
Class _^JL 

Book 'f~'/ 



Z 



(7?¥ 



n siht 



Electrical Engineer's 
pocket-book: 



A BAND-BOOK 

OF USEFUL DATA FOR ELECTRICIANS AND 

ELECTRICAL ENGINEERS. 

BY | 

HORATIO A. FOSTER, 

Fellow A. I. E. E.; Mem. A. S. M. E. Consulting Engineer. 

Author of 

" Engineering Valuation of Public Utilities and Factories." 

With the collaboration of eminent specialists. 



SEVEJVT^f^Qf^p^ HE VISED 

mymm£nTpnm r 

FOR OFFIQA^JJSE C 
ACCOUNTED FOR IN tfKBfcwiTH PAR. 693 A. h. 




NEW YORK: 

D. VAN NO-STRAND COMPANY 

1918. 






Copyrighted, 1902, 1908, 1913, by 

D. VAN NOSTRAND COMPANY, 

New York. 

gj 3IHT 

By Exchange 
Mlddtetown Depot Supply 
March 10,188! 



-4 



r 

PREFACE TO THE FIFTH EDITION. 



^ 

£ 



In appreciation of the very cordial reception accorded 
the earlier editions of this book, and in recognition of 
the fact that vast changes and advances have occurred 
in every branch of electrical engineering since the 
original publication, the author feels called upon to 
issue the present revised and enlarged edition. 

The book as now presented, exceeds the previous 
editions in magnitude by about 600 pages, while the 
subject matter of every section has been either com- 
pletely revised and brought up to date, or entirely 
re-written. The aim throughout has been to supply 
in exhaustive and condensed form, the data essential to 
the engineer engaged in any of the branches of the vast 
domain of electrical engineering. While our concep- 
tion of the fundamental principles of electrical science 
can of necessity have undergone no very considerable 
alteration, those esse&ttal details which in effect con- 
stitute thet ^working -data .Qf the practicing engineer 
have so altered and g^wn : that books published only 
a few years ago are already obsolete. It is believed 
that a stage in the progress of electrical engineering 
standardization has now been reached wherein a com- 
pilation such as the present can be accepted as embody- 
ing the vital element to which future advmces will 
appear to a degree in the relation of superficial alter- 
ations. 

The original plan of dividing the subject into a 
number of sections and having each revised by an 

iii 



iV PREFACE TO THE FIFTH EDITION. 

eminent specialist in that particular field has again 
been followed. Aside from the easy accessibility 
afforded, this plan of construction is valuable only 
in proportion to the weightiness of the authorities 
entrusted with the revision of the several divisions, 
and it is confidently believed that a perusal of the 
names heading the sections will lead to the conviction 
that a more approved and authoritative organization 
could not have been wished for. The several con- 
tributors are widely known and recognized as among 
the first of their respective specialties, and it is be- 
lieved that the general average of excellence assured 
by their collaboration surpasses that of any compila- 
tion of the kind previously attempted. 

Each section is complete in itself, but needless 
repetition has been avoided by the free use of cross 
references through the medium of the very extensive 
index. 

Attention is directed to the large quantity of new 
matter, appearing for the first time in print, in the 
several sections. In the section on Conductors, e.g., 
the tables of Inductance, Capacity and Impedance, will 
be found new and original. Many sections, e.g., 
Street Railways, Photometry, Conductors, Lighting, 
Roentgen Rays, etc., are pointed out as examples 
of exhaustive though condensed presentation. The 
mechanical section has been treated with the same care 
and attention as the electrical. 

The matter has been confined to the requirements 
of the electrical trades and sciences, the inclusion of 
the usual mathematical tables and data found in the 
commonly used handbooks having been avoided. 
These tables being easily accessible, and the present 



PREFACE TO THE FIFTH EDITION. V 

edition being already of great magnitude, this exclu- 
sion will be appreciated. 

An important feature of the present volume will be 
found in the voluminous and studiously developed 
index and table of contents. The index is as com- 
plete as the limitations of manipulative facility will 
permit, and is calculated to render the finding of the 
particular phase of the subject sought a matter of 
least possible labor. The table of contents is designed 
to supplement and extend the use of the index, and in 
conjunction with the marginal thumb-index will render 
instantaneous the location of sections and subdivisions. 

The careful and lengthy work of revision and search 
leads the author to believe that the number of errors 
cannot be large, and he ventures to express the hope 
that readers discovering any will have the kindness 
to bring them to his attention. 

In conclusion the author begs to express his grati- 
tude to the many contributors for their cooperation, 
and to the publishers for their painstaking effort and 
generosity in making so handsome and substantial a 
volume. 

HORATIO A. FOSTER. 

100 Broadway, New York. 
June 1, 1908. 



PREFACE TO THE SEVENTH EDITION. 



No attempt has been made in this edition to add new 
matter nor to make radical changes in the old, but in 
a few cases substitution has been made, as in the latest 
revision of the Standardization Rules of the Am. Inst. 
E. E., and some changes in the text and cuts in the 
chapter on Switchboards. A number of typographical 
and other errors have been corrected. 



HOEATIO A. FOSTER. 



43 Exchange Place, 
New York, April 1, 1913. 



LIST OF CONTRIBUTORS. 



I 



Section. 



Symbols, Units, Instruments 



Measurements 



Revised by 

( W. N. Goodwin, Jr. 
\ J. Frank Stevens. 

jW. N. Goodwin, Jr. 
I Prof. Samuel Sheldon. 



Magnetic Properties of Iron j Townsend Wolcott. 

Electromagnets <Prof. Samuel Sheldon. 

Properties of Conductors . ^ 

Properties of Conductors [ Harold Pender, Ph.D. 

Carrying A.C. Currents . * 

Dimensions of Conductors 
for Distribution Systems . 

Underground Conduit Construction. 

Standard Symbols .... N.E. Contractors' Assoc. 

Cable Testing . . . . . . Wm. Maver, Jr. 



j Harold Pender, Ph.D. 



Principles and Design of 
Dynamos and Motors 



:} 



Cecil P. Poole. 



Tests of 
Motors 



Dynamos and 



( Cecil P. Poole. 
< E. B. Raymond. 



Alternating Current Ma- ( E. B. Raymond, 
chines < Cecil P. Poole. 



The Static Transformer . . 

Standardization Rules . . . 

Electric Lighting, Incan- 
descent 



Electric Lighting, Arc. 



( W. S. Moody. 
i K. C. Randall. 

A.I.E.E. 

j Dr. C. H. Sharp. 
J. H. Hallberg. 



vii 



Vlll 



LIST OF CONTRIBUTORS 



Illuminating Engineering 



Electric Railways . . 

Electrolysis 

Transmission of Power 
Storage Batteries . . . 

Switchboards . . . . . 



Dr. C, H. Sharp. 

r A. H. Armstrong. 
C. Renshaw. 
N. W. Storer. 
Milton W. Franklin, M.A, 

A. A. Knudson. 
Dr. F. A. C. Perrine. 
Lamar Lyndon. 

(H. W. Young. 

B. P. Rowe. 
E. M. Hewlett. 
M. C. Rypinski. 

Lightning Arresters .... Townsend Wolcott. 

to i *«_ M^x ( H. W. Young. 

Electricity Meters ..... | william Br adshaw. 

Telegraphy Chas. Thorn. 

Wireless Telegraphy ... F. K. Vreeland. 

Telephony J. Lloyd Wayne, 3d. 

Electricity in the U. S. Army Grahame H. Powell. 

Electricity in the U. S. Navy J. J. Crain. 

Resonance Lamar Lyndon. 

Electric Automobiles . . . Alexander Churchward. 

Electrochemistry and Elec- ( Prof. F. B. Crocker, 
trometallurgy .... I Prof. M. Arendt. 

X-Rays Edward Lyndon. 

^^w^"^ C ° 0kinS j Max Loewenthal, E.E. 
and Welding ' 

Lightning Conductors . . . Prof. Alex. G. McAdie. 
Mechanical Section _ . j W- Wallace Christie . 

Index Max Loewenthal, E.E. 



SECTIONS. 



Page 

SYMBOLS, UNITS, INSTRUMENTS 1 

MEASUREMENTS 55 

MAGNETIC PROPERTIES OF IRON 89 

ELECTROMAGNETS 108 

PROPERTIES OF WIRES AND CABLES 131 

PROPERTIES OF CONDUCTORS CARRYING A.C. CURRENT 236 

DIMENSIONS OF CONDUCTORS FOR DISTRIBUTION SYSTEMS 260 

STANDARD SYMBOLS FOR WIRING PLANS, N. E. C. A. . 299 

UNDERGROUND CONDUITS AND CONSTRUCTION .... 301 

CABLE TESTING 321 

DIRECT-CURRENT DYNAMOS AND MOTORS 334 

TESTS OF DYNAMOS AND MOTORS 378 

ALTERNATING-CURRENT MACHINES 404 

STATIC TRANSFORMER 443 

STANDARDIZATION RULES A. I. E. E 501 

ELECTRIC LIGHTING 528 

ILLUMINATING ENGINEERING 584 

ELECTRIC RAILWAYS 612 

DETERIORATION OF METALS BY ELECTROLYSIS ... 852 

TRANSMISSION OF POWER . 864 

STORAGE BATTERIES 872 

SWITCHBOARDS 906 

LIGHTNING ARRESTERS ... 980 

ELECTRICITY METERS 997 

TELEGRAPHY 1040 

WIRELESS TELEGRAPHY 1055 

TELEPHONY 1069 

USE OF ELECTRICITY IN U. S. ARMY . . c 1123 

ELECTRICITY IN U. S. NAVY 1153 

RESONANCE 1215 

ELECTRIC AUTOMOBILE 1224 

ELECTROCHEMISTRY AND ELECTRO-METALLURGY . . . 1229 

X-RAYS 1248 

ELECTRIC HEATING, COOKING, AND WELDING .... 1256 

LIGHTNING CONDUCTORS 1277 

FOUNDATIONS AND STRUCTURAL MATERIALS 1289 

STEAM 1327 

WATER-POWER 1460 

SHAFTING, PULLEYS, BELTING, ROPE-DRIVING .... 1481 

MISCELLANEOUS TABLES 1499 

POWER REQUIRED TO DRIVE MACHINERY 1515 

INDEX . . i 5 33 

ix 



( 



TABLE OF CONTENTS. 



ELECTRICAL SECTION. 

SYMBOLS, UNITS, INSTRUMENTS. 

Page 

Electrical Engineering Symbols 1 

Electrical Engineering Units 2 

Symbols for Physical Quantities (Table) 6 

International Electrical Units and Measurements 10 

Equivalent Units, Energy and Work (Table) 12 

Closed Circuit Cells 14 

Open Circuit Cells 15 

Dry Batteries , , 18 

Standard Cells 19 

Grouping of Battery Cells . . . = 19 

Galvanometers 21 

Resistance Standards 30 

Wheatstone Bridge , 31 

Water Rheostats . . . 33 

Galvanized Iron Wire, Properties of 34 

Condensers 35 

Specific Inductive Capacity of Gases (Table) 35 

Specific Inductive Capacity of Solids (Table) 36 

Specific Inductive Capacity of Liquids (Table) . 37 

Specific Inductive Capacity 38 

Electrometers 40 

Voltmeters 40 

Ammeters 41 

Electro-Dynamometers , 42 

Wattmeters 42 

Kelvin's Composite Electric Balance 43 

Potentiometer . . . , . 47 

Instruments and Methods of Determining Wave Forms 50 

Oscillograph 52 

MEASUREMENTS. 

Elementary Laws of Electrical Circuits ............. 55 

Resistance Measurements 56 

Resistance of Galvanometers 60 

Resistance of Batteries . 60 

Resistance of Aerial Lines and House Circuits 61 

xi 



Xll TABLE OF CONTENTS. 

Page 

E.M.F. Measurements 62 

Capacity Measurements 63 

Electromagnetic Induction 64 

Coefficient of Self Induction 65 

Measurement of Self Inductance 66 

Measurement of Mutual Inductance 67 

Measurement of Power in A.C. Circuits 69 

Tests with Voltmeter 74 

E.M.F. of Batteries 74 

E.M.F. of Dynamos , 74 

Comparison of E.M.F. of Batteries 76 

Resistance Measurement with Voltmeter 78 

Resistance Measurement with Voltmeter and Ammeter 78 

Measurement of Very Small Resistances 79 

Measurement of Insulation Resistances 80 

Measurement of Insulation Resistance of Dynamos . . 86 

Measurement of Insulation Resistance of Motors 87 

Measurement of Resistance of Batteries 87 



MAGNETIC PROPERTIES OF IRON. 

Data for (£-3C Curves (Table) 89 

Permeability at High Flux Densities (Table) 91 

Methods of Determining Magnetic Qualities of Steel and Iron ... 91 

Permeameters 94 

Core Losses , 98 

Hysteretic Constants for Different Materials (Table) 99 

Hysteresis Loss Factors (Table) 99 

Hysteresis Factors for Different Core Densities (Table) 100 

Hysteresis Tests 101 

Hysteresis Meter 102 

Eddy Current Factors for Different Core Densities (Table) 106 

Specific Energy Dissipation in Armature Core 107 



ELECTROMAGNETS. 

Principle of Magnetic Circuit 109 

Traction 110 

Magnetization and Traction of Electromagnets (Table) Ill 

Winding of Electromagnets 112 

Resistance of Magnet Wire at 140° F. (Table) 112 

Relation between Wire Length, Size and Turns per Volt (Table). . . 114 

Correcting Length of Magnet Coil (Table) 117 

Linear Space Occupied by Single Cotton-Covered Wire (Table) . . . 121 

Linear Space Occupied by Double Cotton-Covered Wire (Table) . . 123 

Alternating Current Electromagnets 127 

Heating of Magnet Coils 127 

Law of Plunger Electromagnet 127 

Pull and Ampere-Turn Factors (Table) 128 



TABLE OF CONTENTS. Xlll 

PROPERTIES OF WIRES AND CABLES. 

Page 

Units of Resistance 131 

Specific Resistance, Relative Resistance and Relative Conductivity 132 

Temperature Coefficient (Table) 133 

Physical and Electrical Properties of Various Metals and Alloys (Table) 134 

Wire Gauges (Table) 141 

Wire Strands 142 

Physical Constants of Copper Wire (Table) 143 

Effect of Admixture of Copper with Various Substances (Table) . 144 

Copper Wire Tables . . . . . . 145 

Tensile Strength of Copper Wire (Table) . . 156 

Weight of Copper Wire (Table) . . . . . 157 

Underwriters' Test of Rubber Covered Wires 161 

Standard Rubber Covered Wire Cables 161 

Standard Conductor, National Electric Code, G. E. (Table) ... 162 

Special Cables for Car Wiring (Table) . . . . , . 173 

Navy Standard Wires (Table) .*.... 174 

Paper Insulated Cables (Table) ......... . 174 

Cambric Insulated Cables (Table) 178a 

Enameled Wire (Table) 187b 

Telephone Cables (Table) 188 

Telegraph and Submarine Cables (Table) 189 

Joints in Rubber Insulated Cables . . . . . . . 190 

Jointing Gutta-Percha Covered Wire . . . . 193 

Aluminum Wire (Table) . 194 

Aluminum and Copper Compared (Table) 195 

Comparative Cost of Aluminum and Copper for Equal Cond. (Table) 195 
Comparison of Aluminum and Copper for Equal Length and Con- 
ductivity (Table) 195 

Resistance of Solid Aluminum Wire 62% Conductivity (Table) . . 195 

Stranded Weatherproof Aluminum Wire (Table) . 197 

Dimensions and Resistance of Stranded Aluminum Wire (Table) . 198 

Aluminum for High Tension Transmission Lines 199 

Iron and Steel Wire, Physical Constants (Table) . 199 

Double Galvanized Telegraph and Telephone Wires (Table) . . . 200 

Galvanized Signal Strand. Seven Wires (Table) . . . . . . . . 200 

Properties of Steel Wire (Table) 201 

Resistance Wires, Spec. Res. and Temp. Coeff. (Table) . . . . . 202 

German Silver . . 202 

Resistances of German Silver Wire (Table) . . 203 

Manganin 203 

Electrical Properties and Constitution of Manganin (Table) . . . 204 

Dimensions, Resistance and Weights of Resistance Wires (Table) . 204 

Resistance Ribbon, la la, Quality 205 

Krupp's Resistance Wires (Table) 206 

Resistances of Driver-Harris Resistance Wires (Table) . . . . . . 207 

Current Carrying Capacity of Wires and Cables 208 

Carrying Capacity of Wires for Interior Wiring (Tables) 209 



XIV TABLE OF CONTENTS. 

Page 

Carrying Capacity of Rubber Insulated Cables (Table) 210 

Heating of Cables in Multiple Duct Conduit 210 

Watts Lost in Single-Conductor Cables (Table) 212 

Current Carrying Capacity of Lead-Covered Cables 213 

Fusing Effects of Electric Currents 217 

Tension and Sag in Wire Spans 218 

Calculation of Vertical Sag , . 222 

Properties of Dielectrics 227 

Dielectric Strength of Rubber 229 

Dielectric Strength of Gutta-Percha 232 

Dielectric Strength of Air 233 

Puncturing Voltage of Mica (Table) 234 

Minimum Size of Conductors for High Tension Transmission . . . 235 

PROPERTIES OF CONDUCTORS CARRYING ALTERNATING CURRENTS. 

Skin Effect Factors at 20° F. (Table) 237 

Self Induction and Inductive Reactance of Circuits 238 

Self Induction of Iron Wire 240 

Self Induction of Solid Non-Magnetic Wire (Table) 241 

Inductive Reactance of Solid Non-Magnetic Wire (Table) .... 242 

Inductive Reactance of Loop of Three-Phase Line (Table) .... 245 

Inductive Reactance of Solid Iron Wire (Table) 248 

Capacity, Capacity Reactance and Charging Current of Transmission 

Circuits formed by Parallel Wires 248 

Capacity of Transmission Circuits formed by Parallel Wires (Tables) 252 

Simple Alternating Current Circuits, Definitions 259 

DIMENSIONS OF CONDUCTORS FOR DISTRIBUTION SYSTEMS. 

Kelvin's Law 261 

Calculation of Transmission Lines 264 

Effect of Line Capacity 264 

Formulae for Cross Section, Weight and Power Loss (Table) . . . 265 

Cross Section, Resistance and Reactance Factors (Table) .... 266 

Capacity Susceptance of Two Parallel Wires (Table) 269 

Numerical Examples of Calculations of Wiring Systems 271 

Transmission Line of Known Constants 274 

Transmission Line Formulae (Table) 275 

Parallel Distribution 277 

Calculation of Cross Section, Weight, etc., of Lines 277 

Chart and Table for Calculation of Alternating Current Lines . . . 279 
Determination of Size of Conductors for Parallel Distribution of 

Direct Current 284 

Transposition of Lines 285 

Loss in Sheath of Three-Conductor Lead-Covered Cables 293 

Bell Wiring 293 

Gas Light Wiring 295 

Wiring for Generators, Motors, Transformers, etc 295 

Wiring for Induction Motors . 296 

Connections of Transformers for Wiring . . 297 



TABLE OF CONTENTS. XV 

STANDARD SYMBOLS FOR WIRING PLANS AS ADOPTED BY THE 
NATIONAL ELECTRICAL CONTRACTORS' ASSOCIATION. 

UNDERGROUND CONDUITS AND CONSTRUCTION. 

Page 

Cost of Manholes in Dollars (Table) . . 302 

Cost of Sewer Connections in Dollars (Table) 303 

Constant Cost per Conduit Foot for Manholes in Dollars 304 

Cost of Paving per Square Yard in Dol-ars (Table) ........ 305 

Cost of Street Excavation per Conduit Foot (Table) 306 

Constant Cost per Conduit Foot in Dollars (Table) 306 

Cost of Duct Material in Place (Table) . 307 

Cost per Conduit Foot in Cities (Table) 307 

Underground Work at New Orleans (Table) 308 

Boston Edison Co. Construction 309 

Itemized Cost of Conduit (Table) 316 

Estimating Cost of Conduit (Table; 317 

Estimating Cost of Manholes (Table) 317 

Grouping of Ducts in Manholes 318 

Underground Cables 319 

Cable Heads 320 

CABLE TESTING. 

Insulation Resistance Tests 321 

Testing Joints of Cables 323 

Capacity Tests of Cables 324 

Locating Breaks by Capacity Tests 327 

Locating Crosses in Cables 327 

Locating Faults in Cables 328 

Copper Resistance or Conductivity of Cables 330 

Testing Submarine Cables During Manufacture and Laying 331 

Locating Faults in Underground Cables 331 

High Voltage or Dielectric Tests of Cables 332 

DIRECT-CURRENT DYNAMOS AND MOTORS. 

Notation 334 

Fundamentals 336 

External Characteristics 337 

Magnetic Distribution 340 

Armatures 341 

Armature Windings , . . 342 

Balancing the Magnetic Circuits in Dynamos 349 

Heating of Armatures 349 

Armature Reactions 350 

Commutators and Brushes 351 

Field Magnets 352 

Cooling Surfaces of Field Magnets (Table) 352 

Gyrostatic Action on Dynamos in Ships 352 

Direct-Current Motors 353 

Leonard's System of Motor Control 354 



( 



XVI TABLE OF CONTENTS. 

Page 

Three-Wire System for Variable Speed Motor Work ........ 354 

Practical Dynamo Design 355 

Armature Details 356 

Armature Losses 358 

Commutator and Brushes 361 

Air Gap and Pole Face 363 

Field Magnets 364 

Dynamo Efficiency 370 

Armature Slot Sizes for Arrangement of Standard Wires (Table) . . 372 

Trial Armature Coil Slot Depths (Table) 373 

Trial Values for Minimum of Armature Coils (Table) 373 

Trial Values for Maximum Turns per Coil (Table) 374 

Trial Values for Current-Carrying Capacity of Armature Conductors 

(Table) 375 

Barrel Armature Winding Constants (Table) 376 

Average Magnetic Leakage Coefficients (Table) 376 

Average Dynamo Efficiencies (Table) 377 

TESTS OF DYNAMOS AND MOTORS. 

Temperature Tests 378 

Overload Tests 381 

Insulation Tests . ■ 381 

Strain Tests , 381 

Regulation Tests of Dynamos, Shunt or Compound, and Alternators . 382 

Regulation Tests of Motors, Shunt, Compound and Induction .... 383 

Efficiency Tests of Dynamos 383 

Core Loss Test and Test for Friction and Windage 383 

Brush Friction Test 384 

Separation of Core Loss into Hysteresis and Eddy Current Loss . . . 385 

Kapp's Test with Two Similar Direct-Current Dynamos 387 

Electric Method of Supplying the Losses at Constant Potential . . . 389 

Calculation of Efficiencies 391 

Hopkinson's Test of Two Similar Direct-Current Dynamos 393 

Fleming's Modification of Hopkinson's Test . 394 

Motor Tests 394 

Test of Street Railway Motors 397 

Tests for Faults in Armatures . , . , . 402 

ALTERNATING-CURRENT MACHINES. 

Energy in an Entirely Non-inductive and Balanced Three-Phase Cir- 
cuit 405 

Energy in Non-inductive Three-Phase Circuits 406 

Copper Loss in Armatures of Alternators 407 

Compensated Revolving Field Alternators .■"■■. 409 

Regulators for Alternating Current Generators 409 

Alternating Current Armature Windings 410 

Armature Reaction of an Alternator 414 

Synchronizers 416 

Inductor Type Synchroscope . 417 

Note on the Parallel Running of Alternators »,•-•'•• 419 



TABLE OF CONTENTS. XV11 

Page 

Synchronizing .......... 421 

Alternating Current Motors 421 

Elementary Theory of the Polyphase Induction Motor 422 

Analytical Theory of Polyphase Induction Motor . 423 

Speed of Rotary Field for Different Numbers of Poles and for Various 

Frequencies (Table) . 424 

Slip of Induction Motors (Table) 425 

Core of Stator and Rotor 425 

Number of Slots in Field-Frame of Induction Motors (Table) .... 426 

Rotor Slots for Squirrel Cage Induction Motors (Table) 427 

Flux Densities for Induction Motors (Table) 427 

Rotor Windings 429 

Synchronous Motors . . . . . . 430 

Theory of Synchronous Motor 432 

Dynamotors 434 

Direct-Current Boosters 435 

Rotary Converters 436 

Value of Alternating Current Voltage and Current in Terms of 

Direct Current (Table) 438 

Converter Armature Windings 441 

Connection of Transformers and Rotary Converters 442 

Current Densities of Various Materials 442 

THE STATIC TRANSFORMER. 

Cores of American Transformers 443 

Transformer Equations 446 

Features of Design ..... . 447 

Insulation 447 

Temperature 447 

Efficiencies 453 

Magnetic Fatigue or Aging of Steel and Iron 455 

Change of Hysteresis by Prolonged Heating (Table) 457 

Regulation 458 

Comparative Expense of Operating Large and Small Transformers . 458 

Power Factor 458 

Testing Transformer 459 

Sparking Distances Across Needle Points 462 

Transformer for Constant Secondary Current 462 

Economy Coils or Compensators 463 

Transformers for Constant Current from Constant Potential .... 464 

General Electric Constant Current Transformers 464 

Reactance for Alternating Current Arc Circuits 466 

Potential Regulators 467 

Separate Circuit Regulators 469 

Three-Phase Regulators 469 

Three-Phase Transformers , 470 

Ratio of Transformation in Three-Phase Systems 471 

Transformer Connections 472 

Single-Phase Transformer Connection" , , 472 



( 



XV111 TABLE OF CONTENTS. 

Page 

Two-Phase Transformer Connections 473 

Three-Phase Transformer Connections 473 

Arrangement of Transformers for Stepping Up and Down for Long 

Distance Transmission 475 

Three-Phase to Six-Phase Connections 475 

Methods of Connecting Transformers to Rotary Converters 476 

Converter and Transformer Connections 477 

Measuring Power in Six-Phase Circuits .............. 477 

Y or A Connection in Transformers 478 

Grounding the Neutral 478 

Unstable Neutral 479 

Rise of Potential 479 

General Electric Company Mercury Arc Rectifiers 480 

Westinghouse Mercury Arc Rectifier Outfits 481 

Transformer Testing 482 

Insulation Test 483 

Core Loss and Exciting Current 485 

Measurement of Resistance 486 

Impedance and Copper-Loss Tests 487 

Heat Tests 489 

Regulation 491 

Efficiency 493 

Polarity 495 

Data to be Determined by Tests 495 

Methods of Testing Transformers 496 

Specifications for Transformers 498 

Rise of Temperature 498 

Location of Transformers 499 

Transformer Oil 500 

STANDARDIZATION RULES OF THE AMERICAN INSTITUTE 
OF ELECTRICAL ENGINEERS. 

Definitions and Technical Data 501 

Performance, Specifications and Tests 506 

Voltages and Frequencies 521 

General Recommendations 522 

Appendices and Tabular Data 523 

ELECTRIC LIGHTING. 

Light and Laws of Radiation 528 

Intrinsic Brightness of Different Sources of Light (Table) 529 

Units and Standards of Light 530 

Photometers 534 

Incandescent Lamps 540 

Distribution Curves 540 

Current Taken by Various Lamps (Table) 542 

Proper Use of Incandescent Lamps 544 

Life and Candle Power of Lamps 644 

Importance of Good Regulation , 545 



TABLE OF CONTENTS. xix 



Candle-Hours — Regulation of Lamp Values 546 

Variation in Candle-Power and Efficiency 547 

Lamp Renewals 547 

Luminosity of Incandescent Lamps 548 

Metallized Carbon or Gem Lamps 549 

Tantalum Lamps 549 

Tungsten Lamps 553 

Effect of Changes of Voltage 553 

When and How Incandescent Lamps are Used (Table) 555 

Totals of Average Consumption, Showing Yearly Consumption per 

16-c.p. Lamp Connected (Table) 555 

Cooper-Hewitt Mercury Vapor Lamp 558 

Nernst Lamp 562 

Tests of Various Illuminants by National Electric Light Assn. . . . 564 

Moore Vacuum Tube Light 565 

Efficiency of Moore Tube 566 

Arc Lamps and Arc Lighting . . 568 

Classification of Arc Lights 568 

Open Arc Lamps 569 

High Tension Lamp 570 

Magnetite Arc Lamp 570 

Flaming Arc Lamps 572 

Searchlight Projectors 575 

Enclosed Arc Lamps . . . . 575 

Tests of Arc Light Carbons 577 

Enclosed Arc Carbons 578 

Sizes of Carbons for Arc Lamps (Table) 578 

Carbons for Searchlight Projectors (Table) 579 

Carbons for Focusing Lamps (Table) 579 

Candle Power of Arc Lamps 579 

Arc Light Efficiency 580 

Heat and Temperature Developed by the Electric Arc 581 

Balancing Resistance for Arc Lamps on Constant Potential Circuit . 581 

Street Lighting by Arc. Lamps 582 

Light Cut Off by Globes 582 

Trimming Arc Lamps 583 

ILLUMINATING ENGINEERING. 

Intensity of Illumination at Various Points (Table) 586 

Graphic Illuminating Chart 587 

Required Illumination for Various Classes of Service (Table) .... 589 

Saving by the Use of High-Efficiency Lamps (Table) 589 

Experimental Data on Illumination Values 592 

Coefficients of Reflection 593 

Comparative Values of Illumination and Efficiency of Various Methods 

of Lighting (Table) 594 

Interior Illumination 596 

Data on Arc Lighting Installations in Operation (Table) 598 

General Illumination ... 599 



i 



XX TABLE OF CONTENTS. 

Correct Use of Light ............ 600 

Distribution of Light by Incandescent Lamps 601 

Concealed Lighting Systems 601 

Illumination Intensity Required for Reading ...... . ... . 602 

Lighting Schedules 603 

Lighting Table for New York City 604 

Hours Artificial Light Needed Each Month (Table) 606 

Humphreys' Lighting Tables 607 

Hours of Burning Commercial Lights (Table) . . . . 611 

Graphic Lighting Schedule for London, England ......... 611 

ELECTRIC RAILWAYS. 

Grades and Curves . ■•••...,.• 612 

Systems of Operation 613 

Car Equipments . . . . 613 

Locomotives 614 

Weights of Rails (Table) 615 

Radius of Curves for Different Degrees of Curvature (Table) .... 617 

Grades in per Cent, and Rise in Feet (Table) 617 

Elevation of Outer Rail on Curves (Table) 617 

Equipment Tables 618 

Durability of Railroad Ties (Table) 619 

Paving 619 

Estimate of Track Laying Force . 619 

Railway Turnout 620 

Electric Railway Automatic Block Signalling 622 

Requirements of a Signal System 623 

Typical Automatic Two-Line Wire, Non-Interfering Block Signal . . 624 

Distributed Signal Block System 627 

Material for One Mile Overhead Line Street Railway (Table) .... 628 
Estimated Cost of One Mile Double Track Overhead Street Rail- 
way System 629 

Standard Iron or Steel Tubular Poles 629 

Standard Pole Line Construction 630 

Double Track Center Pole Construction 631 

Plate Box Poles 632 

Tubular Iron or Steel Poles (Table) 633 

Cubic Contents of Wooden Poles (Table) 633 

Average Weights of Various Woods (Table) 634 

Dip in Span Wire 634 

Side Brackets 635 

Trolley Wire Suspension 637 

Guard Wires 639 

Catenary Trolley Construction for A.C. Railways 640 

Properties of Galvanized Steel Strand Cable (Table) 642 

Line Material per Mile of Tangent Track for Catenary Construction 

(Table) 643 

Staggering Trolley for Sliding Contact 644 

Bracket Construction 644 



TABLE OF CONTENTS. XXI 

Page 

Span Construction 644 

Hangers per Span for Tangent Track (Table) 646 

Hangers per Span for Pull-Off Curve Construction (Table) 647 

Energy Consumption 652 

Constants for Determining H.P. of Traction (Table) ....... 653 

Horse Power of Traction (Table) 654 

Traction (Table) 655 

Revolution of Wheels for Various Speeds (Table) 655 

Power for Double and Single Truck Cars (Table) 656 

Tractive Effort on Grades (Table) 657 

Kilowatts on Grades (Table) 657 

Power Consumption, 25 M.P.H., 35-Ton Car (Table) 658 

Number of Cars on Ten Miles of Track, Various Speeds and Head- 
ways (Table) 658 

Effect of Shape of Moving Body on Air Resistance (Curves) .... 659 

Headway, Speed and Total Number of Cars 660 

Miles per Hour in Feet per Second and Minute (Table) 660 

Rating Street Railway Motors 661 

Tractive Effort 661 

Tractive Coefficient 662 

Train Performance Diagrams 663 

Acceleration 664 

Construction of Speed-Time Curve 666 

Data for Distance-Time Curve (Table) 669 

Data for Speed -Time Curve (Table) 671 

Rating Railway Motors from Performance Curves 673 

Motor Capacity Curve 676 

Graphical Approximation of Energy for Electric Cars 679 

Train Friction Curves 679 

Speed and Energy Curves 680 

Motor Characteristic Curves 685 

Determination of Energy 706 

Single-Phase A.C. Railway Motors 707 

G. E. Co.'s Hand Potential Control System 710 

Single-Phase Motor Characteristics 713 

Weights of A.C. Motor Equipments 719 

Comparative Weights 75 H.P. 4-Motor Equipments 719 

High Speed Trials on Lake Electric Railway 719 

Interurban Car Tests 722 

Train Log (Tables) 723 

Comparison of Car Tests (Table) 724 

Personal Factor of Motormen, Local Runs (Tables) 724 

Tests of Interurban Cars, Northern Texas Traction Co. (Table) . . . 725 

Two Motors vs. Four Motors per Car (Table) 729 

Railway Motors, Standard Sizes and Ratings (Table) 729 

Weights of Equipment, Control Apparatus, Car Wiring and Motors 

(Table) 730 

Torque and Horse Power (Table) 731 

Emergency Braking of Cars 731 



< 



XX11 TABLE OF CONTENTS. 

Page 

Copper Wire Fuses for Railway Circuits (Table) 731 

Approximate Dimensions of Electric Cars (Table) 732 

Weight of Car Bodies and Trucks 734 

Dimensions of Brill Cars (Table) 737 

Electric Locomotives 739 

Installation of Electric Car Motors 745 

Preparation of the Car Body 745 

Installing Controllers . . 746 

Wiring .... 746 

Operation and Car? 3. Controller 747 

Diagrams of Cat Wiring 747 

Equipment Lists 752 

Controllers 753 

Series Parallel Controllers . 755 

Electric Brake Controllers 755 

Rheostatic Controllers 756 

Dimensions of Controllers (Table) 757 

Sprague G. E. Multiple Unit Control 761 

Westinghouse Unit Switch Systems of Multiple Control 766 

Approximate Rates of Depreciation on Electric Street Railways . . 770 

Depreciation of Street Railway Machinery and Equipment 770 

Car Heating by Electricity 770 

Track Return Circuit 771 

Type of Bonds 772 

Welded Joints 778 

Resistance of Track Rails (Table) 779 

Relative Value of Rails and Bonded Joints 780 

Ingredients of Rails Under Test (Table) 780 

Board of Trade Regulations for Great Britain 781 

Calculation of the Overhead Conducting System of Electric Rail- 
ways 785 

Continuous Current Feeders Load Determination 786 

Economical Design of Feeders 786 

Limiting Potential Drop 788 

Two Classes of Feeders 788 

Calculation of Dimensions of Conductors 791 

Drop and Loss in Line Between Two Substations of Unequal Poten- 
tial 794 

Impedance of Steel Rails to Alternating Current 795 

Experimental Determination of Impedance of Steel Rails 795 

Experiment on Inter works Track of W'estinghouse E. and M. Co. . . 796 
Comparative A.C. and D.C. Resistance Trolley and Track per Mile 

of Circuit 798 

Tests of Street Railway Circuits 798 

Tests for Drop and Resistance in Overhead Lines and Returns . . . 798 

To Read the (J round Return Drop Directly 799 

To Determine Drop at End of Line 800 

To Determine the Condition of Track Bonding and the Division of 

Return Current 800 



TABLE OF CONTENTS. XX111 

Page 

Testing Rail Bonds 801 

Street Railway Motor Testing 803 

Draw-Bar Pull and Efficiency Test without Removing Motor from 

Car 803 

Testing Drop in Railway Circuits » ....... . 804 

Street Car Faults and Remedies 805 

Wiring Diagrams for Lighting Circuits on Street Cars 806 

Special Methods of Distribution 807 

Three- Wire System 807 

Booster System 807 

Return Feeder Booster 808 

Electric Railway Booster Calculations 809 

Series Boosters for Railway Service 813 

Substation System 814 

Portable Substations 819 

Third Rail Systems 821 

Resistance of Rails with Varying Composition 821 

Electrical and Chemical Qualities of Steel for Third Rail (Table) . . 822 

Wrought or Refined Iron for Third Rail (Table) 824 

Resistance of Steel, Variation with Manganese (Table) 825 

Resistance of Steel, Variation with Carbon (Table) 826 

Resistance of Steel, Influence of Carbon (Table) 826 

Resistance of Steel (Table) 827 

Location of Third Rail 830 

Third Rail Insulators 831 

Third Rail Shoe 832 

New York Central Third Rail 834 

Estimated Cost of One Mile Single Track Protected Third Rail, Approxi- 
mate 835 

Conduit Systems of Electric Railways 835 

Surface Contact or Electro-Magnetic Systems 840 

Westinghouse Surface Contact System 841 

Sectional Rail Construction 846 

General Electric Contact Railway System 847 

DETERIORATION OF UNDERGROUND METALS DUE TO 
ELECTROLYTIC ACTION. 

Destructive Effects 853 

Increase of Current Flow upon Mains Due to Bonding same to Rails 

or to Negative Conductors 856 

Current Movements upon Underground Mains 858 

Electrolytic Effects upon Water Meters 855 

Danger from Fire or Explosions 858 

Electrolysis in Steel Frame Buildings 859 

Current Swapping 859 

Alternating Current Electrolysis 860 

Insulating Joints in Mains 861 

Surface Insulation 862 

Summary 863 



< 



) 



XXiV TABLE OF CONTENTS. 

TRANSMISSION OF POWER, 

Page 

Engineering Features 864 

Relative Efficiencies of Various Transmission Methods (Table) . . . 865 

Special Features of Design Due to Transmission Line Requirements . 866 

Motive Power 867 

Storage Reservoirs 867 

Generators 870 

Transmitting Apparatus 870 

Transformers 871 

Pole Lines 871 

STORAGE BATTERIES. 

Theory and General Characteristics 872 

Voltage 874 

Types of Plates 874 

Capacity 874 

Discharge Rate Curve 875 

Voltage Variation 876 

Electrolyte 877 

Cadmium Test 878 

Polarization 879 

Efficiency 879 

Comparison of Plante* and Pasted Electrodes . . 880 

Charging 880 

Removal from Service 881 

Battery Troubles ". 881 

Testing 882 

Weight of Complete Cell and Component Parts , . . 882 

Dimensions 883 

Rates of Charge and Discharge 883 

Capacity at Various Discharge Rates 883 

Voltage Curves 883 

Internal Virtual Resistance 883 

Variation in Density of Electrolyte 884 

Loss of Charge with Time . 884 

Efficiency at Various Charge and Discharge Rates 884 

Erection of Battery 884 

Uses of Batteries 886 

Methods of Controlling Discharge 889 

End Cells and Switches 890 

Counter E.M.F. Cells 891 

Resistance Control 891 

Shunt, Automatic, Reversible and Non-Reversible Boosters 891 

Comparison of Boosters 897 

Installations 897 

Three-Wire Systems 899 

Battery Capacity 900 

Strength of Dilute Sulphuric Acid of Different Densities (Table) . . 904 



TABLE OF CONTENTS. XXV 

Page 
Conducting Power of Dilute Sulphuric Acid of Different Strengths 

(Table) 905 

Conducting Power of Acid and Saline Solutions . . ' 905 

SWITCHBOARDS. 

Design of Direct-Control Panel Switchboards 906 

Copper Bar Data (Table) 911 

Aluminum Bar Data (Table) 911 

Alternating-Current Switchboard Panels 912 

Equipment of Single-Phase Feeder Panels 916 

Equipment of Three-Phase Feeder Panels 917 

Equipment of Two-Phase Feeder Panels 918 

Equipment of Induction Motor Panels 918 

Equipment of Three-Phase Synchronous Motor Panels 919 

Equipment of Three-Phase Rotary Converter Panels 919 

Equipment of Constant-Current Transformer Panels 922 

Arc Switchboards 922 

Direct-Current Switchboard Panels 924 

Hand-Operated Remote-Control Switchboards . . 928 

Central Station Electrically Operated Switchboards 928 

Circumstances which Indicate the Necessity of Installing Electrically 

Operated Switchboard Apparatus 929 

Hydro-Electric Generating Station Design 930 

Bus-Bar and Bus-Bar Structures 933 

General Arrangement of Switchboard Devices 935 

Isolation of Conductors 936 

Cells for Voltage Transformers 938 

High -Tension Conductors 939 

Controlling and Instrument Switchboard 940 

Substation Switchboard Equipments 942 

Switchboard Instruments and Meters 945 

Method of Figuring Instrument Scales 946 

Brief Guide for Writing Switchboard Specifications 947 

Switching Devices . 948 

Sparking at Switches 948 

Circuit Breakers 949 

Circuit Breaker Design 952 

A.C. Service Circuit Breakers 952 

Capacity of Circuit Breakers for D.C. Generators 955 

Circuit Breaker Adapted for Motor of Given Size (Table) ...... 955 

Signalling Relays 955 

Regulating Relays 956 

Protective Relays 956 

Application of Relays 960 

Lever Switches 963 

Plug Tube Switches 965 

Disconnecting Switches 965 

Switches for High Potential 967 

Westinghouse Oil Circuit Breakers 969 

Oil Circuit Breaker Controller 975 

General Electric Oil Switches 976 



( 



XXVI TABLE OF CONTENTS. 

LIGHTNING ARRESTERS. 

Page 

Lightning Protection 980 

Switching 980 

Cables 981 

Engine or Water Wheel Governor Troubles 981 

Protection Against Abnormally High Potentials on A.C. Circuits . . 981 

Use of Reactive Coils 982 

Use of a Protective Wire 982 

Ground Connections 983 

Lightning Arresters 983 

Lightning Arresters for Direct Current 984 

Lightning Arresters for Alternating Current 987 

Non-Arcing Metal Lightning Arrester 989 

Garton Arrester 990 

S.K.C. Arrester 990 

Static Discharges 992 

Arresters for High Potential Circuits 993 

Low Equivalent A.C. Lightning Arrester 994 

Horn Type 995 

ELECTRICITY METERS. 

Action of Integrating Meters 997 

Direct-Current Commutator Type Meters 997 

Thomson Recording Wattmeters 998 

Westinghouse D.C. Integrating Meters 998 

Duncan Meters 998 

Induction Type Alternating Current Integrating Meters 999 

Wattmeters on Inductive Circuits 1000 

Power Factor Compensation 1002 

Minimizing Effect of Voltage Variation 1002 

Westinghouse Single-Phase Induction Wattmeters 1003 

Westinghouse Polyphase Induction Wattmeters 1003 

Thomson High Torque Single-Phase Induction Wattmeters .... 1005 

Thomson Polyphase Induction Wattmeters 1005 

Sangamo D.C. Integrating Meter 1006 

Elementary Diagram of Sangamo D.C. Meter 1007 

Sangamo A.C. Meter 1008 

Wright Discount Meter , . . . . 1008 

Meter Bearings, Registers and Commutators c . . . 1009 

Prepayment Wattmeter 1010 

Integrating Wattmeter Testing 1013 

Testing Service Meters 1015 

Calibration Data for Westinghouse Integrating Wattmeters (Table) . 1016 

Testing Meters for Accuracy on Inductive Loads 1018 

Method of Testing Service Meter for Inductive Load Accuracy . . . 1019 

Obtaining Inductive Load from Two-Phase Circuits 1019 

Obtaining Inductive Load from Three-Phase Circuits 1020 

Testing Meters 102 



TABLE OF CONTENTS. XXVli 

Page 

Testing Polyphase Meters 1020 

Standards for Testing Polyphase Meters * 1020 

Service Connections of Polyphase Meters 1023 

Practical Methods of Checking Connections of Polyphase Meters . 1026 

Meter Testing Formulae 1028 

Formula for Testing the Shallenberger Ampere-Hour Meter .... 1028 
Testing Formula for Shallenberger and Westinghouse Integrating 

Wattmeters 1028 

Testing Constant of Westinghouse Meters 1029 

Westinghouse Direct-Current Meters 1030 

Table of Testing Constants for G. E. Co.'s Meters 1030 

" D3 " Polyphase Meters 1031 

Formula for Testing Duncan Recording Wattmeters 1031 

Table of Duncan Constants " K " and Watts per Rev. per M. . . . 1031 

Per cent Error Table for Fifths of a Second 1032 

Table Values of Constants for Fort Wayne Single-Phase Meters . . 1033 

Formula for Testing Sangamo Wattmeters 1035 

Tables of Constants for Sangamo Wattmeters 1035 

Graphic Recording Meters 1036 

Bristol Recording Meters 1036 

General Electric Graphic Recording Meters 1037 

Westinghouse Graphic Recording Meters 1037 

Action of Meters 1039 

TELEGRAPHY. 

American or Closed Circuit Method 1040 

European or Open Circuit Method 1040 

Repeaters 1041 

Milliken Repeater 1041 

Ghegan Repeater 1042 

Weiny-Phillips Repeater 1043 

Duplex Telegraphy 1044 

Duplex Loop System 1047 

Half-Atkinson Repeater 1048 

Duplex Repeater 1049 

Stearns Duplex 1050 

Quadruplex 1051 

Telegraph Codes 1052 

WIRELESS TELEGRAPHY. 

Electrical Oscillations 1055 

Electromagnetic Waves 1055 

Antenna 1058 

Coherer 1058 

Syntonic Signalling 1059 

Skin Effect 1061 

Transmitters 1062 

Receivers 1064 

Detectors 1066 

Undamped Oscillations , 106£ 



I 



XXV111 TABLE OF CONTENTS. 

TELEPHONY. 

Page 

Receivers 1070 

Transmitters 1071 

Induction Coil . . . 1074 

Hook Switch : . . . . 1075 

Calling Apparatus 1075 

Series and Bridging Systems 1076 

Polarized Bell 1078 

Construction of Magneto Generator 1076 

Factors Affecting Transmission: Inductance, Capacity, Resistance . 1079 

Earth Currents, Induction, Cross-Talk 1081 

Metallic Circuits 1081 

Open Wire Circuits 1082 

Cables 1082 

Sample Specification for Telephone Cables 1083 

Capacity of Aerial Telephone Cables (Table) 1085 

Capacity of Underground Telephone Cables (Table) 1086 

Sizes of Cables (Table) 1086 

Annual Expenses of Telephone Cables 1087 

Lightning Arresters 1087 

Classification of Telephone Lines 1088 

Central Office 1089 

Requirements of Satisfactory Operation of Switchboard 1089 

Small Switchboards 1089 

Multiple Switchboard 1090 

Busy Test 1091 

Series-Multiple Switchboard . « 1092 

Branch Terminal or Bridging System 1093 

Transfer Systems 1094 

Relative Value of Multiple and Transfer Systems 1094 

One Central Office vs. Several 1094 

Trunking 1095 

Method of Operating Circuit Trunks 1095 

Auxiliary Trunk Signals 1096 

Ring Down or Common Trunks 1096 

Common Battery System , 1096 

Rudimentary Common Battery Circuits 1097 

Lamp Signals 1098 

Circuits of Common Battery Switchboards 1098 

Three- Wire System 1099 

Two- Wire System 1101 

Common Battery Instrument Circuits 1102 

Party Lines 1102 

Selective Systems 1102 

Method of Obtaining Impulse Currents 1103 

Central Office Apparatus Auxiliary 1104 

Automatic Exchange Systems 1105 

Simultaneous Use of Lines 1105 

Limits of Telephonic Transmission 1107 



TABLE OF CONTENTS. XXlX 

Page 

Notes on Cost of Telephone Plant 1108 

Private Lines, Intercommunicating, and House Systems « . . . . 1108 

Common Return Intercommunicating Systems 1114 

Two-Wire Intercommunicating Telephone Systems 1120 

USES OF ELECTRICITY IN THE UNITED STATES ARMY. 

Searchlights 1123 

Data Relative to Searchlights (Table) 1127 

Boulange* Chronograph 1128 

Schultz Chronoscope 1130 

Schmidt Chronograph 1131 

Squire-Crehore Photo-Chronograph 1133 

Manipulation of Coast-Defense Guns 1134 

Electric Fuses 1134 

Defensive Mines 1137 

Fortress Telephones and Telegraphs 1140 

Field Telephones and Telegraphs 1140 

Telautograph 1141 

Wireless Telegraphy 1145 

Electric Ammunition Hoist with Automatic Safety Stop 1147 

Night Sights . • 1148 

Firing Mechanism for Rapid Fire Guns 1149 

ELECTRICITY IN THE UNITED STATES NAVY. 

General Requirements 1154 

Engine 1154 

Typical Results of Tests on Generating Sets (Table) 1159 

Specifications for Turbo-Generator Sets ... 1159 

Turbine 1160 

Generator 1161 

Operation of Generator t 1162 

Steam Piping 1163 

Switchboards 1163 

Double Dynamo Rooms 1166 

Wiring Specifications 1167 

Single Conductor (Table) 1169 

Twin Conductor (Table) 1170 

Methods of Installing Conductors 1170 

Lighting System, Lamp Specifications 1171 

U. S. Navy Standards for 100-120 Volt Lamps (Table) ....... 1176 

U. S. Navy Standards for 200-250 Volt Lamps (Table) 1177 

Valves for Navy Special Lamps (Table) 1178 

Diving Lanterns 1179 

Searchlights 1179 

Signal Lights 1181 

Ardois System 1181 

Truck Lights 1181 

Power System 1183 



I 



XXX TABLE OF CONTENTS. 

Page 

Teste 1184 

Principal Requirements for Controlling Panels 1185 

Turret-Turning Gear 1187 

Ammunition Hoists . . 1191 

Endless Chain Ammunition Hoists 1192 

Boat Cranes 1194 

Deck Winches 1196 

Ventilation Fans 1196 

Water-Tight Doors 1198 

Steering-Gear 1200 

Interior Communication System 1202 

Range Indicators 1204 

Revolution Indicators 1204 

Telephones 1206 

Fire Alarms and Call Bells 1210 

Range Finder 1211 

Speed Recorder 1211 

RESONANCE. 

Formula? for Alternating Current Flow 1217 

THE ELECTRIC AUTOMOBILE. 

Resistance Due to Gravity and Power Required 1224 

Resistance to Traction on Common Roads (Table) 1225 

Tires 1225 

Motors 1227 

Batteries (Tables) 1227 

Rules for Proper Care of Batteries 1228 

ELECTROCHEMISTRY-ELECTROMETALLURGY. 

Electrolysis 1229 

Resistances of Dilute Sulphuric Acid (Table) 1229 

Resistances of Copper Sulphate (Table) "... 1231 

Resistances of Zinc Sulphate (Table) 1231 

Applications of Electrochemistry 1231 

Electrolytic Chemistry 1231 

Electrotyping 1233 

Electroplating 1233 

Electrolytic Refining of Copper 1235 

Production of Aluminum 1239 

Production of Caustic Soda 1239 

Production of Metallic Sodium 1241 

Potassium Chlorate 1242 

Electrothermal Chemistry 1244 

Calcium Carbide 1245 

Manufacture of Graphite 1245 

Electric Smelting 1247 



TABLE OF CONTENTS. XXXI 

X-RAYS. 

Page 

Tubes 1249 

Regenerative Tubes 1251 

Exciting Source 1252 

Interrupters 1253 

Fluoroscopes 1255 

ELECTRIC HEATING, COOKING AND WELDING. 

Various Methods of Utilizing the Heat Generated by the Electric 

Current (Table) 1256 

Equivalent Values of Electrical and Mechanical Units (Table) . . . 1258 

Cost of Electric Cooking 1259 

Cost of Heating Water to Different Temperatures at Various Rates 

for Current (Table) 1259 

Efficiency of Electric Cooking Apparatus 1260 

Comparative Costs of Gas and Electric Cooking 1260 

Comparison between Gas and Electric Rates 1261 

Cost of Operating Electrically Heated Utensils (Table) 1261 

Daily Electric Cooking Record for One Week (Table) 1262 

Electric Irons for Domestic and Industrial Purposes 1263 

Commercial Electric Laundry Equipment 1263 

Electric Heating 1263 

Radiators and Convecters 1263 

Energy Consumption of Electric Heaters 1265 

Comparison between Electric and Coal Heating 1265 

Electric Car Heating 1265 

Industrial Electric Heating 1269 

Electric Heat in Printing Shops 1269 

Soldering and Branding Irons 1270 

Thawing Water Pipes 1271 

Electric Welding and Forging • 1271 

Electric Rail Welding 1273 

Electric Smelting 1274 

Annealing of Armor Plate 1274 

Hydro-Electrothermic Systems 1274 

Fuse Data * 1275 

Tested Fuse Wire (Table) 1275 

Installation of Fuses 1276 

LIGHTNING CONDUCTORS. 

Selection and Installation of Rods 1278 

Chimney Protection 1281 

Tests of Lightning Rods 1282 

Directions for Personal Safety During Thunder Storms 1283 

Economy of Isolated Electric Plants (Tables) 1283 

Data on Isolated Plants (Table) 1285 

Data on Isolated Plants in Residences (Table) 1287 



XXXii TABLE OF CONTENTS. 

MECHANICAL SECTION. 

FOUNDATIONS AND STRUCTURAL MATERIALS. 

Page 

Power Station Construction (Chart) 1289 

Foundations 1290 

Mortars 1293 

Sand and Cement 1294 

Weight of Flat Rolled Iron (Table) 1295 

Weights of Square and Round Bars of Wrought Iron (Table) . . . 1297 

Weight of Plate Iron (Table) 1298 

U. S. Standard Gauge for Sheet and Plate Iron and Steel 1299 

Columns, Pillars and Struts 1300 

Strength of Materials 1301 

Moment of Inertia 1302 

Radius of Gyration 1303 

Elements of Usual Sections (Table) . . 1303 

Cast-iron Columns 1305 

Transverse Strength 1308 

Fundamental Formulae for Flexure of Beams 1308 

General Formulae for Transverse Strength of Beams (Table) .... 1309 

Approximate Greatest Safe Load on Steel Beams (Table) 1310 

Beams of Uniform Strength Throughout Their Length 1312 

Trenton Beams and Channels (Tables) 1313 

Size and Distance between Floor Beams (Table) 1315 

Properties of Timber (Table) 1316 

Tests of American Woods (Table) 1317 

Wooden Beams (Table) 1318 

Southern Pine Data (Tables) 1320 

Masonry 1322 

Brick W T ork (Tables) 1321 

Weight of Round Bolt Copper (Table) 1323 

Weight of Sheet and Bar Brass (Table) 1323 

Composition of Rolled Brass (Table) ... 1323 

Weight of Copper and Brass Wire and Plates (Table) 1324 

Galvanized Iron Wire Rope (Table) 1325 

Transmission or Haulage Rope (Table) 1325 

Iron and Steel Hoisting Rope (Table) 1326 

STEAM. 

Steam Boilers 1327 

Types of Boilers 1327 

Horse Power of Boilers 1327 

Heating Surface of Boilers 1328 

Grate Surface of Boilers 1329 

Efficiency of Boilers 1329 

Strength of Boiler Shells (Table) 1330 

Rules Governing Boiler Inspection . 1332 



TABLE OF CONTENTS. XXX111 

Page 

Boiler Stays and Braces 1333 

Boiler Settings 1334 

Chimneys (Tables) 1338 

Chimney Construction 1339 

Blowers for Forced Draft 1344 

Fans for Induced Draft 1345 

Kinds and Ingredients of Fuels 1346 

Total Heat of Combustion of Fuels 1347 

Temperature of Fire (Table) 1349 

American Woods (Table) 1349 

American Coals (Table) 1350 

Heating Value of Coals 1350 

Anthracite Coal (Table) 1351 

Bituminous Coal (Table) 1351 

Approximate Analysis of Coal (Table) 1352 

Analysis of Coke 1353 

Space Required to Stow a Ton of Coal (Table) 1353 

Weight of Coal (Table) 1354 

Relative Values of Coals and How to Burn Them 1355 

Wood as Fuel 1356 

Liquid Fuels 1356 

Chemical Composition of Petroleum Oils 1357 

Comparative Costs of Oil and Coal (Table) 1358 

Mechanical Stoking 1359 

Water 1360 

Weight of W x ater (Table) 1361 

W^ater for Boiler Feed 1362 

Solubilities of Scale-making Materials 1363 

Purification of Feed Water by Boiling 1365 

Table of Water Analysis 1366 

Feed Pumps 1367 

Pumping Hot Water 1367 

Injectors 1370 

Deliveries for Live Steam Injectors (Table) 1371 

Rate of Flow of Water Through Pipes (Tables) 1373 

Loss of Head Due to Bends 1374 

Feed Water Heaters 1375 

Saving by Heating Feed Water 1376 

Pump Exhaust 1377 

Fuel Economizers 1378 

Steam Separators 1380 

Safety Valves 1382 

Rules for Conducting Boiler Tests 1384 

Determination of Moisture in Steam 1394 

Throttling Calorimeter 1394 

Moisture in Steam (Table) 1396 

Separating Calorimeter 1398 

Quality of Steam Shown by Issuing Jet 1400 

Factors for Evaporation (Table) ,. '. 1400 



i 



XXXIV TABLE OF CONTENTS. 

Properties of Saturated Steam (Table) 1404 

Superheated Steam . . . 1413 

Condensation in Steam Pipes 1415 

Overflow of Steam from Initial to Lower Pressures (Table) . . , . 1416 

Steam Pipes 1417 

Flow of Steam Through Pipes (Table) 1417 

Equation of Steam Pipes (Tables) 1418 

Protection of Steam-Heated Surfaces (Table) 1421 

Relative Value of Steam Pipe Coverings 1422 

Relative Economy of Different Thicknesses of Covering 1424 

Wrought-Iron Welded Steam Gas and Water Pipe (Table) .... 1427 

Lap-Welded Charcoal-Iron Boiler Tubes (Table) 1428 

Collapsing Pressure 1429 

Resistance of Tubes to Collapse 1429 

Table of Dimensions, High- Pressure Cast-Iron Screw Flanges (Table) 1430 

Tensile Strain of Bolts (Table) 1431 

Pipe Bends 1431 

Standard Pipe Flanges (Table) 1433 

Steam Engines 1434 

Digest of Report on Standardization of Engines and Dynamos . . . 1435 

Standardized Dimensions of Direct-Connected Generating Sets (Table) 1438 

Summary of Tests of Steam Engines (Table) 1439 

Horse Power of Steam Engines 1440 

Cylinder Ratios in Compound Engines 1441 

Number of Expansions for Condensing Engines 1441 

Mean Effective Pressure per Pound Initial Pressure (Table) .... 1442 

Condensers and Pumps 1443 

Ejector Condenser Capacities (Table) . 1445 

Air Pumps 1445 

Circulating Pumps 1446 

Cooling Tower Test 1447 

Gas Engines 1448 

Classification 1448 

Comparative Economy 1449 

Value of Coal Gas of Different Candle Powers for Motive Power 

(Table) 1450 

Gas Engine Power Plant 1450 

Gas Engine Pumping Plant 1451 

Steam Turbines 1451 

De Laval Steam Turbine 1452 

Parsons Steam Turbine 1453 

Curtis Steam Turbine 1455 

Steam Table 1458 

WATER POWER. 

Synopsis of Report Required on Water-Power Property 1460 

Mill Power 1462 

Comparison of Columns of Water (Table) 1463 

Yearly Expense per H. P. on Wheel Shaft (Table j 1464 



TABLE OF CONTENTS. XXXV 

Page 

Pressure of Water (Table) 1465 

Riveted Steel Pipes 1466 

Data for Flumes and Ditches 1468 

Wooden Stave Pipe 1468 

Riveted Hydraulic Pipe (Table) 1469 

Theoretical Velocity and Discharge of Water (Tables) 1470 

Flow of Water through an. Orifice 1471 

Measurement of Flow of Water in a Stream 1471 

Theory of Rod Float Gauging 1471 

Miners' Inch Measurements 1473 

Flow of W^ater over Weirs 1473 

Weir Table 1474 

Calculating the Horse Power of Water (Table) 1475 

Water Wheels 1476 

Turbines 1476 

Impulse Water Wheel 1480 

SHAFTING, PULLEYS, BELTING, ROPE-DRIVING. 

Shafting 1481 

Deflection of Shafting 1482 

Horse Power Transmitted by Shafting 1483 

Horse Power Transmitted by Cold-Rolled Iron Shafting 1484 

Hollow Shafts 1485 

Table for Laying out Shafting 1486 

Pulleys 1487 

Belting 1487 

Width of Belt for Different Horse Power 1488 

Horse Power Transmitted by Different Belts (Tables) 1489 

Rope Driving " 1490 

Horse Power of Manila Rope (Table) 1491 

Table of Horse Power of Transmission Rope 1493 

Slip of Ropes and Belts 1493 

Strains Produced by Loads on Inclined Planes (Table) 1494 

Transmission of Power by Wire Ropes (Table) 1495 

Chain (Tables) 1496 

Lubrication 1497 

Painting . . . . 1498 

MISCELLANEOUS TABLES. 

Weights and Measures, English and Metric (Tables) 1499 

Greek Letters 1505 

Angular Velocity 1505 

Friction 1505 

Temperature or Intensity of Heat 1506 

Comparison of Different Thermometers (Table) 1506 

Coefficients of Expansion of Solids (Table) 1508 

Specific Heats of Metals (Table) 1509 

Heat Unit Table 1510 



< 



UXXV1 TABLE OF CONTENTS. 

Page 

Specific Heat of Gases and Vapors (Table) 1511 

Total Heat of Steam 1511 

Mechanical Equivalent of Heat 1511 

Specific Gravity (Table) 1512 

POWER REQUIRED TO DRIVE MACHINERY, SHOPS AND TO DO 
VARIOUS KINDS OF WORK. 

Prony Brake 1515 

Horse Power Formulas 1515 

Power Used by Machine Tools (Table) 1515 

Motor Power for Machine Tools (Tables) 1518 

Horse Power in Machine Shops, Friction, Men Employed (Table) . 1523 

Cotton Machinery (Table) 1524 

Power Required for Printing Machinery (Table) 1525 

Power Required for Sewing Machines 1525 

Power Consumption in Industrial Establishments (Table) ..... 1526 

Power for Electric Cranes • • 1527 

Operating Cost of Electric Elevators • 1528 

Saving by Electric Drive 1529 

List of Tools and Supplies Used for Installing Electric Lights and 

Dynamos 1530 

Material Required for installing Lamps 1531 

Thawing Frozen Water Pipes Electrically 1531 

INDEX 1533 



SYMBOLS, UNITS, INSTRUMENTS. 

• CHAPTER I. 



( 



ELECTRICAL EIVGOEERIIG IYMBOL8. 

The following list of symbols has been compiled from various sources as 
being those most commonly in use in the United States. Little variation 
will be found from similar lists already published except the elimination of 
some that may be considered exclusively foreign. The list has been revised 
by competent authorities and may be considered as representing the best 
usage* 



fundamental. 



*, 


Length, cm. = centimeter ; 




in., or "i^inch, ft. or ' — 




foot. 


M, 


Mass. gr. — mass of 1 




gramme ; kg. = 1 kilo- 




gramme. 


T,t, 


Time. s=. second. 




Derived: geometric. 


S s 


Surface. 


r, ' 


Volume. 


«.0. 


Angle. 



Mechanical, 
v, Velocity. 

in, Momentum, 

to, Angular velocity. 

a, Acceleration. 

g, Acceleration due to gravity 

= 32.2 feet, per second. 
F, /, Force. 
W, Work. 
P, Power. 

5, Dyne, 10 5 = 10 dynes. 

e, Ergs, 

ft. lb., Foot-pound. 
H.p. , h.p. ; H\ Horse-power. 
I.H.P., Indicated horse-power. 
B.H.P., Brake horse-power. 
E. H.P. , Electrical horse-power. 
J, Joules' equivalent. 

Pj Pressure. 

K, Moment of inertia. 

Derived Electrostatic. 

q f Quantity. 

i, Current. 

e, Potential Difference. 

r, Resistance. 

k, Capacity. 

sk t Specific Inductive capacity. 






Derived Magnetic. 

Strength of pole. 
Magnetic moment. 
Intensity of magnetization. 



J , Intensity of magnetization. 

J£, Horizontal intensity of 
earth's magnetism. 

JC, Field intensity. 

*» Magnetic Flux. 

(B, Magnetic flux density :>r 

magnetic induction. 

J£, Magnetizing force. 

^, Magnetomotive force. 

(ft, Keluctance, Magnetic le- 

sistance. 

m, Magnetic permeability. 

K , Magnetic susceptibility. 

v, Reluctivity (specific mag- 

netic resistance). 

Derived electromagnetic. 



D, 



Resistance, Ohm. 
do, megohm. 

Electromotive force, volt. 
Difference of potential, volt. 
Intensity of current, Ampere. 
Quantity of electricity, Am- 
pere-hour ; Coulomb. 
Capacity. Farad. 
Electric Energy, Watt-hour ; 

Joule. 
Electric Power, Watt ; Kilo- 
watt. 
Resistivity (specific resis- 
tance), Ohm-centimeter. 
Conductance, Mho. 
Conductivity (specific con- 
ductivity/ 
Admittance, mho. 
Impedance, ohm. 
Reactance, ohm. 
Susceptance, mho. 
Inductance (coefficient of 

Induction), Henry. 
Ratio of electro-magnetic to 
electrostatic unit of quan- 
tity =■ 3 X 10 10 centimeters 
per second approximately. 
Symbols in general use. 
Diameter. 
Radius. 
Temperature. 

Deflection of galvanometer 
needle. 



SYMBOLS, UNITS, INSTRUMENTS. 



N, n, 



^/, 

G, 

S, 

N, n, 

S, s, 

A.M. 

V.M. 

A.C. 

D.C. 

P.D. 

O.G.S. 

B. &S. 
B.W.G 



Number of anything. 

Circumference -^- diameter : 
3.141592. 

2tt N = 6.2831 X frequency, in 
alternating current. 

Frequency, periodicity, cy- 
cles per second. 

Galvanometer. 

Shunt. 

North pole of a magnet. 

South pole of a magnet. 

Ammeter. 

Voltmeter. 

Alternating current. 

Direct current. 

Potential difference. 

Centimeter, Gramme, Second 
system. 

Brown & Sharpe wire gauge. 
,, Birmingham Wire gauge. 



R.p.m., Revolutions per minute 

C.P. Candlepower. 

— o — Incandescent lamp. 
I 

X Arc lamp. 



HhoR-S- 


, Condenser. 


♦ 


Battery of cells. 


>sC 


Dynamo or motor, d.c. 


s@ 


Dynamo or motor, a.c. 


M 


Converter. 


UaajuJ 

•VWVWVW 


Static transformer. 


Inductive resistance. 
Non-inductive resistance. 



CHAPTER II. 

ELECTRICAL ENGINEERING UNITS. 

Index Notation. 

Electrical units and values oftentimes require the use of large numbers 
of many figures both as whole numbers and in decimals. In order to avoid 
this to a great extent the index method of notation is in universal use in 
connection with all electrical computations. 

In indicating a large number, for example, say, a million, instead of writ- 
ing 1,000,000, it would by the index method be written 10 6 ; and 35,000,000 
would be written 35 X 10 6 . 

A decimal is written with a minus sign before the exponent, or, T £ = .01 
= 10" 2 ; and .00048 is written 48 x 10~ 5 . 

The velocity of light is 30,000,000,000 cms. per sec, and is written 3 x 10 10 . 

In multiplying numbers expressed in this notation the significant figures 
are multiplied, and to their product is annexed 10, with an index equal to 
the sum of the indices of the two numbers. 

In dividing, the significant figures are divided, and 10, with an index equal 
to the difference of the two indices of the numbers is annexed to the divi- 
dend. 

Fundamental Units. 

The phvsical qualities, such as force, velocity, momentum, etc., are ex- 
pressed in terms of length, mass, time, and for electricity the system of 
terms in universal use is that known as the C. G. S. system, 
viz. : The unit of length is the Centimeter. 

The unit of mass is the Gramme. 
The unit of time is the Second. 

Expressed in more familiar units, the Centimeter is equal to .3937 inch in 
length ; the Gramme is equal to 15.432 grains, and represents the mass or 
quantity of a cubic centimeter of water at 4° C, or 39.2° Fah. ; the Second is 
the HS i^Tffs part of a sidereal day, or the „|„„ part of a mean solar day. 

These units are also often called absolute units. 

I>erived Geometric Units. 

The unit of area or surface is the square centimeter. 
The unit of volume is the cubic centimeter. 

Derived IVIechanical Units. 

Velocity is the rate of change of position, and is uniform velocity when 
equal distances are passed over in equal spaces of time ; unit velocity is a 
rate of change of one centimeter per second. 



ELECTRICAL ENGINEERING UNITS. 5 

Angular Velocity is the angular distance about a center passed through in 
one second of time. Unit angular velocity is the velocity of a body moving 
in a circular path, whose radius is unity, and which would traverse a unit 
angle in unit time. Unit angle is 57°, 17', 44.8" approximately ; i.e., an angle 
whose arc equals its radius. 

Momentum is the quantity of motion in a body, and equals the mass times 
the velocity. 

Acceleration is the rate at which velocity changes ; the unit is an accel- 
eration of one centimeter per second per second. The acceleration due to 
gravity is the increment in velocity imparted to falling bodies by gravity, 
and is usually taken as 32.2 feet per second, or 981 centimeters per second. 
This value differs somewhat at different localities. At the North Pole g = 
983.1 ; at the equator g = 978.1 ; and at Greenwich it is 981.1. 

Force acts to change a body's condition of rest or motion. It is that which 
tends to produce, alter, or destroy motion, and is measured by the time rate 
of change of momentum produced. 

The unit of force is that force which, acting for one second on a mass of 
one gramme, gives the mass a velocity of one centimeter per second ; this 
unit is called a dyne. The force of gravity or weight of a mass in dynes may 
be found by multiplying the mass in grammes by the value of g at the par- 
ticular place where the force is exerted. The pull of gravity on one pound 
in the United States may be taken as 445,000 dynes. 

Work is the product of a force into the distance through which it acts. 
The unit is the erg, and equals the work done in pushing a mass through a 
distance of one centimeter against a force of one dyne. As the " weight" 
of one gramme is 1 X 981, or 981 dynes, the work done in raising a weight of 
one gramme through a height of one centimeter against the force of gravity, 
or 981 dynes, equals 1 X 981 = 981 ergs. 

One kilogramme- meter = 100000 x 981 ergs. 

Kinetic energy is the work a body is able to do by reason of its motion. 

Potential energy is the work a body is able to do by reason of its position. 

The unit of energy is the erg. 

Power is the rate of working, and the unit is the watt = W 7 ergs per sec. 
Horse-power is the unit of power in common use and, although a somewhat 
arbitrary unit, it is difficult to compel people to change from it to any other. 
It equals 33,000 lbs. raised one foot high in one minute, or 550 foot-pounds 
per second. 

1 ft.-lb. = 1.356 X 10 7 ergs. 

1 watt = 10 7 ergs per second. 

1 horse-power = 550 x 1.356 X 10 7 ergs = 746 watts. If a current of / am- 

peres flow through P ohms under a pressure of E volts, then — = — -— — 

E 2 

• g represents the horse-power involved. 

The French "force de cheval" =736 watts =542.48 ft. lbs. per sec.= 
.9863 H. P., and 1 H.P. = 1.01389 "force de cheval." 

Heat. The Joule WJ= 10 7 ergs, and is the work done, or heat generated, by 
a watt second, or ampere flowing for a second through a resistance of an ohm. 
If i/ = heat generated in gramme calories, 
i= current in amperes, 
2£ = e.m.f. in volts, 
R=z resistance in ohms, and 
2 = time in seconds, 
then ^=0.24/2^ = 0.24 Elt. gramme calories or therms. 

EH 
Then IEt = I 2 Pt = -- — EQ— Joules. 

or, as 1 horse-power = 550 foot-pounds of work per second, 
Joules = ft%EQ = .7373 E Q f t. lbs. 

If eat Units. 

The British Thermal Unit is the amount of heat required to raise the 
temperature of one pound of water one deg. F. at or near its temp, of max. 
density, 39.1°; = 1 pound-degree-Fah. = 251 .9 French calories. 

The Calorie is the amount of heat required to raise the temperature of a 



4 SYMBOLS, UNITS, INSTRUMENTS. 

mass of 1 gramme of water from 4° C. to 5° C. = 1 gramme-degree-centi- 
grade. 

Water at 4° C. is at its maximum density. 

Joules equivalent, 7, is the amount of energy equal to a heat unit. 

For a B.T.U., or pound-degree-Fali., 7=1.07 X 10 10 ergs., or = 778 foot- 
pounds. 

For one pound-degree — Centigrade, 7= 1.93 x 10 10 ergs. 

For a calorie .7=4.189 X 10 7 ergs. 

The heat generated in t seconds of time is 

£!|? = ^? t whe re 7=4.189 X 10 7 , 
J J 

and 7, R, and E are expressed in practical units. 

Electrical Units. 

There are two sets of electrical units derived from the fundamental 
C. G. S. units; viz., the electrostatic and the electromagnetic. The first is 
based on the force exerted between two quantities of electricity, and the sec- 
ond upon the force exerted between a current and a magnetic pole. The 
ratio of the electrostatic to the electromagnetic units has been carefully de- 
termined by a number of authorities, and is found to be some multiple or 
sub-multiple of a quantity represented by v, whose value is approximately 
3 X 10 10 centimeters per second. Convenient rules for changing from one to 
the other set of units will be stated later on in this chapter. 

Electrostatic Units. 

As yet there have been no names assigned to these. Their values are as 
follows : 

The unit of quantity is that quantity of electricity which repels with a 
force of one dyne a similar and equal quantity of electricity placed at unit 
distance (one centimeter) in air. 

Unit of current is that which conveys a unit of quantity along a conduc- 
tor in unit time (one second). 

Unit difference of potential or unit electro-motive force exists between two 
points when one erg of work is required to pass a unit quantity of electricity 
from one point to the other. 

Unit of resistance is possessed by that conductor through which unit cur- 
rent will pass under unit electro-motive force at its ends. 

Unit of capacity is that which, when charged by unit potential, will hold 
one unit of electricity ; or that capacity which, when charged with one unit 
of electricity, has a unit difference of potential. 

Specific inductive capacity of a substance is the ratio between the capacity 
of a condenser having that substance as a dielectric to the capacity of the 
same condenser using dry air at 0° C. and a pressure of 76 centimeters as 
the dielectric. 

Magnetic Units. 

Unit Strength of Pole (symbol m) is that which repels another similar and 
equal pole with unit force (one dyne) when placed at unit distance (one 
centimeter) from it. 

Magnetic Moment (symbol 9K ) is tne product of the strength of either 
pole into the distance between the two poles. 

Intensity of Magnetization is the magnetic moment of a magnet divided 
by its volume, (symbol Q). 

Intensity of Magnetic Field (symbol J£ ) is measured by the force it exerts 
upon a unit magnetic pole, and therefore the unit is that intensity of field 
which acts on a unit pole with a unit force (one dyne). 

Magnetic Induction (symbol (&) is the magnetic flux or the number of 
magnetic lines per unit area of cross-section of magnetized material, the 
area being at every point perpendicular to the direction of flux. It is equal 
to the magnetizing force or field intensity J£ multiplied by the permeability 
ft: the unit is the gauss. 

Magnetic Flux (symbol $) is equal to the average field intensity multiplied 
by the area. Its unit is the maxwell. 

Magnetizing Force (symbol J£ ) per unit of length of a solenoid equals 



ELECTRICAL ENGINEERING UNITS. 



4 n NI -7- L where 2V= the number of turns of wire on the solenoid ; L = 
the length of the solenoid in cms., and I = the current in absolute units. 

Magnetomotive Force (symbol 9F ) is the total magnetizing force developed 
in a magnetic circuit by a coil, equals 4 n AT, and the unit is the gil- 
bert. 

Reluctance, or Magnetic Resistance (symbol (ft), is the resistance offered to 
the magnetic flux by the material magnetized, and is the ratio of magneto- 
motive force to magnetic flux; that is, unit magnetomotive force will generate 
a unit of magnetic flux through unit reluctance : the unit is the oersted; i.e., 
the reluctance ottered by a cubic centimeter of vacuum. 

Magnetic Permeability (symbol /*) is the ratio of the magnetic induction 

(ft to the magnetizing force J£, that is ^ = ft. 

Magnetic Susceptibility (symbol k) is the ratio of the intensity of mag- 
netization to the magnetizing force, or k = ^ • 

Reluctivity , or Specific Magnetic Resistance (symbol v), is the reluctance 
per unit of length and of unit cross-section that a material offers to being 
magnetized. 

Electromag-netic Units. 

Resistance (symbol R) is that property of a material that opposes the flow 
of a current of electricity through it; and the unit is that resistance which, 
with an electro-motive force or pressure between its ends of one unit, will 
permit the flow of a unit of current. 

The practical unit is the ohm, and its value in C.S.G. units is 10 9 . The 
standard unit is a column of pure mercury at 0° C, of uniform cross-section, 
106.3 centimeters long, and 14.4521 grammes weight. For convenience in use 
for very high resistances the prefix meg is used; and the megohm, or million 
ohms, becomes the unit for use in expressing the insulation resistances of 
submarine cables and all other high resistances. 

Electro-motive Force (symbol E) is the electric pressure which forces the 
current through a resistance, and unit E.M.F. is that pressure which will 
force a unit current one ampere through a unit resistance. The unit is the 
volt, and the practical standard adopted by the international congress of elec- 
tricians at Chicago in 1893 is the Clark cell, directions for making which 
will be given farther on. The E.M.F. of a Clark cell is 1.434 volt at 15° C. 

The value of the volt in C.G.S. units is 10 8 . For small E.M.F's. the unit 
millivolt, or one-thousandth volt, is used. 

The International Volt is 1.1358 B. A. volts; and the ratio of B. A. volt 
to the International volt is .9866. 

Difference of Potential, as the name indicates, is simply a difference of 
electric pressure between two points. The unit is the volt. 

Current (symbol /) is the intensity of the electric current that flows 
through a circuit. A unit current will flow through a resistance of one 
ohm, with an electro-motive force of one volt between its ends. The unit 
is the ampere, and is practically represented by the current that will electro- 
lytically deposit silver at the rate of .001118 gramme per second. Its value 
in C.G.S. units is 10 -1 . For small values the milliampere is used, and it 
equals one-thousandth of an ampere. 

The Quantity of Electricity (symbol Q) which passes through a given cross- 
section of an individual circuit in t seconds when a current of /amperes is 
flowing is equal to It units. The unit is therefore the ampere-second. Its 
name is the Coulomb, and its value in C.G.S. units is 10 -1 . 

Capacity (symbol C) is the property of a material condenser for holding 
a charge of electricity. A condenser of unit capacity is one which will be 
charged to a potential of one volt by a quantity of 1 coulomb. The unit is 
the farad, its C.G.S. value is 10~ 9 ; and this being so much larger than ever 
obtains in practical work, its millionth part, or the micro-farad, is used as 
the practical unit, and its value in absolute units is 10 _ 15 . A condenser of 
one-third micro-farad capacity is the size in most common use in the U. S. 

Electric Energy (symbol W) is represented by the work done in a circuit 
or conductor by a current flowing through it. The unit is the Joule, its 
absolute value is 10 7 ergs, and it reprepresents the work done by the flow 
for one second of unit current (1 ampere) through 1 ohm. 

Electric Power (symbol P) is measured in watts, and is represented by a 
current of 1 ampere under a pressure of 1 volt, or 1 Joule per second. The 



SYMBOLS, UNITS, MEASUREMENTS. 



> do © rx • 

© p Jf .2 5 

,0 .« C p 






;■«§! 

-O P e8 ©P 

<2 flfl 



© QQ 

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QQ ^ 



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p 00 



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bC-, . 



tig 

©*s •► 

2.s 

COM 

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ft 



S/ 



v 
X 



S « S 



o . 


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bfi"£ 
© ®, 










br, © 


p* g 


Am 
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®2 

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p © 




B--* 


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IS 



©-© 
£5 
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bcu. 
o © 
a ©< 

M 



as 
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£ exp 
b^ © 

"1*H © 



B © 

© 00 
Q GO 



X 



©1 

© o 
P © 
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a,© . © 

. © <x> . © 

£ a c bX) * 

<U CD ^ 5p C> 

Sfl M P< 

•~-p bC 



^*< S|8| 



^ 
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fe sis S 



mi it ii it it mi i! 



lS*tf 



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b£ CO © 

c rt a 

<d <~.B 



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t- 1 ^ be ,2 

p o a <D 



B © 



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5*2 



-w © 



i?p co © 

• 5 2 £ a 
- a -a © 

-d * a? © 

35<H -J© 

^ 03 H 

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5I.5.S 

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CO rt ©J 
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02 © CO P 



§^-B 

^ I* § 

S ° )n ■• 
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ca « c fl 
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"5 co 50 • 

ce f-i © p 
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Swa 

^q— ■ socq 
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■p © 

PH © «,- 

© eS^t 



ELECTRICAL ENGINEERING UNITS. 



8 



++*? -2> 



O ee 



C > 



S 
© 
bo 



© 0) 



S3 & 
C so 



a s 

.d O 

O > 

m & 

■s * 



o 



r ^ 



Hn Hn Si 

Si nJ? 

«|N W|N I 

^ S *q 



^ L ^ ^ 51 

-In Nn|n He, H- 

S* -In C S| Hn 
^ Sj ^ ^ Sj 

-4n "^ Hn Hn ^h 

| W|N | I HfN 

^ S ^ ^ ^ 



fc 

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PH Hn 



II II 










ei^^l^ii ^S 



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^ ^ * 6 & & g 



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a,^ £ ^ O & * <S #\*> g * 






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a 3 

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be 



•S « fa 



bo ^ 



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oq 53 



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bD © 00 

S3 S3 S3 
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a EL s 

be bp bo 
c3 e« 



S S fafaS£g« 



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S3 




bD 


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SYMBOLS, UNITS, INSTRUMENTS. 






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£ * 



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s s 

o o 



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AG'S 2 

as w 



^ k 



t & &* ^ 

t, ^ ^ 2, 2, 



^ ^ H ft - t £ 

t, ?, ^ fc v ^ ^ t 



s ° 
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II II II II II II II II II II 
b^0»0^^ <*■ Cb ^ ^ 



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to" s~ c£ o fe ^ 






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q 33 






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3 3 « 3 § £ 

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INTERNATIONAL ELECTRICAL UNITS. 9 

watt equals 10 7 absolute units, and 746 watts equals 1 horse-power. In elec- 
tric lighting and power the unit kilowatt, or 1000 watts, is considerably used 
to avoid the use of large numbers. 

Resistivity (symbol p) is the specific resistance of a substance, and is the 
resistance in ohms of a centimeter cube of the material to a flow of cur- 
rent between opposite faces. 

Conductance (symbol G) is that property of a metal or substance by which 
it conducts an electric current, and equals the reciprocal of its resistance. 
The unit proposed for conductance is the Mho, but it has not come into 
prominent use as yet. 

Conductivity (symbol v) is the specific conductance of a material, and is 
therefore the reciprocal of its resistivity. It is often expressed in compari- 
son with the conductivity of some standard metal such as silver or copper, 
and is then stated as a percentage. 

Inductance (symbol L), or coefficient of self-induction, of a circuit is that 
coefficient by which the time rate of change of the current in the circuit 
must be multiplied in order to give the E.M.F. of self-induction in the 
circuit. The practical unit is the henry, which equals 10 9 absolute units, 
and exists in a circuit when a current varying 1 ampere per second produces 
2l volt of electro-motive force in that circuit. As the henry is so large as to 
be seldom met with in practice, 1 thousandth of it, or the milli-henry , is the 
unit most in use. 

Below will be found a few rules for reducing values stated in electrostatic 
units to units in the electro-magnetic system. To reduce 

electrostatic potential to volts, multiply by 300 ; 

44 capacity to micro-farads, divide by 900,000 ; 

44 quantity to coulombs, divide by 3 x 10 9 ; 

44 current to amperes, divide by 3 X 10 9 ; 

44 resistance to ohms, multiply by 9 x 10 11 . 

¥I¥TEIt]¥AMO]¥AJL EIECIRICAL UMTS. 

At the International Congress of Electricians, held at Chicago, August 21, 
1893, the following resolutions met with unanimous approval, and being 
approved for publication by the Treasury Department of the United States 
Government, Dec. 27, 1893, and legalized by act of Congress and approved 
by the President, July 12, 1894, are now recognized as the International 
units of value for their respective purposes. 

RESOL VED, That the several governments represented by the delegates 
of the International Congress of Electricians be, and they are hereby, 
recommended to formally adopt as legal units of electrical measure ttie 
following : 

1. As a unit of resistance, the International ohm, which is based upon the 
ohm equal to 10 9 units of resistance of the C.G.S. system of electro-magnetic 
units, and is represented by the resistance offered' to an unvarying electric 
current by a column of mercury at a temperature of melting ice, 14.4[»21 
grammes in mass, of a constant cross-sectional area, and of the length 10^.3 
centimeters. 

2. As a unit of current, the International ampere, which is one-tenth of the 
unit of current of the C.G.S. system of electro-magnetic units, and which is 
represented sufficiently well for practical use by the unvarying current 
which, when passed through a solution of nitrate of silver in water, in 
accordance with the accompanying specification (A) deposits silver at t lie 
rate of 0.001118 gramme per second. 

3. As a unit of electro-motive force the international volt which is the 
E.M.F. that, steadily applied to a conductor whose resistance is one Inter- 
national ohm, will produce a current of one international ampere, and 

1000 
which is represented sufficiently well for practical use by — — of the E.M.P. 

between the poles or electrodes of the voltaic cell known as Clark's cell at 
a temperature of 15° C, and prepared in the manner described in the ac- 
companying specification (B). 

4. As the unit of quantity, the International coulomb, which is the quan- 
tity of electricity transferred by a current of one international ampere in 
one second. 

5. As the unit of capacity the international farad , which is the capacity 



10 SYMBOLS, UNITS, INSTRUMENTS. 

of a conductor charged to a potential of one international volt by one inter- 
national coulomb of electricity. 

6. As the unit of work, the joule, which is 10 7 units of work in the C.G.S. 
system, and which is represented sufficiently well for practical use by the 
energy expended in one second by an international ampere in an inter- 
national ohm. 

7. As the unit of power, the watt, which is equal to 10 7 units of power in the 
C.G.S. system, and which is represented sufficiently well for practical use 
by'the work done at the rate of one joule per second. 

8. As the unit of induction, the henry, which is the induction in the cir- 
cuit when the E.M.F. induced in this circuit is one international volt, while 
the inducing current varies at the rate of one international ampere per 
second. 

Specification A. 

In employing the silver voltameter to measure currents of about one 
ampere, the following arrangements shall be adopted: : 

The kathode on which the silver is to be deposited shall take the form of 
a platinum bowl not less than 10 cms. in diameter, and from 4 to 5 cms. in 
depth. 

The anode shall be a disk or plate of pure silver some 30 sq. cms. in area, 
and 2 or 3 cms. in thickness. 

This shall be supported horizontally in the liquid near the top of the 
solution by a silver rod riveted through its center. 

To prevent the disintegrated silver which is formed on the anode from 
falling upon the kathode, the anode shall be wrapped around with pure 
filter paper, secured at the back by suitable folding. 

The liquid shall consist of a neutral solution of pure silver nitrate, con- 
taining about 15 parts by weight of the nitrate to 85 parts of water. 

The resistance of the voltameter changes somewhat as the current passes. 
To prevent these changes having too great an effect on the current, some 
resistance, besides that of the voltameter, should be inserted in the circuit. 
The total metallic resistance of the circuit should not be less than 10 ohms. 

Method of making* a Measurement. — The platinum bowl is to 
be washed consecutively with nitric acid, distilled water, and absolute 
alcohol ; it is then to be dried at 160° 0., and left to cool in a desiccator. 
When cold it is to be weighed carefully. 

It is to be nearly filled with the solution, and connected to the rest of the 
circuit by being placed on a clean copper support to which a binding-screw 
is attached 

The anode is then to be immersed in the solution so as to be well covered 
by it, and supported in that position ; the connections to the rest of the 
circuit are then to be made. 

Contact is to be made at the key, noting the time. The current is to be 
allowed to pass for not less than half an hour, and the time of breaking 
contact observed. 

The solution is now to be removed from the bowl, and the deposit washed 
with distilled water, and left to soak for at least six hours. It is then to be 
nused successively with distilled water and absolute alcohol, and dried in a 
hot-air bath at a temperature of about 160° C. After cooling in a desiccator 
11 m fc £ J* Y eighed a S am - The S ain in mass gives the silver' deposited. 

To find the time average of the current in amperes, this mass, expressed 
m grammes, must be divided bv the number of seconds during which th< 
current has passed and by 0.001118. 

In determining the constant of an instrument by this method the current 
should be kept as nearly uniform as possible, and the readings of the instru- 
ment observed at frequent intervals of time. These observations give a 
curve from which the reading corresponding to the mean current (time 
average of the current) can be found. 

The current is calculated from the voltameter results, corresponding to 
this reading. * & 

The current used in this experiment must be obtained from a battery and 
not from a dynamo, especially when the instrument to be calibrated is an 
electrodynamometer. 

Specification B. — The Volt. 

The cell has for its positive electrode, mercury, and for its negative elec- 
trode, amalgamated zinc ; the electrolyte consists of a saturated solution of 



SPECIFICATION B. 



11 



tine sulphate and mercurous sulphate. The electromotive force is 1.434 volts 
at 15° C, and, between 10° C. and 25° C, by the increase of 1° C. in tempera- 
ture, the electromotive force decreases by .00115 of a volt. 

1. Preparation of the mercury. — To secure purity it should be 
first treated with acid in the usual manner, and subsequently distilled in 
vacuo. 

2. Preparation of the Zinc Amalgam,- The zinc designated in 
commerce as " commercially pure" can be used without further prepara- 
tion. For the preparation of the amalgam one part by weight of zinc is to 
be added to nine (9) parts by weight of mercury, and both are to be heated 
in a porcelain dish at 100° C. with moderate stirring until the zinc has been 
fully dissolved in the mercury. 

3. Preparation of the Mercurous Sulphate. — Take mercurous 
sulphate, purchased as pure, mix with it a small quantity of pure mercury, 
and wash the whole thoroughly with cold distilled water by agitation in a 
bottle ; drain off the water and repeat the process at least twice. After the 
last washing, drain off as much of the water as possible. (For further de- 
tails of purification, see Note A.) 

4. Preparation of the Zinc Sulphate Solution. — Prepare a 
neutral saturated solution of pure re-crystallized zinc sulphate, free from 
iron, by mixing distilled water with nearly twice its weight of crystals of 
pure zinc sulphate and adding zinc oxide in the proportion of about 2 per 
cent by weight of the zinc sulphate crystals to neutralize any free acid. The 
crystals should be dissolved by the aid of gentle heat, but the temperature 
to which the solution is raised must not exceed 30° C. Mercurous sulphate, 
treated as described in 3, shall be added in the proportion of about 12 per 
cent by weight of the zinc sulphate crystals to neutralize the free zinc oxide 
remaining, and then the solution filtered, while still warm, into a stock 
bottle. Crystals should form as it cools. 

5. Preparation of the Mercurous Sulphate and Zinc Sul- 
phate Paste. — For making the paste, two or three parts by weight of 
mercurous sulphate are to be added to one by weight of mercury. If the 
sulphate be dry, it is to be mixed with a paste consisting of zinc sulphate 
crystals and a concentrated zinc sulphate solution, so that the whole con- 
stitutes a stiff mass, which is permeated throughout by zinc sulphate crys- 
tals and globules of mercury. 

If the sulphate, however, be moist, only zinc sulphate crystals are to be 
added ; care must, however, be taken that these occur in excess, and are 
not dissolved after continued standing. The mercury must, in this case 
also, permeate the paste in little globules. It is advantageous to crush the 
zinc sulphate crystals before using, since the paste can then be better 
manipulated. 

To set up the Cell. —The containing glass vessel, represented in the 
accompanying figure, shall consist of two limbs closed at bottom, and joined 
above to a common neck fitted with a ground-glass 
stopper. The diameter of the limbs should be at 
least 2 cms. and their length at least 3 cms. The 
neck should be not less than 1.5 cms. in diameter. 
At the bottom of each limb a platinum wire of 
about 0.4 mm. in diameter is sealed through the 
glass. 

To set up the cell, place in one limb mercury, 
and in the other hot liquid amalgam, containing 90 
parts mercury and 10 parts zinc. The platinum 
wires at the bottom must be completely covered 
by the mercury and the amalgam respectively. On 
the mercury, place a layer one cm. thick of the 
zinc and mercurous sulphate paste described in 5. 
Both this paste and the zinc amalgam must then 
be covered with a layer of the neutral zinc sul- 
phate crystals one cm. thick. The whole vessel must 
then be filled with the saturated zinc sulphate solu- 
tion, and the stopper inserted so that it shall just 
touch it, leaving, however, a small bubble to guard 
against breakage when the temperature rises. 

Before finally inserting the glass stopper, it is to be brushed round its 
upper edge with a strong alcoholic solution of shellac, and pressed firmly 
in place. (For details of filling the cell see Note B.) 




Fig 1. 



12 



SYMBOLS, UNITS, INSTRUMENTS. 



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DESCRIPTION OF INSTRUMENTS. 13 



Notes to the Specifications. 

(A). The Mercnrous Sulphate. — The treatment of the mercurous 
sulphate has for its object the removal of any mercuric sulphate which de- 
composes in the presence of water into an acid and a basic sulphate. The 
latter is a yellow substance — turpeth mineral — practically insoluble in 
water ; its presence, at any rate in moderate quantities, has no effect on the 
cell. If, however, it be formed, the acid sulphate is also formed. This is 
soluble in water, and the acid produced affects the electromotive force. The 
object of the washings is to dissolve and remove this acid sulphate, and for 
this purpose the three washings described in the specification will suffice in 
nearly all cases. If, however, much of the turpeth mineral be formed, it 
shows.that there is a great deal of the acid sulphate present ; and it will then 
be wiser to obtain a fresh sample of mercurous sulphate, rather than to try 
by repeated washings to get rid of all the acid. 

The free mercury helps in the process of removing the acid ; for the acid 
mercuric sulphate attacks it, forming mercurous sulphate. 

Pure mercurous sulphate, when quite free from acid, shows on repeated 
washing a faint yellow tinge, which is due to the formation of a basic mer- 
curous salt distinct from the turpeth mineral, or basic mercuric sulphate. 
The appearance of this primrose yellow tinge, which is due to the formation 
of a basic mercurous salt distinct from the turpeth mineral, or basic mer- 
curic sulphate, may be taken as an indication that all the acid has been 
removed ; the washing may with advantage be continued until this tint 
appears. 

(B). filling* the Cell. — After thoroughly cleaning and drying the 
glass vessel, place it in a hot-water bath. Then pass through the neck of 
the vessel a thin glass tube reaching to the bottom to serve for the intro- 
duction of the amalgam. This tube should be as large as the glass vessel 
will admit. It serves to protect the upper part of the cell from being 
soiled with the amalgam. To fill in the amalgam, a clean dropping-tube 
about 10 cms. long, drawn out to a fine point, should be used. Its lower end 
is brought under the surface of the amalgam heated in a porcelain dish, and 
some of the amalgam is drawn into the tube by means of the rubber bulb, 
The point is then quickly cleaned of dross with filter paper, and is passed 
through the wider tube to the bottom, and emptied by pressing the bulb. 
The point of the tube must be so fine that the amlagam will come out only 
on squeezing the bulb. This process is repeated until the limb contains the 
desired quantity of the amalgam. The vessel is then removed from the 
water-bath. After cooling, the amalgam must adhere to the glass, and 
must show a clean surface with a metallic luster. 

For insertion of the mercury, a dropping-tube with a long stem will be 
found convenient. The paste may be poured in through a wide tube reach- 
ing nearly down to the mercury and having a funnel-shaped top. If the 
paste does not run down freely it may be pushed down with a small glass 
rod. The paste and the amalgam are then both covered with the zinc sul- 
phate crystals before the concentrated zinc sulphate solution is poured in. 
This should be added through a small funnel, so as to leave the neck of the 
vessel clean and dry. 

For convenience and security in handling, the cell may be mounted in a 
suitable case so as to be at all times open to inspection. 

In using the cell, sudden variations of temperature should, as far as 
possible, be avoided, since the changes in electromotive force lag behind 
those of temperature. 

CHAPTER III. 
DESCRIPTION OW Il¥STIt¥Jlf«J]¥TS. 

Although no attempt will be made here to fully describe all the different 
instruments used in electrical testing, some of the more important will be 
named and the more common uses to which they may be put mentioned. 

The four essential instruments for all electrical testing of which all other 
instruments are but variations, are: the battery, the galvanometer, the 
resistance-box, and the condenser, and following will be found a concise 
description of the more important types of each. 



14 



SYMBOLS, UNITS, INSTRUMENTS. 



PRIMARY BATT£RI£§, 

A Voltaic Battery is a device for converting chemical energy directly 
into electrical energy. 

If a plate of chemically pure zinc and a plate of copper are immersed in 
dilute sulphuric acid no chemical action takes place. As soon, however, 
as the zinc and copper plates are connected by an electrical conductor 
outside of the liquid a vigorous chemical action is set up, the zinc dis- 
solves in the acid, and hydrogen is liberated on the copper plate. As long 
as this action takes place an electric current passes from the zinc plate 
through the acid to the copper plate and through the conductor back to 
the zinc plate. 

The chemical action in this simple voltaic cell soon becomes weaker, 
and at the same time the intensity of the electric current diminishes and 
finally becomes zero. The diminution of activity is chiefly due to the 
accumulation of hydrogen on the copper plate, causing what is known as 
"polarization." An agent introduced into a galvanic cell to prevent 
polarization is called a "depolarizer." 

The chemical reaction of a voltaic cell is directly proportional to the 
quantity of electricity passing through it. The quantity (in grammes) of 
an element liberated or brought into combination electrolytically by one 
coulomb of electricity, is called its electrochemical equivalent. (See table 
on second page of section on "Electrochemistry.") The theoretical con- 
sumption of material in a voltaic battery doing a certain amount of work 
can be calculated from the electrochemical equivalent of the material. For 
example, in a battery doing work equivalent to one horse-power hour 

746 X 3600 X .003387 



grammes of zinc will be dissolved; E being the E.M.F. of the battery. 

In practice the consumption of material in a galvanic cell is larger, due 
to local action. Commercial zinc always contains iron, carbon, or other 
impurities; as soon as these are exposed to the liquid, local closed circuits 
are formed resulting in the consumption of zinc. To prevent this wasteful 
action, the zinc must be amalgamated with mercury. The action of the 
mercury brings the pure zinc to the surface and in contact with the liquid. 
Amalgamated zinc is not attacked by diluted sulphuric acid. 

Zinc is amalgamated by immersing it in dilute sulphuric or hydrochloric 
acid for a few minutes to give it a clean surface, then mercury is rubbed on 
with a hard brush or cloth fixed on the end of a piece of wood. 

Primary Cells may be classified into two groups; closed circuit and open 
circuit. 

Closed Circuit Cells. — Cells of this group must be capable of work- 
ing on a closed circuit of moderate resistance for a long period without sen- 
sible polarization. They must, therefore, contain an effective depolarizer. 
The best depolarizers are copper sulphate CuS0 4 , strong nitric acid HN0 3 , 
chromic acid Cr0 3 , oxide of copper CuO, and chloride of silver AgCl. 

The following table contains data on the representative types of closed 
circuit cells. 



Name. 


+Plate. 


Electrolyte. 


Depolarizer. 


— Plate. 


E.M.F. 


R. 


Daniell 
Grove 
Bunsen 
Peggen- 
dbrff 

Lande 
Davy 


Zinc 


Sulphuric Acid 
ii ii 

Caustic Potash 
Ammonium Chloride 


Cop. sulphate 
Nitric Acid 

Bichromate of 

Potassium- 

Sulp. acid 

Copper Oxide 

Silver Chloride 


Copper 

Platinum 

Carbon 

Iron 

Silver 


1.08 
1.9 

1.8 
2. 

1. 
1.1 


1. 
.15 
.2 

.2 

.1 
4.5 



The values given as electromotive force and internal resistance of 
the different types of cells are approximate only. The E.M.F. depends 
upon the purity of the materials, the concentration of the solution; the 
internal resistance, furthermore, depends upon the dimensions and general 
arrangement of the cells. 



BATTERIES. 



15 



Open Circuit Cells. — Cells of this group are only suitable for use when 
the circuit is to be closed for a few seconds at a time, as for example for 
call bells, annunciators, etc. Such batteries do not need to contain a quick 
acting polarizer, as the effect of polarization can be taken care of during the 
intervals of rest, either by a slow acting depolarizer or even without any 
polarizer. It is, however, of the greatest importance that no local action 
takes place in these cells on open circuit. 

The following table contains data on the representative types of open 
circuit cells: 



Name. 


-f Plate. 


Electrolyte. 


Depolarizer 


— Plate. 


E.M.F. 


R. 


Leclauche 

Law 

Gassner 


Zinc 

Zinc 
Zinc 


Sol. of Sal-ammoniac 
ii ii ii 

Oxide of Zinc, sal-am- 
moniac, Chloride of 
zinc, plaster 


Binoxide of 
Manganese 
None 


Carbon 

Carbon 
Carbon 


1.48 

1.37 
1.3 


.5 

.4 

.2 




Fig. 2. 



The Oravity Cell. 

The elements are copper and zinc; the solution is sulphate of copper, or 
"bluestone," dissolved in water. The usual form (see Fig. 2) is a glass jar, 
about 8 inches high and 6 inches diameter. The 
copper is made of two or more layers fastened in 
the middle, spread out, and set on edge in the 
bottom of the cell, the terminal being a piece of 
gutta-percha insulated copper wire extending up 
through the solution. 

The zinc is usually cast with fingers spread out, 
and a hook for suspending from the top of the jar 
as shown, the terminal being on top of the hook. 
This form of zinc is commonly called "crowfoot," 
and the battery often goes by that name. Some- 
times star-shaped zincs are suspended from a tri- 
pod across the top of the jar. The "bluestone" 
crystals are placed in the bottom of the jar about 
the copper, the jar then being filled with water to 
just above the "crowfoot" or zinc. A table- 
spoonful of sulphuric acid is added. A saturated 
solution of copper sulphate forms around the cop- 
per; and, after use, a zinc sulphate solution is 
formed around the zinc, and floats upon the cop- 
per sulphate solution. The line of separation between the two solutions 
is called the blue line. As the two solutions are kept separate because of 
their different specific gravities, the name "gravity cell" is employed. 

This cell does not polarize, and the E.M.F. is practically constant or uni- 
form at about 1 volt on a closed circuit. If the circuit is not closed, and the 
cell does not have work enough to prevent mixing of the two solutions, the 
copper sulphate coming in contact with the zinc will become decomposed; 
the oxygen forming oxide of zinc, and the copper depositing on the zinc hav- 
ing an appearance like black mud. 

Care of the Oravity Cell. — For ordinary "local work" about three 
pounds of "bluestone" per cell is usually found best. When this is gone 
it is better to clean out the cell and supply new solution than to try to re- 
plenish. "Bluestone" crystals should not be smaller than a pea nor as 
large as an egg. In good condition the solution at the bottom should be a 
bright blue, changing to water-color above. A brownish color in any part 
denotes deterioration. 

To prevent evaporation of the solution it is well to pour a layer of good 
mineral oil over the top when the cell is first set up. This oil should be 
odorless, free from naphtha or acid, and non-inflammable under 400° F. If 
oil is not used, dipping the top of the jar in melted paraffin for about an 
inch will prevent the salts of the solution from climbing over the edge. In 
starting a new battery it is best to short circuit the cells for twenty-four or 
forty-eight hours to form zinc sulphate and lower the internal resistance, 



16 



SYMBOLS, UNITS, INSTRUMENTS. 



The internal resistance of the ordinary gravity cell is 2 to 3 ohms, depending 
on a number of conditions, such as the size of plates, the nearness together, 
and the nature of the solution. 

Never let the temperature of gravity cells get below 65° or 70° F., as the 
internal resistance increases very rapidly with a decrease in temperature. 

The JLet lanche Cell. 



This cell is one of the most commonly used outside of telegraphy, and up 
to the advent of the so-called dry cell was practically the only one in use for 
house and telephone work. The elements are zinc and carbon, with per- 
oxide of manganese about the carbon plate for a depolarizing agent. As 
usually constructed — for there are many modifications of the type — the jar 
is of glass, about 7 inches high and 5 inches in diameter, or sometimes square. 
The zinc is in the form of a stick, about a half inch diameter by 7 inches 
long, and is placed in one corner of the jar in a solution of sal-ammoniac. 
The carbon plate is placed in a porous cup within the jar, and the space 
around the carbon in the cup is filled with small pieces of carbon and gran- 
ulated peroxide of manganese. The sal-ammoniac solution passes through 
the porous cup and moistens the contents. This cell will polarize if worked 
hard or short circuited, but recuperates quickly if left on open circuit for 
a while* The resistance of the Leclanche" cell varies with its size and con- 
dition, but is generally less than one ohm. The initial E.M.F. is about 1.5 
volt. It is desirable not to use too strong a solution of sal-ammoniac, as 
crystals will be deposited on the zinc; and not to let the solution get too 
weak, as chloride of zinc will form on the zinc; both conditions will 
materially increase the internal resistance of the cell and impair its 
efficiency. Without knowing the dimensions of cells it is not possible to 
state the amount of sal-ammoniac to use; but perhaps as good a way as any 
is to add it to the water until no more will dissolve, 
then add a little water so that the solution will be 
weaker than saturation. Keep all parts clean, and add 
sal-ammoniac and water when necessary. 

Chloride of Silver Dry Cell Battery. 

This cell is extensively used for testing insulation 
of cables, etc., and its elements are a plate of chemi- 
cally pure zinc and a cast plate of chloride of silver 
in an electrolyte paste. 

As ordinarily constructed the jar is of glass about 
2k" long by \" diameter with the zinc and silver plates 
set in as per Fig. 3. The paste is poured in and the 
cell is then hermetically sealed. The terminals are 
led through fiber tops to posts thereon. 

The small size of the cell renders it possible to con- 
struct a battery of from fifty to two hundred and 
twenty cells within a small compass. 

The containing box is provided with a pole-chang- 
ing switch in the cover and with selecting cords and 
tips so that the operator may select any number of 
cells desired. Fig. 4 shows a portable testing battery 
of fifty of these cells complete ready for use. 

The E.M.F. of the chloride of silver cell is .9 of 
a volt, the internal resistance being about 4 ohms. 
The current supplied is quite constant until within 
a few moments of its exhaustion ; they will not dry out 
in any climate, have a long life, and there is no local 
action developed when the cells are not in use. 




Fig. 3. 



Fuller Cell. 

The elements of this cell are zinc in a dilute solution of sulphuric acid 
and carbon in a solution of electropoin. Electropoin consists of three parts 



BATTERIES. 



17 




< 



Fig. 4. Chloride of Silver Cells. 



bichromate of potash, one part sulphuric acid, and nine parts water. Dis- 
solve the bichromate in the water at boiling, and when cool add the sul- 
phuric acid slowly. The zinc plate is in the form of a cone, and is placed 
in the bottom of a porous cup inside a glass jar. The carbon plate is out- 
side the porous cup. 

About two ounces of mercury are placed in the porous cup with the zinc, 
for amalgamation, and the cup is filled with a dilute solution of sulphuric 
acid. The outside jar is filled with the electropoin. In this the carbon 
plate is immersed. 

The E.M.F. is 2 volts, and the internal resistance is about half an ohm. 
The solution is originally of an orange color. When this becomes bluish in 
tint, add more crystals. Should the color be normal and the cell be weak, 
add fresh sulphuric acid. 



ESdison-I<alaiide Cell. 



The elements of this cell (see Fig. 5) are zinc and copper oxide in a water 
solution of caustic potash. The plates are suspended side by side from the 
cover of the jar. The copper oxide, which is plated with a thin film of me- 
tallic copper to reduce the resistance when the cell is first started, is held in 



18 



SYMBOLS, UNITS, INSTRUMENTS. 



a frame attached to the cover. A layer of oil is 
poured on top of the solution to prevent creep- 
ing salts. The E.M.F. is low, starting at .78 
volt, and after working for a time it decreases. 
The internal resistance is also low, being about 
.025 ohm for the largest cell. Very strong cur- 
rents can be taken from this cell : for instance 
the cell having an E.M.F. of .75 volt and resist- 
ance of .025 ohm will produce 30 amperes on 
short circuit. The makers advise, in setting up 
the cell, that only one half of the sticks of 
caustic potash be placed in the jar first, and 
that water be then poured in up to within about 
an inch of the top of the jar. Then stir until 
the potash is dissolved, when one may add the 
remainder of the potash sticks, stirriug as 
before. 

Dry Batteries. 

The general appearance of a cell of dry bat- 
tery is shown in Fig. 6, and the construction Fig. 5. 
varies slightly in the different makes. The 

Burnley dry cell is made of a zinc tube (see Fig. 6) as one element, which acts 
also as the containing jar, a carbon cylinder is the negative element, and an 
exciting solution composed of 1 part sal-ammoniac, 1 part chloride of zinc, 3 
parts plaster, .87 parts flour, and 2 parts water. In constructing the cell a 
plunger somewhat larger than the carbon element is placed in the middle of 






Fig. 6. 



Fig. 7. 



the zinc jar, and the above solution mixture poured in around it, quickly be- 
coming stiff, after which the plunger is withdrawn, the carbon inserted in 
place, and the surrounding space tilled with another mixture consisting of 1 
part sal-ammoniac, 1 part chloride of zinc, 1 part peroxide of manganese, 1 
part granulated carbon, 3 parts plaster, 1 part flour, and 2 parts water. After 
the ingredients are all in place the top is sealed with bitumen or other suit- 
able compound. A terminal is fastened to the zinc cup, and another to the 
carbon plate. The E.M.F. of the Burnley cell is 1.4 volt ; the internal re- 
sistance about .3 ohm, and it gives practically constant E.M.F. during its life. 
The Gasner dry oell } shown in Fig. 7, consists of a zinc cup as the positive 
element, a cylinder composed of carbon and manganese for the negative 
element, and an exciting solution which becomes comparatively hard, made 
up of the following ingredients, viz.: 1 part by weight of oxide of zinc, 1 
part sal-ammoniac, 3 parts plaster, 1 part chloride of zinc, and 2 parts water. 
The E.M.F. and resistance are about the same as for the cell last described 



BATTERIES. 



19 




Fig. 8. Carhart-Clark Standard 
Cell. 



Standard Cells, 

Clark Cell.— The form of cell called 
Clark, specifications for making which 
will be found in the chapter on units, 
is the one adopted as the standard of 
E.M.F. by the International Electrical 
Congress at Chicago in 1893. The posi- 
tive element is mercury, and the negative 
is amalgamated zinc, the electrolytes 
being saturated solutions of sulphate of 
zinc and mercurous sulphate. 

At 15° C. the E.M.F. is 1.434 interna- 
tional volts, and between the tempera- 
tures 10° and 25° C, the increase of 1° C. 
decreases the E.M.F. .00115 volt. 

Later investigations by the Physika- 
lisch Technische Reichsanstalt give the 
value of the E.M.F. as 1.4328 volts at 
15° C; the change due to temperature is 
expressed by the following formula: 
E = 1.4328 — 0.00119 (t — 15° C.) 
— 0.000007 (t— 15° C.) 2 volts. 
In making accurate measurements with 
the Clark cell great care must be taken 
on account of the large temperature co- 
efficient and from the fact that the E.M.F. 
lags behind the temperature change. 

Carhart-Clark Cell.— This cell has the same elements as Clark, but 
the solution of zinc sulphate is saturated at 0° C. The E.M.F. is 1.440 volt, 
and the temperature coefficient about half that of the Clark cell ' 

Weston Cadmium Cell. — The elements of this cell are 'cadmium 
and mercury, the electrolytes being the sulphates of cadmium and mercury. 

If the cadmium sulphate crystals are in excess, the E.M.F. at any tem- 
perature is 

E= 1.0194 -0.000038 (*-20° C.) -0.00000065 (*-20°C.) 2 Int. volts. 
In the cell as made by the Weston Company the cadmium sulphate solu- 
tion is saturated at 4 C and has an E.M.F. = 1.01985 Int. volts with a 
zero temperature coefficient. The E.M.F. remains constant for years if 
no currents in excess of .0001 amp. be passed through the cell. 

The Weston cell has largely superseded the Clark cell as a working stand- 
ard on account of its constancy and its freedom from temperature coefficient. 

Grouping- of Battery Cells. 

Series. — When it is desired to obtain an E.M.F. greater than that of one 
cell, two or more are connected together in series; that is, the positive termi- 
nal of one cell is con- volts 

nected to the negative - V - + - -t-- 4~— + - + '- 4- - + - 

terminal of the next, 
and so on until the 
number of cells required 
to produce the E.M.F. 
wanted are connected. 
For example, the 
E.M.F. of one cell of 
Leclanche is 1.47 volt; 
then 10 cells connected 
in series as in Fig. 9 
would give an E.M.F. 
at the extreme termi- 
nals of 14.7 volts. 

multiple. — If it 
be desired to obtain 
out change of E.M.F., 



-^VWWVJ^ 




Fig. 9. Battery Cells in Series. 



more current strength, i.e., more amperes with- 
., then more cells must be placed along side the 
others, that is, in parallel with the first row; each row or series of cells 
producing the same E.M.F. and joined together at the ends, positive 



20 



SYMBOLS, UNITS, INSTRUMENTS. 



terminals to positive terminals, and negative to negative, adding their cur- 
rents together at the same E.M.F. as in Fig. 10 below. 

If still more current strength be needed, another series of cells may be 
added, and their current added to the circuit, making three times the current 
of one series. 




Fig. 10. Battery Cells in Multiple 



The reason for this is, that when two or more resistances are placed in 
parallel or multiple, the equivalent resistance is decreased, as is shown in 
another chapter. If the resistance of one series be 10 ohms, the resistance 
of two series in multiple would be one-half of ten, or 5 ohms ; that of three 
series in parallel, one-third, or 3.33 ohms ; and of four series, 2.5 ohms. 



Let 



E — E.M.F. of a single cell, 
r = internal resistance of one cell, 
R — external resistance in a circuit. 



Then for n cells arranged in series, the current which will flow wili be 
represented by the formula, 



nE 
' nr-{- R~ 



r + - 



If R is very small as compared with nr, then I =. — » or the current is the 
same as that from one cell on short circuit. r 

If, as in telegraph work, nr is very small as compared with R, then 

/— -— , or the current increases in proportion to the number of cells. 
R 
The value of r is nearly inversely proportional to the area of the plates 
when fronting each other in the liquid, and directly as their distance apart. 
Therefore, if the area of the plate is increased a times, for one cell 



I — 



E 



aE 
r + aR' 



Let iV= the total number of cells in the battery, 

n« rz number of cells in each series, 
rip =z number of sets or series in parallel. 

Then the internal resistance of the whole battery 



Up 

To find the best arrangement of a given number of cells (A r ) to obtain a 
maximum current (/) working through an external resistance (/?), make 

— /?, or the internal resistance of the whole battery equal to R. 

Up 

Si r total E.M.F. 

In any circuit /=: . . . : — i and for any arrangement 

J total resist. 



BATTERIES. 21 

_ n»E _ n P n»E 

n»r ~~ jut -f- n P R ' 

n T ' 

When arranged for maximum current through a given external resistance B, 

Wt = y — and np = y — . 

To find the greatest current that can be obtained from a given number of 
cells (N ) through a given external resistance (R), 

2 > /2r 

To find the number of cells in series (?i«) and in parallel (n p ) required to 
give a current (/) through an external resistance (R) and to have an effi- 
ciency (F). 

„«, . „ External work 

Efficiency E = — — — 

Total work 

1 2 R R 



I*(™ + X) ™+R 
\n P ) n P ' 



< n P ) n P 

The internal resistance of the whole battery is 

n 8 r R(l — F) , _ n,EF 

— = — ^—s — - and / = — — - 
n P F R 

IR Ir 

n ° = an? %> = 



E (1 — F) 

EIECTRICAL n^ASlBIYC; IWSTItUIflEMTS. 

The electrical measuring instruments most used in practice are galvanom- 
eters, resistance boxes, condensers, voltmeters, ammeters, and watt- 
meters, with variations of the same, such as millivoltmeters, milliammeters, 
etc. 

Gal vanometerg. 

These are instruments for measuring the magnitude or direction of electric 
currents. The term galvanometer can also be properly applied to the many 
types of indicating instruments, such as voltmeters and ammeters, where a 
needle or pointer is under the influence of some directive force, such as the 
earth's field, a spring, a weight, a permanent magnet, or other means, and 
is deflected from zero by the passing of an electric current through its 
coils. 

Nearly all galvanometers can be separated into two classes. The first is 
the moving-needle class. A magnetized needle of steel is suspended with 
its axis horizontal so as to move freely in a horizontal plane. The suspen- 
sion is by means of a pivot or fiber of silk, of quartz, or of other material. 
The needle normally points in a north and south direction under the influence 
of the earth's magnetic field, or in the direction of some other field due to 
auxiliary magnets. Near to the needle, and frequently surrounding it, is 
placed a coil of wire whose axis is at right angles to the normal direction of 
the needle. When a current is passed through the coil the needle tends to 
turn into a new position, which lies betw r een the direction of the original 
field and the axis of the coil. 

The second class is the moving coil or d'Arsonval class. A small coil is 
suspended by means of a fine wire between the poles of a magnet. Its axis 
is normally at right angles with the lines of the field. Current is led into 
the coil by means of the suspension wire, and leaves the coil by a flexible 
wire attached underneath it. 

The figure of merit of a galvanometer is (a) the current strength required 
to cause a deflection of one scale division ; or (6) it is the resistance that 
must be introduced into the circuit that one volt may cause a deflection of 
one scale division. This expression for the delicacy of a galvanometer is 



22 



SYMBOLS, UNITS, INSTRUMENTS. 



insufficient unless the following quantities are also given : the resistance 
of the galvanometer, the distance of the scale from the mirror, the size of 
the scale divisions, and the time of vibration of the needle. 

The sensitiveness of a galvanometer is the difference of potential neces- 
sary to be impressed between the galvanometer terminals in order to pro- 
duce a deflection of one scale division. 

Movingr-Needle Galvanometers. 

(a.) The Tangent Galvanometer. If the inside diameter of the coil which 
surrounds a needle, held at zero by the earth's held, be at least 12 times the 
length of the needle, then the deflections of the needle which correspond to 
different current strengths sent through the coils, will be such that the 
current strengths will vary directly as the tangents of the angles of deflec- 
tion. Such an instrument is called a tangent galvanometer. It was for- 
merly much used for the absolute measurement of current. It has, however, 
many correction factors, some of which are of uncertain magnitude ; and, 
furthermore, for accuracy in the results yielded by it one must have an 
exact knowledge of the value of the horizontal component of the earth's 
magnetism. This quantity is continually changing, and is affected much 
by the presence of large masses of iron and the existence of heavy currents 
in the vicinity. 

Let r = the radius of a tangent galvanometer coil, in centimeters 
n = the number of turns in the coil, 
H=. the horizontal intensity of the earth's magnetism, 
T= the current flowing in the coil in absolute units, and 
= the deflection of the needle, then 




Fig. 11. Tangent Galvanometers. 



GALVANOMETERS. 



23 



I=z L - Stan 9. 

2ttU 



For convenience the term 



2irn . 



i.e., the strength of the field produced 



at the center of the coil by the unit of current, is called the constant of the 
galvanometer, and is represented by G, whence 

7— — tan 9 



The current in amperes equals 10 I. 

(b.) Kelvin Galvanometers. The most sensitive galvanometers made are 
of a type due to Lord Kelvin. Fig. 12 shows one form of this instrument. The 
moving system consists of a slender quartz rod, to the center of which is 
fastened a small glass mirror. Parallel to the plane of the mirror, and at 

one end of the quartz tube, is fas- 
tened a complex of carefully se- 
lected minute magnetic needles. 
The north ends of those needles 
all point in the same direction. 
At the other end of the quartz 
tube is fastened a similar complex 
with the polarity reversed. Were 
the two complexes of exactly 
equal magnetic moment, then, 
when suspended in the earth's 
field, no directive action would be 
felt. In fact, this action is very 
small. The combination forms 
what is called an astatic system. 
Each magnetic complex is in- 
closed between two wire coils. 
The four coils are supplied with 
binding-posts, so as to permit of 
connection in series or in parallel. 
Current is sent through them in 
the proper direction, to produce 
in each case deflections the same 
way. Quartz fiber, which ex- 
hibits no elastic fatigue and 
which is very strong, is used as 
a suspension. An adjustable 
magnet is mounted on the top of 
the galvanometer. By means of 
it the directive action of the 
earth's field can be modified to 
any extent. Under weak direc- 
tive force the sensitiveness in- 
creases greatly, and the period of 
oscillation of the needle becomes 
long. The limit of sensitiveness 
is largely influenced by the pa- 
tience of the observer. 

For very precise work the de- 
flections of the needle are ob- 
served by means of a telescope 
and scale. Fig. 13 shows such an 
instrument. The moving mirror 
reflects an image of the scale into 
the objective of the telescope. 
Continuous work with the tele- 
scope is apt to injure the eyes, and is certainly tiresome. Where much gal- 
vanometer work is being done by the same person, a ray of light from a 
small electric, gas, or oil lamp is so directed as to be reflected from the 
mirror on the needle upon a divided scale. Such a lamp and scale is shown 
in Fig. 14. In order to bring the needle quickly to rest when under the in- 




Fig. 12 e — Kelvin Reflecting Astatic 
Galvanometer with Four Coils. 



24 



SYMBOLS, UNITS, INSTRUMENTS. 




FIG. 13. 




Fig. 14. 



GALVANOMETERS. 



25 



fluence of a current, some method of damping must be employed. One 
method is to attach a mica vane to the moving system, and allow it to swing 
in an inclosed chamber which contains air or oil. Sometimes the moving 
needle is inclosed in a hollow made in a block of copper. The eddy currents 
induced by the moving needle react upon it and stop its swinging. 

movingr-Coil Galvanometers. 

These galvanometers are to be preferred in all cases except where the 
utmost of delicacy is required. In the most sensitive form, with permanent 
magnetic field, they can be made to deflect one millimeter with a scale dis- 
tance of one meter, when one microvolt is impressed between the terminals 
of the coil. This is sufficient for nearly all purposes. The sensitiveness can 
be further increased by using an electromagnetic field. The moving-coil 



i 




Fig. 15. 



form of galvanometer has the following good points : its readings are but 
slightly affected by the presence of magnetic substances in the vicinity, and 
are practically independent of the earth's field ; the instrument can be easily 
made dead-beat; and many forms are not much affected by vibrations. 
Fig, 15 shows a form of D'Arsonval galvanometer of high sensibility. The 
coil (shown at the right) is inclosed in an aluminum tube. Eddy currents 
are induced in this tube when the coil swings. They cause damping, and, 
with a proper thickness of tube, the system may be made aperiodic. 

Ballistic Galvanometers. 

Ballistic galvanometers are used for measuring or comparing quantities of 
electricity such as flow in circuits when a condenser is discharged or mag- 
netic flux linkages are disturbed. The time of oscillation of the needle 



26 



SYMBOLS, UNITS, INSTRUMENTS. 



must in such cases be long as compared with the duration of the discharge. 
If there be no damping of the needle the quantities of electricity are pro- 
portional to the sines of half the angle of the first throws of the needle. 
All galvanometers have some damping. The comparison of quantities of 
electricity can easily be made with galvanometers of moderate or even 
Strong damping. Absolute determination of quantity by means of the 
ballistic galvanometer requires great experimental precautions. (See the 
Galvanometer, by E. L. Nichols.) 

Instrument for the Measurement of Alternating- Currents, 
by E. JF. Horthrup. 

(Abstract from Trans. A. I. E. E.) 

The instrument here described was developed to meet the frequent need 
of means for easily and accurately calibrating alternating-current instru- 
ments, ammeters and voltmeters, whatever their capacity. 

(a) It is used as a zero instrument, and does not depend upon any cali- 
bration or determination of any constant of the instrument; (6) it operates 
with extreme sensitiveness, and being perfectly "dead-beat" is adapted to 
work with fluctuating currents; (c) it may be used with or without low. 
resistance shunts; when used with them it has an unlimited upward range 
of current measurement; and when used without them its lower range is 
down to from two to five milliamperes; (d) as the operation of the instru- 




ment depends upon the heating effect of currents it is wholly independent 
of wave-form and frequency. 

Referring to Fig. 16, two small wires, AB, of No. 33 hard-drawn silver 
wire when shunts are used, lie parallel to each other at a distance of 
0.158 in., being held near their extremities by ivory clamps, CC. Each of 
the ends of the two wires are connected to binding posts through the 
medium of heavy leads and soldered joints. 

One face of a small circular disk of ivory, D, rests against the two wires 
at their middle point, a 0.5-in. circular mirror being fastened to the other 



GALVANOMETERS. 



27 



face. Fastened at the center of the ivory disk and half way between the 
wires, when the disk is in position on the wires, is a small hook. To this, 
through the medium of a thread, is fastened a small adjustable spiral spring. 
The small ivory disk maintains its position by friction and the tension of 
the spring. The wires bend back under the tension of the spring about 
0.875 in. from the vertical. The ivory disk does not rest directly upon the 
wires but bears upon each wire through the medium of a small agate stud 
shaped like the head of a screw, each wire being in the slot of the agate stud 
which rests upon it. 

Tne two ivory clamps holding the wires near their upper extremity are 
made separately adjustable in a vertical 
direction by means of thumbscrews which 
pass through the hard-rubber top of the 
instrument. Springs s s prevent lost motion 
when the ivory clamps are screwed up or 
down. 

The arrangement of parts above described 
is supported by a brass frame and a circular 
hard-rubber top. This frame drops into a 
circular nickel-plated brass case (Fig. 17). 
The case has a window in it directly in 
front of the mirror on the small ivory disk. 
Fig. 17 shows clearly the arrangement of 
parts and the appearance of the instrument. 

By means of the adjusting screws the 
tension of the two wires may be so adjusted 
that the plane of the mirror will be vertical 
to a line drawn in the direction of the 
spring which holds the mirror against the 
wires. Now if any elongation occurs in the 
wire on the right, that side of the mirror 
will be drawn down or back by the spring, or 
a deflection to the right is obtained. Like- 
wise, if an elongation takes place in the wire 
on the left, the mirror will deflect to the left. 
If, however, an exactly equal elongation 
occurs in both wires at the same time, the 
plane of the mirror will not tilt but simply move back keeping parallel to 
itself. 

If the mirror is observed with a telescope and scale, say at a distance of 
one meter, very minute angular deflections of the mirror will be easily 
observed, while a sinking back of the plane of the mirror away from the 
scale will not be observable. 

Now if an alternating current of unknown strength be sent through the 
wire A, the wire will elongate, deflecting the mirror toward the left. Pass 
an adjustable direct current, which can be measured, through the wire B, 
until the deflection is reversed and brought back to zero on the scale. If 
when the deflection is zero, and certain precautions to be stated later have 
been observed, the strength of the direct current is known, the strength of 
the alternating current will also be known; for it is exactly equal to the 
direct current. This, however, is on the assumption that equal currents 
through the wires A and B produce equal elongations of the wires. Pre- 
viously to comparing the currents, connect the wires A and B in series, 
and send a current through the circuit; if under these conditions the mirror 
be not deflected at all, or only slightly, it proves that the two wires are 
practically equally elongated by the same current strength. The limit of 
this possible small deflection may be taken as the true zero of the instru- 
ment. If this zero is maintained under working conditions, it means that 
the strength of the alternating current in the wire A, is equal to the strength 
of the adjustable and measured direct current in the wire B. 

The arrangement of the complete circuits for measuring a large alter- 
nating current for the purpose of calibrating an alternating current am- 
meter A is shown diagrammatically in Fig. 18. An important accessory to 
the instrument is a quick-acting double-throw switch, marked S in the 
diagram. Wa and Wd represent the two wires of the instrument and m 
the mirror. R is a low-resistance shunt, preferably of manganin, having 




28 



SYMBOLS, UNITS, INSTRUMENTS. 



a negligible temperature coefficient, furnished with tap-off points c and d, 
between which the resistance R has previously been determined. The 
ammeter indicated in the diagram will measure from one to two amperes 
of direct current; r 3 is a slide wire resistance along which a slider p may be 
moved, thereby varying the pressure difference at a-b from zero to the 
value of the electromotive force of the storage battery. 

The points a, b, on the direct-current side of the circuits have leads 
attached to them which go either to an accurately calibrated direct-current 
laboratory standard voltmeter, or to a potentiometer. 




AMMETER 
VOLTMETER OR 
POTENTIOMETER 



Fig 18. 



When the instrument is installed, a permanent adjustment of the re- 
sistances at any convenient temperature of the wires and leads must be 
made as follows: (see Fig. 18.) 

The resistances, 9 to 10 = 7 to 8, 

10 to 1 -f- 9 to 5 = 8 to 4 + 7 to 2 and 
2 to c + 4 to d — 3 to a + 6 to b. 

Thus while this gives the over-all resistance from a through the wire Wd 
to b equal to the over-all resistance from d through the wire Wa to c, the 
different portions of the circuit must be matched in resistance as stated 
above. 

When the switch S is closed on the alternating-current side the two 
wires Wa and Wd are thrown in parallel, and the two parallel-connected 
circuits have the same resistance, by construction, and that to these par- 
allel circuits at the points 2 and 4 is applied the same potential difference, 
this potential difference being the drop on the low resistance R carrying 
the alternating current. The drop over R, inasmuch as it is a low resis- 
tance, is only slightly lowered by being shunted by the two wires of the 
instrument and their leads, and this iowering of the potential is not appre- 
ciably greater when the two wires in parallel shunt the resistance R than 
when only one wire with its leads shunts the resistance. Disregarding 
the slight lowering of the potential, both wires will now have passing through 
them equal currents, each current being nearly the same as would pass 
through the one wire Wa if the switch S were open, and only this wire could 
receive current. . 

With the resistances of the parallel circuits correctly adjusted to equality, 
both wires will get equal currents, both will elongate equally or very nearly 
so, and the mirror m instead of rotating will move back, maintaining its 
plane parallel to the position which it has with no current passing. 

When the switch S is thrown to the direct-current side, the potential 
drop over the resistance R is now applied to the wire Wd only; and the direct 
potential difference between the points a and b is applied to the wire Wd. 



GALVANOMETERS. 



29 



This drop between a and b can be varied by the slider p and measured by 
a voltmeter or potentiometer applied at a, b. The ammeter gives the 
current taken by the wire Wd. 

The shunt resistance R may be designed to carry any current, however 
large. The same resistance R, or a combination of resistances, may be 
designed with several tap-off or potential points, so that the instrument 
may always have approximately the same potential applied to its alter- 
nating-current side, whatever the strength of the current to be measured. 
This potential drop is best made between 0.25 and 0.5 volt. The neces- 
sary drop of potential being so low, the energy dissipated in the shunts 
is small, and therefore they may be of very moderate size. It is also easy 
to make them practically non-inductive. 



{ 



Galvanometer Shunt Boxes. 

It is often desirable to use a galvanometer ot high sensibility for work 
demanding a much lower sensibility. Again, it may be convenient to cali- 
brate a galvanometer of low 
sensibility, while it would be 
inconvenient to calibrate a more 
sensitive one It is therefore 
useful to be able to change the 
sensibility in a known ratio. 
Convenience dictates that sim- 
ple ratios be used, and those 
almost universally taken are 10, 
100, and 1000; that is J,^,or ft § B , 




AAMAA- 

Fig. 19. 



■ -f- 1 = the Multiplying power of the shunt. 



part of the current flowing is allowed to go through the galvanometer while 
the remainder is diverted through a shunt. In Fig. 19 let 

G == the resistance of the galvanometer, and 

S = the resistance of the shunt, 

then the joint resistance of the two is ■ • 

(jr -f- b 

If I = the total current flowing in the circuit, and 

if L = the part flowing through the galvanometer, 

then 1^ _ G + S _ G 

I, ~~ S ~ S 
The resistance of a shunt which will give a certain multiplying power, n, is 

equal to • Fig. 20 shows a form 

n — 1 
of shunt used with a galvanometer, al- 
though it is perfectly feasible to use an 
ordinary resistance box for the purpose. 
Messrs. Ayrton & Mather have developed 
a new shunt, which can be used with any 
galvanometer irrespective of its resist- 
ance : following is a diagram of it. 

A and B are terminals for the galvano- 
meter connections. B and C are the in- 
going and outgoing terminals for battery 
circuit. To short circuit G, place plugs 
in j and f. To throw all the current 
through G, put a plug in f only. To use 
the shunts, place a plug in h, and leave it 
there until through using. In this method 
it is not necessary to know the resistance 
of either G or r. The shunt box can 
therefore be used with any galvanometer. 
Temperature variations make no differ- 
ence, provided they do not take place Fig. 20. 
during one set of tests. The resistance 

r may be any number of ohms, but in order not to decrease the sensibility 
too much r should be at least as large as G. The resistance r is divided for 
use as follows : permanent attachments to the various blocks are made at 

points in the coil corresponding with </w ^ — — - — ohms. 

1000, 10U, 1U 
o 




30 



SYMBOLS, UNITS, INSTRUMENTS. 




-^k ,/WWWVW ' 



Fig. 21. Ayrton & Mather's Universal Shunt. 
PRACTICAL STANDARD! OF RESISTANCE. 

The unit of resistance, the international ohm, is represented by the resis- 
tance of a uniform column of mercury 106.3 cm. long and 14.4521 grammes in 
mass, at 0° C; but in practice it is not convenient to compare resistances 
with such a standard, and therefore secondary standards of resistance are 
made up and standardized with a great degree of precision. These sec- 
ondary standards are made of wire. The material must possess perma- 
nency of constitution and of resistivity, must have a small temperature 
coefficient of resistivity, must have a small thermo-electric power when 
compared with copper, and should have a fairly high resistivity. Manganin 
when properly treated possesses all of these qualities (see "Properties of 
Conductors"). Platinoid is also frequently used. An assemblage of 
standards of various convenient magnitudes in a single case is called a 
resistance box, or rheostat. 

Fig. 22 shows the pattern adopted by the Physikalisch Reichsanstalt and 
now in general use. For very low resistances having a high current-carry- 
ing capacity a larger form is used shown in Fig. 23. These are immersed 
in oil and cooled by water circulating through coiled pipe. They are made 




Fig. 23. 



RESISTANCES. 



31 



in values of .01, .001 and .0001 ohm, the resistances being that between 
the two small binding posts called the potential terminals. 



IV Ii*» at* tone Bridge. 

The form of resistance box most frequently met with is some type of 
"Wheatstone's bridge," the theory of which is described elsewhere. 

The coils are usually of silk insulated wire wound non-inductively on 
spools, with the ends attached to brass blocks, so arranged that brass 
plugs can be inserted in a hole between two blocks, thus short-circuiting 
the resistance of the particular bobbin over which the plug is placed. By 
non-inductive winding is meant that the wire is first doubled, then the 
closed end is placed on the bobbin and the wire wound double about the 
bobbin. By this method any electro- 
magnetic action in one wire is neu- 
tralized by an equivalent action in the 
other, and there is no inductive effect 
when the circuit is opened or closed. 

The post-office pattern of Wheatstone 
bridge is one of the most commonly 
used, a diagram of its connections being 
shown in Fig. 24. 

One arm of the bridge has separate 
resistances of the following values: 
1, 2, 3, 4, 10, 20, 30, 40, 100, 200, 300, 
400, 1000, 2000, 3000, and 4000 ohms. 
Another arm is left open for the unknown 
resistance, x, which is to be measured. 
The remaining two arms each have three 
resistance coils of 10, 100, and 1000 ohms 
respectively. Two keys are supplied 
with the P.O. bridge, one for closing the 
battery circuit, and the other for closing 
the galvanometer circuit. The battery 
key should be closed first; and in some 



< 




Fig. 24. 



Galvanometer Galvanometer 



Battery 



Battery 




Fig. 25. Diagram of Anthony Bridge. 



32 



SYMBOLS, UNITS, INSTRUMENTS. 



instruments the two keys are arranged with the battery key on top of 

the galvanometer key, so that but one finger and one pressure are necessary. 

Prof. Anthony has devised a resistance box in which there are 10 one 

ohm coils, 10 tens, 10 hundreds, and 10 thousands. Any number of any 

group can be connected either in series or in 

tens units multiple. The means of accomplishing this 

<£*Vt\ <tf***h are seen clearly in the cut. 

r \5 

Decade Methods. 

The Wheatstone bridge arrangement has 
the disadvantage of requiring a large number 
of plugs to short-circuit the resistances not 
in use, which introduces an element of uncer- 
tainty as to resistance of the plug contacts 
and the necessity of adding up the values of 
all the unplugged resistances in order to deter- 
mine the value. 

Fig. 26 shows the Weston arrangement of 
coils requiring but one plug per decade and a 
small number of coils. 

In a later decade arrangement by Leeds & 
Northrup, 1, 3, 3', and 2 ohm coils are con- 
nected in series as shown in Fig. 27. 

Let the terminal of the 1 ohm coil and the 
2 ohm coil and the points of union of the 

coils be numbered (1), (2), (3), (4), (5) as shown in Fig. 27. The current 

enters at point (1) and leaves the coils at the point (5) traversing 1, 3, 3 , 

2 = 9 ohms in all. If this series is multiplied 

by any factor n, then n (1 + 3 + 3' -f- 2) = n 

9 ohms. It will be seen that if the points 

(1) and (5) are connected all the coils are (2) 

short-circuited and that the current will traverse 

zero resistance. If the points (2) and (5) are 

connected the 3, 3\ and 2 ohm will be short- ,/ |(3) 

circuited and the current will traverse 1 ohm. 




Fig. 



26. Decade Resist- 
ance Box. 



1 



(1) 




WVVVAi 



By extending this process so that we connect 






±5y extending tnis process so umi we uumicuu i 

two and only two points at a time, it is possible (4Jt 2 

to obtain the regular succession of values VAAAAAAAA* 

n (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) the last value 
being obtained when no points are connected. 
The following table shows the points which 
must be connected to obtain each of the above 
values and the coils which will be in circuit for giving each value: 



(5; 



Fig. 27. 



Value. 



Points Connected. 



= 


(5-1) 


1 = 


(2-5) 


2 = 


(4-1) 


3 = 


(2-4) 


4 = 


(3-5) 


5 = 


d-3) 


6 = 


(2-3) 


7 = 


(5-4) 


8 = 


(1-2) 


9 = 


(0) 



Coils Used 







I 




2 




1, 


2 


1, 


3 


W 


, 2 


1, 


3', 2 


1, 


3, 3' 


3, 


3', 2 


1. 


3, 3', 2 



Fig. 28 shows a method of connecting these points two at a time with the 
use of a single plug. 

The circles in the diagram represent two rows of ten brass blocks each. 
To the first two blocks at the top of the rows, the points 5 and 1 of dia- 
gram 3 are connected, to the second two points 2 and 5 are connected and 



WATEK RHEOSTATS. 



33 




so on, no points being connected at the last pair of blocks. It is evident 
that if a plug be inserted between the blocks 1 and 5, the points 1 and 5 
of diagram 3 are connected giving the value ; if between the blocks 2 and 
5, the points 2 and 5 are connected giving the value 1, 
and so on. The value 9 is obtained when the plug is 
disposed of by being inserted in the last pair of blocks 
which have no connections. 

WATER RHEOSTATS. 

In testing dynamos and other electrical apparatus 
producing large amounts of energy, it is necessary to 
have resistances of a capacity sufficient to absorb the 
energy developed, and this is almost invariably done 
by the use of the water rheostat, which in its 
simplest form consists of a box or barrel of wood, in 
which are placed two metal electrodes which can be 
adjusted in relation to each other so as to increase 
the resistance by separating them, or decrease it by 
approaching them to each other. Coils of galvanized 
iron wire in running water are much used, and when 
still water is used it is the practice to increase its 
conductivity by adding soda or common salt. 

H. S. Webb in American Electrician, February, 1898, 
gives results of a number of experiments: 

(a) Daniel jar (6i" dia., 8" deep) horizontal sheet 
iron electrodes and water from faucet. With plates 
f inch apart would not carry 4 amperes more than 
fifteen or twenty minutes without becoming too hot. 
P. D. 200 volts. With 2 amperes at 71 volts for one 
hour, temperature rose to 167° F. 

Result: safe cross section in 30.7 sq. in. for 2 to 2\ amperes, with clear 
water and horizontal electrodes, watts absorbed per cu. in. of water, 10. 

(b) Same jar and electrodes as above, but saturated solution of salt 
water used: 11 amperes, 7 volts, electrodes 7f " apart; in three hours tempera- 
ture rose to 122° F. and was slowly rising when stopped. Watts absorbed 
per cu. in. of liquid, .4. 

(c) Wooden trough 42" X 6£" X 8", vertical sheet iron electrodes; cross 
section of liquid, 44 sq. in. With 10% solution of salt water, and 10 amperes 
flowing, temperature at end of run 95° F. Electrodes 41!" apart. P. D. 
20 volts. Current density, about j amp. per sq. in.; watts absorbed, .11 
watt per cu. in., would probably carry 13 to 15 amperes safely. 

It is apparent that salt increases the current carrying capacity, but 
decreases watts absorbed per cu. in. 

(d) Whiskey barrel filled with clear water. Electrodes were horizontal 
circular iron plates I 3 / thick. Plates 26f" apart, P. D. of 486 volts gave 
current of 2.6 amperes. With plates I" apart, P. D. of 228 volts gave 
35.5 amperes at the end of one hour. When temperature of the water had 
reached 175° F., much gas was given off. Current density .12 amp. per 
sq. in., and watts absorbed 30.5 per cu. in. 

With large current density and direct current there is much decompo- 
sition of the electrodes with either clear or salt water. Horizontal elec- 
trodes are not to be recommended unless a large number of holes are drilled 
through the top plate to allow escape of gas. It is seldom necessary to 
use stronger solution than 2 or 3 per cent of salt, and in adding salt to the 
rheostat it is best to dissolve it thoroughly in a separate vessel and then 
add to the liquid as needed. Liquid rheostats seem to be more satisfac- 
tory for use in connection with alternating currents than with direct, as 
no decomposition of electrodes takes place and a given cross section of 
liquid seems to possess a greater current-carrying capacity. 

Merrill in American Electrician, December, 1897, gives results of experi- 
ments on small rheostats with about 20 amperes of current. 

Results are based upon a volume of solution 1 ft. long and 1 sq. ft. cross 
section. 



34 



SYMBOLS, UNITS, INSTRUMENTS. 



Water and Dilute Sulphuric Acid. Water and Common Table Salt- 



Per Cent Acid 


Resistance in 


Per Cent 


Resistance in 


by Weight. 


Ohms. 


Salt 


Ohms. 


.174 


4.12 


by Weight. 




.435 


1.75 


.23 


7.84 


.724 


1.10 


.46 


4.65 


.985 


.85 


.70 


3.12 






.93 


2.38 






1.16 


1.90 






1.39 


1.48 



Use of salt solution is cheap and convenient, but very untrustworthy 
for accurate work. 

For the sake of convenience in choosing proper sizes and lengths of 
iron wire for submerged rheostats, the accompanying table is given. The 
safe carrying capacities are the currents the wires can safely stand for a 
continuous run. If the apparatus is to be used for short periods, as in the 
case of a starting rheostat for a large motor, these values may be doubled. 

Water should be kept circulating through the barrel, enough water being 
used to keep the temperature below 200° F. 



Properties of Galvanized Iron Wire. 
Rheostats. 



for Submerged 



Wire 




Minimum Length in Feet for Safe carrying 




Num- 


Safe 


Capacity at Different Voltages. 






carrying 
Capacity; 




Feet per 
Ohm, hot. 


bers ; 
B. &S. 
Gauge. 










Amperes. 


100 


110 


220 


500 




20 


36 


22.8 


25 


50 


114 


8.5 


19 


42 


24.6 


27 


54 


123 


10.4 


18 


50 


26.4 


29 


58 


132 


13.5 


17 


60 


27.2 


30 


60 


136 


17.1 


16 


71 


29.0 


32 


64 


145 


21.5 


15 


88 


31.0 


34 


68 


155 


27.2 


14 


103 


32.7 


36 


72 


164 


34.2 


13 


122 


34.5 


38 


76 


173 


43.2 


12 


145 


36.4 


40 


80 


182 


54.3 


11 


173 


38.2 


42 


84 


191 


68.6 


10 


205 


41.0 


45 


90 


205 


86.5 


9 


245 


42.8 


47 


94 


214 


109.1 


8 


293 


46.9 


52 


103 


235 


137.5 


7 


347 


50.1 


55 


110 


250 


173.5 


6 


412 


53.1 


59 


117 


266 


219.0 


5 


489 


56.4 


62 


124 


282 


276.0 


4 


584 


59.5 


66 


131 


298 


348.0 



CONDENSERS. 



35 



CONDENSERS. 

If one terminal of a source of E.M.F. be connected to a conductor, 
and the other terminal be connected to another conductor adjacent to the 
first but insulated from it, it will be found that the two conductors exhibit 
a capacity for absorbing a charge of electricity that is somewhat analo- 
gous to the filling of a pipe with water before a pressure can be exerted. 
The charge will remain in the conductors after the removal of the source 
of supply. This capacity of the conductors to hold under a given E.M.F. a 
charge of electricity is governed by the amount of surface exposed, by 
the nearness of the surfaces to each other, by the quality of the insulating 
material, and by the degree of insulation from each other. If the ter- 
minals of a battery be connected through a battery and sensitive gal- 
vanometer to a long submarine cable conductor and to the earth, it will be 
found that a very considerable time will elapse before the needle will settle 
down to a steady point. This shows that the cable insulation has been 
filled with electricity; and it is common in so measuring the insulation 
resistance of a cable to assume a standard length of time, generally 
three minutes, during which time such electrification shall take place. 

A condenser is an arrangement of metallic plates and insulation so made 
up that it will take a standard charge of electricity at a certain pressure. 
The energy represented by the charge seems to be stored up in the insu- 
laxion between the conducting plates in the form of a stress. This property 
of insulating materials to take on a charge of static electricity is known as 
inductive capacity, and the following table shows the specific inductive 
capacities of different substances. 

Specific Inductive Capacity of Oases. 

(From Smithsonian Physical Tables.) 

With the exception of the results given by Ayrton and Perry, 

for which no temperature record has been found, the 

values are for 0° c. and 760 m.m. pressure. 



Gas. 



Air 

Air 

Air 

Carbon disulphide 

Carbon dioxide, C0 2 

Carbon dioxide, C0 2 

Carbon dioxide, C0 2 

Carbon monoxide, CO .... 
Carbon monoxide, CO .... 
Coal gas (illuminating) .... 

Hydrogen 

Hydrogen 

Hydrogen 

Nitrous oxide, N 2 

Nitrous oxide, N 2 

Sulphur dioxide 

Sulphur dioxide 

Vacuum 5 mm. pressure . . . 
Vacuum 0.001 mm. pressure about 

Vacuum 

Vacuum 



Sp. Ind. Cap. 



Vacuum 



1.0015 

1.00059 

1.00059 

1.0029 

1.0023 

1.00098 

1.00095 

1.00069 

1.00069 

1.0019 

1.0013 

1.00026 

1.00026 

1.00116 

1.00099 

1.0052 

1.00955 

1.0000 

1.0000 

1.0000 

1.0000 



Air=l. 



.0000 
.0000 
.0000 
.0023 
.0008 
.00039 
.00036 
1.00010 
1.00010 
1.0004 
0.9998 
0.99967 
0.99967 
1.00057 
1.00040 
1.0037 
1.00896 
0.9985 
0.94 
0.99941 
0.99941 



Authority. 



Ayrton and 
Klemencic. 
Boltzmann. 
Klemencic. 
Ayrton and 
Klemencic. 
Boltzmann. 
Klemencic. 
Boltzmann. 
Ayrton and 
Ayrton and 
Klemencic. 
Boltzmann. 
Klemencic. 
Boltzmann. 
Ayrton and 
Klemencic. 
Ayrton and 
Ayrton and 
Klemencic. 
Boltzmann. 



Perry. 
Perry. 



Perry. 
Perry. 



Perry. 

Perry. 
Perry. 



36 SYMBOLS, UNITS, INSTRUMENTS. 

Specific Inductive Capacity of Solids (Air Unity). 



Substance. 


Sp. Ind.Cap. 


Authority. 


Calcspar parallel to axis . . 


7.5 


Romich and Nowak. 


Calcspar perpendicular to axis 


7.7 


Romich and Nowak. 


Caoutchouc ....... 


. 2.12-2.34 


Schiller. 


Caoutchouc, vulcanized 






. 2.69-2.94 


Schiller. 


Celluvert, hard gray 






1.19 


Elsas. 


Celluvert, hard red . . 






1.44 


Elsas. 


Celluvert, hard black . . 






1.89 


Elsas. 


Celluvert, soft red . . 






2.66 


Elsas. 


Ebonite 








2.08 


Rosetti. 


Ebonite . . 








, 






3.15-3.48 


Boltzmann. - 


Ebonite . . 














2.21-2.76 


Schiller. 


Ebonite . . 








. 






2.72 


Winkelmann. 


Ebonite . . 














2.56 


Wullner. 


Ebonite . . 








. 






2.86 


Elsas. 


Ebonite . . 








• 






1.9 


Thomson (from Hertz's vi- 
brations). 


Fluor spar . 














6.7 


Romich and Nowak. 


Fluor spar . 














6.8 


Curie. 


Glass,* density 2.5 to 4.5 






5-10 


Various. 


Double extra dense flint, den 

sity 4.5 
Dense flint, density 3.66 . . 


9.90 


Hopkinson. 


7.38 


Hopkinson. 


Light flint, density 3.20 . 




6.70 


Hopkinson. 


Very light flint, density 2.8* 


■ 


6.61 


Hopkinson. 


Hard crown, density 2.485 




6.96 


Hopkinson. 


Plate, density . . . 




8.45 


Hopkinson. 


Mirror 








5.8-6.34 


Schiller. 


Mirror . . . 














6.46-7.57 


Winkelmann. 


Mirror . . . 














6.88 


Donle. 


Mirror . . . 














6.44-7.46 


Elsas. 


Plate . . . 














3.31-4.12 


Schiller. 


Plate . . . 














7.5 


Romich and Nowak. 


Plate . . . 














6.10 


Wullner. 


Guttapercha 














3.3-4.9 


Submarine cable data. 


Gypsum . . 














6.33 


Curie. 


Mica . . . 














6.64 


Klemencic. 


Mica . . . 














8.00 


Curie. 


Mica . . . 














7.98 


Bouty. 


Mica . . . 














5.66-5.97 


Elsas. 


Mica . . . 














4.6 


Romich and Nowak. 


Paper, dry . 














1.25-1.75 


Abbott. 


Paraffin . . 














2.32 


Boltzmann. 


Paraffin . . 














1.98 


Gibson and Barclay. 


Paraffin . . 














2.29 


Hopkinson. 


Paraffin, quickly cooled trans 


- 1.68-1.92 


Schiller. | 


lucent. 






Paraffin, slowly cooled white 


1.85-2.47 


Schiller. 


Paraffin 


2.18 


Winkelmann. 


Paraffin 


1.96-2.29 


Donle, Wullner. 


Paraffin fluid, pasty .... 


1.98-2.08 


Arons and Rubens. 


Paraffin, solid 
















1.95 


Arons and Rubens. 



* The values here quoted apply when the duration of charge lies between 
0.25 and 0.00005 of a second. J. J. Thomson has obtained the value 2.7 
when the duration of the charge is about 2 V X 10 6 of a second; and this is 
confirmed by Blondlot, who obtained for a similar duration 2.8. 

t The lower values were obtained by electric oscillations of duration of 
charge about 0.00006 second. The larger values were obtained when 
duration of charge was about 0.02 second. 



CONDENSERS. 



37 



Specific Inductive Capacity of Solids (Air Unity). — Cont. 



Substance. 


Sp. Ind. Cap. 


Authority. 


Porcelain 


4.38 


Curie. 


Quartz, along the optic axis 




4.55 


Curie. 


Quartz, transverse .... 




4.49 


Curie. 


Resin 












2.48-2.57 


Boltzmann. 


Rock salt . 


















18.0 


Hopkinson. 


Rock salt . 


















5.85 


Curie. 


Selenium 


















10.2 


Romich and Nowak. 


Shellac . . 


















3.10 


Winkelmann. 


Shellac . . 


















3.67 


Donle. 


Shellac . . 


















2.95-3.73 


Wullner. 


Spermaceti 


















2.18 


Rosetti. 


Spermaceti 


















2.25 


Felici. 


Sulphur . . 


















3.84-3.90 


Boltzmann. 


Sulphur . . 


















2.88-3.21 


Wullner. 


Sulphur . . 


















2.24 


J. J. Thomson. 


Sulphur . . 


















2.94 


Blondlot. 


Sulphur . . . 


















2.56 


Trouton and Lilly. 



Specific Inductive Capacity of liquids. 



Substance. 



Alcohols: 

Amyl 

Ethyl 

Methyl 

Propyl 

Anilin 

Benzene 

Benzene average about . . . 

Benzene at 5° C 

Benzene at 15° C 

Benzene at 25° C 

Benzene at 40° C 

Hexane, between 11° and 13° C. 
Octane, between 13° .5-14° C. 
Decane, between 13° .5-14° .2 C. 
Amylene, between 15° -16° .2 C. 
Octylene, between 11° .5-13' 

.6C. 
Decylene, between 16° .7 C. 
Oils: 

Arachid 

Castor 

Colza , 

Lemon 

Neatsfoot 

Olive 

Petroleum 

Petroleum ether .... 

Rape-seed 

Sesame 

Sperm 

Turpentine 

Vaseline , 

Ozokerite , 

Toluene 

Xylene 



Sp. Ind. Cap 



15-15.9 

24-27 

32.65 

22.8 

7.5 

1.93-2.45 

2.3 

2.1898 
2 . 1534 
2.1279 
2.1103 
1.859 
1.934 
1.966 
2.201 
2.175 

2.236 

3.17 
4.6-4.8 

3.07-3.14 
2.25 
3.07 

3.08-3.16 

2.02-2.19 

1.92 

2.2-3.0 

3.17 

3.02-3.09 

2.15-2.28 

2.17 

2.13 

2.2-2.4 

2.3-2.6 



Authority. 



Cohn and Arons; Tereschin. 

Various. 

Tereschin. 

Tereschin. 

Tereschin. 

Various. 

Negreano. 
Negreano. 
Negreano. 
Negreano. 
Landholt and Jahn. 
Landholt and Jahn. 
Landholt and Jahn. 
Landholt and Jahn. 
Landholt and Jahn. 

Landholt and Jahn. 

Hopkinson. 
Various. 
Hopkinson. 
Tomaszewski. 
Hopkinson. 

Arons and Rubens; Hopkin- 
son. 
Various. 
Hopkinson. 
Various. 
Hopkinson. 
Hopkinson; Rosa. 
Various. 
Fuchs. 
Hopkinson 
Various. 
Various. 



38 SYMBOLS, UNITS, INSTRUMENTS. 

Specific Inductive Capacity. — Definition: The specific inductive 
capacity of a substance is the ratio of the capacity of a condenser when its 
plates are separated by this substance to the capacity of the same con- 
denser when its plates are separated by air. Therefore while the capacity 
of a condenser is rated as compared with a similar one made up with air 
insulation it is possible to get a greater capacity in the same space by the 
use of some substance other than air. If it take k coulombs of electricity 
to produce a P. D. of one volt between the terminals of an air condenser, 
then if the same condenser be insulated by some other substance it will 
take k X the specific inductive capacity of the substance with which it 
is now insulated to produce a P. D. of one volt. The foregoing are tables 
of specific inductive capacities taken from "Smithsonian Tables." 

The specific inductive capacity of paper cables varies from 3 to 4, ac- 
cording to the type of paper and mixture adopted. The inductive capacity 
of paper is about 2; that of rosin 2 to 3, according to its origin; and mix- 
tures of rosin, oil, paraffin, ozokerite, and other materials have a capacity 
of 3 to 4, or even more. For example, lubricating oil 55 parts, rosin 560, 
paraffin 224, ozokerite 160, has a standard inductive capacity of 3.6; oxidized 
linseed oil 90, rosin 370, Arkangel pitch 70, have 4.4; Arkangel pitch itself 
has 5.9; a mixture with Gallipot, instead of rosin — for example, Gallipot 
600, Arkangel pitch 110, and linseed oil 130 — has 4.8; a mixture of lubri- 
cating oil 9, rosin 52, black ozokerite 23, white ozokerite 16, has only 3.55. 

The unit of capacity is the international farad, which is defined as the 
capacity of a condenser which requires one coulomb (1 ampere for 1 second) 
to raise its potential from zero to one volt. 




Figs. 29 and 30. Standard Condensers. 

As the farad is far larger than ever is met in practice, the practical unit 
is taken as one-millionth farad or the micro-farad. 

The commercial standard most in use is the § micro-farad, although 
adjustable condensers are often used, arranged so as to combine into many 
micro-farads or fractions of the same. Fig. 29 shows the ordinary £ micro- 
farad condenser, and Fig. 30 one that is adjustable for different values. 
Diagram 31 shows an outline of the connections inside an adjustable con- 
denser. The ordinary commercial condenser is most usually made up of 
sheets of tin foil separated from each other by some insulator such as 
paraffined paper or mica. Every alternate sheet of foil is connected to a 
common terminal. As the capacity of a condenser depends upon the near- 
ness of the conductors to each other, and upon the area of the same, the 
insulating material is made as thin as possible, and still be safe from leakage 
or puncture. Many sheets of foil are joined together as described to make 
up the area. A condenser of 1 mfd. capacity contains about 3600 sq. in. of 
tin foil. In adjustable condenser, the sheets are separated into bundles, 



CONDENSERS. 



39 




Fig. 31. 




Fig. 32. Modified Mascart Electrometer. 



40 



SYMBOLS, UNITS, INSTRUMENTS. 



and arranged so that any of them can be plugged in or out to add to or 
lessen the total capacity. If connected in multiple as shown, or if the 
positive side of one condenser be connected to the negative side of another, 
or a number of them are thus added together, then the condensers are said 
to be arranged in "cascade" or in series. This is seldom done unless it be 
to obtain greater variation in capacity. 

Electrometer. — Another instrument used where the measurement of 
electrostatic capacities or potentials is common, is the electrometer. A type 

of electrometer commonly 
used is the quadrant electrom- 
eter, for which we are in- 
debted to Lord Kelvin. The 
needle is a thin, flat piece of 
aluminium suspended in a 
horizontal position by a thin 
metallic wire, in close prox- 
imity to four quadrants of thin 
sheet brass, that are supported 
on insulators without touch- 
ing each other. Opposite 
quadrants are connected by 
fine wires. A charge of elec- 
tricity is given the needle by 
connecting the suspension 
filament with a Leyden jar 
or other condenser. 

If the needle be charged 
positively it will be attracted 
by a negative charge and re- 
pelled by a positive charge. 
If, therefore, there be a dif- 
ference of potential between 
the pairs of quadrants, the 
needle will be deflected from 
zero. The usual mirror, 
scale, and lamp are used 
with this instrument, as in 
= the case of the reflecting 
galvanometer. A form is 
shown in Fig. 32. 

Electrostatic Volt- 
meter. 

Fig. 33. Kelvin's Electrostatic Voltmeter. A modification of the elec- 
trometer, used for indicat- 
ing high, and in some cases low, alternating current potentials is the elec- 
trostatic voltmeter of Lord Kelvin. It is constructed on the principle 
of an air condenser. 

In the high potential instrument, Fig. 33, the needle is made of a thin 
aluminium plate suspended vertically on delicate knife-edges, with a pointer 
extending from the upper part to a scale. 

On either side of the needle, and parallel to its face, are placed two 
quadrant plates metallically connected and serving as one terminal of the 
circuit to be measured, while the needle serves as the other and opposite 
terminal. Any electrical potential difference between the needle and the 
plates will deflect the needle out of its neutral position. Calibrated weights 
can be hung on the bottom of the needle to change the value of the scale 
indications. 

VOI.TIIETERS. 

These are indicating instruments which show the electromotive force 
impressed upon their terminals. They are, in nearly all cases, calibrated 
galvanometers of constant high resistance. When connected across the 
terminals of any source of electromotive force, currents will flow through 
them which are directly proportional to the impressed voltages. A pointer 
connected to the moving element moves over a scale which is empirically 
graduated to show the impressed voltage. The resistance of commercial 




CONDENSERS. 41 

voltmeters in ohms varies from 10 to 150 times the full scale reading in 
volts; thus, a voltmeter of Weston's make having a range of 150 volts may 
have a resistance of from 15000 to 325,000 ohms. The resistance should be 
wound non-inductively and of a wire possessing a negligible temperature 
coefficient. The controlling or directive forces to bring the pointer back to 
zero are generally obtained from springs or gravity and occasionally from 
magnets. 

There are several types of voltmeters in commercial use, those devel- 
oped by Edward Weston being perhaps the best known. For direct- 
current measurements in either switchboard or portable forms the moving 
coil type constructed on the general principle of the d' Arson val galvanom- 
eter with pivoted coil is most frequently used. They can be constructed 
so as to have high resistances and perfect damping and are but little affected 
by external fields, especially if shielded with iron casing, as is often done 
with switchboard instruments. 

For alternating-current measurements the electromagnetic or soft iron 
instrument is very commonly used for switchboard work. In this instru- 
ment a mass of soft iron is so placed in a solenoid that it will be drawn 
from the center to the edge of the solenoid, or drawn into the solenoid from 
an outside point. These instruments are correct only for the particular 
frequency for which they were calibrated and corrections should be made 
for any change of frequency. When properly calibrated they may be used 
on direct-current circuits. 

Portable voltmeters for alternating-current measurements frequently 
employ a system based upon the electro-dynamometer. This instrument 
has the advantage of being independent of frequency variations or wave 
form. It can also be used for direct-current measurements if correction 
for external fields is made. 

In addition to the above types, voltmeters are constructed on the hot 
wire principle in which the passage of the current causes heating and a 
consequent expansion of the wire through which it passes. The expansion 
of the wire is taken up by a spring which causes a pointer to move across a 
graduated scale. 

Ammeters. 

The scale of a voltmeter may be graduated and marked so as to indicate 
the value of the currents passing through it instead of the volts impressed 
upon its terminals. It will then be an ammeter. To be of value its 
resistance must be small. Many ammeters consist of moving-coil milli- 
voltmeters connected to the terminals of shunts through which the 
currents to be measured are passed. The shunts are made of a high resist- 
ance low temperature coefficient alloy and, since the resistance remains 
constant, the drop in potential between its terminals will be proportionate 
to the current flowing through it. The scales are graduated so as to indi- 
cate the currents passing through the shunts. The shunt type of instru- 
ment is particularly applicable to switchboards, but is adapted for direct- 
current measurements only. 

For alternating-current measurements the electromagnetic system is 
generally employed, the total current to be measured passing through a 
low-resistance solenoid, or the current flowing through the ammeter may be 
reduced by inserting the primary of a series transformer in the main circuit 
and connecting the ammeter across the terminals of the secondary. Since 
the ratio of current in the primary to that in the secondary is constant, the 
ammeter may be calibrated in terms of the primary, but need have only the 
small secondary current flowing through it. 

Soft Iron Instruments. — If a piece of soft iron be placed in a mag- 
netic field it becomes itself magnetic. This fact is utilized in the so-called 
"soft iron" instruments in which the movable system consists of a soft 
iron needle pivoted within a coil and normally placed oblique to the direc- 
tions of its magnetic field. When a current passes through the coil the 
needle tends to assume a position parallel to the lines of force, and being 
controlled by a spring or other controlling force, the deflection is a measure 
of the current passing. 

This type of instrument is used to some extent for switchboard work, 
but cannot be used in measurements where great accuracy is required on 
account of magnetic lag in the iron. 



42 



SYMBOLS, UNITS, INSTRUMENTS. 



The Electro-Dynamometer. 

If currents be sent through two coils of wire, which are capable of move- 
ment as regards each other, they will tend to place themselves in such a 
position as to bring the lines of force of their magnetic fields parallel to each 
other and in the same direction. The Siemen's electro-dynamometer acts 
according to this principle. 

Fig. 34 below shows the form most used. It consists of a fixed coil usually 
having two divisions, — one of a few turns of heavy wire for heavy currents 

and another of many turns of finer 
wire for smaller currents. Out- 
side of this fixed coil, and at right 
angles thereto, is suspended a mov- 
able coil of few turns. A carefully 
wound helical spring joins the mov- 
able coil to a torsion screw above 
the dial. A pointer on this torsion 
screw shows on the dial the degrees 
of angle through which it may be 
twisted. The lower ends of the 
movable coil dip into mercury cups 
to make connection with the fixed 
coil. If current flows through the 
two coils in series, the movable coil 
is turned from its position at right 
angles with the fixed coil and tries 
to arrange itself in the same plane 
as the latter, according to above 
law. 

The torsion screw is then turned 
in the opposite direction until the 
force of the spring overcomes the 
electrodynamic action of the coils, 
and the movable coil is brought to 
zero. 

If A be a constant depending 
upon the character of the torsion 
spring, I be the current, and d be 
the angle of deflection of the torsion 
screw to return the movable coil to 
zero, then 

I = A\ / d. 

The electro-dynamometer is suited 
to measure alternating currents of 
ordinary frequencies, also direct 
currents. 

Wattmeter. — If the movable coil of the electro-dynamometer be of 
very fine wire, and have a coil of very high and non-inductive resistance 
in series with it, and if the fixed coil be of heavy wire, then the instrument 
may be used for measuring the work of a circuit in watts, by connecting 
the fixed coil in series with the circuit under test, and the movable coil 
across the terminals of the circuit. In this case, if the voltage current be t, 
and the series current in the fixed coil be i 2 . tnen tne power equals Ki t i 2 , 
where K is a constant of the instrument. The two currents are supposed 
to be in phase with each other. If the movable coil be not brought back 
to zero, but a pointer connected with it be permitted to move over a grad- 
uated scale, the scale can be calibrated directly in watts. 

Weston's well-known wattmeter is constructed substantially on this 
principle. 

In order that a wattmeter (electro-dynamometer) may be reliable for 
measuring alternate-current power, it is needful that the fine-wire circuit, 
which is to be connected as a shunt to the apparatus under measurement, 
should have as little self-induction as possible in proportion to its resis- 
tance. The latter may be increased by adding auxiliary non-inductive 




Fig. 34. Siemen's Electro- 
Dynamometer. 



CONDENSERS. 43 

resistances. The instrument must itself be so constructed that there shall 
be no eddy currents set up by either circuit in the frames, supports, or 
case; otherwise the indications will be false. 

Kelvin's Composite Electric Balance. 

This instrument is employed to a considerable extent as a standard for 
comparison of instruments for both direct and alternating currents, although 
for direct-current work it has been almost entirely superseded by the direct 
reading laboratory standard instrument, which is more sensitive, and 
equally accurate throughout the scale, as is not the case with the Kelvin 
balance, since its indications vary as the square of the current. It can be 
used as voltmeter, ampere meter, or wattmeter. The principle of its action 
is similar to that of the electro-dynamometer. The attraction and repul- 
sion between the stationary and movable coils is balanced by the attrac- 
tion of gravity on a sliding weight connected with the movable coils. 



< 




Fig. 35. Kelvin's Standard Composite Balance. 

Above is a cut of the instrument in its latest form, and the diagram fol- 
lowing shows the theory on which the instrument works. 

In both cut and diagram the same letters indicate the same parts: a 
and b are two coils of silk-covered copper wire placed one above the other 
as shown with their planes horizontal, and the whole being mounted on 
a slab of slate which is supported on leveling screws. 

Two coils c and d, of similar wire, are made in rings that are secured to the 
ends of a balance beam B, which is suspended at its center by two flat liga- 
ments of fine copper wire. 

When for use with direct currents two other coils, g and h, made of 
strip copper, and of cross section heavy enough to carry large currents, say 
500 amperes, are secured to the base plate at the left in the same relative 
position as are the coils a and b at the right. When the instrument is to be 
used in the measurement of alternating currents the coils g and h are made 
of two or three turns of a stranded copper conductor, each wire of which is 
insulated; and, to as far as possible annul the effects of induction, the strand 
is given one turn or twist for each turn around the coil. 

The coils c and d of the balance are suspended equidistant between the 
right and left pairs of coils with planes parallel to their planes and centers 
coinciding with their centers. 

To Set the Balance. — Level the instrument with the adjustable legs, turn 
the stop screws back out of contact with the cross trunnions and front plate 
of the beam, leaving it free. 

To Use as Voltmeter or Centi- ampere Meter. — Connect the instrument to 
the circuit or source of E.M.F. through a non-inductive resistance R, as shown 
in the following diagram, the resistance terminal to T and the other ter- 
minal to T\\ throw the switch H to the right to the "volt" contact. 

One of the weights v u\, v W2, v w$, is then used on the scale beam, and a 
is balance obtained. The current flowing in the instrument is then calcu- 



44 



SYMBOLS, UNITS, INSTRUMENTS. 



Iated by a comparison of the scale-reading with the certificate accompanying 
the instrument. The volts E.M.F. at the terminals are calculated from the 
current flowing and the resistance in circuit, including the non-inductive 
resistance used, by Ohm's law, v = IR. 

To Use as Hekto-ampere Meter. — Turn the switch H to " watts," insert 
the thick wire coils in circuit with the current in such a way that the right- 
hand end of the beam rises. Use the " sledge " alone or the weight marked 
w.w. 

Terminals E and E t are then introduced into the circuit, and a measured 
current passed through the suspended coils g and h ; and the constants given 
in the certificate for the balance used in this way are calculated on the as- 
sumption that this current is .25 ampere. Any other current may be used, 
say I ampere, then the constant becomes / ■*■ .25 or 4f. 

The current flowing in the suspended coils g and h may be measured by 
the instrument itself, arranged for the measurement of volts. To do this, 
first measure the current produced by the applied E.M.F. through the coils 




— wwwwv— -* y 

.R 

Fig. 36. Diagram of the Kelvin Composite Balance. 



of the instrument and the external resistance, then turn the switch H to 
11 watt," and introduce into the circuit a resistance equal to that of the fixed 
coils. 

To Use as a Wattmeter. — Insert the thick wire coils in the main circuit ; 
then join one end of the non-inductive resistance R to one terminal of the 
fine wire coils, and the other end of R to one of the leads ; the other termi- 
nal of the fine wire coils is connected to the other lead. The current flowing 
and the E.M.F. may now be determined by the methods described above. 
The watts can then be calculated from the E.M.F. of the leads, and the 
current flowing in the thick wire coils by the formula, 

P w =VI = i IR, 

Where i = current in the suspended coil circuit. 
/ — current in the thick wire coils. 
R z=z resistance in the circuit. 

When working with alternating currents the non-inductive resistance R 
must be large enough to prevent any difference of phase of the current 
flowing in the fine wire coils and the E.M.F. of the circuit. 



DOUBLED SQUARE ROOTS. 



45 



Table of Doubled Square Roots for Xorrt Kelvin's Stand- 
ard Electric Balances. 








100 


200 


300 


400 


500 


600 


700 


800 


900 







0.000 


20.00 


28.28 


34.64 


40.00 


44.72 


48.99 


52.92 


56.57 


60.00 





1 


2.000 


20.10 


28.35 


34.70 


40.05 


44.77 


49.03 


52.95 


56.60 


60.03 


1 


2 


2.828 


20.20 


28.43 


34.76 


40.10 


44.81 


49.07 


52.99 


56.64 


60.07 


2 


3 


3.464 


20.30 


28.50 


34.81 


40.15 


44.86 


49.11 


53.03 


56.67 


60.10 


3 


4 


4.000 


20.40 


28.57 


34.87 


40.20 


44.90 


49.15 


53.07 


56.71 


G0.13 


4 


5 


4.472 


20.49 


28.64 


34.93 


40.25 


44.94 


49.19 


53.10 


56.75 


60.17 


5 


6 


4.899 


20.59 


28.71 


34.99 


40.30 


44.99 


49,23 


53.14 


56.78 


60.20 


6 


7 


5.292 


20.69 


28.77 


35.04 40.35 


45.03 


49.27 


53.18 


56.82 


60.23 


7 


8 


5.657 


20.78 


28.84 


35.10 


40.40 


45.08 


49.32 


53.22 


56.85 


60.27 


8 


9 


6.000 


20.88 


28.91 


35.16 


40.45 


45.12 


49.36 


53.25 


56.89 


60.30 


9 


10 


6.325 


20.98 


28.98 


35.21 


40.50 


45.17 
l 


49.40 


53.29 


56.92 


60.33 


10 


11 


6.633 


21.07 


29.05 


35.27 


40.55 


45.21 


49.44 


53.33 


56.96 


60.37 


11 


12 


6.928 


21.17 


29.12 


35.33 


40.60 


45.25 


49.48 


53.37 


56.99 


60.40 


12 


13 


7.211 


21.26 


29.19 


35.38 


40.64 


45.30 


49.52 


53.40 


57.03 


60.43 


13 


14 


7.483 


21.35 


29.26 


35.44 


40.69 


45.34 


49.56 


53.44 


57.06 


60.46 


14 


15 


7.746 


21.45 


29.33 


35.50 


40.74 


45.39 


49.60 


53.48 


57.10 


60.50 


15 


16 


8.000 


21.54 


29.39 


35.55 


40.79 


45.43 


49.64 


53.52 


57.13 


60.53 


16 


17 


8.246 


21.63 


29.46 


35.61 


40.84 


45.48 


49.68 


53.55 


57.17 


60.56 


17 


18 


8.485 


21.73 


29.53 


35.67 


40.89 


45.52 


49.72 


53.59 


57.20 


60.60 


18 


19 


8.718 


21.82 


29.60 


35.72 


40.94 


45.56 


49.76 


53.63 


57.24 


60.63 


19 


20 


8.944 


21.91 


29.66 


35.78 


40.99 


45.61 


49.80 


53.67 


57.27 


60.66 


20 


21 


9.165 


22.00 


29.73 


35.83 


41.04 


45.65 


49.84 


53.70 


57.31 


60.70 


21 


22 


9.381 


22.09 


29.80 


35.89 


41.09 


45.69 


49.88 


53.74 


57.34 


60.73 


22 


23 


9.592 


22.18 


29.87 


35.94 


41.13 


45.74 


49.92 


53.78 


57.38 


60.76 


23 


24 


9.798 


22.27 


29.93 


36.00 


41.18 


45.78 


49.96 


53.81 


57.41 


60.79 


24 


25 


10.000 


22.36 


30.00 


36.06 


41.23 


45.83 


50.00 


53.85 


57.45 


60.83 


25 


26 


10.198 


22.45 


30.07 


36.11 


41.28 


45.87 


50.04 


53.89 


57.48 


60.86 


26 


27 


10.392 


22.54 


30.13 


36.17 


41.33 


45.91 


50.08 


53.93 


57.52 


60.89 


27 


28 


10.583 


22.63 


30.20 


36.22 


41.38 


45.96 


50.12 


53.96 


57.55 


60.93 


28 


29 


10.770 


22.72 


30.27 


36.28 


41.42 


46.00 


50.16 


54.00 


57.58 


60.96 


29 


30 


10.954 


22.80 


30.33 


36.33 


41.47 


46.04 


50.20 


54.04 


57.62 


60.99 


30 


31 


11.136 


22.89 


30.40 


36.39 


41.52 


46.09 


50.24 


54.07 


57.65 


61.02 


31 


32 


11.314 


22.98 


30.46 


36.44 


41.57 


46.13 


50.28 


54.11 


57.69 


61.06 


32 


33 


11.489 


23.07 


30.53 


36.50 


41.62 


46.17 


50.32 


54.15 


57.72 


61.09 


33 


34 


11.662 


23.15 


30.59 


36.55 


41.67 


46.22 


5056 


54.18 


57.76 


61.12 


34 


35 


11.832 


23.24 


30.66 


36.61 


41.71 


46.26 


50.40 


54.22 


57.79 


61.16 


35 


36 


12.000 


23.32 


30.72 


36.66 


41.76 


46.30 


50.44 


54.26 


57.83 


61.19 


36 


37 


12.166 


23.41 


30.79 


36.72 


41.81 


46.35 


50.48 


54.30 


57.86 


61.22 


37 


38 


12.329 


23.49 


30.85 


36.77 


41.86 


46.39 


50.52 


54.33 


57.90 


61.25 


38 


39 


12.490 


23.58 


30.92 


36.82 


41.90 


46.43 


50.56 


54.37 


57.93 


61.29 


39 


40 


12.649 


23.66 


30.98 


36.88 


41.95 


46.48 


50.60 


54.41 


57.97 


61.32 


40 


41 


12.806 


23.75 


31.05 


36.93 


42.00 


46.52 


50.64 


54.44 


58.00 


61.35 


41 


42 


12.961 


23.83 


31.11 


36.99 


42.05 


46.56 


50.68 


54.48 


58.03 


61.38 


42 


43 


13.115 


23.92 


31.18 


37.04 


42.10 


46.60 


50.71 


54.52 


58.07 


61.42 


43 


44 


13.266 


24.00 


31.24 


37.09 


42.14 


46.65 


50.75 


54.55 


58.10 


61.45 


44 


45 


13.416 


24.08 


31.30 


37.15 


42.19 


46.69 


50.79 


54.59 


58.14 


61.48 


45 


46 


13.565 


24.17 


31.37 


37.20 


42.24 


46.73 


50.83 


54.63 


58.17 


61.51 


46 


47 


13.711 


24.25 


31.43 


37.26 


42.28 


46.78 


50.87 


54.66 


58.21 


61.55 


47 


48 


13.856 


24.33 


31.50 


37.31 


42.33 


46.82 


50.91 


54.70 


58.24 


61.58 


48 


49 


14.000 


24.41 


31.56 


37.36 


42.38 


46.86 


50.95 


54.74 


58.28 


61.61 


49 


50 


14.142 


24.49 


31.62 


37.42 


42.43 


46.90 


50.99 54.77 


58.31 


61.64 


50 



46 



SYMBOLS, UNITS, INSTRUMENTS. 








100 


200 


300 


400 


500 


600 


700 


800 1 900 




51 


14.283 


24.58 


31.69 


37.47 


42.47 


46.95 


51.03 


54.81 


58.34 


61.68 


51 


52 


14.422 


24.66 


31.75 


37.52 


42.52 


46.99 


51.07 


54.85 


58.38 


61.71 


52 


53 


14.560 


24.74 


31.81 


37.58 


42.57 


47.03 


51.11 


54.88 


58.41 


61.74 


53 


54 


14.697 


24.82 


31.87 


37.63 


42.61 


47.07 


51.15 


54.92 


58.45 


61.77 


54 


55 


14.832 


24.90 


31.94 


37.68 


42.66 


47.12 


51.19 


54.95 


58.48 


61.81 
61.84 


55 


56 


14.967 


24.98 


32.00 


37.74 


42.71 


47.16 


51.22 


54.99 


58.51 


56 


57 


15.100 


25.06 


32.06 


37.79 


42.76 


47.20 


51.26 


55.03 


58.55 


61.87 


57 


58 


15.232 


25.14 


32.12 


37.84 


42.80 


47.24 


51.30 


55.06 


58.58 


61.90 


58 


59 


15.362 


25.22 


32.19 


37.89 


42.85 


47.29 


51.34 


55.10 


58.62 


61.94 


59 


60 


15.492 


25.30 


32.25 


37.95 


42.90 


47.33 


51.38 | 55.14 


58.65 


61.97 


60 


61 


15.620 


25.38 


32.31 


38.00 


42.94 


47.37 


51.42 


55.17 


58.69 


62.00 


61 


62 


15.748 


25.46 


32.37 


38.05 


42.99 


47.41 


51.46 


55.21 


58.72 


62.03 


62 


63 


15.875 


25.53 


32.43 


38.11 


43.03 


47.46 


51.50 


55.24 


58.75 


62.06 


63 


64 


16.000 


25.61 


32.50 


38.16 


43.08 


47.50 


51.54 


55.28 


58.79 


62.10 


64 


65 


16.125 


25.69 


32.56 


38.21 


43.13 


47.54 


51.58 


55.32 


58.82 


62.13 


65 


66 


16.248 


25.77 


32.62 


38.26 


43.17 


47.58 


51.61 


55.35 


58.86 


62.16 


66 


67 


16.371 


25.85 


32.68 


38.31 


43.22 


47.62 


51.65 


55.39 


58.89 


62.19 


67 


68 


16.492 


25.92 


32.74 


38.37 


43.27 


47.67 


51.69 


55.43 


58.92 


62.23 


68 


69 


16.613 


26.00 


32.80 


38.42 


43.31 


47.71 


51.73 


55.46 


58.96 


62.26 


69 


70 


16.733 


26.08 


32.86 


38.47 


43.36 


47.75 


51.77 


55.50 


58.99 


62.29 


70 


71 


16.852 


26.15 


32.92 


38.52 


43.41 


47.79 


51.81 


55.53 


59.03 


62.32 


71 


19 


16.971 


26.23 


32.98 


38.57 


43.45 


47.83 


51.85 


55.57 


59.06 


62.35 


72 


73 


17.088 


26.31 


33.05 


38.63 


43.50 


47.87 


51.88 


55.61 


59.09 


62.39 


73 


74 


17.205 


26.38 


33.11 


38.68 


43.54 


47.92 


51.92 


55.64 


59.13 


62.42 


74 


75 


17.321 


26.46 


33.17 


38.73 


43.59 


47.96 


51.96 


55.68 


59.16 


62.45 


75 


76 


17.436 


26.53 


33.23 


38.78 


43.63 


48.00 


52.00 


55.71 


59.19 


62.48 


76 


77 


17.550 


26.61 


33.29 


38.83 


43.68 


48.04 


52.04 


55.75 


59.23 


62.51 


77 


78 


17.664 


26.68 


33.35 


38.88 


43.73 


48.08 


52.08 


55.79 


59.26 


62.55 


78 


79 


17.776 


26.76 


33.41 


38.94 


43.77 


48.12 


52.12 


55.82 


59.30 


62.58 


79 


80 


17.889 


26.83 


33.47 


38.99 


43.82 


48.17 


52.15 


55.86 


59.33 


62.61 


80 


81 


18.000 


26.91 


33.53 


39.04 


43.86 


48.21 


52.19 


55.89 


59.36 


62.64 


81 


8?, 


18.111 


26.98 


33.59 


39.09 


43.91 


48.25 


52.23 


55.93 


59.40 


62.67 


82 


83 


18.221 


27.06 


33.65 


39.14 


43.95 


48.29 


52.27 


55.96 


59.43 


62.71 


83 


84 


18.330 


27.13 


33.70 


39.19 


44.00 


48.33 


52.31 


56.00 


59.46 


62.74 


84 


85 


18.439 


27.20 


33.76 


39.24 


44.05 


48.37 


52.35 


56.04 


59.50 


62.77 


85 


86 


18.547 


27.28 


33.82 


39.29 


44.09 


48.41 


52.38 


56 07 


59.53 


62.80 


86 


87 


18.655 


27.35 


33.88 


39.34 


44.14 


48.46 


52.42 


56.11 


59.57 


62.83 


87 


88 


18.762 


27.42 


33.94 


39.40 


44.18 


48.50 


52.46 


56.14 


59.60 


62.86 


88 


89 


18.868 


27.50 


34.00 


39.45 


44.23 


48.54 


52.50 


56.18 


59.63 


62.90 


89 


90 


18.974 


27.57 


34.06 


39.50 


44.27 


48.58 


52.54 


56.21 


59.67 


62.93 


90 


91 


19.079 


27.64 


34.12 


39.55 


44.32 


48.62 


52.57 


56.25 


59.70 


62.96 


91 


92 


T9.183 


27.71 


34.18 


39.60 


44.36 


48.66 


52.61 


56.28 


59.73 


62.99 


92 


93 


19.287 


27.78 


34.23 


39.65 


44.41 


48.70 


52.65 


56.32 


59.77 


63.02 


93 


94 


19.391 


27.86 


34.29 


39.70 


44.45 


48.74 


52.69 


56.36 


59.80 


63.06 


94 


95 


19.494 


27.93 


34.35 


39.75 


44.50 


48.79 


52.73 


56.39 


59.83 


63.09 


95 


96 


19.596 


28.00 


34.41 


39.80 


44.54 


48.83 


52.76 


56.43 


59.87 


63.12 


96 


97 


19.698 


28.07 


34.47 


39.85 


44.59 


48.87 


52.80 


56.46 


59.90 


63.15 


97 


98 


19.799 


28.14 


34.53 


39.90 


44.63 


48.91 


52.84 


56.50 


59.93 


63.18 


98 


99 


19.900 


28.21 


34.58 


39.95 


44.68 


48.95 


52.88 


56.53 


59.97 


63.21 


99 


100 


20.000 


28.28 


34.64 


40.00 


44.72 


48.99 


52.92 


56.57 


60.00 


63.25 1 100 



U_(7£J 



THE POTENTIOMETER. 47 

The Potentiometer. 

In its simplest form the potentiometer may be represented by the dia- 
gram, Fig. 37. 

A B is a resistance in which a constant current from the battery IF is 
maintained. The regulating resistance R is used to compensate for varia- 
tions in the E.M.F. or internal resistance of the battery IF. The con- 
stancy of the current in A B is checked by seeing that the drop in poten- 
tial between two points chosen in it is equal to the E.M.F. of a standard 
cell. The standard cell is introduced into the circuit M. E. MJ at E, and 
the regulating resistance R adjusted until the sensitive galvanometer G 
shows no deflection. Assuming A B to have a uniform resistance through- 
out its length, and the current in it to remain constant, it is obvious that 
any other voltage not greater than the drop between A and B can be 
measured by introducing it at E and shifting the points MM' until the 
galvanometer again comes to a balance. Further, a direct reading scale 
may be placed between A and B. For 

most potentiometer work the drop . il 

between A and B is made about 1.5 J A 

volts, as this is about the E.M.F. of aaa/vwwvww vv 

a standard Clark cell. That the instru- I m k m' 

ment may have a wide range and A 
make measurements to a sufficiently 
high degree of accuracy, it is neces- 
sary that it be possible to sub-divide 
this resistance, so as to read voltage p oy 

to at least the fifth decimal place. • 

Since the current must be kept constant the total resistance in the circuit 
must not be varied by raising the resistance between M and M'. 

Itang-e. — To meet general laboratory requirements the potentiometer 
must measure directly as high as 1.5 volts so that all kinds of standard 
cells may be compared with each other; and it must measure as low as 
.00001 volt so that reasonably low resistance standards may be used in 
measuring current. An example will make this point clear. To measure 
1000 amperes the current must flow through a standard low resistance 
and the drop in E.M.F. across its terminals be measured on the potentiom- 
eter. With a potentiometer reading only to .0001 volt the drop across 
the low resistance must be at least .1 volt in order that it may be read to 
an accuracy of T \j%. If 1000 amperes is the maximum current to be used 
on the particular low resistance it should be so designed as to give proper 
readings with a minimum current at least as low as 100 amperes. 100 
amperes must consequently give a drop of .1 volt, which fixes the resistance at 
.001 ohm. .001 ohm to carry 1000 amperes must be able to dissipate 1000 
watts, and in order to remain a standard it must do this without heating 
enough to vary the resistance outside of small limits. With a potentiometer 
reading to .00001 volt the same range of current can be handled on a resist- 
ance of .0001 ohm and can be measured to the same degree of accuracy. 
To carry 1000 amperes it will only have to dissipate 100 watts. To maintain 
the same degree of accuracy while a current is flowing it can consequently 
be made of a very much smaller size and with ^ the radiating surface. 

Methods of Using- the Standard Cell. — The standard cell is 
used to measure the current flowing through the potentiometer, which is 
done by making the drop in E.M.F. across a known resistance in the circuit 
equal to that of the standard cell. 

1st Method. — The standard cell maybe used as indicated in Fig. 38. 
The galvanometer is permanently in circuit with the points MM', and by 
means of the double-throw switch U the standard cell S, or an unknown 
E.M.F. E, may be thrown into the same circuit. If the resistance A B is 
provided with a scale by means of which it is sub-divided into, for example, 
15,000 equal parts, the points MM' may be set to a reading corresponding 
to the E.M.F. of the standard cell and the current from the battery 
W regulated by the resistance R until there is a balance, the standard cell 
being in circuit with the galvanometer and points MM'. There will then 
be such a current flowing that for any other position of the points MM', 
producing a balance with the unknown E.M.F. in circuit, the reading from 
the scale will be direct in volts. This method is open to the objection that 
it requires a resetting of the points MM' to make a check measurement 
of the current flowing. In making accurate measurements these check 



i 



48 



SYMBOLS, UNITS, INSTRUMENTS. 



measurements have to be made frequently and are especially inconvenient 
by this method when the points MM' are multiplied from two to four or 
five as they generally are. 

2d Method. — A method of measuring and checking the currents which 
avoids this objection is shown in Fig. 39. It is not necessary that the re- 
sistance which furnishes the drop, against which the E.M.F. of the standard 



OB 





Fig. 38. Fio. 39. 

cell is balanced, be between the points A B, which limit the motion of MM'. 
If placed at R» and properly chosen with reference to the E.M.F. of the 
standard cell and the resistance of the wire A B, the current which pro- 
duces a drop across it equal to the E.M.F. of the standard cell will make 
the scale of A B direct reading in volts. In this case the double-throw 
switch is arranged so as to thirow the galvanometer either into the circuit 
containing the standard cell and the resistance Rs, or into the circuit con- 
taining the points MM' and the unknown E.M.F. This method is, how- 
ever, open to a serious objection from the standpoint of accuracy, which 
is avoided by the first. To illustrate this by a numerical example, assume 
in both cases all the resistances adjusted to an accuracy of & of 1% and 
the error to be in such a direction as to produce the worst result. In the 
second method if the resistance R* were ^% high the current flowing 
through the potentiometer would be ■&% lower than it should be. If now 

the resistances oi A B were ^ % low this 
would introduce a second error of the 
same amount in the same direction 
and the resulting error in measurement 
would be 55%. In other words the 
measurement accuracy throughout the 
range of the potentiometer may be 
only half so good as the adjustment 
accuracy. In the first method, since 
the standard cell E.M.F. and the un- 
known E.M.F. are balanced against 
the drop across the same resistances 
in measuring an E.M.F. nearly equal 
to that of the standard cell, inaccura- 
cies in the resistance are the same in 
both cases and balance each other. 
Consequently by this method measurements are bound to be more 
accurate than the adjustment of the resistances. In a potentiometer 
arranged to be used with a Clark cell using the first method of applying 
the standard cell and with resistances adjusted to &% it can be shown by 
calculation that the maximum error in measurement will vary with the 
value of the E.M.F. under measurement. For E.M.F. of 1.5 volts this 
error will be less than .003%. For E.M.F. of 1.2 volts it will be about .01%. 
For E.M.F. of .8 volts it will be about .02%. For E.M.F. of .3 to .1 volts 
it will be .04%, and in no case will be larger than this. To sum up the con- 
trast in accuracy between the two methods: in the second the errors may 
be twice as great as the adjustment errors throughout the range, while in 
the first method they only become this large for .3 volt and under, and for 
higher voltages have increasing accuracy becoming equal to that of the 
adjustment at .8 volts and much better as they approach the E.M.F. of 
the standard cell; at exactly the E.M.F. of the standard cell the accuracy 
of comparison becomes independent of the accuracy of adjustment of the 
resistance. 




Fig. 40. 



POTENTIOMETER. 



49 



3d Method. — A third method combines with the accuracy of the first, the 
convenience of the second. It is illustrated in Fig. 40. The E.M.F. of the 
standard cell is balanced against the drop across a part of the potentiometer 
wire AB as in method No. 1, but the terminals of this resistance are found, not 
by setting the points MM', but they are permanently fixed, and the double-throw 
switch U throws the galvanometer into one circuit or the other as desired. 

The Brooks Deflection Potentiometer. 

While the potentiometer is very accurate, it is slow in working and can be 
used only with steady current or voltage. The deflection potentiometer, de- 
signed by H. B. Brooks of the National Bureau of Standards, combines in 
large measure the accuracy and reliability of the null potentiometer with the 
speed and convenience of portable deflection instruments. It consists of a 



< 




Fig. 40a. The Brooks' Deflection Potentiometer. 

one-dial potentiometer having a pivoted moving-coil galvanometer with 
calibrated scale. The deflection of the galvanometer gives the last few figures 
of the result, which are read from the slide wire in some forms of potentiometer. 
As the galvanometer is quick and dead beat, the value of a fluctuating current 
or voltage may be followed. The deflection potentiometer is intended as a 
standard instrument for central stations, instrument and meter factories, and 
other service requiring accuracy combined with speed. 



Description of Instrument. 

Figure 4 shows a plan of circuits of the Model 3 potentiometer, which has 
been designed for general measurements of current and voltage in laboratories 
whose requirements include a reasonable degree of accuracy combined with 
speed of working. 

The main dial has 30 steps of 5 ohms each. In series with it is a coil of 1.80 
ohms and a standard-cell dial of 10 steps of 0.01 ohm each. The Weston 
portable unsaturated standard cell only is used; it is balanced around the 
last two-thirds (100 ohms) of the mam dial, plus the 1.80-ohm coil and the 
standard-cell dial. Thus it is possible to use standard cells whose values are 
from 1.0180 to 1.0190 volts inclusive. This covers the range of variation of 
these unsaturated cells sufficiently well, as cells may be bought with the speci- 
fication that they shall fall within this range, and within several units of the 
lower end of the dial, to provide for the slight decrease of E.M.F. to be ex- 
pected in a period of years. The standard current through the main dial 
coils is thus 0.01 ampere; it is furnished by a storage cell. The series rheostat 
r 3 has a minimum value of 20.85 ohms, and increases by 15 steps of 0.1 ohm 
each. The shunt rheostat (r 6 ) has a minimum value of 88.9 ohms, and in- 
creases by 15 steps to a maximum of 123.4 ohms. A fine rheostat of 0.5 ohm 
in the battery circuit covers any step of the coarse rheostat, and has a com- 
pensating resistance of 0.3 ohm in the galvanometer circuit. The circuits 



50 



SYMBOLS, UNITS, INSTRUMENTS. 



are so designed that the compensating resistance (r 4 ) of the main dial repeats 
at 90, 95, . . . 150 the values for 80, 75, . . . 20; hence a number of ooils 
are saved by using cross connections. 

The galvanometer key has a protective resistance of 2,400 ohms, which is 
in circuit on the first contact and is cut out on full depression. The total 
resistance in the galvanometer circuit under working conditions is 60 ohms 
between the binding posts marked "Volt Box," which with 40 ohms resultant 




34.5-n- 

AAMAMr-AAA- 1 

88.9-n. 



mm^imM^mmM 




L-W\ — WA/WV 

20.85 a 15 x 0.1a. 

Fig. 40b. Plan of Circuit, Model 3 Brooks' Deflection Potentiometer. 

resistance in the volt box makes up the normal total of 100 ohms. The total 
resistance measured between the binding posts marked "Shunt" is 100 ohms 
when the circular plug rheostat near these posts is plugged at the extreme 
right, and is less than this by amounts of 0.1, 0.2, 0.5 .. . 40 ohms when the 
plug is placed in succession toward the left. This allows the total resistance 
to be kept 100 ohms when using shunts of the values just given, the resistance 
of the shunt being counted in the total. 



INSTRUMENTS A3TD METHODS I OR ni-TEII.niV 

ATIO Y OF WAVE FORM OF CURRENT AJJTD 

ELECTROMOTIVE FORCE. 

There are numerous methods of determining wave form, those used in the 
laboratory experiments commonly making use of the ballistic galvanometer. 
Of the simple methods used in shop practice, R. D. Mershon, Consulting 
Engineer, has applied the telephone to an old ballistic method in such a 
manner as to make it quite accurate and readily applied. 

Mershon's ^Method. — The following cut shows the connections. A 
telephone receiver, shunted with a condenser, is connected in the line from 
the source of current, the wave form of which it is wished to determine. A 
contact-maker is placed in the other leg, and an external source of steady 
current, as from a storage battery, is opposed to the alternating current, as 



DETERMINATION OF WAVE FOBM. 



51 



CONTACT MAKER 




-hF— - 3 

41. Mershon's method of de- 
termining Wave Form. 



shown. The pressure of the external current is then varied until there is 
no sound in the telephone, when the pressures are equal and can be read 
from the voltmeter. The contact- ^ c TERM | NALS 

maker being revolved by successive 
steps, points may be determined for an 
entire cycle. 

Duncan's Method. — Where it 
is desirable to make simultaneous de- 
terminations it will ordinarily require 
several contact-makers, as well as full 
sets of instruments. Dr. Louis Dun- 
can has devised a method by which one 
contact-maker in connection with a 
dynamometer for eaeh curve will en- 
able all readings to be taken at once. 
The following cut shows the connec- 
tions. The fixed coils of all the dy- 
namometers are connected to their 
respective circuits, and the fine wire 
movable coils of about 1,000 ohms each Fig* 
are connected in series with a contact 
maker and small storage battery. The 
contact-maker is made to revolve in synchronism with the alternating current 
source. Now, if alternating currents from the different sources are passed 
through the fixed coils, and at intervals of the same frequency current from 
the battery is passed through the movable coils, 
the deflection or impulse will be in proportion 
to the instantaneous value of the currents 
flowing in the fixed coils, and the deflections or 
the movable coils will take permanent position 
indicating that value, if the contact-maker and 
sources of alternating current are revolved in 
unison. 

The dynamometers are calibrated first by 
passing continuous currents of known value 
through the fixed coils, while the regular in- 
terrupted current from the battery is being 
passed through the movable coils. 

Ryan's Method. — Prof. Harris J. Ryan, 
of Leland Stanford University, designed a special 
electrometer for use in connection with a very fine 
series of transformer tests. This instrument will 
be found described and illustrated in the chapter 
on description of instruments. 
The method of using it is shown in the cut below, in which the contact- 
maker shown is made to revolve in synchronism with the source of alter- 



< 




Fig. 42. Duncan's method 
of determining curves 
Of several circuits at the 
same time. 



nating current. The terminals d d u 
connected to any one of the three sets 
of terminals, a a lf b fe lf c ci. 

The terminals, a a x , are for reading 
the instantaneous value of the pri- 
mary impressed E.M.F.; b b u the 
same value of the current flowing 
through the small non-inductive re- 
sistance, R; and c C] the same value 
of the secondary impressed E.M.F.; 
the secondary current being read 
from the ammeter shown. Of course 
if the contact-maker be cut out, then 
all the above values will be V mean 2 . 

Rosa Curve Tracer. 

This instrument consists of a hard- 



of the indicating instruments can be 



I riAnsrumviEK. 




RYAN ELECTR0M.ETEH 



Fig. 43. Prof. Ryan's Method of 
obtaining Curves of Wave Form 
for studying Transformers. 



rubber cylinder upon which is wound a single layer of bare wire. A con- 
stant current from a small storage battery is sent through this coil causing 



52 



SYMBOLS, UNITS, INSTRUMENTS. 



RECORD CYLINDER 

F 




Fiq. 44. Rosa Curve Tracer. 



a uniform drop of potential between its ends. (See Diagram, Fig. 44.) A 
voltmeter connected between the terminals indicates the drop, and the re- 
sistance R in series with the battery serves to regulate this drop. The 
current to be plotted passes through the non-inductive resistance A B and the 
problem is to measure the instantaneous values of the drop between these two 
points at successive instants throughout the period of a wave. The point B 

is joined to the middle point Q of the 
spiral wire M N. A is joined through 
the revolving contact-maker CM to a 
sliding contact P. 

The contact-maker is joined to the 
shaft of the alternator, or is at least 
driven in synchronism with it; then 
every time the contact is completed at 
any particular phase of the wave, the 
current has the same value and the gal- 
vanometer will show a deflection. If 
the sliding contact P be adjusted so that 
the galvanometer shows no deflection, 
then the potential difference between the 
points P and Q is the same as that 
between the points A and B. This value 
is proportional to the distance P Q, and is positive on one side and negative 
on the other side of Q. 

For making the record, a cylinder is arranged opposite the potentiom- 
eter wire and slider, upon which the paper for the record is wound. A tripping 
point is attached to the slider in such manner that when the galvanometer 
has been brought to zero by the adjustment of the resistance R, the pointer is 
tripped and a point impressed on the record paper through a typewriter rib- 
bon, tand at the same time the record cylinder is advanced a notch or series 
of them as may be required, ready for the next record. By this means the 
plotting of a curve of current or potential takes but a few seconds. 

Oscillograph. — This form of instrument devised by Blondel and others 
is much used for the analysis of wave forms of current and electromotive 
force, and for the study of potentials and other properties of alternators or 
other forms of dynamos and motors. It is extremely sensitive and will detect 
and show either on a screen or a photograph, the most minute variations in 
current and potential. The Blondel type described below will serve to show 
all the principles of the instrument. Duddell has somewhat improved upon 
this one, and the General Electric 9 Co. has designed another that is especially 
adapted to workshop practice. 

The engraving (Fig. 45) shows the general appearance of the oscillograph. 
The apparatus is mounted in a box (Fig. 46) with an arc lamp at one end. 
Above is a ground-glass screen upon which the -wave forms are traced by 
a spot of light. The magnet is mounted on the left in an inverted position. 
It is a permanent magnet and made up of six horseshoe pieces. Between 
the poles are placed two similar sets of vibrating bands, separated by an iron 
bridge-piece which renders each one an independent unit. In this w T ay two 
wave forms can be taken at once, such as the electromotive force and current, 
and are seen on the screen in their relative positions. 

The arrangement of mounting will be seen in Fig. 47; the band is a very 
fine and narrow strip of soft iron about one thirty-second of an inch wide 
and one five-hundredth of an inch thick. This band is held in a mov- 
able support in a vertical position between the poles of the magnet. It 
is stretched on the support between two ivory bridge-pieces and is attached 
at a to a sliding piece which moves in a rectangular groove. The slider car- 
ries a rod n above, which passes to the top and has a nut $ on the end. Be- 
low S is a spring contained in a tube, so that by turning the nut the band 
stretches more or less between the bridges. The band carries a small, 
mirror m in the center. The mirror support is mounted in an oil box T 
of ivory, which fits into place between the magnet poles and can be turned 
about by the collar D. At P are two iron pieces inserted in the cylinder 
which serve to concentrate the field; at L is a lens placed in front of the 
mirror. In this way the soft iron piece vibrates without the use of pivots 
or suspension. Each horizontal element of the band acts like a small mag- 
net, and the deflections produced by the coils accumulate from the extremi- 



DETERMINATION OF "WAVE FORM. 



53 



ties to the center of the band, thus increasing its sensitiveness consider- 
ably. The total deflections indicated by the mirror are proportional to the 
current. Owing to the properties peculiar to vibrating bands a very high 




< 



Fig. 45. Blondel Oscillograph, 1902 Model, Interior View. 




Fig. 46. Blondel Oscillograph, 1902 Model, Mounted in Case. 



frequency is obtained and this is further increased by the tension which is 
given to it and by its position in the magnetic field. Where the wave form 
contains small irregularities it is of course important that these should not 
be affected by the vibration proper to the mirror, and the higher this rate of 
vibration the more correctly will the wave form be indicated 



54 



SYMBOLS, UNITS, INSTRUMENTS. 



l> l 



I 



The method of mounting is seen in Fig. 48. The current coils are gener- 
ally made up of thin copper strip. At P P' are the pole-pieces, built of 
laminated iron, for concentrating the effect on the strip. There are two 
similar vibrating sets separated by an iron partition in the center, thus form- 
ing two different oscillographs which 
are quite independent of each other; 
even three sets can be mounted in this 
way. The oil tube T containing the 
mirror may be slid up and down by the 
lower screw v and may be turned hori- 
zontally by the endless screw V. On 
the left is seen the complete mounting; 
the front coil has an elliptical opening 
to allow the light to pass. At M is an 
adjustable mirror which gives a perma- 
nent spot of light to form the, base line 
of the curves. 

By using the vibrating band, a period 
of 50,000 vibrations per second has 
been reached, representing the oscilla- 
tion period proper to the band. In 
this case the instrument is sufficiently 
sensitive, although it may be made 
much more sensitive by using a band 
having 15,000 to 20,000 vibrations, 
which will answer in most cases where 
the wave forms are not too irregular. 
The sensitiveness in the latter case 
answers to a displacement of the spot 
of light of 100 millimeters per ampere 
on a screen one meter distant. The 
use of soft iron pole-pieces to concen- 
trate the effect gives a high magnetic 
intensity to the band, and in fact it is 
generally brought to saturation owing 
to its small volume. It is found that 
the band has an advantage in being 
saturated. The sensitiveness increases 
at first while the band is not yet sat- 
urated, then decreases when the mag- 
netization of the piece increases less 
rapidly than the field strength. The number of vibrations continues to in- 
crease, rapidly at first, then slowly, as the band becomes saturated. The re- 
sults depend in a great measure upon the quality of the iron used for the band. 
The mirrors must be very small and light when mounted on such a thin 
strip. They have now been reduced as low as 0.2 millimeter wide and 0.5 
millimeter high, with a thickness of but 0.05 to 0.1 millimeter. Silvered glass 
or mica is used, and the mirrors are fastened to the bands with shellac before 
the latter are mounted. As the band is enclosed in an oil box it is free from 
rust and well protected. The sensitiveness of the instrument may be greatly 
varied by using an iron yoke which is placed against the poles of the perma- 
nent magnet and acts as a shunt to diminish the strength of the field at the 
poles. 

To the right of the box will be seen the arrangement of the oscillating mirror 
which gives the to-and-fro motion to the spot of light in order to form the 
wave. The device will be understood by the diagram, Fig. 49. *S is an arc 
lamp which throws a beam of light by means of the lens X and shutter F upon 
the mirror of the oscillograph n; this beam is then reflected and passes through 
the lens /, falling on the oscillating mirror m placed behind it. The latter is 
given a to-and-fro motion by a small synchronous motor. The beam of light 
thus far has two movements, one by the mirror n of the oscillograph and the 
other by the mirror m, and the resultant of the two gives the wave form which 
is projected above on the ground-glass screen P. The to-and-fro movement 
of the mirror is obtained by a cam fixed to the motor-shaft. During two 
complete periods of the wave the mirror must be moved at a continuous 



Fig. 47. Blondel Oscillograph, 
snowing Method of mounting 
Vibrating Band. 



DETERMINATION OF WAVE FORM. 



54a 




« 



Fig. 48. Blondel Oscillograph, showing the Arrangement of the Magnet 



o 



""tt^lria 



lU? 



.— ~---s 



Fig. 49. Diagram showing the Arrangement of the Apparatus in the 

Blondel Oscillograph. 



54b symbols, units, instruments. 

rate from top to bottom, and during the next period it must be able to return 

so as to continue the movement (as will be 

^ noticed on the photograph two complete 

r\jk /Xw waves are thrown on the screen). This is 

/ X \ / A \ carried out by the profile of the cam which is 

/ / \ \ / / \\ sucn tnat tne m i rror nas a uniform move- 

\~\/~7 \ \J ment during two cycles of the wave, and the 

\ /\f \ X next cycle is occupied by the return of the 

^ ^ mirror (during this time an electrically oper- 

Fig. 50. ated shutter placed at F cuts off the light), 

so that the eye perceives only a continuous 

trace of the wave. To observe phenomena which are not periodic the motor 

is replaced by a pendulum device. 



MEASUREMENTS. 

Revised by W. N. Goodwin, Jr., and Prof. Samuel Sheldon. 
ELEXEXTARl' LAWS OF ELECTRICAL CIHCOI.I. 

Ohm'i law is the fundamental law of electrical circuits and is expressed 
in the following equations. 

R 
E = IR 

*=i 

where / = Current strength in amperes, 

R = Resistance in ohms, 
E = Electromotive Force in volts. 
The conductance of a conductor is the reciprocal of its resistance, and 
the unit is called a mho, so that Ohm's law may be stated as follows: 

I -EG 
where G =s conductance in mhos. 

multiple Circuits. — The conductance of any number of circuits in 
parallel is equal to the sum of the conductances of the individual circuits, 
which is, as stated above, the reciprocal of their resistances. The combined 
resistance then is the reciprocal of the conductance thus found. 
Thus in Fig. 1, if r and r\ be two resistances in 

parallel, the combined resistance = - : — — A— • 

r n 
The joint resistance of any number of resistances 

in parallel as a, b, c, and d is - - ■ 

a o c a 
Current in a multiple Circuit is divided 
among the separate circuits in direct proportion to 
their respective conductances, or inversely as their resistances. 
In Fig. 2, the total resistance of circuit 



( 





r \ total current 

' and i =■ 



r-\-n 

E (r + n) 



En 



' Rr + Rr\ -{-rri 



Er 



Rr -\r Rr\ + rri 



Rr + Rri -f m 



Fig. 2. 



KIRCHOFF'§ LAWS. 



First Law, — If in any circuit a number of currents meet at a point, 
the sum of those flowing toward that point is equal to the sum of those 
flowirig away from it. 

Second law, — In any closed circuit, the algebraic • _ 

sum of the products formed by multiplying the re- 
sistance of each part by the current passing through 
it is equal to the sum of the electromotive forces in 
the circuit. 

By means of these, laws, the current in any part of 
an intricate system of conductors can be found if the 
resistances of the different parts and the electromotive 
forces are given. 

Thus in Fig. 3, according to the first law i = tj + i 2 
and from the second law i=i x + i 2 and from the second 
law E = i^ and iir 2 = tirj. 




Fig. 3. 
From these three formulae, the three unknown currents can be deduced 
The same method can be applied to more complex circuits. 

55 



56 MEASUREMENTS. 



RESISTANCE MEASIJRIIIENIS. 

Substitution Method. — This is the simplest method of measuring 
resistance. The resistance to be measured is inserted in series with a 
galvanometer and some constant source of current, and the galvanometer 
deflection noted; then a known adjustable resistance is substituted for the 
unknown and adjusted until the same deflection is again obtained, then 
this value of the adjustable resistance is equal to that of the resistance 
to be measured. , 

Differential Galvanometer Ifletliod. — In galvanometers having 
two coils wound side by side, separate currents sent through them in opposite 
directions exert a differential action on the movable system. In a diner- 
ential galvanometer the two coils are equal in their magnetic action on 
the movable system for equal currents, so that equal currents sent through 
them in opposite directions will not deflect the needle. If tne currents 
are unequal, then the deflection is a measure of then difference. This 
form of galvanometer may be used to measure resistance by inserting the 
unknown resistance in circuit with one coil of the galvanometer and a 
known adjustable resistance with the other, both circuits being connected 
in multiple. Then when the resistance is adjusted until no deflection is 
produced the resistances in the two circuits are equal. 

The method is often used in the comparison of the conductivity of wire, 
and where rapid measurements not requiring great accuracy are desired. 

Wheat stone's Bridg-e. — For accurate measurements of resistance 
the Wheatstone Bridge method is almost universally used; Fig. 4 is a dia- 
gram of the connections in which a, o, and ti are 
known resistances and x the unknown resis- 
tance to be measured. G is the galvanometer, 
and B is a battery of several cells, the number 
. 4 of which may be varied according to the value 
k of the resistance x. R is adjusted until there 
is no deflection of the galvanometer needle when 
both keys are closed. 

The battery key should always be closed be- 
fore the galvanometer key is depressed or there 
will be a "kick" in the galvanometer due to the 
v A self inductance or capacity of the circuit under 

* IG * 4 * test. 

When a balance is established — =-, or x = R -• 
R a a 

The resistances a and b are, in practice, made even multiples of 10, so 
that x can be read directly from R, the proper number of figures being 
pointed off decimally. 

If a = b the value of x is the same as R. If x be greater than the ca- 
pacity of R, or low in comparison to it, then a and b must be so chosen 
that their ratio respectively multiplies or divides R. 

For example, let a = 10 ) 7, 1000 

b = 1000 then a> = - , R = ^r X 243 = 24 ' 3( *°- 
ft = 243 ) a 10 

The ratio of a to b being 100, any reading as R is multiplied by 100, or 
again let 

a — 1000 ) in 

b = 10 then x - -r^rz X 243 = 2.43. 

R — 243 J 100 ° 

The ratio of a to b being x fo, any reading as R should be divided by 100. 

A commercial form of Wheatstone Bridge of the Weston Model is shown 
diagrammatical ly in Fig. 5. This type, called the "plug in" type, or some 
modification of it, is most commonly used. It has the advantage over the 
44 plug out " type in that fewer plugs are required, there being but one 
plug needed for each decade; this reduces the plug error to a minimum. 




RESISTANCE MEASUREMENTS. 



57 



Direct Reading* Ohmmeter. — Another form of instrument used 
for measuring resistances is known as the direct reading ohmmeter. Briefly 
described it is simply a slide wire bridge, the wire forming two of the arms 
of the bridge, a known resistance a third arm, and the unknown resistance 

Hllllh 



_ .<§) Ba (§>- 

THOUS. HUNDS. TENS UNITS R 

jW\AA (AVVWN ^VWWV) fVWWV| 



ill xi bo 



x 



ly* ih> 



|W/VW 



i > •? ? p* * 

4 sQr 4 sOr 4 C) 6 4 G° {a? 

3 K?' »Ep- »Q t %53 7 sS? 

2 sOr a vOl? 8 2 sCv 8 2 vLv 8 s£-v 




) 9 j < 






pAAVW 



Qio oQ Qio oQ Qio oQ Qio_ Qioo(^ 



idELSL.-! 



^F 



fi..;n. j 



!Ba 



— - P Ga 



< 



X l 

AWVW — I 



L* 



Fig. 5. 



the fourth. The slide wire is graduated to read directly in ohms, and is 
printed with numbers in black and red. The black numbers refer to a low 
reading scale which is used when the single plug of the instrument is fitted 
into the hole marked black, and the red numbers refer to a higher scale 




Fig. 6. 



Fig. 7. 



Fig. 6 shows diagrammatically the connections of this Ohmmeter, and Fig. 7 
gives the same ones expanded into the conventional Bridge Form. 

when the plug is inserted in the hole marked red. This instrument usually 
has four scales, although it is sometimes made with three and five. The 
slide wire is doubled back on itself by means of a heavy cross block of 
practically zero resistance. 

The detector circuit comprises a detecting instrument ordinarily a tele- 
phone receiver, and a stylus, which is touched at various points along the 



58 



MEASUREMENTS. 



slide wire until the detector by silence indicates a balance, when the result 
is read directly in ohms. In some of the instruments the battery is equipped 
with a small induction coil which provides alternating current. In this 
form the instrument is useful for measuring electrolytic resistance and 
other resistances containing electromotive forces that may be developed 
by the presence of current therein, and by the use of a suitable condenser 
in place of the known resistance, capacities can be compared. 

Directions for Use of j§ag*e Direct Reading* Ohmmeter. — 
To Measure Resistance. Connect the terminals of the circuit to be measured 
to the posts, A and D. Place the telephone receiver to the ear and close 
the battery key, K, located in the receiver. Hold the stylus, S, in the 
hand in the same manner as a pencil, and with it touch the straight wires 
along their entire length until a point is reached where gently tapping the 
stylus on the wire produces no sound in the telephone. The resistance 
sought is then that indicated by the scale under that point of the wire. 
During these readings the plug, P, must be in one of the sockets at the 
right-hand end of the rubber cross-bar. When in the socket marked ••red" 
the scale numerals printed in red should be used. When in the socket 
marked "blue" the blue numbers should be read, etc. 

Slide- wire Bridgre. — A very convenient form of bridge for ordinary 

use where extreme accuracy is not de- 
manded is the slide-wire bridge, shown in 
Fig. 8. It consists of a wire 1 meter long 
and about 1.5 mm. diameter stretched 
"2a ^~/x ~^ v ~\^ N ~\ parallel with a meter scale divided into 

( r~\ 4/ ^ \ iv millimeters. A contact key is so arranged 

p / ip ii is — 2 — °i i° — z n \ < as to be moved along the wire so that 

<~A<\ | o ie 20 30 40 so Co 7o 8 o | 4^ P -=— contact with it can be made at any 

point. 

A known resistance R is connected as 
shown; x is the unknown resistance; the 
galvanometer and the battery are con- 
nected as shown in the figure; after closing 
the key k t the contact 3 is then moved 
along the wire until the galvanometer needle returns to zero; 




Fig. 8. 



then again; 
and 



a : b :: R : x, 
bR 



The Carey- Foster IfCetnod. — For the very precise comparison of 
nearly equal resistances of from 1 to 100 ohms this method yields exquisite 
results. In Fig. 9, Si and S 2 represent the two 
nearly equal resistances to be compared, and R t , 
R 2 represent nearly equal resistances, which, for 
best results, should not differ much in magnitude 
from Si and S 2 . Si and S 2 are connected by a 
slide wire whose resistance per unit length p is 
known. The battery and galvanometer are con- 
nected as in the diagram. A balance is obtained 
by moving the contact c along the stretched wire. 
Suppose the length of the wire on the left-hand 
side to the point of contact to be a units. Then 
exchange S t and S 2 for each other without alter- 
ing any other connections in the circuit. Upon 
producing a new balance, let a x be the length of 
wire to the left of the contact. 




Fio. 



9. Carey-Foster 
Bridge. 



Then 



Si = S 2 + (« — ai) p. 



Special commutators are upon the market which have for their purpose 
the easy exchange of Si and S 2 . 

To avoid thermal effects, which are quite considerable with resistances 
made of some materials, the battery should be commutated for each position 
of the resistances to be compared. The readings for the two balances ac- 
companying the battery commutation should be averaged. 



RESISTANCE MEASUREMENTS. 



59 




Measurements of Low Resistances. 

Kelvin's Doable 

Bridge. — If a Wheatstone 
bridge be used to compare re- 
sistances having a value much 
less than one ohm, the terminal 
and contact resistances produce 
a considerable error in the re- 
sults. In conductors having 
such low resistance, the value 
of the resistance given or to 
he measured is considered as ly- 
ing between two definite points. 
In standard resistances these 
points are connected to two ter- 
minals called potential terminals. 

Kelvin has designed a modified form of Wheatstone bridge in which the 
above-mentioned errors are eliminated. The method is shown diagrammati- 
cally in Fig. 10, in which R and x, the resistances to be compared, lie between 
S and Si on one and between T and T\ of the other, and are connected 
together at y; n and o are auxiliary resistances also adjustable. A galva- 
nometer is connected through a key, as shown, to two points, one at the 
junction of n and o; the other at the junction of a and b. If n and o be 
so adjusted that n: o: : R: x, and o and b be adjusted so that the galvano- 
meter is balanced, then 

a :b : : R : x, 

bR 
or x = 



i 



Fig. 10. Kelvin's Double Bridge. 



In practice, n and o may be changed during the adjustment of a and b 
so as to maintain the ratio of n to o the same as that of a to b, either by 
changing n and o, on standard rheostats, or by opening the circuit at y 
and adjusting n and o, as in a regular bridge, for a balance after each trial 
value of a and b; then when a balance is obtained in the galvanometer 
with circuit at y both open and closed the above equation holds good. 

Another UKethod for Comparison of Ion Resistances. — 
For comparing the resistances of ammeter shunts, etc., with standard side 
terminal resistances of the Reichsanstalt 
form, the method of Sheldon yields 
very accurate results. The unknown 
resistance x, Fig. 11, which may be as- 
sumed to he supplied with branch po- 
tential points a 5, is connected by heavy 
conductors in series with a standard re- 
sistance R, having potential points c d. 
From the two free terminals T T 1 of 
these resistances are shunted two 10,000 
ohm resistance boxes S P, adjusted to 
the same normal temperature, and 
wound with wire of the same or negli- 
gable temperature coefficient, and con- 
nected in series. From the point of 

connection e, between the two boxes, connection is made to one terminal of 
the galvanometer g, the other terminal being connected successively with 
the potential points a, 6, c, and d. At the outset all the plugs are removed 
from the box S, and all are in place in the box P. After connecting T and 
T 1 with a source of heavy current, plugs are transferred from one box to the 
corresponding holes in the other box (this keeps the total resistance in the 
two boxes constant) until no deflection is observed in the galvanometer. 
This operation is repeated for each of the potential points a, b, c, and d. Rep- 
resenting the resistances in the box S on the occasion of each of these bal- 
ances by Sa, Sb, Sc, and Sd respectively, we have the following expression 
for the value of the unknown resistance : 




Fig. 11. Precise Measurement. 



. Sa — Sb 
' Se — Sd 



R. 



60 



MEASUREMENTS. 



Note. ■ — Mr. E. F. Northrup gives the following formula as handy in 
determining the percentage conductivity of metal wires. This conductivity 
is generally^ expressed as a certain per cent conductivity of Matthiessen's 
standard. To determine the conductivity, a resistance R of a sample is 
usually determined at a temperature 20° C and of a length I. From this 
measurement the per cent conductivity may be expressed as follows: 

Percentage conductivity = - 



where 



' R20XW X 581,054* 
I — length in centimeters, _ W =z weight in grams, 

d = specific gravity. 



: resistance in ohms at 20° C, 



RE§I§TAIICE OF OALVA^OMETER§. 




When a second galvanometer is available, by far the most simple and sat- 
isfactory method is to measure the resistance of the galvanometer by any 
of the ordinary Wheatstone's bridge methods. Take the temperature at 
the same time, and, if the instrument has a delicate system, remove the 
needle and suspension. 

Hall Deflection method. — Connect the galvanometer in series with 

a resistance r and battery as in the following figure. 

r Note the deflection d ; then increase r so that the new 

deflection d x will be one-half the first, or - = d x ; call 

the new resistance r\ ; then 

Resistance of Galvanometer = 7\ — 2r. 
If the instrument be a tangent galvanometer, then 
d and d t should represent the tangents of the deflec- 
tions. 
Kelvin's Method. — Connect the galvano- 
meter, as a? in a Wheatstone's bridge, as in Fig. 13. 
Adjust r until the deflection of G is the same, 
whether the key is closed or open. 

G = r b -. 
a 

The result is independent of the resistance of the 
battery. The battery should be connected from the 
junction of the two highest resistances to that of 
the two lowest. 



Fig. 12. 




Fig. 13. 



RESISTANCE OF BAITERIi!§, 



I — vV&V-^A. 



Condenser Method. — For this test is needed a condenser C, a ballistic 
galvanometer G, a double contact key k x , a resistance R, 
of about the same magnitude as the supposed resistance 
of the battery B, and a single contact key k 2 . Connect as 
in the following figure. With the key k 2 open, press the 
key fc lf and observe the throw 9 1 in the galvanometer. 
Then, after the needle has come to rest, with key k 2 
closed, repeat the operation observing the throw 2 . 
Then the resistance of the battery 

x = R d -±^- 



B, 




Reduced Reflection Method. — Connect the 
battery B in circuit with a galvanometer G and a resist- 
ance r as in Fig. 15. Note the deflection d. and then in- 
crease r to r 1 and note the smaller deflection d x ; then, if the deflections of 
the galvanometer be proportional to the currents, 
rydi — rd 

d 



— G. 



Fig. 15. 



If r x is such that d } = - 



then 



B 



■(2r+G). 



RESISTANCE OF HOUSE CIRCUITS. 



61 



The E.M.F. of the battery is supposed to remain unaltered during the 
measurement. 

Mance's IfEetbod. — Connect the battery as x 
in Wheatstone's bridge as in Fig. 16. Adjust r until 
the deflection of G is the same whether the key be 
closed or open. 

Then B = r-' 

a 

The galvanometer should be placed between the 
junction of the two highest resistances and that of 
the two lowest. 

Resistance of Battery while Working-. — Connect the battery B 
with a resistance r, and also in parallel with a condenser C, galvanometer 
G, and key k ; shunt the battery through s with key k] , as in Fig. 17. 

Close the key k, and note the deflection d of 
the galvanometer, keeping k closed, close k x and 
note d u the deflection in the opposite direction. 
Then the battery resistance 




( 




B = i 



d — dy- 

dis 



If r be large, the term 



dis 



is negligible, and 



Bz=i 



d — d^ 
» being the multiplying power of the shunt. 

Workshop Method, Applicable as well to Dynamos. — With 
dynamo or battery on open circuit, take the voltage across the terminals 
with a voltmeter, and call it d ; take another reading d± at the same points 
with the battery or dynamo working on a known resistance r : then the in- 
ternal resistance R z= — - — - r. 

In the case of storage batteries, if the current / be read from an inserted 
ammeter when charging, the resistance of the battery is 

and when discharging B = — j^-± . 



RESISTANCE OE AERIAL LIAES OR HOUSE 
CIRCUITS. 

Conductor Resistance. — When the circuit has metallic return, it is 
easily measured by any of the Wheatstone's bridge methods, or, if the circuit 
conductor can be supplied with current through an ammeter, then the fall 

of potential across the ends of the con- 
ductor will give a measure of the resistance 




by ohms law, viz., 

Resistance = 



drop in volts 
current 



"^Earth — Earth ~ 

Fig. 18. 



If the circuit has earth return as in tele- 
graph and some telephone circuits, then 
place far end of the line to earth, and con- 
nect with bridge as in Fig. 18. 

Then the total resistance x of the line and 

earth, is x — r — . 



If a second line be available, the resistance of the first line can be deter- 
mined separated from that of earth, as well as the resistance of earth. 



62 



MEASUREMENTS. 



Let 



r = resistance of first line, 
r\ = resistance of second line, 
r 2 = resistance of earth. 



First connect the far end of r and r x together, and get the total resistance 
R; connect r and r 2 , and measure the resistance R x , connect r x and r 2 , and 
get total resistance R 2 . Then if 

R±Rj_±Rt 

~ 2 

r = T — R 2 , 

n=T-R lt 

r 2 —T — R. 

This test is particularly applicable to rinding the resistance of trolley 
wires, feeders, and track. 

For other methods for resistance measurements see under "Tests with 
Voltmeter." 



Ro 



MEASUREMENT OF ELECTROMOTIVE FORCE. 

Of Batteries. — This can usually be measured closely enough for all 
practical purposes by a high class low-reading voltmeter (see Tests with a 
Voltmeter). 

Wheat»tone V Method. — Connect the cell or battery to be compared 
in circuit with a galvanometer and high resistance r, and note the deflec- 
tion d; t^ien add another high resistance 
r x (about equal to r), and note the de- 
flection d x . Next, connect the cell with 
which the first is to be compared in cir- 
cuit with the galvanometer, and connect 
in resistance until the galvanometer 
deflection is the same as d; then add 
further resistance R until the galvano- 
meter deflection is the same as d x ; then, 
if e equals the E.M.F. of the first cell, 
and E equals the E.M.F. of the cell with 
which it is compared, 

n : R : : e : E, 







_L 



and 



n 



Fig. 19. 



Or, the electromotive forces are pro- 
portional to the respective resistance 
which must be added to reduce the deflection the same amount. 

Lumsden's Method. — The two cells E x and E 2 to be compared are 
arranged as shown in Fig. 19. R x and R 2 are adjustable resistances which 
are large as compared with the resistances of the cells. R x and R 2 are 
changed until the deflection in the galvanometer is reduced to zero. 



Then 



Ei _ Ri 
E t R 2 



If greater accuracy be required than that obtained by the above methods, 
some potentiometer method may be used, 
in which the cell to be measured is compared 
directly with a standard cell. 

Lord Rarleigrli'g Compensation 
Method. — In the following diagram let 
R and R x be two 10,000-ohm rheostats, B 
be the battery of larger E.M.F. than either 
of the cells to be compared, B x be one of the 
cells under test, G be a sensitive galvano- 
meter, HR be a high resistance to protect 
the standard cell, and k be a key. Obtain 
a balance, so that the galvanometer shows 
no deflection on closing the key k, by trans- 




Fig. 20. 



MEASURING CAPACITY. 



63 



f erring resistance from one box to the other, being careful to keep the sum 
of the resistances in the boxes equal to 10,000 ohms. Observe the resistance 
in R ana call it R x . Repeat with the other cell B 2 , and call the resistance 
R 2 . Then the E.M.F.'s of the two cells 

E\\ E% = R\\ R%. 

Note. — Special boxes are on the market which automatically change the 
resistances R and Ri, maintaining the sum of the resistances constant, the 
value of the resistance being read directly from the dials. 

Direct Reading* Potentiometer. — There are many forms of po- 
tentiometers available, which are used in connection with a standard cell, 
and on which the potential difference to be measured is read directly from 
the switch dials of the instrument when it is balanced as shown by a gal- 
vanometer. Such potentiometers generally read to 1.5 volts. To meas- 
ure higher voltages than this a volt box must be used, which is simply a 
high resistance, across which the voltage to be measured is connected. 
Connections are brought out from the resistance so as to include a known 
portion of it, having such a value that the potential difference across it 
will be less than 1.5 volts. This is then measured on the potentiometer, 
and the value found multiplied by the constant of the volt box. 

Measurement of Current Uy Potentiometer. — The current to 
be measured is passed through a standard low resistance, say, .01 or .001 
ohm, and the difference of potential across its potential terminals meas- 
ured by means of a potentiometer. Then the current is by Ohm's law 

'-§ 

where E is the difference of potential as measured, and R the resistance 
of the standard. 



i 



HTEASURI1VG CAPACITY. 



Arrangement of Condensers. In Parallel. — Join like poles 

of the several condensers together as 
in the figure ; then, the joint capacity 
of the set is equal to the sum of the 
several capacities. 

Total capacity = c + c, + c n + c,,,. 

Condensers in Series. — Join 
the unlike poles as if connecting up 
battery cells in series as in Fig. 22, 
then the joint capacity of all is the 




Fig. 21. 



reciprocal of the sum of the reciprocals of the several capacities 
1 



Capacity C: 



i + I + A 

c c. C// 



+i 




Fig 22. 



Capacity l>y Direct Discharge. — 

Charge a standard condenser, Fig. 23, C« by 
a battery E for a certain time, say 30 sec- 
onds ; then discharge it through a ballistic 
galvanometer G ; note the throw d. 

Next charge the condenser to be measured, 
C lt by the same battery and for the same length of time, and discharge this 
through the same galvanometer noting the throw d x ; 

Then CkiC x iid: d x . 




and 



<\- 



For Kelvin's and Gott's methods see pages 326-327, " Cable 

Testing." 




64 MEASUREMENTS. 

Bridg-e OTethod. — For comparing the capacities of two condensers, 
Ce and C, which are approximately the same, connect as in Fig. 24 through 
two rather high inductionless resistances 
i? t and JR 2 to the key k which makes and 
breaks contacts at each end. E is a bat- 
tery. A galvanometer is inserted between 
the ends of the condensers where they 
join the resistances. Adjust the resist- 
ances so that no deflection results when 
the key is manipulated. 

Then C=C.|l. Fla *• 

Mo. 

JjOS» of Potential Ifletnod. — The capacity of a condenser may be 
determined by the following formula: 

c = { — a 

2.303 R log - 
e 

where C is the electrostatic capacity, in microfarads, of a condenser, the 
potential of whose charge falls from E to e when it is discharged during t 
seconds through a resistance of R megohms. 

If C is the known and R the unknown quantity, then 

R = * 



2.303 k log - 
e 



In measuring the insulation resistance of a short cable by this method, the 
discharge deflection E, compared with the discharge deflection obtained with 
the same battery from a standard condenser, would give the value of k. 
For long cables, however, this does not give correct results, and the ca- 
pacity must be determined by other methods. 

JEJLECTJt0^i:ACJXJETJ.C iADlCTIOX, 

.Law of Induction. — When the magnetic induction or flux inter- 
linked with an electrical circuit is changed in any manner, an electro- 
motive force is induced in that circuit which is proportional in amount to 
the rate of change of the flux, and acts in a direction which would, by 
producing a current, tend to oppose that change. 

Symbolically expressed the induced electromotive force in volts is 

n d<j> 

€ ~ 10 8 dt 9 

where <J> is the magnetic flux through the circuit, n the number of turns 
of wire, and t the time. 

Self-induced electromotive forces are those induced in a circuit by change 
in the current in the circuit itself. 

Coefficient of ftelf-Ind uction. — The practical unit of self-induction 
is the henry, and is equal to 10 9 absolute units. 

The self-induction in henrys of any coil or circuit is equal numerically to 
the electromotive force in volts induced by a current in it changing at the 
rate of one ampere per second. Thus the electromotive force in volts pro- 
duced in a circuit by a varying current is 

T d i 

e =- L it' 

where L is the self-induction in henrys and i the current in amperes. 

If fa = n, <f> represent the flux turns in the circuit, 
then fa = Li X 10 8 . 

Foi example, if a coil have 150 turns of wire, carrying a current of two 



MEASUREMENT OF COEFFICIENT INDUCTION. 



65 



amperes, producing 200,000 lines of force, or 200 kilogausses through it, 
the flux turns equal 200,000 X 150 = 30,000,000, and the self-induction is 
therefore 

<f>i 30,000,000 

L = Wi = 2X100,000,000 = - l0 henry ' 

If the current of 2 amperes die out uniformly in one second, then the 
electromotive force induced is 



i = L 



: .15 X2- .30 rolt. 



Coefficient of Self-induction of a Long 1 Solenoid. 

L ~ 10 9 
when the permeability is unity. 

Where n =: total number of turns of wire, 

n 1 = number of turns per centimeter length, 
A = area of cross section of solenoid. 
For magnetic substances the above equation must be multiplied by fx, the 
permeability of the medium. 



measurements of The Coefficient of Induction. 
Comparison with Known Capacity. — The coefficient of self- 





Fig. 25. 



Fig. 26. 



induction may be determined by means of a Wheatstone bridge as follows: 
Let A and B, in Fig. 25, be the bridge ratio arms, Ri the adjustable rheostat. 
Connect the circuit to be measured as RL in series with a variable 
non-inductive resistance r and r t a portion of which r t is shunted by a 
standard condenser of capacity C. First balance the bridge for steady 
currents by adjusting R x , that is, when the key K is closed continuously. 
Then alter the proportion of non-inductive resistance r t , shunting the 
condenser until no deflection occurs in the galvanometer when the key K 
is open and closed. Then the self-inductance 

L = Crf. 

Comparison witn Know n Self-Inductance. — Arrange in form 
of bridge as shown in Fig. 26, L being the unknown and L t the standard self- 
inductance. Adjustable non-inductive resistances are connected in series 
with them. Call the resistances in each arm R and R lf A and B are non- 
inductive resistances. First adjust to a balance for steady currents by 
changing R and R lt then adjust A and B until no throw of the galvano- 
meter is observed when the galvanometer key is closed before closing the 
battery key. Then R and R t must be again adjusted for steady currents, 



66 



MEASUREMENTS. 



and so on until a balance is obtained for both steady and transient current!. 

L\ B R\ 




Then 



Fig. 27. Ayrton and Perry's Variable 
Standard of Self-induction. 



If L x be one of Ayrton and 
Perry's adjustable standards of 
self-induction (see Fig. 27), then 
the bridge can be balanced in the 
regular way for steady current, 
and for transient currents by 
varying the self-induction stand- 
ard. 

As shown in the illustration 
this instrument consists of two 
coils wound on sections of con- 
centric spherical surfaces, the in- 
side one of which can be rotated 
with reference to the outside one, 
and thus their coefficient of in- 
duction varied without changing 
their resistance. The scale is 
divided to read in millihenrys on 
one side and in degrees on the 
other. Its range is approximately 
from 3.5 to 42 millihenrys. 

Telephone Method. — A 
modification of the above, which 
is quicker and more practical, is 
by using a telephone in place of 
the galvanometer, and a source 



of alternating or rapidly interrupted direct current for the battery, _ 
shown in Fig. 28. The part ab is a slide wire with telephone contact at 
K; the self-inductances L and L\ are connected as in the previous m«tnod 
with adjustable non-inductive resistances. 
S is a source of alternating current. The 
return circuit should be run parallel and 
close to the slide wire to reduce inductive 
errors. The contact K is moved along the 
wire and placed in a position where the 
minimum sound is heard in the telephone 
and R and Ri are changed to reduce this 
sound to a lower minimum. These oper- 
ations are repeated until finally a point is 
reached where the minimum of sound is 
very sharply denned or silence occurs. 

Then £=£• 




Fig. 28. 



Measurement of Self-Inductance with an Alternating- Cur- 
rent of Known frequency. 

For this test is needed a high resistance or electrostatic alternating cur- 
rent voltmeter, a direct current ammeter, and a non-inductive resistance. 

Connect as in Fig. 29, where R x is an inductive resistance to be measured, 
and S a switch for short-circuiting the ammeter; the A. C. dynamo of fre- 
quency n is so arranged that its terminals may be disconnected, and a 
battery be substituted therefor. 

With the connections as in Fig. 29, close the switch S, and take the drop 
with the voltmeter from a to 6 and the drop from a to C; then disconnect 
the A. C. dynamo, and connect the battery B; open the switch s, and vary 
the continuous current until the drop from a to C is the same as with the 
alternating current, both measurements being made with the same volt- 
meter; then note the current shown by the ammeter, and measure t! e drop 
from a to 6 with the voltmeter. Call the drop across R x from a to \ with 



MEASUREMENT OF MUTUAL INDUCTANCE. 



67 



alternating current, E, and the same with continuous current, E lt and the 
reading of the ammeter with the latter, I. 



Then 



L = 



\/E 2 - E x 2 



2-nnl 

If the resistance R t be known, and the ammeter be suitable for use with 
am 




£>* c r a 



( 



rrrrrrrrrr* 



HI 



Load. 




Fig. 29. 



alternating currents, the switch an d non-indu ctive resistance may be dis- 
pensed with. 



We then have L = — }— — . where I x is the value of the 

2-nnl 



alternating current. 

Note. — The resistance of the voltmeter must be high enough to render 
its current negligible as compared with that through the resistance R t . 

Measurement of Mutual Inductance. 

Connect the two coils whose mutual inductance is to be determined, 
first in series and then in opposition to each other. The self-induction of 
each combination is then measured by any suitable method. 
Let M = the mutual inductance between 
the two coils. 
L = the self-inductance of one coil. 
L y = the self-inductance of the other 

coil. 
L n = the self-inductance of both coils 

in series. 
Z//// = the self-inductance of both coils 
in opposition. 
Then since L u = L-\-L,-\-2M 
and L n , = L + L, - 2 M . 

Then the coefficient of mutual inductance 
desired is 



M = 



L„ - L„, 




Fig. 30. 



Comparison with a Known Ca- 
pacity. — Connect as shown in Fig. 30 
where A and D are two coils whose 
mutual inductance M is required. R 
and R x are two adjustable non-inductive resistances and C a standard 
condenser placed in shunt to R and R lm Vary the resistances R and R* 
until no deflection is observed on the galvanometer when the key is opened 
or closed. Then the mutual inductance is 

M = CRR X . 



68 



MEASUREMENTS. 



Comparison with Known Self-1 nduction by Bridge. — In 

this method the mutual inductance of two coils is compared with the knowij 
self-inductance of one of them. The coil whose self-inductance is knowf 
is connected as R in Fig. 31. The othel 
coil is connected in the battery circuit witfc 
its magnetic circuit opposed to that of th< 
other coil. Then by adjusting the othel 
arms of the bridge to a balance for botli 
steady and transient currents, as in tht 
methods for self-inductance, the mutual 
inductance is 

r + ri 
Another Method. — In order that a 
balance may be obtained without the incon- 
Fig. 31. venience of trial and approximation as in 

the foregoing method, the battery circuit 
may be shunted by non-inductive resistance as S shown in Fig. 32. The 
other connections are similar to those of the previous test. The bridge 
is first balanced for steady currents in the regular way by adjusting the 
resistances R u r, and r x , and then S is changed until no deflection occurs when 
the key is opened or closed. Then the mutual inductance is 

M LRxS 

M ~ (R 1 + R)S + (R + r)R 1 

Comparison of Mutual Inductance with Known Self-In- 
ductance of Another Coil. — Connections are made as shown in Fig. 
33. One of the two coils whose mutual inductance is to be measured is con- 






Fig. 33. 

nected in the battery circuit, and the other in series with an adjustable 
non-inductive resistance as a shunt to the galvanometer. The known 
self-inductance L is connected in the bridge as R. The bridge is first 
balanced, as before, for steady current, then the resistance S is changed 
until no deflection occurs when the key is opened or closed. Then if S be 
the total resistance in the shunt circuit, the mutual inductance is 



M 



LR,S 
(R + Ri) 2 ' 



Telephone Method. — As in measurements of self-inductance, a tele- 
phone may be used in measurements of mutual inductance, as shown in 
Fig. 34. The coil of known self-inductance L is connected in one arm of 
the bridge, as shown at R. The other coil is connected in opposition 
to that coil in the main current circuit, the current supplied being either 
alternating or a rapidly interrupted direct current. The non-inductive 
resistance and the telephone circuit contact are varied until silence occurs 
in the telephone in a manner similar to that described for self-inductance. 



MEASUREMENT OF A.C. POWER. 



69 



Then if p is the resistance of the slide wire for unit length, and the position 
for a balance is a units from the right as shown, then the mutual inductance 

Secohmmeter. - In measurements of inductance, when balancing for 
transient currents the galvanometer deflects in one direction when the 
battery key is closed, and in the opposite direction when it is opened, lo 
increase the sensibility of such tests, Ayrton and Perry have devised the 
secohmmeter. The battery and galvanometer circuits are each commuted 





Fig. 34. Fig. 35. Ayrton and Perry's 

Secohmmeter. 

so as to produce a galvanometer deflection in one direction, and increased 
in amount. This apparatus may be used in connection with any of the 
above tests where galvanometers are used, the balance being obtained 
when the deflection is reduced to zero. Below is given a description of the 
apparatus as shown in Fig. 35. 

This instrument serves the purpose of making an alternating current to 
use in measurements of self-induction, and of commuting such portion of 
this current as flows in the galvanometer circuit to a direct current. 

The instrument consists of two rotating commutators mounted on one 
axis and a train of gears for rapidly driving them. The commutators are 
on the two sides of a cast metal case, one only being shown in the illustration. 
They are electrically insulated from each other. The brushes of one com- 
mutator are mounted on a disk, which can be rotated through an angle of 
90° around the axis. The brushes can accordingly be set so that they will 
reverse the circuits in which they are connected at the same time, of so 
that one will reverse at any desired fraction of a period after the other. 
The driving handle may be attached at two places on the train of gears, 
thus giving two speeds. A pulley wheel is also provided, which may be 
used in place of the handle and the apparatus be driven by a motor. 

MEAiURE^EUTT OE POWER Il¥ ALTER^ATI^CJ 
CVRREIT CIRCUITS. 

In alternating current circuits having inductance in any part of the cir- 
cuit, such as motors, unloaded transformers, and the self-inductance of the 
line itself, the product of the values of the current and the E.M.F. as shown 
by an ammeter and voltmeter does not give the power in the circuit, 
since the current is not in phase with the E.M.F. t _ 

The power at any instant of time in any alternating current circuit is 
equal to the product of the instantaneous values of the current and E.M.F. 
This is shown graphically in (Cut A) Fig. 36. The mean power in the circuit is 

P = EI, 
where E is the effective E.M.F. and / the effective current. The effective 
values of E.M.F. and current are the square roots of the mean squares of 
their respective instantaneous values, or numerically, their maximum 
values divided by V^2 or 1.41. Alternating current measuring instruments 
of either the "hot wire' ' or dynamometer type indicate effective values. 

If the current is not in phase with the E.M.F., and the angular difference 
in phase is <f>, then the power is 

P = EI cos 4>. 



70 



MEASUREMENTS. 




Fig. A. 




MEASUREMENT OF A.C. POWER. 



71 



Cos <f> is called the power factor, since it is the factor by which the apparent 
power EI must be multiplied to obtain the true power. 

Suppose that curve No. 1 in Fig. B, page 70, represents the various values 
of the impressed voltage throughout a cycle, and that curve No. 2 represents 
the various values of the self-induced voltage. Curve No. 2, it will be noted, 
is not in phase with curve No. 1. Its highest value comes at a later time 
than that of curve No. 1, because the self-induced electromotive force is 
never in phase with the impressed electromotive force, as the self-induced 
electromotive force is obviously at its highest point when the lines of force 
induced by the coil are changing most rapidly. This occurs when the 
current is rapidly increasing or diminishing, and not when it is maintain- 
ing a momentarily steady value at its highest point. 

Current will flow in the circuit in proportion to, and in phase with, the 
resultant of the two curves, and the ordinates of this resultant will be the 
algebraical sum of the corresponding ordinate of the two curves. Curve No. 
3 shows the resultant curve constructed in this way. It will be found to be 
similar to the other curves but of a different maximum value, also lagging 
behind the curve of impressed E.M.F., but occurring earlier than the curve 
of self-induced E.M.F. 

In Fig. C are shown the curves representing the impressed E.M.F. and 
the resulting current, and as will be seen the current lags behind. If 
the values of these curves be combined by multiplying them together, 
ordinate by ordinate, this curve representing power will result. This will 
be the true curve of power, as it obviously represents the power at every 
instant, the instantaneous voltage being multiplied by the instantaneous 
current, and consequently takes account of the fact that their maxima 
are shifted with reference to one another. 

If the current and voltage curves are arranged as shown in Fig. D, in 
which the maximum value of the voltage occurs at the same time as does 
the minimum value of the current, the result will be as shown, and no 
power will be produced. 

If the current is in phase with the electromotive force as shown in 
Fig. E, the power curve will appear above the zero line, and the true 
power will also be the apparent power. 

Three Voltmeter OTethod. Ayrton & lumpner. 

This method is good where the voltage can be regulated to suit the load. 

m In figure 37 let the non-inductive re- 
sistance R be placed in series with the 
load a b ; take the voltage V across the 
terminals of R ; J\ across the load a b, 
and Vo across both, or from a to c. 
Then the 



( 




V2 V 2 V 2 

True watts = -^ ^ . 

2 R 

The best conditions are when V = V 1% 
and, if R = £ ohm, 
then W— V 2 2 — V? — F 2 . 

Combined Voltmeter and Ammeter Method. 

This method, devised also by Fleming, is quite accurate, and enables the 
accuracy of instruments in use to be 
checked. In Fig. 38 R is a non-inductive 
resistance connected in shunt to the induc- 
tive load a b, and the voltmeter V measures 
the p. d. across x y. A and A x are ammeters 
connected as shown ; then 




True watt! 



*=f(A' 



-A*- 



(f)> 



If the voltmeter stakes an appreciable 
amount of current, it may be tested as fol- 
lows : disconnect R and V at y, and see that A and A x are' alike ; then con- 
nect R and V at y again, and disconnect the load a b. Then A x =z current 
taken by R and V in multiple. 



72 



MEASUREMENTS. 



WATTMETER MIIHOI)^. 

(Contributed by W. N. Goodwin, Jr.) 

For measurement of power in electric circuits, the wattmeter gives the 
quickest and most accurate results. Since the instrument mechanically 
integrates the products of the instantaneous values of current and E.M.F., 
the power is indicated directly, regardless of the power factor. 

When a wattmeter is connected to a circuit, the instrument itself re- 
quires current and, therefore, some power is consumed in it. This error 
must be calculated and subtracted from the observed readings. Weston 
wattmeters are compensated for this error by means of a coil wound in 
opposition to the field coil and adjusted with it. The. following are a few 
of the important tests with a wattmeter used in power measurements. 

Fig. 39 shows the connections for measurement of power in either a 
direct or single phase alternating-current circuit. The power consumed 
by L is read directly from the instrument. 





Fig. 39. 



Fig. 40. 



In direct current measurements, to eliminate the effect of the earth's 
magnetic field, two readings must be taken; either the connections must 
be reversed for the second reading, or the instrument turned 180° from its 
first position; the mean of the two readings gives the true power. 

If the instrument have a multiplier, it should be connected as shown m 
Fig 40, so that the difference of potential between the stationary and mov- 
abTeopils shall be a minimum. 

Checking* IVattnieters. — In checking wattmeters either directly with 
other wattmeters, or by means of a voltmeter and ammeter, the wattmeter 
should be connected so as not to include its compensating coil. In a Wes- 
ton wattmeter the "independent" binding post should be used, shown in 
Fig 39, the pressure circuits being connected in parallel and the field or 
current coils in series. 

Three -Phase Power Measurements. — In unbalanced systems 
two wattmeters are required, connected as shown in Fig. 41. The total power 
transmitted is then the algebraic sum of the readings of the two watt- 
meters. If the power factor is greater than .50, the power is the arith- 
metical sum, and if it is less than .50, the power is the arithmetical differ- 
ence of the readings. 




Fig. 41. 



WATTMETER METHODS. 



73 



Balanced Three>Phase Systems. — One wattmeter may be used 
in three-phase eircuits in which the current lag is the same for all parts 
of the circuit and the load is uniformly distributed. The connections are 
shown in Fig. 42. The current coil of the wattmeter is connected in one 




< 



Fig. 42. 



of the leads as A; one end of the pressure circuit to the same lead, the other 
end is connected successively to each of the other leads as B and C, a read- 
ing being taken in each position. The power is then the sum of the sepa- 
rate readings. 

Second Method for Balanced Circuits. — Another method may 
be used by which the power may be obtained from a single reading of the 
instrument, as shown in Fig. 43. The current coil of the wattmeter is 
connected in one lead as A; one end of the pressure circuit is connected 
to the same lead. 




Fig. 43. 



The other end of the pressure circuit is connected to the junction of 
two resistances r and r, each equal in resistance to that of the wattmeter; 
the ends of these resistances are connected to the other two leads as 
shown at B and C. The power is then 

P = Sp 

where p is the instrument reading. 

If it be desired to use the instrument for higher voltages than that for 
which it was designed, then a resistance R must be added to the instru- 

R + r 

ment branch, of such a value that is equal to the multiplying con- 

r 

stant m desired. 

Each of the other two branches must be increased to R + r. 
Then the power is 

P = 3 mp. 

The Weston " Ybox" multiplier, which may be made for any multiplying 
constant, is constructed according to this principle. 

Any of the above methods can be used equally well for the delta as for 
the star connection. 



74 



MEASUREMENTS. 



> 



TESTS WITH A VOLTMETER. 

The following are a few of the more important tests for which voltmeters 
and ammeters are especially adapted. With some changes and additions 
they have mostly been condensed from an article by H. Maschke, Ph.D., 
of the Western Laboratory published in the Electrical World in April, 1892. 

The scales of the better known portable instruments read, in general, 
from to 150, or some even multiple or fraction of this value. Voltmeters 
are available having scales ranging from 1.5 volts to 750 volts for a full 
scale deflection, and when used with multipliers for any higher range. 
Two or more ranges may be had on the same instrument, so that by simply 
transferring connections from one binding post to another, voltages dif- 
fering greatly in amount may be measured on one instrument. Millivolt- 
meters may be had reading as low as 20 millivolts for a full scale deflection. 

Instruments with Permanent Iflag-nets should not be placed on 
or near the field magnets of motors or generators, nor should they be used 
for measurements in very strong magnetic fields, such as those produced 
in the vicinity of conductors carrying heavy currents. If the fields be 
not too strong, then the error produced in the instrument from this cause 
may be eliminated by taking the mean of two readings, one in position, 
and the other when the instrument is turned 180° from that position around 
its vertical axis. 

electromotive force of Batteries. 



-1» + 




Fig. 44. 



The positive post of voltmeters is 
usually at the right, and marked +• 
In a battery the zinc is commonly neg- 
ative, and should therefore be con- 
nected to the left or negative binding 
post. 

For single cells or a small number, 
a low-reading voltmeter, say one read- 
ing to 15 volts, will be used, the con- 
nections being as per diagrams. 

Electromotive Force 
of Dynamos. 



riliWiUJilHh 




For voltage within range of the instrument available for the purpose, it is 
only necessary to connect one terminal of the voltmeter to a brush of one 
polarity, and the other terminal to a brush of the opposite polarity, and 
read direct from the scale of the instrument. As continuous current volt- 
meters usually deflect forward or back according to which pole is connected, 
it is necessary sometimes to reverse the lead wires, in which case the polar- 
ity of the dynamo is also determined. Of course the voltage across any cir- 
cuit may be taken in the same way, or the dynamo voltage may be taken at 
the switchboard, in which case the drop in the leads sometimes enters into 
the calculations. Following are diagrams of the connections to bipolar and 
multipolar dynamos : 





Fig. 46. 



Fig. 47. 



TESTS WITH A VOLTMETER. 75 

In the case of arc dynamos or other machines giving high voltage, it is 
necessary to provide a multiplier in order to make use of the ordinary in- 
strument ; and the following is the rule for determining the resistance 
which, when placed in series with the voltmeter, will provide the necessary 
multiplying power. 

Let e = upper limit of instrument scale, for example 150 volts, 

E == upper limit of scale required, for example 750 volts, 
R — resistance of the voltmeter, for example 18,000 ohms, 
r = additional resistance required, in ohms. 

Then r = R ^=^ or r = 18,000 75 °~ 15 ° = 72,000 ohms. 

e 150 

The multiplying power = — or — - = 5. 
e 150 

Should the exact resistance not be available, then with any available 
resistance r t the regular scale readings must be multiplied by ( — -j- 1 ) . 

Importance of II igr h Resistance for Voltmeters. 

It is highly important, as reducing the error in measurement, that the in- 
ternal resistance of a voltmeter be as high as practicable, as is shown in the 
following example : 

Let E in the figure be a dynamo, battery, or other 
source of electric energy, senaing current through the 
resistance r ; and vm. be a voltmeter indicating the 
pressure in volts between the terminals A and B. Be- 
fore the vm. is connected to the terminals A and R there 
will be a certain difference of potential, which will be 
less when the voltmeter is connected, owing to the les- 
sening of the total resistance between the two points ; 
if the resistance of the vm. be high, this difference will 
be very small, and the higher it is the less the error. 
Following are the formulas and computations for de- 
termining the error. 

In Fig. 48 let E be the E.M.F. of the generator, 
r the resistance of the circuit across A and B when 
the difference of potential is to be measured, r x the 

resistance of the leads, generator, etc., and R the resistance of the volt- 
meter. Before the vm, is connected the difference of potential between 
A and B is 

With the voltmeter connected the difference of potential indicated by 
the instrument is 

Fl = rM 

1 rR-\-r t r-\- r x R 

The voltage across A and B is, therefore, reduced by the introduction 
of the voltmeter by the amount of 

V Vl {r + rJR 
The error is 

lOOn-! 



( 




— .(^/-V 



+ n)R 



The error r. inversely proportional to the resistance R of the voltmeter 
Example . 
Let E = 10 volts, 

r = 10 ohms, 
ri = 2 ohms, 
R = 500 ohms. 
Then the reading of the voltmeter is 

v 10 X 500 X 10 R . 

Vl (10 X 500) + (2X 10) -|- (2 X 500) ~ S,W °° V01t8, 



7b' 

and the error ia 



V - v x 



MEASUREMENTS 

10 X 2 X 8.3056 



and the percentage error is 



(10 + 2) 500 



.0277 volts. 



__ 100X10X2 _ 
P "(10 + 2) X 500" * 333%> 
If R be made 1000 ohms, then 

r = 10 X 1000 X 10 

(10 X 1000) + (2 X 10) + (2 X 1000) 



= 8.32 volts 



and the error is 

v t -v 

and the percentage error is 
V = 



= 10 X 2 X 8.32 
(10 + 2) 1000 

100 X 10 X 2 



.01387 



- .166% 



is less than -— -• 



(10 + 2) X 1000 
or just one-half the error with R = 500 ohms. 

If the error of measurement is not to exceed a stated per cent p, then r 
and n must be such that 

T\ 

r-\-r x 

If the circuit is closed by a resistance r lt and it be desired to measure 
the E.M.F. of the generator by connecting the voltmeter between any 

two points as A and B, then E =-- ( — ^— - ) Vi, where V± = reading on vm. 

The error between the true value of the E.M.F. of the generator and that 
shown by the voltmeter is 



E - V = 



and the percentage error p = 100 ( b ) ' 



riVi 
R 



If the error is not to exceed p per cent, then the resistance of the gen- 
erator, cables, etc., must not exceed — — • 

100 
For example, with a voltmeter having 15,000 ohms for 150 volts; if p 

must be less than |%, then r x may be as great as - — r^r- = 30 ohms. 

Comparison of E.^I.F. of Batteries. 

Wlieatstone's Method. — To compare E.M.F. of two batteries, A and 
X, with low-reading voltmeters, let E be the E.M.F. of A, and JSi the E.M.F. 
of X. 



-wwwww 




Fig. 49. 



First connect battery A in series with the voltmeter and a resistance r, 
switch B being closed, and note the deflection V\ then open the switch B, 
and throw in the resistance r lt and note the deflection Vy Now connect bat- 
tery X in place of A, and close the switch B, and vary the resistance r until 
the same deflection Voi voltmeter is obtained and call the new resistance r 2 ; 
next open the switch B, or otherwise add to the resistance r 2 until the deflec- 
tion V r of the voltmeter is produced ; call this added resistance r s , then 

If E be smaller than E u the voltmeter resistance R may be taken as r, and 
it is better to have r x about twice as large as the combined resistance of r 
and the resistance of A. 

It is not necessary that the internal resistance of the cells be small as 
compared with R. 



TESTS WITH A VOLTMETER. 



77 



Pog-gendorff's method Modified toy Clark. 

To Compare the E.M.F. of a battery cell or element with a standard cell. 
Let S he a standard cell, 

The a cell for comparison with the standard, 

^bea battery of higher E.M.F. than either of the above elements. 
A resistance r is joined in series with the battery B and a slide wire A D. 
A millivoltmeter is connected as shown, both its terminals being connected 
to the like poles of the battery B and the Standard St 




Fig. 50. 



Move the contact C along the wire until the pointer of the instrument 
stands at zero, and let r t be the resistance of A C. 

Throw the switch b so as to cut out the standard S, and cut in the cell T ; 
now slide the contact C x along the wire until the pointer again stands at 
zero, and call the resistance of A C x r 2 , 

Then the E.M.Fs. of the two cells 

T\ S ::r 2 :r v 

If a meter bridge or other scaled wire be used in place of A Z>, the results 
may be read directly in volts by arranging the resistance r so that with the 
pointer at zero the contact C is at the point 144 on the wire scale, or at 100 
times the E.M.F. of the standard S, which may be supposed to be a Clark 
cell. All other readings will in this case be in hundredths of volts ; and 
should the location of C, be at 175 on the scale when the pointer is at zero 
on the millivoltmeter then the E.M.F. of the cell, being compared, will be 
1.75 volts. 

Measuring* Current Strength with a Voltmeter. 

If the resistance of a part of an electric circuit be known, taking the drop 
in potential around such resistance will determine the current flowing by 

J? 

ohms law viz., J= — • . 
M 

In the figure let r be a known resistance be- 
tween the points A and B of the circuit, and / 
the strength of current to be determined ; then 
il the voltmeter, connected as shown, gives a 
deflection of V volts, the current flowing in r 

will be I— — , 

r 

For the corrections to be applied in certain 
cases, see the section on Importance of High 
Resistance for Voltmeters, page 75. 

Always see that the resistance r has enough 
carrying capacity to avoid a rise of temperature 
which would change its resistance. 

If the reading is exact to — volt the meas- 
urement of current will be exact to am- 

p Xr 




Fig. 51. 



78 



MEASUREMENTS. 



peres. If r ■» .5 ohm, and the readings are taken on a low-reading volt- 
meter, say ranging from to 5 volts, and that can be read to 3 ^ volt, then 
the possible error will be 

* 1 

300 X .5 
If rbe made equal to 1 ohm, then the volts read also mean amperes. 

Measurement of Current with a ^tillivoltnteter. — This is the 
method generally used in practice for the measurements of currents, and 
is the same principle as the one outlined above with the substitution of a 
millivoltmeter for the voltmeter. 

As the drop is much lower, a comparatively low resistance shunt may 
be used, so that heavy currents may be measured without the shunt becom- 
ing disproportionately large. 

For portable instruments, detachable shunts are generally adjusted with 
the instrument so that the instrument scale reads directly in amperes. The 
snunts are constructed of resistance alloy having a negligible temperature 
coefficient. 

Switchboard instruments also have shunts with slotted terminals so 
that they may be connected directly to the bus-bars. 

In some cases where the currents to be measured are very large the in- 
struments are adjusted to the drop across a portion of the copper bus-bar 
through which the current passes. To compute the length of the copper 
bar ofa given cross section to give a certain drop for a given current, 
let A = the area of the cross section of bar in square inches, 

/ = current in amperes, 

V = drop in millivolts desired for instrument for current I; 
a v y 119 
then, length in feet = * at 20° C. 

measuring: Resistance with a Voltmeter. 

General Methods. — In the figure, let X = the unknown resistance 
that is to be measured, r = a known resistance, E, the dynamo or other 
steady source of E.M.F. 

When connected as shown in the figure, let 
the voltmeter reading be V ; then connect the 
voltmeter terminals to r in the same manner 
and let the reading be V x ; then 

X:r:: V: V, 




and X = — ~ — . 

"\ 
If, for instance, r = 2 ohms and V = 3 volts 
and V x = 4 volts then 

x _2x_3_ 15ohms 
4 

If readings can be made to — volt, the error of resistance measurement 
will then be P 



Fig. 52. 



100 X p ( T + ~V\) P ercent ' 



and for the above example would be 

1 (i + i) = 0.58%. 
Should there be a considerable difference between the magnitudes of the 
two resistances X and r, it might be better to read the drop across one of 
them from one scale, and to read the drop across the other on a lower scale. 



Resistance Measurement with Voltmeter and Ammeter. 

The most common modification of the above method is to insert an am- 
meter in place of the resistance r in the last figure, in which case X=z-^ 
where /is the current flowing in amperes as read from the ammeter. 



TESTS WITH A VOLTMETER. 



79 



If the readings of the voltmeter be correct to — and the ammeter read- 
ings be correct to the same degree, the possible error becomes : 



100 X 



-f 1 



r+i) 



per cent. 





©. 


M.Vm, 
V 




L 




\ 


i 


X 


( 


m < 


n 


Am y 


L 


r 





Measurement of very Small Resistances with a Millivolt- 
meter and Ammeter. 

By using a millivoltmeter in connection with an ammeter, very small re- 
sistances, such as that of bars of copper, armature resistance, etc., can be 
accurately measured. 

In order to have a reas- 
onable degree of accuracy 
in measuring resistance by 
the " drop" method, as this 
is called, it is necessary 
that as heavy currents as 
may be available be used. 
Then, if E be the dynamo 
or other source of steady 
E.M.F., X be the required 
resistance of a portion of 
the bar, V be the drop 
in potential between the 
points a and 6, and I be 
the current flowing in the 
circuit as indicated by the 
FIG. 53. v ammeter, then 

x=- r 

The applications of this method are endless, and but a few, to which it is 
especially adapted, need be mentioned here. They are the resistance of 
armatures, the drop being taken from opposite commutator bars and not 
from the brush-holders, as then the brush-contact resistance is taken in ; the 
resistance of station instruments and all switchboard appliances, such as 
the resistance of switch contacts ; the resistance of bonded joints on electric 
railway work, as described in the chapter on railway testing. 

Measurement of High Resistances. 

"With the ordinary voltmeter of high internal resistance, let R be the re- 
sistance of the voltmeter, X be the resistance to be measured. Connect them 
up in series with some source of electro- 
motive force as in the following figure. 

Close the switch b, and read the voltage 
V with the resistance of the voltmeter 
alone in circuit ; then open the switch, 
thus cutting in the resistance X, and take 
another reading of the voltmeter, V r 

Then Xz=r(£—i\. 

If the readings of the voltmeter be cor- 
rect to - of a volt the error of the above 

V 

\ i y j- y \ 

result will be 100 x — tt rr Tr per cent. 

pVi \ V— r,J 

Very Hig-li Resistance. — For the measurement of very high resis- 
tances a more sensitive voltmeter will give much better results for the reason 
that the reading Vi when the switch b is opened, becomes so small with the 
ordinary voltmeter that the error is relatively very great. Instruments are 
on the market having a sensibility of 1600 ohms per volt or about 250,000 
ohms for 150 volts. 




FiCx. 54. 



80 



MEASUREMENTS. 



For example if x =» 1 megohm and an ordinary voltmeter be used 
R — 15,000 ohms for 150 volts, 
and E = 120 volts, 

T . . , , ER 120 X 15,000 , __. u 

V t would be =-—- = 1 nnn nnn , 1 _ - = 1.772 volts; 



while if 



' X + R 

R were 250,000 ohms, 

. , . 120 X 250,000 

Vi would be 



1,000,000 + 15,000 



= 24 volts, 



' 1,000,000 + 250,000 
that is with the high resistance instrument, with the same accuracy of 
the instrument scales, the percentage error is about ^ a s great as with the 
lower resistance instrument. 

Measuring- the Insulation Resistance of [Lighting* and 
Power Circuits with a Voltmeter. — For the measurement of in- 
sulation resistance, a high resistance sensitive voltmeter is needed. For 
rough measurements where the exact insulation resistance is not required 
but it is wished to determine if such resistance exceeds some stated figure, 
then a voltmeter of ordinary sensibility will answer. The methods in general 
are as follows : 

Let X = insulation resistance to ground as in Fig. 55, 

X t = insulation resistance to ground of opposite lead, 

R = resistance of voltmeter, 

V = potential of dynamo E, 

Vi = reading of voltmeter, as connected in figure, 

V2 — reading of voltmeter, when connected to opposite lead. 







Ground 

Fig. 55. 



Ground 



Then 



and 



X = R(f.-t), 



The above formula can be modified to give results more nearly correct by 
taking into account the fact that the path through the resistance R of the 
voltmeter is in parallel with the leak to ground on the side to which it is 
connected as shown in the following figure : 




^=Ground -=r 

Fig. 5G. 



TESTS WITH A VOLTMETER. 



81 



In this case the voltage V of the circuit will not only send current through 
the lamps, but through the leaks e f to ground, and through the ground to 
d and c, thence through d to ft, and c to a, these two last paths being in par- 
allel, therefore having less resistance than if one alone was used ; thus if r 
be the resistance of the ground leak b d, and r x be the resistance of the leak 
e /, and R be the resistance of the voltmeter, then the total resistance by 
way of the ground, between the conductors, would be 

R X r , 



and if 



Then 



and 



R + r 

V= voltage of the circuit, 
v = reading of voltmeter from a to c, 
v, = reading of voltmeter from g to c. 



i 



r,= B ( r -% + v '>). 



The sum of the resistance r -\-r x will be = R 



f (V + v,){V—(v + v,))\ 



Insulation Resistance of Arc liig-ht Circuits. 

Arc lamps are to a great extent run in series, and the insulation resis- 
tance of their circuits is found in a manner similiar to that for multiple 
circuits, but the formula differs a little. Let the following figure be a 
typical arc circuit, with a partial ground at c. 

First find the total voltage V between a and b of the circuit. This can 
most handily be done with a voltmeter having a high resistance in a sepa- 
rate box and so calibrated with the voltmeter as to multiply its readings by 




r Ground 
FlJT57. 



some convenient number. For convenience in locating the ground, get the 
average volts per lamp by dividing the total volts V by the number of lamps 
on the circuit ; the writer has found 48 volts to be a good average for the 
ordinary 10 ampere lamp. With the 16 lamps shown in the above figure, V 
would probably be about 768 volts. 

Next take a voltmeter reading from each end of the circuit to ground. 
Call the reading from a to ground v, and from b to ground v n R being the 
resistance of voltmeter as before, and r the insulation resistance required. 



Then 



— b( v -( v + v ' ) \ 



and the location of the ground, provided there be but one and the general 
insulation of the circuit be good, will be found closely proportional to the 
leadings v and v, ; in the above figure say we find the voltmeter reading 
from a to ground to be 28, and from b to ground to be 36 ; then the distance 
of the ground c from the two ends of the circuit will be in proportion to the 
leadings 28 and 36 respectively. 
There being 16 lamps on the circuit, the number of lamps between a and c 



82 



MEASUREMEN TS. 



would be 28 — (28 -f- 36) = §| of 16 = 7, and from b to c would be 36 - 
(28 + 36) = |f of 16 = 9 ; that is, the ground would most likely be found be- 
tween the seventh and eighth lamps, counting from a. 

Insulation across a Double Pole fuse Block or Other 

Similar Revice where Both Terminals are on 

the lame Base. 

Let// be fuses in place on a base, 

V= potential of circuit, 

R = resistance of voltmeter, 

v =z reading of voltmeter, 
required the resistance r across the base 
a a, to ft 6 t . 

Then r = jR ZjZf. 



Fig. 58. 
MEASUREMENT OF THE Il¥SITEATIO]¥ RESIS- 
TANCE OF AN ELECTRIC WIROG SYSTEM 
WITH THE POWER ON. 




The following methods have been devised by Dr. Edwin F. Northrup 
for the measurement of insulation resistance of a circuit where it is im- 
practicable to shunt off the current. 



1. — Voltmeter Method. 

Let A (Pig. 59) represent any wiring 
system in which X t and X 2 are the 
insulation resistances between the bus- 
bars, B± and B 2 and the earth (the 
gas or water pipes being taken as at 
the potential of the earth). In Fig. 59, 
J, 77, and 777 are equivalent diagrams 
in which y represents the unknown 
resistance of all the lamps, motors, 
etc., across the line. 

If direct current is supplied to the 
bus-bars, a direct-current voltmeter 
should be used. If the current is 
alternating, then an alternating-cur- 
rent voltmeter will be required. The 
resistances, X x and X 2y are determined 
by knowing g, the resistance of the 
voltmeter, and by taking three volt- 
meter readings. 

1st. Measure the voltage, which 
we will call E, across the bus-bars 
(Fig. 59) 7. 

2d. Connect the voltmeter be- 
tween the bus-bar, B lt and the earth 
and take its reading, which we will 
call V t (Fig. 59) 77. 

3d. Connect the voltmeter be- 
tween the bus-bar, B 2 , and the earth 
and take its reading, which we will 
call V 2 (Fig. 59) 777. 

If the readings in either of the two 
latter cases are only a fraction of a 
scale division, then the insulation re- 
sistance is too high to be measured by 
this method and we maj" resort to 



Bi 









c <^f READsE 




II B, 



^f REA DS Vj 



*i 



n£ reads Vo 



>AAA\AAV\AAAAAA/AA/1 



C 2 



1 1 

Fig. 59. Voltmeter Method. 



MEASURING INSULATION RESISTANCE. 83 



the second method to be described. Having taken the above three read- 
ings, it can be shown that 

X i ~ vt (1) 

x 2 - 'C*-r,-r,) . (2) 

The current /, which leaks to the ground will be, 

X x + X 2 

For example, the insulation resistance of the wiring system of a large 
office building was determined by means of a Weston voltmeter, the fol- 
lowing readings and resistances were obtained: 



Q = 
E = 

fc = 

v 12,220 (113 


12,220 ohms, 
113 volts, 
1 volt, 
4 volts. 

-1-4) , 


Xl ~ 4 
v 12,220 (113 

A 2 = 


-1-4) ] 



= 329,940 ohms, 
= 1,319,760 ohms. 

The above example shows that where the sum of the resistances, X x 
and X 2 , are not over one or two million ohms, the voltmeter method is 
sufficiently accurate for the purpose. If one side of the line is grounded — 
that is, if X 2 = — then from (2) E = V x + V 2 = V lf as V 2 = 0, and 
the method fails to give X lm 

Expressions (1) and (2) above are obtained as follows: The meaning of 
the letters used are indicated in /, II, and 77/ (Fig. 59), C lt C 2 , etc., being 
currents and g the resistance of the voltmeter. 

C,= 

c 2 = 



-*2~r ■ — 



X t - 

E 






Cl " F+xl Cl = 1 ' or Cl = "~ xT^ 
C * ""F=ra C, ~7 ' or ° 2 -~x7d 

Hence, we have the two relations, 

E « Zij£±Zl) , and E F 2 (g-rl2) > 

xr I qXi X t g v _t oX 2 X 2 g 

from which the values for X x and X 2 are obtained as given above in equa- 
tions (1) and (2). 

Any instrument, as a galvanometer, in which the deflections are pro- 
portional to the currents, may be substituted for a voltmeter. In such a 
case, if D, d*. and d 2 are deflections corresponding to the readings E, V lt 
and V 2 , and G is the total resistance in series with the instrument, we have 
as before: 

X, = G (D ~f x " d *> (3) 



and X 2 = g (Z) "/* - <* 2 ? (4) 



do 

- d 

d x 



84 



MEASUREMENTS. 



If two or more electric lamps are connected in series, their resistances, 
while carrying current, can be determined by means of three readings, 
as above. 

If X 2 — oo, V t — 0, and X t = — — T , — i which is the ordinary ex- 

2. 

pression used in measuring a resistance with a voltmeter by reading the 
voltmeter with the resistance in series with it and again with the resistance 
cut out. 

II. — Galvanometer Uletliocl. 

This method may be used when greater accuracy is required or when 
the insulation resistance to earth, of at least one side of the line, is over a 
megohm. 

The wiring system is represented in 1 of Fig. 60, and 2 of Fig. 60 gives 
equivalent circuits. 

The method consists in connecting across the bus-bars a moderately 
high resistance and rinding on this resistance a point, p, where the poten- 
tial due to the generator is the same as that of the earth, and then with 




Fig. 60. Galvanometer Method. 



the aid of a sensitive galvanometer and an external source of E.M.F., meas- 
uring the resistances, r t and r 2 , to earth in the following manner: & is a key 
and S an Ayrton universal shunt. This latter may be omitted if the source 
of E.M.F. can be varied in a known manner. 

It is evident from Fig. 60 that a balance will be had when - = — , the 

O To 

key, k, being in its upper position. If k is now depressed, the resistance, 
R, encountered by the current generated by the source, e, will be 



R - Ox + - 



1 



■ + 



b-\-r 2 a-\-r t 

where g t is the resistance of the galvanometer; but in comparison with 
rj and r 2t g lt a an: 1 b can be neglected, and 



R = 



nr 2 



By construction, — = 7 = TV, a known ratio. 
r 2 b 
tions we deduce 

m R(N+1) 
r 2 =- - 



From the last two rela- 



and 



N 

ri = R(N + 1). 



Taking d as the deflection of the galvanometer and K as the galvano- 
meter constant, the current through the galvanometer is 



e 

R 



d __ eK 



MEASURING INSULATION RESISTANCE. 85 

K should be defined as the resistance which must be inserted in circuit 
with the galvanometer (including its own resistance), so that it will give, 
with one volt, a scale deflection of one scale division at the distance at 
which the scale is placed from the mirror during the test, usually taken 
as one meter. 

Then we will have: 

eK {N + l) 



r 2 =" 



Nd 



, eK(N + l) 
and n = - d 

Taking K = 10 8 as an average value for an ordinary D'Arsonval gal- 
vanometer and e = 100, n = 2, and d = 100, we have: 

100X10 8 (2 + 1) tcn , 

r2 = 2^100 = 15 ° me * ohms ' 

100 X 10 8 (2 + 1) on „ , 

r, = Yqq — — = 300 me go hms - 

This example shows that a galvanometer of very moderate sensibility 
will measure in this way a very high insulation resistance. If, on the other 
hand, the insulation is low, small battery power may be used or the deflec- 
tion of the galvanometer can be cut down to xV» ihs, tsVo» or Totyou by the 
Ayrton shunt. The only difficulty likely to be experienced in applying 
the above method is that, while making the test, the relative values of r t 
and r 2 will keep changing, due to motors or lights being thrown on or off 
the line. In this event it is only possible to obtain a sort of average value 
for the resistance to earth of each side of the line. 



Insulation Resistance of £ lee trie Circuits in Building's. 

In the United States it is quite common to specify that the entire installa- 
tion when connected up shall have an insulation resistance from earth of at 
least one megohm. 

The National Code gives the following : 

The wiring of any building must test free from grounds ; i.e., each main 
supply line and every branch circuit should have an insulation resistance of 
at least 100,000 ohms, and the whole installation should have an insulation 
resistance between conductors and between all conductors and the ground 
(not including attachments, sockets, receptacles, etc.) of not less than the 
following : 

Up to 5 amperes . . 4,000.000. Up to 200 amperes . . 100,000. 

Up to 10 amperes . . 2,000,000. Up to 400 amperes . . 50,000. 

Up to 25 amperes . . 800,000. Up to 800 amperes . . 25,000. 

Up to 50 amperes . . 400,000. Up to 1,600 amperes . . 12,500. 

Up to 100 amperes . . 200,000. 

All cut-outs and safety devices in place in the above. 

Where lamp-sockets, receptacles, and electroliers, etc., are connected, 
one-half of the above will be required. 
Professor Jamison's rule is : 

E.M.F. 

Resistance from earth = 100,000 x r ^ . 

number of lamps 

Kempe's rule is : — 

75 

Resistance in megohms == — . 

number of lamps 

A rule for use in the U. S. Navy is : 

E.M.F. 



( 



Resistance = 300,000 x 



number of outlets 



$6 



MEASUREMENTS. 



Institution of Electrical Engineers' rule is : 
7900 X E.M.F. 



B= 



number of lamps 

Phoenix Fire Office rule for circuits of 200 volts is that 

._ , . „ 12.5 megohms 

the least E= r- ^ . 

number of lamps 

Twenty-five English insurance companies have a rule that the leakage 
from a circuit shall not exceed ^-J^ part of the total working current. 

Below is a table giving the approximate insulation allowable for circuits 
having different loads of lamps. 

For a circuit having — 

25 lamps, insulation should exceed . . 500,000 ohms. 

50 lamps, insulation should exceed . . 250,000 ohms. 

100 lamps, insulation should exceed . . 125,000 ohms. 

500 lamps, insulation should exceed . . 25,000 ohms. 

1000 lamps, insulation should exceed . . 12,000 ohms. 

All insulation tests of lighting circuits should be made with the working 
current. (See page 80, voltmeter test.) 

In the following table Uppenborn shows the importance of testing with 
tiie working voltage. 

Table I. shows the resistance between the terminals of a slate cut out. 

Table II. shows the resistance between two cotton-covered wires twisted. 



I. 


II. 


Volts. 


Megohms. 


Volts. 


Megohms. 


5 
10 
13.6 
27.2 


68 
53 
45 

24 


5 
10 
16.9 
27.2 


281 
188 
184 
121 



Measuring* the Insulation of Dynamos. 

The same formula as that used for measuring high resistances (see Fig. 
55) applies equally well to determining the insulation of dynamo conductors 
from the iron body of the machine. 




Fig. 61. 



Connect, as in Fig. No. 61, all symbols having the same meaning a3 
before. 
Let r = insulation resistance of dynamo, then 



«*(£-*)• 



MEASURING INSULATION RESISTANCE. 



87 



JtEeasuring* the Insulation Resistance of motors. 

Where motors are connected to isolated plant circuits with known high 
insulation, the formula used for insulation of dynamos applies ; but where 
the motors are connected to public circuits of questionable insulation it is 
necessary to first determine the circuit insulation, which can be done by 
using the connections shown in Fig. 56. Fig. 62 shows the connections to 
motor for determining its insulation by current from an operating circuit. 




Fig. 62. 
Here, as before, the insulation r of the total connected devices zr 

If r = total resistance of circuit and motor in multiple to ground, and r t 
is the insulation of the circuit from ground, then X, the insulation of the 



motor will be 



X=' 



Measurement of the Internal Resistance of a Battery. 

In the following figure (No. 63), let E be the cell or battery whose resistance 

is to be measured, K be a switch, and 
r a suitable resistance. 
Let V = the reading of voltmeter 
with the key, K y open 
(this is the E.M.F. of the 
battery), and 
V t = the reading of voltmeter 
with key, K, closed (this 
is the drop across the re- 
sistance r), 
Then the battery resistance 

Z±It. 

r. 

The same method can be used to measure the internal resistance of 
dynamos. An ammeter may be connected in the r circuit, in which case 
V-Vi. 




Fig. 63. 



*V = r X 



- ohms. 



r t = 



■ where / is the reading in amperes. 



Conductivity with a Millivoltmeter. 

This is a quick and convenient method of roughly comparing the conduc- 
tivity of a sample of metal with that of a standard piece. 

In Fig. 64, R is a standard bar of copper of 100% conductivity at 70° F.; 
this bar may be of convenient length for use in the clamps, but of known 
cross section. X is the piece of metal of unknown conductivity, but of the 



88 



MEASUREMENTS. 



I 



same cross section as the standard, j^isa source of steady current, and if 
a storage battery is available it is much the better for the purpose. M is a 
milhvoltmeter with the contact device d. The distance apart of the two 
points may be anything, so long as it remains unaltered and will go between 
the clamps on either of the bars. 

Now with the current howing through the two bars in series the fall of 
potential between two points the same distance apart and on the same flow- 




FlG, 64. 



line will, on either bar, be in proportion to the resistance, or in inverse pro- 
portion to the conductivity ; therefore by placing the points of d on the bars 
in succession, the readings of the millivoltmeter will give the ratio of the 
conductivities of the two pieces. 

For example : 
if the reading from R — 200 millivolts, 

and the reading from X=z 205 millivolts, 

then the percentage conductivity of X as compared with R is 
205 : 200 : : 100 : conductivity of X, 

200 X 100 or7 _~ 
or 2Q5 - = 97-50. 



MAGNETIC PROPERTIES OP IRON. 

Revised by Townsend Wolcott. 

With a given excitation the flux $ or flux-density (E of an electromagnet 
will depend upon the quality of the iron or steel of the core, and is usually 
rated as compared with air. 

If a solenoid of wire be traversed with a current, a certain number of 
magnetic lines of force, J£> will be developed per square centimetre of the 
core of air. Now, if a core of iron be thrust into the coil, taking the place of 
the air, many more lines of force will flow ; and at the centre of the solenoid 
these will be equal to (& lines per square centimetre. 

As iron or steel varies considerably as to the number of lines per square 
centimetre (ft which it will allow to traverse its body with a given excitation, 
its conductivity towards lines of force, which is called its permeability , is 
numerically represented by the ratio of the flux-density when the core is 
present, to the flux-density when air alone is present. This permeability 
is represented by /u.. 

The permeability /u. of soft wrought iron is greater than that of cast iron ; 
and that for mild or open-hearth annealed steel castings as now made for 
dynamos and motors is nearly, and in some cases quite, equal to the best 
soft wrought iron. 

The number of magnetic lines that can be forced through a given cross- 
section of iron depends, not only on its permeability, but upon its satura- 
tion. For instance, if but a small number of lines are flowing through the 
iron at a certain excitation, doubling the excitation will practically double 
the lines of force ; when the lines reach a certain number, increasing the 
excitation does not proportionally increase the lines of force, and an excita- 
tion may be reached after which there will be little if any increase of lines 
of force, no matter what may be the increase of excitation. 

Iron or steel for use in magnetic circuits must be tested by sample before 
any accurate calculations can be made. 



< 



Data for (ft-3C Curves. 

Average First Quality American Metal. 

(Sheldon.) 





A 


,d 


Cast Iron. 


Cast Steel. 


Wrought Iron 


Sheet Metal. 




Ampere 

turns pe 

cent, leng 


Ampere 
turns pe 
inch leng 


















JC 


i o 

©33 


Kilomax- 

wells per 

sq. in. 


GO 

1 0) 

©31 


Kilomax- 

wells per 

sq. in. 


03 

tx 


Kilom ax- 
wells per 
sq. in. 




Kilomax- 

wells per 

sq. in. 


10 


7.95 


20.2 


4.3 


27.7 


11.5 


74.2 


13.0 


83.8 


14.3 


92.2 


20 


15.90 


40.4 


5.7 


36.8 


13.8 


89.0 


14.7 


94.8 


15.6 


100.7 


30 


23.S5 


60.6 


6.5 


41.9 


14.9 


96.1 


15.3 


98.6 


16.2 


104.5 


40 


31.80 


80.8 


7.1 


45.8 


15.5 


100.0 


15.7 


101.2 


16.6 


107.1 


50 


39.75 


101.0 


7.6 


49.0 


16.0 


103.2 


16.0 


103.2 


16.9 


109.0 


60 


47.70 


121.2 


8.0 


51.6 


16.5 


106.5 


16.3 


105.2 


17.3 


111.6 


70 


55.65 


141.4 


8.4 


53.2 


16.9 


109.0 


16.5 


106.5 


17.5 


112.9 


80 


63.65 


161.6 


8.7 


56.1 


17.2 


111.0 


16.7 


107.8 


17.7 


114.1 


90 


71.60 


181.8 


9.0 


58.0 


17.4 


112.2 


16.9 


109.0 


18.0 


116.1 


100 


79.50 


202.0 


9.4 


60.6 


17.7 


114.1 


17.2 


110.9 


18.2 


117.3 


150 


119.25 


303.0 


10.6 


68.3 


18.5 


119.2 


18.0 


116.1 


19.0 


122.7 


200 


159.0 


404.0 


11.7 


75.5 


19.2 


123.9 


18.7 


120.8 


19.6 


126.5 


250 


198.8 


505.0 


12.4 


80.0 


19.7 


127.1 


19.2 


123.9 


20.2 


130.2 


300 


238.5 


606.0 


13.2 


85.1 


20.1 


129.6 


19.7 


127.1 


20.7 


133.5 



J€ = 1.257 ampere turns per cm. = .495 ampere turns per inch 



90 



MAGNETIC PROPERTIES OF IRON. 



i O 







T 












1 


























\\ 
































































































































































\\ 








































Ice 














!\ 


























,1 














ft 


























"Pi 

- Id— 












o 


\ 
























_JJ! 






















































\ 
























f\\ 














\ 
























H 














\ 
























! 














1 


I 






















IV 
















\ 






















-M \ 
















\ 






















h-1 
















\ 






































\ 






















«\ 
















\ 








































\ 








































\ 
























\\ 
















\ 


\ 






















V 


















\ 






















\ 


















\ 






















\ 




















\ 






















\ 


















\ 






















\ 








































\ 














































































































© 


s 


° 


a 


3 r~ 


<£ 


IT 


-n 


M 


<N 


» 


i 


D C 




o r 










o cm 



< 


< 


* 


O 

If. 


CO 

o 


a 

CM 

K3 


C5 


O 
cc 


r~ 


C 
* 


O 


o 

o 


* 


o 


CO 
OJ 


CM 


2 


c 

CM 


s 


o 

CM 


o 


c 

c 

CM 


^ 


o 




*~ 


CO 


o 

CM 


s 


o 


£ 


o 

t 



honi abvnos uad s-na/Axvwo iim 



Fig. 1. Magnetic Properties of Iron. 



MAGNETIC TEST METHODS. 



91 



In large generators, having toothed armatures and large flux densities in 
the air-gap, the flux is carried chiefly by the teeth. This results in a very 
high tooth flux density, and a correspondingly reduced permeability. The 
related values of (ft, JC, and ^ are given in the following table. These 
values are for average American sheet metal. 

Permeability at High Flux Densities. 





Ampere 


Ampere 


(B 


Kilomax- 




JC 


Turns per 


Turns per 


Kilo- 


wells per 


t* 




cm. Length. 


Inch Length. 


gausses. 


Square in. 




200 


159 


404 


19.8 


127 


99.0 


400 


318 


808 


21.0 


135 


52.5 


600 


477 


1212 


21.5 


138 


35.8 


800 


637 


1616 


21.8 


140 


27.3 


1000 


795 


2020 


22.0 


142 


22.0 


1200 


954 


2424 


22.3 


144 


1.8 


1400 


1113 


2828 


22.5 


145 


1.6 



i 



METHODS OJF mETEmCIXJHrG- THE JttAOHTETIC 

«H AIJTIE* OJF UtOA A1¥I> HEEL 

The methods of determining the magnetic value of iron or steel for elec- 
tro-magnetic purposes are divided by Prof. S. P. Thompson into the follow- 
ing classes : Magnetometric, Balance, Ballistic, and Traction. 

The first of these methods, now no longer used to any extent, consists in 
calculating the magnetization of a core from the deflection of a magneto- 
meter needle placed at a fixed distance. 

In the Balance class, the deflection of the magnetometer needle is bal- 
anced by known forces, or the deflection due to the difference in magnetiza- 
tion of a known bar and of a test bar is taken. 

The Ballistic method is most frequently used for laboratory tests, and for 
such cases as require considerable accuracy in the results. There are really 
two ballistic methods, the Ring method and the Divided-bar method. 

In either of these methods the ballistic galvanometer is used for measur- 
ing the currents induced in a test coil, by reversing the exciting current, or 
cutting the lines of force. 

Ring: method. — The following cut shows the arrangement of instru- 
ments for this test, as used by Prof. Rowland. The ring is made of the 
sample of iron which is to undergo test, and is uniformly wound with the 

BALLISTIC 
... GALVANOMETER 




FIG. 2. Connections for the Ring Method. 

exciting coil or circuit, and a small exploring coil is wound over the excit- 
ing coil at one point, as shown. The terminals of the latter are connected 
to the ballistic galvanometer. 



92 



MAGNETIC PROPERTIES OF IKOX. 



The method of making a test is as follows : — 

The resistance, i?, is adjusted to give the highest amount of exciting cur- 
rent. The reversing switch is then commutated several times with the gal- 
vanometer disconnected. After connecting the galvanometer the switch is 
suddenly reversed, and the throw of the galvanometer, due to the reversal 
of the direction of magnetic lines, is recorded. The resistance, i?, is then 
adjusted for a somewhat smaller current, Avhich is again reversed, and the 
galvanometer throw again recorded. The test is carried on with various 
exciting currents of any desired magnitude. In every case the exciting cur- 
rent and the corresponding throw of the galvanometer are noted and 
recorded. 

If iz=i amperes flowing in the exciting coil, 

n l = number of turns of wire in exciting coil, 
/ = length in centimetres of the mean circumference of the ring, 
then the magnetizing force 

nr . 47r ii x i . ___ nd 
5C ~To x T~ or ^ 7x ~f' 
If I" — length of the ring in inches, then 

JC"=.495X %. 

If 9 =z the throw of the galvanometer, 
K= constant of the galvanometer, 
i? = resistance of the test coil and circuit, 
n 2 = number of turns in the test coil, 
a = area of cross-section of the ring in centimetres, then 

^ 10 8 RKQ 
*** 2 an 2 

To determine K, the constant of the galvanometer, discharge a condenser 
of known capacity, which has been charged to a known voltage, through it. 
and take the reading 1 , then 



If 



c z=z capacity of the condenser in microfarads, 

e = volts pressure to which the condenser is charged, 



coulombs is Q = 



then the quantity passing through the galvanometer upon discharge in 
c e 
1,000,000' 
and the galvanometer constant 
c e 



K- 



1,000,000 e 1 



IMvided-Bar TOethod. 

obtain samples in the form of 
a ring, and still more incon- 
venient to wind the coils on it, 
Hopkinson devised the di- 
vided-bar method, in which 
the sample is a long rod \" 
diameter, inserted in closely 
fitting holes in a heavy 
wrought iron yoke, as shown 
in Fig. 3. 

In the cut the exciting coils 
are in two parts, and receive 
current from the battery and 
through the ammeter, resist- 
ance, and reversing switch, 
as shown. 



-As it is often inconvenient or impossible to 

AMMETER 
DIVISION IN 

V TEST PIECE 




V TO V-,MEAN_lENGT.H 
, L-OF TEST PIECgl 
BALLISTIC^ 
GALVANOMETER . ., 

Fig. 3. Arrangement for Hopkinson s di- 
vided-bar method of measuring permea- 



The test bar is divided near the centre at the point indicated in the cut, 
and a small light test coil fo placed over it, and so arranged with springs as 



MAGNETIC TEST METHODS. 



93 



to be thrown clear out of the yoke when released by pulling out the loos* 

end of the test bar by the handle shown. 

In operation, the exciting current is adjusted by the resistance B, the test 
bar suddenly pulled out by the handle, thus releasing the test coil and pro- 
ducing a throw of the galvanometer. As the current is not reversed, the 
induced pressure is due to N only, and the equation for (ft is 



(B = 1 and 



IP — ^ v n ^ 
^-10 X L 



: 1.257 ^\ 



Where L = the mean length of the test rod as shown in the cut. 

In using the divided-bar method, a correction must be made, for the rea- 
son that the test coil is much larger than the test rod, and a number of 
lines of force pass through the coil that do not through the rod. This cor- 
rection can easily be determined by taking a reading with a wooden test 
rod in place of the metal one. 

An examination of the cut will show that the bar and yoke can also be 
used for the method of reversals. 

IVEag-iietic Square Method. — G. F. C. Searle (Journal I. E. E., 
December, 1904), has suggested another method of avoiding the use of the 
Rowland ring arrangement. The apparatus consists of a square, with strips 
laid overlapping at the edges. To obtain accurate results, the dimensions 
of the square must be large, as compared with the width of the strips. The 
same is true, but in a somewhat less degree, with the Rowland ring. 
According to A. Press, when the relative dimensions are correctly adjusted 
the ballistic galvanometer will give repeatable results, if the iron be first 
effectively demagnetized by means of an alternating current gradually 
reduced to zero, and then subjected to a series of reversals, from 50 to 200 
with normal magnetizing current, before actual readings are taken. 



Traction Method. 

The following cut shows the method with sufficient clearness. A heavy 
yoke of wrought iron has a small hole in one end through which the test 

rod is pushed, through the exciting coil 
shown, and against the bottom of the 
yoke, which is surfaced true and smooth, 
as is the end of the test rod. 

In operation, the exciting current is ad- 
justed by the resistance R, and the spring 
balance is then pulled until the sample or 
test rod separates from the yoke, at which 
time the pull in pounds necessary to pull 
them apart is read. Then 



SPRING 
BALANCE 




(B = 1,317 X 



v/5 +JC - 



Where P = pull in pounds as shown on 
the balance, 

A z=z area of contact of the rod 
and yoke in square inches. 
3C is found as in the Hopkinson method 
preceding this. 

Following is a description of a practical adaptation of the permeameter to 
shop-work as used in the factory of the Westinghouse Electric and Manu- 
facturing Co. at Pittsburgh, Pa. 



Fig. 4. S. P. Thompson's per- 
meameter. 



94 MAGNETIC PROPERTIES OF IRON. 

Tlie Permeameter, as used by toe Westing-house Electric 
and Mfgr. Co» 

Design and Description prepared by Mr. C. E. Skinner. 

A method of measuring the permeability of iron and steel known as the 
11 Permeameter Method " was devised by Prof. Silvanns P. Thompson, and is 
based on the law of traction as enunciated by Clerk Maxwell. According to 
this law the pull required to break any number of lines of force varies as the 
square of the number of lines broken. (A complete discussion of the theory 
of the permeameter, with the derivation of the proper formula for calculating 
the results from the measurements will be found in the " Electro Magnet,'* 
by Prof. S. P. Thompson.) 

A permeameter which has been in use for several years in the laboratory 
of the Westinghouse Electric and Manufacturing Company, and which has 
given excellent satisfaction, is shown in Figs. 5 and 6. The yoke, .4, 
consists of a piece of soft iron 7" x 8h" x 2J", with a rectangular open- 
ing in the center c l\" x 4". The sample, X, to be tested is §" in diam- 
eter and 7|" long, and is introduced into the opening through a § " hole in the 
yoke, as shown in the drawing. The test sample is finished very accurately to 
§" in diameter, so that it makes a very close tit in the hole in the yoke. The 
lower end of the opening in the yoke and the lower end of the sample are 
accurately faced so as to make a perfect joint. The upper end of the sam- 
ple is tapped to receive a \" screw §" long, twenty threads per inch, by 
means of which a spring balance is attached to it. The magnetizing coil, G\ 
is wound on a brass spool, S, 4" long, with the end flanges turned up so that 
it may be fastened to the yoke by means of the screws. The axis of the coil 
coincides with the axis of the yoke and opening. The coil has flexible leads, 
which allow it to be easily removed trom the opening for the inspection of 
the surface where contact is made between the yoke and the test sample. 

The spring balance, JF, is suspended from an angle iron fastened to the up- 
right rack, /, which engages with the pinion, J. The balance is suspended 
exactly over the centre of the yoke through which the sample passes, to 
avoid any side pull. A spring buffer, K. is provided, which allows perfectly 
free movement of the link holding the sample for a distance of about §", 
and then takes up the jar consequent upon the sudden release of the sample. 
The frame, B, which supports the pulling mechanism, is made of brass, and 
has feet cast at the bottom, by means of which the complete apparatus is 
fastened to the table. Two spring balances are provided, one reading to 30 
lbs. and the other to 100 lbs. These spring balances are of special construc- 
tion, having comparatively long scales. (They were originally made self- 
registering ; but this was found unnecessary, as a reading could be taken 
with greater rapidity and with sufficient accuracy without the self-register- 
ing mechanism.) Any good spring balance may be used. The spring should 
be carefully calibrated from time to time over its whole range ; and if there 
is a correction it will be found convenient to use a calibration curve in cor- 
recting the readings. With a sample f" in diameter, or § of a square inch 
area cross-section, the maximum pull required for cast iron is about 25 lbs., 
and for mild cast steel about 70 lbs. 

With the number of turns on the coil given above, the current required 
for obtaining a magnetizing force of JC= 300, is about 12.5 amperes. This 
is as high a value as is ever necessary in ordinary work. For furnishing the 
current a storage battery is ordinarily used, and the variations made by 
means of a lamp board which has in addition a sliding resistance, so that 
variations of about .01 ampere may be obtained over the full range of cur- 
rent from 0.1 ampere to 12.5 amperes. 

The operation of the permeameter is as follows : — 

The sample to be tested is first demagnetized by introducing it into the 
field of an electro-magnet with a wire core, through which an alternating 
current is passing, and gradually removing it from the field of this electro- 
magnet. The sample is then introduced into the opening in the yoke, care 
being taken to see that it can move without friction. Measurements are 
taken with the smallest current to be used first, gradually increasing 
to the highest value desired. In no case should a reading be taken with a 
current of less value than has been reached with the sample in position, 
unless the sample is thoroughly demagnetized again before reading is taken. 
It is usually most convenient to make each successive adjustment of cur- 



THE PERMEAMETER. 



95 



rent with the sample out of position, then introduce the sample and give it 
a half turn, to insure perfect contact between the sample and the yoke. The 
lower end of the sample and the surface on which it rests should he care- 
fully inspected to see that no foreign matter of any kind is present which 
might introduce serious errors in the measurements. The pull is made by 
turning the pinion slowly by means of a handle, E, carefully noting each 






o 


fflj 




<§B= <§» h 


4j 




LLs / 






J . r 


o 1 


o x^ 


) 



i 




Coil and Shell 

Fig. 5. 

position of the index of the spring balance as it advances over the scale, 
and noting the point of release. The mean of three or four readings is 
usually taken as the corrected value for pull, the current in the coil remain- 
ing constant. With practice the spring balance can be read to within less 
than 1%; and as the square root of the pull is taken, the final error become3 
quite small, especially with high readings. 



96 



MAGNETIC PROPERTIES OF IRON. 



The evaluation of the results for the above permeameter is obtained by 
the use of the following formula : 



The magnetizing force JC = n . 



10 I 

Where 7^ = number of turns in the magnetizing coil = 223, 

i = current in amperes, 

j = length of magnetic circuit in centimeters, estimated in this 
case as 11.74. 
Substituting the known values in the above formula we have 

3C = 23.8i. 




Fig. 6. 



The number of lines of force per square centimeter 



i =r 1,317 



V3 + 3C 



Where P = pull in lbs. 

y4 = area of the sample in square inches = 0.3068. 
JC = value of the magnetizing force for the given pull. 



THE PERMEAMETER. 97 

Substituting the value of A in the above formula we have 

(B = 2,380 Vp + X 

There are several sources of error in measurements made by the permea- 
meter which should be carefully considered, and eliminated as far as possible. 

a. The unavoidable air gap between the sample and the yoke where it 
passes through the hole in the upper part of the yoke, together with the 
more or less imperfect contact at the lower end of the sample, increases the 
magnetic reluctance and introduces errors for which it is impossible to make 
due allowance. By careful manipulation, however, these can be reduced 
to a minimum, and be made practically constant. 

b. As the magnetization becomes greater the leakage at the lower end of 
the sample increases more rapidly; and there is considerable error at very 
high values from this source, as the leakage lines are not broken with the 
rest. 

c. Errors in the calibration and reading of the spring balance. None 
but the best quality of spring balance should be used, and the average of 
several readings taken with the current remaining perfectly constant for 
each point on the (B _ JC curve. As the square root of the pull is taken, the 
errors due to reading the spring balance make a larger and larger percent- 
age error in (gasP approaches zero, thus preventing accurate determina- 
tions being made at the beginning of the curve. 

From the above it will be seen that the permeameter is not well adapted 
for giving the absolute values of the quality of iron and steel, but is especially 
suitable for comparative values, such as are noted in ordinary work, where 
a large number of samples are to be quickly measured. A complete curve 
can be taken and plotted in ten minutes. By suitable comparison of known 
samples measured by more accurate methods, the permeameter readings may 
be evaluated to a sufficient degree for use in the calculations of dynamo 
electric machinery. 

Drysdale's Permeameter, 

This instrument is designed to enable one to test the magnetic quality 
of iron or steel magnet castings and forgings under commercial conditions, 
by drilling it with a special drill. A testing plug is inserted in the hole 
thus drilled and the magnetization or permeability is then directly meas- 



Fig. 7. 

ured on an instrument attaehed, without any calculations, by simply 
throwing over a reversing switch. 

Fig. 7 shows the special form of drill employed. It has four cutting 
edges at the lower end, which cut a cylindrical hole in the specimen. The 
drill is, however, made hollow, so that a thin rod or pin of the material is 
left standing in the center of the hole, as shown in Fig. 8, which shows a 
cast steel pole piece, and some small specimens of iron and steel actually 
drilled. In addition, cutting edges are provided at the top of the drill, 
which give a conical shape to the top of the hole drilled. The hole is 
about f in. deep and ^ in. in its largest diameter, while the pin is T V in. in 
diameter. Such a hole may be drilled in any position where a bolt hole is 
afterwards to be made in the back of a pole piece, or face of a joint, or 
otherwise in projections left specially for the purpose, which may be cut 
off the casting or forging on delivery and sent to the test room. 



98 



MAGNETIC PROPERTIES OP IRON. 




Fig. 8. Specimens Showing Holes and Pins. 



In this hole is inserted the testing plug, Fig. 9, which consists of a soft 
iron plug, accurately fitting the conical portion of the hole cut by the drill, 
and having a central hole fitting over the pin. The plug is also split length- 
wise, so that on forcing it into the conical 
hole the sides yield slightly and grip the pin, 
so making a very perfect magnetic joint. 
If the pin is magnetized the lines of force 
pass through the pin into the plug, and 
thence round the mass of the metal to the 
pin again, as shown in Fig. 9. The pin is 
magnetized by current in a coil wound 
round it, and the magnetization produced 
is tested by use of a second or search coil. 
On making or breaking or reversing the 
current in the first or magnetizing coil, the 
lines of force passing through the search 
coil are altered, and if this coil is connected 
to a galvanometer, kicks or throws of the 
galvanometer will be obtained proportional 
to the change in the magnetization of the 
pin. 

CORE BOSSES. 

These result from Hysteresis and Eddy Fig. 9. Section through Plug 
currents. > and Specimen. 

Professor Ewing has given the name 
Hysteresis to that quality in iron which 

causes the lagging of the induction behind the magnetic force. It causes 
a loss when the direction of the induction is reversed, and results in a 
heating of the iron. It increases in direct proportion to the number of 
reversals, and according to Steinmetz, as the 1.6th power of the maximum 
value of the induction in the iron core. The heat produced has to be dissi- 
pated either by radiation or conduction, or by both. Steinmetz gives the 
following formula for hysteresis loss in ergs per cubic centimeter, of iron 
per cycle; h = -q (fomax 1 - 6 , where i? = a constant depending upon the kind 
of iron. Taking -q at .002 and retaining (B in gausses, the loss in watts per 
cubic inch of material Ph will be, Ph -.338 (ftma* 1 - 6 / 10"*, in which /= 
cycles per second. 




CORE LOSS. 



99 



It is to be observed that, in practice, considerable variations in the mag- 
netic density take place in parts where the magnetomotive force is a con- 
stant, due to the differences in the lengths of the lines of flux. This will not 
only affect the measured hysteresis losses, but the eddy currents as well. 
For this reason, machines of geometrically different form will not obey 
quite the same law of losses. Considerable question has been raised 
regarding the constancy of the hysteresis index. According to A. Press, 
the experiments of Mordey and Hansard with transformer iron imply that 
the hysteresis index for the range taken should be at least 2. Lancelot 
Wild gave the index as 2.7 for densities varying from (ft = 200 to 05 = 400, 
W. E. Sumpner states that the index varies 1.475 to 2.7, depending 
upon the range of the density, and Prof. Ewing gives the index as varying 
from 1 .9 to 2 with densities (E = 200 to (ft = 500, depending upon the 
sample. 

Hysteretic Constants for Different Materials. 



Material. 


Hysteretic Constant. 

v. 


Best annealed transformer sheet metal . . 
Very soft iron wire 


.001 
.002 


Thin good sheet iron 


.003 


Thick sheet iron 


.0033 


Most ordinary sheet iron 

Transformer cores 


.004 
.003 


Soft annealed cast steel 


.008 


Soft machine steel 


.0094 


Cast steel 


.012 


Cast iron 


.016 


Hardened cast steel 


.025 



Hysteresis I^oss JFactors. 



®>maz 


^max 1 ' 6 


^ma, 1 ' 6 


in Gausses. 


r?= 0.002 


V = 0.003 


>? = 0.004 


1,000 


63,100 


126 


189 


252 


2,000 


191,300 


382 


573 


765 


3,000 


365,900 


731 


1,096 


1,463 


4,000 


580,000 


1,160 


1,740 


2,320 


5,000 


828,800 


1,657 


2,486 


3,315 


6,000 


1,111,000 


2,222 


3,333 


4,444 


7,000 


1,420,000 


2,840 


4,260 


5,680 


8,000 


1,758,000 


3,516 


5,274 


7,032 


9,000 


2,122,000 


4,244 


6,366 


8,488 


10,000 


2,511,000 


5,022 


7,533 


10,044 



Eddy Currents are the local currents in the iron core caused by the E.M.F.'s 
generated by moving the cores in the field, and increase as the square of the 
number of revolutions per second. The cure is to divide or laminate the 
core so that currents cannot flow. These currents cause heating, and unless 
the core be laminated to a great degree are apt to heat the armature core so 
much as to char the insulation of its windings. 

Wiener gives tables showing the losses by Hysteresis and Eddy currents 
at one cycle per second, under different conditions. These are changed 
into any number of cycles by direct proportion. The formula for eddy 
current loss is: 

p e = 42 &" 2 fP 10~ 18 , 

in which Pe = watts per cu. in., Qfamax" — = maximum value of the magnetic 
density per sq. in., t = thickness of plate in mils, and/ = frequency. 



100 



MAGNETIC PROPERTIES OF IRON. 



Hysteresis factors for Different Core Densities. 



S? H -* 
~ £ 2 



* H «. 
w o w 

< 3 fe 
S3 



Watts dissipated at a 
Frequency of One 
Complete Magnetic 
Cycle per Second. 



V = .002 



10,000 
15,000 
20,000 
25,000 
30,000 
31,000 
32,000 
33,000 
34,000 
35,000 
36,000 
37,000 
38,000 
39,000 
40,000 
41,000 
42,000 
43,000 
44,000 
45,000 
46,000 
47,000 
48,000 
49,000 
50,000 
51,000 
52,000 
53,000 
54,000 
55,000 
56,000 
57,000 
58,000 
59,000 
60,000 
61,000 
62,000 
63,000 
64,000 
65,000 



Per 

cu. ft. 



713 

37 

16 

09 

06 

39 

4.62 

4.85 

5.08 

5.32 

5.56 

5.82 

6.08 

6.30 

6.59 

6.87 

7.11 

7.39 

7.67 

7.95 

8.24 

8.53 

8.81 

9.10 

9.40 

9.70 

10.00 

10.31 

10.68 

10.98 

11.28 

11.60 

11.94 

12.27 

12.61 

12.95 

13.30 

13.63 

13.99 

14.31 



Per 
lb. 



.0015 
.0027 
.0045 
.0064 
.0086 
.0091 
.0096 
.0101 
.0106 
.0111 
.0116 
.0121 
.0126 
.0131 
.0136 
.0142 
.0148 
.0154 
.0160 
.0166 
.0172 
.0178 
.0184 
.0190 
.0196 
.0202 
.0208 
.0214 
.0221 
.0228 
.0235 
.0242 
.0249 
.0256 
.0263 
.0270 
.0277 
.0284 
.0291 
.0298 



V = .003 



Per 

cu. ft. 



1.069 

2.055 

3.24 

4.64 

6.09 

6.59 

6.93 

7.28 

7.62 

7.98 

8.34 

8.73 

9.12 

9.45 

9.89 

10.31 

10.67 

11.09 

11.51 

11.93 

12.36 

12.80 

13.22 

13.65 

14.10 

14.55 

15.00 

15.46 

15.97 

16.47 

16.92 

17.40 

17.91 

18.41 

18.91 

19.42 

19.95 

20.45 

20.98 

21.47 



Per 

lb. 



.0023 
.0041 
.0068 
.0096 
.0129 
.0137 
.0144 
.0152 
.0159 
.0167 
.0174 
.0182 
.0189 
.0197 
.0204 
.0213 
.0222 
.0231 
.0240 
.0249 
.0258 
.0267 
.0276 
.0285 
.0294 
.0303 
.0312 
.0321 
.0332 
.0342 
.0353 
.0363 
.0374 
.0384 
.0395 
.0405 
.0416 
.0426 
.0437 
.0447 



5 w ^ 

- & fc 

2 H « 

L£J ID K 

£ £ o 

< S fc 



66,000 
67,000 
68,000 
69,000 
70,000 
71,000 
72,000 
73,000 
74,000 
75,000 
76,000 
77,000 
78,000 
79,000 
80,000 
81,000 
82,000 
83,000 
84,000 
85,000 
86,000 
87,000 
88,000 
89,000 
90,000 
91,000 
92,000 
93,000 
94.000 
95,000 
96,000 
97,000 
98,000 
99,000 
100,000 
105,000 
110,000 
115,000 
120,000 
150,000 



Watts dissipated at a 
Frequency of One 
Complete Magnetic 
Cycle per Second. 



V = .002 



Per 

cu. ft. 



14.68 
15.01 
15.39 
15.76 
16.13 
16.50 
16.87 
17.25 
17.61 
17.99 
18.41 
18.78 
19.19 
19.58 
19.93 
20.37 
20.77 
21.18 
21.60 
21.98 
22.40 
22.85 
23.26 
23.65 
24.10 
24.51 
24.97 
25.41 
25.86 
26.30 
26.84 
27.30 
27.73 
28.19 
28.55 
30.86 
33.20 
35.70 
38.20 
40.83 



Per 
lb. 



.0305 
.0313 
.0321 
.0329 
.0337 
.0345 
.0352 
.0360 
.0368 
.0376 
.0384 
.0392 
.0400 
.0408 
.0416 
.0424 
.0432 
.0440 
.0448 
.0456 
.0465 
.0474 
.0483 
.0492 
.0501 
.0510 
.0519 
.0528 
.0538 
.0548 
.0558 
.0568 
,0578 
0588 
0598 
0643 
0694 
0746 
0796 
0850 



V = .003 



Per 

cu. ft. 



22.02 
22.52 
23.05 
23.64 
24.19 
24.75 
25.31 
25.88 
26.41 
26.99 
27.62 
28.17 
28.78 
29.37 
29.90 
30.55 
31.15 
31.77 
32.40 
32.98 
33.60 
34.27 
34.87 
35.47 
36.15 
36.76 
37.44 
38.11 
38.79 
39.45 
40.26 
40.95 
41.59 
42.28 
42.85 
46.29 
49.80 
53.55 
57.30 
60.25 



CORE LOSS. IQl 

The Step-oy-Step method of Hysteresis Test. 

The samples for hysteresis tests, being generally of sheet iron, are made 
in the form of annular disks whose inner diameters are not less than § of 
their external diameter. A number of these disks are stacked on top of 
each other, and the composite ring is wound with one layer of wire form- 
ing the magnetizing coil of n x turns. This coil is connected through a re- 
versing switch to an ammeter in series with an adjustable resistance, and a 
storage battery. A secondary test coil of n 2 turns is connected with a bal- 
listic galvanometer, as shown in Fig. 10. 

BALLISTIC 

GALVANOMETER 



( 




Fig. 10. 

To make the test, adjust the resistance for the maximum exciting current. 
Reverse the switch several times, the galvanometer being disconnected. 
Then connect the galvanometer, and reduce the current by moving the con- 
tact arm of the rheostat up one step. This rheostat must be so constructed 
that an alteration in resistance can be made without opening the circuit even 
for an instant. Note the throw in the galvanometer corresponding to the 
change in exciting current. Follow this method by changing resistance 
step-by-step until the current reaches zero. Reverse the direction, and in- 
crease step-by-step up to a maximum and then back again to zero. Reverse 
once more, and increase step-by-step to the original maximum. In every 
case note and record the value of the exciting current i, and the corre- 
sponding throw of the galvanometer, 0. Form a table having the following 
headings to its columns : — 

i, JC> 0> change of (B, (ft. 

Values of IT are obtained from the formula, 

JC = 10 I , when I = average circumference of the test ring. 

Change of 63 is obtained by the formula, 

W R KB 

a n 2 ' 

where all letters have the same significance as in the formula on page 92. 
Remember that we started in our test with a maximum unknown value of (U 
and that we gradually decreased this by steps measurable by the throw of 
the galvanometer, and that we aftenvards raised the 03 in an opposite direc- 
tion to the same maximum unknown value, and still further reduced this to 
zero, and after commutation produced the original maximum value. Ac- 
cording to this, if due consideration be paid to the sign of the (ft which is 
determined by the direction of the galvanometer throw, the algebraic 
sum of the changes in (ft should be equal to zero ; the algebraic sum of the 
first or second half of the changes in (ft should be equal to twice the value 
of the original maximum, (ft. Taking this maximum value as the first under 
the column of the table headed (ft, and applying algebraically to this the 
changes in (ft for successive values, we obtain the completed table. Plot 
a curve of JCand(ft. The area enclosed represents the energy lost in carry- 
ing the sample through one cycle of magnetization between the maximum 
limits + (ft and —(ft. Measure this area, and express it in the same units as 
is employed for the co-ordinate axes of the curve. This area divided by 4* 



102 



MAGNETIC PROPERTIES OF IRON. 



gives the number of ergs of work performed per cycle upon one cubic centi- 
meter of the iron, the induction being carried to the limits -f- (Sand — (ft. 

Tlie Wattmeter Method of Hysteresis Tests. 

Inasmuch as the iron, a sample of which is submitted for test, is generally 
to be employed in the manufacture of alternating-current apparatus, it is 
desirable to make the test as nearly as possible under working conditions. 
If the samples be disks, as in the previous method, and these be shellacked 
on both sides before being united into the composite test-ring in order to 
avoid as much as possible foucault current losses, the test can be quickly 
made according to the method outlined in the following diagram : 




Fig. 11. Wattmeter Test for Hysteretic Constant. 

Alternating current of / cycles per second is sent through the test-ring. 
Its voltage, E, and current strength, t, are measured by the alternating- 
current voltmeter, V, and ammeter, A. If r be the resistance of the test- 
ring coil of ?ii turns, then the watts lost in hysteresis W, is equal to the 
wattmeter reading W — i 2 r. If the volume of the iron be V cubic centi- 
meters, and the cross section of the iron ring be a square centimeters, then 
Steinmetz's hysteretic constant 

10 7 W / V2tt ttt/a x 1 - 6 
V E 10 8 )' 



Vf 



Foucault current losses are neglected in this 
formula, and the assumption is made that the 
current is sinusoidal. 

Ewing-'s Hysteresis Tester. — In this in- 
strument, Fig. 12, the test sample is made up of 
about seven pieces of sheet iron %" wide and 3" 
long. These are rotated betweec the poles of a 
permanent magnet mounted on knife edges. 

The magnet carries a pointei which moves 
over a scale. Two standards of known hyster- 
esis properties are used for reference. The de- 
flections corresponding to these samples are 
plotted as a function of their hysteresis losses, 
and a line joining the two points thus found is 
referred to in subsequent tests, this line show- 
ing the relation existing between deflection and 
hysteresis loss. The deflections are practically 
the same, with a great variation in the thick- 
ness of the pile of test-pieces, so that no cor- 
rection has to be made for such variation. This 
instrument has the advantage of using easily 
prepared test samples. 




Fig. 12. 



Hysteresis Ttteter, T *ed by General Electric Co. 

Designed and Described by Frank Holden. 

During the last few weeks of the year 1892 there was built at the works of 
the General Electric Company, in Lynn, Mass., under the writer's direction, 
an instrument, shown in Fig. 13, by which the losses in sheet iron were 
determined by measuring the torque produced on the iron, which was 
punched in rings, when placed between the poles of a rotating electro-mag- 
net. The rings were held by a fibre frame so as to be concentric with a 



CORE LOSS. 



103 



vertical shaft which worked freely on a pivot bearing at its lower end. 
They had a width of 1 centimeter, an outside diameter of 8.9 centimeters^ 
and enough were used to make a cylinder about 
1.8 centimeters high. The top part of this in- 
strument, which rested on a thin brass cylin- 
der surrounding the rings, was movable. On 
the upper surface was marked a degree scale, 
over which passed a pointer, with which the 
upper end of a helical spring rotated. It was 
so constructed that when the vertical shaft 
with the rings and the upper part of the instru- 
ment with the spring was put in place, the 
lower end of the spring engaged with the shaft, 
and consequently rotated with the rings. A 
pointer moving with the lower end of the spring 
leached to the zero of the degree scale when 
the apparatus was ready for use. By this ar- 
rangement it was found what distortion it was 
necessary to give the spring in order to bal- 
ance the effect of the rotating magnet, and the 
spring having been calibrated, the ergs spent 
on the rings per cycle were determined by mul- 
tiplying the degrees distortion by a constant. 
A coil, so arranged that it surrounded but did not touch the rings, made 
contact at its ends with two fixed brushes that rested in diametrically oppo- 
site positions on a two-part commutator, which revolved with a magnet. 
The segments were connected each to a collector ring against which rubbed 
a brush, the latter two brushes being joined through a sensitive Weston 
voltmeter. If this were so arranged that the coil was at right angles to the 




Fig. 13. Hysteresis Meter. 







1000 


2000 3000 4000 


5000 0000 7000 






1 •[ 1 








r 




-T_ 


8000 


l|NDL 


G FP'i' 




fp 






16 


























-,4- 


















-- " +.* 


2* 


±=- S000 
















s 




















/ 






6U00 












—l*\ 






t-70oa 














*-/-- 




: 
















JZ 


















- 


2 






t^eooo 












~"V 




















/ 






































? 










3 _- 5000 






















3000 - 








i 




-T 




















_ ± 




















__ i- 






2:- 4000 










































- 


















•*nm 














=£- 






<HMi 


1000 1 












i 









100 200" 300 400 500 600 J00 
R.EVO.Lt)TI£WS PER MINUT^ 

Fig. 14. 

induction, when the brushes changed contact from one segment to the other, 
it is evident, the self-induction of the circuit being negligible, that the 
mean value of the current in the circuit was proportional to the total flux 
through the coil. Knowing the constant of the voltmeter, the deflection was 
easily calculated from the speed of the magnet, the number of turns in the 
coil, cross-section of the rings, and the resistance of the circuit. From an 
induction of 2,000 gausses to at least 10,000 gausses, the leakage across the 
interior space of the rings was negligible. 

Carried on the shaft below the magnet was a pulley around which passed 
a flat belt driven with a pulley of the same size on an electric motor, so that 
the speed of the magnet could be found by observing that of the motor. In 
operating, the deflections to be produced on the voltmeter at a certain speed, 
with the desired induction in the rings, were first calculated. Five hundred 



104 



MAGNETIC PROPERTIES OF IRON. 



revolutions per minute was generally adopted as the speed in this case. 
The motor being run at the desired speed, the magnetizing current was ad- 
justed until the calculated deflection was produced on the voltmeter. Keep- 
ing the magnetizing current constant, the speed was changed successively in 
value to certain values, and the corresponding distortions of the spring 
necessary to balance the effect of the magnet noted. When this process 
was carried out at different induction values, and the ergs expended per 
cycle on the rings plotted as a function of the speed, a series of lines was 
produced, as shown in Figs. 14 and 15. It was found that the slope of the 
lines decreased very rapidly with the decrease in thickness of the iron sheet 
used so as to indicate that had it been thin enough the slope would have 
been zero between 100 and 800 revolutions per minute, which was about the 
highest speed permissible. From this it would seem that, in these tests, the 
total loss per cycle had two components ; one remaining constant, due to 
hysteresis, and the other varying as the speed of the magnets, due to cur- 
rents induced in the iron. 

Fig. 18 gives observations of eddy current loss and thickness of iron sheet 
on this assumption. The line drawn is a parabola, so that it would appear 
that with the range of observations made the loss varied about as the square 
of the thickness of the sheets. 



1000 2000 3000 4000 5000 6000 7000 




100 200 300 .400 500 

revolutions per minute 
Fig. 15. 

Fig. 14 gives lines from iron .04 centimeters thick. Speed readings were 
not taken lower than 250 revolutions per minute, as it had been found that 
the lines were always straight, and speeds below this value could not be 
read with the tachometer available for this particular test. Plotting the 
hysteresis as a function of the induction, in this case the points are all quite 
close to a curve whose equation is, Ergs = A constant x (Density per square 
centimeter) 1 -* 7 , three points in the latter calculated curve being shown by 
the crosses. The iron, a test on which is shown in Fig. 15, was .1 centimeter 
thick, and shows a greater eddy current loss. The equation for the hystere- 
sis curve for this sample is, Ergs =: A constant x (Density per square centi- 
meters) 1,4 , some points in the latter curve being shown by crosses, as before. 

The eddy current losses for these two samples are plotted as functions of 
the induction in Fig. 17. The curves drawn are parabolas; showing that in 
these cases the eddy current loss varied approximately as the square of the 
induction, although there were often greater variations from that law than 
these two samples show. The average exponent for the hysteresis curves 
was a little over 1.5, although it varied from 1.4 to 1.7. Rings tested in this 
manner were wound and tested with a ballistic galvanometer, using the 
step-by-step method. There were discrepancies of as much as 4 per cent be- 
tween the two results, but an average of ten tests showed the ballistic gal- 
vanometer method gave results 2.5 per cent lowe." than the other. This 
difference is easily attributable to experimental errors. 

It being noticed that for a given induction in the rings, the magnetizing 
currents for different samples did not vary much, it was planned shortly 



CORE LOSS. 



105 




after completing the above apparatus to construct a modified instrument 
which would use electro-magnets of such high reluctance that the variations 
of the rings would be negligible, and induction 
be dependent only on the current. By making 
the electro-magnets of suitable iron and of 
about one-third the cross-section of the rings 
used, the iron may be so highly saturated 
that the induction will remain quite constant 
under considerable variation in the magnet- 
izing current, thus rendering unnecessary 
any accurate comparisons of magnetizing 
currents, and the rings can be at about their 
maximum permeability when thus magnetized. Such an instrument is 
shown in Fig. 13 in its original experimental form, with the rings in position 
ready for test. A modified form is shown in Fig. 16. The rings are 
here allowed to rotate in opposition to the action of a spring and carry a 
pointer over a scale, so that it is quite direct reading. Twenty-five compar- 



FiG. 16. 



Modified Hyster- 
esis Meter. 



i 



9QO0 | | | | || | | | | || 




X o^2" 












7000 -gAusses , *■ 








6000 ^ ,-* 
















4000 r -y** 


r 






















1000 










400 GOO 800 1000 1200 1400 

ergs per cm 3 per cycle 

eddy current loss 
speed 700 rev's per min. 
Fig. 17. 

isons of this instrument with the original one gave results that agreed 
within 6 per cent in all cases, and more than half were within 2 per cent of 
agreement. Permanent magnets had been previously tried, but the attempt 
seemed to show that the instrument would not, in that case, compare sam- 
ples of iron widely different in character ; and the writer not being able to 



TH CKNE SS, IN MM 



Z 



~z. 



^1 



:a- 



z 



100 200 300 400 500 600 700 800 900 10001100 1200 130014XX) 15TO1600 1700 

ergs per cm 3 "per cycle 
Fig. 18. 

give any attention to the matter, no further investigations in that direction 
were attempted. 

The instrument first described has been in use continuously since its com- 
pletion at the works of the General Electric Company, in Schenectady. 



106 



MAGNETIC PROPERTIES OF IRON. 



ERRY CURRENT FACTORS FOR RI FFFREXT 

CORE DE^§ITIE§ A.\W FOR VARIOUS 

lAlfFOTATIOXS. 

(Wiener.) 



fa d. fa fa 

° § « o 
fa^g 5 

t> O ^ 2 • 


Watts dissipated 


fa £ fa fa 

fa A H g 
A £ S fa O" 


Watts dissipated 


PER CUBIC FOOT OF 

IRON at a fre- 
quency OF 1 CYCLE 


PER CUBIC FOOT OF 
IRON AT A FRE- 
QUENCY OF 1 CYCLE 


<J H o* fc co 

g « 

& ^ • fa 


PEE 


SECOND. 




^fa5S M 

O fa 
^% • fa 


PER 


SECOND. 
















Thickness of lamination, 5 


Thickness of lamination, 8 


s »«» 










r.Ho 








M fa£ tf tf 










5 fa r* tf g 
























5 


.010" 


.020" 


.040" 


.080" 




.010" 


.020" 


.040" 


.080" 


10,000 


.0007 


.003 


.012 


.046 


66,000 


.0315 


.126 


.503 


2.013 


15,000 


.0016 


.007 


.026 


.104 


67,000 


.0325 


.130 


.519 


2.075 


20,000 


.0029 


.012 


.046 


.185 


68,000 


.0335 


.134 


.534 


2.137 


25,000 


.0045 


.018 


.072 


.288 


69,000 


.0345 


.138 


.550 


2.200 


30,000 


.0065 


.026 


.104 


.416 


70,000 


.0355 


.142 


.566 


2.265 


31,000 


.0070 


.028 


.111 


.444 


71,0W 


.0365 


.146 


.582 


2.330 


32,000 


.0074 


.030 


.118 


.472 


72,000 


.0375 


.150 


.599 


2.396 


33,000 


.0079 


.032 


.126 


.503 


73,000 


.9385 


.154 


.616 


2.463 


34,000 


.0084 


.034 


.134 


.534 


74,000 


.0396 


.158 


.633 


2.530 


35,000 


.0089 


.036 


.142 


.567 


75,000 


.0407 


.163 


.650 


2.600 


36,000 


.0094 


.038 


.150 


.600 


76,000 


.0418 


.167 


.668 


2.670 


37,000 


.0099 


.040 


.158 


.633 


77,000 


.0429 


.171 


.685 


2.740 


38,000 


.0104 


.042 


.167 


.667 


78,000 


.0440 


.176 


.703 


2.810 


39,000 


.0110 


.044 


.176 


.703 


79,000 


.0451 


.180 


.721 


2.883 


40,000 


.0116 


.046 


.185 


.740 


80,000 


.0462 


.185 


.740 


2.958 


41,000 


.0122 


.049 


.194 


.777 


81,000 


.0474 


.190 


.758 


3.033 


42,000 


.0128 


.051 


.204 


.815 


82,000 


.0486 


.194 


.777 


3.108 


43,000 


.0134 


.054 


.214 


.855 


83,000 


.0498 


.199 


.796 


3.184 


44,000 


.0140 


.056 


.224 


.896 


84,000 


.0510 


.204 


.815 


3.260 


45,000 


.0146 


.059 


.234 


.937 


85,000 


.0523 


.209 


.835 


3.340 


46,000 


.0153 


.061 


.245 


.979 


86,000 


.0535 


.214 


.855 


3.420 


47,000 


.0160 


.064 


.256 


1.022 


87,000 


.0548 


.219 


.875 


3.500 


48,000 


.0167 


.067 


.267 


1.066 


88,000 


.0560 


.224 


.895 


3.580 


49,000 


.0174 


.070 


.278 


1.110 


89,000 


.0573 


.229 


.916 


3.662 


50,000 


.0181 


.072 


.289 


1.055 


90,000 


.0586 


.234 


.937 


3.745 


51,000 


.0188 


.075 


.300 


1.200 


91,000 


.0599 


.240 


.958 


3.830 


52,000 


.0195 


.078 


.312 


1.248 


92,000 


.0612 


.245 


.979 


3.915 


53,000 


.0202 


.081 


.324 


1.297 


93,000 


.0625 


.250 


1.000 


4.000 


54,000 


.0210 


.084 


.337 


1.346 


94,000 


.0638 


.255 


1.021 


4.085 


55,000 


.0218 


.087 


.349 


1.397 


95,000 


.0651 


.261 


1.043 


4.170 


56,000 


.0226 


.091 


.362 


1.448 


96,000 


.0665 


.266 


1.064 


4.257 


57,000 


.0234 


.094 


.375 


1.500 


97,000 


.0679 


272 


1.086 


4.345 


58,000 


.0242 


.097 


.389 


1.555 


98,000 


.0693 


.277 


1.109 


4.436 


59,000 


.0251 


.101 


.403 


1.610 


99,000 


.0707 


.283 


1.132 


4.528 


60,000 


.0260 


.104 


.416 


1.665 


100,000 


.0722 


.289 


1.156 


4.622 


61,000 


.0269 


.108 


.430 


1.720 


105,000 


.0797 


.319 


1.274 


5.095 


62,000 


.0278 


.111 


.444 


1.776 


110,000 


.0875 


.350 


1.398 


5.593 


63,000 


.0287 


.115 


.458 


1.833 


115,000 


.0955 


.382 


1.528 


6.113 


64,000 


.0296 


.118 


.473 


1.891 


120,000 


.1040 


.416 


1.664 


6.655 


65,000 


.0305 


.122 


.486 


1.951 


125,000 


.1128 


.451 


1.806 


7.222 



SPECIFIC ENERGY DISSIPATION IN ARMATURE CORE. 107 



SPECIFIC JGXF.RO V DISSIPATION IUT ARMATURE 

CORE. 







Hysteresis Loss for 


Eddy-Current Loss in Watts 


Maximum 


Sheet Iron at Fre- 


for .030" (.075 cm.) Lamina- 


quency of One Mag- 


tion, 


at One Cycle per 


Dex 


^ 


netic Cycle per 


Secon 


d Proportional to 


SITY. 


Second (in Watts) 


Square of Frequency. 






(r, = 0.002). 








Lines 


















Gaus- 


of force 


Per 


Per 


Per 


Per 


Per 


Per 


Per 


Per 


ses. 


per 
sq. in. 


cm.3 


cu. ft. 


kg. 


lb. 


cm.3 


cu. ft. 


kg. 


lb. 


2,000 


12,900 


.000039 


1.13 


.0052 


.0023 


.0000004 


.011 


.000051 


.000023 


3,000 


19,350 


.000073 


2.09 


.0080 


.0044 


.0000009 


.020 


.000119 


.000054 


4,000 


25,800 


.000116 


3.28 


.0153 


.0069 


.0000016 


.046 


.000212 


.000096 


5,000 


32,250 


.000166 


4.68 


.0216 


.0098 


.0000025 


.071 


.000327 


.000148 


6,000 


38,700 


.000222 


6.31 


.0291 


.0131 


.0000036 


.102 


.000471 


.000213 


7,000 


45,150 


.000288 


8.08 


.0372 


.0169 


.0000049 


.139 


.000640 


.000290 


8,000 


51,600 


.000352 


10.00 


.0461 


.0208 


.0000064 


.181 


.000833 


.000377 


9,000 


58,050 


.000424 


11.94 


.0551 


.0249 


.0000081 


.229 


.001054 


.000478 


10,000 


64,500 


.000500 


14.06 


.0648 


.0294 


. 0000100 


.283 


.001303 


.000590 


11,000 


70,950 


.000586 


16.17 


.0745 


.0337 


.0000121 


.343 


.001580 


. 000715 


12,000 


77,400 


.000672 


18.91 


.0871 


.0394 


.0000144 


.408 


001878 


.000850 


13,000 


83,850 


.000765 


21.65 


.0997 


.0452 


. 0000169 


.479 


.002204 


.000998 


14,000 


90,300 


.000869 


24.40 


.1123 


.0509 


. 0000196 


.555 


.002553 


.001157 


15,000 


96,750 


.000950 


27.18 


.1254 


.0566 


.0000225 


.637 


.002923 


.001328 


16,000 


103,200 


.001065 


30.23 


.1396 


.0638 


. 0000256 


.725 


.003340 


.001512 


17,000 


109,650 


.001175 


33.33 


.1537 


.0694 


.0000289 


.818 


.003770 


.001708 


18,000 


116,100 


.001287 


36.40 


.1675 


.0758 


.0000324 


.917 


.004220 


.001911 


19,000 


122,550 


.001406 


39.76 


.1830 


.0828 


. 0000361 


1.022 


.004710 


.002130 


20,000 


129,000 


.001523 


43.20 


.1978 


.0900 


.0000400 


1.133 .005225 


.002362 



Iron Iioss Determinations.— Since, in different types of electrical 
apparatus, uniformity or similarity of the flux distribution is not approached, 
the determination of iron losses from actual machines, when possible, is the 
best way of obtaining loss constants for the design of other machines of 
the same type. 



ELECTROMAGNETS. 

PROPERTIES. 

Revised by Townsend Wolcott and Prof. Samuel Sheldon, 

Residual Magnetism is the magnetization remaining in a piece of mag- 
netic material after the magnetizing force is discontinued. 

Retentiveness is that property of magnetizable materials which is meas- 
ured by the residual magnetism. 

Coercive Force is the magnetizing force necessary to remove all residual 
magnetism. 

Permanent magnetism is residual magnetism in a material of great coer- 
cive force, as hard steel, which has little retentiveness; while soft iron has 
great retentiveness but little coercive force. 

The following paragraphs are condensed from S. P. Thompson's "The 
Electromagnet : " 

HEagrneto-JfEotive Force. — The magneto-motive force, or magnetiz- 
ing power of an electro-magnet is proportional to the number of turns of 
wire and jhe amperes of current flowing through them ; that is, one ampere 
flowing through ten coils or turns will produce the same magneto-motive force 
as ten amperes flowing through one coil or turn. 

If n = number of turns in the coil, 
1=: amperes of current flowing, 

1.257 = -r^ (to reduce to C. G. S. units). 

Magneto-motive force = 1.257 x nlz=$. 

Intensity of ItEagrnetic Force. — Intensity of magnetic force in an 
electro-magnet varies in different parts of the magnet, being strongest in 
the middle of the coil, and weaker toward the ends. In a long electro-mag- 
net, say a length 100 times the diameter, the intensity of magnetic force will 
be found nearly uniform along the axis, falling off rapidly close to the ends. 

In a long magnet, such as described above, and in an annular ring wound 
evenly over its full length, the value of the magnetic force, J£, is deter- 
mined by the following expression : — 

3£= 1.257 —r- , in which Z= centimeters. 

If the length is given in inches, then 
n I 
J£ = .495 -j— , in which l /y z=. inches. 

If intensity of the magnetic force is to be expressed in lines per sq. inch, 

JC//= 3.193 x^. 

Value of JC »* *«« centre of a Single-turn of Conductor. — 

In a single ring or turn of wire of radius r, carrying / amperes of current 

Force on Conductor (carrying* current) 
in a UKagrnetic Field. — A conductor carrying 
current in a magnetic field is repelled from the 
field Dy a certain mechanical force acting at right 
angles both to the conductor itself and to the lines 
of force in the field ; see Fig. 1. 

The magnitude of this repelling force is deter- 
mined as follows, assuming the field to be uniform: 

JP = magnetizing force, or intensity of the field. 
I =z length of conductor across the field in cm. 
l f , = ditto in inches. 

I— amperes of current flowing in the conductor. 
Fz=. repelling force. 

- X1L . Fm dyn es = %£/ . F in grains %^ 




Fig. 1. Action of Mag- 
netic Field, on Con- 
ductor carrying cur- 
rent. 



F in dynes : 



108 



PROPERTIES OF ELECTROMAGNETS. 109 



Work done by Conductor (carrying- Current) in moving 
across a Magnetic Field* 

If the conductor described in the preceding paragraph be moved across 
the field of force, the work done will be determined as follows : in addition 
to the symbols there used, let b = breadth of field in and across which the 
conductor is moved ; w — work done in ergs. 

bl = area of field, 

N=. bl x 4> = number of lines of force cut, 

NI 
W =l0' 

Rotation of Conductor (carrying- current) around a Itlagrnet 

role. 

If a conductor (carrying current) be so arranged that it can rotate about 
the pole of a magnet, the force producing the rotation, called torque, will be 
determined as follows : The whole number of lines of force radiating from 
the pole will be 4tt times the pole strength m. 

4:tt ml . ___ T 
w — — 7q— = 1-257 ml. 

Dividing by the angle 2tt, the torque, T, is 

Every electric circuit tends to place itself so as to embrace the maximum 
flux. 

Two electric conductors carrying currents tend to place themselves in position 
such that their mutual flux may be maximum ; otherwise stated : if two cur- 
rents run parallel and in the same direction, each produces a field of its 
own, and each conductor tends to move across the other's field. 

In two coils or conductors lying parallel to each other, as in a tangent gal- 
vanometer, the mutual force varies directly in proportion to the product of 
their respective n/,and inversely as the axial distance they are apart. 

Principle of the Tlag-uetic Circuit. — The resistance that a mag- 
netic circuit offers to the passage or flow of magnetic lines of force or flux, 
has been given the name of reluctance, symbol (ft, and is analogous to resist- 
ance, to the flow of electric current in a conductor. 

The magnetic flux or lines of force are treated as current flowing in the 
magnetic circuit, and denoted by the symbol <£. 

The above two factors, together with the magneto-motive force described in 
the early part of this chapter, bear much the same reiation to each other 
as do resistance, current, and E.M.F. of electric circuits, and are expressed 
as follows : — 

, x .. „ Magneto-motive force 

Magnetic flux = - — . 

reluctance 

1.257 nl 

Afx 

nl= +J& , 
1.257 



110 ELECTKOMAGNETS. 



If dimensions are in inches, and A is in square inches, then 
nl— <f>-^- X .3132. 
and <£ = (&" A". 

TUe JLaw of Traction. — The formula for the pull or lifting-power 
of an electromagnet when the poles are in actual contact with the arma- 
ture or keeper is as follows : 

Pull (in dynes) = ^ — . 
Pull (in grammes) = 



8 w x 981 

Pull (iii pounds) = „™ nnn '• 
v ^ ' 11,183,000 

fir\ 2 A" 
In inch measure: Pull (in pounds) = " • 

> Jd , 104,000 

Traction. 

This proportionality to the square of the induction accounts for some 
anomalous peculiarities in the way that the keeper of a magnet holds fast 
to the poles. If the pole faces be perfectly true and flat and the face of 
the keeper the same, the keeper is actually held with less force than when the 
pole faces are very slightly convex. Or, again, if the keeper be slid to one 
side until only its sharp edge and that of the poles are in contact, it will be 
found to adhere more firmly than when placed squarely and centrally on 
the poles. In general, a magnet holds tighter to a slightly uneven surface 
than to one which perfectly fits the poles. The reason is that, when the 
area of contact is decreased, the intensity of the induction through the 
remaining contact is increased by the crowding together of the lines of 
induction; and, as the traction is proportional to the product of the area 
and the square of the intensity of the induction, so long as there is sufficient 
crowding of the lines so that the square of their intensity increases more 
than the area is diminished, the traction is increased by reducing the area 
of contact. ^. 2 

The amount of the traction is usually determined by the formula, T z=z __ . 

in which T is the traction per square centimeter expressed in dynes: to 
express the traction in grammes, this figure is of course divided by 981, or 
for pounds avoirdupois per square inch it should be divided by 69090. 
This formula is correct for the force required to separate the halves of a 
straight bar magnet cut in the middle, if the winding be also in halves and 
these halves separate at the same time as their respective halves of the 
core and if, further, the winding fit the core closely. It is also correct for 
the separating force when the magnetism is residual; as in the case of a per- 
manent magnet. In other cases, for example, where an ordinary keeper is 
pulled away from a magnet, the formula is not strictly accurate on account 
of the keeper being attracted partly by the core of the magnet and partly 
by the current in the winding directly. However, the attraction exerted by 
the coil is usually small as compared to that exerted by the core; and the 
formula is not very much in error. 

The attraction between the two parts of the iron is always 2 71-3 2 dynes 
per square centimeter, 3 being the intensity of magnetization, that is the 
number of units of free magnetism per square centimeter. But (fc^z^nQ 
+ JC so when J£ = 0, that is when there is no magnetizing force, 2 11-32 

r= - — , which is evidently correct, as there is no attraction except between 

the two parts of the iron. When J£ is not equal to zero, that is, when the 
magnetism is not residual, there is a force between the coil and the part of 
the iron that is moved away from the coil equal to JC3 ( ^y nes per square 
centimeter, so that the whole force of separation is 2 tt^ 2 -f- J£3- When 
there is a coil on each part of the magnet and both parts of the magnet 



PROPERTIES OF ELECTROMAGNETS. 



Ill 



and both coils are just alike, there are two of these J£3 forces, because 
each coil attracts the other part of the iron; but as in this case J£ represents 
the intensity of the magnetizing force of the whole coil each half now 

attracts the other part of the iron with a force of ' and both forces 

2 Hf>2 

together equal 3C3- The two coils attract each other with a force of- 



3C 2 



8tt 



per square centimeter, so the whole force is 2 n 3 2 + 5C3 + s — > which 

1 1 87r rt* 

may be written ^- (16 n* 3 2 + 8 n JC 3 + JC 2 ) = <±- (4 tt 3 + JC) 2 = -^- 

per square centimeter, so in this case also the traction is proportional to 
the square of the intensity of the induction. If the coils be loose upon 
the cores so that their areas are sensibly greater than those of the cores, 
the whole force of separation is greater than that given by the equation; 
but, in practical cases, the error is usually small. In all cases, the attrac- 
tion between the iron parts is 2 rr 3 2 per square centimeter. 

UEag-netization and Traction of Electromagmets*. 



(B 


(B" 


Dynes 


Grammes 


Kilogs 


Pounds 


Lines per 


Lines per 


per 


per 


per 


per 


sq. cm. 


sq. inch. 


sq. cm. 


sq. cm. 


sq. cm. 


sq. inch. 


1,000 


6,450 


39,790 


40.56 


.04056 


.577 


2,000 


12,900 


159,200 


162.3 


.1623 


2.308 


3,000 


19,350 


358,100 


365.1 


.3651 


5.190 


4,000 


25,800 


636,600 


648.9 


.6489 


9.228 


5,000 


32,250 


994,700 


1,014 


1.014 


14.39 


6,000 


38,700 


1,432,000 


1,460 


1.460 


20.75 


7,000 


45,150 


1,950,000 


1,987 


1.987 


28.26 


8,000 


51,600 


2,547,000 


2,596 


2.596 


36.95 


9,000 


58.050 


3,223,000 


3,286 


3.286 


46.72 


10,000 


64,500 


3,979,000 


4,056 


4.056 


57.68 


11,000 


70,950 


4,815,000 


4,907 


4.907 


69.77 


12,000 


77,400 


5,730,000 


5,841 


5.841 


83.07 


13,000 


83,850 


6,725,000 


6,855 


6.855 


97.47 


14,000 


90,300 


7,800,000 


7,550 


7.550 


113.1 


15,000 


96,750 


8,953,000 


9,124 


9.124 


129.7 


16,000 


103,200 


10,170,000 


10,390 


10.390 


147.7 


17,000 


109,650 


11,500,000 


11,720 


11.720 


166.6 


18,000 


116,100 


12,890,000 


13,140 


13.140 


186.8 


19,000 


122,550 


14,360,000 


14,630 


14.630 


208.1 


20,000 


129,000 


15,920,000 


16,230 


16.230 


230.8 



Exciting- Power and Traction. — If we can assume that there is 
no magnetic leakage, the exciting power may be calculated from the follow- 
irig expression ; all dimensions being in inches, and the pull in pounds: 

nl=z^— x.3132, 

nXnl 

^ — I" X .3132 ' 



also, (ft" = 8494 ^ 



Pull 



7// 

7i/=2661X — X 
If dimensions are in metric measure, 



\. 



Pull 



nl=3951 



Area" 

. / Pull in kilos 
▼ Area in sq. cms. ' 



^=1316.6 



/ 



Pull in lbs. 
Area in sq. ins. 



^ *~ n ~ l /Pull in kilos. 

(R = 4965 V -i 

w t Area sq. cm. 



112 



ELECTROMAGNETS. 



WINDING OF EUECTJRO^AOjIUTS. 

The method used by Cecil P. Poole for predetermining magnet windings 
is as follows: Temporary test coils, of wire much larger than will probably 
be required in the permanent coils, are wound to occupy the space that 
it is estimated the permanent coil will occupy. Current is passed through 
the temporary coils in series with a water rheostat or finely graduated 
resistance, by means of which the excitation may be closely adjusted. 
The exciting current is adjusted until the desired magnet performance is 
obtained ; the current producing this effect is represented by Ix. The 
current is then increased or decreased as may be required until the resist- 
ance per foot of the winding corresponds with the resistance per foot given 
by Table I herewith, after five hours. The current required to produce 
this result is indicated by In. 

The size of wire required to produce a given number of ampere-turns 
under given conditions of mean length and voltage is 



d°~ = 



KAtLm 



in which d 2 equals circular mils of the wire to be used, K is a coefficient de- 
pending upon the specific resistance of the wire, At equals the ampere-turns 
desired, Lm equals the mean length per turn of wire in inches, and V equals 
the volts at the terminals of the coil. With the best commercial grade of 
magnet wire, K becomes unity at a temperature of about 140° Fahr., since 
the resistance per mil-foot of the wire at that temperature is 12 ohms. 
The resistances of wires given by Table I are based on this temperature. 
Table II has been calculated from the foregoing formula for this temper- 
ature. 

From the first test made with the temporary winding the desired ampere- 
turns are obtained, and from Table II may be obtained the size of wire 
required to give the nearest number of ampere-turns per volt corresponding 
to this test and the proposed working voltage. 



Table I. - 



Resistance of 3Kagriet Wire at 140° Tempera- 
ture, Fahrenheit. 



Wire No. 


Resistance per Foot. 


Wire No. 


Resistance per Foot. 


4 
5 
6 


0.0002875 
0.0003625 
0.0004571 


19 
20 
21 


0.009316 

0.01176 

0.014814 


7 
8 
9 


0.00057662 

0.0007268 

0.0009168 


22 
23 
24 


0.018691 
0.023575 
0.0297 


10 
11 
12 


0.001156 

0.0014575 

0.001838 


25 
26 
27 


0.0375 

0.04725 

0.05956 


13 
14 
15 


0.0023175 

0.002922 

0.003684 


28 
29 
30 


0.0751 
0.0947 
0.1194 


16 
17 

18 


0.004646 

0.00586 

0.007389 


31 
32 
33 


. 1506 
. 1899 
0.2395 



WINDING OF ELECTROMAGNETS. 113 



The number of turns of wire in the test coil will, of course, be known, 
and the product of this number and the current, lx, is the required exciting 
force in ampere-turns. The mean length per turn of wire in the perma- 
nent winding will be the same as that in the test winding, subject to minor 
corrections that may prove necessary in rounding out the final results. 
Tentatively, at least, the mean length, Lm, will be equal to 

Gt + g 
2 ' 

in which Gt is the girth of the test coil and g the girth of the bobbin or form 
in which it was wound. Having the ampere-turns required, the mean 
length per turn of wire and the voltage that will be applied to the terminals 
of the coil (or each coil, if there are more than one), the size of wire that 
must be used in the permanent winding is obtainable by the application 
of Table II. It may happen that none of the mean length values in the 
table will be found to correspond with that of the test winding; in that 
event, the nearest table value may be adopted and the mean length per 
turn of the permanent winding made to conform to this. In many cases 
it will be found that both the excitation per volt and the mean length per 
turn of the test winding will differ from all values in the table; in such a 
case, the nearest mean length value in the table should be adopted which 
gives the nearest excitation per volt in excess of the desired value. 

The table is worked out on the assumption that any two wires drawn to 
B. & S. gauge and differing in size by ten gauge numbers will have cross- 
sectional areas differing in the ratio of 1 to 10.163 or 10.163 to 1, according 
to which wire is considered first. 

As stated in the note at the foot of the table, the ampere-turns per volt 
in column a apply to the wire sizes in line A across the top of the table; 
the ampere-turns per volt in column b apply to the wire sizes in line B, and 
those in column c, to the wires in line C Thus, if a coil wound with No. 
8 wire has a mean length of 45.11 inches per turn, its exciting force will 
be 366 ampere-turns for each volt at its terminals; a coil of the same mean 
length but wound with No. 18 wire will have 36 ampere-turns per volt, 
while a coil of No. 28 wire with the same mean length per turn will yield 
only 3.54 ampere-turns per volt of applied E.M.F. The table is calculated 
on the basis of the wire sizes in line B and the ampere-turns per volt in 
column b, hence the latter values are not numbers from which decimals 
have been dropped, but are exact. 

If the winding is to operate at constant potential, as most magnet wind- 
ings do, the watts dissipated will be exactly proportional to the current 
passing, and this will be inversely proportional to the length of the coil par- 
allel with the magnet core if the girth and temperature remain constant. 
The temperature will be unchanged, of course, the value Ih, of the current 
necessary to produce the working temperature having been ascertained by 
trial, as previously described. If the girth of the permanent winding 
cannot be made identical with that of the test winding, the correction in 
dimensions will be simple. First, the proper length on the hypothesis of 
unchanged girth must be determined. As the temperature of the coil is 
a function of the heat dissipated per unit of effective radiating surface, 
and the radiating surface is approximately proportional to the length of 
the coil parallel with the core (assuming the girth fixed), the heat dissi- 
pated per unit of surface will be approximately proportional inversely to 
the square of the coil length. Therefore, if the girth of the permanent 
winding were identical with that of the test winding, the proper length 
of the permanent coil would be given by the equation. 

LtX V^ = Lc (1) 

in which Lt is the length of the test coil and Lc the calculated length of the 
permanent coil on the basis of unchanged girth. Table III (divided into 
lour sections, Ilia, Illb, IIIc and Hid,) gives the corrected coil length, 
Lc, corresponding to a considerable practical range of test coil lengths, 
Lt, and ratios of Ik to Ih. If no correction in the mean length per turn 



114 



ELECTROMAGNETS. 



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CO00l>COr-l 


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to 

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WINDING OF ELECTROMAGNETS. 



115 



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3^.3 



116 ELECTROMAGNETS. 

is necessary, this set of tables will, of course, give the proper length, L, 
of the permanent coil, which in such cases is identical with Lc. If a cor- 
rection in mean length is necessary and is such as to alter materially the 
girth of the coil, and, therefore, the radiating surface per unit of length, 
after making the correction in mean length as explained in a preceding 
paragraph, and ascertaining the calculated length of coil, Lc, by means of 
Table III, the final value for the length (L) of the permanent coil may be 
obtained by means of the formula 

Lc xGt 

—G—= L (2) 

being the girth that the permanent coil will have after correcting the 
mean length per turn, and Gt the girth of the test coil. 

For convenience in making corrections in the mean length per turn and 
the girth of the finished coil, Table IV (divided into IVa to IVe inclusive) 
has been prepared. This gives the depth of coil that will be obtained with 
different numbers of layers of the standard sizes of magnet wire, single 
and double cotton covered. 

The table is based on the insulation thicknesses used by the Roebling 
factory, and while the coil depths are given to the second and third decimal 
places, it will, of course, be understood that this is not intended as an in- 
timation that coils can be wound in practice to any such degree of accuracy, 
even if the insulation ran absolutely uniform always, which it does not do. 
The full figures are given in this, as in Tables I and II, merely in order that 
one may see what the exact theoretical values are. The table has not been 
made to include very small sizes of wire, for the reason that any approach 
to accuracy in calculations based on the insulated diameters of such wires 
is impossible. 

For coils wound around a continuously convex surface, such as that 
of a bobbin for a round magnet core or one of oval cross section, the mean 
length per turn of wire is readily obtained by means of the formula 

g + ,r d = Lm (3) 

in which g is the girth of the bobbin or former in which the coil is wound 
and d is the depth of the winding (in inch measure, or whatever unit of 
linear measurement may be used; not in layers). The girth of the coil 
will be obtainable by means of the formula 

g + 2-nd = G (4) 

The mean length per turn in a coil wound on a bobbin of substantially 
rectangular cross section will be greater than the value given this formula 
on account of the bulging of the wire away from the core in the parts of 
the winding which cover the straight surfaces of the bobbin or former. 
This is also true, and to a greater extent, of the girths of the finished 
coil. 



WINDING OF ELECTROMAGNETS. 



117 



Table Ilia. — Tor correcting* JLeng'tli of Jlagrnet Coil. 



Ix 










Length of Test Coil, Lt. 








Ih 


1* 


H 


H 


U 


2 


2* 


k 


2f 


2i 


2| 


2f 


2| 


.4 . . 


.95 


1.03 


1.11 


1.19 


1.27 


1.35 


1.43 


1.5 


1.58 


1.66 


1.74 


1.82 


.425 . 


.98 


1.06 


1.14 


1.22 


1.31 


1.39 


1.47 


1.55 


1.63 


1.71 


1.8 


1.87 


.45 . . 


1.01 


1.09 


1.17 


1.26 


1.34 


1.43 


1.51 


1.6 


1.68 


1.76 


1.85 


1.93 


.475 . 


1.03 


1.12 


1.21 


1.29 


1.38 


1.47 


1.55 


1.64 


1.72 


1.81 


1.9 


1.98 


.5 . . 


1.06 


1.15 


1.24 


1.33 


1.42 


1.5 


1.59 


1.68 


1.77 


1.86 


1.95 


2.03 


.525 . 


1.09 


1.18 


1.27 


1.36 


1.45 


1.54 


1.63 


1.72 


1.81 


1.9 


1.99 


2.08 


.55 . . 


1.12 


1.21 


1.3 


1.39 


1.48 


1.58 


1.67 


1.76 


1.86 


1.95 


2.04 


2.13 


.575 . 


1.14 


1.23 


1.33 


1.42 


1.52 


1.61 


1.71 


1.8 


1.9 


1.99 


2.09 


2.18 


.6 . . 


1.16 


1.26 


1.36 


1.45 


1.55 


1.65 


1.74 


1.84 


1.94 


2.03 


2.13 


2.23 


.625 . 


1.18 


1.29 


1.38 


1.48 


1.58 


1.68 


1.78 


1.88 


1.98 


2.08 


2.17 


2.27 


.65 . . 


1.21 


1.31 


1.41 


1.51 


1.61 


1.71 


1.82 


1.92 


2.02 


2.12 


2.22 


2.32 


.675 . 


1.23 


1.34 


1.44 


1.54 


1.64 


1.75 


1.85 


1.95 


2.05 


2.16 


2.26 


2.36 


.7 . . 


1.26 


1.36 


1.47 


1.57 


1.67 


1.78 


1.88 


1.99 


2.09 


2.2 


2.3 


2.41 


.725 . 


1.28 


1.38 


1.49 


1.6 


1.7 


1.81 


1.92 


2.02 


2.13 


2.24 


2.34 


2.45 


.75 . . 


1.3 


1.41 


1.52 


1.62 


1.73 


1.84 


1.95 


2.06 


2.17 


2.27 


2.38 


2.49 


.8 . . 


1.34 


1.46 


1.57 


1.68 


1.79 


1.9 


2.01 


2.13 


2.24 


2.35 


2.46 


2.57 


.85 . . 


1.39 


1.5 


1.61 


1.73 


1.85 


1.96 


2.08 


2.19 


2.31 


2.42 


2.54 


2.65 


.9 . . 


1.42 


1.54 


1.66 


1.78 


1.9 


2.02 


2.14 


2.25 


2.37 


2.49 


2.61 


2.73 


.95 . . 


1.46 


1.58 


1.71 


1.83 


1.95 


2.07 


2.19 


2.32 


2.44 


2.56 


2.68 


2.8 


1. . . . 


1.5 


1.63 


1.75 


1.88 


2. 


2.13 


2.25 


2.38 


2.5 


2.63 


2.75 


2.88 


1.05 . . 


1.54 


1.67 


1.79 


1.92 


2.05 


2.18 


2.31 


2.44 


2.56 


2.69 


2.82 


2.95 


1.1 . . 


1.57 


1.71 


1.84 


1.97 


2.1 


2.23 


2.36 


2.49 


2.62 


2.75 


2.88 


3.02 


1.2 . . 


1.64 


1.78 


1.92 


2.05 


2.19 


2.33 


2.47 


2.6 


2.74 


2.88 


3.01 


3.15 


1.3 . . 


1.71 


1.85 


1.99 


2.14 


2.28 


2.42 


2.57 


2.71 


2.85 


3. 


3.14 


3.28 


1.4 . . 


1.78 


1.92 


2.07 


2.22 


2.37 


2.51 


2.66 


2.81 


2.96 


3.11 


3.25 


3.4 


1.5 . . 


1.84 


1.99 


2.14 


2.3 


2.45 


2.6 


2.76 


2.91 


3.06 


3.22 


3.37 


3.52 


1.6 . . 


1.9 


2.06 


2.21 


2.37 


2.53 


2.69 


2.85 


3.01 


3.16 


3.32 


3.48 


3.64 


1.7 . . 


1.96 


2.12 


2.28 


2.45 


2.61 


2.77 


2.93 


3.1 


3.26 


3.42 


3.59 


3.75 


1.8 . . 


2.01 


2.18 


2.35 


2.52 


2.68 


2.85 


3.02 


3.19 


3.35 


3.52 


3.69 


3.86 


1.9 . . 


2.07 


2.24 


2.41 


2.59 


2.76 


2.93 


3.1 


3.27 


3.45 


3.62 


3.79 


3.96 


2. . . . 


2.12 


2.3 


2.48 


2.65 


2.83 


3 


3.18 


3.36 


3.54 


3.71 


3.89 


4.07 


2.1 . . 


2.17 


2.36 


2.54 


2.72 


2.9 


3 '.08 


3.26 


3.44 


3.62 


3.81 


3.99 


4.17 


2.2 . . 


2.23 


2.41 


2.6 


2.78 


2.97 


3.15 


3.34 


3.52 


3.71 


3.89 


4.08 


4.27 


2.3 . . 


2.28 


2.47 


2.65 


2.84 


3.03 


3.22 


3.41 


3.6 


3.79 


3.98 


4.17 


4.36 


2.4 . . 


2.32 


2.52 


2.71 


2.91 


3.1 


3.29 


3.49 


3.68 


3.87 


4.07 


4.26 


4.46 



The above numbers (in the body of the table) are corrected lengths, Lc 



118 



ELECTROMAGNETS. 



Tabic 1 1 lb. — For correcting- Teng"tli of Mag-net Coil. 



Ix 










Length of Test Coil, Lt. 








Ih 


3 


3£ 


3* 


31 


3i 


31 


3i 


31 


4 


4* 


4i 


4f 


.4 . . 


1.9 


1.98 


2.06 


2.14 


2.22 


2.3 


2.37 


2.45 


2.53 


2.61 


2.69 


2.77 


.425 . 


1.96 


2.04 


2.12 


2.2 


2.28 


2.36 


2.45 


2.53 


2.61 


2.69 


2.77 


2.85 


.45 . . 


2.01 


2.1 


2.18 


2.26 


2.35 


2.43 


2.52 


2.6 


2.68 


2.77 


2.85 


2.94 


.475 . 


2.07 


2.15 


2.24 


2.33 


2.41 


2.5 


2.58 


2.67 


2.76 


2.84 


2.93 


3.02 


.5 . . 


2.12 


2.21 


2.3 


2.39 


2.48 


2.56 


2.65 


2.74 


2.83 


2.92 


3.01 


3.09 


.525 . 


2.18 


2.26 


2.36 


2.45 


2.54 


2.63 


2.72 


2.81 


2.9 


2.99 


3.08 


3.17 


.55 . . 


2.23 


2.32 


2.41 


2.5 


2.60 


2.69 


2.78 


2.87 


2.97 


3.06 


3.15 


3.23 


.575 . 


2.28 


2.37 


2.46 


2.56 


2.65 


2.75 


2.84 


2.94 


3.03 


3.13 


3.22 


3.31 


.6 . . 


2.32 


2 42 


2.52 


2.62 


2.71 


2.81 


2.91 


3. 


3.1 


3.2 


3.29 


3.39 


.625 . 


2.37 


2.47 


2.57 


2.67 


2.77 


2.87 


2.97 


3.06 


3.16 


3.26 


3.36 


3.46 


.65 . . 


2.42 


2.52 


2.62 


2.72 


2.82 


2.92 


3.02 


3.13 


3.23 


3.33 


3.43 


3.53 


.675 . 


2.46 


2.57 


2.67 


2.77 


2.88 


2.98 


3.08 


3.19 


3.29 


3.39 


3.49 


3.59 


.7 . . 


2.51 


2.62 


2.72 


2.82 


2.93 


3.03 


3.14 


3.24 


3.35 


3.45 


3.56 


3.66 


.725 . 


2.56 


2.66 


2.77 


2.87 


2.98 


3.09 


3.19 


3.3 


3.41 


3.51 


3.62 


3.73 


.75 . . 


2.6 


2.71 


2.81 


2.92 


3.03 


3.14 


3.25 


3.36 


3.46 


3.57 


3.68 


3.79 


.8 . . 


2.68 


2.8 


2.91 


3.02 


3.13 


3.24 


3.35 


3.47 


3.58 


3.69 


3.8 


3.91 


.85 . . 


2.77 


2.88 


3. 


3.11 


3.23 


3.34 


3.46 


3.57 


3.69 


3.81 


3.92 


4.03 


.9 . . 


2.84 


2.97 


3.09 


3.2 


3.32 


3.44 


3.56 


3.68 


3.8 


3.91 


4.03 


4.15 


.95 . . 


2.92 


3.05 


3.17 


3.29 


3.41 


3.53 


3.66 


3.78 


3.9 


4.02 


4.14 


4.26 


1. . . . 


3. 


3.13 


3.25 


3.38 


3.5 


3.63 


3.75 


3.88 


4. 


4.13 


4.25 


4.38 


1.05 . . 


3.07 


3.2 


3.33 


3.46 


3.59 


3.72 


3.84 


3.97 


4.1 


4.23 


4.36 


4.48 


1.1 . . 


3.14 


3.28 


3.41 


3.54 


3.67 


3.8 


3.93 


4.06 


4.2 


4.33 


4.46 


4.59 


1.15 . . 


3.21 


3.35 


3.49 


3.62 


3.75 


3.89 


4.02 


4.16 


4.29 


4.42 


4.56 


4.69 


1.2 . . 


3.28 


3.44 


3.58 


3.72 


3.85 


3.99 


4.13 


4.27 


4.4 


4.54 


4.68 


4.82 


1.25 . . 


3.35 


3.49 


3.63 


3.77 


3.91 


4.05 


4.19 


4.32 


4.47 


4.61 


4.75 


4.89 


1.3 . . 


3.42 


3.56 


3.71 


3.85 


3.99 


4.13 


4.28 


4.42 


4.56 


4.7 


4.85 


4.99 


1.35 . . 


3.49 


3.68 


3.78 


3.92 


4.07 


4.21 


4.36 


4.5 


4.65 


4.79 


4.94 


5.08 


1.4 . . 


3.55 


3.7 


3.85 


3.99 


4.14 


4.29 


4.44 


4.59 


4.73 


4.88 


5.03 


5.18 


1.45 . . 


3.61 


3.76 


3.91 


4.07 


4.22 


4.37 


4.52 


4.67 


4.82 


4.97 


5.12 


5.27 


1.5 . . 


3.67 


3.83 


3.98 


4.13 


4.29 


4.44 


4.59 


4.75 


4.9 


5.05 


5.21 


5.36 


1.6 . . 


3.85 


3.95 


4.11 


4.27 


4.43 


4.59 


4.75 


4.9 


5.06 


5.22 


5.38 


5.53 


1.7 . . 


3.91 


4.08 


4.24 


4.4 


4.56 


4.73 


4.89 


5.05 


5.22 


5.38 


5.54 


5.71 


1.8 . . 


4.02 


4.19 


4.36 


4.53 


4.7 


4.86 


5.03 


5.2 


5.37 


5.54 


5.7 


5.87 


1.9 . . 


4.14 


4.31 


4.48 


4.65 


4.8S 


5. 


5.17 


5.34 


5.51 


5.69 


5.86 


6.03 


2. . . . 


4.25 


4.42 


4.6 


4.77 


4.95 


5.13 


5.31 


5.48 


5.66 


5.83 


6.01 


6.19 



The above numbers (in the body of the table) are corrected lengths, Lc. 



WINDING OF ELECTROMAGNETS. 



119 



Table IHc. — JFor correcting* T^ng-t Ii of Magpiet Coil. 



Ix 


Length of Test Coil, Lt. 


Ih 


4i 


4| 


41 


41 


5 


5i 


5* 


51 


5* 


51 


51 


51 


.5 . . 


3.18 


3.27 


3.36 


3.45 


3.54 


3.62 


3.71 


3.8 


3.89 


3.98 


4.07 


4.16 


.525 . 


3.26 


3.35 


3.44 


3.53 


3.62 


3.71 


3.81 


3.9 


3.99 


4.08 


4.17 


4.26 


.55 . . 


3.34 


3.43 


3.52 


3.62 


3.71 


3.8 


3.9 


3.99 


4.08 


4.17 


4.27 


4.36 


.575 . 


3.41 


3.51 


3.6 


3.7 


3.79 


3.89 


3.98 


4.08 


4.17 


4.27 


4.36 


4.46 


.6 . . 


3.49 


3.58 


3.68 


3.78 


3.87 


3.97 


4.07 


4.16 


4.26 


4.36 


4.46 


4.55 


.625 . 


3.56 


3.66 


3.76 


3.86 


3.95 


4.05 


4.15 


4.25 


4.35 


4.45 


4.55 


4.65 


.65 . . 


3.63 


3.73 


3.83 


3.93 


4.03 


4.13 


4.23 


4.33 


4.43 


4.54 


4.64 


4.74 


.675 . 


3.7 


3.8 


3.9 


4.01 


4.11 


4.21 


4.31 


4.42 


4.52 


4.62 


4.72 


4.83 


.7 . . 


3.77 


3.87 


3.97 


4.08 


4.78 


4.29 


4.39 


4.5 


4.6 


4.71 


4.81 


4.92 


.725 . 


3.83 


3.94 


4.04 


4.15 


4.26 


4.37 


4.47 


4.58 


4.68 


4.79 


4.9 


5.0 


.75 . . 


3.9 


4.01 


4.11 


4.22 


4.33 


4.44 


4.55 


4.66 


4.76 


4.87 


4.98 


5.09 


.775 . 


4.01 


4.07 


4.18 


4.29 


4.4 


4.51 


4.62 


4.73 


4.84 


4.95 


5.06 


5.17 


.8 . . 


4.03 


4.14 


4.25 


4.36 


4.47 


4.58 


4.7 


4.81 


4.92 


5.03 


5.14 


5.25 


.825 . 


4.09 


4.2 


4.32 


4.43 


4.54 


4.66 


4.77 


4.88 


5. 


5.11 


5.22 


5.34 


.85 . . 


4.15 


4.27 


4.38 


4.5 


4.61 


4.73 


4.84 


4.96 


5.07 


5.19 


5.3 


5.42 


.875 . 


4.21 


4.33 


4.44 


4.56 


4.68 


4.8 


4.91 


5.03 


5.15 


5.26 


5.38 


5.5 


.9 . . 


4.27 


4.39 


4.51 


4.63 


4.74 


4.86 


4.98 


5.1 


5.22 


5.34 


5.46 


5.57 


.925 . 


4.33 


4.45 


4.57 


4.69 


4.81 


4.93 


5.05 


5.17 


5.29 


5.41 


5.53 


5.65 


.95 . . 


4.39 


4.51 


4.63 


4.75 


4.87 


5. 


5.12 


5.24 


5.36 


5.48 


5.61 


5.73 


1. . . . 


4.5 


4.63 


4.75 


4.88 


5. 


5.13 


5.25 


5.38 


5.5 


5.63 


5.75 


5.88 


1.05 . . 


4.61 


4.74 


4.87 


5. 


5.12 


5.25 


5.38 


5.51 


5.64 


5.76 


5.89 


6.02 


1.1 . . 


4.72 


4.85 


4.98 


5.11 


5.25 


5.38 


5.51 


5.64 


5.77 


5.9 


6.03 


6.16 


1.15 . . 


4.83 


4.96 


5.09 


5.23 


5.36 


5.5 


5.63 


5.76 


5.9 


6.03 


6.17 


6.3 


1.2 . . 


4.96 


5.07 


5.2 


5.34 


5.48 


5.61 


5.75 


5.89 


6.03 


6.16 


6.3. 


6.44 


1.25 . . 


5.03 


5.17 


5.31 


5.45 


5.59 


5.73 


5.87 


6.01 


6.15 


6.29 


6.43 


6.57 


1.3 . . 


5.13 


5.27 


5.42 


5.56 


5.7 


5.84 


5.99 


6.13 


6.27 


6.41 


6.56 


6.7 


1.35 . . 


5.23 


5.37 


5.52 


5.67 


5.81 


5.96 


6.1 


6.25 


6.39 


6.54 


6.68 


6.83 


1.4 . . 


5.33 


5.47 


5.62 


5.77 


5.92 


6.07 


6.21 


6.36 


6.51 


6.66 


6.81 


6.95 


1.45 . . 


5.42 


5.57 


5.72 


5.87 


6.02 


6.17 


6.32 


6.47 


6.62 


6.77 


6.93 


7.08 


1.5 . . 


5.51 


5.67 


5.82 


5.97 


6.12 


6.28 


6.43 


6.58 


6.74 


6.89 


7.04 


7.2 


1.55 . . 


5.6 


5.76 


5.91 


6.07 


6.23 


6.38 


6.54 


6.69 


6.85 


7. 


7.16 


7.32 


1.6 . . 


5.69 


6.85 


6.01 


6.17 


6.33 


6.48 


6.64 


6.8 


6.96 


7.12 


7.27 


7.43 


1.65 . . 


5.78 


5.94 


6.1 


6.26 


6.42 


6.58 


6.74 


6.91 


7.07 


7.23 


7.39 


7.55 


1.7 . . 


5.87 


6.03 


6.19 


6.36 


6.52 


6.68 


6.85 


7.01 


7.17 


7.33 


7.5 


7.66 


1.75 . . 


5.96 


6.12 


6.28 


6.45 


6.61 


6.78 


6.95 


7.11 


7.28 


7.44 


7.61 


7.77 


1.8 . . 


6.04 


6.21 


6.37 


6.54 


6.71 


6.88 


7.05 


7.21 


7.38 


7.55 


7.72 


7.88 


1.85 . . 


6.12 


6.29 


6.46 


6.63 


6.8 


6.97 


7.14 


7.31 


7.48 


7.65 


7.82 


7.99 


1.9 . . 


6.2 


6.38 


6.55 


6.72 


6.89 


7.07 


7.24 


7.41 


7.58 


7.75 


7.93 


8.1 


1.95 . . 


6.28 


6.46 


6.63 


6.81 


6.98 


7.16 


7.33 


7.51 


7.68 


7.86 


8.03 


8.21 


2. . . . 


6.37 


6.54 


6.72 


6.9 


7.07 


7.25 


7.42 


7.6 


7.78 


7.96 


8.13 


8.31 



The above numbers (in the body of the table) are corrected lengths, he. 



120 



ELECTKOM AGNETS . 



Table Hid. — Vor correcting* JLeiig-rf i of >1 ag-net Coil. 



lx 










Length of Test Coil, 


U 








Ih 


6 


6* 


6i 


6| 


6i 


6| 


6f 


61 


7 


7£ 


7i 


71 


.5 . . 


4.24 


4.33 


4.44 


4.51 


4.6 


4.69 


4.77 


4.86 


4.95 


5.04 


5.13 


5.22 


.525 . 


4.35 


4.44 


4.53 


4.62 


4.71 


4.8 


4.89 


4.98 


5.07 


5.16 


5.25 


5.34 


.55 . . 


4.45 


4.54 


4.64 


4.73 


4.82 


4.91 


5.01 


5.1 


5.19 


5.29 


5.38 


5.47 


.575 . 


4.55 


4.65 


4.74 


4.83 


4.93 


5.02 


5.12 


5.21 


5.31 


5.4 


5.5 


5.59 


.6 . . 


4.65 


4.75 


4.84 


4.94 


5.04 


5.13 


5.23 


5.33 


5.42 


5.52 


5.62 


5.71 


.625 . 


4.75 


4.84 


4.94 


5.04 


5.14 


5.24 


5.34 


5.44 


5.53 


5.63 


5.73 


5.83 


.65 . . 


4.84 


4.94 


5.04 


5.14 


5.24 


5.34 


5.44 


5.54 


5.64 


5.75 


5.85 


5.95 


.675 . 


4.93 


5.03 


5.14 


5.24 


5.34 


5.44 


5.55 


5.65 


5.75 


5.85 


5.96 


6.06 


.7 . . 


5.02 


5.13 


5.23 


5.33 


5.44 


5.54 


5.65 


5.75 


5.86 


5.96 


6.07 


6.17 


.725 . 


5.11 


5.22 


5.32 


5.43 


5.53 


5.64 


5.75 


5.86 


5.96 


6.07 


6.17 


6.28 


.75 . . 


5.2 


5.3 


5.41 


5.52 


5.63 


5.74 


5.85 


5.95 


6.06 


6.17 


6.28 


6.39 


.775 . 


5.28 


5.39 


5.5 


5.61 


5.72 


5.83 


5.94 


6.05 


6.16 


6.27 


6.39 


6.49 


.8 . . 


5.37 


5.48 


5.59 


5.7 


5.81 


5.93 


6.04 


6.15 


6.26 


6.37 


6.49 


6.6 


.825 . 


5.45 


5.56 


5.68 


5.79 


5.91 


6.02 


6.13 


6.25 


6.36 


6.47 


6.59 


6.7 


.85 . . 


5.53 


5.65 


5.76 


5.88 


5.99 


6.11 


6.22 


6.34 


6.45 


6.57 


6.69 


6.8 


.875 . 


5.61 


5.73 


5.85 


5.96 


6.08 


6.2 


6.31 


6.43 


6.55 


6.67 


6.78 


6.9 


.9 . . 


5.69 


5.81 


5.93 


6.05 


6.17 


6.29 


6.4 


6.52 


6.64 


6.75 


6.88 


7. 


.925 . 


5.77 


5.89 


6.01 


6.13 


6.25 


6.37 


6.49 


6.61 


6.73 


6.85 


6.97 


7.09 


.95 . . 


5.85 


5.97 


6.09 


6.21 


6.34 


6.46 


6.58 


6.7 


6.82 


6.95 


7.07 


7.19 


1. . . . 


6. 


6.13 


6.25 


6.38 


6.5 


6.63 


6.75 


6.88 


7. 


7.13 


7.25 


7.38 


1.05 . . 


6.15 


6.28 


6.41 


6.53 


6.66 


6.79 


6.92 


7.05 


7.17 


7.3 


7.43 


7.56 


1.1 . . 


6.29 


6.43 


4.56 


6.69 


6.82 


6.95 


7.08 


7.21 


7.34 


7.47 


7.61 


7.74 


1.15 . . 


6.44 


6.57 


6.7 


6.84 


6.97 


7.11 


7.24 


7.37 


7.51 


7.64 


7.78 


7.91 


1.2 . . 


6.57 


6.71 


6.85 


6.99 


7.12 


7.26 


7.39 


7.53 


7.67 


7.81 


7.94 


8.08 


1.25 . . 


6.71 


6.85 


6.99 


7.13 


7.27 


7.41 


7.55 


7.69 


7.83 


7.97 


8.11 


8.25 


1.3 . . 


6.84 


6.98 


7.13 


7.27 


7.41 


7.55 


7.7 


7.84 


7.98 


8.13 


8.27 


8.41 


1.35 . . 


6.97 


7.12 


7.26 


7.41 


7.55 


7.7 


7.84 


7.99 


8.13 


8.28 


8.43 


8.57 


1.4 . . 


7.1 


7.25 


7.4 


7.54 


7.69 


7.84 


7.99 


8.13 


8.28 


8.43 


8.58 


8.73 


1.45 . . 


7.23 


7.38 


7.53 


7.68 


7.83 


7.98 


8.13 


8.28 


8.43 


8.58 


8.73 


8.88 


1.5 . . 


7.35 


7.5 


7.66 


7.81 


7.96 


8.11 


8.27 


8.42 


8.57 


8.73 


8.88 


9.03 


1.55 . . 


7.47 


7.63 


7.78 


7.94 


8.09 


8.25 


8.4 


8.56 


8.72 


8.87 


9.03 


9.18 


1.6 . . 


7.59 


7.75 


7.91 


8.07 


8.22 


8.38 


8.54 


8.7 


8.86 


9.01 


9.17 


9.33 


1.65 . . 


7.71 


7.87 


8.03 


8.19 


8.35 


8.51 


8.67 


8.83 


8.99 


9.15 


9.31 


9.47 


1.7 . . 


7.82 


7.99 


8.15 


8.31 


8.48 


8.64 


8.8 


8.96 


9.13 


9.29 


9.45 


9.62 


1.75 . . 


7.94 


8.1 


8.27 


8.43 


8.6 


8.77 


8.93 


9.09 


9.26 


9.43 


9.59 


9.76 


1.8 . . 


8.05 


8.22 


8.39 


8.55 


8.72 


8.89 


9.06 


9.22 


9.39 


9.56 


9.73 


9.9 


1.85 . . 


8.16 


8.33 


8.5 


8.67 


8.84 


9.01 


9.18 


9.35 


9.52 


9.69 


9.86 


10.03 


1.9 . . 


8.27 


8.44 


8.62 


8.79 


8.96 


9.13 


9.3 


9.48 


9.65 


9.82 


9.99 


10.17 


1.95 . . 


8.38 


8.55 


8.73 


8.9 


9.08 


9.25 


9.43 


9.6 


9.78 


9.95 


10.13 


10.3 


2. . . . 


8.49 


8.66 


8.84 


9.02 


9.19 


9.37 


9.55 


9.72 


9.9 


10.08 


10.25 


10.43 



The above numbers (in the body of the table) are corrected lengths, Lc» 



WINDING OF ELECTROMAGNETS. 



121 



Table IVa.-Iinear Space occupied toy Single Cotton- 
Covered Wires. 



Turns 

or 
Layers. 



Wire Numbers, B. & S. Gauge : 



6 



.432 
648 
864 
08 
296 
512 
728 
994 
16 
38 
59 
81 
03 
24 
46 
67 
89 
11 
32 
53 
75 
97 



.388 
,582 
,776 
,97 
164 
358 
552 
746 
94 
,14 
33 
52 
,72 
,91 
.11 
3 

,49 
,69 
.88 
07 
27 
46 
65 
.85 
.05 



344 

516 

688 

86 

032 

204 

376 

548 

72 

89 

07 

24 

41 

58 

75 

93 

1 

27 

44 

61 

78 

95 

125 

3 

47 

64 

81 

98 

16 



.308 
.462 
.616 
.77 
.924 
,078 
232 
386 
.54 
,69 

.85 

!l6 
.31 
.47 
.62 
.77 
.93 
.08 
.24 
.39 
.54 
.69 
.85 

.16 
.31 
.46 
.62 

.77 
.93 
.08 



,274 
,411 
,548 
685 
822 
959 
096 
233 
37 
51 
64 
78 
92 
06 
19 
33 
,47 
61 
,74 
,88 
02 
15 
29 
43 
56 
,7 
83 
97 
11 
25 
38 
52 
65 
79 
93 
07 



9 

~244 
366 

488 

61 

732 

854 

976 

098 

22 

34 

47 

59 

71 

83 

95 

06 

2 

32 

44 

56 

69 

81 

93 

05 

17 

29 

41 

54 

66 

78 

9 

02 

14 

27 

39 

51 

63 

76 

88 



10 

.216 

.324 

.432 

.54 

.648 

.756 

.864 

.972 

.08 

.19 

.3 

.41 

.51 

.62 

.73 

.84 

.95 

.05 

.16 

.27 

.38 

.49 

.59 

.7 

.81 

.92 

.03 

.13 

.24 

.35 

.45 

.56 

.67 

.78 

.89 

.99 

.1 

.21 

.32 

.42 

.53 

.64 
.75 

.86 
.97 



11 

7l94 
.291 
.388 
.485 
.582 
.679 
.776 
.873 
.97 
,07 
,17 
,26 
.36 
.46 
.55 
,65 
.75 
.85 
,94 
.04 
.14 
,23 

33 
,43 
,52 
,62 
,72 

82 

91 

,1 
2 

,29 

39 
,49 

59 

,68 
,78 
,88 
,97 

07 
,17 
,27 

36 

46 

56 

66 

76 
,85 



12 

7l74 
,261 
.348 
,435 
,522 
,609 
.696 
.783 
,87 
.96 
05 
,13 
22 
31 
39 
,48 
,57 
66 
.74 
83 
92 

!09 
,18 
,26 

35 
44 
53 
61 
,7 
79 
87 
96 
04 
13 
22 
3 

39 
48 
56 

65 
74 
83 
91 



13 14 



0.14 
0.21 
0.28 
0.35 
0.42 

0.49 
0.56 
0.63 
0.7 
0.77 
0.84 
0.91 
.98 
1.05 
1.12 
1.19 
1.26 
1.33 
1.4 
1.4* 
1.54 
1.61 
1.68 
1.75 
1.82 
1.89 
1.96 
2.03 
2.1 
2.17 
2.24 
2.31 
2.38 
2.45 
2.52 

2.59 

2.66 

2.73 

2.8 

2.87 

2.94 

3.01 

3.08 

3.15 

3.22 

3.29 

3.36 

3.43 

3.5 

3.64 

3.78 

3.92 

4.06 

4.2 

4.34 

4.48 



122 



ELECTROMAGNETS. 



TA BLE IVl>.- Linear Space occupied by Single Cotton- 
Covered Wires. 



Turns or 
Layers. 



Wire Numbers, B. & S. Gauge : 



15 

0.38 

0.44 

0.5 

0.57 

0.63 



0.75 

0.82 

0.88 

0.95 

1.01 

1.07 

1.13 

1.2 

1.26 

1.32 

1.39 

1.45 

1.51 

1.57 

1.64 

1.7 

1.76 

1.83 

1 

1.95 

2.02 

2.08 

2.14 

2.2 

2.27 

2.33 

2.39 

2.46 

2.52 

2.58 

2.65 

2.71 

2.77 

2.83 

2 

2.96 

3.02 

3.09 

3.15 

3.27 

3.4 

3.53 

3.65 

3.78 

3.91 

4.03 

4.16 

4.28 

4.41 



16 



17 



0.34 

0.4 

0.46 

0.51 

0.57 

0.63 

0.68 

0.74 

0.8 

0.85 

0.91 

0.97 

1.03 

1.08 

1.14 

1.2 

1.25 

1.31 

1.37 

1.42 

1.48 

1.54 

1.6 

1.65 

1.71 

1.77 

1.82 

1.88 

1.94 

2. 

2.05 

2.11 

2.17 

2.22 

2.28 

2.34 

2.39 

2.45 

2.51 

2.56 

2.62 

2 

2.73 

2.79 

2.85 

2.96 

3.08 

3.19 

3.31 

3.42 

3.53 

3.65 

3.76 

3 

3.99 



18 



0.31 

0.36 

0.41 

0.46 

0.51 

0.56 

0.61 

0.66 

0.71 

0.76 

0.82 

0.87 

0.92 

0.97 

1.02 

1.07 

1.12 

1.17 

1.22 

1.27 

1.33 

1.38 

1.43 

1.48 

1.53 

1.58 

1.63 

1.68 

1.73 

1.78 

1.84 

1. 

1.94 

1 

2.04 

2.09 

2.14 

2.19 

2.24 

2.29 

2.35 

2.4 

2.45 

2.5 

2.55 

2.65 

2.75 

2 

2.96 

3.06 

3.16 

3.26 

3.37 

3.47 

3.57 



19 



0.28 

0.32 

0.37 

0.41 

0.46 

0.51 

0.55 

0.6 

0.64 

0.69 

0.74 

0.78 

0.83 

0.87 

0.92 

0.97 

1.01 

1.06 

1.1 

1.15 

1.2 

1.24 

1.29 

1.33 

1.38 

1.43 

1.47 

1.52 

1.56 

1.61 

1.66 

1.7 

1.75 

1.79 

1.84 

1.89 

1.93 

1.98 

2.02 

2.07 

2.12 

2.16 

2.21 

2.25 

2.3 

2.39 

2.48 

2.58 

2.67 

2.76 

2.85 
2.94 
3.04 
3.13 
3.22 



20 



0.25 

0.29 

0.34 

0.38 

0.42 

0.46 

0.5 

0.55 

0.59 

0.63 

0.67 

0.72 

0.76 



0.84 

0.88 

0.92 

0.97 

1.01 

1.05 

1.09 

1.13 

1.18 

1.22 

1.26 

1.3 

1.34 
1.39 
1.43 
1.47 

1.51 

1.55 

1 

1.64 

1.68 

1.72 

1.76 

1.81 

1.85 

1.89 

1.93 

1.97 

2.02 

2.06 

2.1 

2.18 

2.27 

2.35 

2.44 

2.52 

2.6 

2.69 

2.77 

2.86 

2.94 



21 



0.23 

0.27 

0.3 

0.34 

0.38 

0.42 

0.46 

0.49 

0.53 

0.57 

0.61 

0.65 

0.68 

0.72 

0.76 

0.8 

0.84 

0.87 

0.91 

0.95 

0.99 

1.03 

1.06 

1.1 

1.14 

1.18 

1.22 

1.25 

1.29 

1.33 

1.37 

1.41 

1.44 

1.48 

1.52 

1.56 

1.6 

1.63 

1.67 

1.71 

1.75 

1.79 

1.82 

1.8' 

1.9 

1.98 

2.05 

2.13 



22 



2 

2.28 
2.36 
2.43 
2.51 
2.58 
2.66 



0.2 

0.24 

0.27 

0.31 

0.34 

0.37 

0.41 

0.44 

0.48 

0.51 

0.54 

0.58 

0.61 

0.65 



0.71 

0.75 

0.78 

0.82 

0.85 

0.88 

0.92 

0.95 

0.99 

1.02 

1.05 

1.09 

1.12 

1.16 

1.19 

1.22 

1.26 

1.29 

1.33 

1.36 

1.39 

1.43 

1.46 

1.5 

1.53 

1.56 

1 

1.63 

1.67 

1.7 

1.77 

1.84 

1.9 

1.97 

2.04 

2.11 
2.18 
2.24 
2.31 
2.38 



23 



0.19 

0.22 

0.25 

0.28 

0.31 

0.34 

0.37 

0.4 

0.43 

0.46 

0.5 

0.53 

0.56 

0.59 

0.62 

0.65 

0.68 

0.71 

0.74 

0.78 

0.81 

0.84 

0.87 

0.9 

0.93 

0.96 

0.99 

1.02 

1.05 

1.08 

1.12 
1.15 
1.18 
1.21 
1.24 

1.27 

1.3 

1.33 

1.36 

1.39 

1.43 



24 



46 

49 

52 

55 

61 

67 

1.74 

1.8 

1.86 

1.92 

1. 

2.05 

2.11 

2.17 



0.17 

0.2 

0.22 

0.25 

0.28 

0.31 
0.34 
0.36 
0.39 
0.42 

0.45 

0.48 

0.5 

0.53 

0.56 

0.59 

0.62 

0.64 

0.67 

0.7 

0.73 

0.76 

0.78 

0.81 

0.84 

0.87 

0.9 

0.93 

0.95 

0.98 

1.01 
1.04 
1.06 
1.09 
1.12 

1.15 

1.18 

1.2 

1.23 

1.26 

1.29 

1.32 

1.34 

1.37 

1.4 

1.46 

1.51 

1.57 

1.62 

1 

1.74 

1.79 

1.85 

1.9 

1.96 



0.15 

0.17 

0.2 

0.22 

0.25 

0.27 

0.3 

0.33 

0.35 

0.38 

0.4 

0.42 

0.45 

0.47 

0.5 

0.52 

0.55 

0.57 

0.6 

0.62 

0.65 

0.67 

0.7 

0.72 

0.75 

0.77 

0.8 

0.82 

0.85 

0.87 

0.9 

0.92 

0.95 

0.97 

1. 

1.02 

1.05 

1.07 

1.1 

1.12 

1.15 

1.17 

1.2 

1.22 

1.25 



1 


3 


1 


35 


1 


4 


1 


45 


1 


5 


1 


55 


1 


.6 


1 


65 


1 


« 


1 


.75 



WINDING OF ELECTROMAGNETS. 



123 



Table IVc. — Linear Space occupied by Single Cotton- 
Covered Wires. 







Wire Numbers, 


B. &S. 


Gauge : 






Turns or 


















Layers. 




















17 


18 


19 


20 


21 


22 


23 


24 


72 


3.67 


3.31 


3.02 


2.74 


2.45 


2.23 


2.02 


1.8 


74 


3.77 


3.4 


3.11 


2.81 


2.52 


2.29 


2.07 


1.85 


76 


3.88 


3.5 


3.19 


2.89 


2.58 


2.36 


2.13 


1.9 


78 


3.98 


3.58 


3.28 


2.96 


2.65 


2.42 


2.18 


1.95 


80 .... . 


4.08 


3.68 


3.36 


3.04 


2.72 


2.48 


2.24 


2. 


82 


4.18 


3.77 


3.44 


3.12 


2.79 


2.54 


2.3 


2.05 


84 


4.28 


3.86 


3.53 


3.19 


2.86 


2.6 


2.35 


2.1 


86 


4.39 


3.96 


3.61 


3.27 


2.92 


2.67 


2.41 


2.15 


88 


4.49 


4.05 


3.7 


3.34 


2.99 


2.73 


2.46 


2.2 


90 


4.59 


4.14 


3.78 


3.42 


3.06 


2.79 


2.52 


2.25 


92 




4.23 


3.86 


3.5 


3.13 


2.85 


2.58 


2.3 


94 




4.32 


3.95 


3.57 


3.2 


2.91 


2.63 


2.35 


96 




4.42 


4.03 


3.65 


3.26 


2.98 


2.69 


2.4 


98 




4.51 


4.12 


3.72 


3.33 


3.04 


2.74 


2.45 


100 




4.6 


4.2 


3.8 


3.4 


3.1 


2.8 


2.5 


102 






4.28 


3.88 


3.47 


3.16 


2.86 


2.55 


104 






4.37 


3.95 


3.54 


3.22 


2.91 


2.6 


106 






4.45 


4.03 


3.6 


3.29 


2.97 


2.65 


108 






4.54 


4.1 


3.67 


3.35 


3.02 


2.7 


110 








4.18 


3.74 


3.41 


3.08 


2.75 


112 








4.26 


3.81 


3.47 


3.14 


2.8 


114 








4.33 


3.88 


3.53 


3.19 


2.85 


116 








4.41 


3.94 


3.6 


3.25 


2.9 


118 








4.48 


4.01 


3.66 


3.3 


2.95 


120 








4.56 


4.08 


3.72 


3.36 


3. 



Table IVd. — Linear Space occupied by Double Cotton- 
Covered Wires. 





Wire Numbers, B. & S. Gauge: 


Turns or 




Layers. 


























4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


2. . . 


0.444 


0.4 


0.356 


0.32 


0.284 


0.252 


0.224 


0.202 


0.182 


0.16 


0.15 


3. . . 


0.666 


0.6 


0.534 


0.48 


0.426 


0.378 


0.336 


0.303 


0.273 


0.24 


0.22 


4. . . 


0.888 


0.8 


0.712 


0.64 


0.568 


0.504 


0.448 


0.404 


0.364 


0.32 


0.29 


5. . . 


1.11 


1. 


0.89 


0.8 


0.71 


0.63 


0.56 


0.505 


0.455 


0.4 


0.36 


6. . . 


1.332 


1.2 


1.068 


0.96 


0.852 


0.756 


0.672 


0.606 


0.546 


0.49 


0.44 


7. . . 


1.554 


1.4 


1.246 


1.12 


0.994 


0.882 


0.784 


0.707 


0.637 


0.57 


0.51 


8. . . 


1.776 


1.6 


1.424 


1.28 


1.136 


1.008 


0.896 


0.808 


0.728 


0.65 


0.58 


9. . . 


1.998 


1.8 


1.602 


1.44 


1.278 


1.134 


1.008 


0.909 


0.819 


0.73 


0.66 


10. . . 


2.22 


2. 


1.78 


1.6 


1.42 


1.26 


1.12 


1.01 


0.91 


0.81 


0.73 


11. . . 


2.442 


2.2 


1.958 


1.76 


1.562 


1.386 


1.232 


1.111 


1.001 


0.89 


0.8 



124 



ELECTROMAGNETS. 



Table I Vd. — Linear Space occupied by Double Cotton- 
Covered "Wires. — Continued. 



Turns or 
Layers. 



Wire Numbers, B. & S. Gauge: 



2.664 

2 
108 
33 
55 



136 

314 

492 

67 

85 



3.03 

3.2 

3.38 

3.56 

3.74 

3.92 

4.09 
4.27 
4.45 
4.63 

4.81 
4.98 



1.92 

2.08 

2.24 

2.4 

2.56 

2.72 

2.88 

3.04 

3.2 

3.36 

3.52 

3.68 

3.84 

4. 

4.16 

4.32 

4.48 

4.64 

4.8 

4.96 



1.704 

1.846 

1.988 

2.13 

2.27 

2.41 
2.56 
2.77 
2.84 
2.98 

3.12 
3.27 
3.41 
3.55 
3.69 

3.83 

3.98 
4.12 
4.2 
4.4 

4.54 
4.6 
4.8 
4.97 



1.512 

1.638 

1.764 

1.89 

2.01 

2.14 
2.27 
2.39 
2.52 
2.65 

2.77 

2.9 

3.02 

3.15 

3.28 

3.4 

3.53 

3.65 

3.78 

3.91 

4.03 
4.16 

4.28 
4.41 
4.54 

4.66 
4.79 
4.91 
5.04 



10 



1.344 

1.456 

1.568 

1.68 

1.79 

1.9 

2.02 
2.13 
2.24 
2.35 

2.46 

2.58 

2.69 

2.8 

2.91 

3.02 
3.14 
3.25 
3.36 
3.47 

3.58 

3.7 

3.81 

3.92 

4.03 

4.14 
4.26 
4.37 
4.48 
4.59 

4.7 
4.82 
4.93 
5.04 



11 12 13 14 



1.212 

1.313 

1.414 

1.51 

1.62 

1.72 

1.82 
1.92 
2.02 
2.12 

2.22 
2.32 
2.42 
2.53 
2.63 

2.73 

2.83 
2.93 
3.03 
3.13 

3.23 
3.33 
3.43 
3.54 
3.64 

3.74 
3.84 
3.94 
4.04 
4.14 

4.24 
4.34 
4.44 
4.55 
4.65 

4.75 

4.85 



1.092 

1.183 

1.274 

1.36 

1.46 

1.55 
1.64 
1.73 
1.82 
1.91 

2. 
2.09 

2.18 
2.28 
2.37 

2.46 
2.55 
2.64 
2.73 
2.82 

2.91 

3. 

3.09 

3.19 

3.28 

3.37 
3.46 
3.55 
3.64 
3.73 



4.28 
4.37 
4.46 
4.55 
4.73 

4.91 



WINDING OF ELECTROMAGNETS. 



125 



Table IVe. — linear Space occupied by Double Cotton- 
Covered Hires. 









Wire Numbers 


B. and S. Gauge: 






Turns or 






















Layers. 
























15 


16 


17 


18 


19 


20 


21 


22 


23 


24 


7 . . . . 


0.46 


0.42 


0.38 


0.35 


0.32 


0.29 


0.26 


0.24 


0.22 


0.2 


8 . . . . 


0.53 


0.48 


0.43 


0.4 


0.36 


0.33 


0.3 


0.27 


0.25 


0.23 


9 . . . . 


0.59 


0.54 


0.49 


0.45 


0.4 


0.37 


0.34 


0.31 


0.28 


0.26 


10 ... . 


0.66 


0.6 


0.54 


0.5 


0.45 


0.41 


0.37 


0.34 


0.31 


0.28 


11 ... . 


0.73 


0.66 


0.59 


0.55 


0.5 


0.45 


0.41 


0.38 


0.34 


0.31 


12 ... . 


0.79 


0.72 


0.65 


0.59 


0.54 


0.49 


0.45 


0.41 


0.37 


0.34 


13 ... . 


0.86 


0.78 


0.71 


0.65 


0.59 


0.53 


0.49 


0.44 


0.41 


0.37 


14 ... . 


0.92 


0.84 


0.76 


0.69 


0.63 


0.58 


0.53 


0.48 


0.43 


0.39 


15 ... . 


0.99 


0.9 


0.81 


0.74 


0.68 


0.62 


0.56 


0.51 


0-.47 


0.42 


16 ... . 


1.06 


0.96 


0.86 


0.79 


0.72 


0.66 


0.6 


0.54 


0.5 


0.45 


17 ... . 


1.12 


1.02 


0.92 


0.84 


0.77 


0.7 


0.64 


0.58 


0.53 


0.48 


18 ... . 


1.19 


1.08 


0.97 


0.89 


0.81 


0.74 


0.86 


0.61 


0.56 


0.51 


19 ... . 


1.25 


1.14 


1.03 


0.94 


0.86 


0.78 


0.71 


0.65 


0.59 


0.53 


20 ... . 


1.32 


1.2 


1.08 


0.99 


0.9 


0.82 


0.75 


0.68 


0.62 


0.56 


21 ... . 


1.39 


1.26 


1.13 


1.04 


0.95 


0.86 


0.79 


0.72 


0.65 


0.59 


22 ... . 


1.45 


1.32 


1.19 


1.09 


0.99 


0.9 


0.83 


0.75 


0.68 


0.62 


23 ... . 


1.52 


1.38 


1.24 


1.14 


1.04 


0.94 


0.86 


0.78 


0.72 


0.65 


24 ... . 


1.58 


1.44 


1.3 


1.19 


1.08 


0.98 


0.9 


0.82 


0.75 


0.67 


25 ... . 


1.65 


1.5 


1.35 


1.24 


1.13 


1.03 


0.94 


0.85 


0.78 


0.7 


26 ... . 


1.72 


1.56 


1.4 


1.29 


1.17 


1.07 


0.98 


0.88 


0.81 


0.73 


27 ... . 


1.78 


1.62 


1.46 


1.34 


1.22 


1.11 


1.01 


0.92 


0.84 


0.76 


28 ... . 


1.85 


1.68 


1.51 


1.39 


1.26 


1.15 


1.05 


0.95 


0.87 


0.79 


29 ... . 


1.91 


1.74 


1.57 


1.44 


1.31 


1.19 


1.09 


0.99 


0.9 


0.81 


30 ... . 


1.98 


1.8 


1.62 


1.49 


1.35 


1.23 


1.13 


1.02 


0.93 


0.84 


31 ... . 


2.05 


1.86 


1.68 


1.54 


1.4 


1.27 


1.16 


1.06 


0.96 


0.87 


32 ... . 


2.11 


1.92 


1.73 


1.58 


1.44 


1.31 


1.2 


1.09 


0.99 


0.9 


33 ... . 


2.18 


1.98 


1.78 


1.63 


1.49 


1.35 


1.24 


1.12 


1.02 


0.92 


34 ... . 


2.25 


2.04 


1.84 


1.68 


1.53 


1.4 


1.28 


1.16 


1.05 


0.95 


35 ... . 


2.31 


2.1 


1.89 


1.73 


1.58 


1.44 


1.31 


1.19 


1.09 


0.98 


36 ... . 


2.38 


2.16 


1.95 


1.78 


1.62 


1.48 


1.35 


1.23 


1.12 


1.01 


37 ... . 


2.44 


2.22 


2. 


1.83 


1.67 


1.52 


1.39 


1.26 


1.15 


1.04 


38 ... . 


2.51 


2.28 


2.05 


1.88 


1.71 


1.56 


1.43 


1.29 


1.18 


1.07 


39 ... . 


2.58 


2.34 


2.11 


1.93 


1.76 


1.6 


1.46 


1.33 


1.21 


1.09 


40 ... . 


2.64 


2.4 


2.16 


1.98 


1.8 


1.64 


1.5 


1.36 


1.24 


1.12 


41 . . . . 


2.71 


2.46 


2.22 


2.03 


1.85 


1.68 


1.54 


1.4 


1.27 


1.15 


42 ... . 


2.77 


2.52 


2.27 


2.08 


1.89 


1.72 


1.58 


1.43 


1.3 


1.18 


43 ... . 


2.84 


2.58 


2.32 


2.13 


1.94 


1.76 


1.61 


1.46 


1.33 


1.21 


44 ... . 


2.91 


2.64 


2.38 


2.18 


1.98 


1.81 


1.65 


1.5 


1.37 


1.23 


45 ... . 


2.97 


2.7 


2.43 


2.23 


2.03 


1.85 


1.69 


1.53 


1.4 


1.26 


46 ... . 


3.04 


2.76 


2.49 


2.28 


2.07 


1.89 


1.73 


1.57 


1.43 


1.29 


47 ... . 


3.1 


2.82 


2.54 


2.33 


2.12 


1.93 


1.76 


1.6 


1.46 


1.32 


48 ... . 


3.17 


2.88 


2.59 


2.38 


2.16 


1.97 


1.8 


1.63 


1.49 


1.34 


49 ... . 


3.23 


2.94 


2.65 


2.43 


2.21 


2.01 


1.84 


1.67 


1.52 


1.37 


50 ... . 


3.3 


3. 


2.7 


2.47 


2.25 


2.05 


1.87 


1.7 


1.55 


1.4 


52 ... . 


3.43 


3.12 


2.81 


2.57 


2.34 


2.13 


1.95 


1.77 


1.61 


1.46 



VM 



ELECTROMAGNETS. 



Table IVe. 



■Linear Space occupied bv Double Cotton- 
Covered Wires. — Continued. 



Turns or 






Wire 


numbers, B 


and £ 


>. Gauge. 






Layers. 


15 


16 


17 


18 


19 


20 21 


22 


23 


24 


54 . . . 
56 . . . 

58 . . . 
60 . . . 
62 . . . 

64 . . 
66 . . . 
68 . . . 
70 . . . 
72 . . . 

74. . . . 
76. . . . 
78. . . . 
80. . . . 
82. . . . 

84. . . . 
86. . . . 
88. . . . 
90. . . . 
92. . . . 

94. . . . 

96. . . . 

98. . . . 
100. . . . 
102. . . . 

104. . . . 
106. . . . 
108. . . . 
110. . . . 
112. . . . 

114. . . . 
116. . . . 
118. . . . 
120. . . . 
122. .. . 


3.56 

3.7 

3.83 

3.96 

4.09 

4.23 
4.36 
4.49 
4.62 
4.75 


3.24 

3.36 

3.48 

3.6 

3.72 

3.84 

3.96 

4.08 

4.2 

4.32 


2.92 
3.03 
3.13 
3.24 
3.35 

3.46 
3.57 
3.67 

3.78 
3.89 

4. 

4.11 

4.21 

4.32 

4.43 

4.54 

4.65 
4.75 


2.67 
2.77 

2.87 
2.97 
3.07 

3.17 
3.27 
3 37 
3.47 
3.57 

3.67 
3.76 
3.86 
3.96 
4.06 

4.16 
4.26 
4.36 
4.46 
4.56 

4.66 
4.75 


2.43 

2.52 

2.61 

2.7 

2.79 

2.88 
2.97 
3.06 
3.15 
3.24 

3.33 

3.42 

3.51 

3.6 

3.60 

3.78 
3.87 
3.96 
4.05 
4.14 

4.23 

4.32 

4.41 

4.5 

4.59 

4.68 

.... 


2.22 
2.3 

2.38 
2.46 
2.54 

2.63 

2.71 
2.79 
2.87 
2.95 

3.04 

3.12 

3.2 

3.28 

3.36 

3.45 
3.53 
3.61 
3.69 
3.77 

3.86 

3.94 

4.02 

4.1 

4.18 

4.27 
4.35 
4.43 
4.51 
4.59 


2.03 

2.1 

2.18 

2.25 

2.33 

2.4 

2.48 
2.55 
2.63 

2.7 

2.78 

2.85 

2.93 

3. 

3.08 

3.15 

3.23 

3.3 

3.38 

3.45 

3.53 

3.6 

3.68 

3.75 

3.83 

3.9 

3.98 

4.05 

4.13 

4.2 

4.28 
4.35 
4.43 
4.5 


1.84 

1.9 

1.97 

2.04 

2.11 

2.18 
2.25 
2.31 
2.38 
2.45 

2.52 
2.59 
2.65 
2.72 
2.79 

2.86 
2.93 
2.99 
3.06 
3.13 

3.2 

3.27 

3.33 

3.4 

3.47 

3.54 
3.61 
3.67 
3.74 
3.81 

3.88 
3.95 
4.01 
4.08 
4.15 


1.67 

1.74 

1.8 

1.86 

1.92 

1.99 
2.05 
2.11 
2.17 
2.23 

2.3 

2.36 

2.42 

2.48 
2.54 

2.61 
2.67 
2.73 
2.79 
2.85 

2.92 

2.98 

3.04 

3.1 

3.16 

3.23 
3.29 
3.35 
3.41 
3.47 

3.54 

3.6 

3.66 

3.72 

3.78 


1.51 
1.57 
1.63 
1.68 
1.74 

1.79 
1.85 
1.91 
1.96 
2.02 

2.07 
2.13 
2.19 
2.24 
2.3 

2.35 
2.41 
2.47 
2.52 

2.58 

2.63 
2.69 
2.75 

2.8 
2.86 

2.91 
2.97 
3.03 
3.08 
3.14 

3.19 
3.25 
3.31 
3.36 
3.42 



Note. — Because of the compression of the insulation on wires wound in 
layers, and the tendency of the wires of each layer to "bed" between those 
of the preceding layer, a given number of layers will occupy from 2% to 8% 
less space than the same number of turns side by side, according to the size 
of wire and thickness of the insulation. Most of the difference is due to the 
compression of insulation, the "bedding" effect being almost negligible. 
For wires of medium size with single cotton insulation, an allowance of 4% 
will usually be ample to cover the increase in number of layers within a given 
8 pace. 



WINDING OF ELECTROMAGNETS. 127 

Alternatingr-Current Xleetroinagrnets. 

The cores of electromagnets to be used with alternating currents must 
be laminated, and the laminations must run at right angles to the direc- 
tion in which eddy currents would be set up. Eddy currents tend to cir- 
culate parallel to the coils of the wire, and the laminations must, therefore, 
be longitudinal to or parallel with the axis of the cores. 

The coils of an alternating-current electromagnet offer more resistance 
to the passage of the alternating current than the mere resistance of the 
conductor in ohms. This extra resistance is called inductance, and this 
combined with the resistance of the conductor in ohms produces the quality 
called impedance. (See Index for Impedance, etc.) 

If L = coefficient of self-induction, 
N = cycles per second, 
R = resistance, 
Impedance = V#2 + 4 ir*WL?\ 
and, 

Maximum E.M.F. 



Maximum current = 
Mean current = 



Impedance 
Mean E.M.F. 
Impedance. 



Keating' of Hagn<»t Coil*. 

Professor Forbes. 

I = current permissible. 

r t = resistance of coil at permissible temperature. 
Permissible temperature = cold r X 1.2. 

t = rise in temperature C°. 

s = sq. cms. surface of coil exposed to air. 



/ 



0003 X t X s 



.24 X r x 



law of the Plunder Electromagnet. 

Charles R. Underhill gives the following formula as having been found 
by practise the most accurate and complete for the design of plunger electro- 
magnets. 

Let P = pull in pounds. 

B = flux density in the working air-gap. 
I = length of the air-gap. 
IN = ampere-turns in the winding. 
A = cross section of plunger in sq. in. 

Pe = pull at 10,000 ampere-turns and 1 sq. in. of plunger. 
n = ampere-turn factor. 
L = length of the winding in inches. 

Then, the pull due to an iron-clad solenoid is 

APc {IN - n) 



P = 



10,000 - n 



and, at points along the uniform range of solenoids, the pull for the plunger 
electromagnet will be 

ZAT2 Pc(IN - nU 

',075,600 I 2 "*" 10,000 - n )' 

Here I must include the extra length assumed due to the reluctance outside 
of the working air-gap. 



= A iu 



128 



ELECTROMAGNETS. 



Pull in Pound*, and Ampere-turn factor at Different 
Points along* an ^Electromagnet. 



L 


Pt 


n 


1 

2 

3 

4 - 

5 

6 


33.0 

28.3 

23.4 

19.2 

16.0 

13.8 

12.2 

11.0 

10.0 

9.2 

8.4 

7.8 

7.2 

6.8 

6.4 

6.0 

5.7 

5.3 

5.0 

4.7 


3600 
3150 
2800 
2500 
2200 
1970 


7 

8 

9 

10 

11 

12 - - 

13 

14 

15 

16 

17 

18 . . 

19 

20 


1750 

1580 

1400 

1230 

1100 

960 

840 

725 

625 

525 

430 

350 

270 

210 



To approximate the curve of a plunger electromagnet at points between 
the center of the winding, and the end of the winding where the plunger 
enters, assume that the curve is a straight line for the last .4 of the dis- 
tance; then the pull at any point, la as measured in inches, back from the 
end of the winding, will be 



:dx 



IW 



laPc (IN - n) 



075,600 I 2 ' .4 L (10,000 



n)J 



(8) 



where L equals length of the winding. In this it is assumed that the winding 
is approximately as long as the inside of the frame. 

In cases where a low density in the core is used, the curve for the iron- 
clad solenoid effect cannot be calculated with so high a degree of accuracy. 




/fm7777777Zr77 7777777777//A 




ft//////////////////////////, 

Figs. 2, 3, 4 and 5. Shapes of Electromagnets. 



WINDING OF ELECTROMAGNETS. 



129 



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23456789 10 

POSITIONS INSIDE OF WINDING, (INCHES) 

Fig. 6. Characteristics of Electromagnets. 



130 



ELECTROMAGNETS. 



Fig. 2 shows a simple coil and plunger and Fig. 4 the same magnet, but 
with an iron jacket or return circuit about the outside of the winding. 
This is usually referred to as an iron-clad solenoid. 

By placing a "stop" inside the winding at the rear end of the frame 
we have the plunger electromagnet in Fig. 3. 

It is to be observed that the same coil and the same plunger are used in 
each case. The cross section, A, of the plunger is just 1 square inch. 

Referring to Fig. 6, curve " a" is due to the simple coil and plunger in 
Fig. 2, and curve " b " is due to the iron-clad solenoid in Fig. 4, the ampere- 
turns in the winding being 10,000 in all cases. It will be noticed that the 
only difference between curves "a" and " 6" is that curve " 5" is slightly 
higher at distances greater than 6 in., owing to the confinement of the 
field, and also that it bends upward for short distances instead of falling 
off like curve " a." This latter effect is due to the attraction between 
the end of the plunger and the iron frame of the iron-clad solenoid. How- 
ever, the pull throughout the center of the winding is the same in both 
cases. 

Where there is a high density of the lines of force in the plunger, an 
additional reluctance is in evidence, which 
must be added to the length of the work- 
ing air-gap. 

The range of a solenoid is the distance 
through which its plunger will perform 
work when the winding is energized. 
The greater the length of the solenoid, 
the greater will be the range, as the range 
varies in nearly direct proportion with 
the length of the solenoid. The range of 
the solenoid is nearly constant regardless 
of the ampere-turns, but the attraction 
or pull on the plunger varies directly with 
the ampere-turns after the core is satur- 
ated, there being some variation below 
this point due to change in the perme- 
ability of the plunger. 

In designing a solenoid, the pull should Fig. 7. Pull due to Solenoids oi 
be taken at a point on the eurve which Different Lengths with Plunger 
is considerably below the maximum, as 1 sq. in. in Cross-Section, 
this will allow for enough extra attraction 

to overcome any friction, and also to keep the load moving, and by 
assuming a low point for the necessary pull, the effective range will be 
greatly increased. 




AMPERE-TURNS 



PROPERTIES OP WIRES AND CABLES. 

Revised by Harold Pender, Ph.D. 

Units of Resistance. 

The unit of resistance now universally used is the International Ohm. 
The following multiples of this unit are sometimes employed. 

Megohm = 1,000,000 ohms. 
Microhm = 0.000,001 ohm. 

The following table gives the value of the principal practical units of resis- 
tance which existed previous to the establishment of the International Units. 



i 



Unit. 


International 
Ohm. 


B.A. 

Ohm. 


Legal Ohm 

1884. 


Siemens's 
Ohm. 


International ohm. . 

B. A. ohm 

Legal ohm 

Siemens's ohm . . . 


1. 

0.9866 
0.9972 
0.9407 


1 .0136 
1. 

1.0107 
0.9535 


1.0028 
0.9894 
1. 
0.9434 


1.0630 
1.0488 
1.0600 
1. 



Thus to reduce British Association ohms to international ohms we divide 
by 1.0136, or multiply by 0.9866; and to reduce legal ohms to international 
ohms we divide by 1.0028, or multiply by 0.9972, etc. 

Specific Resistance. 

Let I = length of the conductor. 

A = cross section of the conductor. 
R = resistance of the conductor. 
p = specific resistance of the conductor. 

Then R = pi 

A 

T> A 

If I is measured in centimeters and A in square centimeters, p is the 
resistance of a centimeter cube of the conductor. If I is measured in 
inches and A in square inches, p is the resistance of an inch cube of the 
conductor. 

In telegraph and telephone practice, specific resistance is sometimes 
expressed as the weight per mile-ohm, which is the weight in pounds of a 
conductor one mile long having a resistance of one ohm. 

Another common way of expressing specific resistance is in terms of 
ohms per mil-foot, i.e., the resistance of a round wire one foot long and 
0.001 inch in diameter ; I is then measured in feet and A in circular mils. 

Microhms per inch cube = 0.3937 X microhms per centimeter cube. 

Pounds per mile-ohm = 57.07 X microhms per centimeter cube X 

specific gravity. 

Ohms per mil-foot == 6.015 X microhms per centimeter cube. 

131 



132 



PROPERTIES OF CONDUCTORS. 



Specific Conductivity is the reciprocal of specific resistance. If c = 
specific conductivity 

cA 

= J_ 

C RA' 

1 

c = -■ 
P 

By Relative or Percent ag-e Conductivity of a sample is meant 
100 times the ratio of the conductivity of the sample at standard tem- 
perature to the conductivity of a conductor of the same dimensions made 
of the standard material and at standard temperature. If p is the specific 
resistance of the sample at standard temperature and pa is the specific resist- 
ance of the standard at standard temperature, then 

Percentage conductivity = 100 — • 

Po 
In comparing different materials, the specific resistance should always 
be determined at the standard temperature, which is usually taken as 0° 
Centigrade. If it is inconvenient to measure the resistance of the sample 
at the standard temperature, this may be readily calculated if the tem- 
perature coefficient a of the sample is known, i.e., 

P ° = T+Vt 
where p t is the specific resistance at temperature t. 

MT atthiessen's Standard of Conductivity, which is the commercial 
standard, is a copper wire having the following properties at the standard 
temperature of 0° C. 

Specific gravity 8.89. 

Length 1 meter. 

Weight 1 gram. 

Resistance .141729 ohms. 

Specific Resistance 1.594 microhms per cubic centimeter. 

Relative Conductivity 100%. 

Specific Resistance, Relative Resistance, and Relative 
Conductivity of Conductors. 

Referred to Matthiessen's Standard. 





Resistance in Microhms 








at C 


' C. 


Relative 


Relative 


Metals: 






Resis- 


Conduc- 


Centimeter 
Cube. 


Inch Cube. 


tance. 
% 


tivity. 
% 


Silver, annealed . . . 


1.47 


.579 


92.5 


108.2 


Copper 


1.55 


.610 


97.5 


102.6 


Copper (Matthiessen's 


1.594 


.6276 


100 


100.0 


Standard). 










Gold (99.9% pure) . 


2.20 


.865 


138 


72.5 


Aluminum (99% pure) 


2.56 


1.01 


161 


62.1 


Zinc 


5.75 


2.26 


362 


27.6 


Platinum, annealed . . 


8.98 


3.53 


565 


17.7 


Iron 


9.07 


3.57 


570 


17.6 


Nickel 


12.3 


4.85 


778 


12.9 


Tin 


13.1 


5.16 


828 


12.1 


Lead 


20.4 


8.04 


1,280 


7.82 


Antimony 


35.2 


13.9 


2,210 


4.53 


Mercury 


94.3 


37.1 


5,930 


1.69 


Bismuth 


130. 


51.2 


8,220 


1.22 


Carbon (graphitic) . . 


2,400-42,000 


950-16,700 






Carbon (arc light) . . 


about 4,000 


about 1,590 






Selenium 


6X10 10 


2.38 X10 10 







GENERAL. 



133 



Liquids at 18° C. 


Ohms per Centi- 
meter Cube. 


Ohms per Inch 
Cube. 


Pure water 


2650 
30 
4.86 
1.37 
9.18 
1.29 
21.4 


1050 


Sea water 


11 8 


Sulphuric acid, 5% 

Sulphuric acid, 30% 

Sulphuric acid, 80% 

Nitric acid, 30% 

Zinc sulphate, 24% 


1.93 
.544 

3.64 
.512 

8.54 



Temperature Coefficient. 

The resistance of a conductor varies with the temperature of the con- 
ductor. 

Let R = Resistance at 0° 



Then 



R = Resistance at t°. 
R = Ro(l +'at). 



a is called the temperature coefficient of the conductor. 100 a is the per- 
centage change in resistance per degree change in temperature. 

The following values of the temperature coefficient have been found for 
temperatures measured in degrees Centigrade and in degrees Fahrenheit. 
It is to be noted that the coefficients vary considerably with the purity of 
the conductor. 



Pure Metals. 



Silver, annealed . , 
Copper, annealed 
Gold (99.9%) . . , 
Aluminium (99%) . 

Zinc 

Platinum, annealed 

Iron , 

Nickel 

Tin 

Lead 

Antimony . . . 
Mercury .... 
Bismuth .... 



Centigrade 
a 


Fahrenheit 
a 


0.00400 


0.00222 


0.00428 


0.00242 


0.00377 


0.00210 


0.00423 


0.00235 


0.00406 


0.00226 


0.00247 


0.00137 


0.00625 


0.00347 


0.0062 


0.00345 


0.00440 


0.00245 


0.00411 


0.00228 


0.00389 


0.00216 


0.00072 


0.00044 


0.00354 


0.00197 



Matthiessen's formula for soft copper wire 

R = R (l + .00387* + .00000597* 2 ). 

The wire used by Matthiessen was as pure as could be obtained at the 
time (1860), but in reality contained considerable impurities; the above 
formula, therefore, is not generally applicable. Later experiments have 
shown that for all practical work the above equation for copper wire may 
be written 

R = R (1 + .0042*) for t in ° C. 



134 



PROPERTIES OF CONDUCTOKS. 






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PHYSICAL AND ELECTRICAL PROPERTIES OF METALS. 135 



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136 



PROPERTIES OF CONDUCTORS. 



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PHYSICAL AND ELECTRICAL PROPERTIES OF METALS. 137 



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138 



PROPERTIES OF CONDUCTORS. 



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PHYSICAL AND ELECTRICAL PROPERTIES OF METALS. 139 



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140 



PROPERTIES OF CONDUCTORS. 






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WIRE GAUGES. 



141 



WIRE CtAUGJGS. 

The sizes of wires are ordinarily expressed by an arbitrary series of num- 
bers. Unfortunately there are several independent numbering methods, 
so that it is always necessary to specify the method or wire gauge used. 
The following table gives the numbers and diameters in decimal parts of an 
inch for the various wire gauges used in this country and England. 

In Decimal Parts of an Inch. 



Number 

of 

Wire 

Gauge. 


Roebling or 

Washburn 

. & Moens. 


Brown & 
Sharpe. 


Birming- 
ham, or 
Stubs. 


English 
Legal Stand- 
ard. 


Old English, 
or London. 


6-0 


.460 






.464 




5-0 


.430 






.432 




4-0 


.393 


!4600' 


.454 


.400 


.4540' 


3-0 


.362 


.4096 


.425 


.372 


.4250 


2-0 


.331 


.3648 


.380 


.348 


.3800 





.307 


.3249 


.340 


.324 


.3400 


1 


.283 


.2893 


.300 


.300 


.3000 


2 


.263 


.2576 


.284 


.276 


.2840 


3 


.244 


.2294 


.259 


.252 


.2590 


4 


.225 


.2043 


.238 


.232 


.2380 


5 


.207 


.1819 


.220 


.212 


.2200 


6 


.192 


.1620 


.203 


.192 


.2030 


7 


.177 


.1443 


.180 


.176 


.1800 


8 


.162 


.1285 


.165 


.160 


.1650 


9 


.148 


.1144 


.148 


.144 


.1480 


10 


.135 


.1019 


.134 


.128 


.1340 


11 


.120 


.09074 


.120 


.116 


.1200 


12 


.105 


.08081 


.109 


.104 


.1090 


13 


.092 


.07196 


.095 


.092 


.0950 


14 


.080 


.06408 


.083 


.080 


.0830 


15 


.072 


.05706 


.072 


.072 


.0720 


16 


.063 


.05082 


.065 


.064 


.0650 


17 


.054 


.04525 


.058 


.056 


.0580 


18 


.047 


.04030 


.049 


.048 


.0490 


19 


.041 


.03589 


.042 


.040 


.0400 


20 


.035 


.03196 


.035 


.036 


.0350 


21 


.032 


.02846 


.032 


.032 


.0315 


22 


.028 


.02534 . 


.028 


.028 


.0295 


23 


.025 


.02257 


.025 


.024 


.0270 


24 


.023 


.02010 


.022 


.022 


.0250 


25 


.020 


.01790 


.020 


.020 


.0230 


26 


.018 


.01594 


.018 


.018 


.0205 


27 


.017 


.01419 


.016 


.0164 


.01875 


28 


.016 


.01264 


.014 


.0148 


.01650 


29 


.015 


.01125 


.013 


.0136 


.01550 


30 


.014 


.01002 


.012 


.0124 


.01375 


31 


.0135 


.00893 


.010 


.0116 


.01225 


32 


.0130 


.00795 


.009 


.0108 


.01125 


33 


.0110 


.00708 


.008 


.0100 


.01025 


34 


.0100 


.00630 


.007 


.0092 


.0095 


35 


.0095 


.00561 


.005 


.0084 


.0090 


36 


.0090 


.00500 


.004 


.0076 


.0075 


37 


.0085 


.00445 




.0068 


.0065 


38 


.0080 


.00397 




.0060 


.0057 


39 


.0075 


.00353 




.0052 


.0050 


40 


.0070 


.00314 




.0048 


.0045 



142 PROPERTIES OP CONDUCTORS. 

Roehling* Gaugre. — Used almost universally in this country for iron 
and steel wire. 

Brown & Sharpe Gaug-e. — The American standard for wires for 
electrical purposes. 

Birmingham Gauge. — Used largely in England and also in this 
country for wires other than those made especially for electrical purposes, 
excepting iron wire. 

law of the Brown & Sharpe Gauge. 

The diameters of wires on the B. and S. gauge are obtained from the 
geometric series in which No. 0000 = 0.4600 inch and No. 36 = .005 in., 
the nearest fourth significant figure being retained in the areas and diameters 
so deduced. 

Let n = gauge number (0000 = - 3; 000 = - 2; 00 = - 1). 

d = diameter of wire in inches. 
_ . 0.3249 

ThCD d = OS* ' 



WIRE STRANDS. 

Wires larger than No. 0000 B. and S. are seldom made solid but are 
built up of a number of small wires into a strand. The group of wires is 
called a *' strand;" the term "wire" being reserved for the individual wires 
of the strand. Strands are usually built up of wires of such a size that the 
cross section of the metal in the strand is the same as the cross section of a 
solid wire having the same gauge number. 

If n = number of concentric layers around one central strand, 

., 3 (n 2 + n) + 1 - metal area 

then — — , ,._ = ratio of rr-r-. • 

(2 n -f- 1) 2 available area 

The number of wires that will strand will be3n (n-f-l)H-l. 



Number of Strands. 


metal area 
available area 


1 
7 
19 
37 
61 
91 


1.000 
.778 
.760 
.755 
.753 
.752 



Sheathing* Core. — ■ The number, N, of sheathing wires having a diam- 
eter, d, which will cover a core having a diameter, D, is 



COPPER WIRE TABLES 



143 



COPPER HIKE, 

Physical Constants of Commercial Wire. — Average 
Values. 



Annealed. 



Hard. 



Per Cent Conductivity (Matthiessen's Standard 100) 

Specific Gravity 

Pounds in 1 cubic foot 

Pounds in 1 cubic inch 



Pounds per mile per circular mil 

lbs. 
Ultimate Strength 



sq. in. 

Modulus of Elasticity '— — r-f — . . 

in. X sq. in. 

Coefficient of Linear Expansion per ° C. 



Coefficient of Linear Expansion per ° F 

Melting Point in ° C 

Melting Point in ° F 

Specific Heat (watt-seconds to heat 1 lb. 1° C.) . . 

Thermal Conductivity (watts through cu. in., tem- 
perature gradient 1° C.) 



Resistance: 

Microhms per centimeter cube 0° C. 

Microhms per inch cube 0° C. . . . 

Ohms per mil-foot 0° C 

Ohms per mil-foot 20° C 

Resistance per mile 0° C 

Resistance per mile 20° C 

Pounds per mile ohm 0° C 

Pounds per mile ohm 20° C 

Temperature Coefficient per ° C. . . . 
Temperature Coefficient per ° F. . . . 



100 

8.9 

555 

.321 

.0160 

23,000 

.0000171 

.0000095 

1050 

1920 

176 

8.7 



98 

8.94 

558 

.323 

.0161 

55,000 

16,000,000 

.0000171 

.0000095 

1050 

1920 

176 

8.7 



1.594 


1.626 


.6276 


.6401 


9.59 


9.78 


10.36 


10.57 


50,600 


51,600 


cir. mils. 


cir. mils. 


54,600 


55,700 


cir. mils. 


cir. mils. 


810 


830 


875 


896 


.0042 


.0042 


.00233 


.00233 



144 



PROPERTIES OF CONDUCTORS. 



Table showing* the Effect of Admixture of Copper with 
Specific Quantities of Various Substances. 

Matthiessen. 



Substances alloyed with Pure Copper. 


Conducting 
Power of 
Hard-drawn 
Alloy, Pure 
Soft Copper 
being 100. 


Temperature 

Centigrade. 

Degrees. 


Carbon: 






Copper with .05 per cent of carbon . . 


77.87 


18.3 


Sulphur: 






Copper, with . 18 per cent of sulphur . . 


92.08 


19.4 


Phosphorus: 






Copper, with . 13 per cent of phosphorus . 


70.34 


20.0 


Copper, with .95 per cent of phosphorus . 


24.16 


22.1 


Copper, with 2.5 per cent of phosphorus . 


7.52 


17.5 


Arsenic: 






Copper, with traces of arsenic 


60.08 


19.7 


Copper, with 2.8 per cent of arsenic . . . 


13.66 


19.3 


Copper, with 5 . 4 per cent of arsenic . . . 


6.42 


16.8 


Zinc: 






Copper, with traces of zinc 


88.41 


19.0 


Copper, with 1.6 per cent of zinc .... 


79.37 


16.8 


Copper, with 3.2 per cent of zinc .... 


59.23 


10.3 


Iron: 






Copper, with .48 per cent of iron .... 


35.92 


11.2 


Copper, with 1.06 per cent of iron. . . . 


28.01 


13.1 


Tin: 






Copper, with 1 . 33 per cent of tin .... 


50.44 


16.8 


Copper, with 2.52 per cent of tin .... 


33.93 


17.1 


Copper, with 4.9 per cent of tin 


20.24 


14.4 


Silver: 






Copper, with 1 . 22 per cent of silver . . . 


90.34 


20.7 


Copper, with 2.45 per cent of silver . . . 


82.52 


19.7 


Gold: 






Copper, with 3.5 per cent of gold .... 


67.94 


18.1 


Aluminum: 






Copper, with 10 per cent of aluminum. . . 


12.68 


14.0 



COPPER WIRE TABLES. 145 



COPPEB WIRE TABLES. 

Below are given the Copper Wire Tables of the American Institute of 
Electrical Engineers. The table for the Brown and Sharpe gauge is derived 
from the following formulae: 

Let n = wire gauge number. 

d = diameter of wire in inches. 
CM. = area in circular mils. 

r = resistance in ohms per 1000 feet at 20° C. 
o) = weight in pounds per 1000 feet. 
0.3249 



Then d = 

CM. = 



1.123" 

105,500 
1.261" 



r - 0.09811 X 1.261" 
319.5 

A useful approximate formula for resistance per 1000 feet at about 20° C. 
is r = 0.1 X 25. (& = 1.26; 2* = 1.59). 

From this it is seen that an increase of 3 in the wire number corresponds 
to doubling the resistance and halving the cross section and weight. Also, 
that an increase of 10 in the wire number increases the resistance 10 times 
and diminishes the cross section and weight to x&th their original values. 

The data in the following table has been computed as follows : Mat- 
thiessen's standard resistivity, Matthiessen's temperature coefficient, specific 
gravity of copper =8.89. Resistance in terms of the international ohm. 

Matthiessen's standard 1 meter gramme of hard drawn copper = 0.1469 
B.A.U. @ 0° C. Ratio of resistivity hard to soft copper 1.0226. 

Matthiessen's standard 1 meter gramme of soft drawn copper =0.14365 
B.A.U. @ 0° C. One B.A.U. = 0.9866 international ohm. 

Matthiessen's standard 1 meter gramme of soft drawn copper = 0.141729 
international ohm at 0° C. 

Temperature coefficients of resistance ior 20° C, 50° C, and 80° C, 1.07968, 
1.20625 and 1.33681 respectively. 1 foot = 0.3048028 meter, 1 pound = 453.59256 
grammes. 

Although the entries in tho table are carried to the fourth significant 
digit, the computations have been carried to at least five figures. The last 
digit is therefore correct to within half a unit, representing an arithmetical 
degree of accuracy of at least one part in two thousand. The diameters of 
the B. & S. or A. W. G. wires are obtained from the geometrical series in 
which No. 0000 = 0.4600 inch and No. 36 = 0.005 inch, the nearest fourth sig- 
nificant digit being retained in the areas and diameters so reduced. 

It is to be observed that while Matthiessen's standard of resistivity may 
be permanently recognized, the temperature coefficient of its variation 
which he introduced, and which is here used, may in future undergo slight 
revision. 



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154 



PROPERTIES OF CONDUCTORS. 



The following condensed copper wire tables for both solid and stranded 
conductors are more convenient for ordinary calculations. 

Solid Copper Wire-100% JtEatthiessen'rt Standard. 





Diam. 

Mils. 




Weight. Pounds. 


Resistance, 20° C. 
68° F. 


No. 
B.&S. 




Area. 
Cir. Mils. 






Feet 








Bare. 




1000'. 


Mile. 


per 
Pound. 


1000'. 


Mile. 


oooo 

000 

00 




460 
409.6 
364.8 
324.9 


211,600 
167,800 
133,100 
105,500 


640.5 
508 
402.8 
319.5 


3,381 

2,682 
2,127 
1,687 


1.561 
1.969 

2.482 
3.130 


.04893 
.06170 
.07780 
.09811 


.2583 
.3258 
.4108 
.5180 


1 


289.3 


83,690 


253.3 


1,337 


3.947 


.12370 


.6531 


2 
3 

4 


257.6 
229.4 
204.3 


66,370 
52,630 
41,740 


200.9 
159.3 
126.4 


1,062 
841.1 
667.4 


4.977 
6.276 
7.914 


.1560 
.1967 
.2480 


.8237 
1.0386 
1.3094 


5 
g 


181.9 
162.0 


33,100 
26,250 


100.2 
79.46 


529.0 
419.5 


9.980 
12.580 


.3128 
.3944 


1.6516 

2.0824 


7 


144.3 


20,820 


63.02 


332.7 


15.87 


.4973 


2.6257 


8 


128.5 


16,510 


49.98 


263.9 


20.01 


.6271 


3.3111 


9 


114.4 


13,090 


39.63 


209.2 


25.23 


.7908 


4.1754 


10 


101.9 


10,380 


31 .43 


166.0 


31.82 


.9972 


5 . 2652 


11 


90.74 


8,234 


24.93 


131.6 


40.12 


1.257 


6.6370 


12 


80.81 


6,530 


19.77 


104.4 


50.59 


1.586 


8.374 


13 


71.96 


5,178 


15.68 


82.79 


63.79 


2.000 


10.560 


14 


64.08 


4,107 


12.43 


65.63 


SO. 44 


2.521 


13.311 


15 


57.07 


3,257 


9.858 


52.05 


101.4 


3.179 


16.785 


16 


50.82 


2,583 


7.818 


41.28 


127.9 


4.009 


21 . 168 


17 


45.26 


2.04S 


6.200 


32.74 


161.3 


5.055 


26.690 


18 
19 


40.30 

35.89 


1,624 
1,28$ 


4.917 
3.899 


25.96 
20.59 


203.4 
256.5 


6.374 
8.038 


33.655 
42.440 


20 


31.96 


1,022 


5 3.092 


16.33 


323.4 


10.14 


53,540 



T>. 



7« fe 



Or 






. 



STRANDED COPPER WIRE. 



155 



Atranded Copper Wire — 100% JUattliiessen's Standard. 



No. 
B.&S. 


Diam. 

Mils. 


Area 
Cir. Mils, 


Weight Pounds. 


Resistance 20° C. 
68° F. 


Bare. 


1,000'. 


Per 

Mile. 


Feet 
per lb. 


1,000'. 


Mile. 




1,152 
1,125 


2,000,000 
1,500,000 
1,250,000 
1,000,000 
950,000 


6,100 
4,575 
3,813 
3,050 

2,898 


32,208 

24,156 
20,132 
16,104 
15,299 


.164 

.219 
.262 
.328 
.345 


.005177 
.006902 
.008282 
.010353 
.010900 


.02733 
.03644 
.04373 
.05466 
.05755 




1,092 

1,062 

1,035 

999 


900,000 
850,000 
800,000 
750,000 


2,745 
2,593 
2,440 

2,288 


14,494 

13,688 
12,883 
12,078 


.364 
.385 
.409 
.437 


.01150 
.01218 
.01294 
.01380 


.06072 
.06431 
.06832 
.07286 




963 
927 
891 
855 


700,000 
650,000 
600,000 
550,000 


2,135 
1,983 
1,830 
1,678 


11,273 

10,468 

9,662 

8,857 


.468 
.504 
.546 
.596 


.01479 
.01593 
.01725 
.01882 


.07809 
.08411 
.09108 
.09937 




819 
770 

728 
679 


500,000 
450,000 
400,000 
350,000 


1,525 
1,373 
1,220 
1,068 


8,052 
7,247 
6,442 
5,636 


.655 

.728 
.819 
.936 


.02070 
.02300 
.02588 
.02958 


. 10930 
.12144 
. 13664 
.15618 


oooo 

000 


630 
590 
530 
470 


300,000 
250,000 
211,600 
167,800 


915 

762 
645 
513 


4,831 
4,026 
3,405 
2,709 


1.093 
1.312 
1.550 
1.949 


.03451 
.04141 
.04893 
.06170 


.18221 
.21864 
.2583 
.3258 


00 


1 

2 


420 
375 
330 
291 


133,100 

105,500 

83,690 

66,370 


406 
322 
255 
203 


2,144 
1,700 
1,347 
1,072 


2.463 
3.106 
3.941 
4.926 


.07780 
.09811 
.12370 
. 15600 


.4108 
.5180 
.6531 

.8237 


3 

4 


261 
231 


52,630 
41,740 


160 
127 


845 
671 


6.250 

7.874 


.19670 
.2480 


1.0386 
1.3094 



This table is calculated for untwisted strands; if the strand is twisted the 
cross section of the copper at right angles to the length of the strand, the 
weight per unit length and the resistance per unit length will each increase 
from 1 to 3 per cent, and the length per unit weight will decrease from 1 to 3 
per cent, depending on the number of twists per unit length and the number 
of wires in the strand. 



156 



PROPERTIES OF CONDUCTORS. 



Tensile Streng-th of Copper Wire. 

ROEBLING. 



Numbers, 
B.&S. 
Gauge. 


Breaking Weight, Lbs. 


Numbers, 
B.&S. 
Gauge. 


Breaking Weight, Lbs. 


Hard- 
drawn. 


Annealed. 


Hard- 
drawn. 


Annealed. 


0000 

000 

00 



1 
2 
3 

4 

5 
6 

7 
8 


8,310 
6,580 
5,226 
4,558 

3,746 
3,127 
2,480 
1,967 

1,559 

1,237 

980 

778 


5,650 
4,480 
3,553 

2,818 

2,234 
1,772 
1,405 
1,114 

883 
700 
555 
440 


9 
10 
11 
12 

13 
14 
15 
16 

17 
18 
19 
20 


617 
489 
388 
307 

244 
193 
153 
133 

97 

77 
61 
48 


349 
277 
219 
174 

138 

109 

87 

69 

55 
43 
34 
27 



The strength of soft copper wire varies from 32,000 to 36,000 pounds per 
square inch, and of hard copper wire from 45,000 to 68,000 pounds per 
square inch, according to the degree of hardness. 

The above table is calculated for 34,000 pounds for soft wire and 60,000 
pounds for hard wire, except for some of the larger sizes, where the breaking 
weight per square inch is taken at 50,000 pounds for 0000, 000, and 00, 
55,000 for 0, and 57,000 pounds for 1. 



Hard-Drawn Copper Telegraph Wire. 

ROEBLING. 



Size 


Resistance 


Breaking 


Weight 


Furnished 
in Coils 

as follows, 
Miles. 


Approx. Size 


B.&S. 


in Ohms 


Strength, 


per 


E.B.B. Iron Wire 


Gauge. 


per Mile. 


Pounds. 


Mile. 


Equal to Copper. 


9 


4.30 


625 


209 


1 


2 . 


JO 


5.40 


525 


166 


1.2 


3 




11 


6.90 


420 


131 


.52 


4 




12 


8.70 


330 


104 


.65 


6 


Iron-Wire 


13 


10.90 


270 


83 


1.20 


6* 


Gauge. 


14 


13.70 


213 


66 


1.5U 


8 




15 


17.40 


170 


52 


2.00 


9 




16 


22.10 


130 


41 


1.20 


10 





In handling this wire the greatest care should be observed to avoid kinks, 
bends, scratches, or cuts. Joints should be made only with Mclntire Con- 
nectors. 

On account of its conductivity being about five times that of Ex. B. B. 
Iron Wire, and its breaking strength over three times its weight per mile, 
copper may be used of which the section is smaller and the weight less than 
an equivalent iron wire, allowing a greater number of wires to be strung on 
the poles. 

Besides this advantage, the reduction of section materially decreases the 
electrostatic capacity, while its non-magnetic character lessens the seV-induc- 
tion of the line, both of which features tend to increase the possible speed of 
signalling in telegraphing, and to give greater clearness of enunciation over 
telephone lines, especially those of great length. 



WEIGHT OF COPPER WIRES. 



157 



Weig-lit of Copper Wire. 

English System, per 1,000 Feet and per Mile, in Pounds. 



English Legal 
Standard. 


Birmingham. 


Brown & Sharpe. 






Weight. 




Weight. 


Eh 

Si 


Weight. 


1 


1000 
Feet. 


Mile. 


1000 
Feet. 


Mile. 


1000 
Feet. 


Mile. 


6-0 


464 
432 
400 


652 
565 

484 


3,441 
2,983 
2,557 














5-0 














4-0 


454 


624" 


3,294" 


460 " 


64i' ' 


3,382"" 


3-0 


372 


419 


2,212 


425 


547 


2,887 


410 


509 


2,687 


2-0 


348 


367 


1,935 


380 


437 


2,308 


365 


403 


2,129 





324 


318 


1,678 


340 


350 


1,847 


325 


320 


1,688 


1 


300 


272 


1,438 


300 


272 


1,438 


289 


253 


1,335 


2 


276 . 


231 


1,217 


284 


244 


1,289 


258 


202 


1,064 


3 


252 


192 


1,015 


259 


203 


1,072 


229 


159 


838 


4 


233 


163 


860 


238 


171 


905 


204 


126 


665 


5 


212 


136 


718 


220 


146 


773 


182 


100 


529 


6 


192 


112 


589 


203 


125 


659 


162 


79 


419 


7 


176 


94 


495 


180 


98 


518 


144 


63 


331 


8 


160 


77 


409 


165 


82 


435 


128 


50 


262 


9 


144 


63 


331 


148 


66 


350 


114 


39 


208 


10 


128 


50 


262 


134 


54 


287 


102 


32 


166 


LI 


116 


41 


215 


120 


44 


230 


91 


25 


132 


12 


104 


33 


173 


109 


36 


190 


81 


20 


105 


13 


92 


25.6 


135 


95 


27.3 


144 


72 






14 


80 


19.4 


102 


83 


20.8 


110 


64 


12.4 


65 


15 


72 


15.7 


83 


72 


15.7 


83 


57 


9.8 


52 


16 


64 


12.4 


65 


65 


12.8 


68 


51 


7.9 


42 


17 


56 


9.5 


50 


58 


10.2 


54 


45 


6.1 


32 


18 


48 


7.0 


36.8 


49 


7.3 


38.4 


40 


4.8 


25.6 


19 


40 


4.8 


25.6 


42 


5.3 


28.2 


36 


3.9 


20.7 


20 


36 


3.9 


20.7 


35 


3.7 


19.6 


32 


3.1 


16.4 


21 


32 


3.1 


16.4 


32 


3.1 


16.4 


28.5 


2.5 


13.0 


22 


28 


2.4 


12.5 


28 


2.4 


12.5 


25.3 


1.9 


10.2 


23 


24 


1.7 


9.2 


25 


1.9 


10.0 


22.6 


1.5 


8.2 


24 


22 


1.5 


7.7 


22 


1.5 


7.7 


20.1 


1.2 


6.5 


25 


20 


1.2 


6.4 


20 


1.2 


6.4 


17.9 


.97 


5.1 


26 


18 


.98 


5.2 


18 


.98 


5.2 


15.9 


.77 


4.0 


27 


16.4 


.81 


4.3 


16 


.77 


4.1 


14.2 


.61 


3.2 


28 


14.8 


.66 


3.5 


14 


.59 


3.1 


12.6 


.48 


2.5 


29 


13.6 


.56 


3.0 


13 


.51 


2.7 


11.3 


.39 


2.0 


30 


12.4 


.47 


2.5 


12 


.44 


2.3 


10.0 


.30 


1.6 


31 


11.6 


.41 


2.15 


10 


.30 


1.6 


8.9 


.24 


1.27 


32 


10.8 


.35 


1.86 


9 


.25 


1.3 


8.0 


.19 


1.02 


33 


10.0 


.30 


1.60 


8 


.19 


1.02 


7.1 


.15 


.81 


34 


9.2 


.26 


1.35 


7 


.15 


.78 


6.3 


.12 


.63 


35 


8.4 


.21 


1.13 


5 


.075 


.40 


5.6 


.095 


.50 


36 


7.6 


.17 


.92 


4 


.048 


.256 


5.0 


.076 


.40 



The diameters given for the various sizes are those to which the wire is 
actually drawn. 



158 



PROPERTIES OF CONDUCTORS. 



Weight of Copper Wire. 

Metric System — Per Kilometer, in Kilograms. 



Number 
of Wire 
Gauge. 


Roebling. 


Brown & 
Sharpe. 


Birmingham 
or Stubs. 


English 

Legal 

Standard- 


6-0 


954.3 






970.9 


5-0 


833.9 






841.6 


4-0 


696.5 


954! 3 


929 !i 


721.5 


3-0 


591.0 


756.8 


814.5 


624.0 


2-0 


494.1 


600.2 


651.3 


546.2 





425.1 


480.4 


521.3 


473.4 


1 


361.2 


377.4 


405.8 


405.8 


2 


311.9 


299.3 


363.3 


343.5 


3 


268.5 


237.4 


302.6 


286.3 


4 


228.3 


188.3 


255.3 


242.7 


5 


193.2 


149.3 


218.3 


202.7 


6 


166.2 


118.4 


185.9 


166.2 


7 


141.3 


93.9 


146.1 


139.7 


8 


118.3 


74.5 


122.8 


115.4 


9 


98.8 


59.0 


98.8 


93.5 


10 


82.2 


46.8 


81.0 


73.9 


11 


64.9 


37.1 


64.9 


60.7 


12 


49.9 


29.5 


53.6 


48.8 


13 


38.2 


23.4 


39.8 


38.2 


14 


28.9 


18.5 


31.1 


28.9 


15 


23.4 


14.7 


23.4 
19.1 


23.4 


16 


17.9 


11.7 


18.5 


17 


13.2 


9.23 


15.2 


14.1 


18 


9.96 


7.32 


10.8 


10.4 


19 


7.58 


5.80 


7.95 


7.22 


20 


5.52 


4.61 


5.52 


5.85 


21 


4.61 


3.65 


4.62 


4.61 


22 


3.54 


2.89 


3.54 


3.54 


23 


2.81 


2.16 


2.81 


2.59 


24 


2.38 


1.82 


2.19 


2.19 


25 


1.80 


1.44 


1.80 


1.80 


26 


1.46 


1.15 


1.46 


1.46 


27 


1.30 


.908 


1.16 


1.21 


28 


1.15 


.720 


.884 


.988 


29 


1.02 


.572 


.762 


.833 


30 


.884 


.452 


.649 


.694 


31 


.822 


.359 


.451 


.607 


32 


.762 


.284 


.365 


.525 


33 


.544 


.226 


.289 


.451 


34 


.451 


.179 


.220 


.381 


35 


.406 


.141 


.113 


.319 


36 


.365 


.113 


.071 


.260 



STANDARD COPPER STRANDS. 



159 



Standard Copper Strands. 

ROEBLING. 



CM. 


Wires. 


Outside 
Diam. 


Weight 
lbs. per 
1000 ft. 


No. 


Size. 


2,000,000 
1,950,000 
1,900,000 


127 
127 
127 


.1255 
.1239 
.1223 


1.632 
1.611 
1.590 


6100 
5948 
5795 


1,850,000 
1,800,000 
1,750,000 


127 
127 
127 


.1207 
.1191 
.1174 


1.569 
1.548 
1.526 


5643 
5490 
5338 


1,700,000 
1,650,000 
1,600,000 


91 
91 
91 


.1367 
.1347 
.1326 


1.504 
1.482 
1.459 


5185 
5033 
4880 


1,550,000 
1,500,000 
1,450,000 


91 
91 
91 


.1305 
.1284 
.1262 


1.436 
1.412 
1.388 


4728 
4575 
4423 


1,400,000 
1,350,000 
1,300,000 


91 
91 
91 


.1240 
.1218 
.1195 


1.364 
1.340 
1.315 


4270 
4118 
3965 


1,250,000 
1,200,000 
1,150,000 


91 
61 
61 


.1172 
.1403 
.1373 


1.289 
1.263 
1.236 


3813 
3660 
3508 


1,100,000 
1,050,000 
1,000,000 


61 
61 
61 


.1343 
.1312 
.1280 


1.209 
1.181 
1.152 


3355 
3203 
3050 


950,000 
900,000 
850,000 


61 
61 
61 


.1247 
.1214 
.1180 


1.122 
1.093 
1.062 


2898 
2745 
2593 


800,000 
750,000 
700,000 


61 
61 
61 


.1145 
.1108 
.1071 


• 1.031 
.997 
.964 


2440 
2288 
2135 


650,000 
600,000 
550,000 


61 
61 
61 


.1032 
.0991 
.0949 


.929 
.892 
.854 


1983 
1830 
1678 


500,000 
450,000 
400,000 


61 
37 
37 


.0905 
.1103 
.1039 


.815 
.772 
.727 


1525 

1373 
1220 


350,000 
300,000 
250,000 


37 
37 
37 


.0972 
.0900 
.0821 


.680 
.630 
.575 


1068 
915 
763 



160 



PROPERTIES OF CONDUCTORS. 



Standard Copper Strands. — (Continued) . 

ROEBLING. 



Size. 


Wires. 


Outside 
Diameter. 


Weight. 
Lbs. per 
1000 ft. 


B. &. S. 


No. 


Size. 


0000 

000 

00 


19 
19 
19 


.1055 
.0941 
.0837 


.528 
.471 
.419 


645 
513 
406 




1 

2 


19 
19 

7 


.0746 
.0663 
.0975 


.373 
.332 
.293 


322 
255 
203 


3 

4 
5 


7 
7 

7 


.0866 
.0771 

.0688 


.260 
.231 
.206 


160 
127 
101 


6 

8 

10 


7 
7 
7 


.0612 
.0484 
.0386 


.184 
.145 
.116 


80 
50 
32 


12 
14 
16 


7 
7 
7 


.0306 
.0242 
.0193 


.092 
.073 
.058 


20 
12 

8 


18 


7 


.0151 


.045 


5 



0§€LATED COPPER WIRES AIJTD CABLE!. 
Weather-proof JLine and House Wire. Solid Conductor. 

Standard Underground Cable Co. 





Double Covered. 


Tripl 


e Covered. 




B. AS. 














Gauge. 


Lbs. per 


Lbs. per 


Diam. in 


Lbs. per 


Lbs. per 


Diam. in 




Mile. 


1000 ft. 


Mils. 


Mile. 


1000 ft. 


Mils. 


0000 


3690 


699 


725 


3910 


741 


780 


000 


2970 


562 


655 


3160 


598 


700 


00 


2390 


452 


585 


2560 


485 


635 





1860 


352 


545 


2020 


382 


590 


1 


1500 


284 


505 


1650 


312 


550 


2 


1225 


232 


470 


1340 


254 


515 


3 


980 


186 


385 


1050 


199 


450 


4 


800 


151 


360 


860 


163 


430 


5 


640 


121 


335 


700 


132 


400 


6 


520 


98 


300 


575 


109 


360 


7 


420 


79 


270 


465 


88 


335 


8 


345 


65 


245 


390 


74 


265 


9 


275 


52 


225 


320 


60 


255 


10 


235 


45 


195 


265 


50 


220 


11 


190 


36 


180 


225 


42 


205 


12 


145 


27 


165 


180 


34 


185 


14 


105 


20 


140 


130 


24 


160 


16 


80 


15 


130 


100 


19 


150 


18 


55 


10 


125 


80 


15 


145 


20 


42 


8 


122 


68 


12 


135 



PROPERTIES OP CONDUCTORS. 



ion A 



The following tables of weights of weatherproof wire are in general use 
by the manufacturers and are guaranteed to be correct within 3%. 



WEATHER-PROOF \\ I RE. 

Approximate Weights. — Solid. 





Double 


Braid. 


Triple 


Braid. 


Size. 










B. & S. 
Gauge. 


Lbs. per 


Lbs. p3r 


Lbs. per 


Lbs. per 


1000 ft. 


Mile. 


1000 ft. 


Mile. 


0000 


723 


3,817 


767 


4,050 


000 


587 


3,098 


629 


3,320 


00 


467 


2,467 


502 


2,650 





377 


1,989 


407 


2,150 


1 


294 


1,553 


316 


1,670 


2 


239 


1,264 


260 


1,370 


3 


185 


977 


199 


1,050 


4 


151 


795 


164 


865 


5 


122 


646 


135 


710 


6 


100 


529 


112 


590 


8 


66 


349 


75 


395 


9 


54 


283 


62 


325 


10 


46 


241 


53 


280 


12 


30 


158 


35 


185 


14 


20 


107 


25 


130 


16 


16 


83 


20 


105 


18 


12 


64 


16 


85 


20 


9 


48 


12 


65 





Approximate Weights. - 


— Stranded. 




Capacity. 










Circular 










Mills. 










2,000,000 


6,690 


35,323 


7,008 


37,000 


1,750,000 


5,894 


31,119 


6,193 


32,700 


1,500,000 


5,098 


26,915 


5,380 


28,400 


1,250,000 


4,264 


22,516 


4,508 


23,800 


1,000,000 


3,456 


18,246 


3,674 


19,400 


900,000 


3,127 


16,513 


3,332 


17,600 


800,000 


2,799 


14,779 


2,992 


15,800 


750,000 


2,635 


13,913 


2,822 


14,900 


700,000 


2,471 


13,045 


2,650 


14,000 


600,000 


2,093 


11,052 


2,235 


11,800 


500,000 


1,765 


9,318 


1,894 


10,000 


450,000 


1,601 


8,452 


1,724 


9,100 


400,000 


1,436 


7,584 


1,553 


8,200 


350,000 


1,248 


6,589 


1,345 


7,100 


300,000 


1,083 


5,721 


1,174 


6,200 


250,000 


907 


4,788 


985 


5,200 


Size-B. & S. 










Gauge. 










0000 


745 


3,935 


800 


4,220 


000 


604 


3,190 


653 


3,450 


00 


482 


2,544 


522 


2,760 





388 


2,051 


424 


2,240 


1 


303 


1,599 


328 


1,735 


2 


246 


1,301 


270 


1,425 


3 


190 


1,004 


206 


1,090 


4 


155 


820 


170 


900 


5 


126 


668 


140 


740 


6 


103 


544 


115 


610 


8 


68 


359 


78 


410 



160b 



WEATHER-PROOF WIRE. 



SLOW BURNING WEATHER-PROOF WIRE. 

Triple Braid — Black Outside. 



Capacity. 

Circular 

Mills. 


Stranded. 


Solid. 


Capacity. 

Circular 

Mills. 


Stranded. 


Solid. 


Lbs. 

per 
1000 

ft. 


Lbs. 
per 
Mile. 


Lbs. 

per 
1000 

ft. 


Lbs. 
per 
Mile. 


Lbs. 

per 
1000 

ft. 


Lbs. 

per 

Mile. 


Lbs. 

per 

1000 

ft. 


Lbs. 
per 
Mile. 


1000000 


3860 
3520 
3180 
2820 
2350 
1990 
1820 
1650 
1440 
1270 
1060 


20400 
18600 
16800 
14900 
12400 
10500 
9600 
8700 
7600 
6700 
5600 






Size— B.& 

S. Gauge. 

0000 

000 

00 



1 

2 

3 

4 

5 

6 

8 

10 

12 

14 

16 

18 


900 
735 
583 
480 
355 
290 
240 
195 
160 
132 
87 


4750 
3880 
3080 
2530 
1870 
1540 
1270 
1030 
845 
695 
460 


862 

710 

562 

462 

340 

280 

230 

190 

155 

127 

85 

60 

42 

30 

24 

19 


4550 


900000 






3750 


800000 






2970 


700000 






2440 


600000 






1800 


500000 






1480 


450000 






1220 


400000 






1000 


350000 






820 


300000 






670 


250000 






450 








315 








220 








160 








130 








100 

















WEATHER-PROOF IRON WIRE. 

Approximate Weights Per Mile. 



Iron Wire 
Gauge. 


Double 
Braid. 


Triple 
Braid. 


Iron Wire 
Gauge. 


Double 
Braid. 


Triple 
Braid. 


No. 4 
6 
8 
9 


860 
665 
470 
400 


940 
740 
525 
450 


No. 10 
12 
14 


350 
225 
145 


400 
260 
175 



slow mmno wire. 

Approximate Weights — Triple Braid. 



Capacity. 

Circular 

Mills. 


Stranded. 


Solid. 


Capacity. 

Circular 

Mills. 


Stranded. 


Solid. 


Lbs. 

per 

1000 

ft. 


Lbs. 
p-r 
Mile. 


Lbs. 

per 
1000 

ft. 


Lbs. 

per 

Mile. 


Lbs. 

per 
1000 

ft. 


Lbs. 

per 

Mile. 


Lbs. 
per 

1000 
ft. 


Lbs. 

per 

Mile. 


1000000 


3980 
3640 
3280 
2920 
2460 
2080 
1900 
1700 
1500 
1310 
1120 


21000 
19200 
17300 
15400 
13000 
11000 
10000 
9000 
7900 
6900 
590C 






Size— B. & 

S. Gauge. 

0000 

000 

00 



1 

2 

3 

4 

5 

6 

8 

10 
12 
14 
16 
18 


960 
785 
625 
510 
380 
335 
280 
230 
195 
165 
105 


5070 
4150 
3300 
2700 
2000 
1770 
1480 
1220 
1030 
870 
555 


925 
760 
600 
495 
365 
320 
270 
220 
190 
160 
100 
80 
55 
40 
30 
24 


4890 


900000 






4020 


800000 






3170 


700000 






2610 


600000 






1930 


500000 






1690 


450000 






1425 


400000 






1160 


350000 






1000 


300000 






845 


250000 






530 








420 








290 








210 








160 








130 

















RUBBER COVERED WIRES AND CABLES. 161 

Underwriters' Test of Rubber Covered Wire. 

Adopted Dec. 6, 1904. 

The Electrieal Committee of the Underwriters National Association 
recommended the following, which was adopted. 

Each foot of the completed covering must show a dielectric strength 
sufficient to resist throughout five minutes the application of an electro- 
motive force proportionate to the thickness of insulation in accordance 
with the following table: 

Thickness Breakdown Test 

in 64ths inches. on 1 Foot. 

1 3,000 Volts A. C. 

2 6,000 " 

3 9,000 '* 

4 11,000 " 

5 13,000 " 

6 15,000 " 

7 16,500 " 

8 18,000 " 

10 21,000 " 

12 23,500 " 

14 26,000 " 

16 '. . . . .28,000 M 

Standard Rubber Covered Wire* and Cables. 

(Made by General Electric Company.) 

Rubber covered wires and cables are insulated with two or more coats of 
rubber, the inner coat in all cases being free from sulphur or other sub- 
stance liable to corrode the copper, the best grade of fine Para being em- 
ployed. All conductors are heavily and evenly tinned. 

Five distinct finishes can be furnished as follows: — White or black braid, 
plain lead jacket, lead jacket protected by a double wrap of asphalted jute, 
lead jacket armored with a special steel tape, white armored, for submarine 
use. 

For use in conduits the plain lead covering is recommended, or if corro- 
sion is especially to be feared, the lead and asphalt. For use where no con- 
duit is available, the band steel armored cable is best, as it combines 
moderate flexibility with great mechanical strength, enabling it to resist 
treatment which would destroy an unarmored cable. 

In addition to the ordinary galvanometer tests, wires and cables are 
tested with an alternating current (as specified in table) before shipping. 

Special rubber covered wire and cable with lead jackets will be covered 
with the following thicknesses of lead unless otherwise specified: 

Outside diameter of cable (inside diameter of lead pipe). 

Up to and including .500" - • eV 

.501" to .750", inclusive . . -is" 

.751" to 1.250", inclusive &" 

1.251" to 1.5", inclusive &" 

Larger than 1.501" £" 



162 



PROPERTIES OF CONDUCTORS. 



Standard Conductor. National Electric Code, 
General Electric Company. 

I. Solid. 



Size. 


3 a 

03-73 
ft 


Weight 

per 1000 ft. 

in lbs. 


o 
o 

'5 03 


DQ 

$ 

o 

03 - 


o a; 
Jl 03 


<v 

03 - 

c 53 


Test Pres- 
sure for 30 
min. 


B. & S. 


£-6 


03 


T3 03 

*3 


03 • 
4J 03 


18 


.159 


20 


33 


170 


.253 


3 
64 


_3_ 
64 


1000 


1500 


16 


.190 


25 


40 


203 


.284 


_3_ 
64 


3 
64 


1000 


1500 


14 


.203 


33 


47 


220 


.297 


A 


_3_ 
64 


1000 


1500 


12 


.220 


43 


58 


243 


.314 


_3_ 
64 


3 
64 


1000 


1500 


10 


.241 


58 


74 


273 


.335 


3 
64 


_3_ 
64 


1000 


1500 


8 


.268 


81 


99 


316 


.362 


A 


A 


1000 


1500 


6 


.352 


130 


150 


389 


.411 


A 


1 
T6~ 


2000 


2500 


5 


.372 


159 


180 


433 


.431 


3 
64 


1 
15 


2000 


2500 


4 


.394 


187 


210 


476 


.453 


_3_ 
64 


A 


2000 


2500 


3 


.419 


230 


254 


538 


.478 


3 
64 


i 


2000 


2500 


2 


.448 


273 


298 


599 


.507 


_3_ 
64 


1 


2000 


2500 


1 


.540 


362 


390 


722 


.570 


_3_ 
64 


A 


2500 


3500 





.576 


438 


467 


981 


.636 


1 
T6" 


_5_ 
64 


2500 


3500 


00 


.616 


533 


562 


1116 


.675 


1 
TB~ 


A 


2500 


3500 


000 


.661 


648 


678 


1279 


.721 


1 
16 


5 
64 


2500 


3500 


0000 


.711 


794 


827 


1473 


.771 


A 


-5- 
61 


2500 


3500 



Note. ■ — Wire and cable No. 1 B. & S and larger have tape over rubber 
in addition to braid. Add \\" to single braid for diameter of double braid. 



RUBBER INSULATED WIRES AND CABLES. 



163 



Standard Conductor. — National Electric Code, 
General Electric Company.— Cont. 

II. Stranded. 





Us 


Weight 


o . 

O 0> 


1 




BQ 


Test Pres- 




IJS 


per 1000 ft. 


o 


v_ 03 
DO'S 




sure for 30 


Size. 




in 


ibs. 


S3 S 


.fl- 


° a 


min. 


B.&S. and 
CM. 








CM 






m 1 "™ 1 




+3 - 


■S-d 

0QPQ 


0> 


fcC V 


ea a 
.290 


= t 


*6 


o . 


16 


.196 


28 


43 


210 


A 


A 


1000 


1500 


14 


.212 


35 


50 


228 


.306 


A 


A 


1000 


1500 


12 


.231 


46 


63 


253 


.325 


A 


A 


1000 


1500 


10 


.255 


63 


81 


288 


.349 


A 


A 


1000 


1500 


8 


.285 


86 


107 


335 


.379 


3 

64 


A 


1000 


1500 


6 


.374 


139 


162 


410 


.433 


A 


A 


2000 


2500 


5 


.396 


165 


189 


455 


.455 


3 
64 


A 


2000 


2500 


4 


.422 


197 


221 


507 


.481 


A 


A 


2000 


2500 


3 


.450 


240 


265 


567 


.509 


A 


A 


2000 


2500 


2 


.512 


289 


316 


639 


.541 


A 


A 


2000 


2500 


1 


.587 


381 


410 


935 


.647 


1 
T6~ 


A 


2500 


3500 


100000 


.616 


447 


476 


1030 


.676 


A 


A 


2500 


3500 





.626 


464 


493 


1055 


.686 


1 
T6~ 


A 


2500 


3500 


125000 


.656 


513 


544 


1128 


.716 


A 


_5_ 
64 


2500 


3500 


00 


.669 


563 


595 


1202 


.730 


1 


A 


2500 


3500 


150000 


.690 


617 


650 


1275 


.750 


1 
T6~ 


A 


2500 


3500 


000 


.721 


683 


716 


1372 


.781 


A 


A 


2500 


3500 


200000 


.763 


800 


834 


1532 


.823 


i 


A 


2500 


3500 


0000 


.779 


835 


869 


1583 


.839 


A 


_5_ 
64 


2500 


3500 


250000 


.873 


1032 


1095 


2047 


.948 


A 


A 


4000 


5000 


300000 


.932 


1218 


1283 


2303 


1.008 


A 


A 


4000 


5000 


350000 


.976 


1381 


1449 


2527 


1.056 


A 


A 


4000 


5000 


400000 


1.027 


1548 


1617 


2753 


1.102 


A 


A 


4000 


5000 


500000 


1.113 


1888 


1958 


3202 


1.189 


A 


A 


4000 


5000 


600000 


1.222 


2275 


2354 


3725 


1.298 


A 


A 


5000 


6000 


700000 


1.294 


2619 


2707 


4148 


1.370 


A 


7 
64" 


5000 


6000 


750000 


1.328 


2791 


2880 


4355 


1.404 


A 


A 


5000 


6000 


800000 


1.360 


2959 


3051 


4912 


1.436 


A 


A 


5000 


6000 


900000 


1.423 


3295 


3390 


5340 


1.531 


A 


A 


5000 


6000 


1000000 


1.482 


3624 


3721 


5752 


1.590 


A 


A 


5000 


6000 


1250000 


1.650 


4496 


4600 


7704 


1.820 


i 


1 


5000 


6000 


1500000 


1.772 


5319 


5432 


8754 


1.942 


J 


1 
t 


5000 


6000 


2000000 


1.992 


6958 


7075 


10821 


2.162 


* 


i 1 


5000 


6000 



Note. — Wire and cable No. 1 B. & S. and larger have tape over rub- 
ber in addition to braid. Add -fc" to single braid for diameter of double 
braid. 



RUBBER INSULATED WIRES AND CABLES. 



163a 



Diameters and Weights 


oi Small Sizes of Cotton Covered Wire. 






Diameters 




Weighl 


> in Pounds per 1000 Feet. 


Size 














B. &S. 




















s.c.c. 


D.C.C. S.* 


3.C. 


D.S.C 


5. S.C.C. 


D.C.C. 


s.s.c. 


D.S.C. 


14 


.0700 


.0740 






12.684 


12.918 






15 


.0630 


.0670 










10.082 


10.274 








16 


.0560 


.0590 










8.012 


8.176 








17 


.0500 


.0530 










6.375 


6.510 








18 


.0450 


.0480 










5.081 


5.188 








19 


.0400 


.0440 










4.043 


4.130 








20 


.0360 


.0400 










3.218 


3.289 








21 


.0325 


.0365 










2.569 


2.628 








22 


.0294 


.0334 










2.055 


2.106 








23 


.0265 


.0305 .( 


)260 


.029( 


) 1.630 


1.676 


1 


573 


1.604 


24 


.0241 


.0280 .( 


)230 


.026( 


) 1.297 


1.344 


1 


241 


1.298 


25 


.0220 


.0260 .( 


)210 


.024( 


) 1.036 


1.082 




991 


1.040 


26 


.0200 


.0240 .( 


)190 


.022( 


) .828 


.873 




791 


.833 


27 


.0180 


.0220 .( 


)170 


.020( 


) .661 


.703 




631 


.666 


28 


.0166 


.0206 .( 


)156 


.018( 


1 .524 


.562 




499 


.521 


29 


.0153 


.0193 .( 


)140 


.017( 


) .421 


.457 




397 


.416 


30 


.0140 


.0180 .( 


)125 


.0151 


) .336 


.372 




315 


.332 


31 


.0130 


.0170 .( 


)114 


.0131 


) .271 


.307 




254 


.267 


32 


.0119 


.0159 .( 


1105 


.013( 


) .215 


.248 




203 


.214 


33 


.0110 


.0150 .( 


)095 


.012( 


) .174 


.201 




161 


.172 


34 


.0103 


.0143 .( 


)088 


.0}K 


1 .141 


.161 




130 


.140 


35 


.0096 


.0136 .( 


)076 


.009( 


J .120 


.137 




110 


.119 


36 


.0085 


.0120 .( 


)070 


.009( 


) .099 


.112 




089 


.096 


38 




( 


)060 


.008( 


) 






058 


.065 


40 




( 


)05C 




.( 


)07( 


) 






037 


.040 



164 



PROPERTIES OF CONDUCTORS. 



General Electric Company Rubber Insulated Win* and 
Cable (fs" Rubber). 

Test Pressure. — Red Core, 2500 Volts; White Core, 3000 Volts, 
for 30 Minutes. 

Wire. 





Diameter, 
Single 
Braid, 
Inches. 


Weight 

per 1000 ft. 

in Lbs. 


8a 

rH 


o5 
S 


Si 

a? a 

a rt 

Xi O 

Hh3 


Insulation 

Resistance in 

Megohms 

per Mile. 


Size. 
B. &.S. 


v-4 

S u 
icffl 






Red 
Core. 


White 
Core. 


16 
14 
12 
10 

8 


.221 
.234 
.251 
.272 
.299 


33 
40 
51 
67 
91 


48 
56 
67 
85 
109 


233 
249 
273 
305 
348 


.315 
.328 
.345 
.366 
.393 


1 

64 

A 


350 
350 
350 
350 
350 


600 
600 
600 
600 
600 



Cable. 



16 


.227 


39 


56 


242 


.326 


A 


350 


600 


14 


.243 


43 


61 


260 


.337 


_3_ 
64 


350 


600 


12 


.262 


60 


80 


285 


.356 


A 


350 


600 


10 


.286 


78 


99 


316 


.380 


A 


350 


600 


8 


.316 


105 


127 


360 


.395 


& 


350 


600 



Note. — Add t$" to single braid for diameter of double braid. 



RUBBER INSULATED WIRES AND CABLES. 165 



General Electric Company Runner Insulated Wire and 
Cable (gV Runner). 

Test Pressure. — Red Core, 5000 Volts; White Core, 6000 Volts, 
for 30 Minutes. 

Wire. 



Size. 
B. & S. and 


Diameter, 
Single 
Braid, 
Inches. 


Weight 

per 1000 ft. 

in lbs. 


8a 
Kg 

W)h3 


tn 
-CI 

<d d 

ii 
si 


£3 


Insulation 

Resistance in 

Megohms 

per Mile. 


C. M. 


^73 

rs 




Red 
Core. 


White 
Core. 


14 


.296 


61 


80 


293 


.376 


A 


400 


700 


12 


.313 


73 


93 


318 


.393 


_3_ 
64 


400 


700 


10 


.354 


90 


111 


351 


.414 


A 


400 


700 


8 


.381 


115 


138 


395 


.441 


A 


400 


700 


6 


.414 


153 


177 


457 


.474 


A 


400 


700 


5 


.434 


181 


205 


498 


.494 


A 


350 


600 


4 


.456 


211 


236 


545 


.516 


& 


350 


600 


3 


.481 


253 


280 


603 


.541 


A 


350 


600 


2 


.540 


313 


340 


674 


.569 


A 


350 


600 


1 


.571 


374 


402 


913 


.632 


A 


350 


600 





.607 


449 


478 


1025 


.667 


A 


350 


600 


00 


.647 


543 


574 


1160 


.707 


1 
T6" 


300 


500 


000 


.692 


661 


694 


1323 


.752 


A 


300 


500 


0000 


.742 


806 


841 


1519 


.802 


A 


300 


500 



Cable. 



14 


.305 


69 


91 


304 


.385 


A 


400 


700 


12 


.324 


83 


105 


332 


.403 


A 


400 


700 


10 


.368 


103 


126 


367 


.427 


A 


400 


700 


8 


.398 


131 


155 


416 


.457 


A 


400 


700 


6 


.436 


176 


201 


485 


.495 


A 


400 


700 


5 


.458 


203 


229 


528 


.518 


A 


350 


600 


4 


.484 


239 


266 


583 


.523 


A 


350 


600 


3 


.542 


285 


313 


647 


.571 


A 


350 


600 


2 


.574 


336 


365 


878 


.634 


l 
T6" 


350 


600 


1 


.618 


409 


438 


996 


.678 


A 


350 


600 


100000 


.647 


46^ 


498 


1084 


.707 


1 
T6~ 


350 


600 





.657 


485 


515 


1108 


.717 


tV 


350 


600 


125000 


.687 


562 


566 


1182 


.747 


1 
T6~ 


300 


500 


00 


.701 


585 


618 


1255 


.761 


1 
T6" 


300 


500 


150000 


.721 


638 


672 


1329 


.781 


A 


300 


500 


000 


.752 


709 


743 


1430 


.812 


1 
1j& 


300 


500 


200000 


.794 


826 


861 


1590 


.854 


tV 


300 


500 


0000 


.810 


864 


900 


1643 


.870 


1 

T6" 


300 


500 



Note. — Add ^" to single braid for diameter of double braid. 



166 



PROPERTIES OF CONDUCTORS. 



General .Electric Company Rubber Insulated Wire 
(_y Rubber). 

Test Pressure. — Red Core, 7500 Volts ; White Core, 9000 Volts, 
for 30 Minutes. 

I. Wire. 



Size. 


.3 <D 

si 


Weight 

per 1000 ft. 

in lbs. 


83 

WW 


*3 


o_ GO 

HW 


Insulation 

Resistance in 

Megohms 

per Mile. 


B. &S. 


£-6 
dQpq 


I' 3 


^ 8 

wo 


£5 


14 


.379 


84 


106 


372 


.438 


A 


600 


1000 


12 


.396 


98 


121 


398 


.455 


3 

6~4" 


600 


1000 


10 


.417 


117 


141 


432 


.476 


A 


600 


1000 


8 


.444 


144 


169 


479 


.503 


_3_ 
64 


600 


1000 


6 


.477 


186 


213 


547 


.536 


3 
64 


550 


900 


5 


.527 


224 


252 


583 


.556 


3 

6~4 


550 


900 


4 


.549 


259 


287 


635 


.578 


_3_ 
64 


550 


900 


3 


.572 


300 


329 


852 


.633 


A 


550 


900 


2 


.603 


351 


380 


933 


.663 


i 


550 


900 


1 


.634 


414 


445 


1028 


.694 


A 


550 


900 





.670 


493 


525 


1142 


.730 


A 


500 


800 


00 


.710 


591 


625 


1282 


.770 


1 
16" 


300 


800 


000 


.755 


712 


746 


1450 


.815 


A 


300 


800 


0000 


.805 


859 


895 


1649 


.865 


A 


300 


800 



RUBBER INSULATED WIRES AND CABLES. 



167 



General Electric Company Rubber Insulated Cable 
(gV Rubber). 

Test Pressure. — Red Core, 7500 Volts; White Core, 9000 Volts, 
for 30 Minutes. 









II. 


Cable. 










Size. 


.3 <0 

si 


Weight 

per 1000 ft. 

in lbs. 


II 

II 


m 

11 


3 J 

<u a 

7* TO 


Insulation 

Resistance in 

Megohms 

per Mile. 


B.&S. and 
CM. 


S-6 






0> 


14 


.388 


89 


113 


373 


.447 


A 


600 


1000 


12 


.407 


103 


127 


401 


.466 


A 


600 


1000 


10 


.431 


125 


150 


439 


.490 


A 


600 


1000 


8 


.461 


156 


182 


491 


.520 


3 

64 


600 


1000 


6 


.529 


210 


237 


563 


.558 


A 


550 


900 


5 


.551 


240 


268 


608 


.580 


A 


550 


900 


4 


.577 


277 


306 


821 


.636 


A 


550 


900 


3 


.605 


322 


351 


895 


.665 


1 


550 


900 


2 


.637 


376 


407 


981 


.697 


a 


550 


900 


1 


.681 


454 


486 


1104 


.741 


i 

T6~ 


550 


900 


100000 


.710 


514 


547 


1192 


.770 


A 


550 


900 





.720 


530 


564 


1216 


.780 


A 


500 


800 


125000 


.750 


582 


616 


1290 


.810 


A 


500 


800 


00 


.764 


635 


669 


1364 


.824 


1 
T6~ 


500 


800 


150000 


.784 


689 


723 


1443 


.844 


A 


500 


800 


000 


.815 


760 


796 


1545 


.875 


A 


500 


800 


200000 


.872 


914 


977 


1929 


.948 


A 


500 


800 


0000 


.888 


953 


1018 


1987 


.964 


A 


500 


800 


250000 


.955 


1084 


1149 


2178 


1.031 


A 


400 


700 


300000 


.994 


1278 


1346 


2444 


1.070 


A 


400 


700 


350000 


1.042 


1445 


1514 


2672 


1.118 


A 


400 


700 


400000 


1.088 


1617 


1686 


2901 


1.164 


A 


400 


700 


500000 


1.175 


1958 


2034 


3350 


1.251 


A 


350 


600 


600000 


1.253 


2308 


2391 


3790 


1.329 


A 


350 


600 


700000 


1.325 


2657 


2747 


4222 


1.401 


A 


350 


600 


750000 


1.359 


2831 


2923 


4781 


1.466 


A 


300 


500 


800000 


1.391 


3031 


3126 


5012 


1.498 


A 


300 


500 


900000 


1.454 


3343 


3438 


5432 


1.561 


A 


300 


500 


1000000 


1.513 


3675 


3773 


5852 


1.620 


A 


300 


500 



Note. — Add ^" to single braid for diameter of double braid. 



168 



PROPERTIES OF CONDUCTORS. 



General JElectric Company Rubber Insulated Wire and 
Cable ( 5 y Rubber). 

Test Pressure . — Red Core, 12,000 Volts ; White Core. 15,000 
Volts, for 30 Minutes. 

L Solid. 



Size. 


fa 

5« 


Weight 

per 1000 ft. 

in lbs. 


11 

1— 1 

5 ° 

fctH 


u 

IT 

S*g 


°£ 

.§13 


Insulation 

Resistance in 

Megohms 

per Mile. 


B. &S. 


®T3 

bird 

o S 

OQffl 


o * 


Red 
Core. 


White 
Core. 


14 


.534 


156 


184 


512 


.562 


A 


700 


1200 


12 


.551 


173 


201 


540 


.580 


3 
64 


700 


1200 


10 


.572 


196 


224 


735 


.601 


A 


700 


1200 


8 


.598 


226 


255 


792 


.658 


A 


700 


1200 


6 


.632 


272 


303 


872 


.692 


1 
T6~ 


700 


1200 


5 


.652 


302 


333 


924 


.712 


1 
T6~ 


600 


1100 


4 


.674 


340 


372 


982 


.734 


A 


600 


1100 


3 


.699 


386 


419 


1053 


.759 


i 1 ? 


600 


1100 


2 


.728 


441 


474 


1137 


.788 


A 


600 


1100 


1 


.759 


509 


543 


1235 


.819 


A 


600 


1100 





.795 


592 


638 


1356 


.855 


A 


550 


1000 


00 


.850 


696 


732 


1708 


.926 


A 


550 


1000 


000 


.895 


851 


926 


1898 


.971 


5 
64 


550 


1000 


0000 


.945 


1011 


1084 


2109 


1.021 


5 
64 


550 


1000 



RUBBER INSULATED WIRES AND CABLES. 



1C9 



Cleneral Electric- Company Rubber Insulated Wire and 
Cable ( 5 y Rubber) — Continued. 

II. Stranded. 



Size. 


- X 


Weight 

per 1000 ft. 

in lbs. 


o • 

1—1 

II 

fc£H-} 

'o - 


i 
■a 

w ■ 

a 

c3 

3 


O 0> 

»-£ 

02 O 

cj d 
M - 

■s'S 


Insulation 

Resistance in 

Megohms 

per Mile. 


B. & S. and 
CM. 


5-d 

Si 






2 6 

£ o 


14 


.543 


162 


190 


524 


.572 


A 


700 


1200 


12 


.562 


181 


209 


566 


.591 


3 
64 


700 


1200 


10 


.586 


205 


233 


758 


.646 


A 


700 


1200 


8 


.616 


239 


268 


822 


.676 


1 


700 


1200 


6 


.654 


290 


320 


912 


.714 


A 


600 


1100 


5 


.676 


323 


354 


968 


.736 


1 
T6~ 


600 


1100 


4 


.702 


365 


397 


1034 


.762 


A 


600 


1100 


3 


.730 


413 


447 


1112 


.790 


i 

IT 


600 


1100 


2 


.762 


472 


506 


1201 


.822 


A 


600 


1100 


1 


.806 


555 


591 


1332 


.866 


A 


550 


1000 


100000 


.850 


619 


656 


1638 


.926 


5 
64 


550 


1000 





.860 


637 


675 


1666 


.936 


5 
64 


550 


1000 


125000 


.890 


708 


759 


1750 


.966 


A 


550 


1000 


00 


.904 


780 


844 


1834 


.980 


A 


550 


1000 


150000 


.924 


838 


903 


1917 


1.000 


3 
64 


550 


1000 


000 


.955 


915 


981 


2032 


1.031 


A 


550 


1000 


200000 


.997 


1042 


1110 


2212 


1.073 


3 
64 


500 


900 


0000 


1.013 


1083 


1151 


2271 


1.089 


A 


500 


900 


250000 


1.060 


1225 


1294 


2473 


1.136 


A 


500 


900 


300000 


1.119 


1424 


1494 


2745 


1.195 


A 


500 


900 


350000 


1.167 


1600 


1675 


2980 


1.243 


A 


450 


800 


400000 


1.213 


1781 


1860 


3218 


1.289 


A 


450 


800 


500000 


1.300 


2138 


2226 


3679 


1.376 


A 


450 


800 


600000 


1.378 


2497 


2589 


4474 


1.485 


A 


400 


700 


700000 


1.450 


2854 


2950 


4938 


1.557 


A 


400 


700 


750000 


1.484 


3030 


3127 


5161 


1.591 


A 


350 


600 


800000 


1.516 


3205 


3304 


5384 


1.623 


A 


350 


600 


900000 


1.579 


3557 


3658 


5829 


1.687 


A 


350 


600 


1000000 


1.638 


3900 


4004 


7085 


1.808 


i 


350 


600 



Note. — Add ^$" to single braid for diameter of double braid. 

For ^j" insulation the insulation resistance will be in proportion with &" 
and 5 y insulation. 

Test pressure for -^ ,f Red Core, 10,000 volts; White Core, 12,000 volts 
for 30 minutes. 



170 



PROPERTIES OF CONDUCTORS. 



Creneral Electric ( ompaiiv Three Conductor Cable, 
White Core Insulation, 

Test Pressure. — 3000 Volts for 30 Minutes. 





Leaded. 


Braided. 


Insula- 
tion 
Resist- 
ance in 
Megohms 
per Mile. 


Size. 

B. &S. 

and CM. 


££2 


Hi 

Pi 


t-" . CO 

«t r ^ 


3 « 


.2 <8 
5.g 


3&S 

.SP .© 


8 


1192 


A 


.805 


A 


.740 


449 


600 


6 


1567 


A 


.918 


A 


.852 


551 


500 


5 


1728 


tV 


.966 


A 


.900 


653 


500 


4 


1889 


1 
T5 


1.022 


5 
64 


.956 


756 


500 


3 


2123 


A 


1.082 


A 


1.016 


909 


500 


2 


2358 


A 


1.152 


A 


1.077 


1062 


500 


1 


2847 


A- 


1.314 


5 
64 


1.239 


1352 


500 


100000 


3032 


A 


1.376 


A 


1.301 


1492 


500 





3217 


A 


1.398 


5 
64 


1.327 


1632 


500 


125000 


3631 


A 


1.494 


_5_ 
64 


1.386 


1800 


500 


00 


4045 


A 


1.524 


A 


1.427 


1967 


500 


150000 


4332 


A 


1.567 


A 


1.470 


2175 


500 


000 


4619 


A 


1.635 


A 


1.537 


2381 


500 


200000 


4968 


A 


1.724 


JL 

64 


1.626 


2638 


500 


0000 


5318 


A 


1.759 


_5_ 
64 


1.662 


2895 


500 





Test Pressure. — 8000 Volts for 30 Minutes. 






Leaded. 


Braided. 


Insula- 
tion 
Resist- 
ance in 
Megohms 
per Mile. 


Size. 
B. &S. 
and CM. 




It 


<».S • 

<D ~ m 
o V o 

■2^2 


$1 


.SP .o 

££2 


8 


1892 


1.106 


A 


1.040 


641 


1000 


6 


2144 


1.188 


A 


1.122 


796 


900 


5 


2322 


1.236 


5 
64 


1.170 


912 


900 


4 


2499 


1.292 


A 


1.226 


1029 


900 


3 


2926 


1.353 


A 


1.287 


1204 


900 


2 


3354 


1.453 


A 


1.356 


1378 


900 


1 


3760 


1.548 


A 


1.451 


1647 


900 


100000 


3947 


1.611 


A 


1.514 


1775 


900 





4134 


1.633 


A 


1.530 


1904 


800 


125000 


4385 


1.697 


A 


1.594 


2083 


800 


00 


4636 


1.727 


A 


1.630 


2261 


800 


150000 


5372 


1.770 


A 


1.673 


2478 


800 


000 


6108 


1.900 


4 


1.740 


2696 


800 


200000 


6500 


1.991 


ft 


1.831 


2967 


800 


0000 


6893 


2.026 


i 


1.865 


3238 


800 



RUBBER INSULATED WIRES AND CABLES. 



171 



Oeneral Electric Company Three Conductor Cable, 
White Core Insulation. 



Test Pressure. — 15,000 Volts for , 


B0 Minutes. 






Leaded. 




Braided. 
















Insulation 

Resistance 

in Megohms 

per Mile. 


Size. 

B. & S. 

and C. M. 


Weight, 
lbs. per 
1000 ft. 


n 

08 >-H 

15 .a 


§13.3 


JMJ 

3.s 




8 


2452 


1.376 


A 


1.310 


913 


1300 


6 


3077 


1.490 


A 


1.392 


1097 


1200 


5 


3282 


1.538 


A 


1.440 


1224 


1200 


4 


3488 


1.594 


A 


1.496 


1352 


1200 


3 


3767 


1.654 


A 


1.556 


1536 


1200 


2 


4046 


1.723 


A 


1.626 


1721 


1200 


1 


4471 


1.818 


A 


1.721 


2020 


1100 


100000 


5120 


1.943 


* 


1.783 


2160 


1100 





5769 


1.965 


* 


1.800 


2301 


1100 


125000 


6055 


2.030 


* 


1.865 


2490 


1100 


00 


6342 


2.060 


* 


1.900 


2679 


1100 


150000 


6677 


2.103 


* 


1.943 


2907 


1100 


000 


7013 


2.170 


* 


2.010 


3135 


1100 


200000 


7418 


2.261 


ft 


2.101 


3421 


1100 


0000 


7823 


2.295 


ft 


2.135 


3707 


1100 



Test Pressure. — 26,000 Volts for 30 Minutes. 







Leaded. 




Braided. 
















Insulation 


Size. 

B. &S. 

and C. M. 












.sp a © 
t££2 


H 02 

n 

H.s 




§J 

rat— ( 

S.g 


bf7o 

'© 02 O 


Resistance 

in Megohms 

per Mile. 


8 


4103 


1.878 


A 


1.781 


1558 


1600 


6 


4437 


1.960 


3 
32 


1.863 


1770 


1500 


5 


4661 


2.008 


_3_ 
32 


1.911 


1919 


1500 


4 


4885 


2.064 


& 


1.967 


2068 


1500 


3 


5710 


2.124 


A 


2.027 


2281 


1500 


2 


6535 


2.256 


1 

8 


2.096 


2495 


1500 


1 


6995 


2.351 


* 


2.183 


2792 


1500 


100000 


7259 


2.414 


* 


2.246 


2968 


1400 





7523 


2.436 


4 


2.271 


3145 


1400 


125000 


7828 


2.500 


1 
t 


2.335 


3354 


1400 


00 


8133 


2.530 


1 
8 


2.371 


3563 


1400 


150000 


8490 


2.576 


* 


2.417 


3813 


1400 


000 


8848 


2.641 


* 


2.481 


4064 


1400 


200000 


9292 


2.731 


* 


2.571 


4378 


1300 


0000 


9736 


2.766 


1 


2.606 


4693 


1300 



172 



PROPERTIES OF CONDUCTORS. 



General Electric- Company Extra Flexible Dynamo Cable. 

This is adapted for use as brush-holder leads, or to any use where great 
flexibility is required. The finish is black glazed linen braid. Each wire 
of the strand is No. 25 B. & S. 







Dimensions in Inches. 


Number 


Circular 
Mils. 








Wires in 
Strand. 


Diameter 


Thickness 


Diameter 






Bare. 


Rubber. 


Over All. 


25 


8,000 


.108 


.047 


.275 


50 


16,000 


.150 


.047 


.320 


75 


24,000 


.205 


.047 


.375 


100 


32,000 


.235 


.047 


.450 


150 


48,000 


.285 


.047 


.500 


200 


64,000 


.325 


.047 


.540 


250 


80,000 


.350 


.047 


.600 


300 


96,000 


.385 


.065 


.665 


350 


112,000 


.425 


.065 


.705 


400 


128,000 


.460 


.065 


.740 


450 


144,000 


.485 


.065 


.765 


500 


160,000 


.570 


.065 


.810 


550 


176,000 


.530 


.065 


.830 


600 


192,000 


.570 


.065 


.870 


650 


208,000 


.605 


.065 


.935 


700 


224,000 


.625 


.065 


.955 


750 


240,000 


.640 


.065 


.970 


800 


256,000 


.680 


.065 


1.010 


900 


288,000 


.700 


.065 


1.030 


1000 


320,000 


.725 


.065 


1.055 


1250 


400,000 


.825 


.065 


1.165 


1500 


480,000 


.880 


.065 


1.213 


1750 


560,000 


.960 


.093 


1.360 


2000 


640,000 


1.060 


.093 


1.410 


2250 


720,000 


1.100 


.093 


1.500 


2500 


800,000 


1.200 


.093 


1.600 


2750 


880,000 


1.250 


.093 


1.650 


3125 


1,000,000 


1.430 


.093 


1.830 



SPECIAL CABLES. 



173 



Rubber Insulated Cable for Car Wiring-. 

Single Conductor, Weatherproof Finish. 

This class of cable is made with separator, standard code thickness of insu- 
lation tape and single-braid weatherproof finish. 

Standard Strands. 







Finished Weight 


Diameter in 
Inches. 


Size B. & S. 


Stranding. 


in Pounds per M 
Feet. 


14 


7/. 0243 


37 


.23 


12 


7/. 0306 


48 


.25 


10 


7/. 0386 


64 


.27 


8 


7/. 0485 


90 


.31 


6 


7/. 0613 


139 


.38 


4 


7/. 0773 


197 


.42 


2 


7/. 0974 


289 


.51 


1 


19/. 0664 


381 


.59 


I/O 


19/. 0746 


464 


.63 


2/0 


19/. 0838 


563 


.67 


3/0 


19/. 0940 


683 


.72 


4/0 


19/. 1056 


835 


.78 


250,000 


37/. 0823 


1032 


.87 



For each additional braid, add approximately ^g inch to diameter. 

Single Conductor, Flameproof Finish. 
National Electric Code Standard. 

This class of cable is made with separator, standard code thickness of in- 
sulation and double braid finish — the first braid is cotton, well compounded, 
the second or finishing braid is filled asbestos. 

Standard Strands. 







Finished Weight 


Diameter in 
Inches. 


Size B. & S. 


Stranding. 


in Pounds per M 
Feet. 


14 


7/. 0243 


65 


.31 


12 


7/. 0306 


78 


.33 


10 


7/. 0386 


99 


.36 


8 


7/. 0485 


128 


.39 


6 


7/.0613 


189 


.47 


4 


7/. 0773 


255 


.52 


2 


7/. 0974 


353 


.58 


1 


19/. 0664 


461 


.68 


I/O 


19/. 0746 


545 


.72 


2/0 


19/. 0838 


650 


.77 


3/0 


19/. 0940 


778 


.82 


4/0 


19/. 1056 


937 


.88 


250,000 


37/. 0823 


1138 


.99 


300,000 


37/. 0906 


1330 


1.05 


350,000 


37/. 0974 


1497 


1.10 


500,000 


61/. 0906 


2024 


1.23 


750,000 


61/. 1110 


2945 


1.45 


1,000,000 


61/. 1281 


3801 


1.62 



SPECIAL CABLES. 



173a 



Rubber Insulated Cable for Type TO Control. 

For connecting contactors and controllers, 19/25 B. & S. single conductor 
s Vinch rubber insulation is used; double braid weatherproof finish. The 
nearest equivalent size is number 12 B. & S. 

The weight per 1000 feet is 52 pounds, and diameter .25 inches. 

Train Cables. 

Multiple conductors, each single conductor being composed of 19/25 B. & S. 
wires, rubber covered, single braid and a tape and braid finish overall. 



Number of Conductors^ 


Diameter Overall. 


Weight per 1000 Ft. 


5 


.7 


255 


6 


.75 


343 


7 


.75 


373 


9 


.85 


479 


10 


.93 


503 


12 


1.03 


613 


20 


1.28 


893 



Jumper Cables. 

Are similar in construction t* train cables with the exception that the group 
of conductors is surrounded by a rubber jacket and a double braid finish. 



Number of Conductors. 


Diameter Overall. 


Weight per 1000 Feet. 


5 


.88 


371 


6 


.94 


461 


7 


.94 


491 


9 


1.00 


632 


10 


1.07 


687 


12 


1.30 


846 


20 


1.54 


1246 



Both train and jumper cables have distinctive marking threads woven in 
the braid of each conductor. 



174 



PROPERTIES OF CONDUCTORS. 



WAVY STA\»AHJ) HIKES. 

In the following table are given sizes of Navy Standard Wires as per 
specifications issued by the Navy Department in March, 1897. 



d 

3 



4,107 

9,016 

11,368 

14,336 

18,081 

22,799 

30,856 

38,912 

49.077 

60;088 

75,776 

99,064 

124,928 

157,563 

198,677 

250,527 

296,387 

373,737 

413,639 



8-T3 




.J3 S3 


*** 


^QQ 


o . 


£.s 


N^ 1 




m 


1 


14 


7 


19 


7 


18 


7 


17 


7 


16 


7 


15 


19 


18 


19 


17 


19 


16 


37 


18 


37 


17 


61 


18 


61 


17 


61 


16 


61 


15 


61 


14 


91 


15 


91 


14 


127 


15 



Diameter 
Inches. 



Over 
copper. 



.06408 
. 10767 
. 12090 
.13578 
. 15225 
.17121 
.20150 
.22630 
. 25410 
. 28210 
.31682 
.36270 
.40734 
.45738 
.51363 
.57672 
. 62777 
. 70488 
.74191 



Over 

Para 

rubber 



.0953 
.1389 
.1522 
.1670 
.1837 
.2025 
.2328 
.2576 
.2854 
.3134 
.3481 
.3940 
.4386 
.4885 
.5449 
.6080 
.6590 
.7361 
.7732 



Diameter in 


32ds 


of 


an inch. 


Over 
vulc. 
rubber . 


Over 


Over 


tape. 


braid. 


7 


9 


11 


10 


12 


14 


10 


12 


14 


10 


12 


14 


11 


13 


15 


12 


14 


16 


12 


14 


16 


13 


15 


17 


14 


16 


18 


15 


17 


19 


16 


18 


20 


18 


20 


22 


19 


21 


23 


20 


22 


24 


22 


24 


26 


24 


26 


28 


26 


28 


30 


29 


31 


33 


30 


32 


34 



at 



«1§ 



56.9 

103 

108.5 

115.5 

140 

1651 

184 

218 

260i 

314 

371 

463 

557 

647 

794 

970 
1,138 
1,420 
1,553 



Double Conductor, Plain, 2-7-22 B. & S. . . . 

Double Conductor, Silk, 2-7-25 B. & S 

Double Conductor, Diving Lamp, 2-7-20 B. & S. 
Bell Cord, 1-16 B. & S 



181.5 

28 
218.3 

29.7 



PAPER nSILATED AXI> LEADED WIRES AND 

CABLES. 

GENERAL ELECTRIC CO. 



There will be found on the following pages data of a full line of paper 
insulated and lead covered wires and cables. All cables insulated with 
fibrous covering depend for their successful operation and maintenance 
upon the exclusion of moisture by the lead sheath; and this fact should 
be borne in mind constantly in handling this class of cables, consequently 
the lead on them is extra heavy. The use of jute and asphalt covering 
over the lead is strongly recommended on all this class of cables, inasmuch 
as their life is absolutely dependent upon that of the lead. Paper insulated 
cables cannot be furnished without the lead covering. 



PAPER INSULATED WIRES AND CABLES. 



175 



General Electric Company Paper Insulated and JLcad 
Covered Cable. 

I. Solid. 





$t" Insulation 


3 y Insulation 


J, <» 




Test Pressure, 4000 


Test Pressure, 6000 


.2 S fe 




Volts for 30 Minutes. 


Volts for 30 Minutes. 




Size. 

B. & S. and 

CM. 


ft 


.9 




t 08 




08 C 




o>© 

£8 


s 


A 


6$£ 


II 

5 


A 


£ * » 


10 


413 


•414 


493 


.477 


300 


8 


461 


.441 


A 


542 


.503 


1 


300 


6 


530 


.474 


A 


613 


.537 


A 


300 


5 


574 


.494 


A 


660 


.557 


A 


300 


4 


626 


.517 


A 


715 


.579 


A 


300 



II. Stranded. 



6 


558 


.496 


l 


645 


.559 


A 


250 


5 


605 


.518 


A 


694 


.581 


A 


250 


4 


662 


.544 


A 


754 


.607 


l 


250 


2 


814 


.604 


A 


1,068 


.698 


A 


250 


1 


1,072 


.679 


A 


1,184 


.742 


A 


250 


100000 


1,176 


.708 


A 


1,289 


.771 


A 


250 





1,199 


.718 


A 


1,315 


.781 


A 


250 


125000 


1,276 


.748 


A 


1,393 


.811 


A 


200 


00 


1,354 


.762 


A 


1,470 


.825 


A 


200 


150000 


1,431 


.782 


A 


1,547 


.845 


A 


200 


000 


1,536 


.813 


A 


1,655 


.876 


A 


200 


200000 


1,703 


.855 


A 


2,046 


.949 


A 


150 


0000 


1,758 


.871 


A 


2,106 


.965 


A 


150 


250000 


2,165 


.950 


A 


2,304 


1.012 


A 


150 


300000 


2,435 


1.009 


A 


2,574 


1.071 


A 


150 


350000 


2,660 


1.057 


A 


2,804 


1.119 


A 


125 


400000 


2,890 


1.103 


A 


3,041 


1.165 


A 


125 


500000 


3,929 


1.252 


i 


4,106 


1.315 


i 


125 


600000 


4,409 


1.330 


i 


4,598 


1.393 


1 

8 


125 


700000 


4,876 


1.402 


i 


5,067 


1.465 


i 


100 


750000 


5,106 


1.436 


i 


5,298 


1.499 


8 


100 


800000 


5,337 


1.468 


1 

¥ 


5,523 


1.531 


i 


100 


900000 


5,782 


1.531 


l 
8 


5,976 


1.594 


i 


100 


1000000 


6,213 


1.590 


i 


6,416 


1.653 


i 


100 


1250000 


7,293 


1.727 


i 


7,500 


1.790 


I 


100 


1500000 


8,329 


1.849 


8 


8,542 


1.912 


i 


75 


2000000 


10,355 


2.069 


i 


10,586 


2.132 


i 


50 



176 



PROPERTIES OF CONDUCTORS. 



General Electric Company Paper Insulated and Lead 
Covered Cable. 

I. Solid. 





Size. 
& S. and 
CM. 


3 y Insulation 
Test Pressure, 8000 
Volts for 30 Minutes. 


£?" Insulation 
T«st Pressure, 10,000 
Volts for 30 Minutes. 


1 m 

.a S S3 


B 


lid 


11 


Is 

t» _ 

0) C 


Si 




la 

^"0 








*g 


S.S 


S3 


00 


S.S 


3>S 


t-t w 




10 


576 


.539 


l 
T6~ 


669 


.602 


A 


400 




8 


632 


.565 


l 

T6~ 


875 


.659 


A 


400 




6 


707 


.599 


A 


960 


.693 


A 


400 




5 


753 


.619 


A 


1,011 


.713 


_5_ 
64 


400 




4 


963 


.672 


5 

64 


1,075 


.735 


_5_ 
64 


400 



II. Stranded. 



6 


737 


.621 


A 


999 


.715 


A 


400 


5 


943 


.674 


A 


1,056 


.737 


A 


400 


4 


1,012 


.700 


A 


1,124 


.763 


A 


400 


2 


1,182 


.760 


5 

64 


1,300 


.823 


5 

64 


350 


1 


1,300 


.804 


A 


1,420 


.867 


5 
64 


350 


100000 


1,407 


.833 


A 


1,529 


.896 


A 


350 





1,433 


.843 


5 
64 


1,555 


.906 


5 
64 


350 


125000 


1,513 


.873 


5 
64 


1,752 


.967 


3 
32 


350 


00 


1,593 


.887 


A 


1,949 


.981 


A 


300 


150000 


1,892 


.939 


A 


2,029 


1.001 


A 


300 


000 


2 006 


.970 


A 


2,147 


1.032 


A 


300 


200000 


2,187 


1.012 


A 


2,330 


1.074 


A 


250 


0000 


2,246 


1.028 


3 
32 


2,390 


1.090 


3 
32 


250 


250000 


2,451 


1.075 


A 


2,597 


1.137 


A 


250 


300000 


2,724 


1.134 


A 


3,470 


1.259 


1 
8 


250 


350000 


2,958 


1.182 


A 


3,715 


1.307 


ft 


200 


400000 


3,795 


1.290 


A 


3,980 


1.353 


ft 


200 


500000 


4,298 


1.377 


i 


4,488 


1.440 


J 


200 


600000 


4,793 


1.455 


i 


4,983 


1.518 


ft 


200 


700000 


5,269 


1.527 


J 


5,463 


1.590 


i 


150 


750000 


5,500 


1.561 


i 


5,702 


1.624 


i 


150 


800000 


5,721 


1.539 


1 
¥ 


5,931 


1.656 


J 


150 


900000 


6,189 


1.656 


ft 


6,390 


1.719 


ft 


150 


1000000 


6,631 


1.715 


J 


6,838 


1.778 


J 


125 


1250000 


7,715 


1.852 


ft 


7,943 


1.915 


ft 


100 


1500000 


8,776 


1.974 


ft 


9,001 


2.037 


ft 


. 100 


2000000 


10,834 


2.194 


ft 


11,066 


2.257 


ft 


100 



PAPER INSULATED WIRES AND CABLES. 



177 



General Electric Company Paper Insulated and Lead 
Covered Caole. 

I. Solid. 







aV Insulation. 
Test Pressure, 16,000 
Volts for 30 Minutes. 


§f" Insulation. 
Test Pressure, 22,000 
Volts for 30 Minutes. 


J, DB 

.2 g t- 
3 o:5- 


B. 


Size. 

&. S and 
CM. 






g3 


£2 

'So 


cj « a 

5^~ 


Is 

•a o> 


o^ 0> o 
S § & 




10 


1,157 


.820 


A 


1,770 


1.039 


'A 


600 




8 


1,223 


.846 


A 


1,846 


1.065 


A 


600 




6 


1,313 


.880 


A 


1,949 


1.099 


A 


600 




5 


1,369 


.899 


A 


2,013 


1.119 


A 


550 




4 


1,659 


.953 


A 


2,086 


1.141 


A 


550 



II. Stranded. 



6 


1,357 


.902 


A 


2,001 


1.121 


A 


500 


5 


1,639 


.955 


A 


2,068 


1.143 


A 


500 


4 


1,717 


.981 


A 


2,155 


1.169 


A 


500 


2 


1,917 


1.041 


A 


2,959 


1.292 


i 


500 


1 


2,052 


1.085 


A 


3,121 


1.336 


i 


500 


100000 


2,175 


1.114 


A 


3,267 


1.365 


8 


450 





2,204 


1.124 


A 


3,300 


1.375 


4 


450 


125000 


2,293 


1.154 


A 


3,404 


1.405 


J 


450 


00 


2,382 


1.168 


4 


3,508 


1.419 


1 
8 


450 


150000 


3,053 


1.251 


i 

8 


3,610 


1.439 


1 
8 


450 


000 


3,215 


1.282 


i 


3,755 


1.470 


1 


450 


200000 


3,400 


1.323 


i 


3,970 


1.512 


i 


400 


0000 


3,473 


1.340 


J 


4,046 


1.528 


1 
8 


400 


250000 


3,706 


1.387 


* 


4,293 


1.575 


1 
8. 


400 


300000 


4,023 


1.446 


1 

8 


4,611 


1.634 


i 


400 


350000 


4,293 


1.494 


ft 


4,888 


1.682 


i 


350 


400000 


4,559 


1.540 


1 
8 


5,168 


1.728 


i 


350 


500000 


5,088 


1.627 


1 

8 


5,707 


1.815 


I 


300 


600000 


5,594 


1.705 


ft 


6,228 


1.893 


i 


300 


700000 


6,087 


1.777 


ft 


6,740 


1.965 


i 


300 


750000 


6,331 


1.811 


ft 


6,983 


1.999 


i 


300 


800000 


6,555 


1.843 


1 
8 


7,224 


2.031 


i 


300 


900000 


7,040 


1.908 


ft 


7,706 


2.094 


i 


250 


1000000 


7,495 


1.965 


ft 


8171 


2.153 


i 


250 


1250000 


8,608 


2.102 


ft 


9,324 


2.290 


i 


200 


1500000 


9,702 


2.224 


1 
8 


10,424 


2.412 


i 


150 


2000000 


11,810 


2.443 


i 


12,579 


2.631 


i 


150 



178 



PROPERTIES OF CONDUCTORS. 



General Electric Company Three Conductor Paper 
Insulated Cables. 



Test Pressure, 3000 Volts for 
30 Minutes. 





o 
o . 

O n 


"8 


*** 03 

O o> 


Size. 


S 


.fl 


B. & S. and 


a.fl 


fel 


C^ 


C. M. 


■5"S 


2 3 


.2^ 






^ 


— v 




©Pt4 


Hh-3 




£ 


3 




8 


1388 


.864 


_5_ 
64 


6 


1874 


.979 


_3_ 

32 


5 


2072 


1.027 


3 
3"2 


4 


2270 


1.083 


A 


2 


2837 


1.213 


A 


1 


3405 


1.314 


A 


100000 


3635 


1.437 


A 





3864 


1.459 


A 


125000 


4142 


1.524 


A 


00 


4420 


1.553 


A 


150000 


4750 


1.595 


* 


000 


5081 


1.663 


A 


200000 


6300 


1.815 


* 


0000 


6700 


1.852 


1 



ft? O • 

fl^^ 
•J flu 

03 fl 

fl oS 



150 
125 
125 
125 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 



Test Pressure, 8000 Volts 
for 30 Minutes. 



.fl « 

.SPrg 

tv)l-H 



1,892 
2,190 
2,393 
2,597 
3.188 
3,583 
3,814 
4,045 
4,327 
4,610 
5,358 
6,106 
6,546 
6,978 



■g" 




■s 


O 4) 


fl) . 


03 'A 


^ 2 




Sfl 


S fl 

fl^ 

•2li 


a 


J2 V 


3 


hJ 


s 




1.029 


* 


1.114 


A 


1.162 


A 


1.218 


A 


1.345 


A 


1.441 


A 


1.504 


A 


1.525 


A 


1.591 


A 


1.622 


A 


1.663 


A 


1.795 


* 


1.876 


I 


1.919 


1 
8 



.2 fl 

Si . 

flgS 

■S-S8. 
Is 

2 fl 
fl «3 

200 
175 
175 
175 
150 
150 
150 
150 
150 
125 
125 
125 
125 
125 



Test Pressure, 15,000 Volts 
for 30 Minutes. 



Test Pressure, 26,000 Volts 
for 30 Minutes. 



8 

6 

5 

4 

2 

1 

100000 



125000 

00 

150000 

000 

200000 

0000 



2874 


1.424 


* 


3199 


1.508 


_3_ 
32 


3422 


1.557 


A 


3646 


1.608 


A 


4274 


1.740 


A 


4705 


1.837 


3 
3~2 


5407 


1.962 


1 

8 


6110 


1.984 


1 
t 


6433 


2.049 


* 


6755 


2.080 


* 


7134 


2.122 


1 

8 


7513 . 


2.190 


4 


7980 


2.298 


1 

8 


8446 


2.315 


J 



300 
300 
275 
275 
275 
275 
275 
275 
275 
250 
250 
250 
250 
250 



5,342 


2.017 


* 


5,742 


2 . 100 


* 


6,020 


2.150 


* 


6,299 


2.206 


4 


7,052 


2.335 


* 


7,561 


2.433 


* 


7,883 


2.495 


4 


8,144 


2.515 


* 


8,492 


2.580 


* 


8,841 


2.608 


i 


9,249 


2.653 


* 


9,657 


2.720 


* 


10,160 


2.809 


* 


10,663 


2.845 


i 



400 
400 
400 
400 
400 
350 
350 
350 
350 
350 
350 
350 
300 
300 



Thickness of insulation for 3000 volt class, sizes No. 2 and smaller, yV' 
paper on each conductor, T y paper over all ; sizes 0000 to No. 1 inclusive, 
fa" paper on each conductor, fa" paper over all. 

Thickness of insulation for 8000 volt class, all sizes, fa" paper on each 
conductor, fa" paper over all. 

Thickness of insulation for 15,000 volt class, all sizes, fa" paper on each 
conductor, fa" paper over all. 

Thickness of insulation for 26,000 volt class, all sizes, fa" paper on each 
conductor, fa" paper over alL 



PROPERTIES OF CONDUCTORS. 178a 

Varnished Cambric Cables. 

Special Finishes. 

The standard braided finish of varnished cambric cables is a weatherproof 
cotton braid. 

The following special finishes may be applied if desired: 

Asbestos Braid. — Generally applied over the regular cotton braid is filled 
with flameproof paint. It is especially recommended for interior wiring as a 
protection against the arcing of one cable affecting another. 

Asbestos braid adds about ^ to diameter of cable. 

Cotton Braid, Flameproof. — The standard braid may be treated with 
flameproof paint instead of being weatherproof ed, or one or more cotton 
braids may be applied, all being treated with flameproof paint. 

This style of finish is slightly more expensive than standard weatherproof 
but not as expensive as asbestos braided. 

Varnish Cambric cables leaded may have any of the special finishes described 
applied over the lead. 

Hoiking- and Test Pressures of Paper Insulated Lead 
Covered Cables. 

Factors by which to multiply working pressure to obtain proper test pres- 
sure for paper insulated lead covered cables. 

Test at Factory. 

For 5 mins., pressure = 2.5 X working pressure. 

For 30 mins., pressure = 2.0 X working pressure. 

For 60 mins., pressure = 1.6 X working pressure. 

Test After Installation by Manufacturer. 

For 5 mins., pressure = 2.0 X working pressure. 
For 30 mins., pressure = 1.6 X working pressure. 
For 60 mins., pressure = 1.3 X working pressure. 



CAMBRIC INSULATED WIRES AND CABLES. 



179 



Varnished Cambric Cables. Single Stranded Conductor — 
Leaded and Braided. 

For Working Pressures not Exceeding 1000 Volts. 





Thick. 


Thick. 


Diameter. 


Weight in Lbs. per 
1000 Feet. 


Size. 


Insulation 
in Inches. 


Lead in 
Inches. 






















Leaded. 


Braided. 


Leaded. 


Braided. 


6 


A 


A 


.40 




386 


151 


4 


A 


A 


.45 




490 


202 


2 


A 


A 


.54 


t 


725 


279 


1 


A 


A 


.61 


1 


880 


362 





A 


A 


.66 


J 


1015 


448 


00 


A 


A 


.70 


1120 


534 


000 


s 


A 


.75 


3 


1301 


642 


0,000 


A 


A 


.84 


o 


1690 


778 


250,000 


A 


A 


.95 


s 


2267 


1034 


300,000 


A 


A 


1.01 


s 


2520 


1220 


350,000 


3 3 2 


A 


1.06 


>> 


2780 


1409 


400,000 


32 


3 3 2 


1.11 


B 


2994 


1556 


500,000 


32 


3 3 2 


1.19 


1 


3473 


1893 


600,000 


B 7 ¥ 


3 S 2 


1.30 


3999 


2281 


700,000 


& 


A 


1.37 




4388 


2562 


750,000 


A 


A 


1.41 


4589 


2731 


800,000 


A 




1.44 


ft 


4794 


2901 


900,000 




32 
A 

3 3 2 


1.50 


< 


5241 


3245 


1,000,000 


B5 
B ? * 


1.56 




5656 


3589 


1,250,000 


^ 








1,500,000 


i 








1,750,000 


[ 




See 2000 volt class 




2,000,000 


) 









For Working Pressures not Exceeding 2000 Volts. 



6 
4 
2 
1 



00 

000 

0,000 

250,000 

300,000 

350,000 

400.000 

500,000 

600,000 

700,000 

750,000 

800,000 

900,000 

1,000,000 

1,250,000 

1,500,000 

1,750,000 

2,000.000 



32 
3 3 2 
3 3 2 

A 
A 

A 

i 

A 
A 
I 
i 
i 
I 
i 

i 

i 
i 
1 



A 



B* 
3 3 2 



* 



.47 

.52 

.61 

.65 

.69 

.74 

.82 

.87 

.98 

1.04 

1.09 

1.14 

1.22 

1.33 

1.41 

1.44 

1.47 

1.53 

1.59 

1.76 

1.92 

2.03 

2.14 



I 



1 

a 



a 



468 


180 


570 


248 


870 


352 


963 


426 


1082 


496 


1,239 


605 


1,502 


739 


1,846 


905 


2,329 


1063 


2,590 


1252 


2,845 


1440 


3,045 


1569 


3,539 


1924 


4,068 


2315 


4,455 


2597 


4,658 


2765 


4,903 


2938 


5,311 


3280 


5,766 


3632 


7,185 


4453 


8,700 


5297 


9,793 


6157 


10,835 


7010 



Specifications, diameters and weights for solid conductors same as above. 



180 



PROPERTIES OP CONDUCTORS. 



Varnished Cambric Cables. Single Stranded Conductor 
— beaded and Braided. 

For Working Pressures not Exceeding 3,000 Volts. 





Thick. 


Thick. 


Diameter. 


Weight in Lbs. per 
1000 Feet. 


Size. 


Insulation 
in Inches. 


Lead in 
Inches. 
























Leaded. 


Braided. 


Leaded. 


Braided. 


6 


& 


& 


.56 




565 


228 


4 


& 


A 


.64 




837 


301 


2 


& 


2 


.70 




961 


416 


1 


& 


.74 




1,128 


495 





& 


i 1 * 


.78 


T3 


1,417 


570 


00 


£ 


& 


.86 


T3 


1,597 


676 


000 


£ 


& 


.91 


o3 


1,786 


818 


0,000 


£ 


£ 


1.00 


M 


2,293 


994 


250,000 


& 


& 


1.05 


s 


2,495 


1124 


300,000 


& 


& 


1.11 


a> 


2,757 


1319 


350,000 


£ 


& 


1.15 


a 


3,019 


1510 


400,000 


& 


& 


1.20 


03 


3,176 


1639 


500,000 


& 


& 


1.29 


>> 


3,677 


1996 


600,000 


& 


A 


1.36 


"3 


4,145 


2359 


700,000 


& 


A 


1.44 


03 
S 

O 


4,532 


2639 


750,000 


& 


A 


1.47 


4,776 


2811 


800,000 


& 


& 


1.50 


4,982 


2986 


900,000 


& 


& 


1.60 


a 


5,772 


3330 


1,000,000 


£ 


& 


1.65 


Pi 


6,237 


3678 


1,250,000 


& 


i 

8 


1.82 


7,717 


4509 


1,500,000 


& 


l 


1.95 




8,802 


5354 


1,750,000 


& 


1 


2.06 




9,904 


6222 


2,000,000 


& 


i 


2.16 




10,944 


7072 



For Working Pressures not Exceeding 5,000 Volts. 



6 


t 3 b 


| 


.69 




871 


285 


4 


t 3 b 


.74 




999 


365 


2 


i 3 b 


s 


.83 




1,171 


483 


1 


t 3 b 


A 


.87 




1,509 


568 





t 3 b 


A 


.91 


T3 


1,608 


638 


00 


i 3 * 


A 


.95 


T3 


2,023 


757 


000 


x 5 * 


3 3 2 


1.04 


s 


2,242 


1004 


0,000 


& 


A 


1.09 


H-3 


2,525 


1087 


250,000 


i 3 s 


A 


1.14 


s 


2,695 


1219 


300,000 


A 


A 


1.20 


o> 


3,004 


1442 


350,000 


& 


A 


1.25 


a 


3,266 


1619 


400,000 


j\ 


A 


1.29 


o3 

QQ 


3,427 


1749 


500,000 


T 3 B 


A 


1.38 


>> 


3,942 


2116 


600,000 


1 3 B 


A 


1.46 


% 


4,415 


2485 


700,000 


& 


A 


1.53 


a 


4,802 


2771 


750,000 


I 3 B 


A 


1.60 


B 


5,388 


2946 


800,000 


IB 


A 


1.63 


*g 


5,647 


3123 


900,000 


IB 


i 


1.72 




6,499 


3473 


1,000,000 


1 3 B 


I 


1.78 


p. 

<3 


7,010 


3823 


1,250,000 


T 3 B 


| 


1.92 


8,067 


4664 


1,500,000 


TB 


| 


2.04 




9,168 


5532 


1,750,000 


r 3 s 


* 


2.15 




10,282 


6410 


2,000,000 


I 3 B 


i 


2.26 




11,318 


7259 



Specifications, diameters and weights for solid conductor approximately same 
s above. 



CAMBRIC INSULATED WIRES AND CABLES. 



181 



Varnished Camoric Cables. Single Stranded 
— JLeaded and Braided. 



Conductor 



For Working Pressures not Exceeding 7,000 Volts. 





Thick. 


Thick. 


Diameter. 


Weight in Lbs. per 
1000 Feet. 


Size. 


Insulation 
in Inches. 


Lead in 
Inches. 










Leaded. 


Braided. 


Leaded. 


Braided. 


6 


i 

4 


& 


.81 




1,112 


405 


4 


1 


s 5 * 


.89 




1,252 


497 


2 


| 


B 6 ? 


.95 




1,653 


622 


1 


1 


B 5 i 


.99 




1,802 


714 





1 


& 


1.06 


1 


2,183 


812 


00 


I 


& 


1.11 


2,364 


926 


000 


I 


3 3 2 


1.16 


£ 


2,594 


1085 


0,000 


1 

4 


3 3 2 


1.22 


£ 


2,898 


1283 


250,000 


| 


3?2 


1.27 


o3 


3,144 


1397 


300,000 


1 


a 3 ? 


1.32 


© 


3,363 


1610 


350,000 


J 


T?2 


1.37 


i 


3,642 


1816 


400,000 


i 


i 


1.42 


i 


3,888 


1996 


500,000 


i 


1.51 


>> 


4,327 


2331 


600,000 
700,000 


i 

1 




1.58 
1.69 


•a 

c3 


4,816 
5,633 


2714 
3022 


750,000 


1 


! 


1.75 


| 


5,848 


3197 


800,000 


1 


I 


1.78 


°£ 


6,546 


3379 


900,000 


i 


I 


1.85 


8 
p. 


7,004 


3746 


1,000,000 


| 


i 


1.90 


a 


7,514 


4111 


1,250,000 


i 


i 


2.04 


<J 


8,574 


4938 


1,500,000 


i 


§ 


2.17 




9,692 


5820 


1,750,000 


i 


I 


2.28 




10,828 


6719 


2,000,000 


i 


i 

8 


2.38 




11,890 


7599 



For Working Pressures 


not Exceeding 10,000 Volts. 




6 


5 


£ 


.97 




1583 


523 


4 


s 


& 


1.02 




1710 


624 


2 


T 6 B 


£ 


1.08 


•jd 

<D 


1923 


750 


1 


s 


3 3 2 


1.15 


T3 


2360 


851 





T6 


3 


1.19 


o 


2472 


930 


00 


6 


32 


1.23 


1-1 


2683 


1068 


000 


IS 


A 


1.29 


a 


2915 


1233 


0,000 


15 


A 


1.34 


<D 


3227 


1439 


250,000 


6 
16 


3 3 2 


1.39 


a 


3380 


1554 


300,000 


T 6 5 


3 3 2 


1.45 


3705 


1775 


350,000 


5 


A 


1.50 


>> 


3985 


1989 


400,000 


tb 


B 3 2 


1.54 


a> 


4557 


2115 


500,000 


5 


32 


1.63 


a 


5083 


2514 


600,000 


R 


& 


1.74 


5598 


2911 


700,000 


t\ 


I 


1.84 


8 


6471 


3213 


750,000 


i 5 b 


| 


1.88 


a 


6756 


3401 


800,000 




} 


1.91 




6984 


3581 


900,000 


i* 


§ 


1.97 


7460 


3966 


1,000,000 


IB 
I 5 B 


i 


2.03 




7967 


4331 



Specifications, diameters and weights for solid conductor approximately same 
as above. 



182 



PROPERTIES OF CONDUCTORS. 



Varnished Cambric Cables. Single Stranded Conductor 
— Leaded and Braided. 

For Working Pressures not Exceeding 13,000 Volts. 





Thick. 


Thick. 


Diameter. 


Weight in Lbs. per 
1000 Feet. 


Size. 


Insulation 
in Inches. 


Lead in 
Inches. 
























Leaded. 


Braided. 


Leaded. 


Braided. 


6 


t 


A 


1.09 




1724 


636 


4 


f 


A 


1.14 


| 


1978 


749 


2 


I 


3 

32 


1.23 


3 


2493 


878 


1 


f 


A 


1.27 


2668 


986 





t 


_3_ 

32 


1.31 


o3 


2766 


1048 


00 


3 
8 


A 


1.36 


§ 


2997 


1211 


000 


f 


A 


1.41 


i 


3241 


1383 


0,000 


1 


A 


1.47 




3661 


1596 


250,000 


f 


A 


1.52 


c3 


3711 


1715 


300,000 


f 


A 


1.57 


a 


4042 


1940 


350,000 


f 


A 


1.62 


o 


4333 


2159 


400,000 


f 


A 


1.70 


3 


4981 


2330 


500,000 


3 

8 


A 


1.79 


5469 


2701 



For Working Pressures not Exceeding 17,000 Volts. 



6 


A 


A 


1.25 




2193 


755 


4 


A 


A 


1.30 


© 


2488 


873 


2 


A 


A 


1.36 


03 

8 


2803 


1017 


1 


A 


A 


1.40 


h3 


2981 


1123 





7 


A 


1.44 


o3 


3054 


1161 


00 


A 


A 


1.48 


s 


3316 


1351 


000 


A 


A 


1.53 


o3 

OS 


3561 


1530 


0,000 


A 


A 


1.59 


"© 


3891 


1757 


250,000 


A 


A 


1.64 


o3 

J 


4046 


1872 


300,000 


A 


A 


1.73 


4793 


2106 


350,000 


A 


A 


1.78 


g 


5102 


2334 


400,000 


A 


1 
8 


1.86 




5806 


2548 


500,000 


7 


1 

8 


1.94 


6332 


2884 



Specifications, diameters and weights for solid conductor approximately same 
as above. 



CAMBRIC INSULATED WIRES AND CABLES. 



183 



Varnished Cambric Insulated Cables. — Single Conductor. 

Working Pressure, 10,000 Volts or Less. 
Test Pressure, 25,000 Volts. 



Size. 

B. & S. and 

CM. 


Thick. 
Ins. in 
Inches. 


Thick. 
Lead in 
Inches. 


Dia. in 
Inches. 


Braided. 

Weight in 

Lbs. per 

1000 ft. 


Leaded. 
Weight in 
Lbs. per 

1000 ft. 


6 Sol. 


i 


A 


.80 


424 


1063 


4 Sol. 


1 


A 


.84 


498 


1176 


6 St. 


i 


A 


.82 


441 


1102 


4 St. 


i 


A 


.87 


521 


1227 


2 St. 


J 


A 


.96 


712 


1651 


1 St. 


i 


A 


1.04 


793 


1925 


1/0 St. 


1 


A 


1.08 


891 


2182 


2/0 St. 


i 


A 


1.12 


1009 


2365 


3/0 St. 


1 


A 


1,17 


1150 


2580 


4/0 St. 


i 


A 


1.23 


1327 


2839 


250,000 


1 


A 


1.28 


1483 


3058 


300,000 


i 


A 


1.38 


1707 


3353 


400,000 


1 


A 


1.48 


2087 


4031 


500,000 


i 


A 


1.57 


2467 


4709 


750,000 


tt 


A 


1.80 


3458 


6470 


1,000,000 


* 


1.96 


4386 


7688 



Duplex cables larger than 250,000 Cm. are difficult to handle and there- 
fore are not recommended. 

The fourth column — Dia. in Inches — is the over -all diameter of the 
finished cable and is approximately the same for either braided or leaded. 



184 



PROPERTIES OF CONDUCTORS. 



Varnished Cambric Insulated Cables. — Single Conductor. 

Working Pressure, 15,000 Volts or Less. 
Test Pressure, 33,000 Volts. 











Braided. 


Leaded. 


Size. 
B. &. S. and 


Thick. 
Ins. in 


Thick. 
Lead in 


Dia. in 


Weight in 


Weight in 


C. M. 


Inches. 


Inches. 


Inches. 


Lbs. per 
1000 ft. 


Lbs. per 
1000 ft. 


6 Sol. 


a 


A 


1.05 


660 


1939 


4 Sol. 


H 


A 


1.10 


767 


2084 


6 St. 


H 


A 


1.08 


705 


1994 


4 St. 


H 


A 


1.12 


797 


2153 


2 St. 


1 1 
3 2 


A 


1.18 


927 


2373 


ISt. 


1 


A 


1.29 


1110 


2693 


1/0 St. 


1 


A 


1.33 


1225 


2860 


2/0 St. 


1 


A 


1.37 


1360 


3051 


3/0 St. 


t 


3 

32 


1.42 


1533 


3288 


4/0 St. 


t 


A 


1.48 


1732 


3562 


250,000 


f 


A 


1.53 


1901 


3795 


300,000 


t 


7 
FT 


1.63 


2130 


4487 


400,000 


i 


J 


1.73 


2530 


5246 


500,000 


i 


i 


1.82 


2930 


6006 


750,000 


If 


I 


2.05 


3998 


7468 


1,000,000 


a 


i 


2.23 


5005 


8835 



Duplex cables larger than 250,000 Cm. are difficult to handle and there- 
fore are not recommended. 

The fourth column — Dia. in Inches — is the over-all diameter of the 
finished cable and is approximately the same for either braided or leaded. 



CAMBRIC INSULATED WIRES AND CABLES. 185 



Varnished Cambric Cables. Triple Stranded Conductor 
— Leaded and Braided. 

For Working Pressures not Exceeding 1,000 Volts. 





Thick. 


Thick. 


Diameter. 


Weight in Lbs. per 
100 Feet. 


Size. 


Insulation 
in Inches. 


Lead in 
Inches. 
























Leaded. 


Braided. 


Leaded. 


Braided. 


6 
4 


l l 

T6~ 64 

i l 


A 
A 

5 

64 

A 


.824 
.959 


i 


1,245 
1,820 


538 
760 


2 

1 


16 64 

A-A 

64 64 

64~64 
5 1_ 

64 64 
5 1 

64 64 

64 64 


1.085 
1.279 




2,290 
3,066 


1089 
1384 




00 

000 

0,000 

250,000 


A 
A 

A 

A 


1.357 
1.456 
1.566 
1.723 
1.891 


m 
o3 
O 

1 


3,446 
3,933 
4,528 
5,642 
6,470 


1660 
2003 
2416 
2955 
3537 


300,000 
350,000 
400,000 
500,000 


_3 1_ 

32 64 
3 1 
32 64 

J- 1 
W2 64 

32 64 


A 

l 
8 
1 
8 
1 
8 


2.023 
2.150 
2.253 
2.438 


a 
•a 

o 

u 
Q* 

a 
< 


7,296 
8,595 
9,347 
10,870 


4155 
4770 

5288 
6483 


For ' 


Forking '. 


Pressures 


not Exci 


:eding 3,0 


00 Volts. 




6 
4 

2 


5 1 


5 


1.016 




1,803 


692 


64 16 

A _ A 


64 

A 

3 
32 


1.120 
1.277 


T3 

-8 


2,159 
2,955 


930 
1273 


1 


64" 1~6" 


A 


1.363 


h5 


3,290 


1505 





64~ — 16" 


A 


1.451 


cS 


3,725 


1795 


00 


64 — T6~ 


A 


1.550 


a 


4,206 


2139 


000 


64 "~ T6~ 


A 


1.691 


g 


5,184 


2573 


0,000 


64~~16 


A 


1.815 


>> 


5,928 


3115 


250,000 


32~T6~ 


7 
64 


1.984 




6,805 


3704 


300,000 


A~T6" 


1 

8 


2.134 


8,169 


4344 


350,000 


3~2~1T 


1 
I 


2.243 


2 


8,986 


4973 


400,000 


3%~16~ 


1 
8 


2.346 


<5 


9,692 


5492 


500,000 


ft-A 


1 

8 


2.531 




11,288 


6713 



Note. — Under Thickness Insulation: The first fraction is thickness of insu- 
lation on each conductor; the second fraction is thickness of insulation over all. 



186 



PROPERTIES OF CONDUCTORS. 



Varnished Cambric Cables. Triple Stranded 
— Leaded and Braided. 



Conductor 



For Working Pressures 


not Exceeding 5,000 Volts. 






Thick. 


Thick. 


Diameter. 


Weight in Lbs. per 
1000 Feet. 


Size. 


Insulation 
in Inches. 


Lead in 
Inches. 
























Leaded. 


Braided. 


Leaded. 


Braided. 


6 


32"~3~2 


A 


1.15 




2,092 


835 


4 


32~ 3~2" 


A 


1.28 


o 

"d 


2,765 


1083 


2 


3lJ~"32 


A 


1.41 


8 


3,302 


1444 


1 


32~32 


A 


1.50 


h5 

s 


3,682 


■ 1686 





A~A 


A 


1.58 


4,084 


1982 


00 


32 - 32 


A 


1.71 


a 


4,989 


2338 


000 


32"~ 32 


A 


1.82 


3 


5,640 


2790 


0,000 


J- J~ 
32 32 


A 


1.95 


>> 


6,356 


3342 


250,000 


3 3 
32 32 


1 
8 


2.08 


7,517 


3835 


300,000 


32 32 


1 
8 


2.20 


a 


8,398 


4476 


350,000 


3~2~"~ 32 


1 

8 


2.31 


| 


9,267 


5113 


400,000 


32~32 


1 
8 


2.41 




9,978 


5641 


500,000 


32~32 


1 
8 


2.60 


11,533 


6866 



For Working Pressures not Exceeding 7,000 Volts. 



6 


8 8 


A 


1.38 




2,909 


1083 


4 


i-i 


A 


1.48 




3,317 


1352 


2 


hi 


A 


1.61 


t3 


3,867 


1733 


1 


l l 
8 8 


A 


1.69 


h3 


4,268 


1991 





1 1 


A 


1.81 


3 


5,115 


2302 


00 


1 1 

8~8 


A 


1.91 


a 


5,651 


2673 


000 


i-i 


7 


2.02 


02 


6,280 


3139 


0,000 


i i 

8 8 


1 
8 


2.18 


j>> 


7,585 


3713 


250,000 


1 1 

8 8 


1 
8 


2.28 


1 


8,259 


4200 


300,000 


1 1 

8 8 


1 
8 


2.39 


a 

•a 

o 


9,183 


4892 


350,000 


1 1 

8 8 


1 
8 


2.50 


10,075 


5550 


400,000 


H 


1 
8 


2.61 


a 


10,800 


6086 


500,000 


1 1 

8 8 


1 
8 


2.79 


<< 


12,392 


7348 



Note. — Under Thickness Insulation: The first fraction is thickness of insula- 
tion on each conductor; the second fraction is thickness of insulation over all. 



CAMBRIC INSULATED WIRES AND CABLES. 



187 



Varnished Cambric Cables. Triple Stranded Conductor 
— Steaded and Braided. 



For Working Pressures not Exceeding 10,000 Volts. 



Size. 


Thick. 
Insulation 
in Inches. 


Thick. 
Lead in 
Inches. 


Diameter. 


Weight in Lbs. per 
1000 Feet. 




Leaded. 


Braided. 


Leaded. 


Braided. 


6 

4 

2 

1 



00 

000 

0,000 

250,000 

300,000 

350,000 

400,000 

500,000 


32"~32~ 
5 5 
32 32 

3~2~~32" 

3%~A 

32 32 

32~~32 

_5 5_ 

32 32 

32 ~ 32 

T2~ 32" 

32~3"2 
5 5 

32 32 
5 5 

32 32 

32~T2 


i 
i 
1 

i 
i 
i 
i 


1.57 
1.68 
1.80 
1.92 
2.01 
2.11 
2.25 
2.37 
2.47 
2.59 
2.70 
2.81 
2.99 


T3 

73 

c3 
O 

h3 

03 
C3 

<x> 

a 

o3 

03 
>> 

s 

o3 
J 

2 
a 
p. 


3,480 

3,992 

4,480 

5,309 

5,797 

6,336 

7,539 

8,373 

9,083 

10,010 

10,883 

11,660 

13,290 


1378 
1661 
2065 
2331 
2656 
3031 
3526 
4127 
4654 
5343 
6023 
6569 
7868 



187a cambric insulated wires and cables. 



Varnished Cambric Cables. Triple Stranded Conductor 
— Leaded and Braided. 

For Working Pressures not Exceeding 13,000 Volts. 





Thick. 


Thick. 


Diameter. 


Weight in Lbs. per 
1000 Feet. 


Size. 


Insulation 
in Inches. 


Lead in 
Inches. 
























Leaded. 


Braided. 


Leaded. 


Braided. 


6 


A-A 


3 
32 


1.77 




4,103 


1720 


4 


A-A 


A 


1.87 


<v 


4,542 


2019 


2 


A-A 


A 


2.03 


Oj 

o 


5,623 


2441 


1 


A~lV 


A 


2.12 


*1 


6,019 


2714 





A-A 


i 


2.23 


c3 


7,070 


3057 


00 


_3 3 

i6 rs 


i 


2.33 


s 


7,660 


3460 


000 


_3__ 3 
16 16 


I 


2.44 


3 
EG 


8,350 


3963 


0,000 


_3 3_ 

16 16 


i 


2.57 


>> 


9,199 


4582 


250,000 


_3 3_ 

16 16 


i 


2.67 


+3 


9,933 


5128 


300,000 


A-A 


i 


2.79 


1 


10,884 


5840 


350,000 


A-A 


i 


2.90 


O 


11,779 


6541 


400,000 


16 16 


i 


3.00 


a 
a 


12,511 


7089 


500,000 


_3 3 

16 TG 


i 


3.18 . 


< 


14,202 


8402 



For Working Pressures not Exceeding 17,000 Volts. 



6 


7 7 
32 32 


3 
32 


1.97 


*6 

0> 


4,784 


2123 


4 


JL_JL 
32 32 


A 


2.10 


03 


5,724 


2419 


2 


32 _ 32 


7 
64 


2.23 


Hi 


6,381 


2877 


1 


32~32 


1 
8 


2.34 


I 


7,364 


3164 





32~32 


1 
8 


2.43 




7,906 


3519 


00 


W2TTZ 


1 
8 


2.53 


c3 

CO 


8,459 


3884 


000 


7 7 
32 32 


1 
8 


2.64 


£ 


9,218 


4454 


0,000 


32~"~ 32" 


1 
8 


2.77 


-M 

d 


10,091 


5092 


250,000 


7 7 
32 32 


1 
8 


2.88 


a 


10,847 


5664 


300,000 


32 32 


1 
8 


2.99 




11,802 


6380 


350,000 


32~32 


1 
8 


3.10 


a 
a 
< 


12,697 


7086 



Note. — Under Thickness Insulation: The first fraction is thickness of 
insulation on each conductor; the second fraction is thickness of insulation 
over all. 



ENAMELED WIRE. 



187b 



Enameled IFire. 





Diameter in Inches. 


Comparative Weight per 1000 
Feet in Pounds. 


Size 








B. &S. 












Bare. 


Over Enamel. 


Single Cotton- 
Covered. 


Enamel. 


14 


.0640 


.0670 


12.684 


12.684 


15 


.0570 


.0600 


10.082 


10.053 


16 


.0510 


.0535 


8.012 


7.973 


17 


.0450 


.0475 


6.375 


6.322 


18 


.0400 


.0425 


5.081 


5.009 


19 


.0360 


.0380 


4.043 


3.966 


20 


.0320 


.0340 


3.218 


3.136 


21 


.0280 


.0305 


2.569 


2.475 


22 


.0250 


.0275 


2.055 


1.970 


23 


.0230 


.0250 


1.630 


1.555 


24 


.0200 


.0220 


1.297 


1.232 


25 


.0180 


.0200 


1.036 


.980 


26 


.0160 


.0175 


.828 


.777 


27 


.0140 


.0155 


.661 


.616 


28 


.0126 


.0140 


.524 


.485 


29 


.0110 


.0123 


.421 


.384 


30 


.0100 


.0113 


.336 


.303 


31 


.0090 


.0102 


.271 


.242 


32 


.0080 


.0092 


.215 


.192 


33 


.0070 


.0082 


.174 


.152 


34 


.0063 


.0075 


.141 


.121 


35 


.0056 


.0063 


.120 


.101 


36 


.0050 


.0056 


.099 


.081 


37 


.0045 


.0051 


.090 


.061 


38 


.0040 


.0046 


.080 


.0507 


40 


.0031 


.0037 


.060 


.0304 



188 



PROPERTIES OF CONDUCTORS. 



TELEPHONE CABLE!. 
JLead Sheathed for Underground or Aerial Use. 

The insulation of these cables is dry paper. The following specifications 
have been adopted by the larger telephone companies and, therefore, may 
be considered standard. 

Cable Conductor. No. 19 B. and S. G., 98% conductivity, insulated 
with one or two paper tapes; conductor twisted in pairs; one of the pairs 
to have a distinctive colored paper for marker; length of twist not to exceed 
3". Pairs to be laid up in reverse layers; insulation to be unsaturated ex- 
cept two feet from each end to prevent moisture from entering. The lead 
sheath to have an alloy of 2\ to 3^% of tin; thickness of sheath xV for 
fifty pair of cables, &" for one hundred pair of cables, and £" for larger 
sizes. Insulation resistance to be at least 100 megohms per mile after the 
cable is laid and spliced. Electrostatic capacity no greater than .054 with 
a maximum of .060 microfarads per mile. 

The aerial cables for telephone companies usually follow the same speci- 
fications as those for underground use, being purchased with the ultimate 
intention of being put underground. Cables that are to remain overhead 
indefinitely are usually made with a lighter sheathing of lead than that 
specified for underground work. 



Number Pairs. 


Outside Diameters. 
Inches. 


Weights 1000 feet. 
Pounds. 


1 


& 


214 


2 


I 


302 


3 


515 


4 


f 


629 


5 


747 


6 


|1 


877 


7 


T$ 


912 


10 


t! 


1,214 


12 


H 


1,373 


15 


l 


1,566 


18 


l& 


1,758 


20 
25 


li 6 * 


1,940 
2,332 


30 


l& 


2,748 


35 


l* 


2,985 


40 


U\ 


3,176 


45 


if 


3,365 


50 


if 


3,678 


55 


m 


3,867 


60 


u 


4,055 


65 


m 


4,241 


70 


2 


4,430 


80 


2* 


4,804 


90 


21 


5,180 


100 


i 


5,505 



SUBMARINE CABLES. 



189 



TELEGRAPH < VBJLl]*. 

Lead Sheathed for Underg-round or Taped and Braided 
for Aerial Use. 

The insulation of these cables is made of a compound containing not 
less than thirty per cent pure Para rubber. These specifications may be 
considered standard, being used by the principal telegraph companies. 

Rubber Insulated Aerial Teleg-rapli Cable. 



Gauge B. & S. 


No. of Conductors. 


Outside Diameter. 


Weight per 1,000 ft. 


14 
14 
14 


7 
10 
19 


.3." 

IF 


425 lbs. 
500 lbs. 
890 lbs. 



Conductors No. 14 B. and S. insulated to diameter of 6-32", cabled 
together and covered with a rubber tape, one layer of tarred jute, a rubber 
tape, and a heavy cotton braid saturated with waterproof compound. 



SUBMARINE CABLE§. 

These cables are insulated with a rubber compound containing not less 
than thirty per cent (30% ) of pure Para rubber. 

These specifications have been adopted by the various telegraph com- 
panies and the United States Government for general use. 



No. of 
Conduc- 
tors. 


Gauge of Con- 
ductors. 


No. of 
Armor 
Wires. 


Gauge of Armor 
Wires. 


Outside 
Diameter. 


Weight 

per 1,000 

feet. 


1 
2 
3 

4 
5 
6 

7 
10 


14 B. & S. 
14 B. & S. 
14 B. & S. 

14 B. & S. 
14 B. & S. 
14 B. & S. 

14 B. & S. 
14 B. & S. 


12 
16 
14 

16 
19 
21 

21 
22 


8 B. W. G. 
8 B. W. G. 
6 B. W. G. 

6 B. W. G. 
6 B. W. G. 
6 B. W. G. 

6 B. W. G. 
4 B. W. G. 


1" 

w 

U" 

ItV 

if" 
H" 

1J" 

11" 


1150 
1675 
2400 

2750 
3100 
350C 

3600 
4600 



Conductors built up of 7 No. 21 B. & S. copper wires, heavily tinned. Each 
conductor insulated with ^" Rubber and Taped. 

The above specifications refer only to river and harbor cables. Ocean 
cables are of an entirely different character, and consist of Shore End, In- 
termediate and Deep Sea Types. 



190 



PROPERTIES OF CONDUCTORS. 



•Joints in Rubber Insulated Cables. 

Preparation of Ivnds. — Remove the outside protecting braid or 
tape, and bare the conductor of its rubber insulation for two or three inches 
back from the end. Clean the metal carefully by scraping with a knife 
or with sandpaper. 

Metal Joint. — If solid conductor, scarf the ends with a file so as to 
give a good long contact surface for soldering. If conductor is stranded, 
carefully spread apart the strands, cutting out the centers so conductors 
can be butted together, the loose ends interlacing as in Fig. 1, and bind 
wires down tight as in Fig. 2, with gas or other- pliers. Solder carefully, 




Fig. 1. 



Fig. 2. 



using no acid; resin is the best, although jointers often use a spermaceti 
candle as being handy to use and easy to procure. Large cables are easiest 
soldered by dipping the joint into a pot of molten solder, or by pouring the 
molten metal over the joint. 

The insulation of all kinds of joints is done in the same manner, the only 
difference in the joint being the manner in which the conductors are joined 
together. Following are some of the styles of joining conductors, which 
are afterward insulated with rubber, and covered with lead when necessary. 






Fig. 3. 



Fig. 4. 



Figs. 5, 6, 



Seeley's Cable Connectors. — The cuts below show a style of cop- 
per connectors very handy in joining cables. They are copper tinned over, 
and after putting in place can be "sweated" on with solder; when dry can 
be insulated as previously described. 




Figs. 7, 8. 



JOINTS IN CABLES. 191 

Insulating* the Joint. — Jointers must have absolutely dry and 
clean hands, and all tools must be kept in the best possible condition of 
cleanliness. Clean the joint carefully of all flux and solder ; scarf back the 
rubber insulation like a lead-pencil for an inch or more with a sharp knife. 

Carefully wind the joint with three layers of pure unvulcanized rubber, 
taking care not to touch the strip with the hands any more than neces- 
sary ; over this wind red rubber strip ready for vulcanizing. Lap the tape 
upon the taper ends of the insulation, and make the covering of the same 
diameter as the rubber insulation on the conductor, winding even and 
round. Cover the rubber strip with two or three layers of rubber-saturated 
tape. 

Lead covering-. — If the insulation is covered and protected by lead, a 
loose sleeve is slipped over one end before jointing, and slipped back over 
the joint when the insulation is finished, a plumber's wiped joint being 
made at the ends. 




Fig. 9. 

Joints in Waring- Cables. —This cable is covered with cotton, 
thoroughly impregnated with a composition of hydro-carbon oils applied at 
high temperature, the whole being covered with lead to protect the insula- 
tion. The insulating properties of this covering are very high if the lead is 
kept intact. 

Metal joints are made as usual, and a textile tape may be used for cover- 
ing the bare copper. A large lead-sleeve is then drawn over the joint, 
and wiped onto the lead covering at either end ; then the interior space is 
filled with a compound similar to that with which the insulation is im- 
pregnated. 

Joints in Paper Insulated Cables. — This cable is covered or 
insulated with narrow strips of thin manila paper wound on spirally, after 
which the whole is put into an oven and thoroughly dried, then plunged 
into a hot bath of resin oil, which thoroughly impregnates the paper. This 
insulation is not the highest in measurement, but the electrostatic capacity 
is low and the breakdown properties high. When used for telephone pur- 
poses the paper is left dry, and is wound on the conductor very loosely, thus 
leaving large air spaces and giving very low electrostatic capacity. 

Joints are made as in the Waring cable by covering the conductor with 
paper tape of the same kind as the insulation, then pulling over the lead 
sleeve, which is finally filled with paraffine wax. 

Dossert Joint. — Dossert & Company, New York City, make a 
mechanical joint for solid or stranded conductor which has great mechanical 
strength and an electrical conductance in excess of that of the cable. The 
joint illustrated in Fig. 10 consists of a nipple (A), two compression sleeves 
or bushings (B) and two compression nuts (C). 

As shown in Fig. 11, the compression sleeves are split lengthwise and 
tapered at both ends. The tapered ends of the sleeve fit into correspond- 
ingly tapered parts of the nipple and nut. When the nut is screwed upon 
the nipple the action of the taper causes the compression sleeve to decrease 
in diameter and grip the strands tightly together, thereby getting good elec- 
trical contact. 

To make a splice with this connector cut the insulation from the cables to 
a distance equal to half the length of the connector, slip the cable into the 
connector and screw the nuts up tightly on the nipple. 



192 



PROPERTIES OF CONDUCTORS. 




DETAIL TMO-W/iY TOIN~r 



m 




■ e 




Fig. 10. 




LONGWUOlrfAL 
SECTION TO I NT 

TNO MY" SPL ICE 
COMPUTE 



Fig. 11. 

Lugs, 3-Ways, Y's, Reducers, Elbows and many other types of connectors 
are made with this principle for making the electrical connections and can 
be used for connections on switchboards, bus bars, transformers, meters, 
oil switches, storage batteries, electric smelting furnaces and the like. 

A special application of this joint is the cable tap as shown in Figs. 12 
and 13. It consists of a hook (A), cover (B), jam nut C), compression 
sleeve (D) and compression nut (E). The hook is machined to fit the main 
cable while its shank is drilled and threaded to form the nipple of a standard 
Dossert joint for size of branch required. The branch is secured to the 



DETAIL CABLE TAP 




Brewh 
CONNECTION COn PLC TE 



Figs. 12 and 13. 



connector by inserting it in the sleeve (D) and screwing nut (E) up tight. 
Connection is made to main by placing the hook part of the connector over 
the main cable, inserting the cover (B) and screwing up the jam nut (C). 

For overhead work where the cables are subjected to considerable tensile 
strain the Company makes another type of joint. 



JOINTS IN COPPER WIRES. 



193 



Jointing- Cwutta-JPerclia Covered IFire. 

First remove the gutta-percha for about two inches from the ends of the 
wires which are to be jointed. Fig. 14. 



Fig. 14. 

Next cross the wires midway from the gutta-percha, and grasp with the 
pliers. Fig. 15. 




Fig. 15. 

Then twist the wires, the overlapping right-hand wire first, and then, 
reversing the grip of the pliers, twist the left-hand wire over the right. Cut 
off the superfluous ends of the wires and solder the twist, leaving it as shown 
in Fig. 16. 



Fig. 16. 

Next warm up the gutta-percha for about two inches on each side of the 
twist. Then, first draw down the insulation from one side, half way over 



Fig. 17. 
the twisted wires, Fig. 17, and then from the other side in the same way, Fig. 

18. 



Fig. 18. 

Then tool the raised end down evenly over the under half with a heated 
Iron. Then warm up the whole and work the "drawdown" with the thumb 
and forefinger until it resembles Fig. 19. Now allow the joint to cool andfset. 



Fig. 19. 



Next roughen the drawdown with a knife, and place over it a thin coating 
of Chatterton's compound for one inch, in the center of the drawdown, 
which is also allowed to set. 

Next cut a thick strip of gutta-percha, about an inch wide and six inches 



194 



PROPERTIES OF CONDUCTORS. 



long, and wrap this, after it has been well warmed by the lamp, evenly over 
the center of the drawdown. Fig. 20. 



Fig. 20. 

The strip is then worked in each direction by the thumb and forefinger 
over the drawdown until it extends about 2 inches from center of draw- 
down. Then tool over carefully where the new insulation joins the old, 
after which the joint should be again warmed up and worked with the fore- 
finger and thumb as before. Then wet and soap the hand, and smooth and 
round out the joint as shown in Fig. 21. 



Fig. 21. 

Between, and at every operation, the utmost care must be exercised to 
remove every particle of foreign matter, resin, etc. 

Note. Chatterton's compound consists of 1 part by weight Stockholm tar; 
1 part resin; 3 parts Gutta-percha. 



AMJUmTNUXK WIRE. 
Physical Constants of Commercially (99%) Pare Aluminum. 



Per cent Conductivity (Copper 100) 

Specific Gravity 

Pounds in 1 cubic foot 

Pounds in 1 cubic inch 

Pounds per mile per circular mil 

Ultimate strength, r— 

sq. m. 

Modulus of Elasticity, . '— r — 

in. X sq. in. 

Coefficient of Linear Expansion per ° C 

Coefficient of Linear Expansion per °F 

Melting Point in °C 

Melting Point in °F 

Specific Heat (watt-seconds to heat 1 lb. 1° C.) 

Thermal Conductivity (watts through cu. in. temperature grad- 
ient 1° C.) 

Resistance 

Microhms of centimeter cube at 0° C , 

Microhms of inch cube at 0° C , 

Ohms per mile-foot at 0° C , 

Ohms per mil-foot at 20° C 

Ohms per mile at 0° C 

Ohms per mile at 20° C 

Pounds per mile-ohm at 0° C 

Pounds per mile-ohm at 20° C 

Temperature coefficient per ° C 

Temperature coefficient per ° F 



62 

2.68 

167 

.0967 

.00481 

26.000 

9,000,000 

.0000231 
.0000128 

625 
1157 

402 

36.5 



2.571 

1.012 

15.47 

16.70 

81,700 

cir. mils 

88,200 

cir. mils 

393 

424 

.004 

.0022 



ALUMINUM WIRE. 



195 



Aluminum and Copper Compared. 

Aluminum wire of 62% conductivity is the generally accepted standard. 

Aluminum of 62% conductivity, bought at 2.13 times the price of cop- 
per per pound, will give the same length and conductivity for the same 
expenditure. 



Comparative Cost of Aluminum of G2% Conductivity and 
Copper for Equal JLeng-tli and Conductivity. 



Cost per Pound 


Cost per ] 


Pound 


of Copper of 100 % Conductivity. 


of Aluminum of 62% Conductivity. 


14 cents 


28.8 cents 


15 * 




32.0 


" 


16 ' 




34.1 


" 


17 ' 




36.2 


•■ 


18 4 




38.4 


" 


19 ' 




40.5 


«• 


20 * 




42.6 


•• 


21 ' 




44.7 


" 


22 • 




46.8 


«« 


23 * 




49.0 


■■ 


24 ' 




51.1 


'• 


25 - 


53.2 


i« 



Comparison of Copper and Aluminum of Various Conduc- 
tivities for Initial Length and Conductivity. 



Metal. 


Conduc- 
tivity. 


Cross 
Section. 


Weight. 


Breaking 
Weight.* 


Price 
per lb. 


Copper .... 


100 


100 


100.0 


100 


100 


Aluminum 






54 


180 


54.0 


85.1 


185 










55 


176 


53.0 


83.5 


189 












56 


173 


52.0 


82.0 


192 












57 


170 


51.1 


80.6 


196 












58 


167 


50.2 


79.2 


199 












59 


164 


49.4 


77.9 


203 












60 


162 


48.6 


76.6 


206 












61 


159 


47.8 


75.3 


210 












62 


157 


47.0 


74.1 


213 










63 


154 


46.3 


72.9 


216 



* Breaking weights (pounds to break wire of equal conductivity) are cal- 
culated on the assumption of an ultimate strength of 55,000 pounds per 
square inch for copper and 26,000 pounds per square inch for aluminum. 



196 



PROPERTIES OF CONDUCTORS. 



Table of Iteciatances of Solid Aluminum Wire 62% 
Conductivity .* 

Pittsburg Reduction Co. 



Conductivity 62 


in., the Matthiessen Standard Scale 


. Pure aluminum 






weighs 167.111 pounds per cubic foot. 


¥ 




Resistances at 70° ] 


F. 


Log d 2 . 






R 
Ohms per 
1000 Feet, 


Ohms 
per Mile. 


Feet 
per Ohm. 


Ohms per lb. 


Logfl. 


0000 


.07904 


.41730 


12652. 


.00040985 


5.325516 


3 .897847 


000 


.09966 


.52623 


10034. 


.00065102 


5.224808 


3 .998521 


00 


.12569 


.66362 


7956. 


.0010364 


5.124102 


T . 099301 





.15849 


.83684 


6310. 


.0016479 


5.023394 


r . 200002 


1 


.19982 


1.0552 


5005. 


.0026194 


4.922688 


T . 300639 


2 


.25200 


1.3305 


3968. 


.0041656 


4.821980 


T . 401401 


3 


.31778 


1.6779 


3147. 


.0066250 


4.721274 


j. 502127 


4 


.40067 


2.1156 


2496. 


.010531 


4.620566 


1.602787 


5 


.50526 


2.6679 


1975. 


.016749 


4.519860 


T . 703515 


6 


.63720 


3.3687 


1569. 


.026628 


4.419152 


T . 804276 


7 


.80350 


4.2425 


1245. 


.042335 


4.318446 


T . 904986 


8 


1.0131 


5.3498 


987.0 


.067318 


4.217738 


0.005652 


9 


1.2773 


6.7442 


783.0 


.10710 


4.117030 


0.106293 


10 


1.6111 


8.5065 


620.8 


.17028 


4.016324 


0.207122 


11 


2.0312 


10.723 


492.4 


.27061 


3.915616 


0.307753 


12 


2.5615 


13.525 


390.5 


.43040 


3.814910 


0.408494 


13 


3.2300 


17.055 


309.6 


.68437 


3.714202 


0.509203 


14 


4.0724 


21.502 


245.6 


1.0877 


3.613496 


0.609850 


15 


5.1354 


27.114 


194.8 


1.7308 


3.513788 


0.710574 


16 


6.4755 


34.190 


154.4 


2.7505 


3.412082 


0.811273 


17 


8.1670 


43.124 


122.50 


4.3746 


3.311374 


0.912063 


18 


10.300 


54.388 


97.15 


6.9590 


3.210668 


1.012837 


19 


12.985 


68.564 


77.06 


11.070 


3.109960 


1.113442 


20 


16.381 


86.500 


61.03 


17.595 


3.009254 


1.214340 


21 


20.649 


109.02 


48.44 


27.971 


2.908546 


1.314899 


22 


26.025 


137.42 


38.4 


44.450 


2.807838 


1.415391 


23 


32.830 


173.35 


30.45 


70.700 


2.707132 


1.516271 


24 


41.400 


218.60 


24.16 


112.43 


2.606424 


1.617000 


25 


52.200 


275.61 


19.16 


178.78 


2.505718 


1.717671 


26 


65.856 


347.70 


15.19 


284.36 


2.405010 


1.818595 


27 


83.010 


438.32 


12.05 


452.62 


2.304304 


1.919130 


28 


104.67 


552.64 


9.55 


718.95 


2.203596 


2.019822 


29 


132.00 


697.01 


7.58 


1142.9 


2.102890 


2.120574 


30 


166.43 


878.80 


6.01 


1817.2 


2.002182 


2.221232 


31 


209.85 


1108.0 


4.77 


2888.0 


1.901476 


2.321909 


32 


264.68 


1397.6 


3.78 


4595.5 


1.800768 


2.422721 


33 


333.68 


1760.2 


3.00 


7302.0 


1.700060 


2.523330 


34 


420.87 


2222.2 


2.38 


11627. 


1.599354 


2.624148 


35 


530.60 


2801.8 


1.88 


18440. 


1.498646 


2.724767 


36 


669.00 


3532.5 


1.50 


29352. 


1.397940 


2.825426 


37 


843.46 


4453.0 


1.19 


46600. 


1.297234 


2.926064 


38 


1064.0 


5618.0 


.95 


74240. 


1 . 196526 


3.026942 


39 


1341.2 


7082.0 


.75 


118070. 


1.095820 


3.127494 


40 


1691.1 


8930.0 


.59 


187700. 


0.995112 


3.228169 



* Calculated on the basis of Dr. Matthiessen's standard, viz.: The re- 
sistance of a pure soft copper wire 1 meter long, having a weight of 1 gram = 
.141729 International Ohm at 0° C. The purest aluminum obtainable has a 
conductivity of over 63 per cent, but this gain in conductivity is at a greatly 
increased cost. 



STRANDED ALUMINUM WIRE. 



197 



Stranded Weatherproof Aluminum Wire. 

(Triple Braid.) 



Circular Mils 

and B. & S. 

Gauge. 


Diameter 
in Mils. 


Lbs. per 
1000 ft. 


Circular Mils 

and B. & S. 

Gauge. 


Diameter 
in Mils. 


Lbs. per 
1000 ft. 


1,000,000 


1.152 


1408 


400,000 


.728 


567 


950,000 


1.125 


1340 


350,000 


.679 


502 


900,000 


1.092 


1270 


300,000 


.630 


436 


850,000 


1.062 


1202 


250,000 


.590 


375 


800,000 


1.035 


1135 


0000 


.530 


280 


750,000 


.999 


1067 


000 


.470 


232 


700,000 


.963 


1001 


00 


.420 


192 


650,000 


.927 


938 





.375 


155 


600,000 


.891 


878 


1 


.330 


132 


550 000 


.855 


806 


2 


.291 


108 


500,000 


.819 


740 


3 


.261 


88 


450,000 


.770 


665 1 


4 


.231 


72 



Dimensions and Resistances of Stranded Aluminum Wire. 
H. W. Buck. 

Relative Conductivity 62%. 

Resistance per Mil-foot 16.95 ohms. 

Temperature 75° F. 

Elastic Limit 14,000 lbs. per square inch. 

Ultimate Strength 26,000 lbs. per square inch. 





-a 




Pounds 
per 




Ohms per 


1 


en 

0; J 


Size C. M. 


03 02 


Area 

Sq. 




Feet 






3jg 












and B. & S. 


Inch. 






per Lb. 






o^ 


s a 1 




a* 

s 




1000 
Feet. 


Mile. 




1000 
Feet. 


Mil. 


00 

03 
H 


pg 
& 


1,000,000 


1.15 


.7870 


920 


4,858 


1.087 


.01695 


.08950 


10,995 


20,420 


950,000 


1.12 


.7470 


874 


4,617 


1.144 


.01784 


.09420 


10,440 


19,400 


900,000 


1.09 


.7075 


828 


4,374 


1.208 


.01883 


.09942 


9,900 


18,380 


850,000 


1.06 


.6680 


782 


4,131 


1.279 


.01994 


.10529 


9,350 


17,360 


800,000 


1.03 


.6290 


736 


3,888 


1.359 


.02119 


.11188 


8,800 


16,340 


750,000 


1.00 


.5890 


690 


3,645 


1.449 


.02260 


.11933 


8,230 


15,320 


700,000 


.96 


.5500 


644 


3,402 


1.553 


.02421 


.12782 


7,700 


14,300 


650,000 


.93 


.5120 


598 


3,159 


1.672 


.02608 


.13770 


7,150 


13,270 


600,000 


.89 


.4720 


552 


2,916 


1.812 


.02825 


.14917 


6,600 


12,250 


550,000 


.85 


.4330 


506 


2,673 


1.977 


.03082 


. 16275 


6,050 


11,230 


500,000 


.81 


.3930 


460 


2,430 


2.041 


.03300 


. 17900 


5,500 


10,210 


450,000 


.77 


.3540 


414 


2,187 


2.415 


.03766 


. 19884 


4,950 


9,190 


400,000 


.73 


.3141 


368 


1,944 


2.718 


.04237 


.22370 


4,400 


8,170 


350,000 


.68 


.2750 


322 


1,701 


3.106 


.04843 


.25570 


3,850 


7,150 


300,000 


.63 


.2360 


276 


1,458 


3.623 


.05652 


.29830 


3,300 


6,130 


250,000 


.58 


.1965 


230 


1,215 


4.348 


.06780 


.35800 


2,750 


5,110 


0000 


.54 


.1661 


194.7 


1,028 


5.733 


.08010 


.42290 


2,330 


4,320 


000 


.47 


.1317 


154.4 


816 


6.477 


. 10100 


.53315 


1,850 


3,430 


00 


.42 


.1045 


122.4 


647 


8.165 


.12740 


.67270 


1,460 


2,720 





.37 


.0829 


97.1 


513 


10.300 


.16050 


.84740 


960 


2,150 


1 


.33 


.0657 


77.0 


407 


12.990 


.20250 


1.0692 


920 


1,710 


2 


.30 


.0521 


61.0 


323 


16.400 


.25540 


1.3486 


730 


1,355 


3 


.26 


.0413 


48.5 


256 


20.620 


.32200 


1.7002 


579 


1,075 


4 


.23 


.0327 


38.5 


203 


25.970 


.40600 


2.1438 


450 


852 



198 



PROPERTIES OF CONDUCTORS. 



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tOiOOCOl> i>0000O>Ci rH<NTt<CO00 <NcOC0<NC0 l>iO!>iO'-i *0 

OOOOO OOOOO tHt-ItHi-ith CN<NcO , tfiO <OOOOCOt> >-i 



iHl-li-H <N 



moshho ocoon"* ^coo^-* ooo 

NINOICO'* CO CO IO 00 00 ^OOOOCDN OOOOHON i-i CO t> OS OS *0 

OhhMcO ^ iO CO 1> 00 H«00»0 MOWOh OOi-iCOcOCO 00 

r-H rH i-H ,-1 tH rH ,-( tH tH i-H C3 CN CN CO CO "^ iO CO 00 O N©0»0(N O 

OOOOO OOOOO OOOOO OOOOh t-it-icN(NCO ^ 



00NOICO ©t^NOh CO <N CM 00 b- HOiOOO O 

t^^r^oOO CO<M00CO>O CO 00 OS "tf <N i-h O 00 00 O l>C0C0b-O O 

OOINCOOCO i-h CO »0 rtn lo t^CMrHCOO iCiOOOH H®t»N«3 00 

«oi>i>oooo ooo'-ioq coowooq mnohio cmcoo'*^ "- 1 



iO CO»OC5*OiO t^ 

OOrHCNcOT-i i-i»OOsr)HC0 O t> '-• t>- CO CHOOOcMO MOfOO^ '- | 

!>OrHCNTt< CONMOM CO*OI>000 »-iCN|00<N^-i rfiOOCNiO O 

COCNOiOrH t>C0O5L0<N OO^OOCO OiOCMOOO O iO ^ CO <N CM 
NNCOOO 100^^^ C0C0C0CN<N »-h r-t ih i-h 



1O00 tMTt<i>o<M iOI>OiO^O l>i0^01>C^ ^ 

TjH^HOiCOCO H00ONO5 r^r^T-iOO CO^-tfCOCo' i-HCOOOOO oo 

lOOOOCOO Cir-tiot^Ci M^OOOCO COO"*05iO <N05l>0^ CO 

^COCOCN|t-i OO^00t> t><OiGiO-*t< COCOCNrHi-H i-h 



lO-^CMOq^ OOO0000 OOOCOiO^ COr^COfNO O^COOOi-i CO 

i-HCit^iO<N ^Oil>^<N OOOCO^CXJ O CM 0010^-1 CO<MiO^-HrH <N 

^Nhioo COCOO^OO CN iO Oi CO b- hcOOOCO OOO'dO'^ P0 

NhhoO O50000l>0 OiO"^^CO CO<NcNi-ii-H i-hOOOO O 



^^COCOCN (NCNIrHrHO OOO00N i>COiOiO"* T^COCOCO<N 



OOOOO OOOOO OOOOO OOOOO ooooo o 

OOOOO OOOOO OLOO^OO lOOOOO OOO500CN o 

•^^q^"* *OC0 CO "^"^ T *l ,_ tC0'-^CN ,- l , ^CiM0q > MO5HO5C0 " : ^ 

o"r-To4"co^" i6<£i^cca$ <OT-*cic<$*$ loViodto c<f rt< eo"io c4" »h 

OOOCNrt^cO 000^^0 C5'-iC0iOl> O CO CO ^ CO COOOOCOiO ^ 

tOiO-^COCN hhOOOO t>l>COiO^ COCOCNCNr-i tH 1-1 



OOOOO OOOOO OOOOO OOOOO r-icNC0Tt<iO CO 

OOOOO OOOOO ooooo oooo 

<d<o<o<oo ooooo qqqqq qoo 

ooooo ooooo ooooo o° 

OiOO*00 »00i00*0 OiOOiOO »o 

OOiOOOOO t^t^cocoio »O^T^c0C0 <N 



IRON AND STEEL WIRE. 



199 



Aluminum for Ilig-li Tension Transmission JLines. 

1. Stranded wire should always be used, even in the smaller sizes, as 
the action of the wind causes solid aluminum wire to "crystallize," thereby 
decreasing its strength; also, there is less liability of flaws in the metal 
causing breakage. 

2. Aluminum gathers much less sleet than copper. 

3. It costs less to string aluminum than copper, due to the less weight. 

4. Care must be taken in stringing aluminum to prevent denting and 
abrasion, as the wire is very soft. 

5. Mechanical and splice joints made without the use of solder are entirely 
satisfactory. 

6. Wires should be strung far enough apart to prevent trouble from 
burning-off of. the wire in case of a short circuit. 

7. Due to its high coefficient of linear expansion and low tensile strength, 
the minimum allowable sag for aluminum wire is considerably greater than 
for copper. This is one great objection to aluminum for telephone and 
telegraph lines. For long spans the difference in deflection between alu- 
minum and copper wires may be so great as to require a considerably higher 
pole in case aluminum is used, although the pole need not be as strong as 
would be required for copper, as the weight of aluminum for equal con- 
ductivity is but 47 per cent of the weight of copper. 



VltO.Y ASTO §TEEI WIRE, 
Physical Constants of Best Galvanized Telegraph Wire. 



Per cent Conductivity (copper 100) .... 
Per cent Conductivity (pure iron 100) . . . 

Specific Gravity 

Pounds in 1 cubic foot 

Pounds in 1 cubic inch 

Pounds per mile per circular mil 

Ultimate strength, ■ r— 

sq. m. 

Modulus of elasticity, : i~ ! — 

in. X sq. in. 
Coefficient of Linear Expansion per ° C. . . . 
Coefficient of Linear Expansion per °F. . . . 

Melting Point in ° C . 

Melting Point in ° F 

Specific Heat (watt-seconds to heat 1 lb. 1° C.) 
Thermal Conductivity (watts through cu. in. 

temperature gradient 1° C.) 

Resistance 

Microhms per centimeter cube at 0° C. . . 

Microhms per inch cube at 0° C 

Ohms per mil foot at 0° C 

Ohms per mil foot at 20° C 

Ohms per mile at ° C 

Ohms per mile at 20° C 

Pounds per mile-ohm ° C 

Pounds per mile-ohm 20° C 

Temperature Coefficient per ° C 

Temperature Coefficient per ° F 



Iron. 



Steel. 



16.8 


12.2 


95.5 


69.2 


7.8 


7.85 


487 


490 


.282 


.284 


.014 


.0141 


55,000 


68,000 


26,000,000 


30,000,000 


.000012 


.000012 


.0000067 


.0000067 


1600 


1475 


2910 


2685 


209 


209 


1.39 


1.39 


9.5 


13.1 


3.74 


5.17 


57.2 


78.9 


62.9 


86.8 


302,000 


417,000 


cir. mils 


cir. mils 


332,000 


458,000 


cir. mils 


cir. mils 


4230 


5850 


4700 


6500 


.005 


.005 


.0028 


.0028 



200 



PROPERTIES OF CONDUCTORS. 



Double Galvanized Telegraph and Telephone IFire 
of the Higrhest .Electrical Qualities. 

ROEBLING. 







00 








3 


o 


3 


T3 

d 


Approximate 
Breaking Strain in 


Average Resistance 


o aJ 




P-< ® 


3 


in Ohms at 68° F. 




.9 


.a§ 


.a 4 © 


Pounds. 




fco 


a 


^3 0> 


3 






.Q 














a 


'S 


3 


E.B.B. 


B.B. 


Steel. 


E.B.B. 


B.B. 


Steel. 


* 


S 


£ 


pui 














4 


.225 


730 


| mile. 


2,190 


2,409 


2,701 


6.44 


7.53 


8.90 


6 


.192 


540 


£ mile. 


1,620 


1,782 


1,998 


8.70 


10.19 


12.04 


8 


.162 


380 


£ mile. 


1,140 


1,254 


1,406 


12.37 


14.47 


17.10 


9 


.148 


320 


J mile. 


960 


1,056 


1,184 


14.69 


17.19 


20.31 


10 


.135 


260 


£ mile. 


780 


858 


962 


18.08 


21.15 


25.00 


11 


.120 


214 


£ mile. 


* 642 


706 


792 


21.96 


25.70 


30.37 


12 


.105 


165 


■£■ mile. 


495 


545 


611 


28.48 


33.33 


39.39 


14 


.080 


96 


i mile. 


288 


317 


355 


48.96 


57.29 


67.71 



The values given in this table are averages of a large number of tests, 
They are within the limits of the specifications of the Western Union Tele- 
graph Company. 

The average value of the mile-ohm is 4,700 for E. B. B. wire. 

The average value of the mile-ohm is 5,500 for B. B. wire. 

The average value of the mile-ohm is 6,500 for Steel wire. 

The average breaking strain is 3 times the weight per mile for E.B.B. 
wire. 

The average breaking strain is 3.3 times the weight per mile for B. B. wire. 

The average breaking strain is 3.7 times the weight per mile for Steel wire. 

The mile-ohm = weight per mile X resistance per mile. 



Galvanized Sig*nal Strand. Seven "Wires. 



Diameter, 


Weight per 1000'. 


Estimated 
Breaking 


Inches. 










Bare Strand. 


Double Braid 
W. P. 


Triple Braid 
W. P. 


Weight. 


1-2 


520 


616 


677 


8,320 


15-32 


420 


510 


561 


6,720 


7-16 


360 


444 


488 


5,720 


3-8 


290 


362 


398 


4,640 


5-16 


210 


270 


297 


3,360 


9-32 


160 


214 


235 


2,560 


17-64 


120 


171 


188 


1,920 


1-4 


100 


148 


163 


1,600 


7-32 


80 


122 


134 


1,280 


3-16 


60 


96 


105 


960 


11-64 


43 


76 


84 


688 


9-64 


33 


60 


66 


528 


1-8 


24 


48 


53 


384 


3-32 


20 


38 


42 


320 



IRON AND STEEL WIRE. 



201 



Properties of Steel Wire. 

ROEBLING. 

Note. — The breaking weights given for steel wire are not those of Steel 
Telegraph wire. They apply to wire with a tensile strength of 100,000 
pounds per square inch. This strength is higher than that of telegraph wire. 



No. t 


Diam- 
eter in 
Inches. 


Area in 

Square 
Inches. 


Breaking 

Strain 

100,000 lbs. 

sq. inch. 


Weight in Pounds. 




Roeb- 
lingG 


Per 
1,000 ft. 


Per Mile. 


Feet in 
2,000 lbs. 


6-0 


.460 


.166191 


16,619 


558.4 


2,948 


3,582 


5-0 


.430 


.145221 


14,522 


487.9 


2,576 


4,099 


4-0 


.393 


.121304 


12,130 


407.6 


2,152 


4,907 


3-0 


.362 


.102922 


10,292 


345.8 


1,826 


5,783 


2-0 


.331 


.086049 


8,605 


289.1 


1,527 


6,917 





.307 


.074023 


7,402 


248.7 


1,313 


8,041 


1 


.283 


.062902 


6,290 


211.4 


1,116 


9,463 


2 


.263 


.054325 


5,433 


182.5 


964 


10,957 


3 


.244 


.046760 


4,676 


157.1 


830 


12,730 


4 


.225 


.039761 


3,976 


133.6 


705 


14,970 


5 


.207 


.033654 


3,365 


113.1 


597 


17,687 


6 


.192 


.028953 


2,895 


97.3 


514 


20,559 


7 


.177 


.024606 


2,461 


82.7 


437 


24,191 


8 


.162 


.020612 


2,061 


69.3 


366 


28,878 


9 


.148 


.017203 


1,720 


57.8 


305 


34,600 


10 


.135 


.014314 


1,431 


48.1 


254 


41,584 


11 


.120 


.011310 


1,131 


38.0 


201 


52,631 


12 


.105 


.008659 


866 


29.1 


154 


68,752 


13 


.092 


.006648 


665 


22.3 


118 


89,525 


14 


.080 


.005027 


503 


16.9 


89.2 


118,413 


15 


.072 


.004071 


407 


13 7 


72.2 


146,198 


16 


.063 


.003117 


312 


10.5 


55.3 


191,022 


17 


.054 


.002290 


229 


7.70 


40.6 


259,909 


18 


.047 


.001735 


174 


5.83 


30.8 


343,112 


19 


.041 


.001320 


132 


4.44 


23.4 


450,856 


20 


.035 


.000962 


96 


3.23 


17.1 


618,620 


21 


.032 


.000804 


80 


2.70 


14.3 


740,193 


22 


.028 


.000616 


62 


2.07 


10.9 


966,651 


23 


.025 


.000491 


49 


1.65 


8.71 




24 


.023 


.000415 


42 


1.40 


7.37 




25 


.020 


.000314 


31 


1.06 


5.58 




26 


.018 


.000254 


25 


.855 


4.51 




27 


.017 


.000227 


23 


.763 


4.03 




28 


.016 


.000201 


20 


.676 


3.57 




29 


.015 


.000177 


18 


.594 


3.14 




30 


.014 


.000154 


15 


.517 


2.73 




31 


.0135 


.000143 


14 


.481 


2.54 




32 


.013 


.000133 


13 


.446 


2.36 




33 


.011 


.000095 


9.5 


.319 


1.69 




34 


.010 


.000079 


7.9 


.264 


1.39 




35 


.0095 


.000071 


7.1 


.238 


1.26 




36 


.009 


.000064 


6.4 


.214 


1.13 





This table was calculated on a basis of 483.84 pounds per cubic foot for 
steel wire. Iron wire is a trifle lighter. 

The breaking strains are calculated for 100,000 pounds per square inch 
throughout, simply for convenience, so that the breaking strains of wires 
of any strength per square inch may be quickly determined by multiplying 
the values given in the tables by the ratio between the strength per square 
inch and 100,000. Thus, a No. 15 wire, with a strength per square inch of 

150,000 pounds, has a breaking strain of 407 X \^qqq = 610.5 pounds. 

The "Roebling" or "Market wire Gauge" is now used as standard for 
steel wires in America. 



202 



PROPERTIES OF CONDUCTORS. 



II E*I*T A\C i: %V I It i:*. 

Specific Resistance and Temperature Coefficient. 



Substance. 



Microhms 
per Cubic 
Centimeter 

about 

20° F. 



Temperature Coeffi- 
cient per ° C. 



Platinum silver 

(Pt 66, Ag 33) 
Patent-Nickel 

(Cu74.41,Zn0.23,Ni25.10,Fe0.42, 

Mn0.13) 

Platinoid 

(Cu 59 Zn 25.5, Ni 14, W 55) 
German Silver 

(Cu, Zn, Ni in various proportions) 
Manganin 

(Cu, Ni, and Fe-Mn in various propor- 
tions) 

Boker & Co.'s Iala, hard 

Boker & Co.'s Iala, soft 

Krupp's metal 

Driver-Harris Co.'s "S. B." 

Driver-Harris Co.'s "Advance" . . . . 
Driver-Harris Co.'s "Ferro-Nickel" . . 
Constantin 



31.726 



.000243 



34.2 


.00019 


32.5 




19 to 46 


.00025 to .00044 


42 to 74 


.000011 to .00014 


50.2 


— .000011 


47.1 


+ .000005 


85.13 


.0007007 


55.8 


Small 


48.8 


Very small 


28.3 


.00207 


50 to 52 





German Silver. 

German silver is an alloy of copper, nickel, and zinc. The electrical 
properties of the alloy naturally vary considerably with the proportions of 
the constituent metals. The proportion of nickel present is ordinarily used 
to distinguish the various alloys, as the amount of this metal present in the 
alloy fixes the proportions of the other constituents in order that the result- 
ing material may be easily worked. As made in the United States, com- 
mercial German silver is made with approximately the following propor- 
tions. 

(Dr. F. A. C. Perrine.) 



Designation. 


Constituents. 


Resistance at ° C. 


Per Cent. 
Alloy. 


Nickel. 


Copper. 


Zinc. 


Microhms 
Per Centi- 
meter. 


Ohms 

Per Mil 

Foot. 


8 

12.5 
20 
30 


8 
12.5 
20 
30 


60 
57 
56 
50 


32 

30.5 
24 
20 


19 
25 
32 
46 


114 
150 
193 
277 



Specific gravity, 8.5. 
Temperature coefficient per ' 



C, .00025 to .00044. 



GERMAN SILVER WIRES. 



203 



Resistances of German Silver Wire at 20- I\ 

American Gauge. — (American Electrical Works). 







18% Alloy. 


30% Alloy. 




Resistance varies .03 of one 


Resistance varies .022 of one 




per cent for 


one degree 


per cent foi 


• one degree 




Centigrade. 


Centigrade. 


Size. 


Ohms per 
1000 ft. 


Ohms per 


Ohms per 


Ohms per 


pound. 


1000 ft. 


pound. 


No. 8 


11.772 


. 24702 


17.658 


.37054 




9 


14.83 


.39249 


22.22 


. 58873 




' 10 


18.72 


.62443 


28.08 


.93666 




' 11 


23.598 


.99281 


35.397 


1.4927 




' 12 


29.754 


1.5785 


44.631 


2.3676 




4 13 


37.512 


2.5101 


56.268 


3 . 7650 




' 14 


47.304 


3.9911 


70.956 


5.9862 




' 15 


59.652 


6.3462 


89 . 478 


9.5192 




' 16 


75.222 


10.090 


112.833 


15.135 




* 17 


94.842 


16.045 


142.263 


24.066 




' 18 


119.61 


25.511 


179.41 


38.266 




1 19 


155.106 


42.909 


232 . 659 


64 . 362 




4 20 


190.188 


64.498 


285.282 


96.524 




* 21 


239.814 


102.56 


359.721 


153.84 




1 22 


302.382 


163.06 


453.573 


244.60 




4 23 


381.33 


259.33 


571.99 


388.99 




4 24 


480.834 


412.37 


721.251 


618.55 




4 25 


606.312 


655.61 


909 . 468 


983 . 43 




4 26 


764.586 


1042.7 


1146.879 


1563.8 




4 27 


964.134 


1657.7 


1446.201 


2486.6 




4 28 


1215.756 


2636.0 


1823.634 


3953.9 




4 29 


1533.06 


4191.5 


2299 . 59 


6287.2 




' 30 


1933.038 


6666.5 


2899 . 557 


9999.6 




' 31 


2437.236 


10594. 


3655 . 854 


15890. 




4 32 


3073 . 77 


16850. 


4610.65 


25275. 




4 33 


3875.616 


26788. 


5813.424 


40181. 




4 34 


4888 . 494 


42618. 


7332.741 


63927. 




4 35 


6163.974 


67759. 


9245.961 


101640. 




4 36 


7770.816 


107700. 


11656.224 


161540. 




4 37 


9797.166 


171170. 


14695.749 


256770. 




4 38 


12357.198 


269820 . 


18535.797 


404740. 




4 39 


15570.828 


428720. 


23356.242 


643070. 


" 40 


19653.57 


682540. 


29480.35 


1023800. 



Specific Gravity 8.5 approx. 

Tffanganiii. 

Dr. F. A. C. Perrine. 

Perhaps the most remarkable resistance alloy which has been produced 
is manganin, invented by Edward Weston in 1889. It is composed of 
copper, nickel, and ferro-manganese in varying proportions. 

Prof. Nichols of Cornell, has shown that coils made of this material 
are apt to change their resistance when successively heated to 100° Cent, 
and cooled to 0° Cent., but Dr. Lindeck, working for the Reichsanstalt, states 
that when a completed coil is annealed at a temperature of 140° Cent, for 
five hours, no further difficulty is experienced from any aging change, 
whether produced by time or repeated heatings and coolings. 

A further advantage of manganin which has been noticed by Dr. Lindeck, 
when used for resistance coils, is its very feeble thermo-electric power when 
soldered to copper, as is almost always the case in standard coils. While 
for german silver the thermo-electric power is between 20 and 30 micro- 
volts per degree Centigrade, and for constantin, an alloy of copper 50 parts 
with nickel 50 parts, having a temperature coefficient between .00003 and 
.00004, a thermo-electric power of 40 micro-volts per degree Centigrade is 
found, the thermo-electric power of manganin is not above one or two micro- 
volts per degree. 



204 



PROPERTIES OF CONDUCTORS. 



Electrical Properties and Constitution of UEangpanin. 

Dr. F. A. C. Perrine. 









Mi- 






Composition. 


Ohms 


crohms 


Temper- 
ature Co- 
efficient. 


* Authority. 




per 
Mil- 


per 
Cubic 










Cu. 


Fe. Mn. 


Ni. 


Foot. 


Centi- 












meter. 




Nichols 


78.28 


14.07 


7.65 






0.000011 


Nichols 


51.52 


31.27 


16.22 






0.000039 


Perrine 


70. 


25. 




392 


65.15 




Perrine 


65. 


30. 


5 - Is 


404 


67.2 




Perrine 


65. 


30. 


5.JS3 


443 


73.6 




Feussner and Lindeck 


73. 


24. 


3. 


287 


47.7 


0.00003 


Lindeck 


84. 


12. 


4. 


253 


42.0 


0.00014 


Dewar and Fleming . 


84. 


12. 


4. 


287 


47.64 


0.0000 



Dimensions, Resistance, and Weights of Resistance Wires. 

Boker & Co.'s IaIa. 

Specific gravity ' 8.4 

Microhms per centimeter cube, 0° C, hard 50.2 

Microhms per centimeter cube, 0° C, soft 47 . 1 

Microhms per mil-foot, 0° C, hard 310. 

Microhms per mil-foot, 0° C, soft 284. 

Temperature coefficient per 0° C, hard -.000011 

Temperature coefficient per 0° C, soft + .000005 













Carrying 


B. &. S. 
Gauge 

No. 


Diameter, 
Inch. 


Area, 

Circular, 

Mils. 


Ohms per 
1000 Feet. 


Feet per Lb. 
Approxi- 
mately. 


Capacity 
with Free 
Radiation 
Amperes. 


14 


.0641 


4107. 


73.5 


85. 


.... 


16 


.0508 


2583. 


116.9 


135.3 




17 


.0453 


2048. 


147.4 


170.6 




18 


.0403 


1624. 


185.9 


215.5 


15.8 


19 


.0359 


1289. 


234.3 


271.0 


13.6 


20 


.0320 


1024. 


295.6 


342.3 


11.5 


21 


.0285 


812.3 


374.4 


433. 


9.7 


22 


.0253 


640.1 


470.1 


543.5 


8.0 


23 


.0225 


506.25 


596.6 


689.6 


6.8 


24 


.0201 


404. 


747.6 


870. 


5.8 


25 


.0179 


320.4 


945.6 


1098. 


4.9 


26 


.0159 


252.8 


1192.9 


1370. 


4.1 


27 


.0142 


201.6 


1497.8 


1724. 


3.6 


28 


.0126 


158.8 


1890.1 


2174. 


3.1 


29 


.0113 


127.7 


2407.8 


2777. 


2.9 


30 


.0100 


100. 


3005.3 


3448. 


2.7 


31 


.0089 


79.2 


3789 . 2 


4347. 




32 


.0080 


64. 


4779 . 1 


5555. 


2.5 


33 


.0071 


50.4 


6025 . 1 


7142. 




34 


.0063 


39.69 


7600.4 


9090. 


2.2 


35 


.0056 


31.56 


9582.7 


11100. 




36 


.005 


25. 


12081 . 


14286. 


2.6 


37 


.0044 


19.83 


15229. 


17543. 




38 


.004 


16. 


19213. 


22220. 




39 


.0035 


12.25 


24218. 


27700. 




40 


.0031 


9.61 


30570. 


35714. 





Supplied by Boker Co., 101-103 Duane St., New York. 



borer's resistance ribbon. 



205 



Resistance Ribbon. la la Quality. 



of 






Ohms per 1000 feet. 










iin. 


iin. 


I in. 


i in. 


f in. 


fin. 


iin. 


1 in. 


.128 


14.81 


7.40 


4.93 


3.70 


2.96 


2.46 


2.11 


1.85 


.114 


16.69 


8.34 


5.56 


4.17 


3.34 


2.78 


2.38 


2.08 


.101 


18.80 


9.40 


6.26 


4.70 


3.76 


3.13 


2.70 


2.35 


.0907 


20.97 


10.48 


6.99 


5.24 


4.19 


3.49 


2.99 


2.62 


.0808 


23.46 


11.73 


7.82 


5.86 


4.69 


3.91 


3.35 


2.93 


.0719 


26.63 


13.31 


8.87 


6.65 


5.32 


4.43 


3.80 


3.32 


.0641 


29.62 


14.81 


9.87 


7.40 


5.92 


4.93 


4.22 


3.70 


.0571 


33.38 


16.69 


11.12 


8.34 


6.68 


5.56 


4.77 


4.17 


.0508 


37.60 


18.80 


12.53 


9.40 


7.52 


6.26 


5.37 


4.70 


.0452 


41.94 


20.97 


13.98 


10.48 


8.38 


6.99 


5.99 


5.24 


.0403 


46.92 


23.46 


15.64 


11.73 


9.38 


7.82 


6.70 


5.86 


.0359 


53.26 


26.63 


17.78 


13.31 


10.64 


8.87 


7.60 


6.65 


.0320 


59.24 


29.62 


19.75 


14.81 


11.84 


9.87 


8.46 


7.40 


.0284 


66.76 


33.38 


22.25 


16.69 


13.35 


11.12 


9.53 


8.34 


.0253 


75.20 


37.60 


25.07 


18.80 


15.04 


12.53 


10.74 


9.40 


.0225 


83.88 


41.94 


27.96 


20.97 


16.77 


13.98 


11.96 


10.48 


.0201 


93.84 


46.92 


31.28 


23.46 


18.77 


15.64 


13.40 


11.73 


.0179 


106.52 


53.26 


35.50 


26.63 


21.30 


17.78 


15.21 


13.31 


.0159 


118.48 


59.24 


39.49 


29.62 


23.69 


19.75 


16.91 


14.81 


.0142 


133.52 


66.76 


44.50 


33.38 


26.70 


22.25 


19.07 


16.69 


.0126 


150.40 


75.20 


50.13 


37.60 


30.08 


25.07 


21.50 


18.80 


.0112 


167.76 


83.88 


55.92 


41.94 


33.55 


27.96 


23.96 


20.97 


.0100 


187.68 


93.84 


62.56 


46.92 


37.53 


31.28 


26.81 


23.46 


.0089 


213.04 


106.52 


71.01 


53.26 


42.60 


35.50 


30.43 


26.63 


.0079 


236.96 


118.48 


78.98 


59.24 


47.40 


39.49 


33.82 


29.62 


.0071 


267.04 


133 . 52 


89.01 


66.76 


53.40 


44.50 


38.15 


33.38 


.0063 


300.80 


150.40 


100.26 


75.20 


60.16 


50.13 


42.97 


37.60 


.0056 


335.52 


167.76 


111.84 


83.88 


67.10 


55.92 


47.93 


41.94 


.005 


375.36 


187.68 


125.12 


93.84 


75.07 


62.56 


53.62 


46.92 


.0044 


426.08 


213.04 


142.02 


106.52 


85.21 


71.01 


60.87 


53.26 


.004 


473 . 92 


236.96 


157.97 


118.48 


94.78 


78.98 


67.64 


59.24 



206 



PROPERTIES OF CONDUCTORS. 



Krupp's Resistance Wires. 

Specific gravity 8.102. 

Specific resistance at 20° C. mean 85 . 13 microhms. 

Temperature coefficient, mean .0007007. 

Resistance per circular mil-foot 314. ohms. 

Resistance per 1000', 1 square inch area ... .8513 ohms. 

This metal can be permanently loaded with current sufficient to raise its 
temperature to 600° C. (1112° F.) without undergoing any structural change. 
It should never be put in contact with asbestos, however, as this material 
causes it to deteriorate rapidly. 



Diam. 


Diam. 
in inches. 


Near- 
est 
B. &S. 
Gauge 


Feet 
per 
lb. 


Resistance 


in ohms per foot. 


in m.m. 


at 


at 


at 


at 






No. 




68° F. 


176° F. 


284° F. 


428° F. 


5 


.1968 


4 


9 


.0132 


.0138 


.0143 


.0150 


4* 


.1772 


5 


12 


.0163 


.0170 


.0176 


.0184 


4 


.1575 


6 


15 


.0206 


.0215 


.0224 


.0235 


3* 


.1378 


7 


19 


.0269 


.0280 


.0291 


.0307 


3 


.1181 


9+ 


26 


.0368 


.0382 


.0396 


.0417 


2| 


.1083 


9— 


31 


.0437 


.0455 


.0472 


.0497 


2* 


.0984 


10 


37 


.0528 


.0550 


.0570 


.0601 


H 


.0885 


11 


46 


.0653 


.0679 


.0705 


.0742 


2 


.0787 


12 


58 


.0825 


.0860 


.0892 


.0940 


If 


.0689 


13 


76 


.1078 


.112 


.116 


.123 


li 


.0590 


15 


104 


.1468 


.153 


.159 


.167 


n 


.0492 


16 


150 


.2115 


.220 


.229 


.241 


i 


.0393 


18 


234 


.3305 


.344 


.356 


.376 


i 


.0295 


21 


415 


.5870 


.610 


.633 


.667 


i 


.0196 


24 


937 


1.324 


1.38 


1.43 


1.51 



American Agent, Thomas Prosser & Son, 15 Gold St., New York City. 



Resistance Wires Made by Driver-Harris Wire Co., 
Harrison, A . T. 



11 S. B." — Resistance per mil-foot at 75° F. 

Low temperature coefficient and low thermo-electric effect 
against copper. Will not rust. 

'Advance." — Resistance per mil-foot at 75° F. 

A copper-nickel alloy containing no zinc. Temperature 
coefficient practically nil. 

"Ferro-Nickel." — Resistance per mil-foot at 75° F. 
Temperature coefficient per ° F. 

About the same resistance as German Silver, but weighs 
about ten per cent less and is cheaper. 



336 ohms 



294 ohms 



170 ohms 
.00115 



DRIVER-HARRIS RESISTANCE WIRES. 



207 



Resistances of Driver-Harris Resistance Wires. 





"S. B." 


"Advance." 


"Ferro-Nickel." 


No. B. & S. 










Ohms per 


Ohms per 


Ohms per 




1,000 ft. 


1,000 ft. 


1,000 ft. 


10 


32 


28. 


2.0 


11 


40 


35.5 


2.5 


12 


51 


44.8 


3.2 


13 


64 


56.7 


4.1 


14 


82 


71.7 


5.1 


15 


103 


90.4 


6.5 


16 


130 


113 


8.2 


17 


168 


145 


10.4 


18 


210 


184 


13.1 


19 


260 


226 


16.3 


20 


328 


287 


20.5 


21 


415 


362 


25.9 


22 


525 


460 


32.7 


23 


660 


575 


41.5 


24 


831 


725 


52.3 


25 


1,050 


919 


65.4 


26 


1,328 


1,162 


85 


27 


1,667 


1,455 


106 


28 


2,112 


1,850 


131 


29 


2,625 


2,300 


166 


30 


3,360 


2,940 


209 


31 


4,250 


3,680 


266 


32 


5,250 


4,600 


333 


33 


6,660 


5,830 


425 


34 


8,400 


7,400 


531 


35 


10,700 


9,360 


672 


36 


13,440 


11,760 


850 


37 


16,640 


14,550 


1,070 


38 


21,000 


18,375 


1,330 


39 


27,540 


24,100 


1,700 


40 


37,300 


32,660 


2,120 



208 PROPERTIES OF CONDUCTORS. 

CURRENT CARRYING CAPACITY Or Willie 
A3TI> CABLES. 

Let D — diameter of wire or cable core in inches. 

T = temperature elevation of wire or cable core in ° Centigrade. 
/ = current in wire in amperes. 

r — specific resistance of wire in ohms per mil-foot at final tem- 
perature. 
The following approximate formulae give results sufficiently accurate for 
practical purposes. 

Bare Overhead Wires Out of Doors. 
Stranded : Solid : 

/-nooy/lp. / = i250 V / ^ 3 - 

3 Wires In Doors, Expose] 
ed: S 

y/™_ 3 . / = 660 Jl 

>r Rubber Covered Cable : 
ed :__ Solid : 

i/™ 3 . / - 530 yfe 



Bare Wires In Doors, Exposed. 
Stranded : Solid : 

610 ■* * 

Single Conductor Rubber Covered Cable in Still Air. 

Stranded : Solid : 

j = 49Q a i/TD* 



Single Conductor Rubber Covered Lead Sheathed Cable in 
Underground Single Duct Conduit. 

Stranded : Solid : 

/ = 490 l/M 7 - 530 \JIf. 

Single Conductor Paper Covered Lead Sheathed Cable in 
Underground Single Duct Conduit. 

Stranded : Solid : 

/ = 430 



yfe 1 = 470 y^ 3 . 



* Three-Conductor Rubber Covered Lead Sheathed Cable in 
Underground Single Duct Conduit. 

Stranded : Solid : 

/ = 370 \/lf- I = 400 jlf. 

* Three-Conductor Paper Covered Lead Sheathed Cable in 
Underground Single Duct Conduit. 

Stranded : Solid : 

7 - 320 V& / - 350 t/*l!. 



* / is here current per wire. 



CAPACITY OF WIRES AND CABLES. 



209 



Carrying* Capacity of Insulated Copper Wires for 
Interior Wiring*. 

National Electrical Code. 



B. &S. 
Co. 



18 

16 

14 

12 

10 

8 

6 

5 

4 

3 

2 

1 



00 

000 

0000 



Circular 
Mils. 



1,624 

2,583 

4,107 

6,530 

10,380 

16,510 

26,250 

33,100 

41,740 

52,630 

66,370 

83,690 

105,500 

133,100 

167,800 

211,600 



Rubber 


Weather 


Covered 


proof 
Wires. 


Wires. 


Am- 


Am- 


peres. 


peres. 


3 


5 


6 


8 


12 


16 


17 


23 


24 


32 


33 


46 


46 


65 


54 


77 


65 


92 


76 


110 


90 


131 


107 


156 


127 


185 


150 


220 


177 


262 


210 


312 



Circular 
Mils. 



200,000 

300,000 

400,000 

500,000 

600,000 

700,000 

800,000 

900,000 

1,000,000 

1,100,000 

1,200,000 

1,300,000 

1,400,000 

1,500,000 

1,600,000 

1,700,000 

1,800,000 

1,900,000 

2,000,000 



Rubber 

Covered 

Wires. 

Amperes. 



200 
270 
330 
390 
450 
500 
550 
600 
650 
690 
730 
770 
810 
850 
890 
930 
970 
1,010 
1,050 



Weather- 
proof 
Wires. 

Amperes. 



300 

400 

500 

590 

680 

760 

840 

920 

1,000 

1,080 

1,150 

1,220 

1 290 

1,360 

1,430 

1,490 

1,550 

1,610 

1,670 



Carrying* Capacity of Stranded Copper Conductors for 
Interior IViring*. 





National Electrical 


Code. 




B. d 


_ q n Area Actual 
z S * G * C. M. 


No. of 

Strands. 


Size of g 
B. &£ 


trand A 

i q Amperes. 




L9 1,288 










L8 1,624 




. 






L7 2,048 










L6 2,583 






6* 


] 


L5 3,257 








] 


L4 4,107 






i2 


] 


L2 6,530 






17 




9,016 


*7 


is 


) 21 




11,368 


7 


u 


I 25 




14,336 


7 


Vt 


r 30 




18,081 


7 


le 


> 35 




22,799 


7 


u 


> 40 




30,856 


19 


u 


\ 50 




38,912 


19 


17 


60 




49,077 


19 


16 


1 70 




60,088 


37 


It 


1 ' 85 




75,776 


37 


17 


100 




99,064 


61 


IS 


120 




124,928 


61 


17 


145 




157,563 


61 


ie 


► 170 




198,677 


61 


15 


200 




250,527 


61 


14 


235 




296,387 


91 


IS 


270 




373,737 


91 


14 


320 




413,639 


127 


IS 


340 



For aluminum wire the carrying capacity of any given size is to be taken 
as 84 per cent of the value given in the above table. 



210 



PROPERTIES OF CONDUCTORS. 



Carrying* Capacity of Rubber Insulated Cables. 

(From technical letter of General Electric Company.) 

The following table of carrying capacity is based on tests of cables in 
still air. Insulation alone &" thick; lead j\" to I" thick; jute and 
asphalt jacket &" thick. Paper insulated cables heat 8% to 10% more 
than rubber insulated cables with same current and thickness of coverings. 
Cables require about four hours to reach final temperature. 

60% of total increase in temperature in 1st hour. 

30% of total increase in temperature in 2d hour. 

8% of total increase in temperature in 3d hour. 

Cables immersed in water will carry 50% more current with same increase 
of temperature, and cables buried in moist earth about 15% more. Rubber 
cables should not be run above 70° C. Paper cables should not be run above 

90° c. 







Amperes at 30° C. 


Amperes at 50° C 






Rise. 


Rise. 




Diameter 

Copper 

Core. 

Inches. 










Size. 




Leaded 




Leaded 




Braided. 


and Jute 


Braided. 


and Jute 








Covered. 




Covered. 


6 B. & S. Solid 


.162 


61 


56 


76 


68 


4 B. & S. Solid 


.204 


85 


78 


104 


94 


2 B. & S. Stranded 


.300 


133 


121 


162 


146 


1 B. & S. Stranded 


.325 


155 


141 


189 


170 


B. & S. Stranded 


.390 


191 


174 


231 


210 


00 B. & S. Stranded 


.420 


218 


199 


268 


241 


000 B. & S. Stranded 


.475 


266 


242 


325 


293 


0000 B. & S. Stranded 


.543 


320 


291 


391 


352 


250000 CM. 


.570 


355 


324 


435 


392 


300000 CM. 


.640 


414 


377 


506 


456 


350000 CM. 


.680 


460 


419 


563 


507 


400000 CM. 


.735 


512 


466 


626 


564 


450000 CM. 


.787 


562 


511 


687 


618 


500000 CM. 


.820 


606 


551 


742 


668 


600000 CM. 


.900 


694 


631 


848 


763 


750000 CM. 


1.020 


825 


750 


1016 


915 


900000 CM. 


1.096 


940 


855 


1149 


1034 


1000000 CM. 


1.157 


1017 


925 


1333 


1200 


1250000 CM. 


1.298 


1204 


1095 


1481 


1328 


1500000 CM. 


1.413 


1376 


1251 


1644 


1480 


2000000 CM. 


1.760 


1766 


1606 


2178 


1960 



Heating: of Cables in Multiple Duct Conduit. 

The mutual heating of cables in multiple duct conduit has been inves- 
tigated experimentally by H. W. Fisher, The following diagram and 
table shows the arrangement of the conduit system used by him and the 
size and kind of cable in each duct. Means were provided for connecting 
any or all the cables in series and observing the temperature of the con- 
ductor in each duct. 



CAPACITY OF WIRES AND CABLES. 



211 



© 


© 


© 


© 


© 


© 


© 


© 


© 


© 


© 


© 



Fig. 22. 





Number of 


Size B. & S. and 




Cable. 


Conductors. 


C. M. 


Insulation. 


A* .... . 




000 


fa" and fa" Paper 


B 


1 


500,000 


fa" Paper 


C* 




000 


fa" and fa" Paper 


D 




500,000 


fa" Paper 


E 




1,250,000 


fa" Paper 


F 




1,250,000 


fa" Paper 


G 




000 


fa" Paper 


H 




000 


Rubber 


I 




1,250,000 


fa" Paper 


J 




1,250,000 


fa" Paper 


K ..... 




000 


Rubber 


L 




000 


■fa" Paper 



* The three conductors of A and C in multiple. 
Fisher's results are summarized in the following table : 



Conductors 


30° C. 


Rise. 


50° C. 


Rise. 


Carrying Current. 


Conductor. 


Amperes. 


Conductor. 


Amperes. 


All 


A. &C. 

(l 

( I 
) E 

' F 

f B 
D 


130 
155 
180 
600 
590 
560 
535 
355 
400 


A. &C. 
G 
L 
I 
E 
J 
F 
B 
D 


180 


G, H, K 5 L 

E, F, I, J 

A, B, C, D, E, F, I, J. ... 


190 
260 
765 
750 
725 
690 
425 
550 



An inspection of this table will show that the current corresponding to a 
given temperature elevation is in each case less than that given by the 
formulae on page 208, the difference being from 4 to 25 per cent, depend- 
ing on the number of conductors in service and the location of the cable 
in question. It is to be noted that corner ducts radiate heat the best, and 
all outside ducts radiate heat much better than do the inside ducts. 



212 



PROPERTIES OF CONDUCTORS. 



Watt* per foot l,o*t in Single-Conductor Cables at 

Different Maximum Temperature with Different 

A mounts of Currents. 

(From Handbook No. XVII, 1906. Copyrighted by Standard Under- 
ground Cable Company.) 



Size B. & S. 




Current in 


Amperes. 






6 


66 


81 


93 


104 


114 


123 


5 


74 


91 


105 


117 


128 


138 


4 


84 


102 


117 


131 


144 


153 


3 


93 


114 


132 


148 


161 


175 


2 


105 


128 


148 


166 


181 


196 


1 


118 


148 


166 


186 


203 


220 





132 


162 


187 


209 


228 


247 


00 


149 


181 


210 


235 


256 


277 


000 


166 


204 


235 


263 


288 


311 


0090 


186 


229 


264 


295 


323 


350 


Area in 














1000 C. M. 














300 


222 


273 


315 


352 


385 


416 


400 


248 


315 


363 


406 


445 


480 


500 


288 


352 


406 


455 


498 


537 


600 


315 


385 


445 


497 


545 


587 


700 


341 


416 


480 


538 


588 


635 


800 


364 


446 


514 


575 


628 


679 


900 


386 


473 


545 


610 


666 


720 


1000 


407 


498 


575 


642 


703 


758 


1100 


426 


522 


602 


674 


736 


796 


1200 


446 


546 


630 


705 


772 


833 


1300 


462 


568 


655 


732 


802 


866 


1400 


480 


590 


681 


761 


834 


900 


1500 


496 


610 


704 


788 


862 


931 


1600 


512 


629 


726 


812 


889 


960 


1700 


529 


649 


750 


837 


916 


990 


1800 


543 


667 


770 


862 


943 


1018 


1900 


557 


686 


792 


886 


970 


1048 


2000 


573 


705 


813 


910 


995 


1075 



Temp. (100 
of cond. 1 125 
in°F. (150 



Watts lost per ft. 



1.81 
1.91 

2.00 



2.71 
2.87 

3.00 



3.62 
3.82 
4.00 



4.52 
4.78 
5.00 



5.43 
5.73 

6.00 



6.33 
6.69 

7.00 



The watts lost per foot means the amount of electric energy lost in heat- 
ing the conductor and is equal to the product of the resistance per foot of 
cable times the square of the current in amperes. 

The above table is useful in showing the watts lost in heating effect per 
foot of cable with different currents, and also in finding the size of con- 
ductor that must be used for a given current and watts per foot loss. 

For Two-Conductor Cables the watts corresponding to the dif- 
ferent currents must be multiplied by two, and to obtain the currents 
corresponding to the watts in the table multiply the currents given in the 
table by .707. 

For Threes Conductor Caliles the watts corresponding to the 
currents in the table, must be multiplied by 3, and to obtain the currents 
corresponding to the watts in the table multiply the currents given in the 
table by .577. 



CAPACITY OF WIRES AND CABLES. 



213 



Current Carrying* Capacity of Lead Covered Cables. 

(From Handbook No. XVII, 1906. Copyrighted by Standard Under- 
ground Cable Company.) 

The current carrying capacity of insulated copper cables sheathed with 
lead depends primarily upon 

(a) The size and number of conductors and their relative position. 

(6) The ability of the insulating material to withstand high tempera- 
tures and to conduct heat away from the copper conductor, — this latter 
being in turn dependent upon kind of insulation and its thickness. 

(c) The initial temperature of the medium surrounding the cable. 

(d) The ability of the medium surrounding the cable to dissipate heat 
with small temperature rise. 

(e) The number of operating cables in close proximity and their relative 
positions. 

Where a number of insulated conductors are under the same sheath, 
they are subject to an interchange of heat somewhat similar to that which 
takes place when a number of separate cables are laid closely together, 
and for that reason each conductor of a multi-conductor cable will have a 
smaller current carrying capacity than a single-conductor cable. If the 
various conductors are separately insulated and laid together in the form 
of flat or round duplex or triplex, their carrying capacity will be greater 
than if they are laid up in the form of two-conductor concentric or three- 
conductor concentric, since the enveloping conductors in the latter forma- 
tion seriously retard the dissipation of heat from the inner conductors. 
Assuming that unity (1.00) represents the carrying capacity of single- 
conductor cables, the capacity of multi-conductor cables would be given 
by the following: 



2 cond. flat or round form, 

3 cond. triplex form 



.87; concentric form, 
.75; concentric form, 



.79 
.60 



The following experiment on duplex concentric cable of 525,000 C. M. 
indicates clearly the danger in subjecting this type of cable to heavy over- 
loads of even short duration. The cable was first heated up by a current 
of 440 amperes for 5 hours. An overload of 50 per cent w T as then applied, 
the results in degrees Fahrenheit above the surrounding air being as 
follows: 



Time from Start. 


Min. 


15 Min. 


30 Min. 


45 Min. 


60 Min. 


90 Min. 


Inner Conductor . 
Outer Conductor . 
Lead Cover . . . 


70° 

55 

31 


84° 

65 

35 


98° 
76 
40 


111° 
85 
45 


123° 
94 
49 


142° 

108 

57 



In any cable the area over which dissipation of heat must take place is 
proportional to the circumference of the conductor or (since the circum- 
ference varies as the diameter), upon the diameter of the conductor, while 
the cross section of the conductor varies as the square of the diameter. 
Hence the size of conductor varies much more rapidly than its heat radiat- 
ing surface, and in consequence the amperage per square inch, or circular 
mil of copper section, must be less for large size conductors than for small, 
in order to have the same rise of temperature under the same conditions. 
The usual formula for carrying capacity, 



Current = 



3 

(diam. of Cond.) 
A constant 



takes account of this fact but not to a sufficient degree, and we find that 
for cables as ordinarily used in underground work, a more correct expression 
is the following: 

~ (diam. of Cond.)^ 

Current = - — -~- 

A constant 



214 



PROPERTIES OF CONDUCTORS. 



Rubber insulation is a somewhat better heat conductor than dry or 
saturated paper, and therefore, when applied to the same size conductor in 
equal thickness, will permit of a larger current flowing in the conductor for 
the same rise of temperature above the surrounding air. On the other 
hand, rubber deteriorates much more rapidly at high temperatures than 
saturated paper, and while this disadvantage is apparently compensated 
for up to about 150° Fahrenheit by its superior heat dissipating qualities, at 
higher temperatures deterioration takes place and becomes so serious that 
its value as an insulating medium disappears in a comparatively short time. 

As the thickness of insulation is increased, the temperature of the con- 
ductor, with any given current flowing gradually, increases and therefore 
the current carrying capacity becomes reduced. The reduction in capacity 
however, is not very great, being in the ratio of about 93 for §f insulation 
to 100 for & insulation, so that the values in the table given below should 
be slightly decreased when greater thicknesses than ■& are used. 

As it is the final temperature reached which really affects the carrying 
capacity, the initial temperature of surrounding medium must be taken 
into account. If, for instance, the conduit system parallels steam or hot 
water mains, the temperature of 150° F. (which we have assumed in the 
table on page 215 to be the maximum for safe continuous work on cables) 
will be reached with lower values of current than would otherwise be the 
case; and as 70° is the actual temperature we have assumed to exist in the 
surrounding medium prior to loading the cables, any increase over 70° 
must be compensated for by reducing the current carried. 

For rough calculations it will be safe to use the following multipliers to 
reduce the current carrying capacity given in the table on page 215 to the 
proper value for the corresponding initial temperatures: 



Initial Temp. , 


70 


80 


90 


100 


110 


120 


130 


140 


15C 


Multipliers . 


. 1.00 


.93 


.86 


.78 


.70 


.60 


.48 


.34 


.OC 




The ability of the surrounding medium to dissipate heat, directly affects 
the carrying capacity of the cables, as with the same current the cable 
might be comparatively cool if laid in good heat conducting material such 
as water, and dangerously hot if laid in poor heat conduct- 
ing material such as dry sand. Ordinary conduit systems 
of clay or terra cotta ducts laid in cement, dissipate heat 
fairly well, the outside ducts, however, being much more 
efficient in this function than the inner ones, so that an ideal 
system, from this point of view, would consist of a single 
horizontal layer of ducts. _ As this would require an enormous 
width of trench and considerable inconvenience in handling 
the cables in manholes when many cables are to be installed, 
we would suggest the form shown in Fig. 23 as being more 
practicable. 

Where more ducts are required, the vertical section shown 
could be easily duplicated, a considerable space, however, 
being left between them. With this arrangement, the carry- 
ing capacities given in the table on p. 215 could be somewhat 
increased. 

When a number of loaded cables are operating in close proximity to one 
another, the heat from one radiates, or is carried by conduction, to each of 
the others, and all raised in temperature beyond 
what would have resulted had only a single cable 
been in operation; and if the cables occupy 
adjacent ducts in a conduit system of approxi- 
mately square cross section laid in the usual way, 
the centrally located cable or the one just above 
the center in large installations (A in Fig. 24) 
will reach the highest temperature. This is equiv- 
alent to saying that its carrying capacity is 
reduced, and while this reduction does not amount 
to more than about 12 per cent (as compared 
with the cable most favorably located, — as at 
Z), Fig. 24) in the duct arrangement given, it may easily assume much 
greater proportions where large numbers of cables are massed together. 



Fig. 23. 




Fig. 24. 



CAPACITY OP WIRES AND CABLES. 



215 



Assuming that not more than twelve cables, arranged as shown in Fig. 
24, can be used, the average carrying capacity may be taken as the crite- 
rion for proper size of conductor; and for cables of a given type and size 
the carrying capacities of all cables, even though placed in adjacent ducts, 
will be represented by the following figures, taking unity as the average 
carrying capacity of four cables: 



No. Cables 2 

Multiplier 1.16 



4 


6 


8 


10 


12 


1.00 


.88 


.79 


.71 


.63 



Recommended Current Carrying* Capacities for Cables 
and Watts JLost per foot. 

For each of four equally loaded single conductor paper insulated lead 
covered cables, installed in adjacent ducts in the usual type of conduit 
system where the initial temperature does not exceed 70° F., the maximum 
safe temperature for continuous operation being taken at 150° F. 

(From Handbook No. XVII, 1906. Copyrighted by Standard Under- 
ground Cable Company.) 



Size 
B. & S. G. 


Safe Cur- 
rent in 
Amperes. 


Watts * 

lost per 

ft. at 

150° F. 


Size 
CM. 


Safe Cur- 
rent in 
Amperes. 


Watts * 
lost per 

ft. at 
150° F. 


14 


18 


.97 


300,000 


323 


4.22 


13 


21 


1.03 


400,000 


390 


4.61 


12 


24 


1.09 


500,000 


450 


4.91 


11 


29 


1.15 


600,000 


505 


5.16 


10 


33 


1.25 


700,000 


558 


5.36 


9 


38 


1.39 


800,000 


607 


5.56 


8 


45 


1.53 


900,000 


650 


5.71 


7 


53 


1.67 


1,000,000 


695 


5.86 


6 


64 


1.85 


1,100,000 


740 


6.01 


5 


76 


2.08 


1,200,000 


780 


6.13 


4 


91 


2.31 


1,300.000 


820 


6.25 


3 


108 


2.54 


1,400,000 


857 


6.37 


2 


125 


2.77 


1,500,000 


895 


6.49 


1 


146 


3.00 


1,600,000 


933 


6.61 





168 


3.23 


1,700,000 


970 


6.73 


00 


195 


3.46 


1,800,000 


1010 


6.85 


000 


225 


3.69 


1,900.000 


1045 


6.97 


0000 


260 


3.92 


2,000,000 


1085 


7.09 



* This column represents the amount of energy which is transformed 
into heat and which must be dissipated. It is what is usually called the 
PR loss and it is figured by using for / the current values given ; and for R 
the resistance of the respective conductor at a temperature of 150° F. 

Note. — The table is compiled from a long series of tests made by us 
in conjunction with the Niagara Falls Power Company, the conduit system 
being of the type shown in Fig. 24. The ducts were of terra cotta with 
3-inch openings. 



216 



PROPERTIES OF CONDUCTORS. 



Recommended Power Carrying* Capacity in Kilowatt* 

of .Delivered Energy , Three-Conductor, Three-Phase 

Cables. 

(From Handbook No. XVII, 1906. Copyrighted by Standard Under- 
ground Cable Company.) 











Volts 










Size in 
















B. &S.G. 


1100 


2200 


3300 


4000 


6600 j 


11000 


13200 | 


22000 




Kilowatts. 


6 


92 


183 


275 


333 


549 


915 


1098 


1831 


5 


109 


217 


326 


395 


652 


1087 


1304 


2174 


4 


130 


260 


390 


473 


781 


1301 


1562 


2603 


3 


154 


309 


463 


562 


927 


1544 


1854 


3089 


2 


179 


358 


536 


650 


1073 


1788 


2145 


3575 


1 


209 


418 


626 


759 


1253 


2088 


2506 


4176 





240 


481 


721 


874 


1442 


2402 


2884 


4805 


00 


279 


558 


836 


1014 


1674 


2788 


3347 


5577 


000 


322 


644 


965 


1172 


1931 


3217 


3862 


6435 


0000 


372 


744 


1115 


1352 


2231 


3717 


4462 


7435 


250000 


413 


827 


1240 


1503 


24S0 


4132 


4960 


8264 





Single Conductor Cables 


, A. C 


. or D 


. C. 












Volts. 








Size in 


















B.&S.G. 


125 


250 


500 


1100 


2200 


3300 


6600 


11000 




Kilowatts. 


6 


8.0 


16.0 


32 


70 


141 


211 


422 


704 


5 


9.5 


19.0 


38 


84 


167 


251 


502 


836 


4 


11.4 


22.8 


45 


100 


200 


300 


601 


1001 


3 


13.5 


27.0 


54 


119 


238 


356 


713 


1188 


2 


15.6 


31.2 


62 


138 


275 


413 


825 


1375 


1 


18.3 


36.5 


73 


161 


321 


482 


964 


1606 





21.0 


42.0 


84 


185 


370 


554 


1109 


1848 


00 


24.4 


48.8 


97 


215 


429 


644 


1287 


2145 


000 


28.1 


56.3 


113 


248 


495 


743 


1485 


2475 


0000 


32.5 


65.0 


130 


286 


572 


858 


1716 


2860 


300000 


40.4 


80.8 


162 


355 


711 


1066 


2132 


3553 


400000 


48.8 


97.5 


195 


429 


858 


1287 


2574 


4290 


500000 


56.3 


112.5 


225 


495 


990 


1485 


2970 


4950 


600000 


63.1 


126.3 


253 


556 


1111 


1667 


3333 


5555 


700000 


69.8 


139.5 


279 


614 


1228 


1841 


3683 


6138 


800000 


75.9 


151.8 


304 


668 


1335 


2003 


4006 


6677 


900000 


81.3 


162.5 


325 


715 


1430 


2145 


4290 


7150 


1000000 


86.9 


173.8 


348 


764 


1529 


2294 


4587 


7645 


1100000 


92.5 


185.0 


370 


814 


1628 


2442 


4884 


8140 


1200000 


97.5 


195.0 


390 


858 


1716 


2574 


5148 


8580 


1400000 


107.1 


214.3 


429 


943 


1885 


2828 


5656 


9427 


1500000 


111.9 


223 . 8 


448 


985 


1969 


2954 


5907 


9845 


1600000 


116.6 


233 3 


467 


1026 


2053 


3079 


6158 


10263 


1700000 


121.3 


242.5 


485 


1067 


2134 


3201 


6402 


10670 


1800000 


126.3 


252.5 


505 


1111 


2222 


3333 


6666 


11110 


2000000 


135.6 


271.3 


543 


1194 


2387 


3581 


7161 


11935 



These tables are based on the recommended current carrying capacity of 
cables given on page 215. A power factor = 1, was used in the calcula- 
tion and hence the values found in the last table are correct for direct 
currents. For alternating currents the kilowatts given in both tables 
must be multiplied by the power factor of the delivered load. 



FUSING EFFECTS OF ELECTRIC CURRENTS. 217 



ftjsiuto effects of electric currents. 

By W. H. Preece, F. R. S. See " Proc. Roy. Soc," vol. xliv., March 15, 1888. 

The Law — /= ad 2 , where /, current ; a, constant ; and d, diameter — 
is strictly followed; and the following are the linal values of the constant 
"a," for the different metals as determined by Mr. Preece : — 

Inches. Centimeters. Millimeters. 

Copper 10,244 2,530 80.0 

Aluminum .... 7,585 1,873 59.2 

Platinum 5,172 1,277 40.4 

German Silver. . . . 5,230 1,292 40.8 

Platinoid 4,750 1,173 37.1 

Iron ....... 3,148 777.4 24.6 

^i n 1 (342 405.5 12.8 

Alloy (lead and tin 2tol) l',318 325.5 10.3 

Lead 1,379 340.6 10.8 



Table Giving- tne Diameters of Wires of Various materi- 
als Wnicn Will Be Fused by a Current of Given 

Strength.— W. H. Preece, F. R. S. d= (LV /3 





Diameter in Inches. 


GO 

- — 


.4 


s . 

in 
3 e 




*4 

02^ 


'do 

"SB 


00 

CO 


I 


rlo6 
*£ 

111 

03 Q 


s 








rill 


511 






5 £ 


111 

^ 8 


1 


0.0021 


0.0026 


0.0033 


0.0033 


0.0035 


0.0047 


0.0072 


0.0083 


0.0081 


2 


0.0034 


0.0041 


0.0053 


0.0053 


0.0056 


0.0074 


0.0113 


0.0132 


0.0128 


3 


0.0044 


0.0054 


0.0070 


0.0069 


0.0074 


0.0097 


0.0149 


0.0173 


0.0168 


4 


0.0053 


0.0065 


0.0084 


0.0084 


0.0089 


0.0117 


0.0181 


0.0210 


0.0203 


5 


0.0062 


0.0076 


0-0098 


0.0097 


0.0104 


0.0136 


0.0210 


0.0243 


0.0236 


10 


0.0098 


0.0120 


0.0155 


0.0154 


0.0164 


0.0216 


0.0334 


0.0386 


0.0375 


15 


0.0129 


0.0158 


0.0203 


0.0202 


0.0215 


0.0283 


0.0437 


0.0506 


0.0491 


20 


0.0156 


0.0191 


0.0246 


0.0245 


0.0261 


0.0343 


0.0529 


0.0613 


0.0595 


25 


0.0181 


0.0222 


0.0286 


0.0284 


0.0303 


0.0398 


0.0614 


0.0711 


0.0690 


30 


0.0205 


0.0250 


0.0323 


0.0320 


0.0342 


0.0450 


0.0694 


0.0803 


0.0779 


35 


0.0227 


0.0277 


0.0358 


0.0356 


0.0379 


0.0498 


0.0769 


0.0890 


0.0864 


40 


0.0248 


0.0303 


0.0391 


0.0388 


0.0414 


0.0545 


0.0840 


0.0973 


0.0944 


45 


0.0268 


0.0328 


0.0423 


0.0420 


0.0448 


0.0589 


0.0909 


0.1052 


0.1021 


50 


0.0288 


0.0352 


0.0454 


0.0450 


0.0480 


0.0632 


0.0975 


0.1129 


0.1095 


60 


0.0325 


0.0397 


0.0513 


0.0509 


0.0542 


0.0714 


0.1101 


0.1275 


0.1237 


70 


0.0360 


0.CM40 


0.0568 


0.0564 


0.0601 


0.0791 


0.1220 


0.1413 


0.1371 


80 


0.0394 


0.0481 


0.0621 


0.0616 


0.0657 


0.0864 


0.1334 


0.1544 


0.1499 


90 


0.0426 


0.0520 


0.0672 


0.0667 


0.0711 


0.0935 


0.1443 


0.1671 


0.1621 


100. 


0.0457 


0.0558 


0.0720 


0.0715 


0.0762 


0.1003 


0.1548 


0.1792 


0.1739 


120 


0.0516 


0.0630 


0.0814 


0.0808 


0.0861 


0.1133 


0.1748 


0.2024 


0.1964 


140 


0.0572 


0.0698 


0.0902 


0.0895 


0.0954 


0.1255 


0.1937 


0.2243 


0.2176 


160 


0.0625 


0.0763 


0.0986 


0.0978 


0.1043 


0.1372 


0.2118 


0.2452 


0.2379 


180 


0.0676 


0.0826 


0.1066 


0.1058 


0.1128 


0.1484 


0.2291 


0.2652 


0.2573 


200 


0.0725 


0.0886 


0.1144 


0.1135 


0.1210 


0.1592 


0.2457 


0.2845 


0.2760 


225 


0.0784 


0.0958 


0.1237 


0.1228 


0.1309 


0.1722 


0.2658 


0.3077 


0.2986 


250 


0.0841 


0.1028 


0.1327 


0.1317 


0.1404 


0.1848 


0.2851 


0.3301 


0.3203 


275 


0.0897 


0.1095 


0.1414 


0.1404 


0.1497 


0.1969 


0.3038 


0.3518 


0.3413 


300 


0.0950 


0.1161 


0.1498 


0.1487 


0.1586 


0.2086 


0.3220 


0.3728 


0.3617 



218 PROPERTIES OF CONDUCTORS. 

Ti:\MO\ 4VD SAO IJ¥ WIHE SPAM. 

By Harold Pender, Ph.D. 

The accompanying charts* (No. 1 for long spans, No. 2 for short spans) 
enable one to determine without arithmetical computation the variation 
of the tension and sag in copper wire spans with the temperature and resul- 
tant load on the wire. Similar charts can be readily prepared for wires of 
any material. 

The symbols used in the discussion below are as follows: 

m = weight of wire per cubic inch in pounds. 
a = coefficient of linear expansion of wire per degree Faljr. 
M = modulus of elasticity of wire (pounds — square inch). 
p = ratio of resultant of the weight of wire, the weight of sleet and the 

wind pressure to the weight of wire. 
I = length of span in feet. 
t = rise in temperature in degrees Fahr. 
T — tension in thousands of pounds per square inch. 
D = deflection at center of span in feet in direction of resultant force when 

points of suspension are on the same level. 
S — vertical sag at center of span in feet when points of support are on 
the same level. 

The lines on the charts are plotted as follows: 

The hyperbolic curves on the right have the equation y = (~J where y 

is the ordinate and T the abscissa. A curve is plotted for p = 1.0, 1.2, 
1.4 . . . 4.0. The value of p for each curve is indicated at the top of the 
chart. It is to be noted that the horizontal distance between these curves 
at any level is directly proportional to the increment in the value of p. 
These curves are independent of the material of the wire. 

10° 
The inclined straight lines have the equation y = ^-r^ — — T. For a 

given material the equation of these lines depends only on the length of the 
span. The lines on the charts are drawn for copper wire for which m = 
0.321 and M = 12 X 10 6 . The corresponding length of span is indicated 
on the right-hand margin of the charts. For any other material, the line 
for a given length of span will have a different slope. 

The temperature scale on the X axis to the right of the origin is laid off 
so that x = Ma t. The scale given on the chart is for copper, for which 
M = 12 X 10 6 and o = 9.6 X 10"*. This scale will be different for any 
other material. 

The parabolic curves on the left of the chart have the equation D = 0.0015 
m I 2 Vy, where D is measured off from the left of the origin. For a given 
material these curves are fixed by the length of the span. The curves 
given on the chart are for copper, for which m = 0.321. The correspond- 
ing lengths of span are indicated on the curves. These curves will be 
different for any other material. 

Rules for the "Use of the Charts. 

Given: A span of length I and the points of support on the same level, 
tension I\; ratio of resultant force to weight of wire, pi; to find the tension 
T when the temperature rises t degrees and the ratio of resultant force to 
weight of wire changes to p (for example, sleet melts off). 

At the point 1 (Fig. 27) on the curve corresponding to pi and having 
the abscissa 7\ f lay off 12 = the ordinate of the point 3 on the line corre- 
sponding to I having the abscissa t on the temperature scale. 

* These charts were devised to obtain a graphical solution of the equa- 
tions deduced by the author in an article in the Electrical World for Jan. 
12, 1907, Vol. 49, p. 99. The present article also appeared in the Electrical 
World for Sept. 28, 1907. 



WIRE SPANS. 



219 



Through 2 draw a line parallel to the line I : the abscissa of the point 4 
where this line cuts the curve corresponding to p is the tension T at the 
temperature t when the ratio of resultant force to weight of wire is p. The 
abscissa of the point 5 where the horizontal line through 4 cuts the para- 
bolic curve corresponding to I gives the corresponding deflection D at the 
center of the span in feet. Instead of actually drawing the straight line 
24, a pair of compasses may be used; i.e., lay off the distance 12, then open 
the compasses until the lower point touches the straight line Z; then keep- 
ing the compasses vertical, slide the lower point along I until the upper 
point intersects the curve corresponding to p. If t is negative, i.e., if the 
temperature decreases, lay off 12 in the opposite direction. To determine 
D with greater accuracy use the formula 

D = .0015 ml? 9 -' 




Fig. 25. 



Calculation of p. 

Let w = weight of wire in pounds per foot. 

The weight of sleet (and hemp core, if any) in pounds per foot of wire is 



Wt 



0.314 (dj - d 2 ) + 0.25 do 2 , 



where d is the diameter of the wire, d\ the diameter over sleet and do the 
diameter of the core, all in inches. 

The wind pressure in pounds per foot of wire is * 

w 2 = 0.00021 V 2 d u 

where V is the actual wind velocity in miles per hour; d x = d in case of no 
sleet. The relation between indicated wind velocity (as given by U. S. 
Weather Reports) and actual velocity is as follows: 



Indicated Velocity. 




Actual Velocity. 


0.00021 VK 


10 






9.6 


0.0194 


20 






17.8 


0.0667 


30 






25.7 


0.139 


40 






33.3 


0.233 


50 






40.8 


0.350 


60 






48.0 


0.485 


70 






55.2 


0.640 


80 






62.2 


0.812 


90 






69.2 


1.01 


100 






76.2 


1.22 • 


The ratio p is then 










P 


-/c 


4- 


wA 2 /VA 2 

0)/ \(0 / 





* H. W. Buck in Transactions International Electrical Congress, 1904. 



220 



PROPERTIES OF CONDUCTORS. 




WIRE SPANS. 



221 




222 PROPERTIES OF CONDUCTORS. 



Calculation of Vertical Sag 1 . 

In case of no wind the vertical sag S is the same as the deflection D. 
The wind pressure gives a horizontal component to the resultant force so 
that the vertical sag when wind is blowing is, 



S - 



•■ ♦ tw 



Example: A No. 00 stranded copper cable is to be strung in still air 
at 70° F. between two points on the same level 800 feet apart, so that at a 
temperature of zero degrees Fahrenheit, with a coating of sleet 0.41 inch thick 
all around and wind blowing perpendicularly to the cable at 69.5 miles an 
hour (actual velocity) the tension in the cable will be 30,000 lbs. per sq. 
in.; (1) at what tension must the cable be strung and (2) what will be the 
vertical sag at stringing temperature, i.e., 70°, also (3) what will be the sag 
at zero temperature when the cable is coated with i-in. of sleet and wind 
is blowing with a velocity of 65 miles an hour, and (4) what will be the sag 
at the temperature of 150°, in the still air? 



We have 



w= 0.406 



w 1 =0.314 (1.2382 -0.418 2 ) =0.425 
w 2 = .00021 + 69.52 + 1 . 238 = 1 . 26. 

Therefore, at zero degrees with wind and sleet, 

(1) Measure off with compasses, on chart No. 1, the vertical distance 
from t = 70 on X axis to the straight line corresponding to I = 800. Lay 
this distance off vertically above the point on the curve corresponding to 
p = 3.72 having the abscissa T = 30. Keep the upper point fixed, open the 
compasses until the lower point touches the line I = 800; then, keeping the 
compasses vertical, slide the lower point along the line I = 800 until the upper 
point intersects the curve p = 1 at T = 8.95; the cable must therefore be 
strung at a tension of 8950 lbs. per sq. in. (2) The abscissa of the point 
on the parabolic curve I = 800, having the same ordinate as the point 
corresponding to p = 1 and T = 8.95 is D = 34.4 feet, which is the vertical 
sag S, in still air at 70° F. 

(3) The deflection at zero degrees with sleet and wind is the abscissa 
of the point on the parabolic curve I = 800 having the same ordinate as 
the point corresponding to p = 3.72 and T = 30, i.e., D = 38.2 feet. 

The vertical sag is 

= 21.(Heet. 



^ * git 

(4) To find the sag at 150° proceed as under (1) and (2) taking t = 150. 
The sag will be found to be S = 36.8 feet. 



WIRE SPANS. 223 



Were Suspended from Points not on the Sanie Level. 

The charts also apply directly to the determination of the change in 
tension in spans when the points of support are at different heights. In 
this case, however, the vertical sag Si ( — deflection in case of no wind) 
below the highest point of support is given by the formula 



S ^ s ( l + Ts)" 



where h is the difference in height of the two points of support, and S is the 
vertical sag for a span of equal length, but points of support on the same 
level; S is calculated by the formula given above, i.e., 

D 



J, + (_a_y 

D being the deflection, taken directly from the chart, for a span of equal 
length but points of support on the same level; in case of no wind S = D. 
The distance of the point of maximum sag from the highest point of support 
is 



2 V + 4 Sj 



When h is greater than 4 S the lowest point of support is the point of max- 
imum sag, i.e., the lowest point in the span. 

Example: In the example given above, suppose the difference in height 
of the points of support is 20 feet : Then (1) the tension at 70° will still be 
8950 lbs. per sq. in. (2) The corresponding vertical sag at 70° in still 
air for points of support at same level is 34.4 ft., therefore, for the span 
under consideration the vertical sag from the highest point of support is 

(20 \ 2 

(3) The vertical sag at zero degrees with sleet and wind for points of 
support on the same level is 21 ft.; therefore, for a 20-ft. difference in the 
height of points of support the vertical sag from the highest point of sup- 
port is 



21 ( 1+ 4f2i) 2 = 321ft - 

(4) The vertical sag at a temperature of 150°, for points of support on 
the same level is 36.8 ft.; therefore, for a 20-ft. difference in height of the 
points of support the vertical sag from the highest point of support is 

36 - 8 ( 1 + orW= 47 - 5ft - 

The accompanying table, giving the value of T and p for various values 

of y = f J;) will be found useful in plotting the hyperbolic curves in case one 

wishes to make charts on a larger scale than those given herein, or similar 
charts for wires having different constants. The other lines are readily 
plotted from the equations given above. 



224 



PROPERTIES OF CONDUCTORS. 



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8 8 8 8 8 8 8 § § 1 1 8 § 







Circular Mils 



Fig. 28. — The top boundary of each span diagram is drawn for conditions 
at 100° Fahr.; the bottom boundary line for 0°. For other temperatures, 
interpolate or exterpolate proportionately. For mechanical reasons it is 
not recommended to string larger sizes of wire than appear in any closed 
span diagram, with any less sag than the minimum shown therein. The 
values of constants and assumptions of weather conditions are open to 
criticism. No responsibility is assumed beyond the correctness of the 
arithmetic. 

Assumptions. — Maximum stress at - 20° = 14,000 lbs. Ice coating one-half 
inch thick. Wind pressure 10 lbs. per sq.ft. proj. Diam. Diam. stranded 
conductor = 1.15 that of a solid wire of same section, Modulus of Elas- 
ticity = 7,500,000. 



226 



PROPERTIES OF CONDUCTORS. 



Deflections in Feet of Stranded Aluminum Wire in 
Still Air. 

H. W. Buck. 

Wire strung so that the maximum tension at minimum temperature of 
0° F with wind blowing at 65 miles per hour (actual velocity) will be 14,000 
lbs. per square inch. 



Span in 


Area 

of Wire 


Degrees Fahrenheit Rise above Minimum Temperature. 


Feet 


in Cir. 
Mils. 






0° 


20° 


40° 


60° 


80° 


100° 


120° 


140° 


150° 


200 


553,150 
265,400 
132,300 


.42 
.45 
.46 


.51 
.52 
.55 


.65 
.65 
.69 


.83 

.85 
.92 


1.07 
1.13 
1.30 


1.57 
1.65 
1.82 


2.20 
2.27 
2.45 


2.75 
2.80 
2.95 


2.97 
3.03 
3.10 


400 


553,150 
265,400 
132,300 


1.80 
1.95 
2.20 


2.20 
2.42 
2.75 


2.70 
2.90 
3.40 


3.35 
3.70 
4.20 


4.15 
4.50 
5.10 


5.05 
5.45 
6.00 


6.00 
6.40 
7.00 


6.90 
7.35 

7.85 


7.20 

7.78 
8.50 


600 


553,150 
265,400 
132,300 


4.3 
5.1 
6.2 


5.1 
6.1 
7.2 


6.0 

7.1 
8.4 


7.0 
8.2 
9.7 


8.2 

9.5 

11.0 


9.5 

10.8 
12.2 


10.8 
12.0 
13.3 


11.9 
13.1 
14.4 


12.5 
13.6 
15.7 


800 


553,150 
265,400 
132,300 


8.4 
10.3 
14.0 


9.5 

11.7 
15.4 


10.8 
13.2 
16.9 


12.3 
14.7 
18.3 


13.8 
16.4 
19.6 


15.4 
17.7 
29.0 


16.9 
19.1 
22.2 


18.3 
20.4 
23.4 


19.0 
21.5 
25.5 


1000 


553,150 
265,400 
132,300 


13.9 
18.6 
26.0 


15.6 
20.3 
27.6 


17.3 
22.0 
29.0 


19.1 
23.8 
30.5 


20.8 
25.5 
31.8 


22.5 
27.1 
33.1 


24.2 
28.6 
34.4 


25.9 
30.0 
35.8 


26.7 
31.5 
37.5 



Deflections in Incites of Stranded Aluminum Wire in 
Still Air. 

H. W. Buck. 
Wire strung so that the maximum tension at minimum temperature of 
0° F with wind blowing at 65 miles per hour (actual velocity) will be 14,000 
lbs. per square inch. 

Calculations made for No. 2 B. and S. stranded conductor, but it is safe 
to follow this table for all sizes of cable, for the larger sizes will have 
slightly smaller deflections without exceeding their elastic limit on account 
of their greater relative strength. 



Degrees 














Fahren- 




Length of Span in Feet 






heit Rise 














above 














Minimum 
Temp. 


200 


180 


160 


140 


120 


100 





6.3 


5.3 


4.2 


3.1 


2.2 


1.7 


10 


7.0 


5.7 


4.5 


3.4 


2.4 


1.8 


20 


7.8 


6.4 


5.1 


3.8 


2.8 


1.9 


30 


8.8 


7.3 


5.8 


4.5 


3.2 


2.2 


40 


10.2 


8.4 


6.7 


5.2 


3.8 


2.7 


50 


12.0 


9.8 


7.8 


6.4 


4.6 


3.3 


60 


14.0 


11.5 


9.4 


7.5 


5.6 


4.0 


70 


16.5 


14.0 


11.5 


9.2 


7.0 


5.2 


80 


19.8 


17.0 


14.3 


11.4 


8.9 


6.8 


90 


23.1 


20.0 


16.8 


13.8 


10.3 


8.8 


100 


26.6 


23.3 


20.0 


16.6 


13.1 


10.8 


110 


29.8 


26.6 


23.0 


19.5 


16.5 


13.1 


120 


33.5 


29.8 


25.8 


22.2 


18.7 


15.2 


130 


36.8 


32.8 


28.7 


24.5 


20.8 


17.2 


140 


40.0 


35.8 


31.5 


26.8 


22.8 


18.8 


150 


43.0 


38.4 


33.6 


29.1 


24.8 


20.3 



DIELECTRICS. 



227 



PROPERTIES OF DIELECTRICS. 

Approximate Values of Specific Inductive Capacity of 
Various Dielectrics. 

Non-conducting materials or insulators are called dielectrics. The di- 
electric constant or specific inductive capacity of a dielectric is the ratio 
of the capacity of a condenser having the space between its plates filled 
with this substance to the capacity of the same condenser with this space 
filled with air. 

All gases and vacuum 1 . 00 

Glass 3 to 8 

Treated paper used in manufacture of power cables 2 to 4 

Porcelain 4.4 

Ebonite 2.5 

Gutta-percha 2.5 

Pure Para Rubber 2.2 

Vulcanized Rubber 2.5 

Paraffin 2.3 

Rosin 1.8 

Pitch 1.8 

Wax 1.6 

Mica 6 

Water 80 

Turpentine oil 2.2 

Petroleum 2 



Specific Resistance of Dielectrics at about 20° C. 

These are approximate values; the resistance of dielectrics varies greatly 
with their purity and method of preparation. 



Material. 



Benzine 

Ebonite 

Glass, flint 

Glass, ordinary 

Gutta-percha 

Mica 

Micanite 

Micanite cloth 

Micanite paper 

Oil asbestos 

Olive oil 

Ozokerite (crude) 

Paper, parchment 

Paper, ordinary 

Treated paper used in manufacture of power 

cables 

Paraffin 

Paraffin oil 

Shellac 

Vulcanized fiber, black 

Vulcanized fiber, red 

Vulcanized fiber, white . 

Wood, ordinary 

Wood, paraffined 

Wood, tar 

Wood, walnut . . 



Resistance in 


Resistance 


Millions of 


in Millions 


Megohms per 


of Meg- 


Cubic Centi- 


ohms per 


meter. 


Cubic Inch. 


14 


5.22 


28,000 


11,000 


20,000 


8,000 


90 


36 


450 


180 


80 


30 


2,500 


900 


300 


120 


1,200 


500 


850 


315 


1 


0.4 


450 


180 


0.03 


0.01 


0.05 


0.02 


10 to 20 


4 to 8 


24,000 


13,000 


8 


3 


9,000 


3,500 


68 


27 


10 


4 


14 


6 


600 


250 


3,700 


1,500 


1,700 


670 


50 


20 



228 PROPERTIES OF CONDUCTORS. 



Variation of Resistance with Temperature. 

The variations in resistance of dielectrics with temperature is much more 
rapid than in the case of metals. The variation can be expressed by an 
exponential equation. 

Ro — Rji . 

Where Rq = resistance at standard temperature. 

R t — resistance at temperature differing t degrees from standard 
temperature. 
t = temperature. 
a = constant depending on the material. 

For gutta-percha, t in ° C a = 0.88 

For pure rubber, t in ° C a = 0.95 

For other substances, the processes of manufacture vary too widely to 
permit the establishment of temperature coefficients. 



Dielectric Strength of Insulating: Materials. 

C. KlNZBRUNNER. 

Let V = Voltage required to puncture a given thickness of material. 

v = Volts required to puncture a sheet of material .001 inch thick. 
t = Thickness of the material in thousandths of an inch. 

For all the materials given in table below, except pure para, 

For pure para, 

For all the materials given below, except ordinary paper and impreg- 
nated paper, the puncturing voltage is the same for a solid sheet of material 
as for a sheet built up of thin layers. In the case of ordinary paper and 
impregnated paper the puncturing voltage is proportional to the number 
of layers; i.e., V = nnVf, where n is the number of layers and V the 
thickness of each layer. 

Puncturing Voltages for Sheet .001 in. thick (v.) 

Presspahn 117 

Manila paper 56 

Ordinary paper 37 

Fiber 57 

Varnished paper 267 

Red Rope paper 239 

Impregnated paper 107 

Varnished linen 256 

Empire cloth 201 

Leatheroid 73 

Ebonite 682 

Rubber 502 

Gutta-percha 454 

Para 370 



DIELECTRICS. 229 

The values in the preceding table are for tests made under the follow- 
ing conditions: 

1. Electrodes, flat disks with round edges 1.5 inches in diameter. 

2. Pressure on electrodes 0.5 pounds per square inch. 

3. Voltage curve sinusoidal. 

4. Frequency of the alternating current between 20 and 75 cycles per 

second. 

5. Temperature 17° C, humidity of the air about 70 per Gent. 

6. Pressure applied for 15 minutes. 

Rubber. 

Pure rubber is a liquid gum having a specific gravity of .915. The 
rubber of commerce is obtained by coagulating this gum by various means, 
the most approved method being by the hot vapor rising from a smudge 
made from oily nuts. Rubbers prepared in this way are called "Para" 
rubbers; Para is the name of a province of Brazil which supplies a large 
quantity of this kind of rubber. Vulcanized rubber is a mixture of this 
coagulated gum, thoroughly cleaned and dried, with sulphur. Pure rubber 
deteriorates rapidly, whereas vulcanized rubber is comparatively stable, 
and at the same time retains the properties which make it valuable as an 
insulating material. The amount of sulphur present varies from five 
to twenty per cent of the entire mass, the amount determining the hardness 
of the product. Rubber with a large admixture of sulphur is called vari- 
ously "hard rubber," "vulcanite" or "ebonite." Vulcanized rubber is 
used largely for insulating cables of all kinds. 

Specification* for 30% Rubber Insulating: Compound. 

Adopted 1906, by the following wire manufacturers: 

American Steel & Wire Co. Indiana Rubber & Ins. Wire Co. 

American Electrical Works. National India Rubber Co. 

Bishop Gutta Percha Co. New York Ins. Wire Co. 

Canadian Gen. Electric Co. John A. Roebling's Sons Co. 

Crescent Ins. Wire & Cable Co. Safety Ins. Wire & Cable Co. 

General Electric Co. Simplex Electrical Co. 

Hazard Mfg. Co. Standard Underground Cable Co. 
India Rubber & Gutta Percha Ins. Co. 

The compound shall contain not less than 30% by weight of fine dry 
Para rubber which has not previously been used in rubber compounds. 
The composition of the remaining 70% shall be left to the discretion of the 
manufacturer. 

Chemical. — The vulcanized rubber compound shall contain not more 
than 6% by weight of Acetone Extract. For this determination, the 
Acetone extraction shall be carried on for five hours in a Soxhlet extractor, 
as improved by Dr. C. O. Weber. 

mechanical. — The rubber insulation shall be homogeneous in char- 
acter, shall be placed concentrically about the conductor, and shall have a 
tensile strength of not less than 800 pounds per square inch. 

A sample of vulcanized rubber compound, not less than four inches in 
length shall be cut from the wire, with a sharp knife held tangent to the 
copper. Marks should be placed on the sample two inches apart. The 
sample shall be stretched until the marks are six inches apart and then 
immediately released; one minute after such release, the marks shall not be 
over 2| inches apart. The samples shall then be stretched until the marks 
are 9 inches apart before breaking. 

For the purpose of these tests, care must be used in cutting to obtain a 
proper sample, and the manufacturer shall not be responsible for results 
obtained from samples imperfectly cut. 

Electrical. — Each and every length of conductor shall comply with 
the requirements given in the following table. The tests shall be made at 
the Works of the Manufacturer when the conductor is covered with vulcan- 
ized rubber, and before the application of other coverings than tape or braid. 



230 



PROPERTIES OF CONDUCTORS. 



Tests shall be made after at least twelve hours' submersion in water and 
while still immersed. The voltage specified shall be applied for five minutes. 
The insulation test shall follow the voltage test, shall be made with a battery 
of not less than 100 nor more than 500 volts, and the reading shall be taken 
after one minute's electrification. Where tests for acceptance are made by 
the purchaser on his own premises, such tests shall be made within ten days 
of receipt of wire of cable by purchaser. 

Inspection. — The purchaser may send to the works of the manufacturer 
a representative, who shall be afforded all necessary facilities to make the 
above specified electrical and mechanical tests, and, also, to assure himself 
that the 30% of rubber above specified is actually put into the compound, 
but he shall not be privileged to inquire what ingredients are used to make 
up the remaining 70% of the compound. 



30% Rubber Compound 'Voltage Test for 5 HEinutes. 

For 30 Minutes Test, Take 80% of These Figures. 
I. 



Size. 


Thickness of Insulation in Inches. 


A 


2 
32 


5 
64 


3 

32 


A 


A 


1,000,000 to 550,000 . 










4,000 

6,000 

8,000 

10,000 

11,000 


6,000 


500,000 to 250,000 . 








4,000 
6,000 
8,000 
9,000 


8,000 


4/0 to 1 

2 to 7 

8 to 14 


3,666 


'4,666 

5,000 


4,000 
6,000 
7,000 


10,000 
12,000 
13,000 



II. 





Thickness of Insulation in Inches. 




A 


A 


A 


A 


A 


10 
"3"? 


1,000,000 to 550,000 . 
500,000 to 250,000 . 

4/0 to 1 

2 to 7 

8 to 14 


10,000 
12,000 
14,000 
16,000 
17,000 


14,000 
16,000 
18,000 
20,000 
21,000 


18,000 
20 000 
22,000 
24,000 
25,000 


22,000 
24,000 
26 000 
28,000 


26,000 
28,000 
30,000 
32,000 


30,000 
32,000 
34,000 
36 000 











DIELECTRICS. 



231 



HEegpoIims per iflile GO Degrees F. 

One Minute Electrification. 



1000000 C. M. 
900000 C. M. 
800000 C. M. 
700000 C. M. 
600000 C M. 
500000 C. M. 
400000 C. M. 
300000 C. M. 
250000 C. M. 

4/0 Strd. 

3/0 Strd. 

2/0 Strd. 

1/0 Strd. 

1 Solid 

2 Solid 

3 Solid 

4 Solid 

5 Solid 
G Solid 
S Solid 
9 Solid 

10 Solid 
12 Solid 
14 Solid 





A 


A 


A 


A 


A 










200 












235 












270 












305 












C40 










350 


375 










390 


420 










430 


470 










455 


500 






', 


L40 


480 


520 






4 


150 


490 


535 






4 


L60 


500 


545 






t 


190 


540 


590 






i 


>20 


530 


635 




. 


>66 \ 


>50 


615 


680 




i 


>30 l 


>85 


650 


715 




i 


K0 ( 


)20 


690 


750 




i 


yjQ ( 


355 


720 


790 




\\ e 


J20 ( 


390 


760 


840 


610 \ 


no i 


300 


880 


985 


650 ' 


rso i 


350 


940 


1050 


690 ' 


705 ! 


305 


1000 


1120 


750 \ 


370 i 


)90 


1110 


1250 


\ 


300 < 


)30 1< 


360 


1200 


1340 



210 
250 
290 
325 
365 
405 
450 
505 
540 
565 
580 
590 
650 
700 
750 
795 
830 
870 
920 
1060 
1130 
1200 
1370 
1470 



A 



235 
280 
325 
370 
420 
465 
530 
590 
630 
660 
675 
690 
760 
830 
900 
940 
990 
1040 
1100 
1240 
1310 
1380 
1540 
1640 



265 
315 
370 
420 
470 
525 
600 
680 
720 
750 
770 
790 
860 
950 
1040 
1080 
1130 
1180 
1230 
1370 
1440 
1510 
1680 
1780 



32 



300 
360 
420 
480 
540 
600 
670 
750 
810 
840 
860 
880 
950 
1060 
1160 
1210 
1260 
1300 
1350 
1490 
1560 
1620 
1790 
1890 



Crutta-JPercha. 

A higher grade of insulating material is another gum, gutta-percha, 
which is used in its pure state. The use of this gum is confined almost 
entirely to the construction of the insulated core of submarine cables. 

Specific gravity, 0.9693 to 0.981. 

Weight per cubic foot, 60.56 to 61.32 pounds. 

Weight per cubic inch, 0.560 to 0.567 oz. 

Softens at 115 degrees F. 

Becomes plastic at 120 degrees F. 

Meltc at 212 degrees F. ' . 

Oxidizes and becomes brittle, shrinks and cracks when exposed to the air, 
especially at temperatures between 70 and 90 degrees F. 

Oxidation is hastened by exposure to light. 

Oxidation may be delayed by covering the gutta-percha insulation with a 
tape wnich has been soaked in prepared Stockholm tar. 

Where gutta-percha is kept continually under water there is no notice- 
able deterioration, and the same applies where gutta-percha leads are cov- 
ered with lead tubing. , 

Stretched gutta-percha, such as is used for insulating cables, will stand 
a strain of 1,000 pounds per square inch before any elongation. 

The breaking strain is about 3,500 pounds per square inch. 

The tenacity of gutta-percha is increased by stretching it. 

Resistance of Gatta-Percha under Pressure. — The resistance 
of gutta-percha under pressure increases according to the following formula, 
when R = the resistance at the pressure of the atmosphere, and r the resis- 
tance at p pounds per square inch. 

r = R (1 -1- 0.00023 p). 



232 



PROPERTIES OF CONDUCTORS. 



Let D = diameter in mils of over gutta-percha insulation. 
d — diameter of cable core. 

W = weight in pounds of gutta-percha per knot. 
w = weight in pounds of copper. 



Then for Solid Cable 



For Stranded Cables. 



D - V55W-J-49I W. 



5-V 



w 

1 -f- 8.93 - • 
w 



D = V70Aw+491 W 



i-V 



1 + 6.97 



W 



Approximate Electrostatic Capacity of a gutta-percha cable per knot is 

: ^r - : — : ■ microfarads. 

log D — log d 

The electrostatic capacity of a gutta-percha insulated cable compared with 
one of the same size insulated with india rubber is about as 120 is to 100. 



Dividing- Coefficients for Correcting- tite observed Resist- 
ance of Cirutta-PercUa at any Temperature to 95° Jk\ 

K. WlNNERTZ 1907. 



Degree F. 


Coefficient. 


Degree F. 


Coefficient. 


Degree F. 


Coefficient. 


95 


0.1415 


74 


1.089 


53 


6.015 


94 


0.1561 


73 


1.187 


52 


6.373 


93 


0.1721 


72 


1.293 


51 


6.722 


92 


0.1898 


71 


1.409 


50 


7.057 


91 


0.2105 


70 


1.535 


49 


7.377 


90 


0.2332 


69 


1.672 


48 


7.670 


89 


0.2574 


68 


1.821 


47 


7.943 


88 


0.2836 


67 


1.984 


46 


8.178 


87 


0.3125 


66 


2.161 


45 


8.383 


86 


0.3442 


65 


2.353 


44 


8.499 


85 


0.3833 


64 


2.562 


43 


8.585 


84 


0.4304 


63 


2.790 


42 


8.637 


83 


0.4801 


62 


3.035 


41 


8.678 


82 


0.5251 


61 


3.302 


40 


8.719 


81 


0.5848 


60 


3.588 


39 


8.757 


80 


0.6458 


59 


3.896 


38 


8.796 


79 


0.7066 


58 


4.223 


37 


8.834 


78 


0.7707 


57 


4.564 


36 


8.880 


77 


0.8406 


56 


4.919 


35 


8.932 


76 


0.9168 


55 


5.282 


34 


8.990 


75 


1.0000 


54 


5.650 


33 


9.053 



DIELECTRICS. 



233 



Dielectric Strength of Air. 

The voltage required to break down the air between two terminals de- 
pends on the shape of the terminals, the distance between the terminals, 
and the constants of the circuit in series with the terminals. 

The following curves, published by Mr. S. M. Kintner in the proceedings 
of the American Institute of Electrical Engineers, give the voltage re- 
quired to break down air gaps of various lengths under various conditions. 



75 
70 
65 
GO 
55 
50 

2 45 

O 
| W 

30 
25 
20 
15 
10 
5 














































































n. 






































in 








































^X 


































































IV 














































































































$ 


r 












































NEEDLE POINT SPAKK GAP CURVE 

I A.I.E.E. Curve 

q II Water Uheostat in Gap Circuit 

.4.111 Small Condenser 

IV Two Small Condensers in Gap Circuit 

• V Gap Shielded with 8 7 Disc 
















































/ 





















































































































2 Inches 3 
Fig. 29. 



With regard to the use of a spark gap for measuring high voltages, Mr. 
Kintner makes the following recommendations: 

"For the measurement of sudden pressure variations, such as those pro- 
duced on transmission lines by lightning, switching, grounds, short cir- 
cuits, etc., where the use of an oscillograph or similar device is not feasible, 
the spark-gap method is very useful. It is, in fact, the only method by 
which any satisfactory quantitative results can be obtained under such 
conditions. 

"When using a gap the writer prefers * round nose' (hemispherical 
shielded terminals); (slightly concave shields placed back of and coaxial with 
the terminals) ; the gap shouid be standardized over the range for which it 
is to be used just prior to taking measurements, and under as nearly the 
same surroundings, connections, etc., as possible. This preference is based 
on the convenience of operation and greater freedom from erratic behavior 
of this form of gap. 

"The spark gap, although apparently a very simple device, requires an 
expert operator to get results that are at all satisfactory." 



234 



PROPERTIES OF CONDUCTORS. 



70 
65 


















in 


ii 
















































































































































55 










IV 
































50 










































O 40 

O 

a 35 

s 




















CURVES OF JUMP DISTANCES 
Shielded Gaps. ^''Noses 6"Shields Placed 
%"Back of Terminals 
$ I Normal Gap 

O II Voltmeter Resistance in Gap Circuit 
e III Water Resistance >> >> " 
• IV Small Condenser »» " »« 








































30 




$ 
















25 
20 
15 
10 


J 


7 






































/ 








































I 








































1 








































5 













































3 4 

©ap Distances in Inches 
Fig. 30. 



.Puncturing- Voltage of Iflica in Transil Oil. 

W. S. Andrews. 



Thickness of 


Average Punc- 


Thickness of 


Average Punc- 


Mica. 


turing Voltage. 


Mica. 


turing Voltage. 


.00 1" 


3,800 


.006" 


6,700 


.0015" 


4,500 


.0065" 


6.930 


.002" 


4,600 


.007" 


7,220 


.0025" 


4,750 


.0075" 


7,400 


.003" 


5,300 


.008" 


7,700 


.004" 


5,570 


.0085" 


8,550 


.00475" 


5,950 


.01" 


8,900 


.005" 


6,050 







Specific Thermal Conductivity of Dielectrics. 

Watts Through Inch Cube. Temperature Gradient 1° C. 





Specific 




Specific 


Name of Substance. 


Conduc- 


Name of Substance. 


Conduc- 




tivity. 
.0006 




tivity. 


Air 






Vulcanized Rubber . . 


.00105 


Glass 


.0053 


Beeswax 


.00093 


Wood 


.032 


Felt 


.00093 
.00089 


Caoutchouc 

Gutta-percha .... 


.0044 


Vulcanite 


.0051 


Cotton Wool 


.00046 


Sandy Loam .... 


.085 


Sawdust 


.00131 


Bricks and Cement 


.032 


Sand 


.00140 


India Rubber .... 


.0043 


Paraffin 


.00121 


Sand with Air Spaces 


.96 



DIELECTRICS. 



235 



minimum Size of Conductors for Hig-Ii Tension 
Transmission. 

The loss of energy in a high tension transmission line due to the brush 
discharge from the wires depends on the electric pressure, the size of the 
conductors and the atmospheric temperature and barometric pressure. 
For any given size of conductor a certain critical electric pressure exists for 
which there is a sudden rise in the curve of "loss between wires." Con- 
ductors should never be used in practice so small that the operating pres- 
sure is greater than this critical pressure. Mr. H. J. Ryan has deduced 
the following table, giving the minimum size of conductor which should be 
used for pressures from 50,000 to 250,000 volts for a distance between con- 
ductors of 48 inches: 



Operating Pressure; 


Minimum Diameter 


90 per cent of Critical 
Effective Volts. 


of Conductor in 


Inches. 


50,000 


0.058 


75,000 


0.106 


100,000 


0.192 


150,000 


0.430 


200,000 


0.710 


250,000 


0.990 



The equation showing the relation between the maximum value of the 
pressure wave, the atmospheric temperature and barometric pressure, the 
distance between the line conductors and the radius of the conductors 
for conductors larger than No. 4 B. and S. gauge is as follows: 



where 



E= 



E 



17.946 
459 + t 



X 350,000 



log*) (f) 



(r + .07) 



critical pressure at which the sudden increase in the 
brush discharge takes place, 
r = radius of conductors in inches. 
s = distance between conductors from center to center in 

inches. 
t = atmospheric temperature in degrees Fahrenheit. 
b = barometric pressure in inches of mercury. 



PROPERTIES OP CONDUCTORS CARRYING 
ALTERNATING- CURRENTS. 

Ke vised by Harold Pender, Ph.D. * 

Besides the ohmic resistance of a wire, the following phenomena affect 
the flow of an alternating current: 

Skin effect, a retardation of the current due to the property of alter- 
nating currents apparently flowing along the outer surface or shell of the 
conductor, thus not making use of the full area. 

Inductive effects, (a) self induction of the current due to its alternations, 
inducing a counter E.M.F. in the conductor; and (6) mutual inductance, or 
the effect of other alternating current circuits. 

Capacity effects, due to the fact that all lines or conductors act as elec- 
trical condensers, which are alternately charged and discharged with the 
fluctuations of the E.M.F. 



ErFECTIVE RE§I§TAl¥€E~§KI]y EITECT. 

The effective resistance of a circuit to an alternating current depends 
on the shape of the circuit, the specific resistance, permeability, cross 
section and shape of the conductor, and the frequency of the current. The 
current density over the cross section of the conductor is a minimum at 
the center, increasing to a maximum at the periphery; in a solid conductor 
of large cross section the current is confined almost entirely to an outer 
shell or •'skin." The "Skin Effect Factor" is the number by which the re- 
sistance of the circuit to a continuous current must be multiplied to give 
the effective resistance to an alternating current. The following curve, 
formulae and table give the "Skin Effect Factor" for a straight wire of 
circular cross section, the return wire of the circuit being assumed suffi- 
ciently remote to be without effect, which is practically the case in an 
aerial transmission line. 

Let R = Resistance of wire in ohms to a continuous current. 

R' = Effective resistance of wire in ohms to an alternating current. 
/ = Cycles per second. 
A = Cross section of wire in circular mil3. 
ix == Permeability of wire in C.G.S. units. 
t = Temperature in °C. 
a = Temperature coefficient per °C. 

C = Percentage conductivity of wire referred to Matthiessen's 
copper standard at 0° C. 

R 



Then §-' = function of f^-V 



This function is a complex one, and can be represented best by the 
accompanying curve; however, for 



^>3 X1 0.o. 



the approximate formula - = 10~ 5 i/ ;\ +0.28 
tc t 1 ~x~ at 

is sufficiently accurate for all practicable purposes. 

236 



SKIN EFFECT FACTORS. 



237 



Skin effect 


Factor* at 20° C. for Straig-ht Wire* Having* 




Circular Cross Section. 




Product of Cir- 
cular Mils by 
Cycles per Sec- 
ond. 
fX A. 


Factor * for 


Product of Cir- 
cular Mils by 
Cycles per Sec- 
ond. 
fXA. 


Factor for 


Iron Wire. 
C= 17 
n = 150. 


Copper W r ire 
C = 100 


Aluminum 

Wire 

C = 62 

/*= 1. 


500,000 


1.000 


5,000,000 


1.000 


1.000 


1,000,000 


1.015 


10,000,000 


1.000 


1.000 


2,000,000 


1.068 


20,000,000 


1.008 


1.000 


3,000,000 


1.144 


30,000,000 


1.025 


1.006 


4,000,000 


1.234 


40,000,000 


1.045 


1.015 


5,000,000 


1.332 


50,000,000 


1.070 


1.026 


6,000,000 


1.435 


60,000,000 


1.096 


1.040 


7,000,000 


1.535 


70,000,000 


1.126 


1.053 


8,000,000 


1.628 


80,000,000 


1.158 


1.069 


9,000,000 


1.714 


90,000,000 


1.195 


1.085 


10,000,000 


1.795 


100,000,000 


1.230 


1.104 


12,500,000 


1.974 


125,000,000 


1.332 


1.151 


15,000,000 


2.14 


150,000,000 


1.433 


1.206 


17,500,000 


2.29 


175,000,000 


1.530 


1.266 


20,000,000 


2.42 


200,000,000 


1.622 


1.330 


25,000,000 


2.68 


250,000,000 


1.790 


1.455 


30,000,000 


2.90 


300,000,000 


1.937 


1.575 


35,000,000 


3.11 


350,000,000 


2.07 


1.686 


40,000,000 


3.31 


400,000,000 


2.20 


1.787 


45,000,000 


3.49 


450,000,000 


2.31 


1.879 


50,000,000 


3.67 


500,000,000 


2.42 


1.965 


55,000,000 


3.83 


550,000,000 


2.53 


2.05 


60,000,000 


3.99 


600,000,000 


2.63 


2.13 



sj.u 






























/ 






























/ 




L. 1 * 






Curve for Determining 




/ 


/ 






S 


kin Effect Facte 


r 




/ 






l.b 










H.Pender 






/ 






























/ 










U 




















■ 


t 






























/ 












Lfl 


















/ 
















ps| 


i 














/ 














Lb 
















/ 






























/ 


f 
















L4 














/ 






























/ 
































/ 






























1 






























/ 


t 






























/ 






























7 




ffiC A 


xl"- 10 












i.O 


_-*= 


■/ 






1+Ht 



















.2 .4 .0 .3 LU UJ.4 1.6 1.3 2.0 2.2 2.4 2.6 2.9 \SL 

Fio. 1. 



* This corresponds to E.B.B. telegraph wire. 



238 CONDUCTORS. 



The approximate formula 

For Iron (E.B.B. telegraph wire), reduces to 

|-' = 479 X 1(T 6 V 'JA + 0.28 
for jA > 12.5 X 10 6 and t = 20° C. 
For Copper, reduces to 

^ = 96 X HT 6 \/fA +0.28 
ti 

for jA > 300 X 10 6 and t = 20° C. 
For Aluminum, reduces to 

jL' = 76 x io-sZ/Z+o.28 

for /A > 500 X 10 6 and t = 20° C. 

Examples: To find the effective resistance of a round-wire .5 inch in 
diameter, permeability 500, conductivity 10 per cent, at 15 cycles per 
second and 0° C: 

fuCA 15 X 500 X 10 X .25 X 10 6 , cc v 1ni0 
1 + at ~ 1 - 1.88 X 10 . 

/?' 
From the curve ■=— = 1.63 

ti 

or effective resistance R' = 1.63 R. 

To find the effective resistance of the same wire at 60 cycles per second: 

ffiCA 

1+at 

therefore, from formula R_ 

R 

or effective resistance R' = 3.01 R. 



= 7.5 X lO" 10 , 

- 2.73 + 0.28 = 3.01 



SELJF i;]¥I>UCTJM>]¥ A»D E¥DCCTIVE REACTANCE 

OJP TltJLWSJfllSSJLO^r CIRCUITS FORMED 

BY PARALLEL WIRES. 

The Coefficient of Self Induction (L) of an elementary circuit is defined as 
the ratio of the number of lines of induction produced by a current flowing 
in the circuit divided by the current in the circuit. When the conductor has 
a finite croc- section the exact definition of the coefficient of self induction 
is the ratio of twice the energy of the magnetic field produced by the cur- 
rent flowing to the square of the current. 

The practical unit of self induction is the henry; sometimes the milli- 
henry is used, which is equal to x^s of a henry. 

The coefficient of self induction of a circuit depends on the size and 
shape of the circuit, the cross section and shape of the conductor, the per- 
meabilities of the conductor and the surrounding medium, also, when the 
skin effect is large, upon the frequency of the current and the specific re- 
sistance of the conductor. The instantaneous E.M.F. induced in a cir- 
cuit by any change of the current flowing in the circuit is e = — -z- (Li), or, 
if L is constant, which is strictly true when there is no iron in the circuit, 

and approximately so in any case, e = — L -=r • 

at 
When a constant E.M.F. is impressed on a circuit or coil containing 
inductance, the current does not reach its full value instantly, as it is 



SELF INDUCTION AND INDUCTIVE REACTANCE. 239 



opposed at first by a counter-electromotive force due to the inductance. 
This counter-electromotive force gradual^ grows less until the current 
reaches its full strength, which theoretically takes an infinite time, and in 
practice it is usual to determine the time taken for the current to attain 
63.2% of its full value and this period is called the time-constant. 

Time-constant in seconds — -= : 

ohms resistance 

_ henrys X final amperes 
applied volts 
If the impressed E.M.F. varies according to the sine law and L is con- 
stant, the effective value of the counter inductive E.M.F. is 

E = 2 vfLI 
where f = cycles per second or frequency and J = the effective value of 
the current. 2 nfL is called the inductive reactance or simply the inductance 
of the circuit. 

The induced E.M.F. lags 90° behind the current. The E.M.F. required 
to overcome the induced E.M.F. leads the current by 90°. 

Form u Up for Self Induction and Inductive Reactance. 

Let r = radius of wire in inches. 

n = number of wire on B. and S. gauge.* 
D = distance between wires in inches. 

I = distance of transmission (length of one wire) in 1000 feet. 
L = coefficient of self induction of 1000 feet of wire in millihenrys. 

/ = frequency of current in cycles per second. 
X = 2 nfL X 10~ 3 = inductive reactance of 1000 feet of wire in ohms. 

Single-phase Circuit — 2 Wires. 



ID 




Fig. 2. 

Total self induction of circuit = 2 IL. 
Total inductive reactance of circuit = 2 IX. 

Three-phase Circuit — 3 Wires. 




Fig. 3. 

Total self induction per phase (circuit formed by any two wires) =\/3 IL. 
Total inductive reactance per phase = \/3 IX. 
For XOHr-JfEAOHTKTlC WIRES, 

L = 0.01524 + 0.14 log 10 (^\ 
- 0.00705 n + A. 
where A = 0.14 log 10 + 0.1258. 

* See table on next page for values of n for wires larger than No. 0. 



240 



CONDUCTORS. 



For IllOX WIRE, 

L-- 



. 0.01524 n + 0.14 log, 



•(f) 



where u = permeability of the iron. /u. varies with the quality of the iron 
and also with the strength of the current. The above formula is true 
only in case /a is constant over the cross section of the wire, which in any 
practical case is only approximately true. The tables on p. 248 are calcu- 
lated for /u. = 150, corresponding to good quality telegraph wire, and, 
therefore, 

L - 2.286 + 0.14 log 10 j - 

Values of A (=©.14 logr 10 I> + . 1858) for Various Interaxial 

Distances. 



D. 


A. 


I in. 


.0662 




.0837 


£ 


.1083 


1 


.1258 


2 


.1679 


3 


.1925 


6 


.2347 


12 


.2768 


18 


.3015 


24 


.3190 


36 


.3436 


48 


.3611 


60 


.3747 


72 


.3857 



Values of n for Wires Larger than ~No. O, B. and S. 



Size. 



00 B. and S. 

000 

0000 
250,000 C. M. 
800,000 
350,000 
400,000 
450,000 
500,000 
550,000 
600,000 
650,000 
700,000 
750,000 
800,000 
850,000 
900,000 
950,000 
1,000,000 



-1 

- 2 
-3 

- 3.719 

- 4.505 
-5.170 

- 5.746 
-6.254 

- 6.708 
-7.119 
-7.495 
-7.840 
-8.159 
-8.457 

- 8.735 

- 8.997 
-9.243 

- 9.476 

- 9.697 



n = 49.8812 - 9.92978 log CM. 



SELF INDUCTION. 



241 



Self Induction in ItEillihenrys per lOOO Feet of Solid 
Non-magnetic Wire. 

Note. — The self induction of a stranded wire is slightly less than that 
of a solid wire of the same cross section, and slightly greater than 
that of a solid wire having the same diameter, but more nearly equal to 
that of a solid wire with equal cross section. The exact value of the self 
induction of a strand is a complex expression involving both the size and 
number of the individual wires. (See L'Eclairage Electrique, Vol. Ill, p. 
20.) For all practical purposes the self induction of a strand may be 
taken equal to that of a solid conductor having the same cross section. 

L = .00705 n + A. 



B. and S. 
Gauge. 


Interaxial Distances. 


1" 


h" 


r 


1" 


2" 


3" 


0000 


!ioi3 

.1084 
.1225 
.1367 
.1507 
.1647 






.0871 
.0943 
.1012 
.1083 
.1154 
.1223 
.1364 
.1436 
.1506 
.1647 
.1788 
.1928 
.2068 


.1046 
.1116 
.1187 
.1258 
.1329 
.1398 
.1539 
.1610 
.1681 
.1822 
.1963 
.2103 
.2243 


.1467 
.1538 
.1608 
.1679 
.1750 
.1820 
.1961 
.2032 
.2102 
.2243 
.2384 
.2525 
.2665 


.1714 


000 






.1778 


00 




.1855 







.1926 


1 

2 

4 

5 

6 

8 

10 

12 

14 


0977 
1117 
1189 
1259 
1401 
1541 
1682 
1822 


.1946 
.2066 
.2207 
.2278 
.2349 
.2490 
.2631 
.2772 
.2911 









Interaxial Distances. 






Cir. Mils and 


















B. and S. 


















Gauge. 


6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.1659 


.2080 


.2327 


.2502 


.2748 


.2923 


.3059 


.3169 


900,000 


.1691 


.2112 


.2359 


.2534 


.2780 


.2955 


.3091 


.3201 


800000 


.1727 


.2148 


.2395 


.2570 


.2816 


.2991 


.3127 


.3237 


700 000 


.1768 


.2189 


.2436 


.2611 


.2857 


.3032 


.3168 


.3278 


600,000 


.1815 


.2236 


.2483 


.2658 


.2904 


.3079 


.3215 


.3325 


500 000 


.1871 


.2292 


.2539 


.2714 


.2960 


.3135 


.3271 


.3381 


450,000 


.1903 


.2324 


.2571 


.2746 


.2992 


.3167 


.3303 


.3413 


400,000 


.1939 


.2360 


.2607 


.2782 


.3028 


.3203 


.3339 


.3449 


350,000 


.1980 


.2401 


.2648 


.2823 


.3069 


.3244 


.3380 


.3490 


300,000 


.2027 


.2448 


.2695 


.2870 


.3116 


.3291 


.3427 


.3537 


250,000 


.2083 


.2504 


.2751 


.2926 


.3172 


.3347 


.3483 


.3593 


0000 


.2135 


.2556 


.2803 


.2978 


.3224 


.3399 


.3535 


.3645 


000 


.2206 


.2627 


.2874 


.3049 


.3295 


.3470 


.3606 


.3716 


00 


.2276 


.2648 


.2945 


.3120 


.3366 


.3541 


.3677 


.3787 





.2347 


.2768 


.3015 


.3190 


.3436 


.3611 


.3747 


.3857 


1 


.2418 


.2839 


.3086 


.3261 


.3507 


.3682 


.3818 


.3928 


2 


.2488 


.2909 


.3156 


.3331 


.3577 


.3752 


.3888 


.3998 


4 


.2629 


.3050 


.3297 


.3472 


.3718 


.3893 


.4029 


.4139 


6 


.2770 


.3191 


.3438 


.3613 


.3859 


.4034 


.4170 


.4280 


8 


.2911 


.3332 


.3579 


.3754 


.4000 


.4175 


.4311 


.4421 


10 


.3052 


.3473 


.3720 


.3895 


.4141 


.4316 


.4452 


.4562 



242 



CONDUCTORS. 



Inductive Reactance in Ohms Per lOOO feet of Solid Aon* 
Jflagrnetic TFire. 

100 Cycles per Second. X = 0.6283 L. 

Note. — Inductive reactance at other frequencies proportional to values 
given in this table. 







Interaxial Distances. 




























Gauge. 


¥ 


¥ 


3// 

4 


1" 


2" 


3" 


0000 






.0547 


.0657 


.0922 


.1076 


000 






.0592 


.0701 


.0966 


.1116 


00 . 






.0635 


.0745 


.1010 


.1165 









.0680 


.0790 


.1055 


.1209 


1 






.0725 


.0834 


.1099 


.1254 


2 




.0613 


.0768 


.0878 


.1143 


.1298 


4 




.0702 


.0857 


.0966 


.1231 


.1386 


5 


0636 


.0747 


.0902 


.1011 


.1276 


.1431 


6 


0681 


.0791 


.0946 


.1056 


.1320 


.1475 


8 


0770 


.0879 


.1034 


.1144 


.1409 


.1564 


10 


0858 


.0968 


.1123 


.1233 


.1497 


.1652 


12 


0946 


.1056 


.1211 


.1321 


.1586 


.1741 


14 


1034 


.1144 


.1299 


.1409 


.1674 


.1828 



Cir. Mils and 






Interaxial Distances. 






B. and S. 


















Gauge. 


6" 


12" 


18* 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.1042 


.1307 


.1462 


.1572 


.1727 


.1837 


.1922 


.1991 


900,000 


.1062 


.1327 


.1481 


.1592 


.1747 


.1857 


.1942 


.2011 


800 000 


.1085 


.1350 


.1505 


.1615 


.1769 


.1879 


.1965 


.2034 


700,000 


.1111 


.1375 


.1531 


.1640 


.1795 


.1905 


.1990 


.2060 


600,000 


.1140 


.1405 


.1560 


.1670 


.1825 


.1954 


.2020 


.2089 


500,000 


.1176 


.1440 


.1595 


.1705 


.1860 


.1970 


.2055 


.2124 


450,000 


.1196 


.1460 


.1615 


.1725 


.1880 


.1990 


.2075 


.2144 


400,000 


.1218 


.1483 


.1638 


.1748 


.1902 


.2012 


.2098 


.2167 


350,000 


.1244 


.1509 


.1664 


.1774 


.1928 


.2038 


.2124 


.2193 


300,000 


.1274 


.1538 


.1693 


.1803 


.1958 


.2068 


.2153 


.2222 


250,000 


.1309 


.1573 


.1728 


.1838 


.1993 


.2103 


.2188 


.2257 


0000 


.1341 


.1606 


.1761 


.1871 


.2026 


.2136 


.2221 


.2290 


000 


.1386 


.1651 


.1806 


.1916 


.2070 


.2180 


.2266 


.2335 


00 


.1430 


.1695 


.1850 


.1960 


.2115 


.2225 


.2310 


.2379 





.1475 


.1739 


.1894 


.2004 


.2159 


.2269 


.2354 


.2423 


1 


.1519 


.1784 


.1939 


.2049 


.2203 


.2313 


.2399 


.2468 


2 


.1563 


.1828 


.1983 


.2093 


.2247 


.2357 


.2443 


.2512 


4 


.1652 


.1916 


.2072 


.2181 


.2336 


.2446 


.2531 


.2601 


6 


.1740 


.2005 


.2160 


.2270 


.2425 


.2535 


.2620 


.2689 


8 


.1829 


.2093 


.2249 


.2359 


.2513 


.2623 


.2709 


.2778 


10 


.1918 


.2182 


.2337 


.2447 


.2602 


.2712 


.2797 


.2866 



INDUCTIVE KEACTANCE. 



243 



Inductive Reactance in Ohmi Per lOOO feet of Solid \ on- 
HEag-netic IFire. 

25 Cycles Per Second. X = .1571 L. 







Interaxial Distances. 








B. and S. 
Gauge. 














3 » 


f 


V 


1" 


r 


3" 


0000 






.0137 




0169 


.0230 




.0269 


000 








.0148 




0175 


.0242 




.0279 


00 








.0159 




0186 


.0253 




.0291 











.0170 




0198 


.0264 




.0302 


1 








.0181 




0209 


.0275 




.0313 


2 






!6i53 


.0192 




0220 


.0286 




.0325 


4 






.0176 


.0214 




0242 


.0308 




.0347 


5 




0159 


.0187 


.0225 




0253 


.0319 




.0358 


6 




0170 


.0198 


.0236 




0264 


.0330 




.0369 


8 




0192 


.0220 


.0259 




0286 


.0352 




.0391 


10 




0215 


.0242 


.0281 




0308 


.0374 




.0413 


12 




0237 


.0264 


.0303 




0330 


.0396 




.0435 


14 


l0259 


.0286 


.0325 




0352 


.0418 




.0457 


Cir. Mils and 




Interaxial Distances 








B. and S. 
Gauge. 














6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.0261 


.0327 


.0366 


.0393 


.0432 


.0460 


.0481 


.0498 


900,000 


.0266 


.0332 


.0371 


.0398 


.0437 


.0465 


.0486 


.0503 


800,000 


.0272 


.0338 


.0377 


.0404 


.0443 


.0471 


.0492 


.0509 


700,000 


.0278 


.0344 


.0383 


.0410 


.0449 


.0477 


.0498 


.0515 


600,000 


.0285 


.0351 


.0390 


.0417 


.0456 


.0484 


.0505 


.0522 


500,000 


.0294 


.0360 


.0399 


.0426 


.0465 


.0493 


.0514 


.0531 


450,000 


.0299 


.0365 


.0404 


.0431 


.0470 


.0498 


.0519 


.0536 


400,000 


.0305 


.0371 


.0410 


.0437 


.0476 


.0503 


.0525 


.0542 


360,000 


.0311 


.0377 


.0416 


.0444 


.0482 


.0510 


.0531 


.0548 


300,000 


.0319 


.0385 


.0423 


.0451 


.0490 


.0517 


.0538 


.0556 


250,000 


.0327 


.0393 


.0432 


.0460 


.0498 


.0526 


.0547 


.0564 


0000 


.0335 


.0402 


.0440 


.0468 


.0505 


.0534 


.0555 


.0573 


000 


.0347 


.0413 


.0452 


.0479 


.0518 


.0545 


.0567 


.0584 


00 


.0358 


.0424 


.0463 


.0490 


.0529 


.0556 


.0578 


.0595 





.0369 


.0435 


.0474 


.0501 


.0540 


.0567 


.0589 


.0606 


1 


.0380 


.0446 


.0485 


.0512 


.0551 


.0578 


.0600 


.0617 


2 


.0391 


.0457 


.0496 


.0523 


.0562 


.0589 


.0611 


.0628 


4 


.0413 


.0479 


.0518 


.0545 


.0584 


.0612 


.0633 


.0650 


6 


.0435 


.0501 


.0540 


.0568 


.0606 


.0634 


.0655 


.0672 


8 


.0457 


.0523 


.0562 


.0590 


.0628 


.0656 


.0677 


.0695 


10 


.0480 


.0546 


.0584 


.0612 


.0651 


.0678 


.0699 


.0717 



244 



CONDUCTORS. 



Inductive* Reactance in Ohm* per lOOO Feet of Solid 
Non-HEagrnetic Wire. 



60 Cycles Per Second. 



0.3770 L. 









Interaxial Distances. 






B. and S. 












Gauge. 


















r ¥ 


r 


1" 


2" 


3" 


0000 






.0328 


.0394 


.0553 


.0646 


000 






.0355 


.0421 


.0580 


.0670 


00 






.0381 


.0447 


.0606 


.0699 









.0408 


.0474 


.0633 


.0726 


1 






.0435 


.0501 


.0659 


.0752 


2 




0368 


.0461 


.0527 


.0686 


.0779 


4 




0421 


.0514 


.0580 


.0739 


.0832 


5 




0382 .0448 


.0541 


.0607 


.0766 


.0859 


6 




0409 .0474 


.0567 


,0633 


.0792 


.0885 


8 




0462 .0528 


.0621 


.0687 


.0845 


.0938 


10 




0515 .0581 


.0674 


.0740 


.0898 


.0991 


12 




0568 .0634 


.0727 


.0793 


.0951 


.1044 


14 




0621 .0687 


.0779 


.0845 


.1004 


.1097 



+ 






Interaxial Distances. 






Cir. Mils and 


















B. and S. 


































Gauge. 


6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.0026 


.0784 


.0877 


.0943 


.1036 


.1102 


.1153 


.1194 


900,000 


.0638 


.0796 


.0880 


.0955 


.1048 


.1114 


.1166 


.120G 


800,000 


.0652 


.0810 


.0903 


.0fo9 


.1062 


.1128 


.1170 


.1220 


700,000 


.0667 


.0825 


.0918 


.0^84 


.1077 


.1143 


.1194 


.1235 


600,000 


.0685 


.0843 


.0936 


.1002 


. 1005 


.1101 


.1212 


.1253 


500,000 


.0706 


.0864 


.0957 


.1023 


.1116 


.1183 


.1233 


.1274 


450,000 


.0718 


.0876 


.0969 


.1035 


.1128 


.1194 


.1245 


.1286 


400,000 


.0731 


.0890 


.0983 


.1049 


.1141 


.1207 


.1259 


.1300 


350,000 


.0746 


.0905 


.0998 


.1064 


.1157 


.1225 


.1274 


.1316 


300,000 


.0764 


.0923 


.1016 


.1082 


.1175 


.1241 


.1292 


.1333 


250,000 


.0785 


.0944 


.1037 


.1103 


.1196 


.1262 


.1313 


.1354 


0000 


.0805 


.0964 


.1057 


.1123 


.1216 


.1282 


.1333 


.1374 


000 


.0832 


.0991 


.1084 


.1150 


.1242 


.1308 


.1360 


.1401 


00 


.0858 


.1017 


.1110 


.1176 


.1269 


.1335 


.1386 


.1427 





.0885 


.1043 


. 3 36 


.1202 


.1295 


.1361 


.1412 


.1454 


1 


.0911 


.1070 


.1163 


.1229 


.1322 


.1388 


.1439 


.1481 


2 


.0938 


.1097 


.1190 


.1256 


.1348 


.1414 


.1466 


. 1507 


4 


.0991 


.1150 


.1243 


.1309 


.1402 


.1468 


.1510 


.1561 


6 


.1044 


.1203 


.1296 


.1362 


.1455 


.1521 


.1572 


.1613 


8 


.1097 


.12o6 


.1349 


.1415 


.1508 


.1574 


.1625 


.1667 


10 


.1151 


.1309 


.1402 


.1468 


.1561 


.1627 


.1678 


.1720 



INDUCTIVE REACTANCE. 



245 



Inductive Reactance of Loop Formed by Two Wires of a 
Three-Phase Transmission JLine. 

Ohms per 1000 Feet of Line* (Conductor Non-Magnetic) 
100 Cycles per Second. 



*i 



oop 



vSx f( 



or single wire. 



Note. — Inductive reactance at other frequencies proportional to values 
given in this table. 







Interaxial Distances 






B. and S. 
Gauge 










F 


¥ 


3// 

4 


1" 


2" 


3" 


0000 








.0947 


.1138 


.1596 


.1864 


000 












.1025 


.1214 


.1673 


.1933 


00 












.1100 


.1291 


.1749 


.2018 















.1178 


.1368 


.1827 


.2094 


1 












.1255 


.1445 


.1903 


.2171 


2 










1062 


.1331 


.1521 


.1980 


.2248 


4 










1215 


.1484 


.1674 


.2133 


.2401 


5 




L102 




1293 


.1563 


.1758 


.2210 


.2478 


6 




L179 




1369 


.1638 


.1828 


.2286 


.2554 


8 




L333 




1523 


.1791 


.1982 


.2440 


.2708 


10 


. 


1487 




1677 


.1945 


.2135 


.2593 


.2862 


12 




.639 




1830 


.2097 


.2288 


.2746 


.3014 


14 


• 


1791 




1982 


.2250 


.2440 


.2898 


.3167 









Interaxial Distances. 






Cir. Mils and 


















B. and S. 


















Gauge. 


6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.1807 


.2265 


.2533 


.2724 


.2992 


.3183 


.3330 


.3450 


900,000 


.1842 


.2300 


.2568 


.2759 


.3027 


.3218 


.3305 


.3485 


800,000 


.1881 


.2339 


.2607 


.2798 


.3066 


.3257 


.3404 


.3524 


700,000 


.1926 


.2384 


.2652 


.2843 


.3111 


.3302 


.3449 


.3569 


600,000 


.1977 


.2435 


.2703 


.2894 


.3102 


.3353 


.3500 


.3620 


500,000 


.2038 


.2496 


.2764 


.2955 


.3223 


.3414 


.3561 


.3681 


450,000 


.2073 


.2530 


.2799 


.2989 


.3258 


.3449 


.3596 


.3716 


400,000 


.2111 


.2570 


.2839 


.3029 


.3296 


.3487 


.3636 


.3755 


350,000 


.2156 


.2615 


.2884 


.3074 


.3341 


.3532 


.3681 


.3800 


300,000 


.2208 


.2665 


.2934 


.3125 


.3393 


.3584 


.3731 


.3851 


250 000 


.2268 


.2726 


.2995 


.3185 


.3454 


.3644 


.3792 


.3911 


0000 


.2324 


.2783 


.3052 


.3242 


.3511 


.3702 


.3840 


.3969 


000 


.2402 


.2861 


.3130 


.3320 


.3587 


.3778 


.3927 


.4047 


00 


.2478 


.2937 


.3206 


.3397 


.3665 


, .3856 


.4003 


.4123 





.2556 


.3014 


.3282 


.3473 


.3742 


.3932 


.4079 


.4199 


1 


.2632 


.3092 


.3360 


.3551 


.3818 


.4008 


.4157 


.4277 


2 


.2709 


.3168 


.3437 


.3627 


.3894 


.4085 


.4234 


.4353 


4 


.2863 


.3320 


.3591 


.3780 


.4048 


.4239 


.4386 


.4508 


6 


.3015 


.3475 


.3743 


.3934 


.4203 


.4393 


.4540 


.4660 


8 


.3170 


.3627 


.3898 


.4088 


.4355 


.4546 


.4695 


.4814 


10 


.3324 


.3781 


.4050 


.4241 


.4509 


.4700 


.4847 


.4967 



* Length of line equals one half the total length of wire in the loop. 



246 



CONDUCTORS. 



Inductive Reactance of Loop Formed oj Two Wires of a 
Three-Phase Transmission Line. 

Ohms Per 1000 Feet of Line.* (Conductor Non-Magnetic.) 

25 Cycles per Second. 

Xloop = \/3 X for single wire. 







Interaxial Distances. 






B. and S. 










Gauge. 
















1" 


2 


3.// 
4 


1" 


2" 


3" 


0000 








.0237 


.0285 


.0399 


.0466 


000 










.0256 


.0304 


.0418 


.0483 


00 










.0275 


.0323 


.0437 


.0504 













.0294 


.0342 


.0457 


.0524 


1 










.0314 


.0361 


.0476 


.0543 


2 








0266 


.0333 


.0380 


.0495 


.0562 


4 








0304 


.0371 


.0418 


.0533 


.0600 


5 


.0 


276 




0323 


.0391 


.0438 


.0552 


.0620 


6 


.0 


295 




0342 


.0409 


.0457 


.0572 


.0639 


8 


.0 


333 




0381 


.0448 


.0495 


.0610 


.0677 


10 


.0 


372 




0419 


.0486 


.0534 


.0648 


.0715 


12 


.0 


410 




0457 


.0524 


.0572 


.0687 


.0754 


14 


.0 


448 




0495 


.0562 


.0610 


.0725 


.0792 









Interaxial 


Distances. 






Cir. Mils and 


















B. and S. 


































Gauge. 


6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.0452 


.0566 


.0633 


.0681 


.0748 


.0796 


.0832 


.0862 


900,000 


.0461 


.0575 


.0642 


.0690 


.0757 


.0805 


.0841 


.0871 


800,000 


.0471 


.0585 


.0652 


.0700 


.0767 


.0815 


.0851 


.0881 


700,000 


.0482 


.0596 


.0663 


.0711 


.0778 


.0826 


.0862 


.0892 


600,000 


.0495 


.0609 


.0676 


.0724 


.0791 


.0839 


.0875 


.0905 


500,000 


.0510 


.0624 


.0691 


.0739 


.0806 


.0854 


.0890 


.0920 


450,000 


.0518 


.0633 


.0700 


.0747 


.0815 


.0862 


.0899 


.0929 


400,000 


.0528 


.0643 


.0710 


.0757 


.0824 


.0872 


.0909 


.0939 


350,000 


.0539 


.0654 


.0721 


.0769 


.0835 


.0883 


.0920 


.0950 


300,000 


.0552 


.0666 


.0734 


.0781 


.0848 


.0896 


.0933 


.0963 


250,000 


.0567 


.0682 


.0749 


.0796 


.0864 


.0911 


.0948 


.0978 


0000 


.0581 


.0696 


.0763 


.0811 


.0878 


.0926 


.0962 


.0992 


000 


.0601 


.0715 


.0783 


.0830 


.0897 


.0945 


.0982 


.1012 


00 


.0620, 


.0734 


.0802 


.0849 


.0916 


.0964 


.1001 


.1031 





.0639 


.0754 


.0821 


.0868 


.0936 


.0983 


.1020 


.1050 


1 


.0658 


.0773 


.0840 


.0888 


.0955 


.1002 


.1039 


.1069 


2 


.0677 


.0792 


.0859 


.0907 


.0974 


.1021 


.1059 


.1088 


4 


.0716 


.0830 


.0898 


.0945 


.1012 


.1060 


.1097 


.1127 


6 


.0754 


.0869 


.0936 


.0984 


.1051 


.1098 


.1135 


.1165 


8 


.0793 


.0907 


.0975 


.1022 


.1089 


.1137 


.1174 


.1204 


10 


.0831 


.0945 


.1013 


.1060 


.1127 


.1175 


.1212 


.1242 



* Length of line equals half the total length of wire in the loop. 



INDUCTIVE REACTANCE. 



247 



Inductive Reactance of JLoop Formed or Two Wires of a 
Xhree-Phase Transmission ILine. 

Ohms Per 1000 Feet of Line.* (Conductor Non-Magnetic.) 

60 Cycles per Second. 

Xloop = V3 X for single wire. 













Interaxial Distances. 






B. and S. 










Gauge. 
















t" 


¥ 


3.// 

4 


1" 


2" 


3" 


0000 








.0568 
.0615 
.0660 
.0707 
.0753 


.0683 
.0728 
.0774 
.0821 
.0867 


.0958 
.1004 
.1049 
.1096 
.1142 


.1118 


000 










.1160 


00 




.1211 







.1257 


1 




.1303 


2 








0637 


.0798 


.0912 


.1188 


.1349 


4 








0729 


.0890 


.1004 


.1280 


.1440 


5 


.0 


R61 




0776 


.0938 


.1051 


.1326 


.1487 


6 


.0 


708 




0821 


.0983 


.1097 


.1372 


.1533 


8 


.0 


300 




0914 


.1075 


.1189 


.1464 


.1625 


10 


.0 


392 




1006 


.1167 


.1281 


.1556 


.1717 


12 


.0 


983 




1098 


.1258 


.1373 


.1648 


.1809 


14 


.1 


375 




1189 


.1350 


.1464 


.1739 


.1900 



Cir. Mils and 






Interaxial Distances. 






B. and S. 
Gauge. 


















6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.1084 


.1359 


.1519 


.1634 


.1795 


.1909 


.1998 


.2070 


900,000 


.1105 


.1380 


.1540 


.1655 


.1816 


.1930 


.2019 


.2091 


800,000 


.1129 


.1404 


.1564 


.1679 


.1840 


.1954 


.2043 


.2115 


700,000 


.1156 


.1431 


.1591 


.1706 


.1867 


.1981 


.2070 


.2142 


600,000 


.1187 


.1462 


.1622 


.1737 


.1898 


.2012 


.2101 


.2173 


500,000 


.1223 


.1498 


.1658 


.1773 


.1934 


.2048 


.2137 


.2209 


450,000 


.1244 


.1518 


.1679 


.1793 


.1955 


.2069 


.2158 


.2230 


400,000 


.1267 


.1542 


.1703 


.1817 


.1978 


.2092 


.2182 


.2253 


350 000 


.1294 


.1569 


.1730 


.1844 


.2005 


.2119 


.2209 


.2280 


300,000 


.1325 


.1599 


.1760 


.1875 


.2036 


.2150 


.2239 


.2311 


250,000 


.1361 


.1636 


.1797 


.1911 


.2072 


.2186 


.2275 


.2347 


0000 


.1394 


.1670 


.1831 


.1945 


.2107 


.2221 


. 2309 


.2381 


000 


.1441 


.1717 


.1878 


.1992 


.2152 


.2267 


.2356 


.2428 


00 


.1487 


.1762 


.1924 


.2038 


.2199 


.2314 


.2402 


.2474 





.1534 


.1808 


.1969 


.2084 


.2245 


.2359 


.2447 


.2519 


1 


.1579 


.1855 


.2016 


.2131 


.2291 


.2405 


.2494 


.2566 


2 


.1625 


.1901 


.2062 


.2176 


.2336 


.2451 


.2540 


.2612 


4 


.1718 


.1992 


.2155 


.2268 


.2429 


.2543 


.2632 


.2705 


6 


.1809 


.2085 


.2246 


.2360 


.2522 


.2636 


.2724 


.2796 


8 


.1902 


.2176 


.2339 


.2453 


.2613 


.2728 


.2817 


.2888 


10 


.1994 


.2269 


.2430 


.2545 


.2705 


.2820 


.2908 


.2980 



* Length of line equals one half the total length of wire in the loop. 



248 



CONDUCTORS. 



Self Induction in Jlillihenrys per lOOO Feet of Solid 
Iron Wire. Permeability 15© C. O. S. Units. 



L - 2.286+ .14 1og 10 (j'y 







Interaxial Distances. 


Roebling 


Dia. 

In. 




Gauge. 






















1" 


2" 


3" 


6" 


9" 


12" 


18" 


24" 


4 


.225 


2.4189 


2.4610 


2.4857 


2.5278 


2.5525 


2.5699 


2.5946 


2.6121 


6 


.192 2.4285 


2.4706 


2.4953 


2.5374 


2.5621 


2.5796 


2.6042 


2.6217 


8 


.162 2.4389 


2.4809 


2.5056 


2.5478 


2.5724 


2.5899 


2.6146 


2.6321 


9 


.178 2.4443 


2.4865 


2.5111 


2.5533 


2.5779 


2.5954 


2.6201 


2.6376 


10 


.135 


2.4499 


2.4921 


2.5167 


2.5589 


2.5835 


2.6010 


2.6257 


2.6432 


11 


.120 


2.4571 


2.4992 2.5239 


2.5660 


2.5907 


2.6082 


2.6328 


2.6503 


12 


.105 


2.4652 


2.507412.5319 


2.5742 


2.5988 


2.6163 


2.6409 


2.6584 


14 


.080 


2.4817 


2.5239 2.5485 


2.5907 


2.6153 


2.6328 


2.6575 


2.6749 



Inductive Reactance in Ohms per lOOO feet of Solid 
Iron l^ire. 

100 Cycles Per Second. X = 0.6283 L. 

Note. — Inductive reactance at other frequencies proportional to 
values given in this table. 











Interaxial Distances. 






Roebling 


Dia. 
In. 




Gauge. 






















1" 


2" 


3" 


6" 


9" 


12" 


18" 


24" 
/ 


4 


.225 


1.5191 


1.5455 


1.5610 


1.5875 


1.6029 


1.6139 


1.6294 


1.6404 


6 


192 


1.5251 


1.5516 


1.5671 


1.5935 


1.6090 


1.6199 


1.6355 


1.6465 


8 


162 


1.5316 


1.5581 


1.5735 


1.6000 


1.6155 


1.6265 


1.6419 


1.6529 


9 


148 


1.5350 


1.5615 


1.5769 


1.6035 


1.6189 


1.6299 


1.6454 


1.6564 


10 


135 


1.5386 


1.5650 


1.5805 


1.6069 


1.6225 


1.6335 


1 . 6489 


1.6599 


11 


i?n 


1.5431 


1.5695 


1.5850 


1.6115 


1 . 6269 


1.6379 


1.6534 


1 . 6644 


12 


105 


1.5482 


1.5746 


1.5901 


1.6166 


1.6320 


1.6430 


1.6585 


1.6695 


14 


.080 


1.5585 


1.5850 


1.6005 


1.6269 


1.6424 


1.6534 


1.6689 


1.6799 



CAPACITY. CAPACITY REACTANCE, Al¥» CHAItO- 

K¥« CURRENT OF TMAXSIfllSSlOHr CIRCUITS 

FOIl.lI E1» BY PARALLEL WIRES. 

Whenever a difference of potential is established between two or more 
conductors a static charge manifests itself on each conductor. If there 
are but two conductors present these static charges are equal and opposite. 
Two conductors thus carrying equal and opposite charges are said to form 
a condenser. The ratio of the charge (q) on one of the conductors to the 
difference of potential (e) between the two conductors is called the capa- 
city (C) of the condenser, i.e., 

<? = £. 



Tf q is expressed in coulombs and e in volts, the unit of capacity as de- 
fined by this equation is called the farad. A capacity as large as a farad 



TRANSMISSION CIRCUITS. 249 



is a mathematical fiction ; the unit employed in practice is the microfarad, 
which is one millionth of a farad. 

The capacity of a condenser depends on the size and shape of the con- 
ductors, the specific inductive capacity of the surrounding medium, and 
its distance from other conductors. 

The instantaneous capacity E.M.F. is in practical units, 



'/' 



f i 



and the effective value of this E.M.F. for a sine wave current is 

m «, 1Q6 . 

10 6 

The expression „ ,~ is called the capacity reactance, or simply the capaci- 
z 717 c 

2 irfC 1 
tance, of the circuit. The reciprocal of this quantity, namely, - 6 , is 

called the capacity susceptance ; this is the quantity used in the treat- 
ment of the capacity of transmission circuits. 

The current required to charge and discharge a condenser is called 
the charging current; for a sine wave of impressed E.M.F. the charging 
current is 

i c = 2 TtfCE x icr 6 . 

The capacity E.M.F. leads the current by 90°; the E.M.F. required to 
overcome the capacity E.M.F. lags 90° behind the current. 

Single -Phase Transmission JLine. — The capacity effect in a single- 
phase transmission line is the same as would be produced by shunting 
across the line at each point an infinitesimal condenser having a capacity 
equal to that of an infinitesimal length of circuit. The 
exact calculation of this effect involves the use of hyperbolic 
functions and complex algebraic quantities. A close approx- 
imation is to consider a condenser of half the capacity of the O" 
line shunted across the line at each end. A still* closer ap- 
proximation is to divide the line into three equal parts and 
consider the capacity of each section concentrated in a con- Fig. 4. 
denser at the center of that section, but in most practical 
cases this refinement is not necessary. For the purpose of calculating the 
charging current a very simple and in general sufficiently accurate method 
is to determine the current taken by a condenser having a capacity equal 
to that of the entire line when charged to the pressure on the line at the 
generating end. For the calculation of the effect of capacity on the effi- 
ciency and regulation of transmission lines see page 264. 

J-nree-Pnase Transmission Line. — The capacity effect in a three- 
phase transmission line is the same as would 
be produced by shunting the line at each point by 
three infinitesimal condensers connected in star 
with the neutral point grounded, the capacity 
of each condenser being equal to twice that of 
a condenser of infinitesimal length formed by any 
two of the wires. The effect of capacity on the 
regulation and efficiency of the line can be deter- 
mined with sufficient accuracy in most cases by 
considering the line shunted at each end by three 
-c, - condensers connected in star, the capacity of each 

* TQ - 5 - condenser being equal to that formed by any two 

wires of the line. (See page 264.) 
An approximate value for the charging current per wire is the current 
required to charge a condenser, equal in capacity to that of any two of the 
wires, to the pressure at the generating end of the line between any one 
wire and the neutral point. 



y% 



250 CONDUCTORS. 

Formulae: 

Let r = radius of wire in inches. 

n = number of wire on B. and S. gauge.* 
H = height of wires above ground. 
D = distance between wires in inches. 

I = distance of transmission (length of one wire) in 1000 feet. 
V = impressed voltage between adjacent wires at generating end. 
V"o= impressed volts between any wire and ground or neutral 

at generating end. 
Cq= capacity per 1000 feet of a single wire parallel to the earth 

in microfarads. 
C = capacity per 1000 feet of circuit (2000 feet of wire) formed 

by two parallel wires. 
/ = frequency of impressed E.M.F. in cycles per second. 

b = — — ^ = capacity susceptance per 1000 feet of a single wire 

parallel to the earth. 

b = 6 = capacity susceptance per 1000 feet of circuit (2000 

feet of wire) formed by two parallel wires. 
K = dielectric constant of surrounding medium. For bare or 
insulated overhead wires, without metallic sheath, K = 1. 

Single Overhead Wire with Earth Return. 



2H-- 



Co - ; 2H ' 

logio — — 



Total capacity of circuit = I C. 
Total capacity susceptance of circuit = I b. 
M^Jl^fciim^ Total c har S m g current = I bV . 
Fig. 6. 

Two Overhead Wires, Single-Phase. 

.003677 K-2-r-^ 

logio — 

1 t 
B-\- 13.7n 

Total capacity of circuit = IC. Fig. 7. 

Total capacity susceptance of circuit = 1 b. 
Total charging current = lb V. 

Two Wires in Grounded Metallic Sheath, Single-Phase. 

.003677 K 






Y2a R 2 - a 2 l 

logi ° |t ^t^J 

Total capacity of circuit = I C, 

Total capacity susceptance of circuit = lb. 

Total charging current = I b V. 



* For values of n for wires larger than No. see page 240. 

J B = 272 logjo l> + 215. For values of B see p. 251. For stranded wires 
neither formula is strictly accurate; the logarithmic formula gives results 
practically correct; values calculated by the second formula are about 3 per 
cent too small. 



TRANSMISSION CIRCUITS. 



251 



Concentric Cable in Grounded Metallic Sheath, 
Single -Phase. 

Let C ' = capacity in microfarads per 1000 feet of condenser formed by 
the two conductors. 

C" = capacity in microfarads per 
1000 feet of condenser formed by 
outer conductor and sheath. 



Then C ' = 



C" = 



♦007354 K x 

log l0 — 
.007354 K 2 

logio -7 

^3 




Fig. 9. 



Total charging current = I b' V + I b" Vo. 

Three Overhead Wires, Three-Phaie. 

.003677 




SO' 



o 



c = 



logio - 



B + 13.7 n 



Total capacity per wire = 2 I C. 

Total capacitance per wire = 2 I b. 

m , !_ • • 2Z6V 

Total charging current per wire = — — = 

\/3 



2lbV . 



Fig. 10. 
Three Wires in Metallic Sheath, Three-Phase. 



C - 



.007354 K 



T3 a 2 (ft 2 - a 2 )H 
logw L"F" ft 6 - a* J 



Total capacity per wire = 2 Z C. 
Total capacitance per wire = 2 I b. 

Total charging current per wire = — - = 2 

V3 



bVo- 




Fig. 11. 
Sheath Grounded. 
Values of B= £»£ log- l0 I* + «15. 



D. 


B. 


1 


99 


i 


133 


i 


181 


l 


215 


2 


297 


3 


344 


6 


426 


12 


508 


18 


556 


24 


590 


36 


638 


48 


672 


60 


698 


72 


720 



* B = 272 log^o D + 215. For values see table. For stranded wires 
neither formula is strictly accurate; the logarithmic formula gives results 
practically correct; values calculated by the second formula are about 3 per 
cent too small. 



252 



CONDUCTORS. 



Capacity in .flicro farad* per lOOO feet of Circuit (2000 

Feet of Wire) .Formed l>y Two Parallel 

Aerial Wires. 



C = 



0.003677 
D ' 



B+ 13.7 n 



6 . 

.13 








Interaxial Distances. 








pq 


Dia. 

over 
Insul. 


r 


¥ 


r 


1" 


2" 


3* 


6* 


12" 


18" 


D000 


.00748 
.00723 
.00696 
.00669 
.00643 
.00678 
.Q0626 
.00601 
.00576 
.00591 
.00541 
.00499 
.00459 






.00716 


.00575 
.00534 
.00497 
.00465 
.00437 
.00413 
.00371 
.00353 
.00336 
.00308 
.00284 
.00264 
.00246 


.00391 
.00371 
.00353 
.00337 
.00522 
.0030S 
.00284 
.00274 
.00264 
.00246 
.00230 
.00217 
.00205 


.00329 
.00315 
.00302 
.00290 
.00279 
.00269 
.00250 
.00242 
.00234 
.00220 
.00207 
.00196 
.00180 


.00259 
.00250 
.00242 
.00234 
.00227 
.00220 
.0020G 
.00202 
.0019G 
.00186 
.00177 
.00109 
.00162 


.00214 
.00208 
.00202 
.00197 
.00191 
.00183 
.00177 
.00173 
.001G9 
.00162 
.00155 
.00148 
.00143 


.00194 


000 






.00652 


.0018& 


00 






.00598 


.00184 


o 






.00553 


.00180 


1 






.00514 


00175 


2 




.00624 


.00480 
.00424 
.00401 
.00380 
.00344 
.00314 
.00288 
.00268 


o00171 


4 

5 

6 

8 

10 

12 

14 


".00597 
.00552 
.00479 
.00423 
.00380 
.00344 


.00533 
.004b6 
.00465 
.00412 
.00370 
.00336 
.00308 


.00163 
.0016C 
.00156 
.0015C 
.00144 
.00139 
.00134 









Interaxial Distances. 








Size Cir. Mils 




















6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.00361 


.00279 


.00246 


.00227 


.00204 


.00191 


.00182 


.00173 


900,000 


.00353 


.00274 


.00242 


.00223 


.00202 


.00189 


.00180 


.00173 


800,000 


.00345 


.00269 


.00238 


.00220 


.00199 


.00186 


.00178 


.00171 


750,000 


.00340 


.00266 


.00236 


.00218 


.00198 


.00185 


.00177 


.00170 


700,000 


.00335 


.00263 


.00233 


.00216 


.00196 


.00184 


.00175 


.00169 


600,000 


.00325 


.00257 


.00229 


.00212 


.00193 


.00181 


.00172 


.00166 


500,000 


.00314 


.00250 


.00223 


.00207 


.00189 


.00177 


.00169 


.00163 


450,000 


.00308 


.00246 


.00220 


.00205 


.00186 


.00175 


.00168 


.00162 


400,000 


.00302 


.00242 


.00216 


.00202 


.00184 


.00173 


.00166 


.00160 


350,000 


.00295 


.00237 


.00213 


.00199 


.00181 


.00171 


.00163 


.00158 


300,000 


.00287 


.00232 


.00209 


.00195 


.00178 


.00168 


.00161 


.00156 


250,000 


.00278 


.00226 


.00207 


.00191 


.00175 


.00165 


.00158 


.00153 


0000 


.00271 


.00222 


.00250 


.00188 


.00172 


.00163 


.00156 


.00151 


000 


.00261 


.00215 


.00195 


.00183 


.00168 


.00159 


.00153 


.00148 


00 


.00252 


.00209 


.00190 


.00178 


.00164 


.00156 


.00149 


.00145 





.00244 


.00203 


.00185 


.00174 


.00161 


.00152 


.00147 


.00142 


1 


.00235 


.00197 


.00180 


.00170 


.00157 


.00149 


.00143 


.00139 


2 


.00227 


.00192 


.00175 


.00165 


.00153 


.00146 


.00140 


.00136 


4 


.00214 


.00182 


.00167 


.00158 


.00147 


.00140 


.00135 


.00131 


Solid 6 


.00196 


.00169 


.00156 


.00148 


.00139 


.00132 


.00128 


.0012? 


Solid 8 


.00186 


.00162 


.00150 


.00143 


.00133 


.00128 


.00124 


.0012C 


Solid 10 


.00177 


.00155 


.00144 


.00137 


.00129 


.00123 


.00120 


.0011? 



* For stranded wires the last formula gives values about 3% too small. 



TRANSMISSION CIRCUITS. 



253 



Charging* Current in Amperei per lOOO JFeet of Single- 

Phase Circuit (2000 feet of Wire) Formed by 

Two Parallel Aerial Wires. 

Pressure, E = 10,000 Volts. Frequency, / = 100 Cycles per Second. 

Charging Current = 6.283 C. 

Note. — Values of charging current at other pressures and frequencies 
are proportional to those given in this table. 



oooo 
ooo 

00 


1 

2 

4 
5 



Interaxial Distances. 



Dia. 
over 
Insul, 



.04699 
.04542 
.04373 
04203 
.04040 
.04260 
. 03933 
.03776 
. 03619 
.03513 
.03399 
.03135 
.02834 



.03751 
. 03468 
.03009 
.02658 
.02387 
02161 



P 



03920 
03348 
03116 
02921 
02588 
. 02325 
02111 
01935 



.04498 
.04096 
.03757 
.03474 
.03229 
.03016 
.02664 
.02519 
.02387 
.02161 
.01973 
.01809 
.01684 



.03613 
.03355 
.03123 
.02921 
.02745 
.02595 
.02331 
.02218 
.02111 
.01935 
.01784 
.01658 
.01545 



.02456 
.02331 
.02218 
.02117 
.02023 
01935 
.01784 
.01721 
.01658 
.01545 
.01445 
.01363 
,01288 



.02067 
.0^979 
.01897 
.01822 
.01753 
.01690 
.01571 
.01520 
.01470 
.01382 
.01300 
.01231 
.01168 



.01627 
.01571 
. 01520 
.01470 
.01426 
.01382 
.01307 
.01269 
.01231 
,01168 
,01112 
,01061 
,01017 



12* 



.01344 
.01306 
.01269 
.01237 
.01200 
.01168 
.01112 
.01087 
.01062 
.01018 
00973 
,00929 
,00898 



18* 



.01218 
.01187 
.01156 
=01130 
.01099 
.01074 
.01024 
.01005 
.00980 
.00942 
.00905 
.00873 
.00842 



Size Cir. Mils 


Interaxial Distances. 
















Stranded. 


6" 


12" 


18" 


24" 
.01426 


36" 


48" 


60" 


72" 


1,000,000 


.02268 


.01753 


.01545 


.01281 


.01200 


.01143 


.01099 


900,000 


.02271 


.01721 


.01520 


.01401 


.01269 


.01187 


.01131 


.01087 


800,000 


.02167 


.01690 


.01495 


.01382 


.01250 


.01168 


.01118 


.01074 


750,000 


.02136 


.01671 


.01483 


.01369 


.01244 


.01162 


.01112 


.01068 


700,000 


.02105 


.01654 


.01404 


.01357 


.01231 


.01156 


.01099 


.01062 


600,000 


.02042 


.01615 


.01430 


.01332 


.01213 


.01137 


.01081 


.01043 


500,000 


.01972 


.01571 


.01401 


.01300 


.01187 


.01112 


.01062 


.01024 


450,000 


.01935 


.01545 


.013S2 


.01288 


.01168 


.01099 


.01055 


.01018 


400,000 


.01897 


.01520 


.01363 


.01269 


.01156 


.01086 


.01043 


.01005 


350,000 


.01853 


.01489 


.01338 


.01250 


.01137 


.01074 


.01024 


.00993 


300,000 


.01803 


.01457 


.01313 


.01225 


.01118 


.01055 


.01011 


.00980 


250,000 


.01746 


.01426 


.01300 


.01200 


.01099 


.01036 


.00993 


.00961 


0000 


.01702 


.01395 


.01256 


.01181 


.01080 


.01024 


.00980 


.00949 


000 


.01640 


.01351 


.01225 


.01149 


.01055 


.00999 


.00961 


.00930 


00 


.01583 


.01313 


.01194 


.01118 


.01030 


.00980 


.00936 


.00911 





.01533 


.01275 


.01162 


.01093 


.01011 


.00955 


.00923 


.00892 


1 


.01476 


.01238 


.01131 


.01068 


.00986 


.00936 


.00898 


.00873 


2 


.01426 


.01206 


.01099 


.01043 


.00961 


.00917 


.00879 


.00854 


4 


.01344 


.01143 


.01049 


.00993 


.00923 


.00879 


.00848 


.00823 


Solid 6 


.01231 


.01062 


.00980 


.00936 


.00873 


.00829 


.00804 


.00785 


Solid 8 


.01168 


.01011 


.00942 


.00898 


.00835 


.00804 


.00779 


.00754 


Solid 10 


.01112 


.00973 


.00905 


.00861 


.00810 


.00773 


.00754 


.00735 



10 



254 



CONDUCTORS. 



Charging- Current in Amperes per lOOO Feet of Single* 
Phase Circuit (2000 feet of Wire) formed i>j 
Two Parallel Aerial Wires. 

Pressure, E = 10,000 Volts. Frequency, / =» 25 Cycles per Second. 

Charging Current = 1.571 C. 

Note. — Values of charging current at other pressures are proportional 
to those given in this table. 



e . 










Interaxial Distances. 








GO ^ 




#£ 


Dia. 
















/A 


over 


i" 


*" 


r 


1" 


2" 


3" 


6" 


12" 


18" 


PQ 


Insul. 




















0000 


.01175 






.01124 


. 00903 


.00614 


.0051 


7 .0040 


7 .00336 


.00305 


000 


.01135 


«... 




. 01024 


.00839 


. 00583 


.0049 


5 .0039 


3 .00326 


.00297 


00 


. 01093 






.00939 


. 00781 


.00554 


.0047 


4 .0038 


) .00317 


.00289 





.01051 






.00868 


. 00730 


.00529 


.0045 


5 .0036 


7 .00309 


.00282 


1 


. 01010 






.00807 


. 00686 


.00506 


.0043 


8 .0035 


3 .00300 


.00275 


2 


. 01065 


.... 


.00980 


.00754 


.00649 


.00484 


.0042 


2 .0034, 


5 .00292 


.00268 


4 


.00983 




.00837 


. 00666 


.00583 


.00446 


.0039 


3 .0032 


7 .00278 


.00256 


5 


.00944 


.00938 


.00779 


.00630 


.00554 


. 00430 


.0038 


.0031 


J .00272 


.00251 


6 


. 00905 


. 00867 


. 00730 


. 00597 


. 00528 


. 00414 


.0036 


7 .0030* 


1 .00265 


. 00245 


8 


. 00928 


. 00752 


.00647 


.00540 


. 00484 


. 00386 


.0034 


5 .0029i 


I .00254 


.00235 


10 


.00850 


. 00664 


. 00581 


.00493 


.00446 


.00361 


.0032, 


5 .0027* 


* .00243 


.00226 


12 


. 00784 


.00597 


. 00528 


.00452 


.00414 


.00341 


.0030 


3 .0026* 


) .00232 


.00218 


14 


.00721 


.00540 


.00484 


.00421 


.00386 


.00322 


.0029 


2 .002# 


[ .00224 


. 00210 




Interaxial Distances. 


Size Cir. Mils 














Stranded. 


6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.0056 


7 .00438 


.00386 


.00356 


.00320 


.00300 


.00286 


.00275 


900,000 


.0055 


4 .00430 


.00380 


.00350 


.00317 


.00297 


.00283 


.00272 


800,000 


.0054 


2 .00422 


.00374 


.00345 


.00312 


.00292 


.00279 


.00268 


750,000 


.0053 


4 .00418 


.00371 


.00342 


.00311 


.00290 


.00278 


.00267 


700,000 


.0052 


6 .00414 


.00366 


.00339 


.00308 


.00289 


.00275 


.00265 


600,000 


.0051 


3 .00404 


.00360 


.00335 


.00303 


.00284 


.00270 


.00261 


500,000 


.0049 


3 .00393 


.00350 


.00325 


.00297 


.00278 


.00265 


.00256 


450,000 


.0048 


4 .00386 


. 00345 


.00322 


.00292 


.00275 


.00264 


.00254 


400,000 


.0047 


1 .00380 


.00341 


.00317 


.00289 


.00271 


.00261 


.00251 


350,000 


.0046 


3 .00372 


.00334 


.00312 


.00284 


.00268 


.00256 


.00248 


300,000 


.0045 


L .00364 


.00328 


.00306 


.00279 


.00264 


.00253 


.00245 


250,000 


.00431 


3 .00356 


.00325 


.00300 


.00275 


00259 


.00248 


.00240 


0000 


.0042^ 


5 .00349 


.00314 


.00295 


.00270 


00256 


.00245 


.00237 


000 


.004K 


) .00338 


.00306 


.00287 


.00264 


00250 


.00240 


.00232 


00 


.0039( 


3 .00328 


.00298 


.00279 


.00257 


00245 


.00234 


.00228 





.0038: 


J .00319 


.00290 


.00273 


.00253 


00239 


.00231 


.00223 


1 


.0036< 


) .00309 


.00283 


.00267 


.00246 


00234 


.00224 


.00218 


2 


.0035( 


) .00301 


.00275 


.00261 


.00240 . 


00229 


.00220 


.00213 


4 


.0033( 


5 .00286 


.00262 


.00248 


.00231 . 


00220 


.00212 


.00206 


Bolid 6 


.0030£ 


I .00265 


.00245 


.00234 


.00218 . 


00207 


.00201 


.00196 


Solid 8 


.0029S 


5 .00253 


.00235 


.00224 


.00209 . 


00201 


00195 


.00188 


Solid 10 


.0027£ 


1 .00243 


.00226 


.00215 


.00202 . 


00193 .00188 


.00184 



TRANSMISSION CIRCUITS. 



255 



Charging* Current in Amperes per lOOO feet of Single^ 

Phase Circuit (SOOO JFeet of Wire) Formed by 

Iwo Parallel Aerial Wires. 

Pressure, E = 10,000 Volts. Frequency, / = 60 Cycles per Second. 

Charging Current = 3.77 C. 

Note. — Values of charging current at other pressures are proportional 
to those given in this table. 



. 

ad 3 








Interaxial Distances. 












Dia. 
over 
Insul. 


3// 
8 


2 


3// 
4 


1" 


2" 


3" 


6" 


12" 


18* 


noon 


.02819 
.02725 
.02623 
.02521 
.02424 
.02556 
.02359 
.02265 
.02171 
.02227 
.02039 
.01881 
.01730 






.02698 


.02167 
.02013 
.01873 
.01752 
.01647 
.01557 
.01398 
.01331 
.01266 
.01161 
.01070 
.00995 
.00927 


.01473 
.01398 
.01330 
.01270 
.01213 
.01161 
.01070 
.01032 
.00994 
.00927 
.00867 
.00817 
.00772 


.01240 
.01187 
.01138 
.01093 
.01051 
.01014 
.00942 
.00912 
.00882 
.00829 
.00780 
.00738 
.00700 


.00976 
.00942 
.00912 
.00882 
.00855 
.00829 
.00784 
.00761 
.00738 
.00700 
.00667 
.00636 
.00610 


.00806 
.00783 
.00761 
.00742 
.00720 
.00700 
.00667 
.00652 
.00637 
.00611 
.00583 
.00557 
.00538 


.00731 
.00712 
.00693 
.00678 
.00659 
.00644 
.00614 
.00603 
.00588 
.00565 
.00543 
.00523 
.00505 


000 






.02457 


00 






.02254 









.02084 


i 






.01937 


? 




.02352 


.01809 
.01598 
.01511 
.01432 
.01296 
.01183 
.01085 
.01010 


4 




.02008 


5 

6 

8 

10 

12 

14 


.02251 
.02080 
.01805 
.01595 
.01432 
.01296 


.01869 
.01752 
.01552 
.01395 
.01266 
.01161 



Size Cir. Mils 


Interaxial Distances. 


















Stranded. 


6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.01360 


.01052 


.00927 


.00855 


.00768 


.00720 


.00686 


.00659 


900,000 


.01330 


.01032 


.00912 


.00840 


.00761 


.00712 


.00678 


.00652 


800,000 


.01300 


.01014 


.00897 


.00829 


.00750 


.00700 


.00670 


.00644 


750,000 


.01281 


.01002 


.00889 


.00821 


.00746 


.00697 


.00667 


.00640 


700,000 


.01263 


.00993 


.00878 


.00814 


.00738 


.00693 


.00659 


.00636 


600,000 


.01224 


.00969 


.00863 


.00800 


.00727 


.00682 


.00648 


.00625 


500,000 


.01183 


.00942 


.00840 


.00780 


.00712 


.00667 


.00637 


.00614 


450,000 


.01161 


.00927 


.00829 


.00772 


.00700 


.00659 


.00633 


.00610 


400,000 


.01138 


.00912 


.00817 


.00761 


.00693 


.00651 


.00625 


.00603 


350,000 


.01111 


.00893 


.00802 


.00750 


.00682 


.00644 


.00614 


.00596 


300,000 


.01081 


.00874 


.00787 


.00735 


.00670 


.00633 


.00606 


.00588 


250,000 


.01047 


.00855 


.00780 


.00720 


.00659 


.00621 


.00596 


.00576 


0000 


.01021 


.00837 


.00753 


.00708 


.00648 


.00614 


.00588 


.00569 


000 


.00984 


.00810 


.00735 


.00689 


.00633 


.00599 


.00576 


.00558 


00 


.00949 


.00787 


.00716 


.00670 


.00618 


.00588 


.00561 


.00546 





.00919 


.00765 


.00697 


.00655 


.00606 


.00573 


.00553 


.00535 


1 


.00885 


.00742 


.00678 


.00640 


.00591 


.00561 


.00538 


.0052; 


2 


.00855 


.00723 


.00659 


.00626 


.00576 


.00550 


.00527 


.00512 


4 


.00806 


.00685 


.00629 


.00595 


.00553 


.00527 


.00508 


.00493 


Bolid 6 


.00738 


.00636 


.00588 


.00561 


.00523 


.00497 


.00482 


.00471 


Solid 8 


.00700 


.00606 


.00565 


.00538 


.00501 


.00482 


.00467 


.00452 


Solid 10 


.00667 


.00583 


.00543 


.00516 


.00486 .00464 


.00452 


.00441 



256 



CONDUCTORS. 



Charging* Current in Ampere.* per Wire per lOOO feet 

of Three-Phase Circuit Formi'il Uy Three Parallel 

Aerial Wires. 

Pressure between Wires, E = 10,000 Volts. Frequency, / = 100 Cycles 
per Second. 

Charging Current per Wire = 7.26 C. 

Note. — Values of charging current at other pressures and frequencies 
are proportional to those given in this table. 











Interaxial Distances. 










Dia. 
over 
Insul. 


r 


¥ 


3." 

4 


1" 


2" 


3" 


6" 


12" 


18" 


0000 


.05430 
.05249 
.05053 
.04857 
.04668 
.04922 
.04545 
.04363 
.04182 
.04291 
.03928 
.03623 
.03332 






.05198 


.04174 
.03877 
.03608 
.03376 
.03173 
.02998 
.02693 
.02563 
.02439 
.02236 
.02062 
.01917 
.01786 


.02839 
.02693 
.02563 
.02447 
.02338 
.02236 
.02062 
.01989 
.01917 
.01786 
.01670 
.01575 
.01488 


.02388 
.02287 
.02192 
.02105 
.02025 
.01953 
.01815 
.01757 
.01699 
.01597 
.01503 
.01423 
.01350 


.01880 
.01815 
.01757 
.01699 
.01648 
.01597 
.01510 
.01466 
.01423 
.01350 
.01285 
.01227 
.01176 


.01554 
.01510 
.01466 
.01430 
.01387 
.01350 
.01285 
.01256 
.01227 
.01176 
.01125 
.01074 
.01038 


.01408 


000 






.04733 


.01372 


00 






.04341 


.01336 


o 






.04015 


.01307 


1 






.03732 


.01270 


2 




.04530 


.03485 
.03078 
.02911 
.02759 
.02497 
.02280 
.02091 
.01946 


.01241 


4 




.03869 


.01183 


5 

6 

8 

10 

12 

14 


.04334 
.04007 
.03477 
.03071 
.02759 
.02497 


.03601 
.03376 
.02991 
.02686 
.02439 
.02236 


.01162 
.01132 
.01089 
.01045 
.01009 
.00973 





Interaxial Distances. 


Size Cir. Mils 
Stranded. 






















6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.02621 


.02025 


.01786 


.01648 


.01481 


.01387 


.01321 


.01270 


900,000 


.02563 


.01989 


.01757 


.01619 


.01466 


.01372 


.01307 


.01256 


800,000 


.02505 


.01953 


.01728 


.01597 


.01445 


.01350 


.01292 


.01241 


750,000 


.02468 


.01931 


.01713 


.01583 


.01437 


.01343 


.01285 


.01234 


700,000 


.02432 


.01911 


.01691 


.01568 


.01423 


.01336 


.01270 


.01227 


600,000 


.02359 


.01866 


.01662 


.01539 


.01401 


.01314 


.01249 


.01205 


500,000 


.02280 


.01815 


.01619 


.01503 


.01372 


.01285 


.01227 


.01183 


450,000 


.02236 


.01786 


.01597 


.01488 


.01350 


.01270 


.01220 


.01176 


400,000 


.02192 


.01757 


.01568 


.01466 


.01336 


.01256 


.01205 


.01161 


350,000 


.02142 


.01721 


.01546 


.01445 


.01314 


.01241 


.01183 


.01147 


300,000 


.02084 


.01684 


.01517 


.01416 


.01292 


.01220 


.01169 


.01132 


250,000 


.02018 


.01641 


.01503 


.01387 


.01270 


.01198 


.01147 


.01111 


0000 


.01967 


.01612 


.01452 


.01365 


.01249 


.01183 


.01132 


.01096 


000 


.01895 


.01561 


.01416 


.01328 


.01220 


.01154 


.01111 


.01074 


00 


.01829 


.01517 


.01379 


.01292 


.01191 


.01132 


.01082 


.01053 





.01771 


.01474 


.01343 


.01263 


.01169 


.01103 


.01067 


.01031 


1 


.01706 


.01430 


.01307 


.01234 


.01140 


.01082 


.01038 


.01009 


2 


.01648 


.01394 


.01270 


.01198 


.01111 


.01060 


.01016 


.00987 


4 


.01554 


.01321 


.01212 


.01147 


.01067 


.01016 


.00980 


.00951 


Solid 6 


.01423 


.01227 


.01132 


.01074 


.01009 


.00958 


.00929 


.00907 


Solid 8 


.01350 


.01176 


.01089 


.01038 


.00965 


.00929 


.00900 


.00871 


Solid 10 


.01285 


.01125 


.01045 


.00995 


.00936 


.00893 


.00871 


.00849 



TRANSMISSION CIRCUITS. 



257 



Charging* Current in Amperes per \\ ire per lOOO Feet 

of Three-Phase Circuit Formed by Three Parallel 

Aerial Wire*. 

Pressure between Wires, E= 10,000 Volts. Frequency, / = 25 Cycles 

per Second. 

Charging Current per Wire = 1.815 C. 

Note. — Values of charging current at other pressures are proportional 
to those given in this table. 



ml 

*5 



Interaxial Distances. 



1000 

000 

00 



1 

2 

4 

5 

6 

8 

10 

12 

14 



Dia. 
over 
Insul. 



.01358 
.01312 
.01263 
.01214 
.01167 
.01230 
.01136 
.01091 
.01045 
.01073 
.00982 
.00906 
.00833 



.01083 
.01002 
.00869 
.00768 
.00690 
.00624 



.01132 
.00967 
.00900 
.00844 
.00748 
.00671 
.00610 
.00559 



.01299 
.01183 
.01085 
.01004 
.00933 
.00871 
.00769 
.00728 
.00690 
.00624 
.00570 
.00523 
.00486 



.01044 
.00969 
.00902 
.00844 
.00793 
.00749 
.00673 
.00641 
.00610 
.00559 
.00515 
.00479 
.00446 



.00710 
.00673 
.00641 
.00612 
.00584 
.00559 
.00515 
.00497 
.00479 
.00446 
.00417 
.00394 
.00372 



.00597 
.00572 
.00548 
.00526 
.00506 
.00488 
.00454 
.00439 
.00425 
.00399 
.00376 
.00356 
.00337 



6" 



.00470 
.00454 
.00439 
.00425 
.00412 
.00399 
.00377 
.00367 
.00356 
.00337 
.00321 
.00307 
.00294 



12" 



.00388 
.00377 
.00367 
.00357 
.00347 
.00337 
.00321 
.00314 
.00307 
.00294 
.00281 
.00269 
.00259 



18" 



.00352 
.00343 
.00334 
.00327 
.0031S 
.00310 
.00296 
.0029C 
.00282 
.0027S 
.00261 
.00255 
.0024c 









Interaxial Distances. 






Size Cir. Mils 




Stranded. 




















6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


1,000,000 


.00655 


.00506 


.00446 


.00412 


.00370 


.00347 


.00330 


.00318 


900,000 


.00641 


.00497 


.00439 


.00405 


.00367 


.00343 


.00327 


.00314 


800,000 


.00626 


.00488 


.00432 


.00399 


.00361 


.00337 


.00323 


.00310 


750 000 


.00617 


.00483 


.00428 


.00396 


.00359 


.00336 


.00321 


.00308 


700,000 


.00608 


.00478 


.00423 


.00392 


.00356 


.00334 


.00318 


.00307 


600,000 


.00590 


.00466 


.00416 


.00385 


.00350 


.00328 


.00312 


.00301 


500,000 


.00570 


.00454 


.00405 


.00376 


.00343 


.00321 


.00307 


.00296 


450,000 


.00559 


. 00446 


. 00399 


.00372 


.00337 


.00318 


.00305 


.00294 


400,000 


.00548 


.00439 


.00392 


.00367 


.00334 


.00314 


.00301 


.00290 


350,000 


.00535 


.00430 


.00386 


.00361 


.00328 


.00310 


.00296 


.00287 


300,000 


.00521 


.00421 


.00379 


.00354 


.00323 


.00305 


.00292 


.00283 


250,000 


.00504 


.00410 


.00376 


.00347 


.00318 


.00299 


.00287 


.00278 


0000 


.00492 


.00403 


.00363 


.00341 


.00312 


.00296 


.00283 


.00274 


000 


.00474 


.00390 


.00354 


.00332 


.00305 


.00288 


.00278 


.00269 


00 


.00457 


.00379 


.00345 


.00323 


.00298 


.00283 


.00270 


.00263 





.00443 


.00368 


.00336 


.00316 


.00292 


.00276 


.00267 


.00258 


1 


.00426 


.00357 


.00327 


.00308 


.00285 


.00270 


.00259 


.00252 


2 


.00412 


.00348 


.00318 


.00299 


.00278 


.00265 


.00254 


.00247 


4 


.00388 


.00330 


.00303 


.00287 


.00267 


.00254 


.00245 


.00238 


Solid 6 


.00356 


.00307 


.00283 


.00269 


.00252 


.00239 


.00232 


.00227 


Solid 8 


.00337 


.00294 


.00272 


.00259 


.00241 


.00232 


.00225 


.00218 


Solid 10 


.00321 


.00281 


.00261 


.00249 


.00234 


.00223 


.00218 


.00212 



258 



CONDUCTORS. 



Charging- Current in Amperes per Wire per lOOO Feet of 

Three-Phase Circuit formed hv Three Parallel 

Aerial Wires. 

Pressure between Wires, E = 10,000 Volts Frequency, /= 60 Cycles 

per Second. 

Charging Current per Wire = 4.356 C. 

Note. — Values of charging current at other pressures are propor- 
tional to those given in this table. 



4d 

t/5 "5 








Interaxial Distances. 








^ o 


Dia. 
over 
Insul. 


1" 


2 


4 


1" 


2" 


3" 


6" 


12" 


18* 


3000 


.03258 
.03149 
.03032 
.02914 
.02801 
.02953 
.02727 
.02618 
.02509 
.02574 
.02356 
.02174 
.01999 






.03119 


.02505 
.02326 
.02165 
.02025 
.01903 
.01799 
.01616 
.01538 
.01464 
.01342 
.01237 
.01150 
.01071 


.01703 
.01616 
.01538 
.01468 
.01403 
.01342 
.01237 
.01193 
.01150 
.01071 
.01002 
.00945 
.00893 


.01433 
.01372 
.01315 
.01263 
.01215 
.01172 
.01089 
01054 
.01019 
.00958 
.00902 
.00854 
.00810 


.01128 
.01089 
.01054 
.01019 
.00989 
.00958 
.00906 
.00880 
.00854 
.00810 
.00771 
.00736 
.00706 


.00932 


.00845 


000 






.02840 


.00906) .00823 


00 






.02605 


.00880 .00801 


o 






.02409 


.00858 
.00832 
.00810 
.00771 
.00753 
.00736 
.00706 
.00675 
.00645 
.00623 


.00784 


1 






.02239 


.00762 


2 




.02718 


.02091 
.01847 
.01747 
.01655 
.01498 
.01368 
.01254 
.01167 


.00745 


4 




. 02322 


.00710 


5 

6 

8 

10 

12 

14 


.02600 
.02404 
.02086 
.01842 
.01655 
.01498 


.02160 
.02025 
.01795 
.01612 
.01464 
.01342 


.00697 
.00679 
.00653 
.00627 
.00605 
.00584 









Interaxial Distances. 






Size Cir. Mils 


















Stranded. 


6" 


12" 


18" 


24" 


36" 


48" 


60" 


72" 


2,000,000 


.01847 


.01372 


.01189 


.01089 


.00971 


.00906 


.00858 


.00823 


1,500,000 


.01721 


.01298 


.01137 


.01045 


.00936 


.00871 


.00828 


.00793 


1,250,000 


.01651 


.01259 


.01106 


.01019 


.00915 


.00854 


.00810 


.00780 


1,000,000 


.01572 


.01215 


.01071 


.00989 


. 00889 


.00832 


.00793 


.00762 


900,000 


.01538 


.01193 


.01054 


.00971 


.00880 


.00823 


.00784 


.00753 


800,000 


.01503 


.01172 


.01037 


.00958 


.00867 


.00810 


.00775 


.00745 


750,000 


.01481 


.01159 


.01028 


.00950 


. 00862 


.00806 


.00771 


.00740 


700,000 


.01459 


.01147 


.01015 


.00941 


.00854 


.00801 


.00762 


.00736 


600,000 


.01416 


.01119 


.00997 


.00923 


.00841 


.00788 


.00749 


.00723 


500,000 


.01368 


.01089 


.00971 


.00902 


.00823 


.00771 


.00736 


.00710 


450,000 


.01342 


.01071 


.00958 


.00893 


.00810 


.00762 


.00732 


.00706 


400,000 


.01315 


.01054 


.00941 


.00880 


.00801 


.00753 


.00723 


.00697 


350,000 


.01285 


.01032 


.00928 


.00867 


.00788 


.00745 


.00710 


.00688 


300,000 


.01250 


.01010 


.00910 


.00849 


.00775 


.00732 


.00701 


.00679 


250,000 


.01211 


.00984 


.00902 


.00832 


.00762 


.00719 


. 00688 


.00666 


0000 


.01180 


.00967 


.00871 


.00819 


.00749 


.00710 


.00679 


.00658 


000 


.01137 


.00936 


.00849 


.00797 


.00732 


.00693 


.00666 


.00645 


00 


.01098 


.00910 


.00828 


.00775 


.00714 


.00679 


.00649 


.00632 





.01063 


.00884 


.00806 


.00758 


.00701 


.00662 


.00640 


.00618 


1 


.01024 


.00858 


.00784 


.00740 


.00684 


.00649 


.00623 


.00605 


2 


.00989 


.00836 


.00762 


.00719 


.00666 


.00636 


.00610 


.00592 


4 


.00932 


.00793 


.00727 


.00688 


.00640 


.00610 


.00588 


.00571 


Solid 6 


.00854 


.00736 


.00679 


.00645 


.00605 


.00575 


.00557 


.00544 


Solid 8 


.00810 


.00706 


.00653 


.00623 


.00579 


.00557 


.00540 


.06523 


Solid 10 


.00771 


.00675 


.00627 


.00597 


.00562 


.00536 


.00523 


.00510 



ALTERNATING CURRENT CIRCUITS. 



259 



SI UIMLV ALTERNATING CVRREX1 CIRCUITS. 

The impedance (z) of a circuit is defined as the ratio of the difference in 
pressure (effective) between the two ends of the conductor to the current 
(effective) flowing through the conductor. 

The E.M.F. required to overcome impedance is 

E = Iz. 

In the case of direct currents z = r. 

The following are typical alternating current circuits: 



Let 



R = resistance in ohms. 

Z = impedance. 

w = 2 *7. 

L = coefficient of self induction. 

C = capacity. 



Resistance and Inductance, in Series. 

Z = Vfl2 + L2«2, 



or diagrammatically 




Fig. 12. 

Resistance and Capacity in Series. 

Z = 



or diagrammatically, 




Fig. 13. 



Resistance, Inductance, and Capacity in Series. 

z - y/jp + (x-- 5J. 




or diagrammatically, 



Note. — In transmission lines the capacity is in parallel with the resist- 
ance and inductance; the above formulae involving capacity do not there* 
fore apply. For the discussion of capacity of transmission lines see p. 264. 



260 CONDUCTORS. 



THE DIMENSIONS OF CONDUCTORS FOR 
DISTRIBUTION SYSTEMS. 

By Harold Pender, Ph.D. 

To proportion properly the size of the conductors for a distribution 
system, the following data with regard to each circuit is necessary: 

1. The maximum power to be transmitted, or the maximum load on the 

line. 

2. The load factor, or the variation of the power delivered with time. 

3. The length of the line. 

4. The distribution of the load along the line. 

5. The pressure at which the power is to be transmitted. 

6. The loss of power which may be allowed in the line. 

These six conditions will determine a conductor of a definite cross sec- 
tion, but no conductor should ever be used which is not of sufficient size 
both to insure the proper mechanical strength and also to prevent a dan- 
gerous temperature elevation; the first condition is of particular impor- 
tance in overhead lines, the second in underground and interior wiring. 

Assuming that the amount and distribution of the load and the trans- 
mission distance are known, the engineer has next to determine what line 
pressure to employ and what power loss to allow. To do this, he must 
keep in mind two fundamental facts, namely, that the transmission system 
is but part of the entire plant, and that the object of the plant as a whole 
is to gain the maximum net revenue for the least expenditure of money; 
also, that there is usually a limit to the capital available for the enter- 
prise, which the first cost of the entire plant must not exceed, even though 
a further increase of the capital outlay might gain a desirable revenue. 
Consequently, in the selection of the pressure and efficiency for a distribu- 
tion system, many complex factors enter, such as the nature of 
the supply of energy, the nature of the load supplied, the probability of 
increase in the demand for power, etc., as well as the relative costs of the 
various parts of the plant. Space does not permit of a detailed discus- 
sion of all these factors here; it will suffice to state briefly the general Amer- 
ican practice under the most common conditions. 

lilME PRE§§€RE. — To transmit a given amount of power a given 
distance at a fixed efficiency, the amount of copper required will vary 
inversely as the square of the pressure. High pressure then means de- 
crease in the cost of the conducting material, but an increase in the cost 
of insulating the line and the rest of the system. As a general rule, espe- 
cially in longdistance transmission, the saving in copper as the pressure 
is increased more than offsets the increased cost of insulation, up to about 
60,000 volts, but in many cases other factors fix a much lower economical 
limit to the line pressure. Recent improvements in the design of insula- 
tors accompanied by a decrease cost of manufacture have raised the 
economic limit of line pressure to 100,000 volts. 

Direct Current Distribution. — On direct current systems supply- 
ing directly incandescent lamps and small motors, the maximum pressure 
allowable is 125 volts for two-wire distribution, 250 volts for three-wire 
distribution; in certain cases where cheap power may be had, these figures 
may be increased to 250 and 500 respectively. For large direct current 
motor systems the corresponding figures are 500 to 600 volts for two-wire 
and 1000 to 1200 volts for three-wire systems. The limiting transmission 
pressure is fixed by the maximum pressure which can be employed on the 
various translating devices, motors, lamps, and the like. Future devel- 
opments in the latter may set a new limit to the allowable pressure; in 
fact, the compensating pole direct current motors now being placed on the 
market will permit the use of pressure as high as 1200 volts for two-wire 
and 2400 volts for three-wire systems. On circuits supplying direct cur- 
rent series arc lamps, pressures as high as 5000 volts are used. 



DIMENSIONS OF CONDUCTORS. 261 

Alternating: Current Distribution. — The line pressure on that 
part of an alternating current distribution system connected directly to 
the various translating devices, motors, lamps, and the like, is fixed by 
the practicable pressure that may be used on these devices. For direct 
distribution for incandescent lighting, the line pressure between wires 
should not exceed 125 volts, or possibly 250 volts if power is cheap and 
220 to 250 volt incandescent lamps can be advantageously employed. 

Distribution in Cities. — In the larger cities the tendency of modern 
practice (1907) is to generate three-phase alternating current at 11,000 
or 13,000 volts (delta), and to transmit the power at this pressure either 
to static transformer or rotary converter sub-stations. For the dis- 
tribution of direct current from rotary converter sub-stations see above 
under "Line Pressure for Direct Current Distribution." At the static 
transformer sub-stations the pressure is reduced to 2200 volts, and the 
power transmitted at this pressure to the centers of distribution, where 
another reduction in pressure to about 125 or 250 volts takes place, and 
from here the energy is distributed directly to the lamps, motors, or 
other translating device. In smaller cities, or when it is desired to employ 
overhead lines entirely (since 11,000 volts overhead in cities is not advis- 
able), the sub-stations may be omitted and generators for 2200 volts be 
used. Large induction motors may be supplied directly with 2200 volt 
current, the very largest sometimes with current at 11,000 or 13,000 volts. 

POWER LOi§ I]¥ THE MWJE. — To transmit a given amount 
of power a given distance at a given pressure, the amount of copper 
required will vary inversely as the amount of power lost in transmission. 
Low efficiency, therefore, means decrease in the cost of the conducting 
material, but an increase in the central station output. 

Kelvin's law, — In general, if two quantities A and B are both func- 
tions of the same variable x, then the sum of A + B is a minimum when 
the rate of change of A with respect to that variable is equal and opposite 
to the rate of change of B with respect to that variable, i.e., when 

dA = _dB t 

dx dx 

Numerous attempts have been made to apply this law to the determi- 
nation of the most economical efficiency for a transmission line. At first 
sight it would seem logical to proportion the costs of the central station 
and transmission line so that the annual cost of delivering an additional 
kilowatt of power by increasing the central station capacity will equal the 
annual cost of delivering an additional kilowatt of power by adding 
more copper to the line. On this basis a very simple law is found to hold, 
namely, that the most economical current density per million circular 
mils is * 

/Kc 
Kp* 

where Kc = increase in annual charges on transmission line, resulting 
from increasing the weight of copper one ton (2000 lbs.), and Kp = increase 
in annual operating and capital charges on the central station, resulting from 
increasing the output one kilowatt. 

This law, however, is true only for a given current; when the power sup- 
plied by any plant, and therefore the current, varies over wide limits 
during the year, as is almost invariably the case, the current density as 
determined by the above law refers to the square root of the mean square 
current for the year, a quantity which can be determined only to the 
roughest approximation. 

Further, the whole discussion of economical cross section is based on 
two assumptions, usually unwarranted, namely, that the amount of capital 
available is unlimited, and that a market can be found for the maximum 
output of the plant; it will evidently not be economical to install copper 
to save power which cannot be sold. In short, neither Kelvin's law nor 



380 y/^ 



The formula for aluminum is 165 



V K, 



262 CONDUCTORS. 



any modification of it is a safe general guide in determining the proper 
allowance for loss of power in the line. Each plant has to be considered 
on its individual merits, and various conditions are likely to determine the 
pressure and loss in different cases. 

Distribution Direct to translating: Devices. — The power loss 
in a transmission line also fixes the pressure loss or volts drop. In direct 
current systems the per cent power loss equals the per cent pressure loss; 
in an alternating current line there is also a fixed relation between the two, 
see page 264. In that part of a distribution system connected directly 
to the translating devices, lamps, motors, etc., the regulation of the line, 
or the percentage pressure loss, must not exceed a certain amount con- 
sistent with reasonably" efficient operation of these translating devices. 
For example, the maximum variation in pressure on incandescent lamps 
should not be more than 2 per cent; distribution lines which supply incan- 
descent lamps and on which the pressure at the sending end is fixed, 
should therefore be of sufficient size to insure a pressure loss of not over 2 
per cent at maximum load. When a line supplies a large number of lamps, 
all of which are not likely to be burning simultaneously, the per cent drop 
in pressure for the connected load may be taken considerably greater. 
For example, if the probable maximum load be figured at one third of 
the connected load, a drop of 6 per cent for all lamps burning may be 
allowed. 

Distribution in General. — The following discussion of the proper 
power loss to allow in transmission lines is taken from Bell, "Electric 
Power Transmission." 

"The commonest cases which arise are as follows, arranged in order of 
their frequency as occurring in American practice. Each case requires a 
somewhat different treatment in the matter of line loss, and the whole 
classification is the result not of a priori reasoning but of the study of a 
very large number of concrete cases. 

Case I. General distribution of power and light from water-power. 
This includes something like two thirds of all the power transmission enter- 
prises. The cases which have been investigated by the author have ranged 
from 100 to 20,000 H.P., to be transmitted all the way from one to one 
hundred and fifty miles. The market for power and light is usually uncer- 
tain, the proposition of power to light unknown within wide limits, and the 
total amount required only to be determined by future conditions. The 
average load defies even approximate estimation, and as a rule even when the 
general character of the market is most carefully investigated little certainty 
is gained. 

For one without the gift of prophecy the attempt to figure the line for 
such a transmission by following any canonical rules for maximum econ- 
omy is merely the wildest sort of guesswork. The safest process is as fol- 
lows: Assume an amount of power to be transmitted which can certainly 
be disposed of. Figure the line for an assumed loss of energy at full load 
small enough to insure good and easy regulation, which determines the 
quality of the service, and hence, in large measure, its growth. Arrange 
both power station and line w T ith reference to subsequent increase if needed. 
The exact line loss assumed is more a result of trained judgment than of 
formal calculation. It will be in general between 5 and 15 per cent, for 
which losses generators can be conveniently regulated. If raising and 
lowering transformers are used the losses of energy in them should be in- 
cluded in the estimate for total loss in the line. In this case the loss in the 
line proper should seldom exceed 10 per cent. A loss of less than 5 per 
cent is seldom advisable. 

It should not be forgotten that in an alternating circuit two small con- 
ductors are generally better than one large one, so that the labor of installa- 
tion often will not be increased by waiting for developments before adding 
to the line. It frequently happens, too, that it is very necessary to keep 
down the first cost of installation, to lessen the financial burden during the 
early stages of a plant's development. 

Case II. Delivery of a known amount of power from ample water- 
power. This condition frequently arises in connection with manufactur- 
ing establishments. A water-power is bought or leased in toto, and the 
problem consists of transmitting sufficient power for the comparatively 
fixed needs of the works. The total amount is generally not laree seJdorq 



DIMENSIONS OF CONDUCTORS. 263 



more than a few hundred horse-power. Under these circumstances the 
plant should be designed for minimum first cost, and any loss in the line 
is permissible that does not lower the efficiency enough to force the use 
of larger sizes of dynamos and water-wheels. These sizes almost invari- 
ably are near enough together to involve no trouble in regulation if the 
line be thus designed. The operating expense becomes practically a fixed 
charge so that the first cost only need be considered. 

Such plants are increasingly common. A brief trial calculation will 
show at once the conditions of economy and the way to meet them. 

Case III. Delivery of a known power from a closely limited source. 
This case resembles the last, except that there is a definite limit set for the 
losses in the system. Instead, then, of fixing a loss in the line based on regu- 
lation and first cost alone, the first necessity is to deliver the required 
power. This may call for a line more expensive than would be indicated 
by any of the formulae for maximum economy, since it is far more impor- 
tant to avoid a supplementary steam plant entirely than to escape a con- 
siderable increase in cost of line. The data to be seriously considered are 
the cost of maintaining such a supplementary plant properly capitalized, 
and the price of the additional copper that render it unnecessary. Maxi- 
mum efficiency is here the governing factor. In cases where the motive- 
power is rented or derived from steam, formulae like Kelvin's may some- 
times be convenient. Losses in the line will often be as low as 5 per cent, 
sometimes only 2 or 3. 

Case IV. Distribution of power in known amount and units, with or 
without long distance transmission, with motive-power which, like steam 
or rented water-power costs a certain amount per horse-power. Here the 
desideratum is minimum cost per H.P., and design for this purpose may 
be carried out with fair accuracy. Small line loss is generally desirable 
unless the system is complicated by a long transmission. Such problems 
usually or often appear as distributions only. Where electric motors are 
in competition with distribution by shafting, rope transmission, and the 
like, 2 to 5 per cent line loss may advantageously be used in a trial com- 
putation. 

The problem of power transmisson may arise in still other forms than 
those just mentioned. Those are, however, the commonest types, and are 
instanced to show how completely the point of view has to change when 
designing plants under various circumstances. The controlling element 
may be minimum first cost, maximum efficiency, minimum cost of trans- 
mission, or combinations of any one of these, with locally fixed require- 
ments as to one or more of the others, or as to special conditions quite apart 
from any of them. 

In very many cases it is absolutely necessary to keep down the initial 
cost, even at a considerable sacrifice in other respects. Or economy in a 
certain direction must be sought, even at a considerable expense in some 
other direction. For these reasons no rigid system can be followed, and 
there is constant necessity for individual skill and judgment. It is no 
uncommon thing to find two plants for transmitting equal powers over 
the same distance under very similar conditions, which must, however, be 
installed on totally different plans in order to best meet the requirements." 



264 CONDUCTORS. 

CALCULATION OF TRANSMISSION LINUS. 

Harold Pender, Ph.D. 
Let 

E = pressure between adjacent wires at receiving end in volts. 

W = power delivered in kilowatts. 

£ = power factor of the load expressed as a decimal fraction. 

A = cross section of each wire in millions of circular mils. 

w = total weight of conductors in pounds. 

I = length of circuit (length of each wire) in feet. 

R = resistance of each wire in ohms. 

U = reactance factor of line = ratio of line reactance to line resistance 

(Table II). 
Q = per cent power loss in terms of delivered power. 
p = per cent pressure drop in terms of delivered pressure. 

Put 

F = M- 

* (kE) 2 

In Table I are given formulae for calculating the cross section, weight, 
and power loss for any kind of conductor. The per cent pressure drop, P, 
can be readily calculated when the per cent power loss is known by means 
of the formula 

P = MQ + NQ 2 . 

Where M and N are constants depending on the pov/or factor (/;) and the 
ratio t\ of the line reactance to the line resistance, tine ratio is called the 
"reactance-factor"; Tables III and IV cive the values of the constants II 
and N for various values of k and t x . To a close approximation, except 
when the power factor is nearly unity, or the receiver current is leading, the 
term NQ 2 may be neglected, i.e., in most practical cases P = MQ. The 
complete expression P = MQ + NQ 2 is exact in all cases for a 10 per cent 
power loss; it is in error less than 3 per cent for any value of P less than 30; 
in any case likely to arise in practice the discrepancy is less than 1 per cent 
in the value of P. The exact expression for P in terms of is 

P = Vi()4 4- 200 (1 4- th) k 2 Q + (1 + h 2 ) k 2 Q 2 - 100 
where t is the tangent corresponding to the cosine k. (See p. 276.) 



Effect of Line Capacity. 

The effect of the capacity of the line is to reduce the pressure drop, i.e., 
improve the regulation, and to decrease or increase the power loss depend- 
ing on the load and power factor of the receiver. Let 

b = 2 nfC X 10 -6 . 

Where C is the capacity of the condenser in microfarads formed by any pair 
of wires of the line, / is the frequency; b is called the capacity susceptance 
of the line (for a single-phase line, the charging current is bE; for a three- 
phase line the charging current per wire is 1.155 bE. 

Table V gives the values of the capacity susceptance per 1000 feet of 
circuit for various sizes of wire spaced various distances apart for a frequency 
of 100 cycles per second; the values for other frequencies are directly pro- 
portional. (Continued on p. 270.) 



CALCULATION OF TRANSMISSION LINES. 



265 




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a 
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O 


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OOO 


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OOO 


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rf cor- 

OOO 


OOt^cO 
Oi(NO 


b-OOCO 

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si is 



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800 OOO COOOCO COCOCO Nhm 

OO OOO i-HCOCO ooo© o^co 

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CALCULATION OE TRANSMISSION LINES. 



2G; 



Table MI. — Values of ?*K. 









Power Factors of Receiver. 








Reactance 
Factors. 


Current Leading. 


Current Lagging. 


h- 


90 


95 


98 


100 


98 


95 


90 


85 


80 


70 


0.0 
0.1 
0.2 


.81 
.77 
.73 


.90 

.87 
.84 


.96 
.94 
.92 


1.00 

1.00 
1.00 


.95 

.98 

1.00 


.90 
.93 
.96 


.81 
.85 
.89 


.72 
.76 
.81 


.64 
.69 
.74 


.49 
.54 
.59 


0.3 
0.4 
0.5 


.69 
.65 
.61 


.81 
.78 
.75 


.90 

.88 
.86 


1.00 
1.00 
1.00 


1.02 
1.04 
1.06 


.99 
1.02 
1.05 


.93 

.97 

1.01 


.86 
.90 
.94 


.79 
.83 
.88 


.64 
.69 
.74 


0.6 
0.7 
0.8 


.58 
.54 
.50 


.72 
.69 
.66 


.84 
.82 
.80 


1.00 
1.00 
1.00 


1.08 
1.10 
1.12 


1.08 
1.11 
1.14 


1.05 
1.09 
1.13 


.99 
1.03 
1.08 


.93 

.98 

1.02 


.79 

.84 
.89 


0.9 
1.0 
1.1 


.46 
.42 
.38 


.63 
.61 

.58 


.78 
.77 
.75 


1.00 
1.00 
1.00 


1.14 
1.16 
1.18 


1.17 
1.20 
1.23 


1.17 
1.20 
1.24 


1.13 
1.17 
1.21 


1.07 
1.12 
1.17 


.94 

.99 

1.04 


1.2 
1.3 
1.4 


.34 
.30 
.26 


.55 
.52 
.49 


.73 
.71 
.69 


1.00 
1.00 
1.00 


1.19 
1.21 
1.23 


1.26 
1.29 
1.32 


1.28 
1.32 
1.36 


1.26 

1.31 
1.35 


1.22 

1.27 
1.31 


1.09 
1.14 
1.19 


1.5 
1.6 
1.7 


.22 

.18 
.14 


.46 
.43 
.40 


.67 
.65 
.63 


1.00 
1.00 
1.00 


1.25 
1.27 
1.29 


1.35 
1.38 
1.41 


1.40 
1.44 
1.48 


1.39 
1.44 
1.48 


1.36 
1.41 
1.46 


1.24 
1.29 
1.34 


1.8 
1.9 
2.0 


.10 
.07 
.03 


.37 
.34 
.31 


.61 
.59 
.57 


1.00 
1.00 
1.00 


1.31 
1.33 
1.35 


1.44 
1.47 
1.50 


1.51 
1.55 
1.59 


1.53 

1.58 
1.62 


1.50 
1.55 
1.60 


1.39 
1.44 
1.49 


2.1 
2.2 
2.3 


-.01 
-.05 
-.09 


.28 
.25 
.22 


.55 
.53 
.51 


1.00 
1.00 
1.00 


1.37 
1.39 
1.41 


1.53 
1.56 
1.59 


1.63 
1.67 
1.71 


1.66 
1.70 
1.75 


1.65 
1.70 
1.75 


1.54 
1.59 
1.64 


2.4 
2.5 
2.6 


-.13 
-.17 
-.21 


.19 
.16 
.13 


.49 
.47 
.45 


1.00 
1.00 
1.00 


1.43 
1.45 
1.47 


1.62 
1.64 
1.67 


1.75 
1.79 
1.83 


1.80 
1.84 

1.88 


1.79 

1.84 
1.89 


1.69 
1.74 
1.79 


2.7 

2.8 
2.9 


-.25 
-.29 
-.33 


.30 
.07 
.04 


.43 
.41 
.39 


1.00 
1.00 
1.00 


1.49 
1.51 
1.53 


1.70 
1.73 
1.76 


1.87 
1.91 
1.96 


1.93 
1.98 
2.02 


1.94 
1.98 
2.03 


1.84 
1.89 
1.94 


3.0 
3.1 
3.2 


-.36 
-.40 
-.44 


-.01 
-.02 
-.05 


.37 
.36 
.34 


1.00 
1.00 
1.00 


1.55 
1.57 
1.58 


1.79 
1.82 
1.85 


1.99 
2.03 
2.04 


2.06 
2.11 
2.15 


2.08 
2.13 
2.18 


1.99 
2.0^ 
2.09 


3.3 
3.4 
3.5 


-.48 
-.52 
-.56 


-.08 
-.11 
-.14 


.32 
.30 
.28 


1.00 
1.00 
1.00 


1.60 
1.62 
1.64 


1.88 
1.91 
1.94 


2.10 
2.14 
2.18 


2.20 
2.24 
2.29 


2.23 
2.27 
2.32 


2.14 
2.19 
2.24 



268 



CONDUCTORS. 



Table IV. — Values of UT. 





Power Factors of Receiver. 


Reactance 
Factors. 


Current Leading. 


Current Lagging. 


t x . 


90 


95 


98 


100 


98 


95 


90 


85 


80 


70 


0.0 
0.1 
0.2 


.001 
.001 
.002 


.001 

.001 
.001 


.000 
.000 
.001 


.000 
.000 
.000 


.000 
.000 
.000 


.001 
.000 
.000 


.001 
.000 
.000 


.001 
.001 
.001 


.001 
001 
.001 


.002 
.001 
.001 


0.3 
0.4 
0.5 


.002 
.003 
.003 


.002 
.002 
.003 


.001 
.002 
.002 


.000 
.001 
.001 


.000 
.000 
.000 


.000 
.000 
.000 


.000 
.000 
.000 


.000 
.000 
.000 


.000 
.000 
.000 


.001 
.000 
.000 


0.6 
0.7 
0.8 


.003 
.004 
.005 


.003 
.004 
.005 


.003 
.004 
.005 


.002 
.002 
.003 


.000 
.001 
.001 


.000 
.000 
.001 


.000 
.000 
.000 


.000 
.000 
.000 


.000 
.000 
.000 


.000 
.000 
.000 


0.9 
1.0 
1.1 


.006 
.007 
.008 


.006 
.006 
.007 


.006 
.006 
.007 


.004 
.005 
.006 


.002 
.002 
.003 


.001 
.002 
.002 


.001 
.001 
.001 


.000 
.001 
.001 


.000 
.000 
.000 


.000 
.000 
.000 


1.2 
1.3 
1.4 


.009 
.010 
.011 


.008 
.010 
.011 


.008 
.009 
.011 


.007 

.008 
.009 


.004 
.005 
.006 


.003 
.003 
.004 


.002 
.002 
.003 


.001 
.001 
.001 


.000 
.000 
.001 


.000 
.000 
.000 


1.5 
1.6 
1.7 


.013 

.014 
.016 


.013 

.014 
.016 


.012 
.014 
.015 


.010 
.011 
.013 


.007 
.008 
.009 


.005 
.006 
.007 


.003 
.004 
.004 


.002 
.002 
.003 


.001 
.001 
.002 


.000 
.000 
.000 


1.8 
1.9 
2.0 


.017 
.018 
.020 


.018 
.019 
.021 


.017 
.019 
.021 


.015 

.016 
.018 


.011 
.012 
.013 


.008 
.009 
.010 


.005 
.006 
.006 


.003 
.003 
.004 


.002 
.002 
.003 


.000 
.000 
.001 


2.1 
2.2 
2.3 


.022 
.023 
.025 


.023 
.025 
.027 


.023 
.025 
.027 


.020 
.022 
.024 


.015 
.016 
.017 


.011 
.012 
.014 


.007 
.008 
.009 


.005 
.006 
.006 


.003 
.003 
.004 


.001 
.001 
.002 


2.4 
2.5 
2.6 


.027 

.029 
.032 


.029 
.031 
.034 


.030 
.032 
.034 


.026 
.028 
.030 


.019 
.021 
.023 


.015 
.017 
.018 


.010 
.011 
.012 


.007 

.008 
.009 


.005 
.005 
.006 


.002 
.002 
.003 


2.7 
2.8 
2.9 


.034 
.036 
.038 


.036 
.039 
.041 


.037 
.040 
.042 


.033 
.035 
.037 


.024 
.026 
.028 


.020 
.021 
.023 


.013 
.015 
.016 


.010 
.010 
.011 


.006 
.007 
.008 


.003 
.003 
.004 


3.0 
3.1 
3.2 


.040 
.042 
.045 


.044 
.046 
.049 


.045 
.047 
.050 


.040 
.042 
.045 


.030 
.033 
.035 


.024 
.026 
.028 


.018 
.019 
.020 


.012 
.013 
.014 


.009 
.009 
.010 


.004 
.004 
.005 


3.3 
3.4 
3.5 


.048 
.051 
.053 


.052 
.055 
.059 


.053 
.056 
.060 


.048 
.051 
.054 


.038 
.040 
.043 


.030 
.032 
.034 


.021 
.023 
.024 


.015 
.017 
.018 


.011 
.012 
.013 


.005 
.006 
.006 



CALCULATION OF TRANSMISSION LINES. 



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270 



CONDUCTORS. 



Using the same notation as given on page 264, putting R for the total 
resistance and X ( = t x R) for the total reactance of each leg of the line, 





Single Phase. 


Three Phase. 


Decrease in per) 
cent pressure > p — 
drop ) 

Decrease in per) ^ = 
cent power loss ) 


50 bX 
at ~2WQ 


100 6* 



where a = 100 bR and t is the tangent corresponding to the cosine k. (See 
p. 276.) The true regulation of the line is then P — p, and the true per 
cent power loss is Q — q, P and Q being calculated by the formulae given 
on pages 264 and 265. These formulae are approximate, being deduced on 
the assumption that the line capacity can be represented by a condenser of 
half the capacity of the line shunted across the line at each end, but they 
are sufficiently accurate for any case likely to arise in practice. It is to be 
noted that the change in regulation is independent of the load and the 
power factor, and is independent of the line resistance; the change in the 
per cent power loss varies with both the load and the power factor. 

Direct Current, Three-Wire System. — Figure the weight and 
cross section of the outer conductors as if the middle or neutral wire was 
not present, putting E = volts between outside wires. The neutral wire 
is usually taken from one- third to full size of each outer conductor. The 
total weight of copper required will therefore be one-sixth to one-half 
greater than the weight determined by the above formula. 

Two-Phase, Tour- IFire System. — Treat each phase separately, 
remembering that half the power is delivered by each phase, and E =■ 
volts between diametrically opposite wires. 

Two-Phase, Three-Wire System. — 



Let 
E 
V 



= pressure between each outer and middle wire at receiving end in volts. 
= pressure between each outer and middle wire at generating end in 
volts. 
Other symbols as above. 

Then for equal rise of temperature in the three conductors the following 
formulae hold. (The total weight of conductor required for this condition 
is only a fraction of one per cent greater than for the condition of maximum 
economy.) 



Cross section of each ) 

outer wire in million \ A x = 
CM. ) 

Cross section of middle ) a __ 
wire in million CM. \ A0 

Total weight in pounds w = 
Total weight in pounds w = 



Copper. 

100 % conduc- 
tivity. 

20° Centigrade 
or 68° F. 



0.93F 

Q 

1.26^! 

9.85/^! 
9.15ZF 



Aluminum. 
62 % conduc- 
tivity. 
20° Centigrade 
or 68° F. 



1.50F 

Q 

1.26^! 

2.97L4, 
4A51F 



Any Material, 
p = microhms 

per cu. in. 
5 = lbs. per 

cu. in. 



1.37pF 

Q 

1.26^! 

30. 7 81 A t 
42.1pSlF 



On the B. & S. gauge the middle wire is larger than each outer by one 
number (see p. 145). 



NUMERICAL EXAMPLES OF CALCULATIONS. 271 



Two or more Circuit* in iSeries. 

The above formulae and tables are also applicable to the case of two or 
more circuits in series, i.e., a transmission line and transformer, if we put 

R = Ri + R2 4- . . . . 

rp = Rlt\ + ^2*3 , 

R I----- 

where R\, R 2 , etc., are the resistances of the separate circuits and t\, £2. etc. : 
are the reactance factors of the separate circuits. 



NUMERICAL EXAIftEPJLKS OF CAICITATIO^, OJP 
WEIGHT, CROSS IECTIOKT, ETC. 

Direct Current, Two-Wire System. 

Copper Wirhs. 

Given W = 40 kilowatts. 

E = 200 volts. 
I = 500 feet. 
Q = 5 per cent. 

„n. rr 500 X 40 

Then F~ -7200)^ = ' 5 - 

2 08 X 5 

Cross section A = — — = 0.208 million CM. 

o 

The nearest commercial size is No. 0000 B. & S. (see Table II) which hat 
an area of 0.212 million CM. 
Total weight of copper w = 6.06 X 500 X 0.212 = 641 pounds. 

r> 1 r> 208 X0.5 

Power loss Q = — — =4.92 per cent. 

Pressure drop P = Q = 4.92 per cent. 

Pressure at generating end = 1 . 0492 X 200 = 209 . 84 volts. 

IMrect Current, Three- Wire System. 

Take the same constants as in the preceding case, considering E = 200 
volts as the pressure between outer wires. If the neutral wire is to be half 
the size of each outer, the total weight of copper required will be 

641 + ?|i = 801 pounds. 

When the system is balanced there will be no current in the neutral wire 
and the regulation and efficiency will be the same as above. If one side 
of the system is fully loaded, and the other side not loaded at all, the volts 
drop in the loaded outer will be the same as if the system was balanced, 
since the same current flows, and the volts drop in the neutral will be twice 
the drop in the outer (same current and double resistance); hence total drop 
will be 14.8 volts in 100 volts or 14.8 per cent. The power loss will also be 
14.8 per cent or 2.96 kilowatts. 



272 CONDUCTORS. 

Alternating* Current, Single Phase. 

Copper Wires Spaced 3 Feet Apabt. 

Given f = 25 cycles per second. 

W — 500 kilowatts. 
E = 10,000 volts. 
I = 45,000 feet. 

k = 0.9, i.e., 90 per cent power factor. 
Q = 10 per cent. 
™-„ *» - 45,000 X 500 _ Q 

Then F ~ (0.9 X lO.OOO)* = °- 278 * 

2.08X0.278 n A __ .... _„ 

Cross section ^4 = r^r = . 0578 million CM. 

The nearest commercial size is No. 2 B. & S. (Table II), which has an area 
of 0.0664 million CM. 
Total weight of copper w = 6.06 X 45,000 X 0.0664 = 18,100 lbs. 

tt i ^ 2.08 X 0.278 

Exact power loss Q = — ~ ~ aaA — =8.71 per cent. 

U . Uoo4 

1 44 
Reactance factor t x = -~— = 0.36. (Table II). 

Therefore M = 0.95 (Table III). 

N = 0.000. (Table IV). 

Then, neglecting the capacity of the line, 
Pressure drop P = 0.95 X 8. 71 = 8.27 per cent. 

Pressure at generating end = 1.0827 X 10,000 = 10,827 volts. 

Two-Phase, Three-Wire System. 

Copper V/ires Spaced 3 Feet Apart. 
Given / = 25 cycles per second. 

W = 500 kilowatts. 
E = 10,000 volts. 
I = 45,000 feet, 

k =0.9, i.e., 90 per cent power factor. 
Q = 10 per cent. 
Then 

F 45,000 X 500 

(0.9X10,000) 2 u -^'°- 

93 X 278 
Cross section of outers A t = — -^ = 0.0259 million CM. 

The nearest commercial size is No. 6 B. & S. (Table II) which has an area 

of 0.0263 million CM. The middle wire must therefore be No. 5 B. & S. 

Total weight of copper w = 9.85 X 45,000 X 0.0263 = 11,600 lbs. 

tt * i n °- 93 X0.278 _ _ 

Exact power loss Q = — n = 9.87 per cent. 

The pressure loss will depend upon how the wires are arranged on the 
poles. As a first approximation for any ordinary arrangement, the reac- 
tance of each phase can be considered the same as in a single phase system 
with wires of the same cross section as the outer, spaced a distance apart 
equal to that between each outer and the middle wire. 

From Table II the reactance factor of a No. 6 wire corresponding to a 
three-foot spacing and 25 cycles is 

d- ^1=0.15. 

4 

Whence M = 0.87. 



NUMERAL EXAMPLES OF CALCULATIONS. 273 

Then neglecting the capacity of the line, and using the approximate 
formula P = MQ, 

Pressure drop P = 9.87 X 0.87 = 8.59 per cent. 

Pressure at generating end = 1.0859 X 10,000 = 10,859 volts. 

Alternating: Current, Three-Phase. 

Copper Wires Spaced 6 Feet Apart. 

Given / =60 cycles per second. 

W = 10,000 kilowatts. 
E = 60,000 volts. 
I = 400,000 feet. 

k = 0.85, i.e., 85 per cent power factor. 
Q = 12 per cent. 

„ 400,000 X 10,000 , . . 
rhen F = (0.85X60,000)' = 1M - 

Cross section A = — — — : — = 0. 133 million CM. 

The nearest commercial size is No. 00 (see Table II), which has an area 
of 0.133 million CM. 

Total weight of copper w = 9 .09 X 400,000 X 0. 133 = 484,000 lb. 
Neglecting line capacity, 

T7 * i n 1-54 X 1.04 10 , 

Exact power loss Q = — _ „ = 12 per cent. 

Reactance factor t t = 3 . 06 X . 6 = 1 . 84. 

Therefore M = 1 . 55. 

N = 0.003. 
Pressure drop P = 1.55 X 12 + [0.003 X (12) 2 ] = 19.0. 

Effect of line capacity (see p. 264). 

b = .00000089 X 0.6 X 400 = 0.000214. 

(Table V). 
R =0.0778X400 = 31.1 (Table II). 
X = 1.84 X 31.1 = 57.2. 
Then 

Decrease in per cent pressure drop = p = 100 X 0.000214 X 57.2 = 1.2. 

a =100X0.000214X31.1=0.67. 
t = 0.62. 

Decrease in per cent power loss = q =2x0. 67X0. 62- ( Q ' N9 ' =0.8. 

(U. oo)^ Xl^ 

Whence 

True pressure drop = 19.0 — 1.2 = 17.8 per cent. 

True power loss = 12.0 — 0.8 = 11.2 per cent. 

Pressure at generating end = 1 . 178 X 60,000 = 70,680 volts. 



274 



CONDUCTORS. 



tranSiIKissioh mi: ojf known constants. 

The following formulae and tables give an exact method of calculating 
the efficiency and regulation of a transmission line of known constants, 
in terms of the pressure between adjacent wires at the generating end of 
line. 



Given: 



The kind of system, direct or alternating, 



n = number of phases, for the " single phase " system n — 2. 
f = frequency in cycles per second. 

V — pressure between adjacent wires at generating end, in volts. 
W = power delivered in watts. • 

cos a. = power factor of load at receiving end. 
R — resistance of each wire in ohms. 
X = inductive reactance of each wire in ohms. 
Z = \/R 2 + X 2 = impedance of each wire. 
Required: E = pressure between adjacent wires at receiving end in volts. 
/ = current per wire in amperes. 
H = total power lost in watts. 
The values of E, I, and H are given in the table on p. 275. For approx- 
imate calculations J can be taken equal to unity; the exact value of J is 
given in the table below. 



Values of .1. 



.00 
.01 
.02 
.03 
.04 
.05 



000 



1.0000 
1.0001 
1.0004 
1.0009 
1.0016 
1.0025 



.001 



1.0000 
1.0001 
1.0004 
1.0010 
1.0017 
1.0026 



.002 



1.0000 
1.0001 
1.0005 
1.0010 
1.0017 
1.0027 



.003 



1.0000 
1.0002 
1.0005 
1.0011 
1.0018 
1.0028 



.004 



1.0000 
1.0002 
1.0006 
1.0012 
1.0019 
1.0029 



.005 



1.0000 
1.0002 
1.0006 
1.0012 
1.0020 
1.0030 



.006 



1.0000 
1.0003 
1.0007 
1.0013 
1.0021 
1.0031 



.007 



1.0000 
1.0003 
1.0007 
1.0014 
1.0022 
1.0032 



.008 



1.0001 
1.0003 
1.0008 
1.0014 
1.0023 
1.0034 



.009 



1.0001 
1.0004 
1.0008 
1.0015 
1.0024 
1.0035 



e 


.000 


.002 


.004 


.006 


.008 


e 


.000 


.002 


.004 


.006 


.008 


.06 


1.004 


1.004 


1.004 


1.004 


1.005 


.29 


1.102 


1.104 


1.106 


1.108 


1.110 


.07 


1.005 


1.005 


1.005 


1.006 


1.006 


.30 


1.111 


1.113 


1.115 


1.117 


1.119 


.08 


1.006 


1.007 


1.007 


1.007 


1.008 


.31 


1.121 


1.123 


1.125 


1.127 


1.129 


.09 


1.008 


1.008 


1.009 


1.009 


1.010 


.32 


1.131 


1.133 


1.135 


1.137 


1.139 


.10 


1.010 


1.010 


1.011 


1.011 


1.011 


.33 


1 . 141 


1.143 


1.146 


1.149 


1.151 


.11 


1.012 


1.012 


1.013 


1.013 


1.014 


.34 


1.154 


1.156 


1.158 


1.161 


1.163 


.12 


1.014 


1.015 


1.015 


1.016 


1.017 


.35 


1.167 


1.169 


1.171 


1.174 


1.177 


.13 


1.018 


1.018 


1.019 


1.019 


1.020 


.36 


1.180 


1.183 


1.186 


1.189 


1.192 


.14 


1.021 


1.021 


1.022 


1.022 


1.023 


.37 


1.195 


1.199 


1.202 


1.206 


1.209 


.15 


1.024 


1.024 


1.025 


1.025 


1.026 


.38 


1.213 


1.216 


1.220 


1.224 


1.227 


.16 


1.027 


1.027 


1.028 


1.029 


1.030 


.39 


1.231 


1.234 


1.238 


1.242 


1.246 


.17 


1.031 


1.032 


1.032 


1.033 


1.034 


.40 


1 . 250 


1.254 


1.258 


1.263 


1.267 


.18 


1.034 


1.035 


1.03G 


1.037 


1.038 


.41 


1.272 


1.276 


1.280 


1.285 


1.290 


.19 


1.039 


1.040 


1.041 


1.042 


1.043 


.42 


1.296 


1.301 


1.307 


1.312 


1.318 


.20 


1.044 


1.045 


1.046 


1.046 


1.047 


.43 


1.324 


1.330 


1.336 


1.342 


1.349 


.21 


1.048 


1.049 


1.050 


1.051 


1.052 


.44 


1.356 


1.363 


1.370 


1.377 


1.385 


.22 


1.053 


1.054 


1.05G 


1.057 


1.058 


.45 


1.393 


1.401 


1.410 


1.409 


1.428 


.23 


1.059 


1.0G1 


1.062 


1.063 


1.065 


.46 


1.437 


1.447 


1.457 


1.468 


1.479 


.24 


1.066 


1.067 


1.068 


1.070 


1.071 


.47 


1.491 


1.504 


1.518 


1.532 


1.547 


.25 


1.072 


1.074 


1.075 


1.076 


1.078 


.48 


1.563 


1.580 


1.599 


1.620 


1.643 


.26 


1.079 


1.081 


1.082 


1.083 


1.084 


.49 


1.668 


1.697 


1.733 


1.778 


1.835 


.27 


1.086 


1.087 


1.089 


1.090 


1.092 


.50 


2.000 










.28 


1.094 


1.096 


1.098 


1.099 


1.100 















TRANSMISSION LINE OF KNOWN CONSTANTS. 



275 





I 





Q 
Z 



I 

























^_^ 


>TN 


>"V >^s 


b 1 8 








ti 




<3 




a 


B 


j3 


a 


tq 


>^k 


CO 

w 


fc 


93 

c 


fe 


aj . co 

8k 3 


"3 


CO 

O 




fefa 


K5 




3! 




K3 


Bq 


&3 




V—-' v^^.^ 


"*»•— "^ 


^»—^' s — — '"' 






« &3 


A3 


ft^ ft^J(N 






CM CM 






0$| 8 












$ 








ti * 


fe 


CO 

8 


•*H 


fe|K|fc 


C5 
B 
C 
Q 


fc 


DO 
C 


=r 


CO 

O 


co 


o 

Ol 

> 


K3 

X 

b 1 8 






^ 






ICO 

> 


g 


8 










CM 




fcq 


|05l^|Qq|S|cq|^!Qq|S|QqiS 


lOQI^s 


^^^* 


""^J ->- 


^> 










tsi 


« 




X 









U 


S3 




a 

DQ 






a 

CO 

O 
© 




<m 1 w cq 




05 




05 


oq 


'5a 


&3 

8 










<* 










^ 




^ 


IT 


^ ^ 


03 




a 


a 


a a 






+3 


03 




N 




^ + 


£ 


+ 




+ 


+ * 


5 


oq 


"* a* 


s 


A) + 


fe 




I * 


fe 


b 1 8 




1 


CM 

1 


CM & 
1 1 


ooi 8 




K. 


& 


& & 


. 1 










& 












'3 


£ M 


* 

CO 


CO 03 


00 




a> a) 


(D 


0) 0) 


CD 


o 


1 1 




- t- 


1 


*o 


CM <M 


^ 


CO TJH 


8 




0> 
m 


CD 


CO CO 


O 

CO 
03 


H 


9 Ph 


rP 


-3 J§ 


J5 




ftn 


ftH Ph 


PL. 




Q rH 




CM 




CO 


"* 




8 





P. 


50 







>> 


a> 

D1 




a 


a; 


OQ 


5 


a 


-i 


X 







-r 


u 


d 

9) 


*s 


Cv 




^ 


d 






u 


0) 


XJ 


i— 


^' 


,s 


§ 


a 


W 


B3 

+3 


a> 


. 







rr, 




•"" 


a 


[> 


h 







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^ 



276 



CONDUCTORS. 



0.000 



100 
50.0 

33.3 
25.0 
20.0 

16.6 
14.3 
12.5 

11.1 
9.95 
9.03 

8.27 
7.63 
7.07 

6.59 
6.17 
5.80 

5.47 
5.17 
4.90 

4.66 
4.43 
4.23 

4.05 
3.87 
3.71 

3.57 
3.43 
3.30 

3.18 
3.07 
2.96 

33 2 86 
0.34 2.77 
0.35 2 



2.59 
2.51 
2.43 

2.36 
2.29 
2.22 

2.16 
2.10 
2.04 

1.98 
1.93 
1.88 

1.83 

1.78 



0.002 



500 
83.3 
45.4 

31.2 

23.8 
19.2 

16.1 
13.8 
12.2 

10.8 
9.75 
8.87 

8.14 
7.51 
6.97 

6.50 
6.09 
5.73 

5 40 
5.11 

4.85 

4.61 
4.39 
4.19 

4.01 
3.84 
3 

3.54 
3.40 
3.28 

3 16 
3.05 
2.04 

2.84 
2.75 
2 

2.58 
2.50 
2.42 

2 35 

2.28 
2.21 

2.15 
2.09 
2 03 



1 
1 
1.87 



1.82 
1 77 



0.004 



250 
71.4 
41.6 

29 4 
22.7 
18.5 

15.6 
13.5 
11.9 

10.6 
9.56 
8.71 

8.00 
7.40 
6.87 

6.42 
6.02 
5.66 

5.34 
5.06 
4.80 

4.56 
4.35 
4.15 

3.97 
3.81 
3.65 

3.51 
3.38 
3.25 

3.13 
3.02 
2.92 

2.82 
2.73 
2.64 

2 56 

2.48 
2.40 

2.33 
2.26 
2.20 

2.14 
2.08 
2.02 

1.96 
1.91 

1.86 

1.81 
1 76 



0.006 



167 
62 5 
38 4 

27 7 
21 7 
17.8 

15 1 
13.1 
11.6 

10.4 

9 38 
8.56 

7.87 
7 28 
6.78 

6.33 
5.94 
5.59 

5.28 
5 00 
4 75 

4 52 
4 31 
4.12 

3.94 

3.78 
3.62 

3.48 
3.35 
3.23 

3.11 
3.00 
2.90 

2 

2 71 
2.63 

2.54 
2 46 
2 39 

2 32 

2.25 
2.19 

2.12 
2.06 
2.01 

1.9! 
1.90 
1.85 

1. 
1 75 



0.008 



125 
55 5 
35 7 

26 3 
20 8 
17 2 

14 7 
12 8 
11 3 

10 2 
9 21 
8.41 

7 75 
7 18 
6 68 

6 25 

5 

5.53 

5.22 
4 95 
4 70 

4 
4 
4. 

3 91 
3 75 
3.59 

3 46 
3 33 
3.20 

3.09 

2 

2.88 

2 78 
2 
2 61 

2.53 
2.45 
2.38 

2.30 
2.24 
2.17 

2.11 
2.05 
2.00 

1.94 

1. 

1.84 



K 



50 
51 
0.52 

0.53 
0.54 
0.55 

0.56 
0.57 
0.58 

0.59 
0.60 
0.61 

0.62 
0.63 
0.64 

0.65 
0.66 
0.67 

0.68 
0.69 
0.70 

0.71 
0.72 
0.73 

0.74 
0.75 
0.76 

0.77 

0.78 
0.79 

0.80 
0.81 
0.82 

0.83 
0.84 
0.85 

0.86 
0.87 
0.88 

0.89 
90 
0.91 

0.92 
93 
0.94 

0.95 
96 
97 



1.732 

1.687 
1.643 

1.600 

559 

1.519 

479 
1.442 
1.404 

.368 

.333 

1.299 

265 
1.233 
1.201 

1.169 

138 

1.108 



0.000 



1.078 
1.049 
1.020 



0.992 
0,964 
0.936 

0.909 

0.882 
0.855 

0.829 
0.802 
0.776 

0.750 
0.724 
0.698 

0.672 
646 
0.620 

0.593 
0.567 
0.540 

0.512 
0.489 
0.456 

426 
0.395 
0.363 

0.329 
0.292 
0.251 



0.002 



1.723 
1 678 
1.634 

1 592 

550 

1.511 

1.471 
1 434 
1.397 

1.361 
1 . 326 
1 . 292 

1.259 
1.226 
1.194 

1.163 
1.132 
1.102 

1.072 
1.043 
1.015 

0.986 
958 
0.931 

0.904 

0.877 
0.850 

0.823 
0.797 
0.771 

0.745 
0.719 
0.693 

0.667 
0.641 
0.614 

0.588 
0.5G1 
0.534 

507 
0.479 
0.450 

0.420 
0.389 
0.356 

0.321 
0.284 
0.242 



1 714 

1.669 
1.626 



1.79 98 0.203 0.192 181 169 156 
1.74 99 0.143 0.127 0.110 0.090 0.063 



0.004 



583 
542 
503 

464 
427 
390 

354 
319 

"286 



1 252 
1 220 
1.188 

1.157 
1.126 
1.096 

1 067 
1.037 
1.009 

981 
0.953 
0.925 

0.898 
0.871 
0.845 

0.818 
0.792 
0.766 



0.662 
0.635 
0.609 

0.583 
0.556 
0.529 

0.501 
473 
0.444 

0.414 
0.383 
0.350 

0.314 
0.276 
0.232 



0.006 

1.705 
1.660 
1.617 

1.575 
1.534 
1 495 

1.457 
1 419 
1.383 

1.347 
1 313 
1.279 

1.246 
1.213 
1.181 

1.151 
1.120 
1.090 

1 061 
1 032 
1.003 

0.975 
947 
0.920 

0.893 
0.866 
0.839 

0.813 

0.787 
0.760 

0.734 

0.708 
0.682 

0.656 
0. 630 
0.604 

0.577 
0.551 
0.523 

0.496 
0.467 
0.438 

408 
0.376 
0.343 

0.307 
0. 268 
0.223 



Note: This table is to be used like a table of logarithms, e. g. % the reac- 
tance factor corresponding to the power-factor k = 0.816 is 2 = 708. 



TRANSMISSION LINE CALCULATIONS. 277 



PARALLEL DISTRIBUTION. 

When the translating devices, whether lamps or motors, are scattered 
over a considerable area, the ucuai method of supplying them with power 
is to run a single feeder to some point near the "center of gravity" of 
the load, and from this center run out branches to feed groups of lamps or 
motors in parallel. The center of gravity of the load can be readily deter- 
mined as follows: 

Let itfi, v)2, 103, etc. 

represent the individual loads, 

and x it X2, £3. etc 

and y u 2/2, 2/3. etc., 

represent the distances of these loads from any two fixed lines OX and OY 
at right angles to each other. Then the center of gravity is that point which 
is the distance 

= XlWl+X2W2 + X3W , + ... from0X 
w x + w 2 + w z + 



and 



y = 2/^+2/2^2+2/3^3 + ... from 0Y 
Wl + W2 + W 3 + . . . 



The center of gravity of the load is by no means always the most economi- 
cal location for the center of distribution, as considerations of the relative 
cost of establishing the center at this point in comparison with the cost at 
other points, the probable change in the distribution of the load with the 
growth of the system, etc., have all to be taken into account. 

The general scheme of feeders, centers of distribution, and branches 
can be developed still further, and sub-centers, sub-feeders, etc., estab- 
lished, until a point is reached where the saving in the cost of copper is 
balanced by the increase in the cost of the centers of distribution. 



Calculation of Cross Section, Weight, &c. 

When a transmission line is loaded at more than one point, the conductor 
should have such dimensions that the pressure drop at the end of the line, 
when the line is supplying the maximum load at each point, shall not exceed 
a given amount. Whether the conductor shall be made of uniform section 
throughout the length of the line, or be reduced in size as the current 
carried diminishes, will depend on the relative amounts of energy sup- 
plied at, and the distances between, the various points at which the line is 
loaded. Below will be found formulae for determining the weight and 
cross section of a line of uniform cross section, and having no reactance, 
supplying a distributed load. When the line has no inductive reactance 
the weight and cross section of the conductor for a given pressure drop 
are to a close approximation independent of the power factor of the loads 
at the various points. When the line has reactance, the formulae will give 
only a first approximation to the correct weight and cross section. The 
error involved can be determined by considering each section of the line 
separately, and calculating the drop in each section, assuming the dimen- 
sions given by the approximate formulae. (See page 264.) If the pressure 
drop at the end of the line thus calculated differs considerably from the 
permissible drop given, choose a larger size wire and make another trial 
calculation, etc., until the proper size is found. 



278 



CONDUCTORS. 



1} 



<— It- 



Fig. 15. 



In the figure let G be the generating end of the line ; J the far end of line 



Given: 
E = 

k, h 

P = 

Required: 
A = 
w = 
Put 



= pressure between adjacent wires at far end of line in volts. 
W 2 , Wz, etc., the loads in kilowatts at the points 1, 2, 3, etc. 
, lz, etc., the distances of these points from the generating end in 

feet. 

per cent pressure drop at far end of line in terms of delivered 

pressure. 

cross section of each wire in million CM. 
total weight of conductors in pounds. 



W = w t + W2 + Wz + . . . total power delivered in kilowatts. 

I = l L + l 2 + lz + . . . total length of circuit (length of each wire) in feet. 



F - 



hW t + hW 2 + hWz + . . . 
E* 



Then, for a line having no reactance : 







Copper. 
100% conduc- 
tivity. 
20° Centigrade. 


Aluminum. 
62% conduc- 
tivity. 
20°Centigrade. 

3.34F 


Any Material. 
p = microhms 

per cu. in. 
5 — lbs. per 

cu. in. 


Single Phase. 

Cross section in million 
C M 


A = 
w = 

w = 

A = 

w = 

w = 


2.0SF 


3.06pF 


Total weight of conduc- 
tors 

Or total weight of con- 
ductors 

Three Phase. 

Cross section in million 
CM 

Total weight of conduc- 
tors 

Or total weight of con- 
ductors 


P 
6.06L4. 

12. 6FI 


P 

1 . 83L4 

6.11FZ 


P 
18.9MA 

57. 881F 


P 
1.04F 


P 
1.67F 


P 
1.53 P F 


P 
9.09L4 

9.48FZ 


P 
2.741A 

4.58*7 


P 

28.3SL4 

43. 2 P 81F 


P 


P 


P 



TRANSMISSION LINE CALCULATIONS. 279 



Economical Tapering* of Conductor. 

When the distances between the points at which the line is loaded are 
considerable, it is usually advantageous to taper the conductor; the most 
economical pressure drop per section must be determined, and each section 
of the line calculated independently. The following formulae give the 
most economical division of the drop, taking into account the cost both 
of conductor and insulation. For short runs the saving in cost of con- 
ductor and insulation may be more than offset by the extra cost of handling 
two or more sizes of wire. 

The same notation as in the preceding paragraph is used. In addition, 
let 

U t = W x -f- W 2 -h Wz + • • • = total load in kilowatts at and beyond point 1 . 
JJ 2 = W 2 + TF3 + . . . = total load in kilowatts at and beyond point 2. 
U3 = W% -+-.•• = total load in kilowatts at and beyond point 3. 

3tC. 

A x = Zj = distance in feet from generating end to point 1. 
*2 =■= h — h = distance in feet between points 1 and 2. 
^3 = h ~ h = distance in feet between points 2 and 3. 
etc. 

Thea the most economical per cent pressure drop for the ith section is 

Pi== XiV uj x P 

*i ^Ut + A 2 ^U 2 + A3 ^U 3 



House Wiring*. 

y* 

As a rule, the size of wire used in wiring ordinary buildings for light 
&nd power as fixed by the permissible heating of the wire (see p. £65) is of 
sufficient size to keep the pressure drop within the prescribed limit, since 
the distances the wires are run are comparatively short. It is always well, 
however, to calculate the drop in the heaviest and longest circuits, to be 
sure that one is on the safe side as regards regulation. 

Chart and Table for calculating* Alternating-Current 

JLi ne.«. 

Ralph D. Mershon, in American Electrician. 

The accompanying table, and chart on page 282 include everything neces- 
sary for calculating the copper of alternating-current lines. 

The terms, resistance volts, resistance E.M.F., reactance volts, and react- 
ance E.M.F., refer to the voltages for overcoming the back E.M.F.'s due to 
resistance and reactance respectively. The following examples illustrate 
the use of the chart and table. 

Problem. — Power to be delivered, 250 k.w.; E.M.F. to be delivered, 2000 
volts; distance of transmission, 10,000 ft.; size of wire, No. ; distance be- 
tween wires, 18 inches ; power factor of load, .8 ; alternations, 7200 per min- 
ute. Find the line loss and drop. 

The power factor is that fraction by which the apparent power or volt-am- 
peres must be multiplied to give the true power or watts. Therefore the 

250 k w 
apparent power to be delivered is ^ — - = 312.5 apparent k.w., or 312,500 

volt-amperes, or apparent watts. The current, therefore, at 2000 volts will be 

312 500 

-xqVvq- = 156.25 amperes. From the table of reactances, under the heading 

M 18 inches," and corresponding to No. wire, is obtained the constant, .228. 
Bearing the instructions of the table in mind, the reactance volts of this 



280 CONDUCTORS. 

line are 156.25 (amperes) X 10 (thousands of feet) x .228 = 356.3 volts, whicli 
are 17.8 per cent of the 2000 volts to be delivered. 

From the column headed " Resistance Volts," and corresponding to No. 
wire, is obtained the constant .197. The resistance volts of the line are, 
therefore, 156.25 (amperes) x 10 (thousands of feet) x .197 = 307.8 volts, which 
are 15.4 per cent of the 2000 volts to be delivered. 

Starting, in accordance with the instructions of the sheet, from the point 
where the vertical line, which at the bottom of the sheet is marked " Load 
Power Factor .8," intersects the inner or smallest circle, lay off horizontally 
and to the right the resistance E.M.F. in per cent (15.4), and "from the 
point thus obtained," lay off vertically the reactance E.M.F. in per cent 
(17.8). The last point falls at about 23 per cent, as given by the circular arcs. 
This, then, is the drop in per cent of the E.M.F. delivered. The drop in per 

23 
cent of the generator E.M.F. is, of course, o = 18.7 per cent. 

J.UU —j" — o 

The resistance volts in this case being 307.8, and the current 156.25 am- 
peres, the energy loss is 307.8 x 156.25 = 48.1 k.w. The percentage loss is 

48.1 
250 4- 4g .. = 16.1. Therefore, for the problem taken, the drop is 18.7 per cent, 

and the energy loss is 16.1 per cent. 

If the problem be to find the size of wire for a given drop, it must be solved 
by trial. Assume a size of wire, and calculate the drop in the manner above 
indicated ; the result in connection with the table will show the direction 
and extent of the change necessary in the size of wire to give the required 
drop. 

The table is made out for 7200 alternations per minute, but will answer 
for any other number. For instance, for 16,000 alternations, multiply the 
reactances by 16000 -f- 7200 = 2.22. 

As an illustration of the method of calculating the drop in a line and trans- 
former, and also of the use of the table and chart in calculating low-voltage 
mains, the following example is given : — 

Problem. —A single-phase, induction motor is to be supplied with 20 am- 
peres at 200 volts ; alternations, 7200 per minute ; power factor, .78. The 
distance from transformer to motor is 150 ft., and the line is No. 5 wire, 6 
inches between centres of conductors. The transformer reduces in the ratio 
2000 : 200, and has a capacity of 25 amperes at 200 volts ; when delivering this 
current and voltage, its resistance E.M.F. is as 2.5 per cent, and its reactance 
E.M.F. 5 per cent, both of these constants being furnished by the makers. 
Find the drop. 

The reactance of 1000 ft. of circuit, consisting of two No. 5 wires, 6 inches 

150 
apart, is .204. The reactance-volts, therefore, are .204 x tt^ X 20= .61 volts. 

150 
The Tesistance-volts are .627 x ^^^ X 20 = 1.88 volts. At 25 amperes, the re- 

j 1000 

sistance-volts of the transformers are 2.5 per cent of 200, or 5 volts. At 20 

20 
amperes they are — of this, or 4 volts. Similarly, the transformer reactance 

volts at 25 amperes are 10, and at 20 amperes are 8 volts. The combined re- 
actance-volts of transformer and line are 8-f- .61 = 8.61, which is 4.3 per cent 
of the 200 volts to be delivered. The combined resistance- volts are 1.88-}- 4, 
or 5.88, which is 2.94 per cent of the E.M.F. to be delivered. Combining these 
quantities on the chart with a power factor of .78, the drop is 6 per cent of 

the delivered E.M.F., or -— = 4.8 per cent of the impressed E.M.F. The 

105 
transformer must therefore be supplied with 2000 -f- .952 = 2100 volts, in order 
that 200 volts shall be delivered to the motor. 

To calculate a four-wire, two-phased transmission circuit, compute, as 
above, the single-phased circuit required to transmit one-half the power at 
the same voltage. The two-phase transmission will require two such 
circuits. 

To calculate a three-phase transmission, compute, as above, a single-phase 
circuit to carry one-half the load at the same voltage. The three-phase 
transmission will require three wires of the size obtained for the single-phase 
circuit, and with the same distance (triangular) between centres. 

By means of the table calculate the Resistance- Volts and the Reactance- 



TRANSMISSION LINE CALCULATIONS. 



281 



Volts in the line, and find what per cent each is of the E.M.F. delivered at 
the end of the line. Starting from the point on the chart where the vertical 
line corresponding with power factor of the load intersects the smallest 
circle, lay off in per cent the resistance E.M.F. horizontally and to the right; 
from the point thus obtained lay off upward in per cent the reactance E.M.F. 
The circle on which the last point falls gives the drop in per cent of the 
E.M.F. delivered at the end of the line. Every tenth circle-arc is marked 
with the per cent drop to which it corresponds. 



Size 

of 

Wire 

B.&S. 


o 

o 
o 

-§£ 

§M 

£h.S 

fcj) 


o a 

§^ 

o • 

io 

ss 

.22 © 


'- 
d 

C" 

r; 

o 

;> 



u 


£ 


Reactance- Volts in 1000 ft. of Line ( = 2000 ft. 
of Wire) for One Ampere ( V Mean Square) at 
7200 Alternations per Minute for the Distance 
given between Centers of Conductors. 






V 


1" 


2" 


3" 


6" 


9" 


12* 


18" 


24" 


30" 


36" 


3000 


639 


.098 


.046 


.079 


.111 


.130 


.161 


.180 


.193 


.212 


.225 


.235 


.244 


000 


507 


.124 


.052 


.085 


.116 


.135 


.167 


.185 


.199 


.217 


.230 


.241 


.249 


00 


402 


.156 


.057 


.090 


.121 


.140 


.172 


.190 


.204 


.222 


.236 


.246 


.254 





319 


.197 


.063 


.095 


.127 


.145 


.177 


.196 


.209 


.228 


.241 


.251 


.259 


1 


253 


.248 


.068 


.101 


.132 


.151 


.183 


.201 


.214 


.233 


.246 


.256 


.265 


2 


201 


.313 


.074 


.106 


.138 


.156 


.188 


.206 


.220 


.238 


.252 


.262 


.270 


3 


159 


.394 


.079 


.112 


.143 


.162 


.193 


.212 


.225 


.244 


.257 


.267 


.275 


4 


126 


.497 


.085 


.117 


.149 


.167 


.199 


.217 


.230 


.249 


.262 


.272 


.281 


5 


100 


.627 


.090 


.121 


.154 


.172 


.204 


.223 


.236 


.254 


.268 


.278 


.286 


6 


79 


.791 


.095 


.127 


.158 


.178 


.209 


.228 


.241 


.260 


.272 


.283 


.291 


7 


63 


.997 


.101 


.132 


.164 


.183 


.214 


.233 


.246 


.265 


.278 


.288 


.296 


8 


50 


1.260 


.106 


.138 


.169 


.188 


.220 


.238 


252 


.270 


.284 


.293 


.302 



282 



CONDUCTORS. 











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rite±E 


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quals one Percent 










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Load Power Factors 



10 20 30 

Drop in Percent of 
E.M.F. Delivered 



Fig. 1(5. 



TRANSMISSION LINE CALCULATIONS. 



283 



The following curves published by the General Electric Company give 
the pounds of copper per kilowatt delivered for various percentages of power 
loss and various pressure gradients (volts per mile). It is to be noted that 
these curves are correct only for unity power factor. 

Line Loss in per cent of Power Delivered. 



rirn v 


fflt PP^t I L A 


wtitt , T i V A 


flrtttm 3 3 x 


fflt+t+^h- f V v 


nitui. t X X a 


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pjnj^t A- a v A 


t ttx t 3 \r v , 


£ ^443 A V > £ 


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ftttJJ I C V v \ 


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002 
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061 
S8I 
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Sit 
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091 
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0ST 

src 

on 

S2T 
SST g 

osi <a 

ST1 & 
0Tl£ 

sot 

001 . 
S6 






06 S 






Fig. 17. 

Explanation : Figures on curves indicate volts per mile, i.e., potential 
of line divided by distance. Weight of copper, potential, and line loss are 
in terms of power delivered at end of line and not of generated power. 
Curves are correct only for 100% power factor. Two-phase, single-phase 
or continuous current transmission requires one-third more copper. 5% 
has been allowed for sag and tie wires in weights of copper given. 

Example: Assuming that 1000 kw. at 10,000 volts are to be delivered 

over a line 10 miles long with 5% loss, we have — - '- — ^ = 1000 volts 

& 10 miles 

per mile. Looking on the 1000 volt curve, we find 5% line loss corresponds 
to 57 lbs. of copper per kilowatt delivered. 



284 CONDUCTORS. 



IIETKRni5AT10\ OE SIZE OE CONDUCTORS FOR 

PARALLEL DIITRIBUTIOX OF DIRECT 

CURRENT. 

Resistance of one cir. -mil-foot of pure hard drawn copper wire 

at 20° C. (68° F.) (see page 200) 10.57 ohms 

Resistance of one cir.-mil-foot of pure hard drawn copper wire 

at 97.5 per cent conductivity 10.8 ohms 



Thus the resistance R of any hard drawn copper conductor is, 

D length in feet X 10.8 

R = ; n * 

cir. mils 

length in feet X 10.8 



and 



Cir. mils = 
Length in feet = 



B 

B X cir. mil9 
10^8 



Let / = Current in amperes flowing in circuit. 

W = Watts, power in circuit. 

E = Volts at receiving end of circuit. 

v = Volts drop in circuit. 

A = Cir. mils area of wire. 

P = Per cent of power lost. 

p = Per cent of volts drop in circuit. 

d = Distance from generating to receiving end of circuit or center 
of load=£ the length of wire if the load is uniformly dis- 
tributed. 
21.6 = 10.8 X 2. 



Then 



21.6 X d X / 





V 


\ 


2160 Xd X I 




PXE 


A 


2160 X d X W 


PXE 2 ' 




21.6 Xd X T 




A 


V 


p XE 



100 



TRANSPOSITION OF LINES. 



285 



TRANSPOSITION OF IIYES. 

F. F. Fowle. 

The transposition of overhead lines is a means for eliminating induction 
between them and is universally employed on telephone lines and quite fre- 
quently on power and lighting circuits. 

Transpositions are effective only under certain conditions. Fig. 18 
shows the electric and the magnetic fields about a line consisting of a single 
wire whose circuit is completed through the earth. Fig. 19 shows the fields 





Fig. 18. 



"\ / MAGNETKJ 

etATio 
Fig. 19. 



about the two wires of a metallic circuit, with equal and opposite currents 
in the wires and no connection to earth at any point on the circuit. In 
telephony this condition of line is termed "balanced." 

The intensity of the induced current depends on the extent to which the 
field of one circuit threads into the other, and therefore upon the distance 
between the wires and the extent to which their fields spread into the sur- 
rounding dielectric. The spread of the field of a single-wire circuit, shown 
in Fig. 1 8, is equal to that of an imaginary metallic circuit of which one 
wire is the existing overhead wire- and the other a similar wire parallel to 



Transposition 



H— 






-i-- 



a-b = b-c 
Fig. 20. 



the existing wire but beneath the earth's surface a distance equal to the 
elevation of the existing wire. The spread of the field of single- wire earth- 
return circuits is therefore excessive. 

Fig. 20 shows the manner of neutralizing mutual inductive effects of 
two metallic circuits by the transposition of the wires of one circuit. By 
the transposition of wires 3 and 4 midway in the section the field of the 
circuit 3-4 from a to b is opposite in its direction and polarity to that be- 
tween b and c, sp that the induced E.M.F.'s in circuit 1-2 between a and 6 
are opposite to those between b and c. The same is true of induced E.M.F.'s 



286 



CONDUCTORS. 



in circuit 3-4 produced by circuit 1-2. The effects would have been iden- 
tical had 1 and 2 been transposed instead of 3 and 4. 

Referring to Fig. 20, the length of the section I must not be so great that 
the current and the potential in the section a-b are materially different from 




Fig. 21. 



those in the section b-c, or the induced E.M.F.'s in the section a-b will now 
be equal as well as opposite to those in b-c. 

After determining the proper length of the section I, the section may be 
applied consecutively to a line which is to be transposed, by laying it off 
in the manner of using a foot rule in the measurement of a distance. If 
the total length of line is not a multiple of I, the last section may be taken 
somewhat longer or shorter than the standard section, but it should be not 



2f- 



& 



Fig. 22. 



II- 



Af 



-*— 



$ 



Fig. 22A. 



more than one and a half regular sections nor less than half a regular sec- 
tion. Fig. 21 shows a line having four and a quarter transposition sections. 
A* transposition at the junction of two adjacent sections is without effect 
on those sections, therefore the Fig. 22A is equivalent to Fig. 22. 



This 



n 



j£ £, 



Fig. 23. 



TRANSPOSITION OF LINES. 



287 



is true only when the standard section length is not in excess of that per- 
missible, as outlined above. 

The transposition of power and lighting circuits is not often necessary. 
In complicated networks it is almost unknown, because the troublesome 



4 4 4 



Fig. 24 



circuits are usually short. At the frequencies used in power and lighting 
the transposition section may be several miles in length, much longer than 
in telephone practice. 

The transposition of polyphase lines is sometimes employed to balance 
inductive effects which would otherwise be troublesome. 




Fig. 25. 



Fig. 23 shows a balanced three-phase line, which would be transposed 
only to avoid inductive interference with other lines. 

Fig. 24 shows an unbalanced three-phase line and Fig. 25 shows the 
method of transposing it to secure a balanced circuit, or equal inductance 
per phase. Fig. 26 illustrates the application of the section shown in Fig. 8. 



— f 



-H 



Fig. 26. 



The transposition of telephone lines becomes a complicated problem when 
there are many circuits, as it is necessary to arrange the transpositions in 
such a manner that each circuit is transposed with respeet to all the others; 



288 



CONDUCTORS. 



also the circuits that are adjacent must have more frequent relative trans- 
positions than those further apart. The method of deriving differently 
transposed types of circuits is given in an American Institute paper on 
4, The Transposition of Electrical Conductors." * 

Fig. 27 shows fifteen different types of transposition. The "exposure," 
as it is termed, of circuit 1 to circuit 2 is ±; of 1 to 3 is i; of 2 to 3 is £; 
because a transposition at the junction of two sections, each transposed at 



Number of 
Transpositions 

o= 



31 



4 ?C 

5=X= 

6 ?C 

7 X = 

8.ZZX 

9ZZX 

10 — X 

11 X 



W 



zxzx: 



DCDC 



IXZ3C 



DCZDC 



IXZDC 



12ZZX 

13 =X 

14 ZDCZ)CDCDCZ>CD( 
15 



dczxizx: 



Type Derivation 

No. of Type 
=0 



IXZDCDC 



XZDCZXIZJCZI^CZXZ 



-^"?- 



DCDC 



DCDC 



DCZ>CDC 



:3 = 1 + 2 
A 

:5 . - 1 + 4 
-6 = 2+4 

:: =3 + 4 

18 

19 = 1 + 8 

110= 2 + 8 

:ii= 3 + 8 

112= 4+8 
113= 5+8 
114=6 + 8 

115= 7 + 8 



-J 



Fig. 27 



its center, has almost no beneficial effect. The exposure of 1 to 5 is 4; of 
2 to 6 and 3 to 7, £; of 2 to 8 and 2 to 9, <fo ; and so on. The tabulated ex- 
posures are given in Fig. 28, in terms of the length 1 of a transposition sec- 
tion. The method may be extended as far as desired, but 15 types are 
usually sufficient. 

It has been found experimentally that one-fourth mile exposures are sat- 
isfactory in telephone work for circuits immediately adjacent to each other; 
for circuits not adjacent the transpositions may be farther apart. The 
distance I in Fig. 27 may then be taken at four miles, and fifteen differently 
transposed types are available. The method may be extended to thirty- 
two types with an eight mile section. The eight mile section is rather 
cumbersome for most work and a four mile section is more adaptable to gen- 
eral conditions. 

The transposition of telephone circuits against power and lighting circuits 
should be treated on the sectional principle. It is possible to improve 
some cases by reducing the separation between the wires of the power or 
lighting circuit; this is usually the cheapest plan if the transposition section 



* Vol. XXIII, page 659, Oct. 28, 1904. 



TRANSPOSITION OF LINES. 



289 



is long and there are many telephone circuits. For the voltages less than 
5000, in distribution systems, a separation of 18 to 24 inches is ample for 
spans less than 150 feet. 

At points where telephone lines are transposed against power and light- 
ing circuits, all the telephone circuits should be transposed; the cross-talk 
exposures will not be altered. 



Exposure of Type No. 



To 





i 


2 


3 


1 4 


5 


6 


7 


8 


9 


10 


n 


12 


13 


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£ 


£ 


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5 


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£ 


£ 


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6 


£ 


£ 


£ 


£ 


i 


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4 




















7 


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£ 


£ 


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15 


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re 


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A 


A 


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— 












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re 


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T5 


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re 


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re 


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i 


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11 


A 


1 
re 


A 


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1 


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re 


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re 


A 


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4 


i 


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12 


A 


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A 


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re 


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£ 


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13 


A 


A 


A 


A 


A 


A 


A 


A 


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£ 


£ 


£ 


* 






14 


A 


1 


A 


A 


1 

re 


A 


A 


A 


£ 


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1 


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i 


i 




15 


A 


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T5 


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re 


A 


A 


£ 


£ 


£ 


£ 


1 


i 


I 



Fig. 28. 



Fig. 29 shows a typical case and its treatment. The procedure is to lay 
out transposition sections to take care of the induction from the power or 
lighting circuits, the "induction sections," so that they will not interfere 
with the "cross-talk sections;" to do this it is necessary that the junction 
of two induction sections occur at the same place as the cross-talk transpo- 
sitions; the induction sections should also terminate at points opposite 
changes in the distributing circuits, as on opposite sides of these points the 
induction will not be equal. 

When telephone lines are exposed to complicated distribution systems, 
transposition, as a rule, is not effective. 



290 



CONDUCTORS. 



D 




: 






? 


: 


1 


n 




r» «• u o «■• 


v 


rv ii 


. 


j 


-. * 11 o *• 


Induction 




Induction 


etion > 
Induction 


Induction 


Sec 


tion 




Seel 


;ion 


Section 




Section 



Fig. 29. 



Niagara Lin«*, — The conductors on this line are bare cables of 19 
strands, equivalent to 350,000 circuit mils, and are arranged as shown in 
the following diagram. The first arrangement was with two three-wire cir~ 

A 



-4-1-8^- 



± 




: 



Fig. 30. Niagara-Buffalo Line. 11000 to 22000 Volts. 

cuits on the upper cross-arm, the wires being 18 inches apart. So much 
trouble was experienced from short circuits by wires and other material 
being thrown across the conductors, that the middle wire was lowered to 
the bottom cross-arm as shown, since which time no trouble has been 
experienced. With porcelain insulators tested to 40,000 volts there is no 
appreciable leakage. These circuits are interchanged at a number of 
points to avoid inductive effects. 



TRANSPOSITION OF LINES. 



291 



Three-Phase Circuits. — The diagram (Fig. 31) shows another ar- 
rangement now seldom used although it makes lines conveniently accessible 
for repairs. Under the ordinary loads usual in the smaller plants the unbal- 
ancing effect is so small # as to be inappreciable. 




i. 



Fiq. 31. Convenient Arrangement of Three-Phase Lines for, 
600010,000 Volts. 



h— «*-h 



•&, 



-L.6, 



Fig. 32. 



Arrangement of Two-Phase Circuit, 
of Phases necessary. 



No Reversal 



Two-Phase, Four-wire Circuits. — The arrangement of conductors 

shown in Fig. 32 is probably the best for two-phase work; as no reversals 
of wires are needed, the inductive effects of the wires of one circuit on those 
of the other are neutralized. 



292 CONDUCTORS. 



Two-Phase Circuit* in lame Plane. — If the phases are treated 
as separate circuits, and carried well apart, as shown in Fig. 33, the interfer- 




Fio. 33. 

ence is trifling; and should the loads carried be heavy enough to cause notice- 
able effect, the reversal of one of the phases in the middle of its length will 
obviate it. The following diagram illustrates the meaning. 



PH AS E B. y C 



Fig. 34. Arrangement of Two-Phase, Four-Wire Circuit with Wires on 
same Plane. Wires of One Phase should be interchanged at the Middle 
Point of the Distance between Branches, and between its Origin and 
First Branch. 

Messrs. Scott and Mershon of the Westinghouse Electric and Manufactur- 
ing Co. have made special studies of the question of mutual induction of 
circuits, both in theory and practice; and their papers can be found in the 
files of the technical journals, and supply full detail information. 

Mutual Neutralization of Capacity and Inductance. — In 
order to completely neutralize phase displacement due to distributed in- 
ductance a distributed capacity is essential. Localized capacity can, how- 
ever, produce a partial neutralization. Excessive distributed capacity 
can also be partially neutralized by inserting inductances at proper inter- 
vals. In treating of local neutralization of capacity by inductance, the 
assumption is frequently made that the capacity is constant irrespective 
of the voltage, and that the inductance is constant irrespective of the 
current. Under these conditions neutralization can be obtained. As, 
however, inductance is dependent upon the permeability of the associated 
magnetic circuit, and permeability varies with the saturation of the iron, — 
that is, with the current, — complete neutralization cannot be obtained 
with iron inductances. 

Over-excited synchronous motors, or synchronous converters, take cur- 
rents which lead the electromotive force impressed upon them, and they 
therefore operate as condensers, and they may be utilized advantageously 
in neutralizing the line inductance. The power factor of the transmission 
system can therefore be varied by varying their excitation. 



BELL WIRING, 



293 



10§§ IX SHEATH OF THREE-CONDUCTOR 

COVERED CABLEI. 



IEAD 



John T. Morris (Electrician, London) gives the following formula, con- 
firmed by experiments, for the loss of power in the lead sheath of a three- 
conductor cable. 

Let / = current in amperes. 

/ = frequency. 

I = length of cable in 1000 ft. 
t = thickness of sheath in mils. 
Then: Watts loss = 123 X 10^° PfW' 1 . 

If the cable is placed in an iron pipe the loss is increased about 75%. 



BELL WIRING. 

The following diagrams show various methods of connecting up-call bells 
for different purposes, and will indicate ways in which incandescent lamps 
may also be connected to accomplish different results. 



5=6= 



Fio. 35. 



One Bell, operated by 
One Push. 



Fig. 36. 



One Bell, operated by 
Two Pushes. 



t_t 



J- 



Fig. 37. 



Two Bells, operated by 
One Push. 



Fig. 38. Two Bells, operated by 
Two Pushes. 



When two or more bells are required to ring from one push, the common 
practice is to connect them in series, i.e., wire from one directly to the next, 
and to make all but one single-stroke ends. Bells connected in multiple 
arc, as in diagram No. 24, give better satisfaction, although requiring more 
wire. 



Fig. 39. Three-Line Factory Call. 
A number of Bells operated by 
any number of pushes. All bells 
rung by each push. 



Fig. 40. Simple Button, Three- 
Line Return Call. One set of 
battery. 



ug gCM'I- j 

Fig. 41. Simple Button, Two-Line 
and Ground Return Call. One set 
of battery. 



6 T*1 

Fig. 42. Two-Line Return Call. 
Illustrating use of Return Call 
Button. Bells ring separately. 



294 



CONDUCTORS. 



Fig. 43. One-Line and Ground Return 
Call. Illustrating use of Return Call 
Button. Bells ring separately. 



Fig 44. Simple Button, Two- 
Line Return Call. Bells ring 
together. 



Q 




Fig. 45. Simple Button, One-Line 
and Ground Return Call. Bells 
ring together. The use of com- 
plete metallic circuit in place of 
ground connection is advised in 
all cases where expense of wire 
is not considerable. 



Fig. 46. Four Indication Annuncia- 
tor. Connections drawn for two 
buttons only. A burglar alarm cir- 
cuit is similar to the above, but 
with one extra wire running from 
door or window-spring side of bat- 
tery to burglar alarm in order to 
operate continuous ringing attach- 
ment. 




<j> (j> <j> (j> <jT^ 



Fig. 47. 

Diagram of connections for control of lights from two points. 



r<- 



"ct 



JA 



~~WHML 

Fig. 48. 

Diagram of connections for control of lights from four points. By in- 
troducing other switches like A and B control can be had from any number 
of points. 



12 



Fig. 49. Four Indication Annuncia- 
tor, with extra Bell to ring from one 
Push only. Illustrating use of 
three-point button. 



Fig. 50. Acoustic Telephone with 
Magneto Bell Return Call. Ex- 
tension Bell at one end of line. 



TRANSFORMERS. 



295 



In running lines between any two points, use care to place the battery, if 
possible, near the push-button end of the line, as a slight leakage in the cir- 
cuit will not then weaken the battery. 



When mat is to be used, throw it into the circuit 
by the switch, so that when the circuit is closed by a 
person stepping on the mat, the automatic drop will 
keep it closed, and both bells will continue to ring 
until the drop is hooked up again. 



Fig. 51. Diagram of Burglar-Alarm Mat, two Bells, 
one Push and Automatic Drop; all operated by one 
battery. Both bells ring from one push or mat, as 
desired, by changing the switch. 




GAS-LIGHT WIRIIte. 




, SPARK COIL 

■Air'ERy 




Fig. 52. Pendant and Automatic Gas- Fie. 53. Pendant Gas-Lighting Cir- 
Lighting Circuit, with Switchboard. cuit, with Switchboard, Relay 

and Tell-Tale Bell. 



WIM1VO FOR GEIERATOR9. 

The generators are rated by their volt-ampere capacity and their apparent 
watts, and not their actual watts, so that the size has to be increased if the 
power-factor of the system is low. 



WIIU\I, JbOJ% XllAA*AOMI?l.E»S. 



For lighting circuits using small transformers, the voltage at the prima- 
ries of the step-down transformers should be made about 3% higher than the 
secondary voltage multiplied by tho ratio of transformation, to allow for the 
drop in transformers. In large lighting transformers this drop may be as low 
as 2%. Standard lighting transformers have a ratio of 10 to 1 or some mul- 
tiple thereof. 

For motor circuits, the voltage at the primaries of step-down transformers 
should be made about 5% higher than the secondary voltage multiplied by 
the ratio of trancformation. Transformers used with 110 volt motors on any 
60-cycle system should have a ratio of 4^ to 1, 9 to 1, or 18 to 1 respectively 
for 1040, 2080, and 3120 volt generators. The transformer capacity in kilo- 
watts should be the same as the motor rating in horse-power for medium-sized 
motors, and slightly larger for small motors and where only two trans- 
formers are used. 



296 



CONDUCTORS. 



Capacities of Transformers to be used with ©©-Cycle 
Induction Motors. 





Kilowatts per Transformer. 


Size of Motor. 




Horse-Power. 








Two Transformers. 


Three Transformers. 


1 


.6 


.6 


2 


1.5 


1 


3 


2 


1.5 


5 


3 


2 


7* 


4 


3 


10 


5 


4 


15 


7.5 


5 


20 


10 


7.5 


30 


15 


10 


50 


25 


15 


75 




25 



WIROG TOR I\IM(TIO\ MOTORS. 

The standard (General Electric) induction motors for three-phase cir- 
cuits are wound for 110 volts, 220 volts, and 550 volts; motors of 50 H.P. 
and above are, in addition, wound for 1040 volts and 2080 volts. Motors 
for the two latter voltages are not built in sizes of less than 50 H.P. Where 
the four-wire, three-phase distribution system is used, motors can also be 
wound for 200 volts. 

The output of an induction motor varies with the square of the voltage at 
the motor terminals. Thus, if the volts at the terminals happen to be 15% 
low, that is, only 85% of the rated voltage, a motor, which at the rated volt- 
age gives a maximum of 150% of its rated output, will be able to give at the 
15% lower voltage, only (A 5 o) 2 X 150 = 108% of its rated output, and at full 
load will have no margin left to carry over sudden fluctuations of load while 
running. 

Thus it is of the utmost importance to take care that the volts at the motor 
terminals are not below the rated volts, but rather slightly above at no load, 
so as not to drop below rated voltage at full-load or over-load. 

The output of the motor may be increased by raising the potential; in 
this case, however, the current taken is increased, especially at light loads. 

The direction of rotation of an induction motor on a three-phase circuit 
can be reversed by changing any two of the leads to the field. 

Like all electrical apparatus, the induction motor works most efficiently 
at or near full load, and its efficiency decreases at light load. Besides this, 
when running at light load, or no load, the induction motor draws from the 
lines a current of about 30% to 35% of the full-load current. This current 
does not represent energy, and is not therefore measured by the recording 
watt-meter; it constitutes no waste of power, being merely what is called an 
idle or "wattless" current. If, however, many induction motors are oper- 
ated at light loads from a generator, the combined wattless currents of the 
motors may represent a considerable part of the rated current of the gener- 
ator, and thus the generator will send a considerable current over the line. 
This current is wattless, and does not do any work, so that in an extreme 
case an alternator may run at apparently half-load or nearly full-load cur- 
rent, and still the engine driving it run light. While these idle currents are 
in general not objectionable, since they do not represent any waste of 
power, they are undesirable when excessive, by increasing the current-heat- 
ing of the generator. Therefore it is desirable to keep the idle currents in 
the system as low as possible, by carefully choosing proper capacities of 
motors. These idle currents are a comparatively small per cent of the total 



CONNECTIONS. 



297 



current at or near full-load of the motor, but a larger per cent at light loads. 
Therefore oare should be taken not to install larger motors than necessary 
to do the required work, since in this case the motors would have to work 
continuously at light loads, thereby producing a larger per cent of idle cur- 
rent in the system than would be produced by motors of proper capacity; 
that is, motors running mostly between half-load and full-load. 

Current taken by General Electric Co., Three -Phase In- 
duction motors at HO Volts. 







Starting 


Starting 


H.P. of Motor. 


Full-Load 


Current at 


Current 


Current. 


150% of Full- 
Load Torque. 


at Full-Load 






Torque. 


1 


6.5 


19 




2 


12 


36 




3 


17 


54 




5 


28 


♦42-84 


28 


10 


55 


70 


55 


15 


80 


120 


80 


20 


105 


167 


105 


30 


150 


252 


150 


50 


250 


400 


250 


75 


370 


585 


370 


100 


500 


825 


500 


150 


740 


1180 


740 



The current taken by motors of higher voltage than 110 will be proportion- 
ally less. The above are average current values, and in particular cases the 
values may vary slightly. 

conricFCTiours of transformers for irrnoo. 

The connection of three transformers, with their primaries, to the genera- 
tor and their secondaries to the induction motor, in a three-phase system, 
are shown in Fig. 26. The three transformers are connected with their pri- 
maries between the three lines leading from the generator, and the three 
secondaries are connected to the three lines leading to the motor, in what 
is called delta connection. 

The connection of two transformers for the supply of an induction motor 
from a three-phase generator is shown in Fig. 55. It is identical with the 





Fig. 54. 



Fig. 55. 



arrangement in Fig. 54, except that one of the transformers is left out, and 
the two other transformers are made correspondingly larger. The copper 
required in any three-wire, three-phase circuit for a given power and loss is 
75%, as compared with the two- wire, single-phase, or four- wire, two-phase 
system, having the same voltage between lines. 



* The 5 H.P. motor is made with or without starting-switch. 



298 



CONDUCTORS. 



The connections of three transformers for a low-tension distribution sys- 
tem by the four-wire, three-phase system are shown in Fig. 56. The three 
transformers have their primaries joined in delta connection, and their sec- 
ondaries in " Y " connection. The three upper lines are the three main 
three-phase lines, and the lowest line is the common neutral . The difference 
of potential between the main conductor is 200 volts, while that between 
either of them and the neutral is 115 volts. 200 volt-motors are joined to the 



t_ 


j Hi 


l_ 


i ladov. 


s 


•iifcvJ 



Fig. 56. 



3200 



IC 



Fig. 57. 



mains while 115 volt-lamps are connected between the mains and the neutral. 
The neutral is similar to the neutral wire in the Edison three-wire system, 
and only carries current when the lamp load is unbalanced. 

The potential between the main conductors should be used in the formula?, 
and the section of neutral wire should be made in the proportion to each of 
the main conductors that the lighting load is to the total load. When lights 
only are used, the neutral should be of the same size as either of the three 
main conductors. The copper then required in a four- wire, three-phase sys- 
tem of secondary distribution to transmit a given power at a given loss is 
about 33.3 %, as compared with a two-wire, single-phase system, or a four- 
wire, two-phase system having the same voltage across the lamps. 

The connections of two transformers for supplying motors on the four-wire, 
two-phase system are shown in Fig. 57. This system practically consists of 
two separate single-phase circuits, half the power being transmitted over 
each circuit when the load is balanced. The copper required, as compared 
with the three-phase system to transmit given power with given loss at the 
same voltage between lines, is 133£ % — that is, the same as with a single- 
phase system, 



STANDARD SYMBOLS FOR WIRING- PLANS 
AS ADOPTED BY THE NATIONAL ELEC- 
TRICAL CONTRACTORS ASSOCIATION. 

(Copyrighted.) 

)3£ Ceiling Outlet ; Electric only. Numeral in center indicates 
number of Standard 16 C.P. Incandescent Lamps. 

]X<2" Ceiling Outlet ; Combination, § indicates 4-16 C.P. Standard 

Incandescent Lamps and 2 Gas Burners. If gas only ]/[ 

Mn§[ Bracket Outlet ; Electric only. Numeral in center indicates 
number of Standard 16 C.P. Incandescent Lamps. 

MjXfar Bracket Outlet ; Combinations. $ indicates 4-16 C.P. Standard 

Incandescent Lamps and 2 Gas Burners. If gas only * 



H2J "Wall or Baseboard Receptacle Outlet. Numeral in center indi- 

cates number of Standard 16 C.P. Incandescent Lamps. 

j4~f Floor Outlet. Numeral in center indicates number of Standard 

16 C.P. Incandescent Lamps. 

j3 6 Outlet for Outdoor Standard or Pedestal; Electric only. Numeral 
indicates number of Standard 16 C.P. Incandescent Lamps. 

0-|- Outlet for Outdoor Standard or Pedestal ; Combination. | indi- 
cates 6-16 C.P. Standard Incandescent Lamps ; 6 Gas Burners. 

® Drop Cord Outlet. 

® One Light Outlet, for Lamp Receptacle. 

(f Arc Lamp Outlet. 

Q Special Outlet, for Lighting, Heating and Power Current, as 

described in Specifications. 



C^OO Ceiling Fan Outlet. 

5 1 S. P. Switch Outlet. 

g 2 D. P. Switch Outlet. 

g 3 3- Way Switch Outlet. 

g 4 4-Way Switch Outlet. 

g D Automatic Door Switch Outlet. 

g E Electrolier Switch Outlet. 

g Meter Outlet. 

m Distribution Panel. 

£§!§gl8B Junction or Pull Box. 



Show as many Symbols as there 
are Switches. Or in case of a 
very large group, of Switches, 
indicate number of Switches 
by a Roman numeral, thus ; 
S' XII; meaning 12 Single Pole 
Switches. 

Describe Type of Switch in 
Specifications, that is, Flush 
or Surface, Push Button or 
Snap. 



1^3 



Motor Outlet ; Numeral in center indicates Horse Power. 

Motor Control Outlet. 

Transformer. 

299 



300 STANDARD SYMBOLS FOR WIRING PLANS. 



Main or Feeder run concealed 
under floor. 

Main or Feeder run concealed 
under floor above. 

Main or Feeder run exposed. 

Branch Circuit run concealed 
under floor. 

Branch Circuit run concealed 
under floor above. 



Heights of Center of Wall 
Outlets (unless otherwise 
specified): 

Living Rooms 5 ft. 6 ins. 

Chambers 5 ft. ins. 

Offices 6 ft. ins. 

Corridors 6 ft. 3 ins. 

Heights of Switches (unless 
otherwise specified) : 

4 ft. ins. 



H 

8 



~ — Branch Circuit run exposed. 
" • " Pole Line. 
* Riser. 

Telephone Outlet ; Private Service. 
Telephone Outlet ; Public Service. 
Bell Outlet. 
UV Buzzer Outlet. 

[•J 2 Push Button Outlet ; Numeral indicates number of Pushes. 
"K§> Annunciator ; Numeral indicates number of Points. 

— ^ Speaking Tube. 

— © Watchman Clock Outlet. 

— J Watchman Station Outlet. 

— © Master Time Clock Outlet. 

— J) Secondary Time Clock Outlet. 

ffl Door Opener. 

|Xl Special Outlet ; for Signal Systems, as described in Specifications. 

j|||||l||| | Battery Outlet. 

{Circuit for Clock, Telephone, Bell or other Service, run under 
floor, concealed. 
Kind of Service wanted ascertained by Symbol to which line 
connects. 

{Circuit for Clock, Telephone, Bell or other Service, run under 
floor above, concealed. 
Kind of Service wanted ascertained by Symbol to which line 
connects. 

In writing circular mill sizes a quick and handy method is to draw a circle 
and place in it the size in hundred thousands of circular mills, as, 
(?) = 300,000, (§) = 750,000, @ = 250,000. This is unhandy to print. 



UNDERGROUND CONDUITS AND 
CONSTRUCTION. 

With the establishment of the first commercial Morse telegraph line 
probably commences the history of the "underground wire" when a 
gutta-percha covered cable was laid in a trench made by an ox-drawn plough. 

Stages in the evolution of the present " monolithic " conduit are promi- 
nently marked by the system of grouping wires permanently installed and 
separated by the pouring about them in the trench of various insulating 
compounds; by the "built up system" made of creosoted boards so placed 
as to form square channels or ducts; by the "pump log" system or squared 
timber bored to required size and creosoted; by the cement lined iron pipe 
system; by the use of paper moulded and treated with dielectric compounds; 
and by the now very largely used vitrified clay. Clay conduits should be 
manufactured from a clay which will vitrify to a highly homogeneous and 
non-absorbent condition and be free from chemical elements (iron, sulphur, 
etc.) which under the action of heat in the kilns result in nodes or blisters 
in the ware. 

There are two established styles of clay conduit commonly designated as 
"single duct" and "multiple duct." The standard unit of the single duct 
is of square cross section measuring 4$ " by 4$" with corners chamfered, is 
18 inches in length, and has a 3£ inch round bore or hole. The standard 
multiple duct units are of two, three, four, or six duct sections, the bore of 
each duct of any section being square and measuring 3£ by 3|, the interior 
and exterior wall being f" thick; the lengths of units are, for two and three 
duct, 24 inches, and for four or six duct 36 inches. The demand for 3£ inch 
and 4 inch bores or even larger is constantly increasing. Multiple duct 
conduit of nine duct and twelve duct sections have been offered to the 
trade but so far have not come into extensive use. 

Single duct conduits being more flexible are better adapted to use where 
service pipes, curves, or obstacles are frequently encountered. Laid with 
broken joints the possibility of the heat from a burning cable , being com- 
municated to a neighboring cable, is precluded. Where high construction 
on a small base (two ducts wide by more than five ducts high) is required, 
singles are not used to advantage. A mason should, under fair working 
conditions, average in a day of eight hours from twelve hundred to sixteen 
hundred duct feet of single duct conduit. 

Multiples have in their favor fewer joints, greater weight per unit, and the 
fact that their installation requires only unskilled labor. Two men selected 
from a gang of laborers will lay from eighteen hundred to twenty-four hun- 
dred duct feet per day of ten hours. 

Through town or city streets the conduit should have a foundation of 
concrete at least 3 inches thick. Where frequent excavations for other 
works are probable a complete encasement of 3 inches to 4 inches of concrete 
should be placed on both sides and on top of the ducts. The side protec- 
tion is, however, sometimes omitted and creosoted boards substituted for 
concrete on top. The top covering over ducts should be not less than 24 
inches below the surface of the street. 

The several conduit terms are generally defined as follows: 

The word "Conduit" means the aggregation of a number of hollow 
tubes of duct material and includes all of the ducts in a cross section of 
the subway. In general a conduit will consist of four ducts or more. 

The word "Duct" means a single continuous passageway between man- 
holes or through any portion of the conduit or laterals. 

The word "Manhole" means an underground chamber built to receive 
electrical equipment and suitable to give access to the conduit. 

The word "Service Box" means an underground chamber similar to a 
manhole but of smaller size, and designed primarily to give access to dis- 
tributing conductors. 

301 



302 



UNDERGROUND CONDUITS. 



The word "Lateral" means one or more ducts extending from a manhole 
or service box or from one or more of the main conduit ducts to some dis- 
tributing point. In general laterals will consist of one or two ducts for the 
same service connections. One or more laterals may be installed in the 
same trench. 

Manholes vary so much according to the ideas of the different engineers 
that it is difficult to give data that would suit all of them. However, the 
average size of manhole is 5' X 6' X 6' in the clear with a 12" wall. The 
covers for same vary from 800 to 1400 lbs. The general practice is to 
have ventilated covers and sewer connections with automatic back-water 
traps. 

The Service Boxes are made generally of concrete with an 8" wall, either 
2' X 2' or 2' X 3' in length and width, and extending in most cases to the 
top layer of the conduit system, which would make the depth of the 
service boxes vary according to the depth of the conduit system proper, 
the upper tier of ducts being used for distribution. Covers for service boxes, 
including inside pan, weigh from 400 to 600 lbs. ; 

Usual Practice of Conduit Work. 

Manhole walls, where built of concrete are generally 8 to 12 inches thick, 
made of Portland Cement concrete, using, \\ inch stone, mixed in the pro- 
portion of an 1-2-5 and in some instances as high as 1-3-8. While in some 
cases the conduits proper are surrounded with Portland Cement concrete, 
the usual practice throughout the country is with casing of hydraulic cement 
concrete in a 1-2-5 mixture, stone \ inches to 1 inch. 

The Cost of Conduits. 

(A. V. Abbot in Electrical World and Engineer.) 

The items of cost of conduit construction are: 

1. Duct material. 2. Pavement per square yard. 3. Street excava- 
tion per cubic foot, including the removal of paving, the refillment of the 
excavation after the ducts are laid, and the temporary replacement of the 
paving. 4. Concrete deposited in place. 5. Labor of placing duct ma- 
terial 6. Engineering expenses. 7. Manholes. 8. Removal of obstacles. 



TABLE No. 1. 
Cost of Manholes in Dollars. 

A. Brick with Brick Roof. 



Item. 


Amount. 


Rate (Dollars). 


Min. 

Amt. 

$ 


Per 
Ct. 


Av. 

Am. 

$ 


Per 
Ct. 


Max. 
Amt. 


Per 


Min. 


Ave. 


Max. 


Ct. 


Excavation 
Concrete . 
Brick . . 
Cover . . 
Iron . . . 
Repaving . 
Cleaning . 


375 cu. ft. 

.7 yard 

2200 

1 
500 lbs. 
6 yards 
10 loads 


.02 

5.00 

12.00 

5.00 

.015 

.75 

.50 


.03 
7.00 
15.00 
10.00 
.03 
2.00 
.75 


.04 

9.00 

18.00 

15.00 

.05 

4.00 

1.00 


7.50 
3.50 
26.40 
5.00 
7.50 
4.50 
5.00 


12.6 
5.9 

44.5 
8.4 

12.6 
7.6 
8.2 


11.25 
4.90 
33.00 
10.00 
14.00 
15.00 
7.50 


11.8 
5.3 
35.3 
10.6 
16.1 
12.8 
8.1 


15.00 
6.00 
39.60 
15.00 
25.00 
24.00 
10.00 


11.2 
4.4 
29.4 
11.2 

18.6 
17.8 

7.4 


Totals . . 


.... 








59.40 


100.0 


93.65 


100.0 


134.00 


100.0 



COST OF UNDERGROUND CONDUITS. 303 

B. Brick ivith Concrete Roof. 







Rate (Dollars) 














Item. 


Amount. 


Per Unit. 


Min. 

Amt. 

% 


Per 
Ct. 


Av. 

Am. 

$ 


Per 
Ct. 


Max. 
Amt. 


Per 


Min. 


Ave. 


Max. 


ct. 


Excavation 


375 cu. ft. 


.02 


.03 


.04 


7.50 


14.8 


11.25 


14.4 


15.00 


13.8 


Concrete . 


1.9 yards 


5.00 


7.00 


9.00 


9.50 


18.7 


13.30 


17.0 


17.10 


15.7 


Brick . . 


1600 


12.00 


15.00 


18.00 


19.20 


37.8 


24.00 


30.9 


28.80 


25.7 


Cover . . 


1 


5.00 


10.00 


15.00 


5.00 


9.0 


10.00 


12.8 


15.00 


13,8 


Repaving . 


6 yards 


.75 


2.00 


4.00 


4.50 


8.9 


12.00 


15.4 


24.C0 


21.9 


Cleaning . 


10 loads 


.50 


.75 


1.00 


5.00 


9.9 


7.50 


9.5 


10.00 


9.1 


Totals . . 






• • 


• • 


50.70 


100.0 


78.05 


100.0 


109.90 


100.0 



C. Concrete Manhole. 



Item. 


Amount. 


Bate (Dollars) 
Per Unit. 


Min. 

Amt. 


Per 
Ct. 


Av. 
Am. 


Per 
Ct. 


Max. 
Amt. 


Per 


Min. 


Ave. 


Max. 


Ct. 


Excavation 
Concrete . 
Cover . . 
Repaving . 
Cleaning . 


375 cu. ft. 

4.5 yards 

1 

6 yards 

10 loads 


.02 

5.00 

5.00 

.75 

.50 


.03 

7.00 

10.00 

2.00 

.75 


.04 

9.00 

15.00 

4.00 

1.00 


7.50 
22.50 
5.00 
4.50 
5.00 


16.8 
50.5 
11.2 
10.2 
11.2 


11.25 
31.50 
10.00 
12.00 
7.50 


15.5 
43.6 
13.9 
16.6 
10.4 


15.00 
40.50 
15.00 
24.00 
10.00 


14.3 

38.8 

14.4 

23.0 

9.5 


Totals . . 


.... 


• • 


• ■ 


• • 


44.50 


100.0 


72.25 


100.0 


104.50 


100.0 



Whenever practicable, a sewer connection to each manhole is desirable 
to provide exit for street drainage. Such sewer connections are essential 
in all cases where manholes are equipped with ventilating covers, otherwise 
the manholes will fill during every storm. 

TABLE Wo. «. 
Cost of Sewer Connections in Dollars. 







Rate (Dollars) 


















Per Unit. 


Min. 




Ave. 




Max. 




Item. 


Amount. 




Amt. 


Per 


Am. 


Per 


Amt. 


Per 








Min. 


Ave. 
.03 


Max. 
.04 


$ 


Ct. 


$ 


Ct. 


$ 


Ct. 


Excavation 


225 cu. ft. 


.02 


4.50 


35 1 


6.75 


26 


9.00 


21.4 


Concrete . 


5 yards 


.75 


2.00 


4.00 


3.75 


29.2 


10.00 


38.8 


20.00 


47.0 


Brick 


1 


1.00 


2.50 


4.00 


1.00 


7 6 


2.50 


19.6 


4 00 


9 3 


Cover 


16 feet 


.04 


.07 


.10 


.64 


5 


1.12 


4 4 


1.60 


3 6 


Repaving . 


2 loads 


.50 


.75 


1.00 


1.00 


7 6 


1 50 


5.8 


2 00 


4 7 


Cleaning . 


1 


2.00 


4.00 


6.00 


2.00 


15.5 


4.00 


15.4 


6 00 


14 


Totals . . 


. . . 








12.89 


100.0 


25.87 


100 


42.60 


100 



304 



UNDERGROUND CONDUITS. 



Manholes will occur at intervals of from 250 to 500 feet, consequently 
the constant cost per conduit foot for this item is obtained by dividing the 
various manhole costs by the distances between them. 



TABLE No. 3. 
Constant Cost per Conduit foot for Manholes in Dollars. 







Distance between Manholes in Feet. 




250 


300 


350 


400 


500 


Brick manhole with 
brick roof . . . 


(Min. 
] Ave. 
( Max. 


.238 
.372 
.536 


.196 
.310 

.427 


.170 

.248 
.384 


.148 
.236 
.335 


.118 
.186 
.268 


Brick manhole with 
concrete roof . . 


( Min. 
< Ave. 
( Max. 


.203 
.300 
.440 


.169 
.260 
.363 


.145 
.223 
.314 


.127 
.195 

.272 


.102 
.156 
.218 


Concrete manhole 


(Min. 
I Ave. 
(Max. 


.176 
.278 
.416 


.148 
.242 
.347 


.127 
.209 
.298 


.111 

.180 
.260 


.089 
.144 
.208 


Sewer connection 


(Min. 
jAve. 
(Max. 


.051 

.104 
.170 


.043 

.086 
.142 


.038 
.074 
.121 


.032 
.064 
.105 


.025 
.051 

.084 



Engineering expense will vary from a minimum of 5 cents per conduit 
foot to a maximum of 12 cents, depending chiefly upon the difficulty of 
the work. 

The cost of the removal of obstacles is an item impracticable to estimate 
a priori with any degree of certainty, as it is impossible to foresee, and 
usually impracticable to ascertain, even with the greatest care, the impedi- 
ments to be encountered beneath street surface. Experience indicates 
that this expense will vary for small subways from 10 cents to 62 cents per 
foot of conduit; for medium-sized ones from 12 cents to $1.10, and for 
large conduits from 15 cents to $2.25. 

The cost of paving is partially dependent upon the number of ducts. 
It is impracticable for workmen to perform their avocations in a trench 
less than 18 inches wide, and, therefore, a strip of pavement of this width 
must be opened irrespective of the number of ducts to be installed. 

The cost of repaving will further vary with the kind of paving. In 
Table No. 4, the usual kinds of pavement encountered, the minimum, 
average, and maximum prices per square yard, and cost per conduit foot 
are given. 

Allowing a disturbance of paving for six inches on each side of the trench, 
the cost per lineal foot for small conduits will vary from 2.3 to 26.3 cents; 
for medium-sized ones from 4.6 to 29.2 cents, and for large conduits from 
6.9 to 35.0 cents. 

Similarly the cost of excavation is only partially dependent upon the 
number of ducts. 



COST OP PAVING. 



305 



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306 



UNDERGROUND CONDUITS. 



Experience shows that 3 feet 6 inches is a minimum permissible dep^ 
for the bottom of subway construction, and that the cost of street excava- 
tion will vary from two to four cents per cubic foot of material excavated, 
including the removal of the pavement, the refillment of the trench, and 
the replacement of temporary paving. The cost of excavation will, there- 
fore, stand as in Table No. 1. 

TABLE Wo. 5. 
Cost of Street Excavation per Conduit foot in Dollars, 



1 to 9 ducts 
10 to 16 ducts 
17 to 25 ducts 



Minimum 

.02 
per Cu. Ft. 



.105 
.160 
.225 



Average 

.03 

per Cu. Ft. 



.1575 

.240 

.3375 



Maximum 

.04 
per Cu. Ft. 



.210 
.320 
.450 



Table No. 5 summarizes these constant items; for conduits of from one 
to nine ducts, ten to sixteen ducts, and seventeen to twenty-five ducts, 
giving the minimum, average, and maximum prices of all, together with 
the percentage that each bears to the total. 

Table No. 6 enumerates the probable prices for the various forms of 
duct material laid into place, calculated in a manner similar to the preced- 
ing tables, including a percentage column showing the effect of each item 
upon the total expense. 

TABIE Wo. O. 
Constant Cost per Conduit Foot in Dollars. 





Minimum. 


Average. 


Maximum. 


Item. 


Cost. 


Per 
Cent. 


Cost. 


Per 

Cent. 


Cost. 


Per 

Cent. 


1 to 9 ducts. 
Excavation .... 

Paving 

Engineering .... 
Removal of obstacles . 


.105 
.0695 
.05 
.10 


32.6 
21.2 
15.2 
32.0 


.1575 

.185 

.08 

.25 


23.4 
27.5 
11.9 
37.2 


.210 
.279 
.12 
1.00 


13.0 

17.4 

7.5 

62.1 


Total 


.3245 


100.0 

38.6 
20.2 
12.1 

29.1 


.6725 

.24 
.222 
.08 
.28 


100.0 

29.1 

27.0 

9.8 

34.1 


1.609 

.32 
.3315 
.12 
1.10 


100.0 


10 to 16 ducts. 
Excavation .... 
Paving . 


.16 

.0845 


17.0 
17.7 


Engineering .... 
Removal of obstacles . 


.05 
.12 


6.5 

58.8 


Total 


.4145 


100.0 

43.0 

18.6 
9.6 

28.8 


.822 

.3375 
.26 
.08 
.35 


100.0 

32.8 

25.3 

7.8 

34.1 


1.8715 

.45 

.52 

.12 

1.25 


100.0 


17 to 25 ducts. 
Excavation .... 

Paving 

Engineering .... 
Removal of obstacles . 


.225 

.0970 

.05 

.15 


19.2 

22.2 

5.1 

53.5 


Total 


.522 


100.0 


1.0275 


100.0 


2.34 


100.0 









COST OF UNDERGROUND CONDUITS. 



307 



From the data thus collected, the total cost of a conduit of any size is 
readily determined by taking first the cost per foot of street for manholes 
and sewer connections; second, the cost of the constant street items as 
given in Table No. 6 depending upon the number of ducts, and third, 
the cost per duct foot determined from Table No. 5 multiplied by the 
number of ducts to be laid, and adding these three items together, giving 
immediately the total cost per conduit foot. 

TABLE Wo. 9. 
Cost of Duet Material in Place in Dollars, 





Minimum. 


Average. 


Maximum. 


Item. 


Cost. 


Per 

Cent. 


Cost. 


Per 
Cent. 


Cost. 


Per 

Cent. 


Hollow brick. 
Duct material . . . 

Placing 

Encasement .... 


.02 

.005 

.02 


44.4 
11.2 
44.4 


.035 

.01 

.05 


36.8 
10.5 
52.7 


.05 
.015 

.08 


34.5 
10.3 

55.2 


Total 


.045 


100.0 

67.5 

2.2 

30.3 


.095 

.05 

.0025 

.0475 


100.0 

50.0 

2.5 

47.5 

looTo - 

53.6 

3.4 

43.0 


.145 

.065 
.004 
.07 


100 


Multiple duct. 
Duct material . . . 

Placing 

Encasement .... 


.035 

.011 
.015 
.061 


46.7 

2.9 

50.4 


Total 


100.0 

62.5 

3.2 

34.3 


.10 

.06 

.004 

.05 


.139 

.08 
.006 

.088 


100 


Cement-lined pipe. 
Cement pipe. 
Wood pulp. 

Duct material . . . 

Placing 

Encasement .... 


.04 

.002 
.022 


48.2 
3.6 

48.2 


Total 


.064 


100.0 

98.04 
1.96 
0.00 


.114 

.05 

.0015 

.00 


100.0 

98.0 
3.0 
0.0 


.174 

.06 

.003 

.00 


100 


Creosoted wood. 
Duct material . . . 

Placing 

Encasement .... 


.04 

.0008 
.00 


95.0 
5.0 
0.0 


Total 


.0408 


100.00 


0515 


100 


.063 


100 













Cost per Conduit foot in Cities. 



Cost per 


Number of Ducts. 


Trench Foot. 


2 


4 


6 


12 


16 


20 


24 


Atlanta . . . 
Louisville . . 
Cincinnati . 
Boston . . . 
Springfield . . 
Brooklyn . . 


$.88 
.89 
.92 

1.06 
.90 
.95 


$1.14 
1.12 
1.18 
1.34 
1.16 
1.21 


$1.43 
1.40 
1.48 
1.65 
1.45 
1.51 


$2.31 
2.29 
2.36 
2.66 
2.34 
2.45 


$2.76 
2.76 
2.82 
3.13 

2.78 
2.91 


$3.22 
3.19 
3.26 
3.66 
3.24 
3.39 


$3.53 
3.63 
3.72 
4.10 
3.68 
3.84 



308 



UNDERGROUND CONDUITS. 



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MANHOLES. 



309 



Boston 'Edison Company Construction. 

Following are a few cuts illustrating the practice of the Boston Edison 
Co. as described by W. P. Hancock. There are also two tables giving item- 
ized cost of manholes and of conduits. 




SSSST " 




Fig. 1. Construction for Small 
Manhole. 



Fig. 2. Arched Construction for 
Large Manhole. 




j^ffi^%^t?*fofr^ 


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c«»iat;rS«fig®5;5? n ?a.^e^ss^2^#^ 



SECTION ELEVATION SECTION* B-B 

Figs. 3 and 4. Manholes. 



310 



UNDERGROUND CONDUITS. 





Section A-A 
Fig. 5. Plan and Sectional View of Manholes. 



mmm 







9 DUCTS 










48 DUCTS 
Fig. 6. Feeder Ducts in Position. 



MANHOLES. 



31] 





Fig. 7. Transformer Manhole. 



312 



UNDERGROUND CONDUITS. 




Fie. 8. 




Fig. 9. Gest's Patent Manhole Designs. 



Part of Frame 

showing 

Roughening 




Fig. 10. Sectional View of Manhole Covers. 



314 



UNDERGROUND CONDUITS. 




INNER COVER 



w 



Upper Side 
<AV/\V/\V^V/\f7\V/\V/\ V/\W\V 



I 



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aas[ra=aas!oasDDSQQs 

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STREET COVER 
Fig. 11a. Manhole ^vers. 



TIGHT COVER FOR MANHOLE. 



315 



H-,r*4-,-rff 



^^^^^^^^^^^^^g 




« IP-so"— I 4-1 



42 



PLAN OF FRAME 




Plan of Lock Bar 
Fig. 11b. Manhole Covers. 



316 



UNDERGROUND CONDUITS. 



Itemized Cost of Conduit. 

W. P. Hancock, Boston Edison Company. 



Material and Labor. 



Material. 
Lumber at $15.00 per M., or .015 cents per 

square foot, B. M 

Concrete at $4.85 per cubic yard, or 18 cents 

per cubic foot 

Mortar at $3.98 per cubic yard, or 14 cents 

per cubic foot . 

Ducts laid down beside the trench at $.0502 

per duct foot 



Labor. 
Excavate and backfill at 15 cents per hour 

or $.0278 per cubic foot 

Cut and place lumber at 20 cents per hour, 

or $.0006 per square foot B. M. . . . . 
Mix and place concrete at 15 cents per 

hour, or $.0222 per cubic foot .... 
Mix and place mortar at 25 cents per hour, 

or $.0925 per cubic foot 

Lay the ducts at 60 cents per hour, or $.0040 

per duct foot 

Haul away the dirt at 50 cents per hour, or 

$.0142 per cubic foot 

Pave the trench at $1.44 per square yard, 

or $.16 per square foot 

Cost of manholes per duct foot 

__ Total cost of manholes _ 490.28 

~ Total number of duct feet "~ 22,200 
Inspection at 50 cents per hour, or $.0033 

per duct foot 

Engineering expenses at $.0214 per duct 

foot 

Incidental expense at 5 per cent of 

total 



Cost 

per Duct 

Foot. 



.0105 
.0231 
.0026 
.0502 



.0004 
.0029 
.0016 
.0040 
.0047 
.0500 

.0221 

.0033 
.0214 
.0116 



$.2350 



Cost per 
Conduit 

Foot. 

Total 
Expense. 



.1575 
.3465 
.0390 
.7530 

.3990 
.0060 
.0435 
.0240 
.0600 
.0705 
.7500 

.3315 

.0495 
.3210 
.1740 



$3.5250 



Total 
Cost for 

each 
Item for 
the Total 

Line. 



233.10 

514.15 

58.90 

1114.44 

592.06 
9.32 
63.48 
37.00 
88.00 
104.72 
1109.92 

490.28 

73.26 

475.08 
248.22 



$5212.73 



Cost of 5' X »' X »' manhole. 

W. P. Hancock, Boston Edison Company. 

23.76 cubic feet concrete, cost in place $.202 per foot $4.78 

2,500 hard sewer bricks, cost $9.00 per M 22.50 

If S. 6" trap and connections cost 5 . 65 

30' 6" Akron sewer pipe, cost 30 cents per foot 9.00 

R. R. steel (60 lbs. to the yard), 8 pieces 6' 4" long (1013 lbs.) 

cost $.0125 per lb 12.67 

\\ yards mortar, cost per yard $3.98 4.47 

1 manhole frame and cover, 962 lbs., cost $.015 lb 14.43 

$73.50 



COST OF MANHOLES. 



317 



We shall need labor that will cost as follows: 
Excavate and backfill part of same, including that for sewer 

connections, 785 cubic feet, cost $.0278 per Foot 

Remove from street 304 cubic feet of dirt, cost 50 cents double 

load or $.0142 per foot 

Pave 11.08 yards (including manhole and sewer connection), 

cost $1.44 per yard 

1 mason, 10 hours, cost 40 cents per hour 

2 mason helpers, 10 hours each = 20 hours, cost 15 cents per hour, 



$21.82 

4.3^ 

15.95 
4.00 
3.00 
$49.07 
Total cost 1 manhole, complete $122.o7 

Cost of Underground Conduits in Cliicag-o. 

G. B. Springer, civil engineer of Chicago Edison Co., says: 
The difference in local conditions, variations in cost of material and labor, 
make it very difficult to give a set of figures which will hold good in many 
places or in fact in the same place under different circumstances. 

The following table, however, is submitted as a guide in approximating 
the cost of work of this character as a result of conduit construction cov- 
ering ten years in Chicago. The cost of manholes is not included in this 
table, but is given in the one following. 

Table for Estimating* Cost of Conduit, Per Duct Foot, in 
Different Groups, in Various Pavements: 



Kinds of Pavement 


Number of Ducts. 




















2 


4 


6 


9 


12 


16 


20 


25 


30 


No pavement 


$.18 


$.18 


$.18 


$.18 


$.18 


$.18 


$.18 


$.18 


$.18 


Macadam 


.24 


.21 


.20 


.20 


.19 


.19 


.19 


.19 


.19 


Cedar 


.26 


.22 


.21 


.20 


.20 


.19 


.19 


.19 


.19 


Cedar reserve and granite . 


.31 


.24 


.23 


.21 


.21 


.20 


.20 


.20 


.19 


Granite reserve 


.43 


.31 


.28 


.24 


.24 


.23 


.22 


.21 


.21 


Asphalt and brick reserve . 


.68 


.43 


.37 


.31 


.29 


.26 


.24 


.24 


.23 



The following table contains approximate figures based on conditions 
prevailing in Chicago, and may be used as a guide in estimating the cost of 
conduit construction in connection with the table preceding. 

Table for .Estimating* Total Cost of Manholes in Different 
Kinds of Pavements : 



Kinds of Pavement. 


Size of Manholes in Feet. 


3X3 

$41 
42 
43 

44 
46 

50 


3X4 

$47 
48 
49 

50 
53 

58 


4X4 


4X5 


5X5 


6X6 


6X7 


7X7 


8X8 


9X9 


No pavement .... 

Macadam 

Cedar 

Cedar reserve 

and granite .... 
Granite reserve . . . 
Asphalt and brick 

reserve 


$53 
55 
56 

57 
60 

67 


$64 
66 
67 

68 
72 

80 


$109 
111 
112 

113 
117 

126 


$133 
135 
136 

138 
144 

156 


$142 
146 
146 

149 
155 

168 


$160 
163 
164 

167 
174 

188 


$189 
193 
194 

198 
207 

224 


$222 
2C6 
227 

231 
,°43 

264 



The above figures are based on the same prices for repaving, labor, brick- 
layers, cement and sand, as given in the table for conduit, and upon the 
following unit prices: 

Brick work including labor and material .... $12.50 per cu. yd. 

Concrete tops and bottoms $7 50 per cu' yd 

Back water gates '. | 6 .50 each! 

Sewer grates 30 cents each. 

Sewer connections $12.50 each. 

Sewer permits m $5.50 each. 

Manhole frames and covers * $15 *00 each' 

12 



318 



UNDERGROUND CONDUITS. 



Grouping* of Ducts in Iflanholes. 

H. W. Buck in Electric Club Journal, April, 1904. 

Attention is called to the grouping of ducts and construction of manholes. 
Ordinarily ducts are bunched together and brought out at the center of 
the manhole, as shown in Fig. 12. Here the cables divide, half passing on 
one side and half on the other side of the manhole, being racked on the 
manhole walls. This design is objectionable for a number of reasons. 




» 



-N>^>\1 ft^fa 



E2S 



Plan 



Section 



Fig. 12. Ordinary Type of Manhole. 



First, it exposes every cable in the conduit to damage from short-circuit 
at the points A- A, where they are in close proximity to each other. 
Secondly, it necessitates bending every cable sharply at points A and B 
in every manhole, which tends to crack the insulation and cause trouble. 
Most break-downs in underground work do occur at these points. Another 
objection to this form of conduit construction is from the standpoint of 
heating. The cables in the inner ducts, if heavily loaded, will rise to a 




Section 1ULJ Plan 

Fig. 13. Improved Form of Manhole Construction. 



high temperature, for there is no way for the heat to get away by con- 
duction. The inner ducts are surrounded by chambers containing still air, 
which constitute the best possible insulator of heat. 

Ducts should never be grouped more than two in width, so that every 
duct will have an outlet for heat conduction through the surrounding 
earth. A much better form of construction is shown in Fig. 13. Here the 
ducts are grouped only two in width, and the conduit enters the manhole 
at the side, so that the cables can pass straight through on the side 



UNDERGROUND CABLES. 



319 



without bending. A further step in design leads to the arrangement shown 
in Fig. 14. Here the ducts are still laid in one trench but the ducts are 
placed in four separate groups, spaced apart by concrete, as shown. The 




Section 



Plan 



Fig. 14. Manhole Construction Adopted by Niagara Falls Power Company. 

manholes are built with a vertical division wall through the center and 
two entrance holes. Removable soapstone shelves divide the groups of 
cables horizontally, so that not more than one-quarter' of the number of 




Section Plan 

Fig. 15. Manhole Construction of Shallow Trenches. 



cables in the conduit can be damaged by short-circuit at any time. In 
this design the cables also run straight through the manhole without bend- 
ing. 

In places where rock is near the surface of the ground the construction 
shown in Fig. 15 is adopted. 

uarDEitoROuxn cjabmjs. 

Cables are placed underground in several different ways, chief among 
which are the " solid " and " drawing in" systems, as noted on page 301. 
One type of the solid systems is that in which the conductors, properly 
insulated, lead covered and protected by armor, are laid directly in the 
earth, a plan that has been widely adopted in Europe. 

The "Drawinff In " Plan is the one now most generally adopted 
in this country. This plan utilizes .the manholes and conduits just 
described. The cables are drawn into the ducts from manhole to manhole 
by means of a rope that has been previously drawn through the duct by a 
process termed "rodding." Rodding consists of screwing one rod on to 
another in the manhole and pushing them through the duct until the 
further end is reached. The rope is attached to the last rod and the rods 
are withdrawn from the ducts bringing the rope with them. Sometimes in 
place of rods a stiff steel wire is pushed through the ducts. The rope is 



320 UNDERGROUND CONDUITS. 

attached to the cable by a mechanical device which securely grips the end 
of the cable. 

Various means of drawing the cables into the ducts are availed of, 
depending somewhat on the size of the cable and the length of the run; 
haud power, man power with windlass, horses, electric motors and gasoline 
engines being thus employed. 

Xjpen of" Underground Cables. — The type of cable employed for 
underground service varies largely with the requirements. Virtually all 
underground cables are lead covered to prevent injury to the insulation by 
moisture, gases, etc. For telephone purposes, lead covered, dry paper, 
insulated cables are universally used, to obtain low static capacity. (See 
pages 180 and 188.) For telegraph purposes rubber insulation (see page 229) 
and oil saturated cotton or paper are utilized, as in the telegraph service ; 
static capacity is not of so much importance, but still cannot always be 
disregarded, especially in high speed telegraph signaling. The conductor 
commonly used in underground telegraph cable is No. 14 B. & S. copper, 
having a conductivity of 98 per cent. In the case of cotton fiber or paper 
cable, each conductor is insulated to six thirty-seconds (&) of an inch 
outside diameter. The insulating material is thoroughly dried and then 
saturated with an insulating oil or compound. 

JFor Electric JLig-ht and Power purposes rubber, paper and 
varnished cambric insulation are largely used. (See pp. 174 and 180.) Owing 
to its high cost, rubber cables are not now in as high demand as formerly, 
especially as oil saturated paper cables appear to be quite as durable, 
efficient and reliable as rubber insulation for high potential work. 

It was formerly the practice to place as many as six lead covered electric 
light cables in one duct, but experience demonstrated that this was not 
advisable owing to the difficulty in withdrawing when necessary one or 
more cables from the duct without injury to the remaining cables. A burn- 
out in one cable also frequently injured adjoining cables in the duct. 
Present practice favors having only one cable in each duct, although there 
may be several conductors within the lead covering. (See page 185.) 

To prevent burning of light and power cables due to short circuits in the 
manholes and other places where the cables are bunched, the cables are 
frequently covered with asbestos strips about 3 inches wide and T % inch 
thick, well impregnated with a solution of silicate of soda which soon 
hardens over the lead. The lead covers of cables carrying alternating 
currents of high amperage and low E. M. F. should be bonded or carefully 
insulated in the manholes to prevent sparking and possible consequent 
damage, due to induced currents in the lead cover of the cables. 

All lead covered cables used on high potential circuits should be pro- 
tected from damage by static discharge by flared ends or bells, that is, by 
enlargement of the lead sheath to fully twice the diameter of the lead over 
the cable, for a distance of about a foot. The bell should then be filled 
with some good insulating material like Chatterton Compound, the con- 
ductor ends, in case of multiple conductor cable, being carefully separated. 

Cable Heads. — To prevent the entrance of moisture to the ends of 
telegraph and telephone paper cables the conductors of a short length 
(about two feet) of rubber covered cable are spliced to those of the paper 
cable. These splices are then insulated. A lead sleeve is passed over the 
rubber insulated conductors and the lead casing of the paper cable to which 
it is then soldered. The outer terminal of the rubber cable is led into a 
metal box or head to which the lead sleeve is soldered. The free conductors 
are solidly connected to insulated binding posts on the inside of the box, 
which binding posts extend to the outside of the head, thus giving access 
to the conductors externally. The sleeve and box are then filled with a 
melted rubber compound, the temperature of which must be below that at 
which the rubber insulation will soften ; otherwise the rubber will be 
seriously damaged. 

Bells for Cable End*. — AH lead-covered cable ends should be pro- 
tected from damage by static discharge by flared ends or bells, that is, by 
enlargment of the lead sheath to fully twice the diameter of the lead over 
the cable, for a distance of about a foot. Lead or brass cable heads or 
bells are much used on the ends of high potential underground cables. 
This bell should then be filled with some good insulating material like 
Chatterton Compound, the conductor ends, in case of multiple conductor 
cables, being carefully separated and arranged 



CABLE TESTING. 

Revised by Wm. Mayer, Jr. 

Cables — Underground and Submarine. 

The majority of the methods of tests and measurements given herein are 
applicable to aerial, underground, and submarine cables. 

Insulation Resistance. 

Direct Deflection Method, with Mirror Galvanometer. — 

This method, Fig. 1, is generally used in this country in underground and 
submarine work. 




CABLE 



Fig. 1. 
a and b z=. leads. 

G = galvanometer, Thomson or D'Arsonval, mirror type. 
S = shunts for G, usually X, T fo, T ^ . 
B =z battery, 20, 50, or 100 chloride silver cells. 
R z=. resistance box of megohm or more. 
BK = battery reversing key. 
SK=: short-circuit key for G. 
First connect a to lower contact point of SK, and take constant of G, 
using T fo v shunt, and small number of cells, say 5 (depending upon the sen- 
sitiveness of G), with standard resistance B only in circuit, b being discon- 
nected as shown. If 5 cells are used in taking constant, and 100 cells are 
to be used for test, 

G deflec. X shunt X R X 20 , 

Constant _-= 1>0 oo,000 = me g° hms ' 

After obtaining the constant, measure insulation resistance of lead b, by 
joining it instead of SK to a, disconnecting the far end of b from the cable. 
The result should be infinity ; but if not, deduct this deflection from the 
deflection to be obtained in testing the cable proper. Now connect the far 
end of b to the conductor of the cable, the far terminal of latter being free. 
Then open SK carefully, and observe if there are any earth currents from 
the cable. If any, note deflection due to the same, and deduct from bat- 
tery reading if in the same direction, or add to it if in opposite direction. 
Short-circuit G with SK, and close one knob of BK, using, say, the T £<j shunt. 
After a few seconds open SK; if spot goes off the scale, use a higher shunt. 
If deflection is low, use a lower shunt. After one minute's electrification, 
note the deflection. The result may be worked out from this reading, but 
the current should be kept on for three or five minutes longer, and readings 
taken at end of each minute. The deflection should decrease gradually. 
At the end of the last minute of test, open BK, and allow the cable to 

321 



322 



CABLE TESTING. 



discharge fully. Then close SK and press the other knob of BK, revers- 
ing the battery. After a few moments, open SK, and take readings of deflec- 
tions as before. 

The insulation resistance in megohms = — ^ =- , 

a X *j 

where d is the deflection at a given time, and S is the shunt used. If no 
constant 



shunt is used, x = - 



d 



Note that in the above constant, the ordinary constant is multiplied by 20 
for the reason that the battery is increased 20-fold, or 5 :: 100. In case the 
same battery is used for testing as for obtaining the constant, then 



constant = 



G deflec. X S X R 
1,000,000 



Insulating* Cable Ends for Tests. — Much care must be employed 
in order to insure accurate results in measuring insulation resistance. The 
ends should be well cleaned and thoroughly dried. For this purpose they 
are sometimes immersed in boiling paraffin for a few seconds ; or the 
ends may be dried by the careful application of heat from an alcohol lamp. 

If there be no earth currents, the readings with opposite poles of battery 
to the cable should not vary appreciably at any given minute. Pronounced 
variation between the readings at given times and unsteady deflections indi- 
cate defective cable. 

Insulation Resistance by Method of I*oss of Charge. 

The insulation resistance of a cable or other conductor having considera- 
ble capacity may be measured by its loss of charge. Let one end of the 
conductor be insulated, and the other end attached to an electrometer, in 
the manner shown in Fig. 2. 




^SH'ltt ) 



Fig. 2. 

Let R — Insulation resistance in megohms per mile. 
G'= Capacity in microfarads per mile. 
E = potential of cable as charged, 
e := potential of cable after a certain time. 
Depress one knob of key K, and throw key K* to the right, and charge the 
cable for one minute; then throw key K 7 to the left, thus connecting the 
cable to the electrometer. Note the deflection E. Noting the movement of 
the 6pot for one minute, take reading e at end of minute, then 



R- 



2C.06 
Clog- 



If an electrometer is not conveniently at hand, use a reflecting galvanom- 
eter, and after charging cable as before, take an instantaneous discharge, 
noting deflection E due thereto. Recharge cable as before, then open K' 
and at end of one minute, the galvanometer having been disconnected from 
cable in the meantime, take another discharge-reading of cable, and apply 



CABLES. 



323 



the same formula as before. If a condenser of low capacity be inserted be- 
tween K' and the galvanometer, the latter need not be disconnected. The 
advantage of the use'of the electrometer is that the actual loss of potential 
of the cable may be observed as it progresses. 

Testing- Joint* of Cables by Clark's Method. 

In the figure (Fig. 3) the letters refer to the parts as follows : 






=~B 




Fig. 3. 

G is a high-resistance mirror galvanometer. 

S is the shunt. 

K, is the short-circuit key. It may be on the shunt box or separate. 

K lt is a reversing key. 

K ltt is a discharge key. 

B the battery, usually 100 cells chloride of silver. 

C is a ^ microfarad standard condenser. 

The joint to be tested is placed in a well-insulated trough, nearly filled 
with salt water. A copper plate attached to the lead wire is placed in the 
water to ensure a good connection with the liquid. The connections are 
made as shown in the figure, one end of the cable being free. To make test 
close K /n for a half minute; then release it (first depressing one knob of 
key K„), thereby discharging the condenser C, through the galvanometer, 
and note the deflection, if any. A perfect piece of cable of the same length 
as the joint is then placed in the vessel, and if the results with the joint are 
practically equal to those obtained with the perfect cable, the joint is passed. 
When the deflection is very low, it is evident that the joint is sound, and it 
may then be considered unnecessary to compare it with the piece of cable. 
It is very important that the trough and apparatus be thoroughly insulated. 

Electrometer Method. — This method possesses the advantage that 
it dispenses with a condenser, and thereby avoids possible misleading re- 
sults due to electric absorption by that instrument. The connections for 
the electrometer test are shown in the accompanying figure (Fig. 4). 




ELECTROMETER 



Fig. 4. 

B is a battery of about 10 cells. 
B 2 is a battery of 100 or more cells. 



324 



CABLE TESTING. 



As in the preceding test, it is here highly essential that the insulation of 
the trough should be practically perfect, or at least known, so that if not 
perfect, proper deductions may be made for deflections due to it alone. 

To test the insulation of the trough, depress .AT,, and close switch S. This 
charges the quadrants of the electrometer, and produces a steady deflection 
of its needle, and shows the potential due to the small battery B. Now 
open switch S f still keeping K, closed, and watch the deflection of needl6 
for about two minutes. If the insulation of the trough is not perfect, there 
will be a circuit, so to speak, from the earth at the trough to the earth 
shown in the tigure, and a fall in the deflection will be the result. If, how- 
ever, the drop of potential is not more than is indicated by a fall of two or 
three divisions, the insulation of the trough will suffice. The electrometer 
is discharged by closing switch S, which short-circuits the quadrants, K / 
being open at this time. The joint is now connected as in the figure. 
Switch S is opened, and key K„ depressed, thus charging the joint with the 
large battery B,. This produces a quick throw of the needle, due to the 
charging of the joint. Next, keeping K lt closed, discharge the electrometer 
by closing switch S for a moment. The switch is then opened, and if the 
joint is imperfect as to its insulation, the deflection will rise as the elec- 
tricity accumulates in the trough. The deflections are recorded after one 
and two minutes, and are compared, as in the previous test, with a piece of 
perfect cable. The results obtained with the joint should not greatly ex- 
ceed those with the cable proper. 

Capacity. 

Capacity tests are usually made by the aid of standard condensers. Con- 
densers, or sections of the plates of condensers, may be arranged in parallel 
or in series (cascade). 

Arrangement of Condensers — Parallel. — Join like terminals 
of the condensers together, as in the figure ; then the joint capacity of the 
condensers is equal to the sum of the respective capacities. 

Capacity, C= c -{- c, -f c„ + c,„. 




Fig. 5. 
Condensers in Series or Cascade. —Join the terminals, as in 
Fig. 6. The total capacity of the condensers as thus arranged is equal to 
the reciprocal of the sum of the reciprocals of the several capacities, or 

1 
Capacity in series : 



1+ 



-+^ + 



1 



tiiiiii 



c> — c,; 



-+ 



Fig. 6. 
condensers are now constructed so that these two methods of arranging 
the plates of a condenser may conveniently be combined in one condenser, 
thereby obtaining a much wider range of capacities. 



CABLES. 



325 



Vesting- Capacity l*y IMrec* Dischargee. — It is frequently de- 
sirable to know the capacity of a condenser, a wire, or a cable. This may 
be ascertained by the aid of a standard condenser, a trigger key, and an 
astatic or ballistic galvanometer. First, obtain a constant. This is done by 
noting the deflection d, due to the discharge of the standard condenser after 
a charge of, say, 10 seconds from a given E.M.F. Then discharge the other 
condenser, wire, or cable through the galvanometer after 10 seconds charge, 
and note the deflection d'. The capacity c' of the latter is then 

c being the capacity of the standard condenser. 

Capacity l>y Thomson's method. — This method is used with 
accurate results in testing the capacity of long cables. In the figure (Fig. 7) 



£jp mth|||| — l^QyJ^* 






CABLE C, 




Fig. 7. 

B = battery, say 10 chloride silver cells. 

R — adjustable resistance. 

Rj— fixed resistance. 

G=z galvanometer. 

C =. standard condenser. 

1,2, 3, 4,5, keys. 

To test, close key 1, thus connecting the battery B, through the resist- 
ances R, R n to earth. Then 

V: V,r. R-.R, 
where Fand V, = the potentials at the junctions of the battery withi? R r 

Next close keys 2 and 3 simultaneously for, say 5 minutes, thereby char- 
ging the condenser to potential V, and the cable to potential V 

Let Cbe the capacity in microfarads of the condenser, and C, capacity of 
cable, and let Q and Q, be their respective charges when the keys were 
closed. Then Q : Q, :: VC : V,C r 

Open keys 2 and 3, keeping key 1 closed for say 10 seconds, to allow the 
charges of cable and condenser to mix or neutralize, in which case, if the 
charges are equal, there will be no deflection of the galvanometer when key 
5 is closed. If there is a deflection, it is due to a preponderance of charge 
in Cor C r Change the ratio of R to R„ until no deflection occurs. 

Then, VC— V, C, 

or V : V :: C : C . 

But we found V. : V : : r' : & 

or Rs'.R.iC.C,. 



and 



Cv= w C microfarads. 



326 



CABLE TESTING. 



Capacity t>y Oott's Method. — Fig. 8 shows the connections for 
testing the insulation of a cable by this method, which is considered some- 
what better than Kelvin's, as it does not necessarily require a well insulated 
battery. 

First adjust the resistances R and R t to the proportions of C x to C, as 
nearly as may be, by moving the slider S. Depress K for five seconds, 
which will charge both cable and condenser. At the end of the time, de- 
press k and observe if there is any deflection of the galvanometer G. If 
there be any such deflection, open A; again, let up the key K, and short- 




Cable c 



Fig. 8. Gott's Method of Cable Testing with Condenser. 



circuit the condenser C x with its plug for a short time, then readjust R and 
R x and repeat the operation until there is no deflection of the galvano- 
meter G\ then 



C :C 1 ::R 1 :R 



and C = ^ C t . 



The best conditions for this test are when R and R x are as high as pos- 
sible, say 10,000 ohms, and C x and C are as nearly equal as possible. 

Testing* Capacities Uy Lord Kelvin's Dead-Beat, Multi- 
cellular Voltmeter. — Suitable for short lengths of cable (See Fig. 9.) 



M V = multicellular voltmeter. 
AC = air condenser. 

B = battery. 

& = switch. 

Q = total charge in condenser and M V, due to battery. 
Ca = capacity of AC. 
C6 = capacity of cable. 

First close switch S on upper point 1 and charge M V and AC to a desired 
potential, V. Next move switch S from point 1 to lower point 2, and note 
the potential V, and M V. 

Then Q = V (C + Ca) = V,(C + Ca + Cb), where r is the capacity of volt- 
meter. Ordinarily C can be neglected, as comparea with the capacities of 
AC and the cable, in which case, by transposition, 

Cb = (V-V,)Ca = F,. 



CABLES. 



327 



Conductors of telephone cables are measured for capacity with the lead 
sheathing of armor and all conductors but the one under test grounded. 




Fig. 9. 



Locating* Breaks in Cables or Overland Wire* by Capa- 
city Tests. —When the capacity per mile or knot of the conductor of a 
cable is known its total capacity up to the break is measured by comparison 

with a standard condenser. Then x = — , , x being distance to fault in miles, 

m 
m' capacity of conductor per mile and m total capacity of conductor from 
the testing station to break. A clear break in the caole or conductor is 
assumed. 

Locating- Crosses in Cables or Aerial Wires. — IProf. Ayr- 
ton Method. — To locate the cross at d (Fig. 10) arrange the connections 




-tvrf 



• Fig. 10. 
as shown. This is virtually a Wheatstone bridge, in which one of the wires, 
n, is one of the arms of same. Adjust r until a (x -\- y) =. br y when r will be 
equal to x + y> if a = b. 

d 




Fig. 11. 



328 CABLE TESTING. 

Next connect the battery to line m instead of to earth, as in Fig- 11, and 
adjust a until ax — by. 

r^ x b 

Then = — = , , ■ 

and as x -f- y = r in the first arrangement, 

v b X r 

hence, x = =— - -. — • 

' b-\- a 

This test may be varied by transposing G and the battery, in Fig. 9, which 
is the old method of making this test. 

Locating* Fault** in Aerial W ires or Cables l>r the loop 
Test. — Two conductors are necessary for this test, or both ends of a cable 
must be available at the testing-point. Also it is assumed there is but one 
defect in the conductor. The resistance of the fault itself is negligible in 
this test. 

Measure the resistance L of the loop by the ordinary Wheatstone bridge. 

Murray Method. — Connect as in Fig. 12, in which a and b are the 
arms of a Wheatstone bridge, and y x are resistances to fault, the conduc- 
tors being joined at J" (in the case of aerial wire, for instance). Close key 
and note the deflection of needle due to E.M.F. of chemical action at fault 
if any. This is called the false zero. 



Fig. 12. 

Now apply the positive or negative pole of the battery, by depressing one 
of the knobs of reversing key K, and balance to the false zero previously 
obtained by varying the resistance in arms a or b. Then, by Wheatstone 
bridge formula, 

ax =z by, 
and l — x-j-y 

y= I —x 

a 4- b 



To ascertain distance in knots or miles from 2 to F, divide x by resistance 
per knot or mile ; to ascertain distance from 1 to F, divide y by resistance 
per knot or mile. 

The foregoing test is varied in the case of comparatively short lengths of 
cable, in the manner shown in Fig. 13, in which the positions of the battery 
and galvanometer are transposed. Otherwise the test and formula are the 
same. It is advisable to reverse the connections of cable or conductors at 2 
and 1, and take the average of results obtained in the different positions. 
In this latter method, battery B should be of low resistance, and well insu- 
lated. 

Best conditions for making test, according to Kempe.— Resistance of b 
should be as high as necessary to give required range of adjustment in a. 



CABLES. 



329 



Resistance of galvanometer should not be more than about five times the 
resistance of the loop. 



CABLE 




Fig. 13. 

Varley Loop Test. — Measure resistance of looped cable or conduc- 
tors as before. Then connect, as shown in Fig. 14, in which r is an adjustable 
resistance. If currents due to fault be present, obtain false zero as before. 
Then close key K, and adjust r for balance. In testing, when earth current 
is present, the best results are obtained when the fault is cleared by the 
negative pole, and just before it begins to polarize. 




Fig. 14. 



Then 



where x is the distance of fault, in ohms, from point 2 of cable proper. 

Then x + by the resistance of the cable or conductor per knot or mile 
gives the distance of fault in knots or miles. 

When the resistance of the "good" wire used to form a loop with the 
defective wire, together with that portion of the defective wire from ./ to F, 
is less than the resistance of the defective wire from the testing station to 
fault, the resistance r must be inserted between point 1 and the good con- 
ductor, the defective wire being connected directly to point 1. The formula 

in this case is x = — - — , x, as before, being the distance to fault in ohms. 

To Localize Fault when Resistance of Conductor is 
Known and a Parallel Good Wire is not Available. — Measure 
by Wheatstone bridge resistance (r) from A to earth through fault F, and 
resistance (r') from A' to earth through fault, Fig. 15. Let R be resistance 
of conductor from A to A', x the actual resistance of conductor from A to 
F and y actual resistance of conductor from A' to F. 

The* x = R + r- r ' 



330 CABLE TESTING. 

and 2/ = 

in ohms, from which the distance in feet or miles may be calculated. 

» R_ £ 

< ~ *< —, > 



Fig. 15. 

Locating- Fault* in Insulated Wires. — The following, so to 
speak, "rule of thumb," or point to point electro-mechanical methods of 
locating faults in unarmored cables, in which the defect is not a pronounced 
one, have been found successful. 

Warren's Method. — The cable should be coiled on two insulated 
drums, one-half on each drum. The surface of the cable between the drums 
is carefully dried. One end of the conductor is connected to a battery which 
is grounded. The other terminal is connected to the insulated quadrants 
of an electrometer, the other pairs of quadrants of which are connected to 
the earth. Both drums being well insulated, no loss of potential is observed 
after three or four minutes. An earth wire is now connected first to one 
and then another of the drums, and the fault will be found on the drum 
which shows the greater fall on the electrometer. The coil is now uncoiled 
from the defective drum to the other drum, and tests are made at intervals 
until the defect is found. 

JF. JTacoo coils the core from a tank to a drum. The battery is con- 
nected between the tank and the conductor, one end of which is free. A 
galvanometer is joined between the tank and drum, which need only be 
partially insulated. The needle shows when the fault has passed to the 
drum, and it can be localized by running the galvanometer lead along the 
insulated wire. 

Copper Resistance, or Conductivity of Cables. 

The copper resistance of the submarine and underground cables used in 
telephony and telegraphy is always tested at the factory, usually by the 
Wheatstone bridge method. In such a case both ends of the cable are ac- 
cessible. When the cable is laid, if the far end is well grounded, the cop- 
per resistance may be measured, either by the Wheatstone bridge method, 
or by a substitution method, as follows: First, note the deflection due to 
copper resistance of conductor. Then substitute an adjustable resistance 
box and vary the resistance in the box until the deflection equals that due 
to cable. This latter resistance is the resistance of the cable. If there are 
earth currents on the cable, take readings of cable resistance with each 
pole of battery. Should there be any difference between the results 
obtained with the respective poles of the battery, the actual resistance 
will, according to F. Jacob, be equal to the harmonic mean of the two 
results, i.e., 

r 4- r 

where R is the actual resistance, r is the resistance with + pole, / is the 
resistance with — pole. 

To measure copper resistance of conductors by the voltmeter, first 
measure the E.M.F., V of testing battery. Then place the voltmeter in 
series with the battery and conductor or instrument to be tested, exactly . 
as a galvanometer would be placed, and note the deflection V in volts. 
It will be less than in the first instance. Unknown resistance x will be 
found by the formula: 

where r is the resistance of the voltmeter coil. 



CABLES. 331 

Tenting 1 Submarine Cable During* manufacture and 
liajing*. 

The Core of the cable, that is, the insulated copper conductor, is 
made, as a rule, in lengths of 2 knots, which are coiled upon wooden drums, 
and are then immersed in water at a temperature of 75° F. for about 24 
hours. The coils are then tested for copper resistance, insulation resis- 
tance, and capacity ; the results of which tests, together with data as to 
length of coils, weight, etc., are entered on suitably prepared blanks. 

After the tests of some of the coils have been made, the jointing up of 
the cable begins, which is followed by the sheathing or armoring. The 
joints are tested after 24 hours immersion in water. During the sheathing 
process, continuous galvanometer or electrometer tests are made of the 
core, to see that no injury befalls the cable during this process. In fact, 
practically continuous tests of the cable for insulation resistance, copper 
resistance, and capacity should be made until the laying of the cable begins. 

During laying, the cable should be tested continuously, and communica- 
tion should be* practically constant between the ship and the shore. An 
arrangement to permit such tests and communication is shown in Fig. 14. 

SHIP 8H0RE 



K 



Fig. 16. 

In this figure, G x is a marine galvanometer, B is a battery of about 100 
cells on ship-board. In the shore station, L is a lever of key K, C is a con- 
denser, G 2 is a galvanometer. Normally key K is open and the cable is 
charged by battery B. If, while the cable is being paid out a defect occurs 
in the insulation, or if the conductor breaks, a noticeable throw of the galva- 
nometer follows, and the ship should be stopped and the cause ascertained. 
By pre-arrangement the lever of shore key K is closed, say every 5 minutes, 
thereby charging the condenser C, which causes a throw of the galvano- 
meters' needles. If the ship or shore fails to get these periodic signals, or 
if they vary as to their strength, it indicates the occurrence of a defect. 
At the end of every hour the ship reverses the battery, which reverses the 
direction of the deflection of the galvanometers. If the ship desires to 
communicate with the shore, the battery is not reversed at the hour, or 
is reversed before the hour. If the shore wishes to speak with the ship, the 
key K is opened and closed several times in succession. In either event 
both connect in their regular telegraphing apparatus for conversation. 

Compound Cables, that is, cables of more than one conductor, have 
their conductors connected in series for these tests. If there is an even 
number of conductors, two of them must be connected in parallel. 

Locating* Faults in Underground Cables. 

To localize a fault in a conductor of a cable, form a loop consisting of the 
defective conductor and a 
good conductor of equal resis- 
tance and length, with battery 
E as shown, Fig. 17. Place 
an ammeter in each leg of 
loop L. If current in leg A 
to fault F is /, and current 
in leg A' to fault is /' ; D being 
length of loop L and x the 
distance from A' to fault F t 

Fig. 17. 




332 



CABLE TESTING. 



then 



/ x 


IL 


77 = 7T and x = 

/' D — x 


I +/' 



The compass method of locating faults in underground cables consists, 
briefly, in sending a constant continuous current of about 10 amperes into 
the cable through the ground, the current first passing into an automatic 
reverser which reverses the direction of the current flow every ten seconds. 
A manhole is then opened near the center of the cable length and a pocket 
compass laid on the lead sheathing of the faulty cable and observed for 
say half a minute. If the ground is further from the source of reversed 
current the compass needle will swing around approximately 180° upon 
every reversal at the end of each ten seconds interval. The manhole is 
immediately closed and another opened, say a mile further away from the 
source of test current, and if no motion of the compass needle occurs, then 
the fault has been passed and another manhole is opened between the two 
first positions, and so on until the fault is finally located in a section be- 
tween two manholes. H. G. Stott, in Trans, A. I. E. E. 



Hig-ti Voltage or Dielectric Vests of Cables or Other 
Apparatus. 



Cables intended for high pressure circuits ranging from 500 to 60,000 
volts or more are usually tested at the factory to ascertain their ability to 

withstand specified voltages. For 
the lower voltages the cables are 
generally tested for three or four 
times the contemplated working 
pressure. For higher voltages the 
cables are usually tested for one and 
a half to twice the working electro- 
motive force. See standardization 
rides of A.I. E. E. The present limit 
for underground power cables is 
about 30,000 volts. The alternat- 
ing electromotive force for these 
tests is supplied by specially de- 
signed step-up transformers, which 
must be of sufficient kw. capacity 
to supply the charging current called 
for by the cable to be tested. The 
charging current varies directly as 
the frequency, directly as the 
E.M.F., and directly as the static 
capacity, and as apparent energy 
(Skinner, Electrical Age, July, 1905) 
is equal to current multiplied by 
E.M.F., the apparent output of the 
transformers required must vary 
directly as the frequency, directly 
as the square of the E.M.F., and 
directly as the static capacity in 
microfarads of the cable or apparatus under test. For example, an under- 
ground cable having a static capacity of one microfarad, and tested at 
20,000 volts, 60 cycles, requires a testing transformer of 150 kilowatt capac- 
ity; tested at 40,000 volts the same cable would require a testing trans- 
former of 600 kilowatt capacity. The testing electromotive force is regulated 
in several ways, for instance, by means of a rheostat in the field of the 
generator, as in Fig. 18, or by employing a number of small transformers 
capable of being connected up, as indicated in Fig. 19, in which the range is 
from 10,000 to 40,000 volts in steps of 10,000 volts. The voltmeter or vol- 




CABLES. 



333 



Supply Mains 




or Spark Gap 



Fig. 19. 



tage indicator may be placed in the primary circuit of the transformer, in 
which case the E.M.F. in testing circuit is calculated by the ratio of primary 
to secondary of the transformer, or the voltmeter may be placed directly in the 
testing circuit. A spark gap in the testing circuit is frequently employed 
across the cable or apparatus under test (Fig. 19), the E.M.F. in this case 
being obtained from a table of voltages of spark lengths in air. (See p. 233.) 
In applying high voltage, say anything above 5000 volts, to a cable or 
to a piece of apparatus for the purpose of testing its insulation, care should 
be taken to build it up gradually to the point required; and for this it is 
best to place a voltmeter across the primary of the testing transformer and 
place needles for a spark gap across the secondary, gauging their points at 
the distance given in the rules of the committee of standards of the 
A.I.E.E. Run the voltage up gradually, reading the voltmeter as the pres- 
sure is built up. until the current jumps the gap, when the indication of the 
voltmeter should be carefully taken. When the test is being made the 
needles should be set about 10*% farther apart, and the pressure obtained 
can be read on the voltmeter direct. Choke coils of many turns, and other 
high resistances should be placed in series with each side of the spark gap 
so as not to cause damage when the gap closes. Water rheostats consisting 
of glass tubes about 3 feet long, J" diameter, and filled with water, make 
good high resistance for this purpose. 



DIRECT-CURRENT DYNAMOS AND MOTORS. 

Revised by Cecil P. Poole. 

KfOTAIIOX. 

Except where other definitions are given, the definitions of the symboli 
used throughout this section are as follows : — 

A =: Area in square inches. 

Ab =: Aggregate area of all brush faces. 

B« =: Magnetic density in armature core body at full load. 

&m = Magnetic density in field magnet core at full load. 

Bj> = Average magnetic density over pole-face at full load. 

Bt = Magnetic density in armature tooth tops at full load. 

Bt'=: Approximate magnetic density in armature tooth tops at full load. 

B< = Magnetic density in armature tooth roots at full load. 

B*' = Approximate magnetic density in armature tooth roots at full load. 

Bt = Magnetic density in armature teeth at a specified point. 

Bt' = Approximate density in armature teeth at a specified point. 

b = Brush-face dimension crosswise of commutator bars. 

y = Average distance between interpolar edges of adjacent pole-faces. 

Da = Diameter of armature core over teeth. 

Dk =: Diameter of commutator barrel. 

Do = Diameter of central hole in armature core. 

Dp m Diameter of pole-face bore. 

Dt = Diameter of circle drawn through narrowest parts of armature core 

teeth. 
d — Diameter of bare round wire, in mils. 
A = Depth or thickness of winding in a magnet coil. 
8 = Air-gap length from pole-face to tops of armature teeth. 
E =. Total E.M.F. generated in an armature. 
Ew == E.M.F. delivered by a dynamo or applied to a motor. 
e r= E.M.F. at terminals of one magnet coil. 
F = Ampere-turns per pole required by complete magnetic circuit at 

full load. 
F = Ampere-turns per pole required by complete magnetic circuit at 

no load. 
Fa = Ampere-turns per pole required by armature core at full load. 
F g = Ampere-turns per pole required by air-gap at full load. 
Fm = Ampere-turns per pole required by magnet core at full load. 
F P = Ampere-turns per pole required by pole-piece or shoe at full load. 
Fr =. Ampere-turns per pole required to balance full-load armature 

reaction. 
F$ = Ampere-turns per pole in series field-winding at full load. 
Fth =. Ampere-turns per pole in shunt field-winding at full load. 
Ft = Ampere-turns per pole required by armature teeth at full load. 
F v =z Ampere-turns per pole required by field-magnet yoke at full load. 
/ = Ampere-turns per inch length of magnetic path at full load : 

Subscripts a, m, p, t and y apply to armature core, magnet core, 

pole-shoe, armature teeth and magnet yoke, respectively. 
G — Girth or perimeter of a complete magnet coil. 
g = Girth or perimeter of form or bobbin on which a magnet coil is 

wound. 
h =z Depth of armature coil slot. 
la — Total armature current. 
I»h ~ Shunt field current. 
Iu> — Current delivered from a dynamo, 
i r= Current in a specified conductor, or coil. 
i a == Current in each armature conductor. 
kch = sin (180 t+p); kch Dp = chord of polar arc. 
kg = a coefficient ; kg 8 = increase of air-gap span due to flux spread. 
kg 2 = a coefficient ; k ff2 8 = increase of air-gap width due to flux spread. 
k* z=. Number of commutator bars between the two to which the termi. 
nals of each armature coil are connected. 
334 



NOTATION. 335 

X« = Length of magnetic path in armature core beneath slots. 

Lf — Length of a specified field-magnet coil parallel to flux path. 

Lm = Length of magnetic path in one field-magnet core. 

L P = Length of magnetic path in one magnet pole-piece or shoe. 

Ly = Length of magnetic path in field-magnet yoke between adjacent 

poles. 
le = Total length of each armature conductor. 
m =2 Number of windings in a multiplex armature winding. 
Ke =. Total number of armature conductors around armature periphery. 
Nk = Number of commutator bars and armature coils 
Nt = Number of armature teeth (and slots). 
rik = Maximum number of commutator bars simultaneously in contact 

with one brush at any instant. 
v — Coefficient of magnetic leakage. 
P A = Total watts lost in armature. 
P' A = Total watts lost in armature exclusive of projecting parts of the 

winding. 
Pb z=. Watts lost at all brush faces. 
Pe = Watts lost by eddy currents. 
Ph z=: Watts lost by hysteresis. 
Pr = Watts lost in entire armature winding alone. 
Pr' r= Watts lost in armature winding exclusive of projecting parts. 
Pa = Watts lost in series field-magnet winding. 
Psh — Watts lost in shunt field-magnet winding. 
P w = Watts of dynamo armature output or motor armature intake. 
p = Number of field-magnet poles. 
q = Number of parallel paths through an armature winding ; 

Note: — In a multiplex winding, q = total paths in all the 
windings. 
R =p Resistance of armature, commutator and brushes, warm. 
Pa = Resistance of armature winding, warm. 
R a ' = Resistance of embedded part of armature winding, warm. 
Rb z=z Effective resistance of all brush-face contacts ; I*Rb = Volts drop 

at brush faces. 
r rr Resistance of a specified conductor or coil in ohms, 
r.p.m. == Revolutions per minute. 
r.p.s. == Revolutions per second. 
5 = Width of one armature coil slot. 

T = Torque in pound-feet. 
T =z Width of one armature tooth at the top. 

t ■=. Width of one armature tooth at the narrowest part, except in 

equation 32 and Table V. 
t =z Number of turns per armature coil ; only in equation 32 and 

Table V. 
A = Temperature rise of armature, Fahrenheit degrees. 
6k rr Temperature rise of commutator, Fahrenheit degrees. 
0/ = Temperature rise of field winding, Fahrenheit degrees. 
t = Width of one armature tooth at a specified point. 

$ z=z Magnetic flux passing from one pole-face to armature at full load. 
$m = Magnetic flux in magnet core at full load. 
<P = Magnetic flux in one air-gap at no load. 
$m =z Magnetic flux in magnet core at no load. 
* r= Polar span -^- pole-pitch = proportion of armature circumference 

covered by all pole-faces. 
v = Volume of iron or steel, cubic inches. 
v a = Volume of iron or steel in armature core body. 
vt = Volume of iron or steel in armature teeth. 
Wa — Gross length of armature core, between end plates. 
Wa = Net measurement of armature core iron parallel to shaft = 0.9 X 

(Wa — ventilating ducts). 
Wh = Width of commutator barrel, parallel to shaft. 
Wp = Width of pole-face parallel to shaft. 

Note. — All dimensions are in inches, except wire diameters. 



336 



DYNAMOS AND MOTORS. 



:fu]¥I»a]!i:e]¥Ta:ls. 

One volt is generated in anelectrical conductor by the " cutting" of 
100,000,000 maxwells per second. 

One volt is generated in a looped or coiled conductor by a uniform varia- 
tion of magnetic flux threaded through the loop or coil when the average 
rate of change is 100,000,000 maxwells per second. 

Consequently, the E.M.F. generated in any direct-current armature is 



E = $ A r c £r.p.s. 10" 8 



(1) 



Dynamos are 

Series-wound, to deliver constant current, 
Shunt-wound, to deliver approximately constant E.M.F. , 
Compound-wound, to deliver strictly constant E.M.F. at some point in 
the work circuit. 



The entire field winding of a series-wound machine is in series with its 
armature, and therefore carries the full current ; an auxiliary regulator is 
required to maintain the current constant under varying loads. 

The field winding of a shunt-wound dynamo is connected to its brushes in 
series with an adjustable resistance (rheostat) ; as the load increases, the 
drop in the armature winding and connections increases and the available 
E.M.F. at the terminals is thereby reduced, necessitating adjustment of 
the rheostat to strengthen the field excitation and bring the terminal 
E.M.F. up to normal. 

A compound-wound dynamo is provided with a shunt field winding con- 
nected either to its brushes or to its main terminals, in series with a rheostat, 
and an auxiliary winding of relatively large conductor connected in series 
with the armature. The shunt winding excites the machine to normal vol- 
tage at no load ; the application of a load causes the field excitation to be 
strengthened by reason of the current flowing in the series winding. The 
series winding is proportioned to increase the field strength in response to 
any increase in load, to such an extent as to maintain the proper E.M.F. at 
a predetermined point in the work circuit. The rheostat in the shunt field 
circuit is for the purpose of adjusting the no-load E.M.F. within practical 
limits. 

The relation between field excitation and generated E.M.F. is shown by 
the "magnetization characteristic" curve. See Fig. 1. The early part 

of the curve is practically a straight 
line because the iron or steel in the 
magnetic circuit has such high perme- 
ability at low degrees of magnetization 
that the flux is almost directly pro- 
portional to the exciting force. As 
the iron or steel approaches sat- 
uration, the permeability decreases 
rapidly and a given increase in excita- 
tion will not produce an increase in 
flux equal to the increase produced 
by the last previous equal increase 
in excitation ; hence the sharp bend 
in the curve. In constant-potential 
machines, the magnetic circuit should 
be proportioned so that at no load 
the characteristic curve has com- 
menced to bend sharply, as at the intersection of the lines a and c in the 
diagram ; the lines b and d indicate respectively the total internal E.M.F. 
generated at full load and the ampere-turns required to produce it, and their 
intersection establishes the point on the magnetization curve corresponding 
to full load. 





■^ . ■ 


e < 
o s 


^ 




m < 

II 


e / 






»- H 
















11 


1 e 




d 



AJHPERE -TURN8 ON FIELD 
OR CURRENT IN FIELDS 



Fi«. 1. Magnetization Curve. 



DYNAMO CHARACTERISTICS. 



337 



VO UTAGe 



External Characteristic — This curve is a curve of results, m 
which the dynamo is excited from its own current, and with the speed con- 
stant, the terminal voltage is read for different values of load. 

The curves for series, shunt, and compound wound machines all dilter. 

The observations are best plotted in a curve in which the ordinates repre- 
sent volt values, and abscissae amperes of load. 

Series dynamo. In a series machine all the current flowing magnetizes 
the field, the volts increase with the current, and if fully developed the 
curve is somewhat like the magnetization curve, being always below it, 
however, due to the loss of pressure in overcoming internal resistance and 
armature reactions. The diagram, Fig. 2 (armature reaction being neg- 
lected), is a sample of the external characteristic of a series dynamo. 

To construct this curve from an existing 
machine, the curve of terminal voltage can 
be taken from the machine itself by driving 
its armature at a constant speed, and varying 
the load in amperes. 

The curve " drop due to internal resistance," 
sometimes called the " loss line," can be con- 
structed by learning the internal resistance 
of the machine, and computing one or more 
values by ohm's law, and drawing the straight 
line through these points, as shown. 

The curve of total voltage is then con- 
structed by adding together the ordinates of 
the "terminal voltage" and "drop due to 
internal resistance." 

A very good sample of curve from a modern 
series machine is to be found in the following 
description of the Brush arc dynamo. 

Fig. 3 is a characteristic curve of the new Brush 125-lt. Arc Dynamo 




AMPERES LOAD 



Fig. 2. External Charac- 
teristic of Series Dynamo. 



7000 
6832 
















^ ' 


"X 












6500 








_/ 


S 












\ 










6000 








1 














\ 
















t 
















\ 








5500 






/ 
































/ 


























































4500 
































4000 




































1 


























«o 3500 
>3000 


































/ 






























/ 




























2500 




/ 




























2000 




/ 


























































1500 


/ 






CHARACTERISTIC CURVE 

SPEED-B00 REV. PER MIN. 










1000 


/ 












































500 



































/ 































4 5 7 8 9 10 11 12 13 14 
AMPERES 



Fig. 3. Characteristic curve of Brush 125-Light Arc 
Dynamo without Regulator, 



338 



DYNAMOS AND MOTORS. 



machine without any regulator. The readings were all taken at the spark- 
less position of commutation. This curve is remarkable from the fact that 
after we get over the bend, the curve is almost perpendicular, and is prob- 
ably the nearest approach to a constant current machine ever attained. 
By winding more wire on the armature the machine could have been made 
to deliver a constant current of 9.6 amperes at all loads, without shunting 













































100 


















































































m 










































. so 


















































































\n 






/ 








































t 


































"'GO 




/ 










ELECTRICAL EFFICIENCY 

AMPERES 9.6 

8PEEO 600 R.P.M. 














/ 




















50 
































































40 










































8S 











































2000 3000 4000 5000 6000 
VOLTS 



Fig. 4. Electrical Efficiency Curve of 
Brush 125-Light Arc Dynamo. 







































































































































































































































































































































J 


t 






































/ 










COMMERCIAL 


IFFICIENCY 
5 9.6 












/ 












AMPERE 
























SPEED 600 R.P.M. 



































































































































3000 4000 
VOLT8 



Pro. 5. Commercial Efficiency Curve of 
Brush 125-Light Arc Dynamo. 



any of the current from the field ; but this would have increased the internal 
resistance, and also have made the machine much less efficient at light 
loads. By the present method of regulation the 1*R loss at one-quarter load 
is reduced from 4,018 to 3,367 watts, the gain being almost one electrical 
horse-power. 

Fig. 4 is a curve of the electrical efficiency. It will be noticed that this 
at full load reaches 94 per cent, which is accounted for by the liberal allow- 
ance of iron in the armature, thus reducing the reluctance of the magnetic 
circuit, and by the large size of the wire used on both field and armature. 

Fig. 5 is a curve of the commercial efficiency. At full load this is Dver 
90 per cent, and approaches very closely the efficiency of incandescent 
dynamos of equal capacity, but the most noteworthy point is the high effi- 
ciency shown at one-quarter load. 

Fig. 6 is a curve of the machine separately excited, with no current in the 
armature. The ordinates are the volts at the armature terminals, and the 
abscissae the amperes in the field. This is in reality a permeability curve of 
the magnetic circuit. By a comparison of the voltage shown here when 



DYNAMO CHARACTERISTICS. 



339 



there are nine amperes in the field, -with that of the machine when deliver- 
ing current, can be seen the enormous armature reaction. The curve also 



































9000 






























































































































































1000 
































































6000 
































































5000 


































] 






























4000 
































































8000 


















































E. M. F. 










































































1000 
500 
































1 































Fig. 



1&345678 9 10 11 12 13 14 M 

AMPEBE8 

6. Permeability Curve of Magnetic Circuit 
of Brush 125-Light Arc Dynamo. 



indicates a new departure in arc dynamo design, namely, that the magnetic 
circuit is not worked at nearly as high a point of saturation as in the old 
types. 

Shunt dynamo. The shunt dynamo has, besides an external characteristic, 
shown below, an internal characteristic. The first is developed from the 
volts read while the load in amperes is being added, the armature revolu- 
tions being kept constant (See Fig. 7.) 

Adding load to a shunt dynamo means simply reducing the resistance of 
the external circuit. With all shunt machines there is a point of external 
resistance, as at n, beyond which, if the resistance is further reduced, the 
volts will drop away abruptly, and finally reach zero at a short circuit. 




/ft 



Fig. 7. External Characteristic Fig. 8. Internal Character- 

of Shunt-wound Dynamo. istic of Shunt Dynamo. 

The internal characteristic, Fig. 8, or, more correctly, curve of magnetiza- 
tion, of a shunt dynamo, is plotted on the same scale as those previously 
described, from the volts at the field terminals and the amperes flowing in 
the field winding. 



340 



DYNAMOS AND MOTORS. 



The resistance line o a only applies to the point a on the curve, and the 
resistance value a b for that point is determined by ohms law, or as fol- 
lows : As the curve of magnetization is determined from the reading of 

volts plotted vertically and amperes horizontally, and asr=yOrr= — r 

and ^-r = tang aob, therefore the resistance at any point on the curve will 

o b 
be the tangent of the angle made by joining that point to the origin o. 

Compound dynamo. As the compound dynamo is a combination of the 
series and shunt machines, the characteristics of both may be obtained 

from it. 

The external characteristic is of con- 
siderable importance where more than 
one dynamo is to be connected to the 
same circuit, or when close regulation 
is necessary. 

Fig. 9 is a sample curve from a com- 
pound-wound dynamo, where the in- 
crease of magnetization of the fields 
due to the series coils and load causes 
amperes the terminal voltage to rise as the load 

._, _ ~, . . 4. « A „„„ is increased. This is commonly done 

Fig. 9. Characteristic of Over- tQ make for d in feeder / to the 

compounded Compound - wound cen tre of distribution. It is impossi- 

Dynamo. kl e m ordinary commercial dynamos 

to make this curve closely approach a straight line, and the author has 
found it difficult for good makes to approach a straight line of regulation 
nearer than 1£ per cent either side of it for the extreme variation. 

Curve of IWtagrnetic ^Distribution. — This curve is constructed 
from existing dynamos to show the distribution of the field about the pole- 
pieces ; it can be plotted on the regular rectangular co-ordinate plan, or on 
the polar co-ordinate. 

The following cuts illustrate the commonest methods of getting the data 
for the curve. With the dynamo running at the speed and load desired, the 





Fig. 11. 

pilot brush, a, in Fig. 10, or the two brushes, a and b, in Fig. 11, 
is started at the brush x, and "moving a distance of one segment at a time, 
the difference in volts between the brush x and the location of the pilot 
brush, a, is read on the voltmeter. 

Where the one pilot brush is used, the total difference between that and 
the origin is read ; while with two brushes, as a and 6, which are commonly 
fastened to a handle in such a manner as to be the width of a segment apart, 
just the difference between the two adjacent segments is read, and the total 
difference is determined by adding the individual differences together. 



ARMATURES. 341 



ARMATURE!. 

Direct-current armatures are divided into two general forms, — drum arma- 
tures, in which the conductors are placed wholly on the surface or ends of 
a cylindrical core of iron ; and ring armatures, in which the conductors are 
wound on an iron core of ring form, the conductors being wound on the out- 
side of the ring and threaded through its interior. 

Another form used somewhat abroad is the disk armature, in which the 
conductors are arranged in disk form, the plane of which is perpendicular to 
the shaft, and without iron core, as the disk revolves in a narrow slot be- 
tween the pole-pieces. 

Armatures of the slotted or toothed core type are almost exclusively em- 
ployed now. The coils are set into the slots, with the results that eddy cur- 
rents in the conductors are prevented and the conductors are positively 
driven by the core teeth. The cores are built up of sheet steel disks in small 
sizes, annular sheets in medium sizes, and staggered circular segments in 
large sizes ; the steel is from 15 to 25 mils thick and the sheets are clamped 
firmly together by end-plates. In order to prevent eddy currents in the 
core, the disks or sheets are either coated with an insulating varnish or 
separated by tissue paper pasted over the entire surface of one side of each 
disk or sheet. 

The toothed armature has the following advantages and disadvantages as 
compared with the smooth body: 

Advantages. 

1. The reluctance of air-gap is minimum. 

2. The conductors are protected from injury. 

3. The conductors cannot slip along the core by action of the electrody- 
namic force. 

• 4. Eddy currents in the conductors are almost entirely obviated. 

5. If the teeth are practically saturated by the fiefd magnetism, the> 
oppose the shifting of the lines by armature reaction. 

Disadvantages. 

1. More expensive. 

2. The teeth tend to generate eddy currents in the pole-pieces. 

3. Self-induction of the armature is increased. 

If the slots can be made less in width than twice the air-gap, so that the 
lines spread and become nearly uniform over the pole-faces, but little 
effect will be felt from eddy currents induced in the pole-faces. When it is 
not possible to make such narrow slots, pole-pieces must be laminated in 
the same plane as the disks of the armature core, or the gap must be con- 
siderably increased. 

Hysteresis in the armature core can be avoided to a great extent by using 
the best soft sheet iron or mild steel, which must be annealed to the softest 
point by heating to a red heat and cooling very slowly. Disks are always 
punched, and are somewhat hardened in the process ; annealing will 
entirely remove the hardness, and any burrs that may have been raised. 

Disks should be punched to size so carefully as to need no filing or trueing 
up after being assembled. Turning down the surface of a smooth-body 
armature core burrs the disks together, and is apt to cause dangerous 
heating in the core when finished. Light filing is all that is permissible for 
truing up such a surface. Slotted cores should be filed as little as possible, 
and can sometimes be driven true with a suitable mandrel. 

Armature shafts must be very strong and stiff, to avoid trouble from the 
magnetic pull should the core be out of center. They are made of machin- 
ery steel, and have shoulders to prevent too much endwise play. 

Core Insulation. — A great variety of material is used for insulating 
the core, including asbestos, which is usually put next to the core to prevent 
damage from heating of that part, oiled or varnished paper, linen, and silk ; 
press board ; mica and micanite. For the slots of slotted cores the insula- 
tion is frequently made into tubes that will slide into the slots, and the con- 
ductors are then threaded through. Special care must be taken at corners 
and at turns, for the insulation is often cut at such points. 



342 



DYNAMOS AND MOTORS. 



Armature Winding-*. 

For all small dynamos, and in many of considerable 6ize, the winding is 
of double cotton-covered wire. Where the required carrying capacity is 
more than that of a No. 8 wire, B. & S. gauge, the conductor should be 
stranded for smooth-core armatures. In large dynamos, rectangular cop- 
per bars, cables of twisted copper, and in some cases large cable compressed 
into rectangular shape, are more commonly used. If the copper bars are 
too wide, or wide enough so that one edge of the bar enters the field percep- 
tibly before the remaining parts of the bar, eddy currents are induced in it ; 
such bars are therefore made quite narrow, and it is common to slope the 
pole-face a trifle, so that the bars may enter the field gradually. 

Method* or arrangement of windings are of a most complex nature, and 
only the most general in use will be described here, and these only in theory ; 
Parshall & Hobart have described about all the possible combinations ; 
S. P. Thompson, Hawkins &Wallis, and others have also written quite fully 
on the subject. 



Ring- or Gramme Winding**. 

There are two fundamental types of armature winding : ring and drum. 
In a ring-wound armature, the core is necessarily annular, the wire being 
wound through the core as well as along the exterior, as indicated in Figs. 
12 to 15. This form of winding is now used only in arc-light dynamos and 
very small motors. 

The simplest form of ring winding is the two-circuit single winding, where 
a continuous conductor is wound about the ring, and taps taken off to the 
commutator at regular intervals. 




Fig. 12. 



Fig. 13. 



Fig. 14. 



The first variation on this will be the multi-circuit single winding, used 
where there are more than one pair of poles. Fig. 13 shows the four-circuit 
single winding. 

Where it is advisable to reduce the number of brushes in use, the multi- 
circuit winding can be cross-connected ; that is, those parts of the winding 
occupying similar positions in the various fields are connected in parallel to 
the same commutator bar. Fig. 14 shows one of the simplest forms of cross- 
connected armatures. 

Where, from the shape of the frame, the magnetic circuits are somewhat 
unequal, the winding shown in Fig. 15 will average up the unequal induc- 
tion values, and prevent sparking to some extent. It also halves the 
number of commutator segments ; that is, there are two coils connected 



ARMATURES. 



343 



to each segment instead of one, as in the previously mentioned windings. 
If Nk = number of coils, and p = number of poles, each coil is connected 



(?*»)* 



in advance of it. 



across to a coil 

\ p i 
Two-Circuit Winding's for Multipolar Field's. —This is an 
important class of windings, and, as it has but two circuits irrespective of 
the number of poles, has the advantage over the multiple-circuit windings 

2 
that it needs but — as many conductors as are necessary in that class. 

But two sets of brushes are necessary for the two-circuit windings, unless 
the current is heavy enough to require a long commutator, in which case 
other sets of brushes can be added, up to the number of poles. 




Fig. 15. Ring Winding Cross-connected to Reduce Unequal Induction. 



In the short-connection type of this class, conductors under adjacent field 
poles are connected together so that the circuits from brush to brush are 
influenced by all the poles and are therefore equal. 

In the long-connection type the conductors under every other pole are con- 
nected, so that the conductors from brush to brush are influenced by but 
one-half the number of poles. 

The number of coils in a two-circuit long-connection multipolar winding is 
determined by the formula 



**=? 



y ± i, 



where Nk = the number of coils, p = the number of poles, and y = the 
pitch. The number of commutator segments is equal to the number of 
coils and must be a number not divisible without a remainder by the num- 
ber of pairs of poles. 

The pitch, y, is the number of coils advanced over for the connections, as, 
for instance, m an armature with a pitch of 7 the end of coil number 1 is 
connected to the beginning of coil 1+7 = 8, and from 8 to 8 + 7 = 15, and 
so on. In multipolar ring long-connection windings y may be any integer. 

Mr. Kapp gives in the following table the best practice as to angular dis- 
tance between brushes for this class of windings. 



344 



DYNAMOS AND MOTORS. 



Number 
of poles. 




Angular distance between brushes. 






Degrees. 


Degrees. 


Degrees. 


Degrees. 


Degrees. 


2 


180 










4 


90 










6 


60 


180 








8 


45 


135 








10 


36 


108 


180 






12 


30 


90 


150 






14 


25.7 


77 


128 


180 




16 


22.5 


67.5 


112 


158 




18 




60 


100 


140 


180 


20 




54 


90 


126 


162 



Fig. 16 shows a simple form of two-circuit multipolar single winding, and 
Fig. 17 another sample as used with a greater number of poles. 




WmMm 

Fig. 16. Two-path Multipolar Windings. Fig. 17. 

Both of the above samples are of the long -connection type. In the short* 
connection type the formula for determining the number of the coil is 

m = py ± 2, 
and Fig. 18 is a sample diagram of this type. 



ARMATURES. 



345 




Fig. 18. Short-connection Two-path Ring Winding. 

Dram Winding's. 

In order that the E.M.F.'s generated in the coils of a drum armature may 
be in the same direction, it is necessary that the two sides of each coil be in 
fields of opposite polarity, and therefore the sides of the coils are connected 
across the ends of the core ; directly across, for bipolar machines, and part 
way so for those of the multipolar type. 




Fig. 19. Bipolar Drum Winding. 

The drum winding is wholly on the exterior of the core. Fig. 19 is a dia- 
gram of a bipolar drum winding on a smooth core ; the dotted lines indicate 
the crossings of the wires over the rear head of the core. Drum windings 
are mostly of the two-layer type, of which Fig. 20 is a diagram; with a 
slotted core, the numbered conductors would lie within the slots. In this 
diagram each pair of conductors having numbers differing by 15 compose 
the two " sides " of one coil, and are therefore integral with each other. 



346 



DYNAMOS AND MOTORS. 



There are two general types of drum winding : lap and wave. If each 
coil has more than one turn, " lap-connected" and "wave-connected" 
are more appropriate distinguishing terms. Bipolar machines necessarily 




Fig. 20. Bipolar two-layer drum winding. 




FIG. 21. Two-path single four-pole winding 



have lap-connected windings. In multipolar machines the two " sides " of 
each coil are located a distance apart approximately equal to the pol« 
pitch instead of on opposite sides of the core (see Fig. 21). The proportion 
of armature circumference spanned by each coil is preferably a trifle less 



ARMATURES. 



347 



than the pole pitch ; for a toothed armature the number of teeth embraced 
by each coil should be equal to Nt-^p — xt . If Kt — p is a whole number, 
xt = 1 ; if it is a mixed number, xt = the fractional part or 1 -\- that part ; 
it should seldom exceed 2 in any case. 

All lap windings have p m parallel paths. A multiplex winding consists 
of two or more distinct windings, the conductors of which are arranged in 
regular sequence around the core ; the windings are connected to m sets 
of commutator segments assembled in a single commutator, as indicated 




Fig. 22. Six-path single drum winding. 



by Fig. 23. The terminals of each coil of any lap winding must be con- 
nected to two commutator segments between which there are m — 1 other 
segments. 

Wave-connected windings may have any even number of parallel paths 
regardless of the number of magnet poles, within practical limits. The 
number depends on the number of coils and method of connecting them. 
The relation between the number of coils (and commutator segments), num- 
ber of paths, number of magnet poles and method of connection is as 
follows : — 



Nh 



__ (l+l' 8 )p± q 
~~ 2 



and 



h= 8J ft*g-l 



(2) 



(3) 



The smaller value of ka is preferable, but choice between the two is usu- 
ally determined by the choice between the resulting classes of winding. If 
k» + 1 and JVk have a common factor, the winding will be of the plural or 
multiplex type ; if not, a simple wave-connected winding will result, pro- 
vided qT^p. 

In slotted armatures the number of conductors must be a multiple of the 
number of conductors per slot. 



348 



DYNAMOS AND MOTORS. 



Fig. 23 is a diagram of a two-path triplex winding, i.e., three two-path 
windings connected in parallel by the brushes. It is mathematically the 
equivalent of a single six-path winding. 




Fig. 23. 



Fig. 24 shows diagrammatically the characteristics of the usual two-path 
armature winding used on street railway motors, in which there are three 
times as many coils as there are slots. In this case xt ~ 0.25 and k» == 48. 




Fig. 24. 



ARMATURES. 349 

Balancing* the Magnetic Circuits in Dynamo*. 

Difficulty has been experienced in the operation of large multipolar direct- 
current machines with parallel wound armatures, owing to differing mag- 
netic strengths in the poles. The potential generated in conductors under 
one pole differed from that generated in conductors similarly situated under 
another pole of the same polarity, the result being a slight difference of 
potential between brushes of similar polarity. This caused currents to flow 
from one brush to another, and from one section of the armature winding 
to another, attended by wasteful heating of conductors and sparking at the 
brushes. This difficulty is obviated by the Westinghouse Electric & Manu- 
facturing Company by the following method of balancing : 

A number of points in the armature winding corresponding to the num- 
ber of pairs of poles, which are normally of equal potential, are connected 
by leads through which currents may pass from one section to the others 
with which it is connected in parallel. The currents are alternating in 
character 'and lead or lag with reference to their respective E.M.E.'s. 
They thus magnetize or demagnetize the field magnets and automatically 
produce the necessary balance. This method of balancing is also of advan- 
tage in eliminating the sparking at the brushes and the wasteful heating, 
which occur when an armature becomes decentralized, owing to wear of 
the bearings, or to other causes. When an armature gets out of center the 
air-gap on one side is greater than the air-gap on the opposite side. The 
potential generated in the coils — if the armature has the ordinary multiple 
winding — will be much greater on the side having the smaller air-gap than 
that generated under poles of the same polarity on the opposite side. Con- 
sequently, a current corresponding to this difference of potential flows 
through the brushes from one section of the winding to another. This flow 
of current will act the same as if two generators were coupled rigidly on one 
shaft and the potential of the one raised above that of the other. The 
machine having the higher potential would act as a generator, and the 
other would run as a motor. This, of course, would result in bad sparking 
and the burning of the brushes. 

By the use of the above balancing method, however, the armature could 
be considerably out of center and no injurious results occur, as the balanc- 
ing currents flow, not through the brushes, but, as explained above, through 
specially provided connections. In addition, the currents in these conduc- 
tors are alternating currents — " leading" in some coils and " lagging " in 
others — a fact which enables a relatively small current to balance the cir- 
cuits effectively. 

Heating- of Armatures. 

The temperature an armature will attain during a long run depends on 
its peripheral speed, the means adopted for ventilation, the heating of the 
conductors by eddy currents, the heating of the iron core by hysteresis and 
eddy currents, the ratio of the diameter of the insulated conductor to that 
of its copper core, the current density in the conductor, the radial depth of 
winding, whether the armature is of cylinder or drum type, and the amount 
and character of the cooling surface of the wound armature. 

The higher the peripheral speed of the armature the less is the rise of 
temperature in it. Mr. Esson gives, as the result of some experiments on 
armatures with smooth cooling surfaces, the following approximate rule : 

55 P A 350 P x 



"" £(1+0.00018 V) T S'{ 1 + 0.00059 V) ' 

where A = difference of temperature between the hottest part of the arma- 
ture and the surrounding air in degrees, Centigrade, 
P A = watts wasted in armature, 
S = .ictiVe cooling surface in square inches, 
S' = active cooling surface in square centimeters, 

V = peripheral speed of armature in feet per minute, 

V =. peripheral speed in meters per minute. 



350 DYNAMOS AND MOTORS. 

The more efficient the means adopted for ventilating the armature by 
currents of air, the smaller is the temperature rise. Some makers leave 
spaces between the winding at intervals, thus allowing the air free access 
to the core and between the conductors. A draught of air through the in- 
terior of the armature assists cooling and should be arranged for whenever 
possible. 

For heavy currents it is sometimes necessary to subdivide the conductors 
to prevent eddy currents; stranded conductors, rolled or pressed hydraulic- 
ally, of rectangular or wedge-shaped section, have been used. Such sub- 
division should be parallel to the axis of the conductor, and preferably 
effected by the use of stranded wires rather than laminae. Few armature 
conductors of American dynamos of to-day are divided or laminated in any 
degree whatsoever. Solid copper bars of approximately rectangular cross- 
section are often used, and little trouble is found from Foucault currents. 

Mr. Kapp considers 1.5 square inches (9.7 square centimeters) of cooling 
surface per watt wasted in the armature a fair allowance. 

Esson gives the following for armatures revolving at 3000 feet per minute : 

P x = watts wasted in heat in winding and core, 
S = cooling surface, exterior, interior, and ends, in square inches, 
S' = cooling surface, exterior, interior, and ends, in square centi- 
meters, 

A = temperature difference between hottest part of armature and 

surrounding air in C°. 



Then 



_ 35 P A w 225 P A 



Specifications for standard electrical apparatus for IT. S. Navy say, " No 
part of the dynamo, field, or armature windings shall heat more than 50° F. 
above the temperature of the surrounding air after a run of four hours at 
maximum rated output." 

According to the British Admiralty specification for dynamos, the tem- 
perature of the armature one minute after stopping, after a six hours' run, 
must not exceed 30° F. above that of the atmosphere. In this test the ther- 
mometer is raised to a temperature of 30° F. above that of the atmosphere 
before it is placed in contact with the armature, and the dynamo complies 
(or does not comply) with the specification according as the thermometer 
does not (or does) indicate a further rise of temperature. 

The best dynamo makers to-day specify 40° and 45° C. as the maximum 
rise in temperature of the hottest part of a dynamo, or 55° if the tempera- 
ture of the commutator surface is to be measured. 

Armature Reactions. 

In many direct-current dynamos having no special devices for reversing 
the current in each armature coil as it passes through the " commutating 
zone," it is necessary to give the brushes a forward lead so that the mag- 
netic fringe from the pole-tip toward which the coil is moving may induce 
an E.M.F. in the coil and reverse the current. In motors the brushes are 
shifted rearward instead of forward, the polarity of the approaching pole- 
tip being of the wrong sign. 

With the forward lead given to the brushes the effect of the armature cur- 
rent is to weaken and distort the magnetic field set up by the field mag- 
nets ; a certain number — depending on the lead of the brushes — of the ar- 
mature ampere-turns directly oppose those on the field-magnets and render 
a somewhat larger number of these ineffective, except as regards wasting 
power ; the remaining armature ampere-turns tend to set up a magnetic field 
at right angles to the main field, with the result that the resultant field 
is rotated forward in the direction of motion of the armature, and that the 
field strength is reduced in the neighborhood of every trailing pole-piece 
horn, and is increased in that of every leading pole-piece horn. When, 
therefore, the brushes have a forward lead each armature section as it comes 
under a brush enters a part of the field of which the strength is reduced by 



ARMATURES. 351 

the armature cross-induction ; and, if this reduction is great, the field 
strength necessary for reversing the current in the section (in the short 
time that the section is short-circuited under the brush) may not be ob- 
tained, and sparkless collection may thus be rendered impossible. 

Various devices for reversing the currents in the armature sections, as 
they pass successively under the brushes, without giving a forward lead to 
the brushes, have been proposed ; a number of these were described in a 

Saper by Mr. Swinburne ; an improvement by Mr. W. B. Sayers consists in 
iterposing auxiliary coils between the joints of adjacent armature sections 
and the corresponding commutator bars. Each auxiliary coil is wound on 
the armature with a lead relative to the two main armature sections and 
the commutator bar which it connects together. The result of this arrange- 
ment is that the difference between the E.M.F.'s in the two auxiliary coils 
connecting any given armature section to the two corresponding commutator 
bars may be made sufficient to reverse the current in the armature section 
when short-circuited under a brush, even if the brush has a backward in- 
stead of a forward lead. 

In the Thompson-Ryan dynamo the effects of armature reaction are neu- 
tralized by a special winding through slots across the faces of the pole- 
pieces, parallel with the axis of the armature ; this winding is in series with 
the armature, and the same current flowing in both, but in such direction 
that all effects on the field magnets are neutralized, the ampere-turns of the 
shunt are therefore much less than in other dynamos, there is no sparking 
, under any ordinary conditions of load, the brushes are placed permanently 
when the machine is set up, and the efficiency is high through a wide range. 

The method which is most widely employed is to put small auxiliary 
field-magnet poles between the main poles and connect their windings in 
series with the armature. This method is applied chiefly to constant-poten- 
tial motors designed to run at several speeds. 

Drag- on Armature Conductors. _ i n dynamos, each armature 
conductor has to be driven in opposition to an effort or drag proportional at 
every instant to the product of the current carried by the conductor into 
the strength of the magnetic field. This drag on a conductor, varies, there- 
fore, with the position of the conductor relative to the field-magnet poles, 
and is a maximum when the conductor passes through that part of the air- 
gap at which the magnetic induction is greatest. The arrangements for 
driving the armature conductors must, of course, be adapted to the greatest 
value of the drag to which a conductor is exposed, and this is given for 
smooth core armatures by the formula below. 

Let %• = current in amperes carried by each conductor, 

(ft = maximum induction in air-gap per square centimeter, 
B = maximum induction in air-gap per square inch, 
Wa = length of armature core in inches. 

mv ($>Waia B Wa la -, . „ . _. 

Then 1^300 = 13,302,360 = Maximum P ul1 m lbs - on each conductor. 
In slotted armatures the core teeth take the drag. 

COJ1 yi\ T II OH* AID BRUSHES, 

Commutators are built up of the best grade of copper, preferably hard 
drawn. The insulation between segments should invariably be of the best 
quality of amber mica ; white mica is usually too hard and brittle, and does 
not wear down as rapidly as the copper segments, so that eventually the 
mica strips project above the surface and cause the brushes to chatter and 
spark. The insulation at the ends is usually of micanite, and should be as 
hard as possible. 

Brushes are invariably of carbon except on machines built for very low 
voltages. The high resistance of the carbon reduces the "short-circuit" 
current in a coil undergoing commutation and also reduces the inductive 
opposition to the reversal of current in the coil, thereby facilitating com- 
mutation. 

The current density under brush faces should not exceed 60 amperes per 
square inch for carbon, 200 for woven wire, or 250 amps, per sq. in. for soft 



352 



DYNAMOS AND MOTORS. 



leaf copper brushes. The proper density to be used in any given case de- 
pends upon other features of commutator and brush proportions. See 
44 Practical Design," page 361. 

FIEJLO Mie]¥ETS. 

Field magnets are bipolar in small sizes and multipolar in large sizes | 
the dividing line between bipolar and multipolar construction varies from 
1 kilowatt to 10 kilowatts ; it is quite common practice to make machines 
of 5 kilowatts and over multipolar. Magnet cores are made either of 
wrought iron or steel, except in very small machines in which cast iron is 
used. Pole-pieces or shoes are of either cast iron or steel, according to 
their shape and disposition. Cast-iron shoes are attached to the sides of 
the pole and merely extend the pole-face surface ; steel shoes are bolted 
against the free ends of the poles so that the entire air-gap flux passes 
through the shoe. In many cases no shoes are used, the poles being carried 
to the air-gap without change in cross-section, or else provided with integral 
polar extensions at the free ends. 

Field magnet yokes are either of cast steel or cast iron. The latter is 
preferable on every score except weight, for the reason that steel castings 
are seldom perfectly sound throughout and rarely within & inch of calcu- 
lated dimensions. Magnet cores are generally bolted to the yoke, but a 
few builders still " cast-weld " them in. 



Coil Surface Necessary for Safe Temperature. 

Esson gives the following method of determining the surface necessary for 
a magnet coil to keep its heat within assigned limits. 
Let P == watts wasted in heating, 

S = cooling surface in square inches of coil, not including end flanges 

and interior, 
^rr same as above in square centimeters, 
= temperature of hottest part above surrounding air, 



then 



F.°= 99 ^ or C.°= 335 ^. 



Maximum current 



-/ 



degs.F. x sq. ins. 



99 X hot r 
Hot r = cold r -}- 1% for each additional 4.5° F. 



Table of Cooling- Surfaces. 



Excess temperature above sur- 
rounding air. 


Cooling surface per watt in 


F.° 


C.° 


square inches. 


sq. centimeters. 




15 


3.67 


23.7 


30 


— 


3.30 


21.3 





20 


2.75 


17.8 


40 


— 


2.48 


16.0 


— 


25 


2.20 


14.2 


50 


— 


1.98 


12.8 





30 


1.83 


11.8 


60 


— 


1.65 


10.7 


— 


35 


1.57 


10.1 


70 


— 


1.41 


9.1 


~~ 


40 


1.38 


8.9 



DIRECT-CURRENT MOTORS. 



353 



Ctyrostatic Action on Dynamos in Ships. 



L — 



(Lord Kelvin.) 
and P = 



where 



g* 



L = moment of couple on axis, 
P=z pressure on each bearing, 
Wz=z weight of armature, 
k = radius of gyration about axis, 

n=r -= A ■=. maximum angular velocity of dynamo in radians per 

second due to rolling of ship, 

A == zrr^ = amplitude in radians per second, 
loO 

(Radian is unit angle in circular measure.) 

d = degrees of roll from mean position, 

Tz=. periodic time in seconds, 

<o =r 2 nn = angular velocity of armature in radians per second, 

n = number of revolutions of armature per second, 

I = distance between bearings, 

g =. acceleration due to gravity. 
Note. — On applying the above formula to dynamos, where W, k, and to 
are great, it will be found advisable to place their plane of rotation athwart- 
ships, in order to avoid as far as possible wear and tear of bearings due to 
the gyrostatic action. 



(4) 



DIRECT-CIRREIT MOTORS. 

The counter E.M.F. generated in a motor armature is given by equation 
(1). This E.M.F. is equal to the E.M.F. applied at the motor brushes minus 
the drop in the armature winding and connections ; consequently, the speed 
of a motor is 

60 (Ew — IaR)q 10* 

R.p.m. = — i ^_ — L2 

* <b Ncp 

At no load, the drop in the armature circuit is so small that Ew — IaR 
may be considered equal to Ew, for the purpose of computing the no-load 
speed. 

The torque of a motor armature, in pound-feet, is 

2 7 z=117^iV r c iai?10- 11 (5) 

Motors for operation on constant-potential circuits are : 

Shunt-wound, for service requiring practically constant speed and im- 
posing small load at starting ; 

Series-wound, for starting heavy loads from standstill and running at 
speeds inversely varying as the load ; 

Compound-wound, for starting heavy loads and 
running at nearly constant speed. 

Diiferentially-wound, for starting under light 
loads and running at strictly constant speed. 
(This type is not much used now.) 

The remarks concerning dynamo magnets, ar- 
matures, etc., apply also to direct-current motors. 
The magnetization curve may be obtained by driv- 
ing the machine as a dynamo ; or it may be plotted 
from readings of field excitation and armature 
speed ; in the latter case, the curve will be tbe in- 
verse of Fig. 1, as indicated by Fig. 25. 

Brushes on a motor must usually be set back of 
the neutral point, or with a " backward lead." 
This tends to demagnetize the fields, and as weak- 
ening the fields of a motor tends to increase the 
speed, the increase of load on a shunt-wound 
motor tends to prevent the speed falling, and the shunt motor is very 
nearly self-regulating. 



\ 








^ 


^ 



z 

of 

u 

a 

1 

P 

3 

I 

AMPERETURNS 

IN FIELD WINDING 

Fig. 25. Magnetization 
Curve of Motor. 



354 



DYNAMOS AND MOTORS. 



Leonard'! System of Motor Control. 

Wherever it becomes necessary to vary the speed and torque of a continu 
ous current electric motor to any considerable degree, any of the rheostat 
methods introduce very considerable losses, and are apt to induce ba«l 
sparking at the commutator. 

H. Ward Leonard invented the method shown in Fig. 26, which givea 
most excellent results, although to some extent complicated, and is highly 
efficient. 

The driving motor, or rather motor which it is wished to control, is pro- 
vided with a separately excited field, which can be varied by us rheostat to 
produce any rate of speed, from just turning to the full speed of which it 
may be capable. Current is supplied to its armature from a separate gen- 
erator, and by varying the separately excited field of this generator, the 
amount of current supplied to the motor armature can be varied at will, and 
the torque therefore changed to suit the circumstances. 

The generator is driven at constant speed by direct connection to a motor 
which gets its current from an outside source, or to another generator 



RHEOSTAT 





MOTOR, GENERATOR 

Fig. 26. Leonard's System of Motor 
Control. 



Fig. 27. Leonard's System of 
Electric Propulsion. 



driven by some other motive power, say a steam engine. This driven gen- 
erator supplies current for exciting the fields of the secondary generator 
and main motor. 

By reversing the field of the generator, the current in its armature is 
reversed, and therefore so is the direction of rotation of the motor armature. 

Fig. 27 shows the Leonard system adapted to electric street railway motor 
control. 



Three-Wire System for Variable Speed IWEotor Work. 

Omitting cranes, street railways, hoists, and other classes of service 
where the series motor with rheostatic control is used, variable speed motor 
work may be divided into three classes : 

(1) Machines requiring a torque increasing with the speed. Blowers and 
fans belong to this class. The power required for the machine increases 
very rapidly as the speed increases, and care should be exercised in selecting 
motors for 6uch service. However, as the variation required is usually 
small, the requirements can be met with standard motors on a single vol- 
tage system. Motors should preferably be compound-wound and the speed 
should be varied by means of a resistance in the shunt field. 

(2) Machines requiring a constant torque. In this class pumps and air 
compressors are examples. The speed variation required for such service 
is usually small, and it is generally best and most economical to supply 
compound motors and to vary the speed by means of the shunt field rheo- 
stat, as in the case of the fans and blowers. A series winding is especially 
beneficial for this class of work in preventing the heavy fluctuations of cur- 
rent that would take place with a constant speed motor in passing through 
the different parts of the cycle. A compound motor may be used for this 



PRACTICAL DYNAMO DESIGN. 



355 



work because a constant speed at any point on the controller is not 
necessary. » 

(3) Machines requiring approximately the same maximum output at any 
speed, or a torque varying inversely as the speed. This class includes most 
of the machine tool work Avhere automatically constant speed regulation on 
any notch of the controller is especially desirable. It is, therefore, neces- 
sary to use a shunt motor having good inherent regulation. 

Tlie Generator.- The standard Edison three-wire system for general 
distribution consists of two 125-volt generators connected in series with 
the neutral wire brought out from between them. A single generator of the 
over-all voltage, with a motor-generator set of sufficient capacity to carry 
the unbalanced current, is used in many places. Still another system con- 
sists broadly of a standard direct-current 
generator designed for the maximum 
required E.M.F. having collector rings 
connected to the armature winding like 
a two-phase rotary converter. The leads 
from these rings are connected to auto- 
transformers or balancing coils, the 
middle points of which are connected 
to the neutral wire. With no external 
devices whatever, the neutral wire is 
'thus maintained at a voltage midway 
between the outside wires of the system 
(see Fig. 28). These generators may be 
operated in multiple with any standard 
three-wire system, whether it consists 
of two machines operated in series, a 
single voltage generator with a balanc- 
ing set or a double commutator gen- 
erator. Any standard single-voltage 

system may be changed into a three-wire system by adding collector rings 
to the generator and using balancing coils to supply the neutral wire. 




PRACTICAL «T> F A1TIO DESIGN.* 

It is safe to follow the rule of using bipolar field-magnets for machines of 
4 kilowatts or less and multipolar magnets for larger machines. 

For commutation reasons the current passing any one set of brushes 
should not exceed 250 amperes ; this gives a criterion of the number of 
poles for machines of 250 amperes output or more. Lap windings should 
be used on such machines. Then 



P — 



0.008 la 



(6) 



The number of poles on machines having wave-connected armatures is 
determined by commutation considerations chiefly ; more than six poles are 
seldom used. 

The best construction is a laminated magnet pole with extensions at the 
air-gap end, bolted to a cast-steel yoke. Fairly good results are obtained, 
however, with cast-steel poles. Laminated cores, cast-welded into either 
iron or steel yoke and provided with cast-iron shoes embracing the ends at 
the air-gap, give excellent results if the cast-welding is properly done. 
When the ratio of air-gap length to the width of each armature core-slot 
opening is much less than 0.5, the pole-face should be laminated in order to 
prevent excessive eddy curents in it ; otherwise it may be solid. A cast-iron 
pole-shoe must not cover the end of the magnet core, but should surround 
it and serve merely as lateral extensions ; the cross section of the core 
should be slightly reduced where it is surrounded by the pole-shoe. 

* Cecil P. Poole. 



356 



DYNAMOS AND MOTORS. 



The E.M.F. generated in the direct-current armature is, from eq. (X), 

p op q 60 

which reduces to 

E = 0.05236 Dp Wp \f/ Bp & r.p.m. 10 -8 -J- q. 

The output in watts is Pw =. Ew Iw, which for preliminary purposes may 
be considered the equal to E ia q ; whence 

Pu> — 0.05236 Dp Wp^i Bp i« Nc r.p.m. 10 ~ 8 .... (7) 

For economical use of material, the projected outline of a pole-face should 
be square, so that the width parallel to the armature shaft should approxi- 
mately equal the chord of the average polar arc; whence Wp should 
be— Dp sin (180 \p -f- p). For moderately high-speed machines, ^ may be 
taken at 0.7 ; for slightly lower speeds, at 0.72, and for slow-speed machines, 
at 0.75. For reversing motors it is best put at 0.6666, except series-wound 
reversing motors ; for these, let $ =: 0.7. 

Representing sin (180 i// — p) by kch, page 371, results. 

The average magnetic density over the pole-face ranges from 25,000 to 
60,000 lines per square inch, according to the designer's method and the size 
of the machine. It is rational to make Bp = cX Dp 0,15 ,c being a coefficient 
varying according to the type of machine. For constant-potential dynamos 
and motors for general service, 28,120 is a suitable value for c ; for shunt or 
compound-wound reversing motors, 33,850 is appropriate, and for series re- 
versing motors, 36,620. 

The permissible number of ampere-conductors around the armature peri- 
phery ranges from 1200 to 2200 per inch of armature diameter. For ma- 
chines designed according to the method outlined herein, it is good 
practice to apply the formula: 

. ._ he Dp*-™ 

taNeZ=Z p 

The values of kc are as follows : 

Dynamos and motors for general service, kc = 679. 
Shunt and compound reversing motors, kc = 564. 

Series-wound reversing motors, kc = 678. 

From the foregoing equation an equivalent is obviously obtainable for 
iaNc «//, and substituting this and the equivalents for Bp a ^d Wp previously 
obtained, equation (7) reduces to the following two : 

For all machines except series-wound reversing motors : 

_ fc*ZV».s r .p. m . 

p "~ ioo — (8) 

For series-wound reversing motors : 

Pw = 0.013 kch Dp™ r.p.m (9) 

For belted machines which need not have any particular rate of speed, an 
economical rate is 

8500 

Considering Da and Dp equal, which is allowable in preliminary " rough- 
ing out," and substituting in equation (8) the above equivalent for r.p.m.: 

Pw = 85 kch Dp*- 6 (10) 

Armature Details. — Core disks 25 mils thick may be used in most 
armatures ; only those in which the core is subjected to high rates of mag- 
netic reversal need have thinner disks. When p x r.p.m. exceeds 3000. it is 
advisable to use disks 20 mils thick, or less ; wnenp x r.p.m. exceeds 4000, 
15 mils should be the limiting thickness. The final criterion, however, is 
the eddy current loss in the core and teeth. 



PRACTICAL DYNAMO DESIGN. 



357 



Having a means of determining the pole-face width parallel to the arma- 
ture shaft, the length of the armature core follows within close limits. 
The armature core should extend beyond the edges of the pole-face at each 
end by a small amount — not less than the air-gap length, and preferably 
1.5 times the air-gap. 

Armature cores more than 5 inches long should have ventilating ducts 
not less than § inch wide at intervals of 2J to 3^ inches. The exact duct 
width is usually determined by the amount of steel required parallel to the 
shaft in order to keep the magnetic density in the teeth within suitable 
limits. 

The" nominal " magnetic density at the narrowest part of the teeth should 
be between 140,000 and 155,000 lines per square inch of net cross section. 
The " nominal " density is that which would exist if the flux did not spread 
beyond the geometrical contour of the pole-face in passing from the latter 
to the armature, and if all of the flux passed through the teeth ; that is, 



--. ,-*. — = nominal density at tooth roots, 

Nt^tWa 

wa = 0.9 (Wa— ventilating ducts). 

In order to obtain dimensions that will result in a " nominal " density at 
the roots of the teeth that will be within the specified range, the number of 
teeth (and slots) may be approximated by means of the formula 



-nDt- 



Nt = - 



kt 

Wa 



(11) 



The number of teeth must, of course, be an integer ; if the result of eq. (11) 
should be a mixed number, therefore, the fractional part should be discarded 
if it is 0.8 or less ; if it be more than 0.8, the next higher integer is to be 
taken as the number of teeth. The net measurement of the armature iron 
parallel with the shaft must then be corrected to satisfy the equation, 



kt 



' it Dt — sNt 



(12) 



The value of kt for all cases is 



__ 0.053 Dp* W P 

When the armature conductors are round wires, the size of the coil slot 
is determined chiefly by the size and arrangement of the wires. Form-wound 





WW/////. 




Fig. 29. 



and separately-insulated coils are generally used, so that the coil slot is 
ordinarily of one of the shapes shown in Fig. 29, the slots a or b being used 
when binding wires are employed to keep the wires in their slots, and one of 
the others when the coils are held in by wedges. Two-layer windings are 
almost invariably used in this country. Fig. 30 shows two half-coils 
*• abreast " in each layer, each coil having three turns of wire ; this makes 



358 



DYNAMOS AND MOTORS. 



the total number of coils twice the number of slots. Fig. 31 shows three 
half coils " nested," with two turns per coil ; this gives three times as many 
coils as there are slots, " three coils per slot." It is extremely objectionable 
to " nest " the coils, but sometimes unavoidable when round wires are used. 
Table II, p. 372, gives slot widths and depths suitable for various arrange- 
ments of round conductors drawn to B. & S. gauge, based on two-layer wind- 
ings and the insulation indicated in Fig. 32. The individual coils are wrapped 



Slot trough 




Fig. 30. 




Fig. 31. 



each in a single fold of 0.015-inch mica-treated press-board, each group of 
coils is wrapped with a single covering of 0.01-inch oiled tape, half lapped, 
and the slot is lined with a trough of 0.02-inch mica-treated press-board. 
If the press-board is well varnished with insulating compound, and the 
coils are dipped and baked before being assembled in the slots, this insula- 
tion will be adequate for 550-volt armatures. 

The Avidth of a coil slot should not be less than $ of its depth nor more 
than £ the depth. The depth of the coil slot, for armature of 16 inches 
diameter or over, may be estimated for preliminary purposes by means of 
the formula 

a=i+5 < 13 > 

Appropriate trial depths for the coil slots of smaller cores are given by 
Table III, page 373. 

Table IV, page 373, gives empirical but practical trial values for the mini- 
mum allowable number of armature coils, and Table V, page 374, gives values 
for the maximum allowable number of turns per coil, for use in preliminary 
11 roughing-out." The former are somewhat elastic, but the latter can sel- 
dom be exceeded without risk of sparking at the brushes. 

Table VI, page 375, gives trial values for armature conductor sizes ; the 
actual allowable current density in the conductors, however, is determined 
by the heating of the armature. 

Armature bosses. —The total losses in the armature should not 
exceed the value which will give a temperature rise, under full load, of 70°F. 
The relation between lost watts, radiating surface, peripheral velocity 
and temperature rise is, for fairly well ventilated armatures in non-enclosed 
field magnet frames, approximately as follows : 

35P' A 



DaWa[l + 



(• 



y(7),r.p.m.)» 



420,000 



and allowing a rise of 70° this transposes to 



210 



)' 

r.p.m.) 8 \ 
^000 / 



(H) 



PRACTICAL DYNAMO DESIGN. 359 

The reason for taking P' A instead of P A as the criterion of heating is 
that the projecting parts of the winding do not act effectively in radiating 
the heat produced by the core and teeth losses, although their radiating 
surface is always ample for the i^r loss in them. Since they are not included 
in the radiating surface, the loss in them is not included in considering the 
heating. 

With round conductors, the watts lost in the embedded part of the wind- 
ing will be, with sufficient accuracy, 

Pr' = WaNc ~\ 

a 2 
if the conductors are rectangular in cross section, — — must be substituted 

for -^ in this equation. 
a 2 
The losses in the armature teeth must be estimated separately from those 
in the body of the core, the densities being widely different in the two parts. 
The general formula for hysteresis loss in either part of the core is 

Ph — 48 kh vp r.p.m. 10 — 7 

and the formula for eddy current loss is 

Pe = 4 k e vp 2 (r.p.m. )2 10 -■ 

in which kh is the loss per cubic foot of iron due to hysteresis, as given in 
the table on page 100 and ke the corresponding eddy current loss as given in 
the table on page 106. It should be borne in mind that although the con- 
stants taken from the tables mentioned are based on losses per cubic foot of 
iron or steel, the volume of iron or steel represented by v in the equations 
is in cubic inches. Combining the three equations just given, the total loss 
to be considered in estimating the heating of the armature is 

P A ' —WaNc l -£+p r.p.m. JO" » [48 (v a kha + vt kht) 

-f 0.4 p r.p.m. (Vakea + Vt ketj\ (15) 

In order to allow for the crowding of the magnetic flux toward the slots 
the cross section of the armature core body may be taken at 0.8 of the actual 
cross section, making the effective volume 

Va = 0.2 7T (2)«2 — Do 2 ) Wa (16) 

and the effective density will be, accordingly, 

# 
Ba= 0.8(Z)< — J) )w a ' • (17) 

For computing the probable losses in the teeth the following relations may 
be assumed without appreciable error : 

active teeth ) (2k ff S 



stive teeth ) _ /2_M £ \ # 
per pole \~ [nVp+p)"*' 



average width of each tooth =. (t -|- 2 t) -±- 3 ; 

and since (t -f 2 1) -^- 3 = [n (D a — 1.33 h) —Nt s] -=- Nt, and the average density 
in the teeth, for the present purpose, is equal to the flux per pole -J- active 
teeth per pole x average cross section per tooth, the average density will be 

Avg.B T = /0 ^ ,,„ * • • • (18) 



(v25 + |) ^( Da ~ 1 ' 3 ^ + Nt ^ Wa 



The volume of iron in the teeth is 

Vt— V-Da 2 — ™-D#—hsNA Wa (19) 



360 



DYNAMOS AND MOTORS. 



The value of kg in eq. (18) depends upon the relation between the inter- 
polar space (distance between neighboring pole-tips of opposite polarity) and 
the air-gap length, and also upon the slope of the pole from the tip toward 




Armature 
Center 



Fig. 33. 



the main part of the core. Table VII, page 376, gives practical values of k g 
within ordinary limits, and Fig. 33 indicates the angle represented in the 
table heading by a. 

Fig. 34 affords a simple method of estimating roughly the armature core 
losses which is favored by Messrs. Parshall and Hobart ; the curves here 



450 




































t* 


^ A 


















































































■D 










































Jd 


































M S 








,^ 


400 






























s 


<r 






M s 
































y 








> 
































> 








y 


































y 






s 


































y 






S 




































y 






y 










350 
























y 






y* 




































/ 




s 










































s 








































t y 
















n/\n 
























s 


















300 




















y 








































y 










































/ 








































/ 




s 






















250 
















/ 


> 




































y 


* 


y 








































y 










































/ 








































y 




























200 














/ 






































/ 






































































































































































































150 






































































































A 


<-^\i 






„A 1 


• 




*A-~ 




ces 




























100 




/ 














"D. 


01 ' 4.4. A ~ ~L A 




:esr 






// 














O 
















L ^U 


itu * 






// 


















































































V 


7 






































50 


// 








































// 










































// 










































u 










































1 











































f 








































) 





.2 





.4 





.6 





.8 




L 


1 


.2 


1 


.4 


l 


6 


l 


.8 


2 



Watts per cubic inch; core and teeth. 
Fig. 34- 



PRACTICAL DYNAMO DESIGN. 361 

shown were plotted by Messrs. Esterlein and Reid from tests made on a 
large number of actual machines. 

In estimating before hand the efficiency of a machine, the loss in the pro- 
jecting parts of the armature winding must, of course, be considered. The 
actual total losses in the armature winding and core will be approximately 

P A = lc Nc ^+P r.p.m. 10~ 7 [48 (Vakha -J- vtkht) 

-hOApr.p.m. (vtket + vak*a)] (20) 

In a barrel winding, the length of each conductor (l e ) will be practically 
that given by the formula 

*e= W. + kw (Da — h) -f 0.8 (1 + h), 

if the conductors are bent around £-inch pins, as indicated in Fig. 35, and 




Fig. 35. 

afterward pulled out to span the proper number of teeth. Table VIII, page 
376, gives values of kw for different numbers of poles. Each coil will project 
beyond the armature core at each end about 

-^ (Da — h) -\ — inches, 

and the distance from center to center of the winding pins must be equal 
to 

Wa + kw (Da — h) inches. 

Commutator and Brushes. — The number of commutator bars = 
number of armature coils or elements, in practically all modern windings. 
The diameter of the commutator barrel must be kept as small as possible in 
order to reduce the friction loss at the brush faces as well as to keep down 
the cost of the commutator and to favor good commutation. From purely 
mechanical considerations, 

Dk > 0.06 x Number of segments (21) 

For commutation reasons and to keep down friction, 

Dk < 10,000 -f r.p.m (22) 

In finally rounding out the dimensions, the following relation should be ob- 
served, if possible, 

t^ -W* b ___,. 

Dk— (23) 

3 rik v ' 

and n* should preferably be an integer. 

The current density in each commutator segment should not much exceed 
2000 amperes per square inch in the horizontal part and 2500 amperes per 
square inch in the connecting lugs or risers. 

The brush faces should be of such area and number that the current den- 
sity at the faces will not exceed 40 amperes per square inch for carbon 
brushes, 150 amperes per square inch for woven wire or gauze brushes, or 



362 DYNAMOS AND MOTORS. 



200 amperes per square inch for leaf copper brushes. Good average face 
densities are 30, 120, and 160 amperes per square inch, respectively. 

With pressures of 11 to 1\ lbs. per square inch of brush face, the effective 
resistance of the brushes will usually be 
Carbon brushes : 



Copper brushes : 



Ab 

0.0125 

— -a — = Rb - 
Ab 



The total drop in volts at the brush faces, therefore, will be 
Carbon brushes : 



Copper brushes : 

^~ = volts drop • . . (24a) 

The loss in watts due to the friction of the brush contacts with the com- 
mutator is 

Ab Dk r.p.m. 

kb ' 

kb varying according to the brush pressure, condition of commutator and 
quality of brush. The total losses at the brush faces, therefore, are 
Carbon brushes : 

^^ + 0^" m 

Copper brushes : 

AbDk r.p.m. /a 2 __ Pjk , OK . 
U- - + 8Q-Ab- Pb (25a) 

reasonably good condition, 



With ordinary grades of copper and carbon brushes and a commutator in 
d c 



560 

kb = : 



brush pressure in lbs. per sq. inch 



The maximum efficiency is obtained when the two terms of eqs. (25) and 
(25a) are equal, i. c, when the friction loss equals the J 2 R loss. 
The temperature rise of the commutator will usually be 

85 X total lost watts /0 _. 

— uk (^b) 



■»(* + ^ 



If the lugs of the commutator segments are of considerable length, the 
rise of temperature will be somewhat less than calculated; on the other 
hand, if the commutator and brushes are not in good condition, the losses 
will be considerably more than given by eq. (25) or (25a) and the tempera- 
ture rise will be correspondingly greater. The temperature rise should in 
no case exceed 75° Fahrenheit, and it is preferable to keep it down to 65° or 
70°. 

The dimension of the brush face transverse to the commutator segments, 
is determined almost solely by commutation requirements, and these in- 
volve so many widely varying factors that no hard-and-fast general rule 
can be laid down. For machines of ordinary types and fairly large sizes — 
100 kilowatts and over, say — the span of a carbon brush may be roughly 
estimated by means of the formula 

. Dk r ,. iaNc 1 /rt _. 

6 " T L * (1 ~ *' ~ MSTBbJ (27) 



PRACTICAL DYNAMO DESIGN. 



363 



This formula will apply with sufficient closeness for all practical work by 
determining the value, for a given type of design, of the coefficient in the 
denominator of the bracketed fraction. For reversing motors of a certain 
type, for example, it is 1600, and for small, shunt-wound motors of conven- 
tional design, it ranges from 800 to 1000. 

Air-Crap. — The mechanical air-gap, from the pole-face to the tops of 
the armature teeth, should be made the nearest commercial dimension to 
that given by the formula 



General Service 
Machines. 

18p 



All Other 
Machines. 

20p 



(28) 



Thus, if the formula gives 0.188 inch as the proper air-gap length and the 
machine is to be built by English measure, the actual value to be used 
would be T ^ inch. In such cases a revision of the pole-face density should be 
made in order that the ampere-turns devoted to the air-gap shall conform tc 




Machine 



Axis 




Machin e 



Fig. 36. 



Fig. 37. 



the plan of design which is the basis of this section. See " Checking up 
Preliminary Dimensions below." 

role-Face. — The dimensions of the pole-face are determinable as 
previously described, the average chord being equal to kch Dp and the width 
parallel to the shaft being preferably equal to the chord. 

If solid pole-faces are used, the interpolar edges should not be strictly 
parallel to the armature slots. A common expedient for avoiding this par- 
allelism is to round the interpolar edges as in Fig. 36, or to make them 
slightly oblique with respect to the axis of the machine, as in Fig. 37. If 
laminated poles without shoes are used, the corners of alternate sheets of 




Fig. 38. 



Fig. 39. 



steel should be cut away as in Fig. 38 for straight poles, or the tips cut off, 
as in Fig. 39, for polar extensions. 

The length of the pole-face span should never exceed 2.5 Dp 4- p ; practi- 
cal values are given in the beginning of this section (page 356.) 

Checking* up Preliminary Dimensions. — Before passing on to 
the field-magnet proportions, and preferably before taking up the probable 
armature losses, the preliminary dimensions should be checked up in order 
to make sure that the desired E.M.F. is obtainable at the desired speed 
without entailing the use of excessive magnetic densities. 



364 DYNAMOS AND MOTORS. 

Having ascertained by means of eq. (11) the maximum number of coil 
slots allowable and adjusted the net armature iron dimension axially by 
eq. (12) the E.M.F. or counter E.M.F. of the armature should be tested by the 
formula: 

_ frzy-"yr P *iy«r.p.m.io-» 

pq8 ' ' 

and if the E.M.F. is not what is desired, the armature diameter should be 
changed to correct it rather than change the value of either W p or ty or both. 
On the basis of the author's method, the E.M.F. is proportional to ZV 15 » if it 
be assumed that the number of wires will increase or diminish in proportion 
to small variations in the diameter ; therefore, if the preliminary dimen- 
sions do not give the proper E.M.F., the correct dimensions may be closely 
approximated by 

Tri al ZV-15 x E 

Trials = Correct B *> > 

the word " trial" referring to the diameter and E.M.F. first obtained. 

If the air-gap length actually adopted is not precisely the value given by 
eq. (28), the pole-face density should be adjusted to satisfy the equation, 

_ kdD P ^ 
Bp ~ p & < 30) 

The values of kv and kd are as follows : 

Type of Machine: General Service. Co^^g. **<&££* 

k v — 81 88 95 

kd— 1562 1692 1831 

The tendency to field distortion and sparking at the brushes should also 
be checked (after correcting the armature dimensions and pole-face density 
as just explained) before taking up the field magnet proportions. 

Armature Reaction and Commutation. — In order to guard 
against excessive field distortion the relation between the air-gap ampere- 
turns and armature ampere-turns should be as indicated by the following 
formula, for operation with fixed brushes at all loads : 

& p p8>kriaNc*l/ (31) 

The value of kr varies as follows : 

In general service machines, kr = 2.3. 

In shunt and compound reversing motors, kr 2j 3. 
In series-wound motors, kr = 2.7. 

The formula is based on the facts that Bp5 is approximately proportiona! 
to the ampere-turns required by the air-gap, and ia Nc \jt -f- p — armature 
ampere-turns tending to distort the field under each pole-face. 

The tendency to sparking at the brushes is proportional to the inductance 
of each coil, the number of coils simultaneously short-circuited by one 
brush, the number of coils in series between one positive and one negative 
brush and the current in the coil being commutated, and inversely propor- 
tional to the length of time the coil is short-circuited by the brush. The 
induotance of the coil is proportional to the length of the conductor and 
the square of the number of turns per coil. The following formula, based 
on these considerations, is an excellent criterion as to the sparklessness of 
a machine : 

(JVa + 0.llc)tHank^ ^r.p.m. 10~ 6 = Kk (32) 

The value of Kk varies as below : 
Kilowatts of machine : Up to 15 30 60 100 500 1000 or over. 
Kk— 80 70 60 50 40 35 

field Magrnet. — Cores of circular cross section are most economical 
of wire in the field windings, and a square cross section is next best in this 
respect. The temperature rise is greater, however, in a round coil of given 



PRACTICAL DYNAMO DESIGN. 365 

magnetizing power than in a square one, the cross section of the core and 
length of coil along the core being the same in both cases. Round coils are 
easier to wind, and are usually preferred. 

The length of a magnet core from the yoke to the pole-shoe or beginning 
of polar extensions, i.e., the space available for windings, parallel to the 
flux path in the core, may be roughly estimated for preliminary laying-out 
as follows : 

im= 9ow^iff) (33) 

The trial core length obtained by means of this formula will usually require 
revision in order to obtain the proper radiating surface for the coils. 

The magnetic density in field-magnet cores ranges from 90,000 to 100,000 
lines per square inch for cast steel, and from 100,000 to 110,000 for sheet 
steel. The density in magnet yokes ranges from 35,000 to 45,000 maxwells 
per square inch in cast iron, and 85,000 to 95,000 for cast steel. In railway 
motors and others of extraordinarily light weight, the yoke density is con- 
siderably higher than in stationary machines ; the core density is also 
somewhat higher, but the diiference is not so great as in the yoke. 

The density is not uniform throughout the length of path in the core, nor 
is it so in the yoke, but for convenience the maximum density is assumed 
to exist throughout the length of each path. 

Leakage of magnetic lines between adjacent poles and between each pole 
and the yoke surfaces makes the flux in the field magnet considerably 




Fig. 40. 

greater than that in the air-gap. The relation between the magnet -core 
flux and the air-gap flux is 

The value of v varies widely with different types of machines and different 
sizes of a given type. For well-designed machines of conventional tvpes it 
may be assumed tentatively to have the values given in Table X. It is con- 
siderably higher for poor designs. In the absence of data from existing 
machines of the type being designed, the field magnet may be proportioned 
on the basis of the values in Table X, page 376, tentatively, and the leakage 
roughly checked up as follows: 

Lay out to a rather large scale two poles of the machine and the corre- 
sponding portion of the yoke, as shown in Fig. 40 for a circular yoke. The 
average length of the leakage path between the upper surface of the polar 
extension and the inner surface of the yoke will be about as indicated by 
the dotted line Z, and the length of the leakage path between the neighbor- 
ing polar extensions will be about as shown by the line Z x . The mean 
length of the leakage path between the flanks of neighboring pole-ends is 
practically equal to the distance between the centers of the two measured 
along a circular arc concentric with the armature ; represent it by Z 2 . The 
mean length of the leakage path between each pole-piece flank and the yoke 
surface lying between x and z may be called equal to Z. The maximum flux 
in the magnet core will be approximately as given by the equation, 

♦.= . + 3.2* ( *A+A+A 3 + A i + ±A_ l + S _A,j . . m 

Field-Jftag-net Excitation. — In order to estimate beforehand the 
excitation required by the machine, the quality of the iron and steel to be 



366 



DYNAMOS AND MOTORS. 



used in its construction should be known. In the absence of such data 
however, the curves in Fig. 41 will serve for estimates. 



140 



130 



120 



110 



100 



90 



£ 80 



Ampere-turns per inch of length 

500 1000 1500 



o 



o 



70 



.9 6° 
«50 



50 100 150 

Ampere^turns per inch of length 

Fig. 41. 

The flux in the air-gap of a dynamo at no load is 
60 q Ew 10 8 



The flux at full load is 



*n = 



* = 



pNcT.p.m. 



2000 















































































































































rr s 


:<u^ 


































r«Vi 


uyp 


































-^ 


s^ 




































^jcMV 




































/ 








































/- 






































y 








































/ 






































/ 








































/ 






































/ 








































? 


















wr^ 


SC2 


te 


















/ 
















Wj 




















/ 
















*\c^ 


































5V 


2*V 












































































^ 






























1 










\/ 






^,e* 


\ 






























/ 




































/ 






^Q.T& 
































/ 








































/ 






































/ 




y 




































/ 


j 








































/ 








































, 




































> 


• 






































' 


/ 






































/ 


/ 






































/ 








































! 








































• 








































J 






































I 
























































































































I 


/ 






































/ 


















































































' 






















































































































1 


































































































- 






































L* « 






































fjgz 




















































































































X 






































y 






































} 








































/ 








































/ 






































/ 








































/ 














































































/ 








































J 








































/ 






































. 


/ 






































/ 
















































































1 








































1 








































i 









































GOg^^ + ^/q)^ 
p No r.p.m. 



200 

(35) 
(36) 



PRACTICAL DYNAMO DESIGN. 367 

For a motor the flux is the same at full load as at no load, except in special 
cases where a series winding is used in order to start a heavy load, and ex- 
cepting series- wound motors. The maximum air-gap flux for a motor haying 
to start under a load is 

no 11 

** = 117 pia#. ' < 3?) 

The full-load ampere-turns per pole for a dynamo or motor are F-\- Fr. 
F ' = Fa + Ft + F g + F P + Fm -f F y ; Fa =f a £a -J- 2 ; Ft = /t h ; F P =f p L P ; 

Fm '^zjm Lrn ) -by ZZZJy ±jy — 2. 

The ampere-turns per inch for the armature teeth will be the mean be- 
tween the ampere-turns per inch required to produce the density at the tops 
and those required to produce the density at the roots — not the ampere- 
turns required to produce the average density in the teeth. The approxi- 
mate density at th© roots of the armature teeth will be, at full load, 

and the approximate density at the tops of the teeth will be 

b t , = — — ^ o.mm "\ (39) 

Wa (nDa — S Nt) ( - + sr^ ) 

\P T Dp ] 

As some of the flux passes to the armature core body through the slots 
and ventilating spaces, the actual densities in the roots and tops of the teeth 
are less than the approximate densities given by the above formulas. The 
actual densities cannot be computed directly, but may be derived from the 
relation between the actual and approximate densities, which is as follows: 



B/=B T + 3.192/ T [^(l+f)-.l] 



(40) 



Since the formula cannot be transposed to solve for B T because B T and/ T 
are interdependent and vary at different rates, a table should be prepared 
showing values of B/ corresponding to different values of f T at different 
ratios of s -f- t and Wa -~ wa. The preparation of such a table is greatly 
facilitated by first preparing a table of values for 

representing this expression by k T , and thereby reducing eq. (40) to 

B/=B T -r-* T /r ( 41 > 

Table XI, page 377, gives values for k T for practical ranges of values for the 
two ratios mentioned. From eq. (41) and curves such as those in Fig. 41, a table 
of corresponding values for B T ' and/ T is easily prepared. From such a table 
the value of / T should be ascertained for the root and top of the tooth and 
also for two or three equidistant intermediate points between the root and 
top ; the average of these will be the working value. 
The ampere-turns per pole required by the air-gap will be 

f.'~ °' 3133 * (42) 



<^+*<^>0§f + *') 



368 



DYNAMOS AND MOTORS. 



Table IX, page 376, gives values of k g2 and Fig. 42 gives those of k h within ordi- 
nary ranges. The constant k g2 is merely the number which, multiplied by 
the air-gap length, gives the extent to which the air-gap dimension parallel 
to the shaft is increased by the bowing outward of the magnetic flux in pass- 




Slot 
Air-gap 



Pig. 42. 



ing from the pole-face edges to the armature core teeth. The constant k$ is 
the proportion of the physical air-gap length, 6, by which the gap is increased 
effectively by the passage of flux into the sides of the armature core teeth. 
This has been taken from Mr. F. W. Carter's article in the Electrical World 
and Engineer for Nov. 30, 1901. 

The value of F r cannot be predetermined with any approach to accuracy 
unless one has data from existing machines of corresponding type and out- 
put. The following empirical formula will serve to estimate roughly the 
value of F + Fr for modern American dynamos and non-reversing motors : 



PRACTICAL DYNAMO DESIGN. 369 

j. + jR . = (0-g-0-»»>fcM + J F2+ ^UN. y , _ (43) 

For reversing motors, 

0£4rUNc\2 (43a ) 



F+Fr= Jf* + / 0-6«M*JVc \ 



The no-load excitation of a shunt-wound dynamo need not be predeter- 
mined. The no-load excitation of a compound-wound dynamo is 

Fg ~ Fdo -f- Fto -f- Fgo -\- Fpo -j- Fmo -\- Fyo* 

The ampere-turns of the several parts of the magnetic circuit are deter- 
mined as in the case at full load, taking into account the differences in 
magnetic density in each part. 

After the first machine of a given type has been constructed, with the 
exception of the field-magnet coils, it should be tested with temporary 
exciting coils ; the results of these tests should be taken as the foundation 
of the magnet coil calculations. 

JF ield-UIagmet Winding's. — The field winding of a series or shunt- 
wound dynamo must be capable of giving the excitation required at full 
load. 

The field winding of a shunt-wound motor must give the excitation re- 
quired at the proper full-load speed. 

The field winding of a series-wound motor must give the excitation re- 
quired to produce the starting flux, 4> T . 

The shunt winding of a compound-wound dynamo must give the excita- 
tion required at no load ; the series winding must give the difference be- 
tween this and the excitation required at full load. 

The shunt winding of a compound-wound motor must give the excitation 
required at normal no-load speed ; the series winding must give the differ- 
ence between this and the excitation required to produce the starting flux, 

*T. 

The surface of any field magnet coil on a dynamo or motor of open con- 
struction (non-enclosed frame giving the external air free access to the 
windings), should be 

L fG— —jj- (44) 

r being the resistance of the coil when warm. For enclosed or poorly ven- 
tilated frames, the coil surface per watt per degree of temperature rise 
must be determined by trial ; no general rule will apply. In all cases 9/ 
should not exceed 70°. 

The proper size of wire to be used in a shunt field coil is approximately 
given by 

d 2 - ^fr + TA) (45) 

e 

Should the calculated value of d 2 not correspond with any standard size, the 
nearest standard size should be adopted and the depth of the winding ad- 
justed to suit it by transposing eq. (45) and solving for A, thus : 

d 2 e 



Fsh 



-9 



A = — (46) 

7T 

See also Magnet Windings, page 112. 

The minimum number of turns per pole for the series coils of a com- 
pound-wound machine is 



CF-\- Fr — Fah 



Turns : 



\ 



I F -\- Fr — Fah 



(short shunt) 



(long shunt) 



(47) 



370 



DYNAMOS AND MOTORS. 



The cross section of the series conductor need not exceed 0015 sauare 
inches per ampere actually carried by the coil, and should not be less tian 
?hTheft q ing 1 : e mCh Pei ' amP<3re ordi * aril y J " will be finally determined by 

ti™K b ° th f the Seiie . S and f hu ?i 3 eM ma g net coils, the maximum possible 
number of ampere-turns should be made from 10% to 15% greater tEanth« 
calculated maximum in order to provide a margin fol -differenced Tin the 
?r U epanciesf C ° PPer and ^ USed ' aS Wel1 M othw ^?onteol2b£ at* 




1H.P. 



Fig. 43, 



Efficiency.-— Efficiencies. range from 60% to 95#i SLOonrdi^tr +r» fv,<* «,v« ~o 
the machine and the character of service. Table XII plgefr'^ves aver 
l&V„V UeS / 0r or ? i,lar y constant-potential dynamos, and *?ig. 43 gives simil 

wPSStiSSS^KXttSS!"- Traction and "ASK^SSi 

Procedure in raying- out a Desig-n.— The following will be 
Receding pages :° US p, ' ocedure in H-Hjl^ft. method described in the 

Determine 

1. A trial polar bore, eq. 8 or 9 or 10. 

Type of armature winding ; number of paths. 
Number of poles ; eq. 6, for lap-wound machines. 
Ratio of pole-face span : pole pitch (i//). 
Maximum pole-face width ( W P < lech Dp). 
. Air-gap, eq. 28 ; the armature diameter follows. 
7. Turns per armature coil, Table V. 
8 Trial size of conductor, Table VI. 



2. 
3. 
4. 

5. 



PRACTICAL DYNAMO DESIGN. 



371 



9. Size of coil slot, based on number of conductors per slot, either 
Table III or eq. 13, and rules s < 25 and s = — to — . 

10. Possible number of coil slots, eq. 11 ; hence, total number of arma- 
ture conductors, keeping in view type of winding, eq. 2. 

11 Corrected pole-face density, eq. 30. 

12! Field-distorting armature reaction, eq. 31 ; if kr comes out too 
small ' the polar bore must be increased, thereby increasing the pole-face 
density and air-gap ; then solve eq. 31 for Nc, taking the nearest smaller 
value that will fit the winding. . l. ^ 

13. Corrected pole-face width, by solving eq. 29 for W P ; if the result 
^ kch D P , accept it ; if not, take a still larger polar bore, with the corre- 
sponding air-gap, and start over from Determination No. 11. 

14. Net axial iron measurement in armature, eq. 12. 

15. Gross length of armature core (= W P + 2bto W P + 4 5) ; the differ- 
ence between this and the net iron to be occupied by ventilating ducts. 

16. Number of armature coils ; check by Table I\ roughly ; a discrep- 
ancy of 25% is not prohibitive. , _ . _ , 

17. Diameter of commutator barrel, eqs. 21 and 22 ; Dk should never ex- 
ceed 0.9 Da, and 0.7 Dais an excellent limit ; if the diameter comes out too 



polar 

revising the air-gap by eq. 28. 

18. Complete commutator and brush dimensions, eqs. 25, 26, and 27. 

19. Probable tendency to sparking, eq. 32 ; if Kh is excessive, and the 
turns per coil cannot be reduced without entailing an unwieldy number of 
coils, the polar bore must be increased in order to permit reducing the 
length of the armature core, the determinations being revised from No. 11 
after finding the new air-gap, eq. 28. 

20. Armature losses with respect to heating, eq. 15 et seq. ; if PjJ ex- 
ceeds the limit set by eq. 14, and cannot be brought within the limit by re- 
ducing the hole in' the center of the core, the ventilating ducts may be 
reduced sufficiently to accomplish the result ; if not, and if Wa cannot be 
sufficiently increased on account of eq. 32, the polar bore must be increased, 
the corresponding air-gap adopted, and the determinations revised, begin- 
ning with No. 11. 

Having progressed this far, the remainder of the design is straight work, 
only a slight revision of the trial magnet core length being probably neces- 
sary to obtain the minimum quantity of field copper within the heating 
limit. 

TABLE I. 

Values of Uch. 



Poles. 


yfj = 0.666. 


v// = 0.7. 


xjj = 0.72. 


1// == 0.75. 


2 
4 
6 


0.866 

0.5 

0.342 


0.891 

0.5225 

0.3584 


0.9048 
0.5358 
0.3681 


0.9239 
0.5556 
0.3827 


8 
10 
12 


0.2588 
0.2079 
0.1736 


0.2714 
0.2181 

0.1822 


0.279 

0.2244 

0.1874 


0.2903 
0.2334 
0.1951 


14 
16 
18 


0.149 

0.1305 

0.1161 


0.1564 

0.137 

0.1219 


0.1609 
0.1409 
0.1253 


0.1676 
0.1467 
0.1305 


20 
22 
24 


0.1045 
0.0949 
0.0872 


0.1097 
0.0998 
0.0915 


0.1129 
0.1026 
0.0941 


0.1175 
0.1069 
0.0979 



372 



DYNAMOS AND MOTORS. 



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PRACTICAL DYNAMO DESIGN. 



373 



TABLE III. 
Trial Armature Coil Slot Depth 0. 



Core Diameter. 


Slot Depth. 


Core diameter. 


Slot Depth. 


6 

7 


i 


10* 

11 

11* 


If 


8 
8* 


I 

B 


12 

12* 

13 


it 


9 
10 


1 

It 1 * 


13* 

14 

15 


1A 

ii 5 * 
if 



TABLE IV. 
Trial Values for Minimum lumber of Armature Coils. 

Formula : N, = 0.8 p°' 8 X \A#X ^/KW.* 
The numbers in the table are values of \JE x \J KW.* 



KW* 


125 volts. 


250 volts. 


600 volts. 


1 


11.2 


15.8 


24.5 


2 


14.1 


19.9 


30.9 


3 


16.1 


22.8 


35.3 


4 


17.8 


25.1 


38.9 


5 


19.1 


26.9 


41.9 


6 


20.3 


28.7 


44.5 


8 


22.4 


31.6 


49. 


10 


24.1 


34.1 


52.8 


15 


27.6 


39. 


60.4 


20 


30.4 


42.9 


66.5 


25 


32.7 


46.2 


71.6 


30 


34.7 


49.1 


76.1 


40 


38.2 


54.1 


83.8 


50 


41.2 


58.2 


90.2 


60 


43.7 


61.9 


95.9 


75 


47.1 


66.7 


103.3 


100 


51.9 


73.4 


113.7 


125 


55.9 


79. 


122.5 


150 


59.4 


84. 


130. 


200 


65.4 


92.5 


143. 


250 


70.4 


99.6 


154. 


300 


74.8 


105.8 


164. 


400 


82.4 


116.5 


180. 


500 


88.7 


125. 


194. 


600 


94.3 


133. 


207. 


700 


99.3 


140. 


218. 


800 


103.8 


147. 


227. 


1000 


112. 


158. 


245. 



*KW. = Kilowatts output of dynamo or intake of motor. 
For;? = 2 4 6 8 10 12 14 

0.8p°- 8 = 1.4 2.4 3.35 4.2 5 6.8 6.6 



1.6 
73 



374 



DYNAMOS AND MOTORS. 



TABLE V. 

Trial Values for Maximum Allowable Number of Turns 
per Armature Coil. 

Formula : t 2 :5 240 q ~ iap. 



Lap 
Winding. 


Two-path Windings. 


Turns per 
Coil. 


p — q. 


p =z 4. 


p = 6. 


p = 8. 


t 


ia 


Id 


ia 


id 




240 


120 


80 


60 


1 


60 


30 


20 


15 


2 


26 


13 


9 


6.6 


3 


15 


7.5 


5 


3.75 


4 


9.6 


4.8 


3.2 


2.4 


5 


6.6 


3.3 


2.2 


1.66 


6 


4.9 


2.4 


1.6 


1.22 


7 


3.75 


1.87 


1.25 


0.93 


8 


3 


1.5 


1 


0.75 


9 


2.4 


1.2 


0.8 


0.6 


10 


1.8 


0.9 


0.6 


0.45 


11 


1.66 


0.83 


0.55 


0.42 


12 


1.42 


0.71 


0.47 


0.35 


13 


1.22 


0.61 


0.41 


0.3 


14 


1.06 


0.53 


0.35 


0.26 


15 



PRACTICAL DYNAMO DESIGN. 



375 



TABLE VI. 
Trial Value* for Carrying- Capacity of Armature Conductors. 

2 or 4 Wires in Parallel Considered a Single Conductor. 



Round Wires, 


Drawn to B. & S. Gauge. 


Rectangular Conductors. 




2 

in par- 
allel. 


4 

in par- 
allel. 


Da X r.p.m. = 


Da X r.p.m. 


= 


Single. 


4000 to 


8000 to 


10,000 to 


15,000 to 


20,000 to 








6000. 


10,000. 


12,000. 


17,000. 


22,000. 


No. 


No. 


No. 


Amperes. 


A 


A 




20 






2 


2* 


,d 


19 




. . 


2i 


3i 


q 


cd 


.9 


18 


• • 


• • 


3 


4 




CD 
U 


CD 


17 
16 


20 
19 


• • 


4 
5 


5 
6 


B 


c3 


c« 

S3 


15 


18 


• • 


6 


n 


CO 

u 
CD 


00 

U 

CD 


■ 
CD 


14 


17 


20 


7i 


9i 


ft 


Pi 


ft 


13 


16 


19 


9 


111 


CD 


CD 


CD 


12 


15 


18 


11 


14 


cd 

ft 


u 
CD 

ft 


CD 

ft 


11 


14 


17 


13* 


17* 


! 


i 


a 

oB 


10 


13 


16 


17 


21* 








9 


12 


15 


21 


26* 


I 


<N 


1 


8 


11 


14 


26 


33 


o 


O 


o 


7 


10 


13 


32| 


40 


>> 


£> 


>> 


6 


9 


12 


40 


50 


'35 




1 




8 


11 


52 


66 


CD 


CD 

T3 


CD 




7 


10 


65 


80 


43 


43 






6 


9 


80 


100 


a 

CD 
U 
U 


CD 


CD 
M 

N 






8 


104 


132 





3 


S3 






7 


130 


160 


O 


o 


O 






6 


160 


200 









376 



DYNAMOS AND MOTORS. 



TABLE VII. 

From " The Dynamo," by Hawkins & Wallis. 
Values of U 9 . 



a 


*•■* 


| =1 0. 


I= 12 - 


*-» 


I *>*» 


0° 
10° 
20° 

30° 

40° 
50° 


1.95 
1.85 
1.75 

1.66 
1.58 
1.52 


2.18 
2.05 
1.95 

1.84 
1.75 
1.666 


2.38 
2.23 
2.10 

1.98 
1.S9 
1.80 


2.55 
2.38 
2.25 

2.12 

2.00 
1.90 


2.7 

252 

2.38 

2.24 
2.12 
2.00 



TAJBI.E VIII. 

Barrel Armature Winding* Constants. 



Poles = 


4 


6 


8 


10 


12 


14 


16 


18 


20 


24 


hw = 


0.8 


0.56 


0.42 


0.36 


0.3 


0.256 


0.225 


0.2 


0.18 


0.15 



TABLE IX. 

From " The Dynamo," by Hawkins & Wallis. 
Values of U gt . 



JVa—W P _ 



1 


1.5 


2 


2.5 


3 


3.5 


0.74 


1.0 


1.2 


1.38 


1.54 


1.68 



4 
1.8 



T4BIE X. 
Averag-e Mag-netic L^aka-je Coefficients. 



Kilowatts = 


10 


25 


40 


50 


75 


100 


200 


300 


500 


1000 


v — 


1.35 


1.3 


1.27 


1.25 


1.23 


1.2 


1.18 


1.15 


1.13 


1.12 



PRACTICAL DYNAMO DESIGN. 



577 



TABLE VI. 
Values of k r . 



s 


»s=ua 


1.17 


1.18 


1.19 


1.20 


1.22 


1.24 


T 


Wd 














0.70 


3.10 


3.16 


3.21 


3.26 


3.32 


3.43 


3.54 


0.75 


3.29 


3.34 


3.40 


3.45 


3.51 


3.62 


3.73 


0.80 


3.47 


3.53 


3.59 


3.64 


3.70 


3.82 


3.93 


0.85 


3.66 


3.72 


3.78 


3.84 


3.89 


4.01 


4.13 


0.90 


3.84 


3.90 


3.96 


4.02 


4.09 


4.21 


4.33 


0.95 


4.03 


4.09 


4.15 


4.21 


4.28 


4.40 


4.53 


1.00 


4.21 


4.28 


4.34 


4.40 


4.47 


4.60 


4.72 


1.05 


4.40 


4.46 


4.53 


4.59 


4.66 


4.79 


4.92 


1.10 


4.58 


4.65 


4.72 


4.78 


4.85 


4.98 


5.12 


1.15 


4.77 


4.84 


4.91 


4.97 


5.04 


5.18 


5.32 


1.20 


4.95 


5.02 


5.09 


5.16 


5.23 


5.37 


5.52 


1.25 


5.14 


5.21 


5.28 


5.35 


5.43 


5.57 


5.71 


1.30 


5.32 


5.40 


5.47 


5.54 


5.62 


5.76 


5.91 


1.35 


5.51 


5.58 


5.66 


5.73 


5.81 


5.96 


6.11 


1.40 


5.69 


5.77 


5.85 


5.92 


6.00 


6.15 


6.31 


1.45 


5.88 


5.96 


6.04 


6.11 


6.19 


6.35 


6.51 


1.50 , 


6.06 


6.14 


6.22 


6.30 


6.38 


6.54 


6.70 


1.55 


6.25 


6.33 


6.41 


6.49 


6.57 


6.74 


6.90 


1.60 


6.43 


6.52 


6.60 


6.68 


6.77 


6.93 


7.10 


1.65 


6.62 


6.70 


6.77 


6.87 


6.96 


7.13 


7.30 


1.70 


6.80 


6.89 


6.98 


7.06 


7.15 


7.32 


7.49 


1.75 


6.99 


7.08 


7.17 


7.25 


7.34 


7.52 


7.69 


1.80 


7.18 


7.26 


7.35 


7.44 


7.53 


7.71 


7.89 


1.85 


7.36 


7.45 


7.54 


7.63 


7.72 


7.91 


8.09 


1.90 


7.55 


7.64 


7.73 


7.82 


7.92 


8.10 


8.29 


2.00 


7.92 


8.01 


8.11 


8.20 


8.30 


8.49 


8.68 



tibli: XII. 
Average Dynamo Efficiencies. 







Appropriate Distribution of Losses 




BO 




in Per Cent. 




. « 


«a 




'd . 




PJ o 


68 


© P 

© © 


Armature Losses. 


.2 w> 


ri 


%* 


O 


fe 3 




fa a 


o 










©T3 


■4-» 
© 


« 2 


M 






fao 






Copper. 


Iron. 




fa 


h} 


30 


90 


4.0 


3.0 


2.5 


0.5 


10 


40 


90.5 


3.8 


2.8 


2.4 


0.5 


9.5 


50 


91 


3.6 


2.7 


2.3 


0.4 


9 


75 


91.5 


3.4 


2.5 


2.2 


0.4 


8.5 


100 


92 


3.2 


2.4 


2.0 


0.4 


8 


200 


93 


2.7 


2.15 


1.8 


0.35 


7 


300 


93.5 


2.5 


2.0 


1.65 


0.35 


6.5 


500 


94 


2.3 


1.8 


1.55 


0.35 


6 


750 


94.5 


2.0 


1.7 


1.5 


0.3 


5.5 


1000 


95 


1.8 


1.5 


1.4 


0.3 


I 5 



378 TESTS OF DYNAMOS AND MOTORS. 

TESTS OF DYNAMOS AND MOTORS. 

Revised by Cecil P. Poole and E. B= Raymond 

All reliable manufacturers of electrical machinery and apparatus are now 
provided with the necessary facilities for testing the efficiency and other 
properties of their output, and where the purchaser desires to confirm the 
tests and guaranties of the maker, he should endeavor to have nearly, and 
in some cases all such tests carried out in his presence at the factory, unless 
he may be equipped with sufficient facilities to enable him to carry out like 
tests in his own shops after the apparatus is in place. 

Some tests, such as full load and overload, temperature, and insulation 
(except dielectric) tests are best made after the machinery has been installed 
and is in full running order. 

Owing to the ease and accuracy with wmich electrical measurements can 
be made, it is always more convenient to make use of electrical driving 
power for dynamos, and electrical load for the dynamo output, and in the 
case of motors, a direct-current dynamo with electrical load makes the best 
load for belting the motor to. 

No really accurate tests of dynamo efficiencies can be made with water- 
wheels, and only slightly better are those made by steam-engines, owing 
to unreliability of friction cards for the engine itself and the change of fric- 
tion with load. 

Where it is necessary to use a steam-engine for dynamo testing, all fric- 
tion and low load cards should be taken with the steam throttled so low as 
to cut off at more than half stroke, and to run the engine at the same speed 
as when under load. 

The tests of the engine as separated from the dynamo are as follows : — 

a. Friction of engine alone. 

b. Friction of engine and any belts and countershaft between it and the 
dynamo under test. 

Consult works on indicators and steam-engines for instructions for deter- 
mining power of engines under various conditions. 

The important practical tests for acceptance by the purchaser, or to deter- 
mine the full value of all the properties of dynamos and motors, are to learn 
the value of the following items : — 

Rise of temperature under full load. 

Insulation resistance. 

Dielectric strength of insulation. 

Regulation. 

Overload capacity. 

Efficiency, core loss. 

Bearing friction, windage and brush friction. 

I 2 R loss in field and field rheostat, 
I 2 B loss in armature and brushes. 

Note. — If a separate exciter goes with the dynamo, its losses will be 
determined separately as for a dynamo. 

Methods of determining each of the above-named items will be described, 
and then the combinations of them necessary for any test will be outlined. 

Temperature.— -The rise of temperature in a dynamo, motor, or 
transformer, is one of the most important factors in determining the life of 
such piece of apparatus; and tests for its determination should be carried 
out according to the highest standards that can be specified, and yet be 
within reasonable range of economy. The A. I. E. E. standards state the 
allowable rise of temperature above surrounding air for most conditions, 
but special conditions must be met by special standards. For instance, no 
ordinary insulation ought to be subjected to a degree of heat exceeding 
212° F., or 100° C. And yet in the dynamo-room of our naval vessels the 
temperature is said to at times reach 130° F., or even higher, which leaves a 
small margin for safety. It is obvious that specifications for dynamos in 
such locations should call for a much lower temperature rise in order to be 
safe under full load. 

For all practical temperature tests it is sufficient to run a machine under 
its normal full-load conditions until it has developed its highest temperature, 
although at times a curve of rise of temperature may be desired at various 
loads. 



TEMPERATURE. 379 

Most small dynamos, motors, and transformers, up to, say, 50 K.W., will 
reach maximum temperature in five hours run under full load, if the tem- 

Eerature rise is normal ; but larger machines sometimes require from 6 to 18 
ours, although this depends quite as much on the design and construction 
of the apparatus as on size, as, for instance, the 5,000 h.p. Niagara Falls Gen- 
erators reach full temperature in fiv r e hours. Temperature tests can be 
shortened by overloading the apparatus for a time, thus reaching full heat 
in a shorter period. 

On dynamos and motors the temperatures of all iron or frame parts, com- 
mutators, and pole-pieces, have to be taken by thermometer laid on the 
surface and covered by waste. Note that when temperatures are taken 
with the machine running, care must be taken not to use enough waste to 
influence the machine's radiation. Where there are spaces, as air spaces, 
in armature cores or in the field laminations, that will permit the insertion 
of a thermometer, it should be placed there. Temperature of field coils 
should be taken by thermometer laid on the surface and covered with waste, 
and by taking the resistance of the coils first at the room temperature and 
again while hot immediately after the heat run. Temperature rise of arma- 
ture windings can be taken by surface measurement and by the resistance 
method also ; although being nearly always of low resistance, very careful 
tests by fine galvanometer and very steady current are required in order to 
get anything like accurate results. 

The formula for determining the rise of temperature from the rise of 
resistance is as follows : 

Temperature by rise in resistance; for copper. — The in- 
crease in resistance due to increase in temperature is approximately 0.4% 
for each degree Cent, above zero, the resistance at zero being taken as the 
base. If then 

t x = temperature of copper when cold resistance is measured (Cent.), 
R x = resistance at temperature t lt 

t 2 — temperature of copper when hot resistance is taken, 
i?2 = resistance at temperature t 2 , 
Then first reducing to zero degrees, we have 

p — A n \ 

M ° - 1 + 0.0042 t t ' ' ' ■ (1) 

The increase in resistance from to t t degrees is i? 2 — i? , and hence we 
have for final temperature, 

t 2 = B2 ~ B ° + 0.0042 (2) 

Substituting (1) _ i? 2 (1 -f 0.0042 t x ) — i? t 

2_ 0.0042^ " (3) 

It is often convenient to correct all cold resistances to a temperature of 
20° C, in which case we first reduce to zero and then raise to 20°. 
The general formula for obtaining the resistance at t degrees is 

Rt = (1 + 0.0042 t) i? . 
Hence i? 20 = 1.084 K and in terms of the cold resistance at temperature t. 
_ (1.084 i? ) 

^2 - ( i _j_ 0.0042 t) (4) 

Formula (3) then becomes, when the cold resistance is at 20°, 

^ = ^f 2 X ^-6i42 = 258 5- 238 < 5 > 

As the first formula requires but oue setting of the slide rule, and the sub- 
traction of the constant 238 can usually be done mentally, the advantage of 
the temperature equation in this form is very great as regards both speed 
aud accuracy. 

The temperature coefficients most generally used are 

For copper 0042 

For iron 0045 

For German silver 00028 to .00044 



380 TESTS OF DYNAMOS AND MOTORS. 

The following parts should be tested by the resistance method and the 
surface method also : 
Field coils series, and shunt. 
Armature coils. In 3-phase machines, take resistance between all three 

rinss. 
The following parts should be tested by thermometer on the surface : — 

Room, on side opposite from steam-engine, if direct connected, and always 
in two or more parts of the room, within six feet of machine. 

Bearings, each bearing, thermometer held against inner shell, unless oil 
from the well is found to be of same temperature as the bearing. 

Commutators and collector rings. 

Brush-holders and brushes, if thought hotter than the commutator. 

Pole-tips, leading and following. 

Armature teeth, windings, and spider. 

Terminal blocks, for leads to switch-board, and those for leads from the 

brushes. 
Series shunt, if in a compound-wound machine. 
Shunt field rheostat. 

On transformers which are enclosed in a tank filled with oil/temperatures 
by thermometer should be taken on — 

Outside case, in several places. 

Oil, on top, and deeper by letting down thermometer. 
Windings, by placing thermometer against same, even if under oil. 
Laminations, by placing thermometer against same, even if under oil. 
Terminals. 

Room, as with dynamos and motors. 

Also resistance measurements of primary and secondary windings, from 
which the temperature by resistance can be calculated as shown. 

On transformers cooled by air forced through spaces between windings 
%nd spaces in laminations, temperatures by thermometer should be taken 
on — 

Outside frame. 

Air, outgoing from coils. 

Air, outgoing from iron laminations. 

Windings. 

Terminals. 

Room, in two or more places. 

Also resistance measurements, hot and cold, should be taken, from which 

rise of temperature, by resistance can be calculated. 
Finally, the cubic feet of air, and pressure to force same through spaces 

(easily measured by " U " tube of water), should be measured. 

When other fluids are used for cooling, such as water passing through 
piping submerged in oil, in which also the windings and core are submerged, 
or through windings of transformers themselves (made hollow for the pur- 
pose), the temperature of incoming and outgoing fluid should be measured, 
the quantity used and the pressure necessary to force it through the path 
arranged, besides the other points mentioned above. 

Careful watch of thermometers is necessary in all cases, as they will rise 
for a time and then begin to fall ; and the maximum point is what is wanted. 

British authorities state a definite time to read the thermometers after 
stopping the machine. 

Care must also be taken to stop the machine rotating as soon as possible, 
so that it will not fan itself cool. 

A handy method of constructing a curve showing the rise of temperature 
in the stationary parts of a machine at full load is to insert a small coil of 
fine iron wire in some crevice in the machine in the part of which the tem- 
perature is desired. Connect the coil with a mirror galvanometer and 
battery. 

The temperature coefficient of iron is high, and the gradual increase in 
resistance of the coil will cause the readings on the galvanometer to grow 
gradually less ; and readings taken at regular intervals of time can be 
plotted on cross-section paper to form a curve showing the changes in 
temperature. 



TEMPERATURE. 381 



Records of temperature test. —During all heat runs readings 
should be taken every fifteen (15) minutes of the following items: 

On direct and alternating current motors and generators — 
Armature, Volts (between the various rings where machine is more than 
single-phase, in the case of alternators, and between brushes, 
in the case of a D. C. machine). 
Amperes (in each line). 
Speed. 
Field, Volts. 

Amperes. 
On synchronous converters : — 
Armature, Volts (between all rings on A. C. end, and between brushes on 
D. C. end). 
Amperes, per line A. C. end, also D. C. end. 
Speed. 
Field, Volts. 

Amperes. 
On transformers, compensators, potential regulators : — 
Volts, primary. 
Volts, secondary. 
Amperes, primary. 
Amperes, secondary. 
Cycles. 

Amount and pressure of cooling-fluid (if any is used). 
On induction motors : — 

Volts, between lines. 
Amperes, in line. 
Speed. 
Cycles. 
Overload. —The A. I. E. E. standards contain suggestions for overload 
capacity (see page 303). 

The writer has uniformly specified a standard overload of 25% for 3 hours, 
and there seems to be no especial difficulty in getting machines for this 
Standard that do not heat dangerously under such conditions. 

Insulation test. — Insulation resistance in ohms is of much less im- 
portance than resistance against breakdown of the insulation under a 
strain test, with alternating current of high pressure. 

Make all insulation tests with a voltage as high, at least, as that at which 
the machine is to be worked. 

The following diagram shows the connections to be made with E some 
external source of E.M.F. The formula used is 
R =z resistance of voltmeter. 

E =: E.M.F. of the external source. mmror, 
e = reading of voltmeter connected as in wg. 

diagram. t/C\ i W n 
x=z insulation resistance in ohms. X--^ «BB— ■ 



x— insulation resistance in ohms. armature 



Then x : 



»(!-')• a^ y 



, — 4- 

FRAME 



According to the A. I. E. E. standards, 
the insulation resistance must be such that Fig. 1. Connections for volt- 
the rated voltage of the machine will not meter test of insulation re- 
send more than y^^s of the full-load cur- sistance of a dynamo. 
rent through the insulation. One megohm 

is usually considered sufficient, if found by such a test. Where one megohm 
is specified as sufficient, the maximum deflection that will produce that 
value, and that must not be exceeded in the test, may be found by the fol- 
lowing variation of the above formula : 

RXE 
~ 1,000,000 -f R 

Strain test. — The dielectric strength of insulation should be deter- 
mined by a continued application of an alternating E.M.F. for at least one 
(1) minute. The transformer from which the alternating E.M.F. ht takax* 
should have a current capacity at least four (4) times the amount oi current 




382 TESTS OF DYNAMOS AND MOTORS. 

necessary to charge the apparatus under test as a condenser. Strain tests 
should only be made with the apparatus fully assembled. 
Connect on a D.C. machine as in the following diagram. 

Strain tests should be made with a sine 
wave of E.M.F., or with an E.M.F. having 
/■Khini m w VM - tne same striking distance between needle 

rooaojjooo .so points in air. 

I >T> I Jpy See article 219 A. I. E. E. standards for 

X-^Tfuja J jL proper voltages. 

Regulation. — The test for regula- 
tion in a dynamo consists in determining 
its change in voltage under different 
FRAME loads, or output of current, the speed be- 

Fig. 2. Connections for strain ing maintained constant, 
test of dynamo or motor or The test for regulation in a motor 
transformer insulation. consists in determining its change of 

speedy under different applied loads, 
when the voltage is kept constant. 

Standards. — For full details of standards of regulation of different 
machines, see report of the Committee on Standardization of the A. I. E. E. 
at the beginning of this chapter. 

Regulation Tests, Dynamos, Shunt or Compound, and 
Alternators. 

The dynamo must be run for a sufficient length of time at a heavy load to 
raise its temperature to its highest limit ; the field rheostat is then adjusted, 
starting with voltage a little low, and bringing up to proper value to obtain 
the standard voltage at the machine terminals, and since a constant temper- 
ature condition has been reached, must not again be adjusted during the 
test. Adjust the brushes, in the case of a D. C. machine, for full-load con- 
ditions, and they should not receive other adjustment during the test. This 
is a severe condition, and not all machines will stand it ; but all good dy- 
namos, with carbon brushes, will stand the test very well, provided tne 
brushes are adjusted at just the non-sparking point at no load. 

Load is now decreased by regular steps, and when the current has settled 
the following readings are taken : — 

Speed of dynamo (adjusted at proper amount). 

Current in output (a non-inductive load should be used). 

If alternator, current in each line if more than single-phase. 

Volts at machine terminals. 

Amperes, field. 

Volts, field. 

Note sparking at the brushes (they should not spark any with carbon 

brushes) . 

Readings should be taken for at least ten intervals, from full load to open 

circuit (no load) ; and load should then be put on gradually and by the same 

steps as it was brought down ; and the same records should be made back 

to full-load point, and beyond to 25% overload. 

If the readings are to be plotted in curves, as they always should be, it 
will make little difference if the intervals or steps are not all alike ; and 
should the steps be overreached in adjusting the load, the load must not, in 
any circumstances, be backed up or readjusted back to get regular inter- 
vals or a stated value, as the conditions of magnetization change, and throw 
the test all out. In case the current is broken, or the test has to be slowed 
down in speed or stopped, it must be commenced all over again. Finally, 
when the curves are plotted, draw, in the case of a compound-wound ma- 
chine, a straight line joining the no-load voltage and the full-load voltage ; 
and the ratio of the point of maximum departure of the voltage from this 
line to the voltage indicated by the line at the point will be the regulation 
of the machine. 

The readings as obtained give what is called a field compounding curve. 
In the case of a shunt or separately excited machine, the procedure for the 
test is the same ; but when the curve is plotted, the regulation is figured as 
equal to the difference between the no-load voltage and full-load voltage, 
divided by the full-load voltage. The curve is called a characteristic in 
this case. 



DYNAMO EFFICIENCY. 383 

For alternators that are too large to apply actual load as suggested above, 
another "no-load" method commonly used with satisfactory results upon 
alternators designed upon the usual lines is to short-circuit the alternator ar- 
mature upon itself and determine the amperes in the field required to produce 
normal current in the armature so short-circuited, the speed of the machine 
being normal at the time ; call this current F. Take another reading of 
the field current required to produce normal voltage at the machine ter- 
minals, with the armature on open circuit and the speed normal ; call this 
current C. Then the current required in the field winding for full non- 
inductive load will be /= ViT2_j_ c*. 

Having calculated the value of this current, pass it through the field 
windings of the alternator with the armature on open circuit and running 
at normal speed, and read the volts V. Let E =. normal voltage, then the 

regulation = — = — >• 

The current F is called the " Synchronous impedance " field current, being 
so named by Mr. C. P. Steinmetz, who proposed and has used the above- 
described method. 

When regulation is desired for a power factor other than unity the field 
currents F and C must be combined at the proper angle corresponding to 
the power factor. For instance, for a power factor of (i.e., 90° lag) the 
field currents would be directly added. This method is used extensively 
and gives results agreeing very well with those of actual tests. 

Reg-illation Tests, Motors, Shunt. Compound, and 
Induction. 

After driving the motor under heavy load for a length of time sufiicient 
to develop its full heat, full-rated load should be applied, the field rheostat, 
if any is used, and brushes adjusted for the standard conditions ; then the 
load should be gradually removed by regular steps, and the following read- 
ings be made at each such step : — 
Amperes, input. 

Volts at machine terminals (kept constant). 
Watts, if induction motor. 
Speed of armature. 
Note sparking at brushes. 
Amperes, field (in D. C. machines). 
At least ten steps of load should be taken from full-rated load to no load. 
The ratio of the maximum drop in speed between no-load and full-load, 
which will be at full-load, to the speed at full-load, is the regulation of the 
motor. 

Efficiency Tests. Dynamos. 

The term efficiency has two meanings as applied to dynamos ; viz., electrical 
and commercial. The electrical efficiency of a dynamo is the ratio of elec- 
trical energy delivered to the line at the dynamo terminals to the total electri- 
cal energy produced in the machine. The commercial efficiency of a dynamo 
is the ratio of the energy delivered at the terminals of the machine to the total 
energy supplied at the pulley. Otherwise the electrical efficiency takes into 
account only electrical losses, while the commercial efficiency includes all 
losses, electrical, magnetic, and frictional. 

Core-lioss Test, and Test for friction and Windage. 

These losses are treated together for the reason that all are obtained at 
the same time, and the first can only be determined after separating out the 
others. 

A core-loss test is ordinarily run only on new types of dynamos and 
motors, but is handy to know of any machine, and if time and the facilities 
are available, should be run on acceptance tests by the consulting engineer. 
It consists in running the armature at open circuit in an excited field, driv- 
ing it by belt from a motor the input to which, after making proper deduc- 
tions, is the measure of the power necessary to turn the iron core in a field 
of the same strength as that in which it will work when in actual use. 



384 TESTS OF DYNAMOS AND MOTORS. 

Connect as in the following diagram, in wMcli A is the dynamo or motor 
under test, and B is the 

motor driving the arma- f ■ ^ 

ture of A by means of gk PjJrvJ • 

the belt. The field of A (M, field J^rAJ'* 1 motor field 

must, of necessity, be T^ / ~ ~ =1 .exciter 

separately excited, as LrV_J f^S I /SC\ rS? rfiJ *-^ 

its own armature circuit ~^£Z Y^Sy) ^X^^hM-^-^y 

must be open so that excite* V^X belt, \ y generator eor 

there may be no current uSHS?^- DR,VJNB W0T0R C0J5REN T 

generated in its conduc- mDER TES ' W0T0R - 

tors. Fig. 3. Connections for a test of core loss. 

The motor field is sep- 
arately excited and kept constant, so that its losses and the core loss of the 
motor itself, being constant for all conditions of the test, may be cancelled 
in the calculations. The motor B should be thoroughly heated ; and bear- 
ings should be run long enough to have reached a constant friction condi- 
tion before starting this test, so that as little change as possible will take 
place in the different "constant" values. It is necessary to know accu- 
rately the resistance of the armature, B, in order to determine its I 2 R loss 
at different loads, and to use copper brushes to practically eliminate the 
I i R of brushes. 

It is well to make a test run with the belt on in order to learn at what 
speed it is necessary to run the motor in order to drive the armature A at its 
proper and standard speed. 

Friction, core loss, and windage of motor. — The speed having 
been determined, the belt is removed, and the motor field kept at its final 
adjustment, and enough voltage is supplied to the motor armature to drive 
it free at the standard speed. The watts input to the armature is then the 
measure of the loss (I 2 R) in the motor armature plus the friction of its bear- 
ings, plus its windage, plus core loss, or the total loss in the motor at no 
load. This is called the " running light " reading. 

Friction and windage of dynamo. — After learning the losses 
in the driving motor, the belt is put on and the dynamo is driven at its 
standard speed without excitation, and in order to be sure of this a volt- 
meter may be connected across the armature terminals ; if the slightest 
indication of pressure is found, the dynamo field can be reversely excited, 
to be demagnetized, by touching its terminals momentarily to a source of 
E.M.F. Take a number of readings of the input to the motor in order to 
obtain a good mean, and the friction and windage of dynamo is then the 
input to the motor, less the " running light" reading previously obtained, 
the I 2 R of motor armature having been taken out in each case. 

Let P = watts input to motor, 

P,= PR loss in motor armature when driving dynamo, 
f = " running light " reading of motor, 
h = friction and windage of dynamo armature, 
P 2 = 1 2 R loss of motor armature when " running light," 
then A = p_ ( p 1+ /_p 2 ). 

II rush friction. — The friction of brushes is ordinarily a small portion 
of the losses ; but when it is desirable that it should be separated from other 
losses, it can be done at the same time and in the same manner as the test 
for bearing friction. The brushes can be lifted free from the commutator 
or collector rings when the readings of input to the driving motor for bearing 
friction are taken ; dropping the brushes again onto the commutator and 
taking other readings, the difference between these last readings and those 
taken with brushes off will be the value of brush friction. Note, that allow- 
ance must be made as before for increase of I 2 R loss in the motor armature. 

Test for core loss. — Having determined the friction and other losses 
that are to be deducted from the total loss, a current as heavy as will ever 
be used is put on the dynamo field, the motor is supplied with current 
enough to drive the dynamo at its standard speed, and the reading of watts 
and current input to the motor armature is taken. 

The dynamo field current is now gradually decreased in approximately 
regular steps, readings of the input to the motor being taken at each such 
step until zero exciting current is reached, when the exciting current is 
reversed and the current increased in like steps until the highest current 



DYNAMO EFFICIENCY. 



385 



reading is again reached. This may now be again decreased by intervals 
back to zero, reversed and increased back to the starting-point, which will 
thus complete a cycle of magnetization ; ordinarily this refinement is not, 
however, necessary. 

This test must always be carried through without stop ; and although it is 
desirable to make the step changes in field excitation alike, if the excitation 
be changed in excess of the regular step it must not be changed back for the 
purpose of making the interval regular, as it will change the conditions of 
the residual field. When the readings are plotted on a curve, regularity in 
intervals of magnetization is not entirely necessary. 

The following ruling makes a convenient method of tabulation : — 



Dynamo. 


Motor. 


Speed 


amperes 

in 

field 


Speed 


amperes 

in 

field 


amperes 

in 

armature 

i 


volts 

in 

armature 

e 


Constant 




Constant. 


Constant. 







Computations. 



Watts in 

armature, 

belt on 

P„ = ie 



Running 

light 

reading 

/ 



PR 

in arm, 
belt on 
Px ' 



PR 
in arm, 
belt off 

P% 



Core loss 
P t s-{Pi+f-PJ 



Plot on curve with exciting-current values on the horizontal scale, and 
the core loss on the vertical, and the usual core-loss curve is obtained. 

Separation of Core ILoss into Hysterenis and Eddr 
Current Lo*v 

Losses due to hysteresis and friction vary directly with the speed ; losses 
due to eddy currents vary as the square of the speed. 

Current and voltage must now be applied to the dynamo armature to 
drive it as a motor at proper speed, with the current in the separately 
excited field kept constant at proper value. Drive the motor (dynamo) at 
say two different speeds, one of which may be K times the other ; let 
P = total loss in watts, 
f x = loss in friction, 
H = loss by hysteresis, 
D rr loss by eddy currents, or 
P = /v, -f- H-\- D at the first speed, 
P. z=.'Kf y -f KH-\-K*D at second speed, 
KP — JtA -f kH+ KD, 
P 1 — KP=K*D — KD, 
P. — KPz^KDiK—l) 
n -P.-KP 



If K=2, then 



£>-. 



K(K-1) 
. Pi — 2P_ 



2 (2 — 1) 2 

Kapp and Housman separately devised the above method of separating 
the losses, but stated them somewhat differently. 

With the field separately excited at a constant value, different values of 
current are supplied to the armature at different voltages to drive it as a 
motor. The results are plotted in a ^urve which is a straight line, rising as 
the volts are increased. 



386 



TESTS OF DYNAMOS AND MOTORS. 



The following diagram shows how the losses are plotted in curves. The 
test as a separately excited motor is run at a number of different values of 
voltage and current in the armature, and the results are plotted in a curve 
as shown in the following diagram. The line a, 6, is plotted from the results 
of the current and volt readings. 

The line a, c, is then drawn parallel to the base, and represents the sum of 
all the other losses, as shown by previous tests, and they may be further 
separated and laid off on the chart. 

The triangle a, b, c, represents one-half of the value of the foucault cur- 
rent loss. . 

If another run be made with a different value of excitation, a curve, at, b t . 
or one below the original a, b, will be gotten, according to whether the total 
losses have been increased or decreased. 

If the higher values of current tend to demagnetize, by reason of the eddy 
currents in the armature, the curve a, 6, will curve upward somewhat at the 
upper end. .. , . 

Knowing the core-loss, friction and windage of a dynamo and the resis- 
tance of the various parts, the efficiency is quickly calculated, thus 
Let P = core-loss 4- friction (obtained as shown), 
V = voltage of armature, 
/ = current of dynamo armature, 
/i = current of dynamo field, 
R = resistance of armature and brushes, 
Rx = resistance of field. 
Then, considering the above as the only losses (i.e., neglecting rheostats, 
etc.), y 

Efficiency = Vi + pr + 1 J r^T ' 

This is a satisfactory method of getting the efficiency, but does not take 

in M load losses " if any 
should exist. 

The simplest method 
of determining the effi- 
ciency of a direct-current 
machine is to run it light 
as a motor, without load 
or belting or gearing, at 
its proper field strength 
and its proper speed and 
measure the input to 
the armature. From this 
value subtract the PR 
loss in the armature and 
the remainder is the core 
and friction loss. Know- 
ing this and the resis- 
tance of the remaining 
circuits, all the losses 
are known, and hence 
the efficiency can be cal- 
culated. This method is 
an accurate one and is 
easy to carry out. 

Another teat for 
efficiency. — If the dy- 
namo under test is not 
of too large capacity, and 
a load for its full output is available, either in the form of a lamp bank, 
water rheostat, or other adjustable resistance, then one form of test is to 
belt it to a motor. 

By separately exciting the motor fields, and running the motor free with 
belt off, its friction can be determined, and with the resistance of the arma- 
ture known, the input to the motor in watts, less the friction and the PR 
loss in its armature at the given load, is a direct measure of the power ap- 
plied at the pulley of the dynamo. The output in watts, measured at the 
dynamos terminals, then measures the efficiency of the machine. 




BRUSH FRICTION 



BERBtflCl ERICTION AND WINDAGE 



WETS IN ARMATURE' 



6? 



Fig. 4. 



Diagram showing separation of losses 
in dynamos. 



DYNAMO EFFICIENCY. 



38T 



Let P = watts input to motor, 

Pi— losses in motor, friction, Pit, and core-loss, 
P x == watts output at dynamo terminals. 
P 
% of efficiency = 100 X -p — ~- ;= commercial efficiency. 

Knowing the current flowing in the armature and in the fields, and also 
knowing the resistance of the same, the I 2 R losses in each may be calcu- 
lated, which, added to the output at the dynamo terminals, shows the total 
electrical energy generated in the 
machine. 

If a = the I 2 R loss in the armature, 
/ =the I 2 R loss in the fields. 

The electrical efficiency in per- 
centage will be 

100 x — 

The adjoining diagram shows the 
connections for this form of test. 

It must be obvious that a steam- 
engine, or other motive power that 
can be accurately measured, may be 
used in place of the electric motor ; 
but measurements of mechanical 
power are so much more liable to 
error that they should be avoided 
where possible. 

The only objection to this method 
is that the friction of the driving-motor varies with the load, and the loss 
in the belt is not considered. 




SENERATOfi 



WATER 
-^RHEOSTAT. 
=3 FOR LOAD 



Fig. 5. Connections for efficiency 
test of a generator, driven by an 
electric motor. 



Kapp'i Test with Two Similar Direct-Current Djnamoi, 

Where two similar dynamos are to be tested, and especially where their 
capacity is so great as to make it difficult to supply load for them, it is com- 
mon to test them by a sort of opposition method ; that is, their shafts are 
either coupled or belted together, the armature leads are connected in series, 
the field of one is weakened enough to make a motor of it ; this motor drives 
the other machine as a generator, and its current is delivered to the motor. 
The difference in currents between the two machines, and for exciting the 
fields of each, is supplied by a separate generator. 

The following diagram shows the method of connecting two similar 



SWITCH 




Fig. 6. Connections for Kapp's method of efficiency 
test of two similar dynamos. 



388 



TESTS OF DYNAMOS AND MOTORS. 



dynamos for Kapp's test. D is the dynamo ; M the machine with field 
weakened by the resistance R, that acts as a motor, and G is the generator 
that supplies the energy necessary to make up the losses, excitation and 
differences. 

Start the combination and get them to standard voltage, as shown by the 
voltmeter ; then take a reading of the current with the switch on b, and 
another with the switch on a. Let the first reading be m, and the second rf, 
and let x be the efficiency of either machine, then 

Per cent efficiency of the combination = 100 X -j-» and 



:V( 10 0X^). 



In using this formula the efficiency of the dynamo at its load is assumed 
the same as the motor at its simultaneous load, which is usually true above 
the | load point. The loss in motor-field rheostat should also be allowed for. 
Another similar method, called "pumping back ," is to connect the shafts 
of the two machines as before, by clutch or belt ; arrange the electrical 
connections and instruments as in the following diagram : 



A.M. 



A.M. 



V.M. 



n v.m, 




Fig. 7. Efficiency test of two similar dynamos. 



D is the dynamo under test ; M is the similar machine used as a motor ; 
and G is the generator for supplying current for the losses and differences 
between M and D. The speed of the combination, as well as the load on D, 
can be adjusted by varying the field of M. 

The motor, M, drives D by means of the shaft or belt connection. M gets 
its current for power from two sources, viz., G and D. In order to determine 
the amount of mechanical power developed by M, and also to be able to 
separate the magnetic and frictional losses in the two machines, a, core-loss 
test should have been made on the machine M at the same speed, current, 
and E.M.F. as it is to have in the efficiency test. The loss in the cable con- 
nections between M and D must also be taken into account, and is equal to 
the difference in volts between voltmeters c and 6, X the current flowing 
in ammeter n. 
Let V— E.M.F. of D, shown on c, 

V, — E.M.F. of M by vm. 6, 
V„ — E.M.F. of G by vm. a, 
I =z amperes current from D by am. n, 
7 / =c amperes current from G by am. I, 
I n = amperes current in M = I-\- /,, 
t = drop in connections between D and M = V — V m 
L = loss in connections between D and M = e X I t 
r = D's internal resistance, 
r x =: M's internal resistance, 

w r= core loss + armature loss -f field loss + friction of M in 
watts -f- L (loss in connections). 



ELECTRICAL METHOD OP SUPPLYING LOSSES. 389 



Then 

W = the useful output of D= V X /, 
Wj = energy supplied by G = V„ X T n 
W + W, = total energy supplied to M, 
7P" -f" FT/ — «* = energy required to drive D, 

% commercial efficiency of D == - 



I 2 r =. electrical loss in D, 
% electrical efficiency r= - 



W+ W, — w 



x 100. 



w 



^ + /v xioo. 

The other way of calculating the efficiency with this arrangement is to 
measure the output — W x from G, with full load on D. W x then is the 
losses of both machines under load ; and knowing the I 2 R loss in the arma- 
ture and field of each, the efficiency is quicklv and accurately calculated. 
This method is best, as no core loss is required, and includes the " load 



Electrical Method of Supplying* the losses at 
Constant Potential. 

Modification of <4 Kapp Method" by Prof. Wm. L. Puffer, from notes 

privately printed for the students of the Massachusetts Institute 

of Technology. 

Specification. 

Two similar shunt dynamos under full load, one as a motor driving the 
other as a loaded dynamo through a mechanical coupling. Mains at same 
voltage as dynamos, and only large enough to supply the full-load losses of 
both dynamos. 

Line up the two dynamos carefully, and mechanically connect them by 
a good form of mechanical coupling, strong enough to transmit the full load 
to the dynamo. 

Connect the field magnet windings of each machine to the supply mains, 
putting a suitable field rheostat in each. If desirable for any reason, the 
field of the dynamo may be left connected as designed ; but the field of the 
motor, which does not in any way enter as a quantity to be measured during 
the test, should be connected to the supply mains. 




Fig. 8. Diagram of Connections for Professor Puffer's Modifi- 
cation of Kapp's Dynamo Test. 

Method of Starting*. 

Close the field circuit of the motor, and by the motor starting rheostat 
gradually bring the motor up to full speed. The dynamo armature will be 
also at proper speed and on open circuit. Now close the dynamo field and 
adjust the field rheostat until the dynamo is at about normal voltage. 
Adjust the speed roughly at first by the use of the field rheostat of the 
motor, remembering that an added resistance will cause the speed to rise. 
Next see that the voltage of the dynamo is equal to that of the motor, or, 
in other words, that there is no difference of potential between -opposite 
sides of the main switch on the dynamo. Close this switch and there may, 
or may not, be a small current in the dynamo armature. Now carefully 



390 TESTS OF DYNAMOS AND MOTORS. 

increase the armature voltage of the dynamo, watching the ammeter, and 
weaken that of the motor ; a current will now from the dynamo to the 
motor, and the motor will transmit power mechanically to the dynamo. 

The current which was first taken from the supply wires to run the motor 
and dynamo armatures will increase somewhat. By a careful adjustment 
of the two rheostats and the lead on each machine, the conditions of full 
load of the dynamo may be produced. The motor is overloaded and its arm- 
ature will carry the sum of the dynamo and supply currents. Great care 
must be taken in adjusting the brushes of the macbines, because of great 
changes in the armature reactions which take place as the brushes are 
moved. It is well to remember that a backward lead to the motor brushes 
will increase the speed, as the armature reactions will considerably weaken 
the effective field strength. 

Cautions. 

The increase of speed will raise the dynamo voltage, and cause the cur- 
rent flowing in the armatures to greatly increase. A forward movement of 
the motor brushes will reduce both speed and current. A forward move- 
ment of the dynamo brushes will increase the armature reaction, and cut 
down the current through the armatures, while a backward movement will 
cause it greatly to increase. Very great care must be taken in adjusting 
the brush lead, as a movement of the brushes of either machine, which 
would be of little importance usually, will produce sometimes a change in 
current value equal to the full-load current. It is quite possible but poor 
practice to produce the load adjustment by use of the brushes alone. 

It is best to have ammeters of proper size in all circuits, but those actually 
required are in the dynamo leads and in the supply mains. A single volt- 
meter is all that is required. 

The field magnet circuits ought to be connected as shown, and the am- 
meters placed so that the energy in the fields does not come into the test of 
the losses in the armatures. The magnet of the machine under test, a 
dynamo in this case, should be under the proper electrical conditions for 
the load, yet not in the armature test, because the object of the test can best 
be made the determination of the stray power loss under the conditions of 
full load ; then having found this, assume the exact values of E, I, and 
speed, and so build up the data for the required efficiency under a desired 
set of conditions which might not have been exactly produced during the 
test. 

Immediately after the run, all hot resistances should be measured as 
rapidly and carefully as possible, to avoid any error due to a change in 
temperature. 

The energy given to the two armatures less the I 2 R in each armature, 
will be the sum of all the armature losses of the two dynamos under the 
conditions of the test, so that we measure directly the armature losses of 
the dynamos while fully loaded. 

It is evident that the two armatures are not under exactly the same con- 
ditions, except as to speed, for the dynamo armature w r ill have an intensity 

of magnetic field that will give an armature voltage of Vf + 7^ 2? ^4, while 

the motor will be weaker as Vf is the same for both armatures, and the 

motor armature voltage will be Vf — I a Bj t All the iron core losses will be 
made much greater in the dynamo than in the motor. The motor armature 
must carry a current equal to the sum of the dynamo and supply currents, 
and will get much hotter ; its reaction will also be greater, and there will be 
a tendency for greater sparking at the brushes. 

The total stray power thus obtained may be divided between the two 
armatures equally, but preferably in proportion to the armature voltages, 
unless the true law for the armatures is known. All resistances of wires, etc., 
must be noted and corrections applied, unless entirely negligible. 

Two 15-H.P. dynamos were tested by the class of '93, using this method. 
One of the full-load tests is here given as a sample of calculation. The 
exact rating of the dynamos is not known, but is nearly 45 amperes at 220 
volts, with the dynamo at a speed of 1600 r.p.m. 



ELECTRICAL METHOD OF SUPPLYING LOSSES. 391 

The averages of the observed readings taken during the test, and after a 
run of about five hours to become heated, was as below. 

Example of Calculation. 

(Connections as shown in Fig. 8.) 

Volts at supply point 220.3 

Amperes of 15.71 

Output of dynamo, amperes 45.80 

Dynamo field current . . . 1.945 

Speed 1594. 

To Measure Armature Resistance. 

Motor V— 1.952 J— 10.18 

Dynamo V — 2.406 7=10.08 

The motor field is out of the test while the dynamo field is in the test. 



Calculation. 

Watts supplied 220.3 X 15.71 = 3461. 
Dynamo armature R. = Motor armature R. = 

PadRad I 2 am Ram 

la = 45.80 -f 1.94 = 47.74 la = 45.80 + 15.71 =. 61.51 

47.742 x .2387 = 554 = Pa Rod 61.51 2 X .1918 =. 725.4 = Pa Ram 

Dynamo Field = 1.945 X 220.3 = 428.4 

Watts supplied = 3461 

Dynamo field = 428.4 

PR M = 725.4 

PR D — 554.0 

Total heat lost = 1697.8 1698 

Total stray power = 1763 watts, for both machines. 

Vad Vam 

Vt+IaRa Vt — IaRa 

47.74 X .2387 = 11.4 + 220.3 61.51 X .1918 = 11.8 -f 220.3 

= 231.7 = Vad. = 208.5 = Vam. 

Divide the total stray power between the two armatures as their arma- 
ture voltages. 

231.7 
Stray power of dynamo, 23 17 ■' 208.5 X 1763 = 928, 
Stray power of motor = 1763 — 928.0 r= 835.0. 
The quantity 928.0 is the object of our test, i.e., the stray power when 
as nearly as may be under actual running conditions. 

Calculation of Efficiencies. 

As run. 

Output of dynamo = 220.3 X 45.80 = 10090 Watts output 

554 I^Rad 

10090 428 Field 

544 928 Stray power 

428 11990 Watts input to the dynamo. 

U062 == Work done by current- 



392 



TESTS OF DYNAMOS AND MOTORS. 



Efficiency of Conversion: 

11062 x 100 



11990 



= 92.2 per cent. 



Commercial efficiency: 



10090 X 100 
119.90 

Power required to run dynamo: 

11990 



= 84.1 per cent. 



746 



= 16.1 H.P. 



In this test, carbon brushes were used, and the lead adjusted as carefully 
as possible. If the exact rating of this dynamo had been 45 amperes and 220 
volts at a speed of 1600, and we wished to find the efficiencies corresponding, 
we should proceed in this way. 

The test was made under conditions as nearly as possible to the rating, 
and the stray power as found will not be perceptibly different from what it 
would be under the exact conditions. 

When the load has been as carefully adjusted as in this test, it is seldom 
worth while to make these corrections, as they are smaller than changes pro- 
duced by accidental changes of oiling, temperature, brush pressure, etc., 
of two separate tests. 

Advantages of the Method. 

Small amount of energy used in making the test, namely, only the losses. 
No wire or water rheostat required. Test made under full load, and yet 
the losses are directly measured. All quantities are expressed in terms de- 
pending on the same standards, and therefore the efficiency will be but little 
affected by any error in the standards. No mechanical power measure- 
ments are made, and all measurements are electrical. 

Disadvantages. 

Requires two similar machines. Armature reactions are not alike in both 
machines. Leads are not alike. The iron losses are not the same. No belt 
pull on bearings. Must line up machines and use a good form of mechanical 
coupling. Sometimes difficult to set the brushes on the motor. The motor 
armature is much overloaded. 




u&$&m 



FOR FIELDS 
OF MOTORS 



Fig. 9. Diagram of Connections for Test of Street 
Motors, Prof. Puffer. 



Car 



ELECTRICAL METHOD OF SUPPLYING LOSSES. 393 




Fig. 10. 



Diagram of Connections of Modification of the 
Previous Diagram, by Prof. Puffer. 



This method is of advantage in the test of railway series motors, if slightly 
modified by the separate excitation of the motor fields. If the series field 
windings be not separately excited there will be a great deal of unneces- 
sary difficulty from great changes of speed as the load is varied. However, 
one field may be kept in circuit on the machine used as a motor, as the test 
can then be made with the motor under its exact conditions. There will be 
a very great change of speed during adjustment of load, but there will be no 
danger of injuring anything, as the separate excitation of the dynamo field 
is an aid to steadiness. Railway motors, as generally made, will not stand 
their full rated load continuously, and the motor is likely to get too hot if 
not watched ; the machine used as a dynamo will run cold, as it will not 
have a large current in it. The friction of brushes is very large in these 
motors, and in general there is a want of accuracy in the division of the 
total stray power between the two armatures. It can only be very approxi- 
mately done by the aid of curves showing the relation between speed and 
stray power, and armature voltage and stray power, 

Hopkiaioni Vest of two Similar Direct-Current Dynamos. 

In the original Hopkinson method, the two dynamos to be tested were 
placed on a common foundation with their shafts in line, and coupled to- 
gether. The combination was then driven by a belt from an engine, or other 
source of power, to a pulley on the dynamo shafts. The leads of both ma- 
chines were then joined in series, and the fields adjusted so that one acted 
as a motor driven by current from the other. The outside power in that 
case supplied, and was a measure of the total losses in the combination, the 
efficiency of either machine being taken as the square root of the efficiency 
of the combination. 

Many modifications of this test have been used, especially in the substitu- 
tion of some method of electrically driving the combination, as the driving- 
power is so much easier measured if electrical. 

This test is somewhat like that last given, but the two machines are con- 
nected in series through the source of supply for the difference in power, 
such as a storage battery or generator. The following diagram shows the 
connections for the Hopkinson test, with a generator for supplying the dif- 
ference in power. 

In this test the output of G plus energy taken by M x (motor driving the 
system), gives losses of motor and dynamo (the losses of Mj being taken 
out). These losses being known, the efficiency can be calculated. 

If the two machines D and M are alike, G supplies the I 2 It losses of arma- 
tures, and M the friction, core losses, and I 2 R of fields. 

Another method useful where load and current are both available, is to 
drive one of two similar dynamos as a motor, and belt the second dynamo 
to it. Put the proper load on the dynamo, and the efficiency of the com- 
bination is the ratio of the watts taken out of the dynamo to the watts 
supplied to the motor. The efficiency of either machine, neglecting smalJ 
differences, is then the square root of the efficiency of both. 



394 



TESTS OF DYNAMOS AND MOTORS. 




Fig. 11. Diagram of connections for Hopkinson's test of 
two similar dynamos. 

If P = watts put into the motor, 

P x z=. watts taken from the dynamo, 
x = per cent efficiency of the combination, 
y =z efficiency of either machine, 

A x loo 

*- P ' 

The above test is especially applicable to rotary converters, the belt being 
discarded, and the a c sides being connected by wires ; thus the first ma- 
chine supplies alternating current to the second, which acts as a motor 
generator with an output of direct current. The only error (usually small) 
is due to the fact that both machines are not running same load, since that 
one supplies the losses of both. 

Fleming*'* Modification ofHopkimon Test. — In this case the 
two dynamos under test are connected together by belt or shafts,- and are 




Fig. 12. 

driven electrically by an external source of current, say a storage battery or 
another dynamo, which is connected in series with the circuit of the two 
machines. Figure 12 shows the connections for this test, which will be found 
carried out in full in Fleming's " Electrical Laboratory Notes and Forms." 



Motor Tests. 

Probably the most common method of testing the efficiency and capa- 
city of motors is with the prony brake, although in factories where spare 
dynamos are to be had, with load available for them 5 there can be no 




MOTOR TESTS. 395 

question that belting the motor to the dynamo with an electrical load is 

by far the most accurate, and 

_i * the easiest to carry out. 

Piony brake test. — In 

this test a pulley of suitable 
dimensions is applied to the 
motor-shaft, and some form of 
friction brake is applied to the 
pulley to absorb the power. 
prony brakeT 55 ^^ ^ ^ The following diagram shows 

■p IG 13 one of the simplest forms of 

prony brake ; but ropes, straps, 
and other appliances are also often used in place of the wooden brake shoes 
as shown. 
Note. — See Flather, " Dynamometers and the Measurement of power." 
As the friction of the brake creates a great amount of heat, some method 
of keeping the pulley cool is necessary if the test is to continue any length 
of time. A pulley with deep inside flanges is often used ; water is poured 
into the pulley after it has reached its full speed, and will stay there by 
reason of the centrifugal force until it is evaporated by the heat, or the 
speed is lowered enough to let it drop out. Rope brakes with spring bal- 
ances are quite handy forms. 
The work done on the brake per m inute is the product of the following items : 
I = the distance from the centre of the brake pulley to the point 

of bearing on the scales, in feet, 
n = number of revolutions of the pulley per second, 
w •=. weight in lbs. of brake bearing on scales. 
Power = 2 it I n w = foot-pounds per second, and 

H.P. =?^?= 0.011424 In w. 

The input to the motor is measured in watts, and can be reduced to horse- 
power by dividing the watts by 746; or the power absorbed by the brake can 
be reduced to watts as follows: Brake watts = 8.52 I n w = P. 

If the length, I, be given in centimeters, and the weight, iv, be taken in 
kilograms, the horsepower absorbed by the brake is given by the formula 
H.P. = S26lnwl0~\ 

Again taking the length in centimeters and the weight in kilograms, the 
watts absorbed by the brake are 

Brake watts = 0.616 In w. 

p 
The watts input = Pi and efficiency in percentage = pT X 100. 

Using feet and pounds in the measurements, the efficiency in percentage 
will be 

_ 852 I n w 
Eff * = Pi ' 
Using centimeters and kilograms the efficiency will be 

61.6 In w 



Eff. = ■ 



Pi 



If it is desired to know the friction and other losses in the motor, after the 
brake test has been made, the brake can be removed, and the watts neces- 
sary to drive the motor at the same speed as when loaded, can be ascertained. 

Electrical load test (including loss in belting, and extra loss in bear- 
ings due to pull of belt). — This test consists in belting a generator to the 
motor and measuring the electrical output of the generator, which added to 
the friction and other losses in the generator, makes up the load on the 
motor. The efficiency is then measured as before, by the ratio of output to 
input. The great advantage of this form of test is, that it can be carried on 
for any length of time without trouble from heat, and the extra loss in 
bearings due to pull of belt is included, which is therefore an actual com- 
mercial condition. 



396 TESTS OF DYNAMOS AND MOTORS. 

In this form of test the losses in the generator are termed counter torque, 
and the method of determining them is given following this. 

Counter torque. — In tests of some motors, especially induction mo- 
tors, the load is supplied by belting the motor under test to a direct current 
generator having a capacity of output sufficient to supply all load, including 
overload. 

In determining the load applied to the motor and the counter torque, it is 
necessary to know, besides the /. E. or watts output of the generator, the 
following : — 

1*11 of generator armature, 

Core loss of generator armature, 

Bearing and brush friction and windage of generator, 

Extra bearing friction due to belt tension. 

It is necessary to know the above items for all speeds at which the com- 
bination may have been run during the testing. This is especially useful 
in determining the breakdown point on induction and synchronous motors, 
both of which can be loaded to such a point that they " fall out of step." 

While the motor is under test especial note should be made of the speeds 
at which the motor armature and generator armature rotate, and of the 
watts necessary to drive the motor at the various speeds without load. 

The counter torque will then be the sum of the following three items : — 

P =r PR of generator armature, 
Pe = core loss of generator armature, 
F = bearing and brush friction and windage of the generator armature. 

The field of the dynamo must be separately excited and kept at the same 
value during the load tests and the tests for " stray power " and does not 
enter into any of these calculations. 

Belt-on test. — After disconnecting current from the motor under 
test, and with the belt or other connection still in place, supply sufficient 
voltage to the dynamo armature to drive it as a motor at the speeds 
run during the motor test, holding the field excitation to the same value as 
before, but adjusting the voltage supplied to the armature for changing the 
speed. 

Take readings of 

Speed, i.e., number of revolutions of dynamo armature. 
Volts at dynamo armature. 
Amperes at dynamo armature. 

Construct a curve of the power required to drive the combination at the 
various speeds shown during the motor test. 

Belt-off test. — Throw the belt or other connection off, and take read- 
ings similar to those mentioned above, which will show the power necessary 
to drive the dynamo without belt. 

Then for any speed of the combination the " stray power" will be found 
as follows : — 

P, = watts from belt-off curve, required to drive the dynamo as a motor. 
p n ■=. watts from belt-on curve, required to drive the combination. 
Pc ■=. core loss in dynamo armature. 
F = friction of dynamo belt-off. 
F, •=. friction of motor under test, running light and without belt. 

f— increase in bearing friction of dynamo, due to belt tension. 
/,= increase in bearing friction of motor, due to belt tension. 

From the belt-off curve, 

P, = Pc + F (1) 

From the belt-on curve, 

P„ = Pe + F+F s +f+f 4 (2) 



INDUCTION MOTORS. 



397 



Subtract (1) from (2) 



■ />, = *■,+/+/, 



(3) 



The values of /and f, cannot be determined accurately ; but if the ma- 
chines are of about the same size as to bearings and weights of moving 
parts, it is very close to call them of equal value, when, 



/or/, 



_ (P„ - P, - F t ) 



(4) 



The friction F t of the motor under test has been previously found by 
noting the watts necessary to drive it at the various speeds. If it is an in- 
duction motor, the impressed voltage is reduced very low in determining 
the friction in order that the core loss may be approximately zero. 

As all the values of the quantities on the right-hand side of the equation 
(4) are now known,/ is determined, and may be added to P, to give the total 
11 strew power." A curve is then plotted from the values of " stray power' 
at different speeds. 

Counter torque = (P, -f- f). 

Total load z=IE + PR + (P, +/), 
where IE = watts load on the D. C. machine when it is being driven by 
the motor. 

If S = Pi +/ = " stray power" then 

Total load = IE + l*R + 8. 

The value of/ is so small when compared with the total load, that any 
ordinary error in its determination will be unimportant. 




BOOSTER SUPPLYING IP. 



Test of Street-Railway Motors. 

The " pumping-back " test, as described before, with some little modifica- 
tion serves for testing street-railway motors. The following diagram shows 
the arrangement and electrical connections. 

The motors are driven mechanically by another motor, the input to which 
is a measure of the 

losses, frictional, core Eg g shaft 

losses, gears, bearings, t^^TfT^wT H H supplying core 

etc., in the two motors; VMr -§f D l_l &_J M ^g 5 losses and friction 
the two motors are 
connected in series, 
through a booster, B, 
care being taken to 
make the connections 
in such a manner as to 
have the direction of 
rotation the same ; 
and their voltages op- 
posing. 

Readings are taken and the efficiencies are calculated as in the u pumping- 
back " test. 

In eliminating the friction of bearings, etc., and of the driving-motor, it is 
run first without belts, the input being recorded as taken, at the speed 
necessary. The belt is then put on and a reading taken at proper speed, 
with both the motors under load. 

The load being adjusted by varying the field of booster B, the total losses 
of the system are then IE from booster plus the difference between belt-on 
reading with full load through the motors, and belt-off reading as noted 
(allowance being made for change of I 2 R of driving-motor). If the two 
motors are similar, half this value is the loss in one motor, from which the 
efficiency can be calculated as previously shown. 

Induction motors. — In addition to the tests to which the D. C. motor 



Fig. 14. Diagram of connections and arrange- 
ment of street-railway motors. 



398 TESTS OF DYNAMOS AND MOTORS. 

is ordinarily submitted, there are several others usually applied to the in- 
duction motor, as follows : — 

Excitation ; Stationary impedance ; Maximum output ; and some variations 
on the usual heat and efficiency tests. 

Excitation: This is also the test for core loss-f friction, allowance being 
made for I 2 E of field ; with no belt on the pulley the motor is run at full 
impressed voltage. Read the amperes of current in each leg, and total 
watts input. The amperes give the excitation or " running-light" current, 
and the watts give core loss -}- friction + I 2 R of excitation current. 

Stationary impedance : Block the rotor so it cannot move, and read volts 
and amperes in each leg, and total watts input. This is usually done at 
half voltage or less, and the current at full voltage is then computed by 
proportion. This then gives the current at instant of starting, and a meas- 
ure of impedance from which, knowing the resistance and core loss, other 
data can be calculated, such as maximum output, efficiency, etc. 

Maximum output : This might be called & break-down test; as it merely 
consists in loading the motor to a point where the maximum torque point is 
passed and thus the motor comes to rest. 

Keep the impressed voltage constant and apply load, reading volts, am- 
peres in each leg, the total watts input, and revolutions ; also record the 
load applied at the time of taking the input. Then take counter torque as 
explained before, from which the efficiency, the apparent efficiency, the 
power factor, and maximum output are immediately calculated. 

Heat test. — Run motor at full load for a sufficient length of time to 
develop full temperature, then take temperatures by thermometer at the 
following points : — 

1. Room, not nearer to the motor than three feet and on each side of motor. 

2. Surface of field laminations. 

3. Ducts (field). 

4. Field or stator conductors, through hole in shield. 

5. Surface of rotor. 

6. Rotor spider and laminations. 

7. Bearings, in oil. 

During heat run, read amperes and volts in each line. 

Efficiency test. — Apply load to the motor, starting with nothing but 
friction ; make readings at twelve or more intervals, from no load to break- 
down point. Keep the speed of A. C. generator constant, also the impressed 
voltage at the motor. 

Read, Speed of motor. 

Speed of A. C. dynamo. 

Amperes input to motor, in each leg. 

Volts impressed at motor terminals. 

Watts input to motor, by wattmeter. 

Current and volts output from D. C. machine belted to motor, 

Counter torque as explained above, and excitation reading watts. 

From the above the efficiency, apparent efficiency, power factor 

-^- — ^ — 7s— ; ) » & n <i maximum output can be calculated. 

real efficiency / 

In reading watts in three-phase motors, it is best to use two wattmeters, 
connected as shown in following sketch : — 

1, 2, 3, are the three-phase lines leading to the 
motor. 

A and B are two wattmeters. 

b is the current coil of A, and b 1 of B. 

a is voltage coil of A, and a 1 of B. 

The sum of the deflections of A and B give total 
watts input. At light loads one wattmeter usually 
reads negative, and the difference is the total watts. 

Results. — At the end of the preceding tests the 
following results should be computed, and curves 
plotted from them. 

~ , . Speed of motor x 100. 

% synchronism = -^ r -r- 

Synchronous speed. 



(= 




SYNCHRONOUS MOTOR. 



399 



i real efficiency = 



i apparent efficiency : 



Power factor = — 



Output of motor x 100 
Input by wattmeter 

Output of motor X 100 
volt X amperes 
Watts _ a pparent efficiency 

real efficiency 



Volt x amperes " 

5 250 H. P. 

Torque-pounds pull at 1 ft. radius =: , ... ' * *•»,„+ • 

H * * revolutions per minute 

The above results should be plotted on a sheet in curves similar to Fig. 16, 
taken from Steinmetzs article on " Induction Motors." 




00 




500 


90 




450 


80 




400 


70 




350 


60 




300 


50 




250 


40 


400 


200 


30 


300 


150 


20 


200 


100 


10 


100 


50 



Fig. 16. Curves of results of tests of induction motor. 



Synchronous motor. —Synchronous motors are separately excited, 
and the D. C. exciter should have its qualities tested as a dynamo. Syn- 
chronous motors are tested for Break-down point ; Starting current at differ- 
ent points of location of the rotor ; Least exciting current for various loads. 
All these in addition to the regular efficiency and other tests. Core losses, 
friction, 1 2 R losses, etc., can be found by any of the usual methods pre- 
viously described. 

Break-down point. Synchronous motors have but little starting-torque ; 
and it is necessary to start them without load, throwing it on gradually 
after the motor has settled steadily and without " hunting" on its synchro- 
nous speed. The break-down point is found by applying load to the point 
where the motor falls out of step, which will be indicated by a violent rush 
of current in the ammeter simultaneous with the slowing down. 

This test is usually carried out at about half voltage, the ratio of the load 
on the motor at the moment of dropping out of step will be to the full load 
of break-down as the square of the voltages, the load being adjusted at 
minimum input in each case. For example, say a certain motor, built tc 
run at 2,000 volts, breaks down at 150 K.W., with an impressed voltage of 
1,000. Then the true full break-down load will be 



2,000 2 
1,0002 



X 150 = 600 K.W. 



400 TESTS ; ETC. 

Starting current. Owing to consequent disturbance to the line, it is desi- 
rable that the starting current of a synchronous motor be cut down to the 
lowest point; but it is difficult to reduce this starting current lower than 
200% of full-load current. A synchronous motor also starts easier at certain 
positions of its rotor as related to poles. With the rotor at rest, and the 
location of the centre of its pole-pieces chalked on the opposite member, 
the circuit is closed, the impressed voltage is kept constant, and the current 
flowing in each leg of the circuit is read, and the time to reach synchro- 
nism. Care should be taken to note the amount of the first rush of current, 
and then the settling current at speed. 

Least exciting current. The power factor of a synchronous motor will be 
100 only when, with a given load on the motor, the exciting current is ad- 
justed so that there is neither a leading nor lagging current in the armature. 
Sometimes it is desirable to produce a leading current in order to balance 
the effect of induction motors on the line, or inductance of the line itself. 
This is done by over-exciting the fields. 

With a given load on the motor, the 100 power-factor is found by com- 
paring the amperes in the motor armature with the exciting current in the 
field. Starting with the excitation rather low, the armature current will be 
high and lagging ; as the excitation is increased, the armature current will 
drop, until it reaches a point where, as the excitation is still increased, the 
armature current begins to rise, and keeps on rising as the exciting current 
is increased, and on this side of the low point the armature current is 
leading. 

With no reason for making a leading current, the best point to run the 
motor at is, of course, that at which the armature current is" the lowest ; and 
at that point the power-factor is 100. 

Synchronous Impedance.- The E.M.F. of an alternating dynamo 
is the resultant of two factors, i.e., the energy E.M.F. and inductive E.M.F. 

The energy E.M.F. may be determined from the saturation curve by run- 
ning the machine without load, and learning the field strength necessary to 
produce full voltage. 

The inductive E.M.F. is at right angles to the energy E.M.F., and is de- 
termined by driving the machine at speed, short-circuiting the armature 
through an ammeter, and exciting the field just enough to produce full-load 
current in the armature. The amount of field current necessary to produce 
full load is a measure of the inductive E.M.F., which can be determined from 
the saturation curve as before, and the resultant E.M.F. will be 

Resultant E.M.F. = Venergy E.M.F. 2 + inductive E.M.F. 2 . 

Saturation test. — This test shows the quality of the magnetic cir- 
cuit of a dynamo, and especially the amount of current necessary to saturate 
the field cores and yokes to a proper intensity. In this test it is important 
that the brushes and commutator be in good condition, and that all contacts 
and joints be mechanically and electrically tight. 

The dynamo armature must be driven at a constant speed, and the leads 
from the voltmeter placed to get readings from the brushes of the dynamo 
must have the best of contacts. 

The fields of the dynamo must be separately excited, and must have in 
the circuit with them an ammeter and rheostat capable of adjusting the 
field current for rather small changes of charge. 

The armature must be without load, and a voltmeter must be connected 
across its terminals. 

Should there be residual magnetism enough in the iron to produce any 
pressure without supplying any exciting current, such pressure should be 
recorded ; or perhaps a better way is to start at zero voltage by entirely 
demagnetizing the fields by momentary reversal of the exciting current. 

To start the test, read the pressure, due to residual magnetism if not de- 
magnetized, or if demagnetized, start at zero. Give the fields a small ex- 
citing current, and read the voltage at the armature terminals ; at the same 
time read the current in the fields, and the revolutions of the armature. 
Increase the excitation in small steps until the figures show that the knee of 
the iron curve has been passed by several points ; then reverse the operation, 
decreasing the excitation by like amounts of current, until zero potential is 
reached. 

This is usually as far as it is necessary to go in practice ; but occasionally 



RESISTANCE OF ARMATURE. 401 

it is well to complete the entire magnetic cycle by reversing the exciting cur- 
rent, and repeating the steps and readings as above described. 

The readings should be plotted in a curve with the amperes of exciting 
current as abscissae, and volts pressure as ordinates. 

The E.M.F. will be found to increase rapidly at first ; and this increase 
will be nearly proportional to the exciting current until the " knee " in the 
curve is reached, when the E.M.F. increase will not be proportional to the 
excitation until after the "knee" is passed, when the increase in E.M.F. 
will again become nearly proportional to the excitation, but the increase 
will be at such a low rate as to show that the magnetic circuit is practically 
saturated ; and it is not economical to work the iron of a magnetic circuit too 
far above the knee, nor is it expedient to work it at a point much below the 
" knee" except for boosters. 

The exciting current must not be broken during this test, except possibly 
at zero ; nor must its value be reduced or receded from in case a step should 
be made longer than intended. Inequalities of interval in steps of excit- 
ing current will make little difference when all are plotted on a curve. For 
the same value of exciting current the down readings of E.M.F. will always 
be higher than those on the up curve. 

Resistance of field coils. — The resistance of the shunt fields of a 
dynamo or motor can be taken in any of the usual ways : by Wheatstone 
bridge ; by the current flowing and drop of potential across the field termi- 
nals ; and it is usual, in addition, to take the drop across the rheostat at the 
same time. The resistance of each field coil should be taken to insure that 
all are alike. 

Resistance of series fields, and shunts to the same, must be taken by a dif- 
ferent method, as the resistance is so low that the condition of contacts may 
vary the results more than the entire resistance required. The test for re- 
sistance of armatures following this is quite applicable. Of course any test 
for low resistances is applicable ; but the one described is as simple as any, 
and quite accurate enough for the purpose. 

Resistance of armature. — In order to determine the 7 2 i? loss in a 
generator or motor armature, its resistance must be measured with consider- 
able care ; and the ordinary Wheatstone bridge method is of no use, for the 
reason that the variable resistance of the contacts is often more than that 
of the armature itself. The drop 
method, so useful with higher re- 
sistance devices, is not accurate 
enough for the work ; and the storage .___ 
most accurate method is probably battery, :=: 
the direct comparison Avith a stan- \~ AM# 

dard resistance by means of a adjustable! 
good galvanometer and a storage resistance ^ 
battery. f 

Clean the brushes, commutator 
surface, or surface of the col- 
lector-rings, and in the case of a 

D. C. machine, see that opposite Fig. 17. Diagram of arrangement for 
brushes bear on opposite seg- measuring resistance of armatures, 
ments. 

Connect the galvanometer and its leads, the storage battery and resis- 
tances, as in the following diagram. The standard resistance, R, will ordina- 
rily be about .01 ohm, but may be made of any size to suit the circumstances. 
The storage battery must be large enough to furnish practically constant 
current during the time of testing. The galvanometer must be able to 
stand the potentials from the battery ; and it is usually better to connect in 
series with it a high resistance, so that its deflections may not be too high. 
The deflection of the galvanometer should be as large as possible, and pro- 
portional to the current flowing. The leads a, a t , and b and 6 lt are so ar- 
ranged with the transfer switch that one pair after the other can be thrown 
in circuit with the galvanometer ; and it is always well to take a deflection 
first with R, then again after taking a deflection from the armature. 

The leads a and a t must be pressed on the commutator directly at the 
brush contacts, and may often be kept in place by one of a set of brushes 
at either side. 

Test. — Close the switch, k, and adjust the resistance, r, until the am- 
meter shows the amount of current desired, and watch it long enough to bo 




402 



TESTS, ETC. 



sure it is constant. Close the transfer switch on b and b lt and read the gal- 
vanometer deflection, calling it d. Throw the transfer switch to the con- 
tacts a, and a,, read the galvanometer deflection, and call it d % . Transfer 
the contacts back to 6, and b x and take another reading; and if it differs 
from d 1% take the mean of the two. 

Let x = resistance of the armature, then 



R 



d ' 



Note. — See Fleming's " Electrical Laboratory Notes and Forms." 




AM. nlk^ 

STORAGE .BATTERY 

Fig. 18. Test for break in ar- 
mature lead. 



Tests for Faults in Armatures. 

The arrangement of galvanometer for testing the resistance of an arma- 
ture is the very best for searching for faults in the same, although it is not 
often necessary to measure resistance. 

Test for open circuit. — Clean the brushes and commutator, then 
apply current from some outside source, say a few cells of storage battery 
or low pressure dynamo, through an am- 
meter as in the following diagrams. Note 
the current indicated in the ammeter ; ro- 
tate the armature slowly by hand, and if the 
break is in a lead, the flow of current will 
stop when one brush bears on the segment 
in fault. Note that the brushes must not 
cover more than a single segment. 

If on rotating the armature completely 
around the deflection of the ammeter does 
not indicate a broken lead, then touch the ter- 
minals of the galvanometer to two adjacent 
" bars, working from bar to bar. The deflec- 
tion between any two commutator bars 
should be substantially the same in a perfect armature ; if the deflection 
suddenly rises between two bars it is indicative of a high resistance in the 
coil or a break (open circuit). 

The following diagram shows the connec- 
tions. 

A telephone receiver may be used in place 
of the galvanometer, and the presence of 
current will be indicated by a " tick " in the 
instrument as circuit is made or broken. 

Test for snort circuit. — Where two 
adjacent commutator bars are in contact, or 
a coil between two segments becomes short- 
circuited, the bar to bar test with galvanom- 
eter will detect the fault by showing no 
deflection. If a telephone is used, it will be 
silent when its terminal leads are connected 
with the two segments in contact. See dia- 
gram below for connections. If there be a short circuit between two coils 

the galvanometer terminals 
should include or straddle three 
commutator bars. The normal 
deflection will then be twice that 
indicated between two segments 
until the coils in fault are 
reached, when the deflection will 
drop. When this happens, test 
each coil for trouble ; and if indi- 
vidually they are all right, the 
trouble is between the two. The 
following diagram shows the con- 
nections. 

Test for grounded arma- 
ture. — Place one terminal of the 
galvanometer on the shaft or 
and the other terminal on the commutator. (The 




Fig. 19. Bar to bar test for 
open circuit in coil. 




short ciRcvrr 

BETWEEN SEGMENTS 
OR IN COIL 



HihW 

' STORAGE 
BATTERY 



SHUNT 



Fig. 20. Bar to bar test for short cir- 
cuit in one coil or between commuta- 
tator segments. 

frame of the machine, 



ARMATUKE FAULTS. 



403 



storage battery, ammeter, and leads must be thoroughly insulated from 
ground.) If, under these circumstances, there is any deflection of the gal- 
vanometer, it indicates the presence 
of a ground, or contact between the 
armature conductors and the frame 
of the machine. Move the terminal 
about the commutator until the least 
deflection is shown, and at or near 
that point will be found the contact 
in the particular coil connected be- 
tween two segments showing equal 
deflection, unless the contact happens 
to be close to one segment, in which <e&ixERY 




'SHORT CIRCUIT 
BETWEEN SECTKMB 



Fig. 21 . Alternate bar test for short 
circuit between sections. 



case there will be zero deflection. 

Contacts in field coils can be located 

by the same method. The following 

diagram shows the connections. 
To determine if armature of multipolar dynamo is electrically centred, put 

down brushes 1 and 2, and take volt- 
age of machine ; put down brush 3, 
and lift 1, take voltage again ; put 
down brush 4 and lift 2, again tak- 
ing voltage ; repeat the operation 
with all the brushes, and the volt- 
age with any pair should be the 
same as that of any other pair if the 
armature is electrically central. 

The same thing can also be deter- 
mined by taking the pressure curves 
all around the commutator as shown 
in the notes on characteristics on 
dynamos. 



GROUNDED TO GORE 
AT THIS POINO? 




Fig. 22. 



Test for ground in armature 
coils. 



In the above the brushes should be exactly at the neutral point, 



ALTERNATING-CURRENT MACHINES. 

Revised by E. B. Raymond and Cecil P. Poole. 

For alternating or periodically varying currents there are three values of 
the E.M.F. used, or of which the value is required : 

a. The maximum value, or the top of the wave. 

b. The instantaneous value of a point in the wave. 

c. The effective E.M.F. , or VEean 2 value of the full wave. 

Since the maximum value of a sine curve = - x its average value, the 

maximum value of the E.M.F. of a single-phase bi-polar alternator pro- 
ducing an alternating sine wave of E.M.F. is 

_ 7r * 2v*e 2 r.p.s. __„ 7T * JVc r.p.s. 10 -8 

iLmax — 7, • 10 8 = • 

2 q q 

In an alternator having^ poles and m phases, 

n k <& N c p r.p.s. 10~ 8 

Jimax — - • * 

2 mq 

where k is a number ranging from 1 to 2.5, depending upon the shape of the 
coil of the armature and also upon the shape of the pole-piece. Nc r= num- 
ber of conductors ; q = number of parallel paths in each winding or phase. 
The instantaneous E.M.F. in one winding at any moment 

_ 7T Nc X r.p.s. X $ XP X k 10~ 8 

— — x X sin t7, 

2 mq 

where = the angle through which the armature has turned from the posi- 
tion where the coil embraces the maximum flux. The most important value 
of all is the square root of the mean square value of the sine wave of E.M.F., 
since this value is the effective or working value. It is equal to the maxi- 
mum value of a sine E.M.F. wave -f- ^2, 
Hence 

_ it k<t>N c p r.p.s. 10— 8 1.11 k <l> Np r.p.s. 10~ 8 
jjj — _ _ == . 

2 vlrnq mq 

In three-phase alternators the E.M.F. between terminals will depend upon 
the method of connecting the armature conductors. The two most common 
methods are called the delta connection and the Y or star connection, both 
shown in the following diagrams. 





DELTA CONNECTION Y OR STAR CONNECTION 

Figs. 1 and 2. Values of E.M.F. in three-phase connections when x = y=zz. 

In the delta- connected armature the E.M.F.'s between terminals are those 
generated in each coil, as shown in the diagram. 

In the Y-connected armature the E.M.F. between any two terminals is 
the E.M.F. generated by one of the coils in that phase multiplied by the V3 
or 1.732. 

Two-phase circuits are sometimes connected as a three-phase circuit ; that 
is, both phases have a common return wire. In this case the pressure be- 
tween the two outgoing wires is ^2 x E, and the current in the common 
return will be / V2, both conditions are on the assumption that E and / in 
each phase is the same. 

404 



ENERGY IN THREE-PHASE CIRCUITS. 405 

The current from an alternator depends upon inductance and resistance. 
The coefficient of inductance is represented by the letter L. The E.M.F. 
of an alternator follows approximately a sine curve, and the current from 
it is represented by the same kind of curve. Since in a circuit, lines of 
force exist in proportion to the current flowing, at each of its different cur- 
rent values there is a new value of lines in force. Thus, in a circuit of 
varying current there is a continuously varying flux, and hence there is in- 
duced a back E.M.F. This back E.M.F. is called the back E.M.F. of self- 
induction, and it retards the current flow just as does resistance. 

This back E.M.F. of self-induction combines with the resistance, but at 
right angles thereto, the result being called impedance. 

The coefficient of self-induction = 

max. flux x turns 

L = w .,_. — = henrys. 

amperes X 10 8 J 

Henrys multiplied by 2 *■/ =. reactance ohms (/ = cycles per second). 

In a circuit where R = resistance ohms, and 2 tt fL = reactance ohms, 
these combine at right angles to produce impedance ohms, or the total 
opposing force of the current, thus: 

Impedance = V R* -f (2 n fL)*. 

Hence in an alternator circuit if the coefficient of self-induction of the 
alternator be L, and that of the external circuit be L x \ and if the resistance 
of the alternator armature be R, and that of the external circuit be i? t , 
and the effective E.M.F. generated in the alternator armature =: E f then 
the current flowing will be 

E 

V ( 22 + R % + ( 2 nfL + 2 nfLJ* 

Energy in an Entirely Non-Inductive and Balanced 
Three-Phase Circuit. 

In the following diagram of a Y-connected multiphase generator and cir- 
cuits, let 

e ± = E.M.F. of any phase in the armature, 
i x = current of any phase in the armature, 
E = E.M.F. between mains, 
/ = current in any main, 







1 




Fig. 3. 




P t = power of one phase of the armature, 
P =. total power, 
P 1 = e 1 i l ; 


but 




hence 


P = 3 w x = 5-5f= 1.732 EI, 
V3 


and 


/- I. _ 





' 1.732 E 



406 



ALTERNATING- CURRENT MACHINES. 



In the following diagram of a delta-connected polyphase generator and 
circuits, let 

€ 2 =zE f 
I=i 2 V3, 

P 2 — e 3 i 21 

P=z3P 2 = ^= = 1.732 EI, 
V3 
P 



I — 



1.732 E 




Fig. 4. 



Where the circuit is inductive, in order to determine the real power tin 
above result must be multiplied by the " power factor," or the cosine of the 
" angle " bv which the current lags behind or leads the E.M.F. Thus the 
power in a circuit in which the current lags 9 degrees behind the E.M.F. = 
IE cos 9. If the current lags 90° behind the E.M.F. there will be no energy 
developed as cos 90° = 0. 

The cosine of the angle of lag 0, or the power factor, is equal to the ratio 
of the true watts to the apparent watts. In ordinary lighting distribution, 
the power factor is high so that rough calculations are made without ita 
value being exactly known. 

Angle of Las': To determine with a watt meter in three* 
phase circuit* (Fig. 5) : Connect the current coil in one lead ; connec* 



Wm 




Fig. 5. 

one end of the potential coil to x on the same lead ; now connect the re 
maining end first to one of the remaining leads y, then to z, calling the firs'* 
reading P t and the second, P n ; then if 9 = angle of lag, 

When 9 is greater than 60 degrees, one reading will be negative, so tha> 
the difference of readings will be greater than their sum. 

If i? = resistance per leg of Y-connected armature, 

r= resistance per phase of A-connected armature, 
then, 

PR loss in Y-connected armature = 3 PR 



PR loss in A-connected armature 



=»©; = 



Pr. 



Energy in UTon-Inductive Three-Phase Circuits. 

/ — current in any one of the three wires of external circuit, 
i = current in one phase of the armature for delta connection, 
p- watts output of a balanced three-phase generator, 
1.732 = V3, 
.577 = 1 — V3, 
E = volts between terminals (or lines) on either delta or Y system, 
v — volts of one phase of the armature it connected in " Y," 
R= resistance per leg, of Y-connected armature, 
r = resistance per phase of A-connected armature, 

P=3 I,v = 3 ' —F E 1.732 (either with Y or A armature). 
V3 



COPPER LOSS IN ARMATURES. 



407 



For A 



P = 3r y i = 3v, 



V3 



v.— E 
v p — r , 7 = 1.732 i£ /, which shows statement in brackets to be true. 



V 3 



w 



'— E X 1.732 
/, = 1.732 i in delta system. 



I 2 R loss in Y connected armature = 3 7/72. 
7 2 i? loss in A connected armature = 3 ( -~ \ r =. Ifr. 



— x y 

\*\ E 

%*& 1" E 

E 

!i L. 



fC< r E 

E 



Fig. 6. Fig. 7. 

E=^E,z= 1.1Z2E,. 



E=E, 




/ AMPERES = 1 .732 X 2 OT X 



I AMPERES ~Z 



\ I AMPERES = 1.732X Z or y 



AMPERES ■ 1.782.X V or X 



\Z AMP8. 
)J£™£: I AMPERES =y 




3CAMP8. / AMPERES =0J 



Delta Connection. Star or Y Connection. 

ftGS. 8 and 9. Values of current in three-phase connections, where x=zy=zz. 



Copper LoMi in the Armatures of Alternators. 

A. Ruckgaber. 

In the armature of any alternating-current dynamo or motor of either 

single or polyphase the copper loss is always equivalent to -~— , in which 

/= total amperes and R = the measure of resistance between leads of a 
phase, usually taken as an average of the measurements of the armature 
resistance of each phase. 

Let R = Resistance as measured (average). 
r — Resistance per phase. 
/ z= Total amperes = watts -J- volts. 
I x — Amperes per lead. 
i — Amperes per phase, in winding. 



Single-Phase. 



- Here /= I x = i ; and R : 
l^R loss = I*R. 



408 



ALTERNATING-CURRENT MACHINES. 



Two-Phase Independent Wind- 
ing* (Fig. 10). 

R is measured from 1 to 3 and 2 to 4. 



'=S 


_ watts 
volts 




'1=4 


Then I*R loss = 2 X PB 






_JLI 2 B 

4 


r-R 

2 



Fig. 10. 
Two-Phase Winding-* Connected in Series (Fig. 11). 

E X 2 

The I X 2 R loss = A i*r = 

R is measured from 1 to 3 and 2 to 4, 
the average of these two being taken 
for the value of R. 

B= (r + r)(r + r) _ r 



h _ 

V2~ 


I 
: 2V2 




4 l^r __ 

8 ~~ 


/2 r 
2 



Then 



4 r 



/2/2 

: 2 



The IJR loss 
Three-Phase Star Connection (Fig. 12). 





E V 3 



Then the /^ loss = 3 i*r = 3 T^r = i 2 r. 

J? is measured from 1 to 2, 2 to 3, and 3 to 
1, the average of the three being the value 
used for R. 



Then R as measured — 2r. 
PR 



.-. The IJR loss = ■ 



Fig. 12. 



Three-Phase Delta Connection (Fig. 13) 

E l V3 *V3 3* 



Then Vi? loss = 3 iV = 



I*r 

3 * 




-ft is measured from 1 to 2, 2 to 3, 
and 3 to 1, the average of these being ^ 3 
taken as the value of R. 

r ( r _L r ) 9 T2J? 

Then R as measured = ^ ; = - r and the IJR loss = ^. 

r -+• r -\- r 6 * 2 



-AA/WV\\WvWWWV-- 

r 
Fig. 13. 



2\ 



REGULATORS LOR GENEKATORS. 409 



Compensated Revolving* field Alternators. 

The General Electric Company in October, 1899, placed on the market a 
new type of polyphase alternator, which is claimed to overcome many of 
the faults common to the old style of machine, especially when used on 
combined lighting and motor loads. While it has been found a compara- 
tively easy matter to compound and over-compound for non-inductive loads, 
it has been heretofore quite difficult to add excitation enough to compound 
for inductive loads which require considerably more held current than do 
loads of a non-inductive nature. 

The following description is taken from the bulletin issued by the makers 
describing the machine, which is of the revolving field type : — 

" The means by which this result is accomplished are as follows : The 
shaft of the alternator which carries the revolving field carries also the 
armature of the exciter, which has the same number of poles as the alter- 
nator, so that the two operate in synchronous relation. In addition to the 
commutator, which delivers current to the fields of both the exciter and the 
alternator, the exciter has three collector rings through which it receives 
current from one or several series transformers inserted in the lines leading 
from the alternator. This alternating current, passing through the exciter 
armature, reacts magnetically upon the exciter field in proportion to the 
strength and phase relation of the alternating current. Consequently the 
magnetic field and hence the voltage of the exciter, are due to the combined 
effect of the shunt field current and the magnetic reaction of the alternating 
current. This alternating current passes through the exciter armature in 
such a manner as to give the necessary rise of exciter voltage as the non- 
inductive load increases, and without other adjustment, to give a greater 
rise of exciter voltage with additions of inductive load." 

REGULATORS FOR ilTERXATOG C1IBREWT 
GENERATORS. 

General Electric Company. 

This regulator automatically maintains the voltage of the generator at 
the desired value by varying the exciter voltage. This is done by rapidly 
opening and closing a shunt circuit across the exciter field rheostat. Fig. 14 
shows the elementary connections of the regulator. The rheostat shunt 
circuit is opened and closed by a deferentially wound relay. The current 
for operating this relay is taken from the exciter bus bars and is controlled by 
the floating main contacts. The current for operating the direct-current con- 
trol magnet is also taken from the exciter bus bars. The relay and the direct- 
current control magnet constitute the direct-current portion of the regulator, 
and maintain not a constant but a steady exciter voltage. The alternating- 
current portion of the regulator consists of a magnet having a potential 
winding connected, by means of a potential transformer, to the bus bars or 
the circuit to be regulated. This magnet also has an adjustable compen- 
sating winding which is connected in series with the secondary of a current 
transformer usually inserted in the principal lighting circuit. The core of 
this magnet is attached to a pivoted lever carrying a counterweight which is 
balanced by the attraction of the magnet. If a load is thrown on the genera- 
tor the voltage will tend to drop, the alternating-current magnet will weaken 
and destroy the balance of the core and lever and cause the main contacts to 
close ; this in turn will close the relay contacts and entirely short-circuit 
the exciter field rheostat, thus increasing the exciter voltage until the origi- 
nal balance of the alternating-current magnet core and lever is restored 
and the alternating-current voltage maintained at the required value. 

In some cases the exciter voltage will vary from 70 to 125 volts from no 
load to full load. This is especially true if the load is partly inductive 
and the regulator is adjusted to compensate for the line loss. In order to 
get the full range of regulation within the scope of the regulator in such 
cases, the alternating field rheostat should be turned entirely out and the 
exciter field rheostat adjusted to lower the alternating-current voltage 
about 65 per cent below normal. When the regulator is switched in, it will 
close the rheostat shunt circuit and instantly build the voltage up to nor- 
mal, and maintain normal voltage by rapidly opening and closing the 
rheostat shunt circuit. 



410 



ALTERNATING-CURRENT MACHINES. 



MAIN CONTACTS 






POTENTIAL 
INDING 




POTENTIAL 
GENERATOR TRANSFORMER ^^ 
RHEOSTAT 



PCT 5 



CURRENT TRANSFORMER 



A.C. GENERATOR 




Fig. 14. Diagram of Tirrell regulator and connections for a single genera- 
tor and exciter. 

Alternating-Current Armatures. 

Almost any continuous current armature winding may in a general way 
be used for alternating currents, but they are not well suited for such work, 
and special windings better adapted for the purpose are designed. 

Alternating current armature windings are open-circuit windings, except- 
ing in the rotary converter, where the rings are tapped directly on to the 
direct current armature windings. 

Early forms of armature windings of this type, as first used in the United 
States, had pan-cake or flat coils bound on the periphery of the core. In 
the next type the coils were made in a bunched form, and secured in large 
slots across the face of the core. Both these types were used for single- 
phase machines. After the introduction of the multiphase dynamo, arma- 
ture windings began to be distributed in subdivided coils laid in slots of the 
core ; and this is the preferred method of to-day, especially so in the case of 
revolving field machines. 

The single coil per pole type of winding gives the larger E.M.F., as the 
coils are thus best distributed for influence by the magnetic field. This type 
also produces the highest self-induction with its attendant disadvantages. 

The pan-cake and distributed-coil windings are much freer from self-induc- 
tion, but do not generate as high E.M.F. as does the single-coil windings. 

In well-considered multiphase windings the E.M.F. is but little less for 
distributed coils than for single coils, and has other advantages, especially 
where the use of step-up transformers permits the use of low voltages, and 
consequently light insulation for the coils. The distributed-coil winding 
offers better chance for getting rid of heat from the armature core, and the 
conductor can in such case be made of less cross-section than would be 
required for the single-coil windings. 

The greater number of coils into which a winding is divided, the less will 



ARMATURE WINDINGS. 



411 



>e the terminal voltage at no load. Parshall & Hobart give the following 
•atio for terminal voltage under no-load conditions : 
Single-coil winding = 1. for the same total number of conductors, the 
spacing of conductors being uniform over the whole circumference. 
Two-coil winding =: .707. 
Three-coil winding — .667. 
Four-coil winding = .654. 

When the armature is loaded, the current in it reacts to change the termi- 
nal E.M.F., and this may be maintained constant by manipulation of the 
exciting current. With a given number of armature conductors this reac- 
tion is greatest with the single coil per pole winding, and the ratios just 
given are not correct for full-load conditions. 

Single -phase Winding's. — The following diagram shows one of the 
simplest forms of single-phase winding, and is a single coil per pole winding. 




Fig. 15. 

Another similar winding, but with bars in place of coils, is shown in the 
following figure. It can be used for machines of large output. 




Fig. 16. 



412 



ALTERNATING-CURRENT MACHINES. 



The following figure shows a good type of three bars per pole winding, 
which is simple in construction. 




Fig. 17. 



Two-phase Winding's. — The following diagram shows a good type 
of winding for quarter-phase machines. It utilizes the winding space to 
good advantage, and is applicable to any number of coils per pole per phase. 




Fig. 18. 



Fig. 19 is a diagram of a bar winding for a quarter-phase machine, with 
four conductors per pole per phase. 
Tnre«-pliase Winding's. — Fig. 20 is a diagram of a three-phase 



ARMATURE WINDINGS. 



413 



srinding connected in Y, in which one end of each of the three windings 
is connected to a common terminal, the other ends being connected to 
three collector rings. 




Fig. 19. 

Fig. 31 is a sample of a three-phase delta winding, in which all the con- 
ductors on the armature are connected in series, a lead being taken off to a 
collector ring at every third of the total length. 





Fig. 20. 



Fig. 21. 



In the Y windings the proper ends to connect to the common terminal and 
to the rings may be selected as follows : Assume that the conductor in the 
middle of the pole-piece is carrying the maximum current, and mark its direc- 
tion by an arrow ; then the current in the conductors on either side of and ad- 
jacent to it will be in the same direction. As the maximum current must be 
coming from the common terminal, the end toward which the arrow points 
must be connected to one of the rings, while the other end is connected to 
the common terminal. It is quite as evident that the currents in the two 
adjacent conductors must be flowing into the common terminal, and there- 
fore the ends toward which the arrows point must be connected to the com- 
mon terminal, while their other ends are connected to the remaining two 
rings. 

In a delta winding, starting with the conductors of one phase in the mid- 
dle of pole-piece, assume the maximum current to be induced at the 
moment in this conductor ; then but one-half the same value of current 
will be included at the same moment in the other two phases, and its path 



414 



ALTERNATING-CURRENT MACHINES. 



and value will best be shown in the following diagram, in which x may be 

taken as the middle collector-ring, and the maximum current to be flowing 

from x toward z. It will be seen that no current 

is coming in over the line y, but part of the current 

at z will have been induced in branches b and c. 

Most three-phase windings can be connected 
either in Y or delta ; but it must be borne in mind 
that with the same windings the delta-connection 
will stand 1.732 times as much current as the Y- 

connection, but gives only — — as much voltage. 




Fig. 22. Path and Value 
of Current in Delta- 
eonnected Armature. 



Armature Reaction of an Alternator. 



Since the armature core is a part of the magnetic 
circuit, and since the armature winding surrounds 
this core and also carries current, it must be 
expected that this current influences the total magnetism of the machine 
and hence its voltage. This effect, combined with the natural inductance 
of the winding, itself constitutes what is called armature reaction. Fig. 23 









a* 




]a A 










r ,mmmm "" 


l"^' 




A 


it\ V * 




< } 




» / 







N 


b'\ 




^ffj' /b ' 


S ( I 






,,B* 






c 'Xe 


A 








m 


\ 

m 



















Fig. 23. 



■hows an alternator in its elements. The armature winding is tapped in 
two places and connected to the collector rings d and e, from which the 
current flows to the external circuit. This current passing through the 
winding on the armature creates a magneto-motive force, which tends to 
produce the flow of magnetism as shown by the dotted lines a—b—c; 
a' — b' — c', or in a general direction, m — n. 

The field current proper entering at A and coming out at B tends to pro- 
duct magnetism in the direction x — y, at right angles to m — n. Under 
such conditions, therefore, the ampere-turns of the armature are acting at 
right angles to the ampere-turns of the field. This is the condition under 
non-inductive load, the maximum current of the armature occurring in 
time and space simultaneously with the maximum E.M.F. 

If the maximum of the current of the armature occurs later than the 
maximum of the E.M.F. , or in other words, if the current lags behind the 
E.M.F., the ampere-turns of the armature are no longer acting in a direc- 
tion m — n when the current is a maximum, but in a direction m' — n\ 
partially opposing the main flux x — y. If the lag of current becomes 90° 
the armature reaction would turn still more around, becoming, in fact, just 
opposite to x — y. 

Thus, on non-inductive load, the armature ampere-turns combine with the 
field ampere-turns at right angles, and with increasing lag show a higher 
and higher resultant until at 90° lag the two combine by direct addition. 
Just similar to all this is the self-induction component of the armature 
inductance. As has been pointed out, self-induction lags in its opposing 



ARMATURE REACTION. 



415 



effects behind the current, thus on non-inductive load, the opposing effect 
of self-induction is shown by Fig. 24. 




Fig. 24. 

Let a — c =zlz=. the current, 

a — dz= E = the E.M.F. generated by the revolutions of the arma- 
ture, 
a — b-=z the resistance drop r= IR in phase always with the current, 
a—g = IX '= the inductive drop 90° away from the current. 

The resultant of these = a — e = E =: the total E.M.F. necessary to pro- 
duce to give the value E under the conditions. 
If the current lags these values are as shown in Fig. 25, the current lag- 




FlG. 25. 

ging behind and E.M.F. by the angle 0. At 90° lag the E.M.F. of self- 
induction is just in line with E, hence is added directly to give the total 
E.M.F. E necessary to generate to product E. 

Thus a similarity exists between the armature reactive effect shown in 
Fig. 23 and the armature self-inductive effect shown in Figs. 24 and 25. On 
this account it has been suggested by Mr. C. P. Steinmetz that the two 
values be combined into one and the combined value be given the term 
" synchronous impedance." This value is obtained in an actual alternator 
by short-circuiting the armature upon itself and reading the ampere-turns 
in the field coils necessary to give full armature current, which is then 
expressed in terms of ampere-turns. Since on short-circuit the armature 
ampere-turns are exactly opposing the field ampere-turns, this reading 
gives a direct measure of the armature opposing forces, but conveniently 
converted into ampere-turns. To calculate from this value the amount of 
ampere-turns necessary in a given alternator to give a certain voltage, pro- 
ceed as follows : 

Let A equal the ampere-turns necessary to produce the terminal voltage 
E of the alternator when running on open circuit : let B equal the syn- 
chronous impedance ampere-turns obtained as above. Then the total 
ampere-turns required to produce the voltage E on non-inductive load 
= V J2 -|_ B 2 If the current is not non-inductive the two values must be 
combined with proper phase relation, as shown in Figs. 24 and 25. The 



416 



ALTERNATING-CURRENT MACHINES. 



method has been extensively used and for ordinary designs seems a very 
useful one to follow. A designer can calculate this value to a very close 
approximation, thus predetermining the regulation. It can be seen from 
this that a single-phase alternator gives a pulsating armature reaction. A 
polyphase armature gives a constant armature reaction since it can be shown 
that at any instant the magnetic resultant of the current is the same. 

For this reason, among others, a polyphase alternator is more efficient 
than a single-phase machine since the pulsating armature reaction sets up 
eddy currents from its variable nature, which increases the losses. 



§YICHRONIZEH§. 

There are numerous methods of determining when alternators are in step, 
some acoustic, but mostly using incandescent lamps as an indicator. 

In the United States it is most common to so connect up the synchronizer 
that the lamp stays dark at synchronism ; in England it is more usual to 
have the lamp at full brilliancy at synchromism, and on some accounts the 
latter is, in the writer's opinion, the* better of the two, as, if darkness indi- 
cates synchronism, the lamp breaking its filament might cause the machines 
to be thrown together when clear out of step ; on the other hand, it is some- 
times difficult to determine the full brilliancy. 

The two following cuts show theory and practice in connecting synchro- 
nizers. 

IO.TERNA.TOR 
HO. 1 



/& 



/& 



—.moo, 1 |— vQj&fls 






K\ 



^© "^ 



Fig. 26. Synchronizer Connections. 

When connected as shoivn, the lamp 
will show full c.p. at synchronism. 

If a and b are reversed, darkness of 
lamp will show synchronism. 




Fig. 27. Synchronizer Connections. 

Lamp lights to full c.p. when dyna- 
mos are in synchronism. 

Two transformers having their primaries connected, one to the loaded 
and the other to the idle dynamo, have their secondaries connected in series 
through a lamp ; if in straight series the lamp is dark at synchronism ; if 
the secondaries are cross-connected the lamp lights in full brilliance at 
synchronism. 

The Lincoln Synchronizer is so made as to move a hand around a 
dial so that the angle between the hand and the vertical is always the 
phase angle between the two sources of electro-motive force to which the 
synchronizer is connected. If the incoming alternator is running too fast 
the hand deflects in one direction, and if too slow, in the opposite direction. 
Coincidence in phase occurs when the moving hand stands vertically. A 
complete revolution of the hand indicates a gain or loss of one cycle in the 
frequency of the incoming alternator as compared with bus-bars. 



SYNCHRONIZING GENERATORS. 



417 



Suppose a stationary coil F, Fig. 28, has suspended within it a coil A, free 
to move about an axis in the planes of both coils and including a diameter 
of each. If an alternating current be passed through both coils, A will 
take up a position with its plane parallel to F. If now the currents in A 
and F be reversed with respect to each other, coil A will take up a position 
180° from its former position. Reversal of the relative directions of currents 
in A and F is equivalent to changing their phase relations by 180°, and 
therefore this change of 180° in phase relations is followed by a correspond- 
ing change of 180° in their mechanical relations. Suppose now, that instead 
of reversing the relative direction of currents in A and F, the change in 
phase relations between them be made gradually and without disturbing 
the current sjbrength in either coil. It is evident that when the phase 
difference between A and F reaches 90° the force between A and F will 
become reduced to zero, and a movable system, of which A may be made a 
part, is in condition to take up any position demanded by any other force. 
Let a second member of this movable system consist of coil B, which may 
be fastened rigidly to coil A, with its plane 90° from that of coil A, and the 
axis of A passing through a diameter of B. 
Further, suppose a current to circulate 
through B, whose difference in phase rela- 
tive to that in A, is always 90°. It is evident 
under these conditions that when the differ- 
ence in phase between A and F is 90°, the 
movable system will take up a position 
such that B is parallel to F, because the 
force between^ and F is zero, and the force 
between B and F is a maximum ; similarly 
when the difference in phase between B 
and F is 90°, A will be parallel to F. That 
is, beginning with a phase difference be- 
tween A and F of 0, a phase change of 90° 
will be followed by a mechanical change 
on the movable system of 90°, and each suc- 
cessive change of 90° in phase will be 
followed by a corresponding mechanical Fig. 28. Lincoln Synchronizer, 
change of 90°. For intermediate phase 

relations it can be proved that under certain conditions the position of 
equilibrium assumed by the movable element will exactly represent the 
phase relations. That is, with proper design, the mechanical angle between 
the plane of F and that of A and also between the plane of F and that of B 
is always equal to the phase angle between the current flowing in F and 
those in A and B respectively. 

As commercially constructed coil F consists of a small laminated iron 
field-magnet with a winding whose terminals are connected with binding 
posts. The coils A and B are windings practically 90° apart on a laminated 
iron armature pivoted between the poles of the magnet. These two 
windings are joined, and a tap from the junction is brought out through a 
slip-ring to one of two other binding posts. The two remaining ends are 
brought out through two more slip-rings, one of which is connected to the 
remaining binding post, through a non-inductive resistance, and the other 
to the same binding post through an inductive resistance. A light 
aluminum hand attached to the armature shaft marks the position assumed 
by the armature. 




< 



lUTDUCTOIt tym: synchroscope. 

From The Electric Journal. 

This type is especially applicable where voltage transformers are already 
installed for use with other meters. As it requires only about ten apparent 
watts it may be used on the same transformers with other meters. There 
are three stationary coils, A r , M and C, Fig. 29, and a moving system com- 
prising an iron armature, A, rigidly attached to a shaft, S, suitably pivoted 
and mounted in bearings. A pointer, B, is also attached to the shaft S. 
The moving system is balanced and is not subjected to any restraining 



418 



ALTERNATING-CURRENT MACHINES. 



force, such as a spring or gravity control. The axes of the coils N and M 
are in the same vertical plane, but 90 degrees apart, while the axis of C is in 
a horizontal plane. The coils A x and ikf are connected in " split phase " rela- 
tion through an inductive resistance P and non-inductive resistance Q, and 
these two circuits are paralleled across the bus-bar terminals 3 and 4 of the 
synchroscope. Coil C is connected through a non-inductive resistance 
across the upper or machine terminals 1 and 2 of the synchroscope. 

In operation, current in the coil C magnetizes the iron core carried by 
the shaft and the two projections, marked A and " Iron Armature" in Fig. 
29. There is, however, no tendency to rotate the shaft. If current be 
passed through one of the other coils, say M, a magnetic field will be pro- 
duced parallel with its axis. This will act on the projections of the iron 
armature, causing it to turn so that the positive and negative projections 
assume their appropriate position in the field of the coil M. A reversal of 




Pointer -B n 

' ' ' I 




Fig. 29. 



the direction of the current in both coils will obviously not affect the posi- 
tion of the armature ; hence alternating current of the same frequency and 
phase in the coils C and M cause the same directional effect upon the 
armature as if direct current were passed through the coils. If current 
lagging 90 degrees behind that in the coils M and C be passed through the 
coil jV, it will cause no rotative effect upon the armature because the 
maximum value of the field which it produces will occur at the instant 
when the pole strength of the armature is zero. The two currents in the 
coils M and N produce a shifting magnetic field which rotates about the 
shaft as an axis. As all currents are assumed to be of the same frequency, 
the rate of rotation of this field is such that its direction corresponds with 
that of the armature projections at the instants when the poles induced in 
them by the current in the coil C are at maximum value and the field shifts 
through 180 degrees in the same interval as is required for reversal of the 
poles. This is the essential feature of the instrument, namely, that the 
armature projections take a position in the rotating magnetic field which 
corresponds to the direction of the field at the instant when the projections 
are magnetized to their maximum strength by current in the coil C. If 
the frequency of the currents in the coils which produce the shifting field is 
less than that in the coil which magnetizes the armature, then the arma- 
ture must turn in order that it may be parallel with the field when its poles 



PARALLEL OPERATION. 419 

are at maximum strength, consequently rotation of its armature indicates 
a difference in frequency, and the direction and rate of rotation show, 
respectively, which current has the higher frequency and the amount of 
the difference. 

Note on the Parallel Running* of Alternators. — There is 
little if any trouble in running alternators that are driven by water-wheels, 
owing to the uniform motion of rotation. With steam-engine driven ma- 
chines it is somewhat different, owing to more or less pulsation during a 
stroke of the engines, caused by periodic variations in the cut-off, which 
cause oscillations in the relative motion of the two or more machines, 
accompanied by periodic cross currents. Experiments have proved that a 
sluggish governor for engines driving alternators in parallel is more desi- 
rable than one that acts too quickly ; and it is sometimes an advantage to 
apply a dashpot to a quick-acting governor, one that will allow of adjust- 
ment while running. It is quite desirable also that the governors of engines 
designed to drive alternators in parallel shall be so planned as to allow of 
adjustment of speed while the engine is running, so that engines as well as 
dynamos may be synchronized, and load may be transferred from one 
machine to the others in shutting down. Foreign builders apply a bell con- 
tact to the same part of all engines that are to be used in this way, and throw 
machines together when the bells ring at the same time. These bells would 
also serve to determine any variation, if not too small, in the speed of the 
machines, and assist in close adjustment. 

Manufacturers do not entirely agree as to the exact allowance permissible 
for variation in angular speed of engines, some preferring to design their 
dynamos for large synchronizing power, and relatively wide variation in 
angular speed, while others call for very close regulation in angular varia- 
tion of engine speed, and construct their dynamos with relatively little syn- 
chronizing power. 

Dynamos of low armature reaction have large synchronizing power, but if 
accidentally thrown out of step are liable to heavy cross-currents. On the 
contrary, machines with high armature reaction have relatively little syn- 
chronizing power, and are less liable to trouble if accidentally thrown out 
of step. 

The smaller the number of poles the greater may be the angular variation 
between two machines without causing trouble, thus low frequencies are 
more favorable to parallel operation than high ; and this is especially so 
where the dynamos are used to deliver current to synchronous motors or 
rotary converters. 

Specifications for engines should read in such a manner as to require not 
more than a certain stated angular variation of speed during any stroke of 
the machine, and this variation is usually stated in degrees departure from 
a mean speed. 

The General Electric Company states it as follows : — 

"We have . . . fixed upon two and one-half degrees of phase departure 
from a mean as the limit allowable in ordinary cases. It will, in certain 
cases, be possible to operate satisfactorily in parallel, or to run synchronous 
apparatus from machines whose angular variation exceeds this amount, 
and in other cases it will be easy and desirable to obtain a better speed con- 
trol. The two and one-half degree limit is intended to imply that the max- 
imum departure from the mean position during any revolution shall not 

2i 
exceed ^ of an angle corresponding to two poles of a machine. The angle 

ooO 
of circumference which corresponds to the two and one-half degrees of 
phase variation can be ascertained by dividing two and one-half by one-half 
the number of poles ; thus, in a twenty-pole machine, the allowable angular 

2i 
variation from the mean would be -^ = .25 of one degree." 

Some foreign builders of engines state the conditions as follows : Calling N 
the number of revolutions per minute, the weight of all the rotary parts of 
the engine should be such that under normal load the variation in speed dur- 
. ,. Nmax. — Nmin. ... , 1 „ 1 

mg one revolution — will not exceed — - • Some state — - • 

N average 250 200 

Oudin says : " The regulation of an engine can be expressed as a percent- 
age of variation from that of an absolutely uniform rotative speed . A close 
solution of the general problem shows that 1£° of phase displacement cor- 



I 



420 



ALTERNATING-CUKRENT MACHINES. 



responds to a speed variation, or *' pulsation," with an alternator of two n 
poles, as follows : — 

2 75% 
In the case of a single cylinder or tandem compound engine — ■ 



A cross compound . 



5.5% 



A working out of the problem also shows . . . that no better results are 
obtained from a three-crank engine than a two-crank. 

The Westinghouse Company designs its machines with larger synchro- 
nizing effect by special construction between poles, and allows somewhat 
larger angular variation, stating it as follows: The variation of the fly- 
wheel through the revolution at any load not exceeding 25% overload, shall 
not exceed one-sixtieth of the pitch angle between two consecutive poles 
from the position it would have if the motion were absolutely uniform at 
the same mean velocity. The maximum allowable variation, which is the 
amount which the armature forges ahead plus the amount which it lags 
behind the position of absolute uniform motion is therefore one-thirtieth of 
the pitch angle between two poles. 

The number of degrees of the circumference equal to one-thirtieth of the 
pitch angle is the quotient of 12 divided by the number of poles. 

The cross currents of alternators can be shown by reference to Fig. 30, 




Fig. 30. 



which represents the E.M.F. vectors of two alternators which have swung 
apart in phase due to any cause, such as variation in speed of their prime 
movers or fluctuations of speed during a revolu- 
tion. 
Let O—A = E.M.F. vector of alternator A. 
O—B — E.M.F. vector of alternator B. 

As drawn, the vectors are displaced in phase by 
the angle 0. When these alternators are con- 
nected in multiple there will be acting between 
them the E.M.F. A — B, or drawn to the center 
point O, the E.M.F. O — B. This E.M.F. acts 
through the two armatures in series, the circuit 
being a — b — c — d, (Fig. 31); the current result- 
ing is equal to the volts O — D divided by the im- 
pedance of the two armatures in series, which is 
equal to 

V(/? a + J? 6 )2 + (2 7r/Za + 2 nfLb)* 

where Ra and Bb = the resistance of the two al- 
ternator armatures respectively and La and Lb 
their inductances. 

Since in such a circuit the proportion of inductance is greater than tht, 
resistance, the current flowing from the E.M.F. O — D is lagging a large 
amount as shown by the line O — C. Hence the E.M.F. 's O — A and — B 




Fig. 31. Two Alterna- 
tors Connected in 
Multiple. 



ALTERNATING-CURRENT MOTORS. 421 

of the alternators proper are in phase approximately with this cross current 
and hence under such conditions as the figure indicates there will be an ex- 
change of energy (since E.M.F. and current are in phase) which is what 
actually happens, thus tending to bring the two alternators together in 
phase. 
Fig. 32 shows the vectors of two alternators A and B in phase but the 

C 



->A 



Fig. 32. 

E.M.F. O — A smaller than the other, — B, due, for instance, to the field 
of one being weaker than that of the other. In this case there is a difference 
of — D volts to act through the armatures of the two alternators in 
series, as in Fig. 31. As shown in Fig. 32 the current from this E.M.F. 
O — D lags 90° and is indicated by the vector O — C. This current is, how- 
ever, 90° away from the E.M.F.'s O — A and O — B of the machine proper 
and hence does not represent an exchange of energy ; therefore, it has no 
tendency to bring the machines together or increasing the dephasing. 

Synchronizing*. 

It is plain from the foregoing that to connect an idle alternator in 
parallel with one or more already in use : 

Excite the fields of the idle machine until at full speed the indicator 
shows bus-bar pressure, or the pressure that may have been determined 
on as the best for connecting the particular design of alternator in circuit. 

Connect in the synchronizer to show when the machines are in step, at 
which point the idle machine may be connected to the bus bars. The load 
will now be unequally divided, and must be equalized by increasing the driv- 
ing-power of the idle dynamo until it takes on its proper part of the load. 

Very little control over the load can be had from the field rheostats. 

To disconnect an alternator from the bus-bars : Decrease its driving power 
slowly until the other machines have taken all the load from it, when its 
xiain switch may be opened and the dynamo stopped and laid off . 

ALTERWATIMG-C1JRREKT MOTORS. 

The single-phase alternating-current motor has been quite well developed 
luring the last few years, but it has as yet come into rather limited use. 
The polyphase motor has come into very general use, its relative simplicity 
oeing a strong feature. 

Only the most elementary formulas will be given here, and the reader is 
referred to the numerous books treating on the subject ; among others, 
S. P. Thompson, Steinmetz, Jackson, Kapp and Oudin. 

Following is a statement of the theory of the polyphase motor, condensed 
from a pamphlet of the Westinghouse Electric and Manufacturing Com- 
pany. 



i 



422 



ALTERNATING-CURRENT MACHINES. 



Elementary Theory of the Polyphase Induction Motor. 

If a horse-shoe magnet be held over a compass the needle will take a posi- 
tion parallel to the lines of force which flow from one pole to the other. 
It is perfectly obvious that if the magnet be rotated the needle will follow. 

If a four-pole electromagnet be substituted for the horse-shoe, and current 
be made to flow about either one of the sets of poles separately, the needle 
will take its position parallel with the lines of force that may be flowing, as 
will be seen by the following figures. 





Fig. 33. 



Fig. 34 



If the two sets of poles are excited at the same time by currents of equal 
strength, then the needle will take its position diagonally, half way be- 
tween the two sets of poles, as will be seen by the following diagram. 

It is now easily conceivable that if one of these currents is growing 
stronger while the other is at the same time 
becoming weaker, the needle will be at- 
tracted toward the former until it reaches 
its maximum value, when if the currents 
are alternating, the strong current having 
reached its maximum begins to weaken, 
and the other current having not only re- 
versed its direction but begun to grow 
strong, attracts the needle aAvay from the 
first current and in the same direction of 
rotation. If this process be continually 
repeated, the needle will continue to re- 
volve, and its direction of rotation will be 
determined by the phase relation of the 
two currents, and the direction of rotation 
can be reversed by reversing the leads of 
one phase. 

If the compass needle be replaced by an 
iron core wound with copper conductors, 
secondary currents will be induced in 
these windings, which will react on the field windings, and rotation will 
be produced in the core just as it was in the compass needle. Two cranks 
at right angles on an engine shaft are analogous with the quarter-phase 
motor, and three to the three-phase motor, which depends on the same 
principle for its working. 




Fig. 35. 



Theory of the Polyphase Induction motor. 
Condensed from C. P. Steinmetz. 

The following names and symbols are used for designating the parts and 
properties of the induction motor : — 



THE INDUCTION MOTOR. 423 

Statorzz stationary part, nearly always corresponding to the field. 
Rotor = rotating part, corresponding to the armature of the direct-current 
motor. 

Analytical Theory of Polyphase Induction Motor. 

Let r = resistance per circuit of primary, 

r t = resistance per circuit of secondary , 

being reduced to primary system by square of the ratio of turns. 

Let p = number of poles, 

x = reactance of primary, per circuit, 
x x z=z reactance of secondary, per circuit, 

reduced to primary system by square of the ratio of turns. 

Let s = per cent of slip, 

/ = current per circuit of primary, 
E z= applied E.M.F. per circuit, 
Z=. impedance of whole motor per circuit, 
T=z torque between the stator and rotor, 
f = frequency of applied E.M.F. 

Let the primary and secondary consist of m circuits on an m phase system. 

n = primary turns per circuit, 
*&i= secondary turns per circuit. 

Let a = — ratio of transformation. 

«i 

Then 

sE 
/(neglecting ex. current) =• V / , Na , 9/ , — r, » 
B v (r t -f s r) 2 + s 2 (x -f- x t )* 

Toraue T- mpr^s 

^ ""4 7r/[(r 1 + sr)2 + s 2 (^i+^) 2 ] 

n mr x E 2 s (1 — s) 

Power = ■ — 



" (r x -\- s r)2 + s 2 (x x + x)* 



mpE 2 

Max. torque = g -^^=== , 



Max. power = 2[r " r f +Jg] at the slip . = v ^< 

E 

Starting current = i =2 — » 

JO 

, ,. mpE 2 n 

Starting torque = ~^y X ~ 

Note that the maximum torque is independent of secondary resistance r t . 
and thus the speed at maximum torque depends on the secondary resistance 
Current at maximum torque is also independent of secondary resistance. 

The maximum torque occurs at a lower speed than the maximum output. 
A resistance can be chosen that when inserted in the secondary, the maximum 



424 



ALTERNATING-CURRENT MACHINES. 



torque will be obtained at starting ; that is, the speed at which maximum 
torque occurs can be regulated by the resistance in the rotor. 




Ro. 36. Torque curves for Polyphase Induction Motor. 

Curves 1, 2, and 3 show the effect of successive increases of rotor resist- 
ance, rotor run on part of curve a—b ; for here a decrease of speed due to 
load increases the torque. 

Speed of Induction Motor. — The speed or rotating velocity of 
the magnetic field of an induction motor depends upon the frequency 
(cycles per second) of the alternating current in the field, and the number 
of poles in the field frame, and may be expressed as follows : — 

r.p.m. = revolutions per minute of the magnetic field, 
p = number of poles, 
/= frequency ; then 

r.p.m. ~ 120 - 
P 

The actual revolutions of the rotor will be less than shown by the formula, 
owing to the slip which is expressed in a percentage of the actual revolu- 
tions ; therefore the actual revolutions at any portion of the load on a 
motor will be 

r.p.m. x slip due to the part of the load actually in use. 
actual speed = r.p.m. (1 — % of slip.) 

The following table by Wiener, in the American Electrician^ shows the 
speeds due to different numbers of poles at various frequencies. 



Speed of Rotary field for Different Number* of Poles 
and for Various frequencies. 



O 


Speed of Revolving Magnetism, in Revolutions per Minute, when 






Frequency is : 




a ° 


25 


30 


33£ 


40 


50 


60 


66§ 


80 


100 


120 


125 


133$ 


2 


1500 


1870 


2000 


2400 


3000 


3600 


4000 


4800 


6000 


7200 


7500 


8000 


4 


750 


900 


1000 


1200 


1500 


1800 


2000 


2400 


3000 


3600 


3750 


4000 


6 


500 


600 


667 


800 


1000 


1200 


1333 


1600 


2000 


2400 


2500 


2667 


8 


375 


450 


500 


600 


750 


900 


1000 


1200 


1500 


1800 


1875 


2000 


10 


300 


360 


400 


480 


600 


720 


800 


960 


1200 


1440 


1500 


1600 


12 


250 


300 


333 


400 


500 


600 


667 


800 


1000 


1200 


1250 


1333 


14 


214 


257 


286 


343 


428 


514 


571 


686 


857 


1029 


1071 


1143 


16 


188 


225 


250 


300 


375 


450 


500 


600 


750 


900 


938 


1000 


18 


167 


200 


222 


267 


333 


400 


444 


533 


667 


800 


833 


889 


20 


150 


180 


200 


240 


300 


360 


400 


480 


600 


720 


750 


800 


22 


136 


164 


182 


217 


273 


327 


364 


436 


545 


655 


682 


720 


24 


125 


150 


167 


200 


250 


300 


333 


400 


500 


600 


625 


667 



THE INDUCTION MOTOR. 



425 



Slip. —The slip, or difference in rate of rotation between rotating field 
and rotor, is due to the resistance opposed to rotor current. 

Slip varies from 1 per cent in a motor designed for very close regulation 
to 40 per cent in one badly designed, or designed for some special purpose. 

Weiner gives the following table as embodying the usual variations : 



Slip of Induction Motors. 



Capacity of Motor, H.P. 


Slip, at full load, per cent. 










Usual limits. 


Average. 


, 


20 to 40 


30 


1 


10 ■ 


1 30 


20 


1 


10 ■ 


« 20 


15 


1 


8 ■ 


« 20 


14 


2 


8 « 


* 18 


13 


3 


8 * 


* 16 


12 


6 


7 ■ 


1 15 


11 


n 


6 ■ 


1 14 


10 


10 


6 « 


■ 12 


9 


15 


6 « 


♦ 11 


8 


20 


4 ■ 


« 10 


7 


30 


3 ■ 


* 9 


6 


50 


2 « 


" 8 


5 


75 




1 7 


4 


100 




« 6 


3.5 


150 




• 5 


3 


200 




♦ 4 


2.5 


300 




• 3 


2 



Core of Stator and Rotor. — Both the field-frame core, or Stator > 
and the armature core, or Itotor, are built up of laminated iron punchings in 
much the same manner as are the armature cores of ordinary dynamos. 

The windings in both cases are laid in slots across the face of either part, 
and for this reason both parts are punched in a series of slots or holes for 
the reception of the windings. The following cuts, taken from the " Ameri- 
can Electrician," show the usual form of slots used. 





Figs. 37 and 38. Forms of Punchings of Induction Motors. 



The number of slots in the stator must be a multiple of the number of poles 
and number of phases, and Weiner gives the following table, in the " Ameri- 
can Electrician," as showing the proper number to be used in various cases, 
both for two- and three-phase machines. In practice the number of poles 
is determined by the speed required and the available frequency ; then the 
number of slots is so designed as to be equally spaced about the whole innei 
periphery of the stator. 



426 ALTERNATING-CURRENT MACHINES. 

Somber of Slots in Field-Frame of Induction Motors. 



Capacity of Motor. 


Number of 
Poles. 


Slots per 
Pole. 


Slots per Pole per Phase. 


Two-Phase. 


Three-Phase. 


£ H.P. to 1 H.P. 


4 to 8 


3 

4 


? 


1 


1 H.P. to 1 H.P. 


4 to 6 


5 
6 


? 


2 




4 to 10 


5 
6 


9 


2 


2 HJP. to 5 H.P. 


4 to 6 


7 
8 
9 


? 


3 


6 H .P. to 50 H.P. 


6 to 12 


7 
8 
9 


4J 


3 


4 to 8 


10 
11 

12 


5 


4 




10 to 20 


7 
8 
9 




3 


50H.P.to200H.P. 


8 to 12 


10 
11 
12 
13 


5 


4 




6 to 10 


14 
15 
16 


7 

? 


5 



The number of slots per pole per phase in the rotor must be prime to that 
of the stator in order to avoid dead points in starting, and to insure smooth 
running, and commonly range from 7 to 9 times the number of poles, or 
any integer not divisible by the number of poles, in the squirrel cage or 
single conductor per slot windings. The proper number of slots may be 
taken from the following table by Wiener ; 



THE INDUCTION MOTOR 



427 



Number of Rotor Slots for Squirrel-Cagre Induction Motors 
up to 5 H.I*. Capacity. 



Number 

of 
Poles, p. 


Limits of Slots, 
Number 
7 p. to 9 p. 


Number of Rotor Slots. 


4 
6 
8 


28 to 36 
42 " 54 
56 " 72 


29, 30, 31, 33, 34, 35, 37. 

43, 44, 45, 46, 47, 49, 50, 51, 52, 53. 

57,58,59,60,61,62,63,65,66,67, 68, 69,70,71. 



In large machines, where there is more than one conductor in each slot 
and in which the winding is connected in parallel, the number of slots in 
the rotor must be a multiple of both the number of phases and the number 
of pairs of poles. 

The following table gives numbers of slots for various field-slots : 

Number of Rotor-Slots for Induction Motors of Capacities 
over 5 H.P. 



Number of 

Field-Slots per 

Pole. 


Number of Rotor-Slots. (n« = 
Field-Slots.) 


= number of 


8 


fn,. 


or § n*. 




9 


§ n 8 . 






10 


fn«. 


» fn*. 




12 


|iu. 


" fn«. 




14 


fn«. 


" §n«. 




15 


f n«. 


" fn 8 . 




16 


|n 8 . 


" |n«. 





Flux Density. — This must be settled for each particular case, as it 
will be governed much by the quality of iron and the particular design of 
the motor. 

Hysteresis loss increases as the 1.6 power of the flux density ; and eddy 
current losses are proportional to the square of the density and also to the 
square of the frequency. 

The following table shows practical values : 

flux-Densities for Induction Motors. 

(Wiener.) 





Flux-Density, in Lines of Force per Square Inch. 


Capacity 

of 

Motor, 

H.P. 


For Frequencies 
from 25 to 40. 


For Frequencies 
from 60 to 100. 


For Frequencies 
from 120 to 180. 




Practical 
Values. 


Aver- 
age. 


Practical 
Values. 


Aver- 
age. 


Practical 
Values. 


Aver- 
Age. 


i 


12000 to 18000 
15000 " 25000 
18000 " 32000 


15000 
20000 
25000 


10000 to 15000 
12000 " 18000 
15000 " 25000 


12500 
15000 
20000 


7000 to 11000 
7500 " 12500 
8000 " 17000 


9000 
10000 
12500 



428 ALTERNATING-CURRENT MACHINES 

Flux-Densities for Induction Motors —(Continued). 





Flux-Density 


in Lines of i 


orce per 


Square Inch. 




Capacity 
of 


For Frequencies 


For Frequencies 


For Frequencies 


Motor, 


from 25 to 40. 


from 60 to 100. 


from 120 to 180. 


H.P. 
















Practical 


Aver- 


Practical 


Aver- 


Practical 


Aver- 




Values. 


age. 


Values. 


age. 


Values. 


age. 


1 


20000 to 40000 


30000 


18000 to 32000 


25000 


9000 to 21000 


15000 


2 


25000 " 45000 


35000 


20000 " 40000 


30000 


10000 " 25000 


17500 


5 


30000 " 50000 


40000 


25000 " 45000 


35000 


11000 " 29000 


20000 


10 


40000 " 60000 


50000 


30000 " 50000 


40000 


12500 " 32500 


22500 


20 


50000 " 70000 


60000 


35000 " 55000 


45000 


15000 " 35000 


25000 


50 


60000 " 80000 


70000 


40000 " 60000 


50000 


17500 " 37500 


27500 


100 


70000 " 90000 


80000 


45000 " 65000 


55000 


20000 " 40000 


30000 


150 


80000 " 100000 


90000 


50000 " 70000 


60000 


25000 " 45000 


35000 


200t 


90000 " 110000 


100000 


60000 " 80000 


70000 


30000 " 50000 


40000 



t And over. 

In the earlier induction motors it was considered the most efficient method 
to connect the driving current to the revolving part or rotor ; and as it is 
highly important that 
the number of windings 
on the rotor be prime to 
that of the stator, Fig. 39 
shows a winding with an 
odd combination of con- 
ductors, being 51, or three 
times 17. 

The stator windings 
would then be bars, con- 
nected at either end to a 
heavy copper ring, this 
forming a sort of " squir- 
rel-cage." 

In the modern ma- 
chines the winding 
shown would be in coils 
on the stator, the three 
ends being carried to 
terminal blocks on the 
outside of the machine 
instead of to rings as 
shown, and the " squirrel- 
cage " would then be 
placed on the rotor and 
be made of bars as men- 
tioned. 

Starting* and It em- 
ulating- Devices. — Small induction motors, up to about 5 h. p. capa- 
city, are started by closing the circuit directly to the motor. In large ma- 
chines this would not be safe, as the rotor is standing, and would act in a 
lesser degree as the short-circuited secondary of a static transformer, and 
cause a heavy rush of current. 

Resistance in Rotor. —This is a favorite method with the General 
Electric Company. A set of strongly constructed resistances is secured 
inside the rotor ring, and so arranged with a lever that they may be closed 
orshoU-circuited after the motor has reached its full speed. These resist- 




Fig. 39. 



THE INDUCTION MOTOR. 429 

ances are in the armature circuits. In order to give maximum starting torque 
total armature resistance should be 

r, = V r2 + (a?/ + y)l 
Where r x — rotor resistance per circuit reduced to field system, 
x x := rotor reactance per circuit reduced to field system. 
r = resistance per field circuit. 
y =z reactance per field circuit. 

This method serves the double purpose of keeping down the starting cur- 
rent and increasing the starting torque. 

Resistances in Stator. — Resistance boxes may be connected in the 
circuits supplying induction motors ; three separate resistances in three- 
phase circuits, and two separate resistances in two-phase circuits. They 
must be all connected in such a manner as to be operated in unison. Under 
these conditions the pressure at the field terminals is reduced, as is of course 
the starting current and the starting torque. In order to start a heavy load, 
under this arrangement, a heavy starting-current is necessary. 

Compensators or Auto-Transformers. —This method is greatly 
favored by the Westinghouse Electric Manufacturing Company, and is used 
extensively by the General Electric Company. It consists of connecting an 
impedance coil across the line terminals, the motor being fed, in starting, 
from some point on the winding where the pressure is considerably less 
than line pressure. This avoids heavy drafts of current from the line, thus 
not disturbing other appliances attached thereto, but as regards starting 
current and torque has the same effect as resistances directly in the line ; 
that is, greatly reduces both. 

Rotor Winding's Commutated.— In this arrangement all or a 
part of the rotor windings are designed to be connected in series when 
starting, and are thrown in parallel after standard speed is attained. 
Another design has part of the conductors arranged in opposition to the 
remainder in starting, but all are thrown in parallel in regular order when 
running at standard speed. These commutated arrangements have not 
been much used in the United States. 

The single-phase alternating-current motor brought out by the Wagner 
Electric Manufacturing Company of St. Louis, is, in mechanical construc- 
tion, similar in many respects to the two and 
z three-phase motors on the market. A field is 

built up of iron plates very much like A of Fig. 
40, and an armature core is also built up from 
iron plates very much like B. 

The field is wound with so-called pan-cake coils 
threading through the slots of the punchings, as 
shown at C, thus producing a magnetic pole of 
intensity, varying from a maximum along the 
radius x — y to zero along the radius x — z. The 
armature core is wound with an ordinary direct- 
current progressive winding, connected up to a 
commutator in exactly the same fashion as is the 
direct-current motor winding. 
Fig. 40. -^ ne commutator of this armature is so designed 

that it may be completely short-circuited by intro- 
ducing into it a short-circuiting circle of copper 
segments. When so short-circuited, the winding affords a substitute for the 
squirrel-cage form of winding, above described, differing from the squirrel 
cage, in that instead of currents being able to select paths for themselves, 
they are restricted to flowing in paths afforded by the individual coils. The 
operation of this motor, as stated, is based wholly upon the principle that 
an induction motor with a completely short-circuited armature will, when 
up to the running speed, operate on single-phase current supply in exactly 
the same manner as does a two or three-phase motor with two or three- 
phase current supply. 

The armature winding is short-circuited through carbon brushes bearing 
upon the commutator surface, and the currents flowing in it are generated 
by induction from the field. These currents flow out through the carbon 
rushes either into an outside resistance box, or where a direct short cir- 




430 



ALTERNATING-CURRENT MACHINES. 



cuit of the brushes is provided, out through one brush and back into the 
armature through the other. By the shifting of the brushes on the com- 
mutator surface, they are forced to take such position relative to the mag- 
netic poles of the field, that repellant action between them and the poles 
of the fields is eifected, and rotation results. When running speed is 
attained, the brushes are no longer required and the armature winding is 
completely short-circuited, as stated. The short-circuiting ring is made 
up of small copper links, which links, being in turn mounted upon a short- 
circuiting band, are thrown into the annular opening in the commutator and 
by making close contact with the individual segments, produce a very effec- 
tive short-circuiting of the entire armature winding. In the operation of 
the motor, it is very advantageous to have this short-circuiting operation 
performed either at or slightly below the running speed, so these motors are 
built with an automatic device for performing this operation. This device 
consists of a set of governor weights acting against a spiral spring. The 
centrifugal action of the weight will, at the proper speed, force the short- 




Fig. 41. Cross Section of Wagner Motor. 



circuiting links into the commutator, against the action of the spring. At 
the same instant and by the same means, the brushes bearing upon the 
commutator are thrown off. 

Fig. 41 shows a view in cross-section of the Wagner motor, and the dia- 
gram, Fig. 42, shows the elementary connections of the same ; the first 
diagrammatic motor being shown as in the starting condition, and the 
diagram at the right showing the condition of the armature after it has 
attained full running speed and the commutator is short-circuited. 



S¥ICHR0^01J§ MOTORS. 



Alternators are convertible into motors ; and one alternator will run in 
synchronism with another similar machine after it is brought to the same 
speed, or, if of unlike number of poles, to some multiple of the speed of the 
driven dynamo, provided the number of pairs of poles on the motor is 



SYNCHRONOUS MOTORS. 



431 



ORDIN*<V 

LIGHTmG 
TRANSF. 



STARTING 
SWITCH 



r<*»<>*a»J Rheostat 

.'/Sometimes i 
I // :<iMied with 
L. A. J»rg« Moion 



1 FUSE CUT OUT 



LIGHTING CIRCUIT 

OPERATING FROM 

SAME TRANSFORMER 



<!><!> pop 




STARTING 

COMMUTATOR CONNECTIONS 

•REPULSION MOTOR 



Rotot Winding 
Stator Winding 
Commutator. 
>rt Circuiting Links and 
ng automatically introduced 
mo Cjra mutator: Carbou SruthM 
mu!uneou»_'y removed from. 
iCommuutpr.. 
RUNNING 
COMMUTATOR CONNECTIONS 
•INDUCTION MOTOR 



Fig. 42. Connections of Wagner Single-Phase Motor. 



divisible into the multiple. Such motors will run as if geared to the driven 
dynamo even up to two or three times its normal full torque or capacity. 
Single-phase synchronous motors have no starting-torque, hut synchronous 
motors for multiphase circuits will come up to synchronism without much 
load, giving about 25 % starting-torque, starting as induction motors, with 
the d. c. field open. 

When connected to lines on which are connected induction motors that 
tend to cause lagging currents and low-power factor of the line, over excita- 
tion of the synchronous motor fields acts in the same manner as a condenser 
introduced in the line, and tends to restore the current to phase with the 
impressed E.M.F., and therefore to do away with inductive disturbances. 

It is necessary to provide some source from which may be obtained con- 
tinuous current for exciting the fields of the synchronous motor ; and this is 
oftenest done by the use of a small d. c. dynamo belted from the motor- 
shaft, the exciting current not being put into use until the motor armature 
reaches synchronism. 

In starting a synchronous motor the field is open-circuited, and current is 
turned on the armature. In practice, field coils are connected in various ways 
to obviate the dangers of induced voltage, and a low resistance coil similar 
to the series winding of the d. c. machine is sometimes so arranged on the field 
poles as to give the necessary reaction for starting. Another way is to use 
a low-pressure excitation, and therefore few turns on the field coils ; also 
the field coils are " split up " by a switch at starting. The field excitation is 
thrown on after the rotating part approaches synchronism, which may be 
indicated by a lamp or other suitable device at the operating switchboard. 

Considerable care must be exercised in the use of synchronous motors, and 
their best condition is where the load is quite steady, otherwise they intro- 
duce inductive effects on the line that are quite troublesome. The field of 
such a motor can be adjusted for a particular load, so there will be neither 
leading nor lagging current, but unity power factor. If the load changes, 
then the power factor also changes, until the field is readjusted ; if the load 



ALTERNATING-CURRENT MACHINES. 



has been lessened the current will lead, and if it increases the current will 
lag. If induction motors are connected to the same line, with a synchro- 
nous motor that has a steady load, then the field of the synchronous motor 
can he over-excited to produce a leading current, which will conteract the 
effect of the lagging currents induced by the induction motors. If two or more 
synchronous motors are connected to the same circuit, and the load on one 
of them is quite variable, and its field is not changed to meet such changing 
conditions, a pumping effect is liable to take place in the other motors, unless 
especial provision has been made in the design of the motors to prevent it. It 
is only necessary to arrange one of the motors of the number for preventing 
this trouble, but better to make all alike. A copper shield between pole- 
pieces, and covering a portion of the pole-tip, will prevent the trouble ; and 
the Westinghouse Electric and Manufacturing Company use a heavy copper 
strap around each pole-piece, with a shoe covering part of the pole-tip in 
the air-gap. 

Theory of the Synchronous motor. 

Let R = resistance of whole circuit, 
L = inductance of whole circuit, 
E x = generator E.M.F., 
E 2 = motor E.M.F. 





E<> resultant 



Fig. 43. 
Take the origin at 0. 
Let E represent maximum value, 

e = instantaneous value, 
e x = E x sin (o> t -f- <£), 
e 2 = E 2 sin (<o t — </>), 

where w = 2 tt/, and/ number of complete cycles per second 

e = E sin (w t — \p), 

where i// = angle of lag of E with respect to the origin. 

E Q 2 = EJ + E 2 2 -f- 2 E X E 2 cos 2 <f>, 



For 



Eo > E x , E leads, 
E 2 <E l , E lags, 



cos \f/ = — ~ cos 4>, 

r» j? 

tan rjf = 2 * tan <f>, 

(E. + E 2 ) 
sin »// = V *1, — - cos <f» ; 



E Q and <f> are known, 
Energy shifts the origin by the angle \]/. 

e x = E x sin (a> t + </> -\- \f/), 
e 2 = E 2 sin (ut t — <j> -f" #)• 



Now 



THE SYNCHRONOUS MOTOR. 

E n 



433 



/ = 



" V,R2 + ta ,2£2 

and / lags behind E by the angle 5 where 

LP 

tan 5 z=i — =■ • 
K 

By introducing the angle \f/ we are referring the E.M.F.'s of both machines 
to the zero point of the resultant wave as origin. 
In general 



1 f T > M E1 
= ji f « idt=— cos®, 



P = -7* 



where 

Let 

Then 



P = the power in watts, and 

$ =. lag or lead of / with respect to E, 

E and / are maximum values, 

T= - » or the periodic time. 
n 

P x as power given to the circuit by the generator, 
P 2 =. power absorbed from the circuit by the motor, 



XT 
e, idt— — l , E ° cos (<f> + i/r + 8) [i = /sin (P 1 t — «)], 

2 Vm + i^L* 



* = ^ 



E 



2 Vi22_|_ w 2£2 

sin 6 as - 



[cos (4> + \p) cos 6 — bin ($ + \fj) sin 8], 



cos 5 = - 



" V.R2 _J_ JJl ^2 ^R2 4. 0,2 2,2 

''' Pl = 2(R^+!iL*) {^ co s(<^ + ^)-Z wS in ($ + *)}, 
and substituting — </> for -f- <£ we get 

{ R cos (0 — «J0 + 2/ w sin (<fr — i//) } . 



P* = 



2 (.R2 + w 2 X2) 



Now 



Bin \\i as 
cos»// = 



IT 2/ sin<ft, 

^0 



and cos v// = — ±-= — ^ 

-&0 



cos <£. 



Substituting and reducing 

^ 2+ ^ 2£2 {^i(igco820 + Xu) 8 in2»)^Jg > ig} 



P 2 = 



An angle <£i is introduced such that 
R 



sin 2^ — 



Vi22 _|. w 2 £2 



- » and cos 2 <£i : 



' Vtf2 + w 2 £2 



434 



ALTERNATING-CURRENT MACHINES. 



Substitute in P 2 
1 



P* = 



and 



[e x Vi22 + w 2i2 S in {2<!> + 2<p')-EiR\ • 



P 2 is a maximum when 
or 



2$ + 2<fr' = 90° 



<*> + <*>': 



that is, the 4i sine term " = unity. 



P 2 is positive provided 



E l R 

— > - i 

J£ 2 Vtf2 + W 2£2 




FIELD 

Fig. 44. 



which shows that it is possible to have E 2 greater than E x if there is the 
proper ratio of resistance and reactance in" the circuit. 

Now, if we plot from an actual motor the 
armature current and the field excitation we 
get a curve shown in Fig. 44. 

This shows that the armature current 
varies with the excitation for a given load. 
The flatter curves are for increase of load. 
Point a shows under excitation, 
b shows over excitation, 
c shows the excitation which 
makes the power factor unity ; it is well 
from the point of stability of operation to 
slightly over excite, and this makes E 2 >E, , 
and also counteracts the inductive drop m 
the line, thus showing that the action of an 
over excited synchronous motor is similar to a condenser. 

Graphical treatment. 

Eg = generator E.M.F. 
Em = motor E.M.F. 
Eo — resultant E.M.F. 
Io = resultant current. 
O I g z=z projection of Io on Eg. 
O Im — projection of Io on O Em. 
O Ig . OEg — ug = energy given up by 

the generator. 
O Im . Em = wm = energy absorbed by 
the motor from the cir- 
cuit, 
com is negative, which shows that com is the 
motor, because it is taking energy from 
the circuit ; and similarly <o g is the gener- 
ator, because O Eg . O Ig is positive, and 
gives up energy to the circuit. 

[For further discussion see Jackson's 
Alternating Current and Alternating Car- 
rent Macliines; also Electrical World for 
March 30 and April 6, 1895, by Bedell and 
Ryan. The latter is the classic paper on the subject.] 




ANGLE OF LAG POSITIVE 



Fig. 45. 



DY>4UOTORM. 

These are of two styles, one for changing direct current of one voltage 
into direct current of a different voltage, and usually called in America 
motor-generators; the second class changes alternating current into direct 
current or vice versa, the voltage not being changed excepting from alter- 
nating Vmean 2 values to direct-current values equal to the top of the 
alternating wave ; these latter machines are now called rotary converters, 
and are largely used. 



DIRECT-CURRENT BOOSTERS. 435 

Dynamotors are now largely used in telegraph offices for reducing the 
pressure of the supply current to voltages suitable for use in telegraphy 
and for ringing and charging generators in telephone offices. 

Theory. Let 

E = voltage at motor terminals. 

e = voltage at generator terminals. 

/ zz current in motor armature. 

B zz resistance of motor armature. 

Nc = number of conductors in motor armature. 

L zz current in generator armature part. 

ijL zz resistance of generator armature part. 

iv c ,= number of conductors in generator armature part. 

Nc 

— — zz k =. coefficient of transformation. 

E zz induced E.M.F. in motor part. 

E x zz induced E.M.F. in generator part. 

E = r.p.s. X Nc X </>. 

^i = r.p.s. X Nc Y X <*>. 

E —E — RI. 

E 1 = e-\- EJ V 

ke = E = EI — krJ v 

If it be assumed that losses by hysteresis and eddy currents be negligible, 
or that EI zz E X I Y whence I x zz kl, then 



E 

k ' 



«,+!)/, 



Such machines run without sparking at the commutator, as all armature 
reactions are neutralized. 



!>fi 11 ■;< T-C I ItJREUT IftOOfcTXIlS. 

This is a tvpe of motor generator much in use for raising or lowering the 
pressure on long feeders on the low-pressure system of distribution, and is 
to be found in most of the larger stations of the Edison companies. It is 
also much used in connection with storage-battery systems in charging cells. 

The " booster " consists of a series generator driven by a motor direct con- 
nected to its armature shaft. The terminals of the generator are connected 
in series with one leg of the feeder ; and it is obvious that the current in the 
feeder will excite the series field just in proportion to the current flowing, 
provided the design of the iron magnetic circuit is liberal enough so that 
the field is way below saturation (on the straight part of the iron curve way 
below the knee). As the armature is being independently rotated in this field, 
it will produce an E.M.F. approximately in proportion to such excitation, 
which E.M.F. will be added to that of the feeder or will oppose that E.M.F., ac- 
cording as the terminal connections are made. On three-wire systems two 
generators are direct connected to one motor, and for convenience on one 
bed-plate. . . 

Such a booster can be so adjusted as to make up for line loss as it in- 
creases with the load. 

One danger of a booster that is not always taken into account is. that if 
the shunt of the driving-motor should happen to open, or, in fact, anything 
should happen to the driving-motor that would result in its losing its power, 
the generator would immediately become a series motor, taking current 
from the line to which it is connected, and by its nature would reverse in 
direction of rotation, and increase in speed enormously, and if not discon- 
nected from its circuits in time would result in a complete wreck of the 
machine. It is always safest to have the generator terminals connected to 
their line through some automatic cut-out, so arranged that should 
the shunt break, as suggested, it would actuate the device, and automati- 
cally detach the booster from the circuit before harm could be done, 



436 



THE ROTARY CONVERTER. 



ROTARY CONVERTERS. 



A rotary converter is the name given to a machine designed for changing 
alternating currents into direct currents. If the same machine be used 
inverted, i. e., for changing direct currents into alternating, it is some- 
times known as an inverted converter. Again, if the same machine be 
driven by outside mechanical power, both alternating and direct currents 
may be taken from it, and it then becomes known as a double current 
generator. 

Theoretically the rotary converter is a continuous current dynamo with 
collector rings added, which are connected by leads to certain parts of the 
armature windings, sometimes at the commutator segments. 

In the following figure, which represents in diagram the single-phase 
rotary converter, the collector rings r and r± are connected by leads to dia- 
metrically opposite segments or coils of the armature at c and c v It is 
obvious that as the armature revolves the greatest difference of potential 
between the rings, or maximum E.M.F., will be at the instant the segments 
c and Cj pass under and coincide with the brushes B and B 1 ; and this 
E.M.F. will decrease as the rotation continues, until the lowest E.M.F. 
will occur when the segments c and c 1 are directly opposite the centre of 
the pole-pieces P and P v 




SINGLE PHASE ROTARY CONVERTER 

Fig. 46. 



The maximum alternating E.M.F. will be equal to the direct-current 
voltage at the brushes B and B lt and if the machine be designed to produce 
a sinuso idal curve of E.M.F., then the alternating E.M.F., that is, the 
Vmean 2 or effective E.M.F., will be, 

e = JL=.707 J£, 
V2 



where e = Vmean 2 value of the alternating E.M.F. , 
and E = direct-current voltage between brushes. 



In a bipolar machine the frequency = r.p.s., and in a machine with p 
poles the frequency will be — r.p.s. 



Neglecting losses and phase displacement the supply of alternating cur- 
rent to the rings must be / V2 = 1.414 / where / is the direct-current 
output. 

If, as shown in Fig. 47, another pair of rings be added, and connected to 
points on the winding at right angles to the first, then another and similar 



THE ROTARY CONVERTER. 



43? 



E.M.F. will be produced, but in quadrature to the first. The E.M.F. will be 
the same for each phase as in the single-phase connection previously shown, 
and still neglecting phase displacement and losses the current will be for 
each of the two phases 

-£= = .707 /. 
V 2 




TWO PHA8E, OR QUARTER PHASE 
ROTARY CONVERTER 

Fig. 47. 

If three equidistant points on the armature windings be connected to 
three rings, as shown in the following diagram, a three-phase converter is 
produced. 




THREE PHASE ROTARY CONVERTER 

Fig. 4& 

As the connections of a three-phase rotary are always delta, the E.M.F.'s 
as compared with the continuous current E.M.F. E have the following 
value : 

E 
Voltage between collector ring and neutral point e = — — = .354 E. 

2 V 2 



Voltage between collector rings e 1 = 



E^3 



Alternating current input : 



2V^ 

IE _ 2/V~2 

: 3e" 3 



.612 E. 



: .943 1. 



Steinmetz, in the Electrical World of Dec. 17, 1898, gives the following 
tables of values of the alternating E.M.F. and current in units of direct 
current. 



438 



THE ROTARY CONVERTER. 





© 


fl 






1:1* 




8 




ii 


CO 1 


|CN| 

> « 

CN ! 


d 
*« 

ICN 
> 


g 






s 








6 












> 


cp 

CO 

a 


ii 


1 


CO 

1 


| 


£ 


A 


ilCN 








H 


Pa 


1 CN 










cp 


"* 
8 


S 


CN 


CN 

5 


jjjj 

55 


,d 
Pi 


II 


ii 


ii 

|CN| 


ii 

|CN| 






j 




t- 












o 




6 


(0 

CO 


ii 


to 


t>; 


«3 


Is 

H 


e3 

,d 


ii 

1H ICN 


ii 

-,|i <N 

l> 


11 

r-l ICN 


& 


® 


•«*< 

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CN 
CO 




3 


CP 


CO 

c3 


ii 


ii 


N 


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,d 


ip 


ICO||<N 


|CN| 


|CN||CQ 




h> 


> rfc 


> r 


> > 






1 CN 


1 CN 


CN 1 


CN 1 CO 






S 


5 


"<* 


"*< 


cp 


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t^ 


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rf| 




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- 1 > 

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'bio 
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03 o 

oJ cp 


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d * 
cp CO 

CP^ 






§ bo d 


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St; a 

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CP 


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CP 






OJ2 


co <».S 


CO 
CP 

u 


00 «P 
CP c« 






co *? =3 


CP 


cp'd 






Sgg 


^3 O M 


a 


ftoS 






O-H fl 


O 


8 


a 






k 


|> 


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4 





THE ROTARY CONVERTER. 



439 



The values of E.M.F. and of current stated above are theoretical, and are 
varied in practice by reason of drop in armature conductors and phase 
displacement. In converting from a.c. to d.c, if the current in the rotary 
is in phase with the impressed E.M.F. , armature self-induction has little 
effect ; but with a lagging current, which may be due to under-excitation, 
the induced d.c. E.M.F. is somewhat reduced ; and if the machine be over- 
excited, thus producing a Leading current, the induced d.c. E.M.F. will be 
raised. The same is the case in converting from d.c. to a.c, the a.c. volts 
being down on a lagging circuit. 

The corrections for the theoretical ratios of voltages as shown are, first 
for drop in the armature ; and second, they have to be multiplied by the 
factors shown above. 

Steinmetz says that the current flowing in the armature conductors of a 
rotary is the difference between the alternating current input and the con- 
tinuous current output. The armature heating is therefore relatively small, 
and the practical limit of overload is limited by the commutator, and is 
usually far higher than in the continuous current generator. 

In six-phase rotaries the I 2 R losses of the armature are but 29 % of the 
regular I 2 R loss in the armature as used for d.c. dynamo. 

Kapp shows that width of pole-face has a bearing on the increase in out- 
put of a rotary converter over the same machine used as a continuous cur- 
rent dynamo. He compares the output of two converters, one in which 
the pole-face is two-thirds the pole distance, and another in which it is one- 
half the pole distance. In single-phase converters the output is not equal 
to that of the d.c. dynamo, and two- and three-phase machines are much 
different. 

He gives, in the following table, the percentage of d.c. output of what 
would be the output of the same machine used as a d.c. dynamo. 





Pole-width. 




§ 


i 


rcos — 1 


88% 
81 
73 
63 


95% 


Single-phase \ gj = ;§ ; ; ; ; ; ; ; ; ; ; 
LCos= .7 


88 
80 
70 


( Cos — 1 


138 

128 
117 


144 


Three-phase \ Cos = .9 

(Cos= .8 


137 
126 


»n ( COS — 1 


167 
160 
144 


170 


T wo-or Cos- .9 


167 


four-phase { ^ = % ; v ; ; ; ; ; ; ; ; ; 


153 



To find the voltage required between collector rings on rotary con- 
verters, when 

T— number of turns in series between collector rings, 
* = flux from one pole-piece into the armature, 
/■=. cycles per second, 
E = required E.M.F. 



Then 



For single-phase and two-phase machines 

E = 2.83 T /*$ 10- 8 , 
For three-phase machines 

E — 3.69 T f S> lO- 8 . 



440 THE ROTARY CONVERTER. 

The single-phase rotary lias to be turned up to synchronous speed by some 
external power, as it will not start itself. 

The polyphase rotary will start itself from the a.c. end, but takes a tre- 
mendous lagging current, and therefore, where possible, it should be started 
from its d.c. side. 

The starting of rotaries that are connected to lines having lights also con- 
nected, should always be done from the d.c. side, as the large starting cur- 
rent taken at the moment of closing the switch will surely show in the 
lamps. Polyphase rotaries are sometimes started, as are induction motors, 
by use of a " compensator." 

In starting a rotary , the field circuit must be opened until synchronism is 
reached, after which it is closed. The d.c. side must also be disconnected 
from its circuit, as it is obvious that the current produced is alternating 
until synchronism is reached. Care must be taken to keep the field circuit 
closed when the d.c. side is connected in parallel with other machines, and 
the a.c. side open, or the armature will run away and destroy itself. 

As the change in excitation of the field of a rotary changes the d.c. voltage 
but little, and on the other hand produces wattless currents, the regulation 
of E.M.F. must be accomplished by some other method. This can be done by 
changing the ratio of the static transformer by cutting in and out turns as 
its primary, or by the introduction of self-induction coils in the a.c. leads to 
the rotary. 

The first introduces a complicated set of connections and contacts, but is 
unlimited in range. 

The second method seems especially suited for the purpose, but is some- 
what limited in range. Theoretically the action is as follows : Suppose the 
excitation to be low enough so that the current lags 90° behind the impressed 
E.M.F., the E.M.F. of self-induction lags 90° behind the current, and is 
therefore 180° behind the impressed E.M.F., and therefore in opposition to it. 
On the other hand, if the excitation is large, and produces a leading current 
of 90°, the E.M.F. of self-induction is in phase with the impressed E.M.F. 
and adds itself to it. Therefore, with self-induction introduced in the a.c 
lines, it is only necessary to vary the excitation in order to change the con 
tinuous current E.M.F. A rotary can thus be compounded by using shunt 
and series field, to maintain a constant E.M.F. under changes of load, the 
compounding taking place, of course, in the a.c. lines and not in the field of 
the machine, as usual in d.c. dynamos. 

In handling the inverted converter care must be exercised in starting it 
under load, as it is apt to run away if not connected in parallel with other 
alternators. If they are started from the d.c. side, and have lagging cur- 
rents flowing from a.c. side, this current will tend to demagnetize or weaker 
the fields, and the speed of the armature is liable to accelerate to the dan- 
ger limit. 

A lagging current taken from an inverted rotary, even after having reached 
synchronism, will cause an immediate increase in speed, and if enough lag- 
ging will cause an approach to the danger point. 

Running as a rotary, and converting from a.c. to d.c, the phase of the en- 
tering current has no effect on the speed, this being determined by the 
cycles of the driving generator, nor upon the commutation, simply influen- 
cing the heat in the armature and ratio of voltages slightly. 

Double-current generators are useful in situations where continuous cur 
rent can be used for a portion of the day and the current transferred througl 
the a.c. side to some other district for use in another portion of the day, 
thus keeping the machine under practically constant load. 

The size of double-current generators is limited by the size of the d.c. gen- 
erator that can be built with the same number of poles as a good alternator. 
The heating of the armature depends upon the sum and not the difference 
of the currents, as in the rotary, and the capacity is therefore no greater 
than a d.c. machine of the same total output. 

Automatic compounding of double- current generators is scarcely feasible 
in practice, and the field must be very stable, as the demagnetizing effect of 
the lagging a.c. currents tends to drop the excitation entirely. Such machine? 
run better separately excited. 



ROTARY CONVERTER WINDINGS. 



441 



€O^T£RTER U4H4TIKE WINDINGS. 
Two-Circuit Winding* for Two-Phase Horary Transforms rs. 

The following diagram shows the connections of the four rings to the dif- 
ferent sections of the armature. The connections are made at the commu- 
tator segments at four points, although there are six poles. 




Fig. 49. 

Two-Circuit Winding- for Three -Phase Rotary 
Transform ers. 

The following diagram shows the connections of the three collector rings 
to the continuous current winding of a six-pole dynamo. As in the last fig- 
ure, the rings are connected to points on the commutator at nearly equi< 
distant points. 




Fig. 50. 



442 



ROTARY CONVERTER CONNECTIONS. 



Note, — Connection of Transformer* and Rotary 
Converters. 

In the use of rotary converters, two or more of these machines are some- 
times connected in multiple to the secondary of the transformers, and their 
direct current leads then conducted in multiple to a common bus-bar circuit, 
as shown in Fig. 51. 






UfcSHfcNAr.OK 

I — ^ — I 

rQQOmOQbOQQW 



QfflOOOQOOOO.OWi 



TRANSFORMER 




00006] fffiW] KWlSt 



fOi rOi 



mm mm 4 

ROTARY ROTARY 



Fig. 51. 



Fig. 52. 



With the'above connections, currents are often formed in the rotaries that 

. disturb the point of commutation, and it becomes practically impossible to 

adjust the brushes so they will not spark. Rather than connect across in 

the above manner, it is better that each rotary have its own transformer, or 

at least its own secondary on the transformer, as shown in Fig. 52. 

Current Densities. 

Current leads from brushes to binding-posts, must be ample to produce no 
appreciable drop in voltage. The following table gives current densities, 
etc., for brush-holders, conductors, bolted joints, and switches. 

Average Current Densities for Cross Section and Contact 
Surface of Various materials. 





Material. 


Square Mils, 
per Ampere. 


Amperes per 
Square Inch. 


Cross section i 


Copper wire . . . 
Copper rod . . . 
Copper-wire cable . 
Copper casting . . 
Brass casting . . 


500 to 800 

800 " 1,200 

600 " 1,000 

1,400 " 2,000 

2,500 " 3,300 


1,200 to 2,000 
800 " 1,200 

1,000 " 1,600 
500 " 700 
300 " 400 


Brush contact < 


Copper brush . . . 
Carbon brush . . . 


5,700 " 6,700 
28,500 " 33,500 


150 " 175 
30 " 35 


Switch jaws 


Copper — copper . . 
Brass <gjjf > ; 


10,000 " 15,000 
J 20,000 " 25,090 


67 " 100 
40 " 50 


Screwed contact J 


Copper — copper 

B '«<ta5Sf: : 


5,000 " 8,000 
J 10,000 " 15,000 


120 " 200 
67 " 100 



THE STATIC TRANSFORMER. 

Revised by W. S. Moody and K. C. Randall. 

The static transformer is a device used for changing the voltage and cur 
rent of an alternating circuit in pressure and amount. It consists, essen- 
tially, of a pair of mutually inductive circuits, called the primary and 
secondary coils, and a magnetic circuit interlinked with both the primary 
and secondary coils. This magnetic circuit is called the core of the trans- 
former. 

The primary and secondary coils are so placed that the mutual induction 
between them is very great. Upon applying an alternating voltage to the 
primary coil an alternating flux is set up in the iron core, and this alternat- 
ing flux induces an E.M.F. in the secondary coil in direct proportion to the 
ratio of the number of turns of the primary and secondary. 

Technically, the primary is the coil upon which the E.M.F. from the line 
or source of supply is impressed, and the secondary is the coil within which 
an induced E.M.F. is generated. 

The magnetic circuit or core in transformers is composed of laminated 
sheet iron or steel. The following cuts represent sections of several dif- 
ferent types of single phase transformers. 






m 




i 













I 


V 












I i 




1 


"" 




I 






I 






1_„ 











if" 







; 




! 1 






i 








IL 


J 





Fig. 1. Cores of some American Transformers. 

p = primary winding ; s = secondary winding. 

In those showing a double magnetic circuit the iron is built up through 
and around the coils, and they are usually called the " Shell " type of trans- 



former 



443 



444 THE STATIC TRANSFORMER. 



Fio. 2. Unfinished and Finished Coils for Core Type Transformers 




Flo. 3. Unfinished and Finished Coils for Shell Type Transformers 





Fia. 4. Shell Type Transformer Fio.5. Core Type Transforrae. 
in Process of Construction. in Process of Construction. 



DUTIES OF TRANSFORMERS. 445 

Those having a single magnetic circuit, and having the coils built around 
the long portions or legs of the core, the short portions or yoke connecting 
these legs at each end, are called " core " type of transformer. 

The duties of a perfect transformer are : 

(1) To absorb a certain amount of electrical energy at a given voltage and 
frequency, and to give out the same amount of energy at the same frequency 
and any desired voltage. 

(2) To keep the primary and secondary coils completely isolated from one 
another electrically. 

(3) To maintain the same ratio between impressed and delivered voltage 
at all loads. 

The commercial transformer, however, is not a perfect converter of energy, 
although it probably approaches nearer perfection than any form of appa- 
ratus used to transform energy. The difference between the energy taken 
into the transformer and that given out is the sum of its losses. These 
losses are made up of the copper loss and the core loss. 

The core loss is that energy which is absorbed by the transformer when 
the secondary circuit is open, and is the sum of the hysteresis and eddy cur- 
rent loss in the core, and a slight copper loss in the primary coil, which is 
generally neglected in the measurements. 

The hysteresis loss is caused by the reversals of the magnetism in the 
iron core, and differs Avith different qualities of iron With a given quality 
of iron, this loss varies as the 1.6 power of the voltage with constant fre- 
quency. 

Steinmetz gives a law or equation for hysteresis as follows : 

Wn = r, (fc l ' 6 . 

JFh = Hysteresis loss per cubic centimeter per cycle, in ergs (= 10~» 
joules). 
t) = constant dependent on the quality of iron. 

[f JVr= the frequency, 

V=z the volume of the iron in the core in cubic centimeters, 
P ±z the power in watts consumed in the whole core, 

men P = rjN V (ft 1 * 6 10~ 7 , 



md 



In the construction, the core loss depends on the following factors : 

(1) Magnetic density, 

(2) Weight of iron core, 

(3) Frequency, 

(4) Quality of iron, 

(5) Thickness of iron, 

(6) Insulation between the sheets or laminations. 

The density and frequency being predetermined the weight or amount of 
iron is a matter of design. The quality of the iron is very variable, and up to 
the present time no method has been found to manufacture iron for trans- 
formers which gives as great a uniformity of results as to the magnetic 
losses as could be desired. 

On the thickness of the laminations and the insulation between them de- 
pend the eddy current losses in the iron. Theoretically 1 the best thickness 
of iron for minimum combined eddy and hysteresis loss at commercial fre- 
quencies is from .010" to .015", and common practice is to use iron about 
.014" thick. 

The copper losses in a transformer are the sum of the I 2 B losses of both 
the primary and secondary coils, and the eddy current loss in the conductors. 
In any well-designed transformer, however, the eddy current loss in the 
sonductors is negligible, so that the sum of the I 2 Ii losses of primary and 
secondary can be taken as the actual copper loss in the transformer. 

* Bedell, Klein, Thomson, Elec. W., Dec. 31. 1898. 



446 



THE STATIC TRANSFORMER. 



TRANSFORMER E«*¥ ATIOXS. 

Practically all successful designs of transformers are determined to 
greater or less extent by the method of cut and try. Empirical methods 
are of little value if the designer can obtain data on other successful trans- 
formers for the same kind of work, and base the calculations for the new 
apparatus on the behavior of the old while under test. 

For any transformer or reactive coil : 

Let E — Vmean 2 of the induced E.M.F. 
$ 3= total flux. 
(jy 7 = lines of force per square inch. 
A ra section of magnetic circuit in square inches. 
N == frequency in cycles per second. 
T— total turns of wire in series. 



4,44 =vi = V2X7r 



Then^ = 



4.44 NQT 
10 8 



(1) 



This equation is based on the assumption of a sine wave of electromotive 
force, and is the most important of the formulae used in the design of an 
alternating current transformer. 

By substituting and transposing we can derive an equation for any un- 
known quantity. 

Thus if the volts, frequency, and turns are known, then — 



$ 


Ex 10 8 
~"4.44x^V r x2 7 


But$ 


= <M4 




Ex 10 8 



■ 4.44 X y X T X (R" 



(2) 
(3) 
(4) 



which equation gives at once the cross section of iron necessary for the 
magnetic circuit after we have decided on the total primary turns, and the 
density at which it is desired to work the iron. 

Again, if the volts, frequency, cross section of core, and density ara 
known, we have, transposing equation (4), 



T = 



Ex 10 8 



4.44xATx(fc /, X^ 



1..6 

1.4 
1.2 
1.0 



t: :::::: 3:::: 






± it . 






±_ 4: 
























± 






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SI - -_ s 












zkz s 






xl ~tt 
























S 2 : : : 






£ z ::: : 






X A - 






t / _ 






±v_ _: _ : 






it 






1- _: _ : 






4- - - - 






t _ 






t_ I_ z z 



















16 18 20 22 24 



Fra. 6. 



FEATURES OF DESIGN. 447 

Fig. 6 is a curve giving the total fluxes as ordinates and capacities in K.W- 
as abscissae . This curve represents approximately common practice for a 
line of lighting transformers, to be operated at 60 cycles. 

For any other frequency or for power work, a curve of total fluxes can be 
drawn after three or more transformers have been calculated with quite 
widely differing capacities. 

Magnetic densities in the cores of transformers vary considerably 
with the differerjt frequencies and different designs of various makers. The 
practical limits of these densities are as follows: 

For 25 cycle transformers from 60,000 to 90,000 C.G.S. lines per square inch. 

For 60 cycle transformers from 40,000 to 60,000 lines per square inch. 

For 125 cycles from 30,000 to 50,000 lines per square inch. 

Densities for other frequencies are taken in proportion. 

Current Densities. — Current density cannot be determined except 
in connection with the coil surface exposed for heat radiations, and if, there- 
fore, for any reason, different portions of the winding have relatively differ- 
ent amounts of exposed surface, current densities must be adjusted to give 
equal heat distribution. 

FEATURES OF DESIGN. 

In the design of successful transformers the principal features requiring 
attention are: 

(1) Quality of insulation between primary and secondary windings, 

(2) Temperature rise, 

(3) Regulation, 

(4) Efficiencies, 

(5) Ageing of iron or increase in core loss, 

(6) Power factor and exciting current, 

(7) Cost. 

Insulation. 

No feature of a successful transformer should be given more considera- 
tion than the quality and durability of the insulation used to separate the 
two windings. Good insulation means few burn-outs and interruptions of 
service, safety of customers, and low maintenance. The failure of the 
insulation is fatal to the primary function of the transformer. 

Not only must the transformer withstand the strain when first installed 
or tested by the manufacturer, but during years of continued use after 
being subjected to frequent overloads and probably high temperatures 
for short periods. 

No insulating material has been found which fills the purpose outlined 
above so well as mica, first, because of its being fire-proof, and second, 
because of its high dielectric strength. In a construction where there are 
no sharp corners to insulate, no insulation can surpass mica. 

Next in value as insulators are perhaps varnished or oiled cloths. The 
value of such insulation varies greatly, and depends not only upon the 
quality of the cloth, but more especially on the qualities of the varnish and 
oils used in their manufacture. Their particular value over mica is their 
adaptability for use with coils having sharp or abrupt corners or edges. 

Fiber, pressboard, fuller board, or other artificial boards are lowest in 
the scale of insulations, and are generally used not so much as insulators 
as for mechanical separation. If treated with oil or varnish, however, 
their insulating value is greatly increased. 

For very high voltages no better insulator is known than mineral oils 
properly refined. Oil-filled spaces insulating great differences of potential 
should be sub-divided by partitions to prevent bridging of the space by 
conducting material. 

Temperature. 

Statements regarding temperature rise and method of determining the 
same, mean little unless all the conditions are considered. Measurement 
of temperature by thermometer is superficial and of little value. 

In small transformers in which relatively large coil surface results, the 
temperature rise is quite uniform, and there is little possibility of any 



448 



THE STATIC TRANSFORMER. 



local high temperature in any part of the windings. Temperature meas- 
ured by the resistance method or thermometer on such transformers is, 
therefore, not far from the maximum temperature. 

On large transformers the only effective method of insuring uniform 
temperature is to provide liberal ducts between adjacent portions of the 
winding and between the windings and the core. Such ducts greatly 
increase the cost of a transformer, but experience has shown their necessity. 

Because of the different methods of cooling, transformers are grouped in 
several classes. There are two classes of self-cooled transformers, namely, 
natural draft and self -cooled oil-insulated transformers. 

Natural Draft Transformers. — The natural draft transformer is 
one in which the heat is dissipated by the air passing through the trans- 
former, circulation of which is generated by the rise in temperature of the 
air itself. Such transformers are not suited for out-door installation, and 
are expensive because of the large surface that must be provided for radia- 
tion. This class of transformers is little used in this country, but is very 
common abroad. 

Oil-Cooled Transformers. — The oil-cooled transformer is one in 
which the heat is dissipated by the oil circulating through the transformer 




Fig. 7. 175 K/W. Oil-Insulated Self-Cooling Transformer Complete 
with Case. 



structure. In addition to acting as a heat-conducting medium, it also 
serves to preserve the insulation from oxidation, increasing the breakdown 
resistance of the insulation, and, in a number of insulators, restores the 
insulation in case of puncture. 

The use of oil in insulating a transformer results in a more rapid conduc- 
tion between the transformer proper and its case or tank, and the conse- 
quent lowering of the temperature increases the life of the transformer. 



OIL-COOLED TRANSFORMERS. 



449 



Again, instances are known when the discharge of "atmospheric elec- 
tricity," or lightning at a distance, has punctured the insulation of an oil- 
insulated transformer, in which the oil has flowed in and repaired the 
rupture, which was too small to cause immediate damage. 

This cooling may be effectively increased by making the containing tank 
with vertical corrugations, thus largely increasing the radiating surface. 

The curves in Fig. 8 serve to show the effect on the temperature by 
the use of oil. Curve 1 represents the temperature rise (by resistance 
method) of the small transformer without oil; curve 2, the temperature 
rise of the same transformer with oil; curve 3, the temperature rise of the 
oil; curve 4, the temperature rise of another transformer run with oil; and 
curve 5, the highest temperature rise accessible to thermometer, whose 
actual temperature by resistance is shown in curve 4. 

These curves show very forcibly the value or merit of measuring the 
temperature rise of transformers by resistance method rather than by 







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2 3 4 5 6 7 8 S 

TIME IN HOURS 
CURVES 8H0WING RESULTS Duf TO USE OF OIL IN TRANSFORMERS 



Fig. 8. 



thermometer. The difference of temperature of transformers operated 
with and without oil as shown in these curves is greatly exaggerated in 
larger sizes. 

When the transformers are of such size that sufficient radiating surface 
cannot be had in the tank to dissipate the heat, it becomes necessary to 
provide artificial means for cooling the same. The principal methods 
employed are the use of a forced blast of air and by the circulation of water 
through the coils immersed in oil-cooled transformers. 

The former are known as air-blast transformers and the latter as water- 
cooled. 

Some special forms of water-cooled transformers have been built, wherein 
water has been circulated through the conductor itself. 

Transformers have been constructed in sizes up to about 4000 K.W., using 
water circulation for cooling. 

An Air-Blast Transformer, or one in which ventilation and radi- 
ation of heat is, by means of a blast or current of air, forced through the 
transformer coils and core, is shown in Figs. 14 and 15. In this transformer, 
the coils are built up high and thin, and assembled with spaces between 
them, the air being forced through these spaces. The iron core is also built 
with numerous openings through which the air is forced for cooling pur- 
poses. This style of transformer has been constructed in si^es up to about 



450 



THE STATIC TRANSFORMER. 





m 



1 


~r~ A" ii 


ii 


fc- 


: /QOT^ 




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£ " 


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Fw. 9. 300 K.W. Oil-Insulated 
Water-Cooled Transformer. 



Fig. 10. Water-Cooled Oil- 
Insulated Transformer. 




Fig. 11. 



200 K.W. 22,000- Volt Oil-Insulated, 
Self-Cooling Transformer. 



WATER-COOLED TRANSFORMERS. 



451 




Fia. 12. Water-Cooled Transformer out of Tank. 




Fig. 13. Water-Cooled Transformer in Tank with Switch 
for Voltage Regulation. 





Fig. 14. 250 K.W. Single-Phase Air- 
Blast Transformer. 



Fig.. 15. Section of Air-Blast 
Transformer. 



EFFICIENCIES. 



453 



EFFICIENCIES. 

The efficiency of a transformer is the ratio of the output watts to the input 
watts. Thus 



Efficiency = 



Output 



Output watts _ 
Input watts — Output + Core loss + Copper loss 



The core loss, which is made up of the hysteresis loss and eddy current 
loss, remains constant in a constant potential transformer at all loads 



28000 






1 1 1 1 1 1 II II 1 1 1 1 1 1 1 




















= 


-B 
-C 


TRANSFORMER IRON.AGEING TESTS. 

BYH.F. PARSHALL 
HYSTERESIS IN THE IRON AS RECEIVED 
HYSTERESIS TRANSFORMER AFTER , 

SHORT PERIOD OF LIGHT WORK > 
HYSTERESIS TRANSFORMER AFTER 
THREE YEARS OF HEAVY WORK 


















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MANUFACTURE BY A.H. FORD,AT UNIVERSITY 

OF WISCONSIN. JAN. FEB. MAR. 1897. 

B- TEST ON WAGNER TRANSFORMER , 

FEB. MAR. APR. 1897. 






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DAY8 
RESULTS OF AG~.ING TESTS 



Fig. 17. 



454 



THE STATIC TRANSFORMER. 



while the copper loss, or I 2 R loss, varies as the square of the current in the 
primary and secondary. Methods for determining all the losses are fully 
described in the chapter on transformer testing. 

In a service where a transformer is generally worked at full load while 
connected to the circuit, as in power work, the average or "all-day" effi- 
ciency will be about the same as its full-load efficiency. By " all-day " effi- 
ciency is meant the percentage which the energy used by the customer is of 
the total energy sent into the transformer during twenty-four hours. 

In lighting work the transformers are usually connected to the mains or 













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K. W. CAPACITY 

Fig. 18. Comparative Curves of Core Losses and Regulation, 
Showing the Improvement made in Transformers from 
1897 to 1902. 



are excited the full twenty-four hours per day, while the customer draws 
current from them during from three to five hours in the twenty-four. 
Assuming on an average five hours full load, the losses will be 5 hours I 2 R 
and 24 hours core loss. The calculation of the "all-day" efficiency can, 
therefore, be made by the following formula: 



All-day efficiency = 



Full load X 5 



Core loss X 24 + I 2 R X 5 + Full load X 5 



From this it is evident that while for power work or continuous fulljoad 
the relative amount of the core and copper losses will not affect the " all- 
day " efficiency seriously, yet in the design of transformers which are 
worked at full load only a short time, but are always kept excited, a large 
core loss means a very low " all-day " efficiency. 



MAGNETIC FATIGUE. 



455 



450 




















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INDICATE/? DIFFERENCE BETWE 
TRANSFORMERS OF 1899 & 190 


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12 3 4 5 7.5 10 15 20 25 30 

K. W. CAPACITY 



Fig. 19. Reduction in Core Loss, Illustrating the Reduction in Core 
Loss by the Leading Manufacturers. 



MAGNETIC FATIGUE OH AGEBIG OF IRON AUTO 

ITEEL. 

The subject of ageing is of vast importance. The result of investigations 
by Professor Goldsborough, Mr. William M. Mordey and Mr. S. R. Rouget, 
B.A., led to the following conclusions: 

First. There is unquestionably such a phenomena as ageing. 

Second. A great difference exists in the amount of ageing taking place 
in different qualities of iron and steel when maintained at the same tem- 
peratures. 

Third. This increase in the loss in a given body of iron is dependent 
solely on the temperatures at which it is maintained.- 

Fourth. Within ordinary limits of temperature the tendency to age is 
greater the greater the temperature. 

Fifth. Soft sheet steel is much less subject to ageing than soft sheet iron. 

Sixth. Sheet steel that does not age materially at moderate tempera- 
tures (below 75° C.) can be obtained, but almost any iron or steel ages more 
or less at higher temperatures. 

Seventh. The real cause of ageing has not been discovered. Many of 
the laws governing it have been determined, but there is much room ior 
further study and investigation. 

The following curves (Fig. 20) and Table 1 show results of ageing tests on 
samples of iron from the same sheet of metal heated to different tempera- 
tures. 



456 



THE STATIC TRANSFORMER. 



200 - 










_5_ 


















1 1 1 1 1 I 1 1 I 1 1 1 1 1 1 1 






























Ageing test oh samplesof Iron 
cut from the same Sheet of Metal 






















































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10 15 20 25 

DAYS 

Fio. 20. 



The curve (Fig. 21) shows result of ageing tests taken by Professor 
Goldsborough on a 5 K.W. transformer of prominent make. 

"The ageing tests were made at 1100 volts primary pressure and 60 cycles. 
The core loss was measured at 104 volts secondary pressure. 



Full Load Hours 
115 163 187 221 266 350 494 602 822 
Watts Core Loss 
73.8 73.9 72.2 73.5 73.5 74 73 72.8 73 73.8 

Increase in core loss only 2.7%." 



Test Discon-1 
tinued for 1 822 1403 1858 
a period off 
8 Months. J 75.0 72.6 75.8 




HOURS yvORKiNG UN0E.R FVIX 1.0*0 



Fig. 21. 



The above is the record of an ageing test on a 5000-watt 60-cycle 
Transformer. The test was made in the electrical laboratory ot Purdue 
University, in May, 1900, the pressure wave of the generator being as 
indicated. 



CHANGE OF HYSTERESIS BY PROLONGED HEATING. 457 



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458 



THE STATIC TRANSFORMER. 



Regulation. 

The most important factor in the life of incandescent lamps is a steady 
voltage, and a system of distribution in which the regulation of pressure is 
not maintained to within 2% is liable to considerable reduction in the Hfe 
and candle-power of its lamps. For this reason it is highly important that 
the regulation, i.e., the change of voltage due wholly to change of load on 
the secondary of a transformer, be maintained within as close limits as 
possible. 

In the design of a transformer, good regulation and low core loss are in 
direct opposition to one another when both are desired in the highest de- 
gree. For instance, assuming the densities will not be changed in the iron 
or in the copper, if we cut the section of the core down one-half we decrease 
the core loss one-half. The turns of wire, however, are doubled, and the 
reactance of the coils quadrupled, because the resistance changes with the 
square of the turns in series. 

A well-designed transformer, however, should give good results, both as 
regards core loss and regulation, the relative values depending upon the 
class of work it is to do, and the size of the transformer. 

Comparative Expense of Operating- JL.i rg*e and Small 
Transformers. 

It is obvious that the design of the distributing system has quite as much 
to do with the maintenance of a steady voltage as does the regulation of the 
transformers, and the proper selection of the size of transformers to be 
used requires skilled judgment. 

When transformers were first used it was the custom to supply one for 
each house, and sometimes two or three where the load was heavy. Expe- 
rience and tests soon made it evident that the installation of one large 
transformer in place of several small ones was very much more economical 
in first cost, running expenses (cost of power to supply loss), and regulation. 

Where transformers are supplied one for each house, it is necessary to 
provide a capacity for 80 % of the lamps wired, and allowing an overload of 
25% at times. Where one large transformer is installed for a group of houses, 
capacity for only 50% of the total wired lamps need be provided. For resi- 
dence lighting, where the load factor is always very low, it is often best to 
run a line of secondaries over the region to be served, and connect a few 
large transformers to them in multiple. 

A study of the following curves will show in a measure the results to be 
expected by careful selection and placing of the transformers. The first 
curve, Fig. 22, shows the relative cost per lamp or unit of transformers of 
different capacity, showing how much cheaper large ones are than small 
ones. 



S a 






































I 




























id 

> 1 






V 


































-->— 


— 
























LU 






















I 






























I 











100 200 300 400 500 600 

FIG. 22. Relative Cost of Transformers of Different Capacities. 

The second set of curves (Fig. 23), shows the power saved at different 
loads, and using different sizes of transformers. 

Power factor is the ratio of the actual watts in a line to the volt 
amperes or apparent watts in that line. It is also defined as the cosine of 
the angle of phase displacement of the current from the voltage in the 
circuit. 



TESTING TRANSFORMER. 



459 



The power factor of most commercial transformers is low at no load 
varying from 50% to 70%, while at high loads the power factor is very 




Fig. 23. Relative Efficiency of Large and Small Transformers. 

nearly 100%. For this reason it is better to distribute the transformers 
on tne line so that they will carry load enough most of the time to keen the 
power factor reasonably high. 

TESTIJ¥« Tftl^FOIUIEH. 

The term testing transformer is a commercial one for describing a trans- 
former used in testing the insulation of cables, transformers and other ap- 




Fig. 24. Shop Testing Set. to 12,000 Volts by 200 Volt Steps. 



paratus. Such apparatus is generally tested at a voltage from 2 to 
1U times the working pressure. It is necessary, therefore, to build such 



460 



THE STATIC TRANSFORMER. 



transformers for very high voltages, some having been made for pressures 
as high as 500,000. 

Because of the severe nature of the service to which they are subjected 
it is essential that more than ordinary attention be paid to the insulation 




Fig. 25. 



of the windings so that a minimum potential strain results between adja- 
cent portions, and that sufficient insulation be provided between the two 
windings. 

These transformers are generally of the core type of design, because the 
construction of this type of transformer lends itself more readily to the 



TESTING TRANSFORMER. 



461 



sub-division of the high voltage coils into separate and independent parts 
of few turns, thus reducing the potential strain within such coils to a very 
low figure. 

Such transformers are almost invariably oil-insulated and the best prac- 
tice is to place them in metal cases which are connected to the ground 
to protect the operator against accident from the static induced by the 
high voltage winding. 

Figs. 24 and 26 show two types of this appliance, Figs. 24 and 25 show- 
ing a handy shop testing set with diagram of connections, and Fig. 26 
showing a set for moderately high voltage. 

The only practical way of measuring the high potential generated by 
these transformers is by spark-gap shunted across the terminals of the 



TEST LINE 50 OR 




Flo. 26. S. K. C. High Voltage Testing Set. 



transformer. Ordinarily the spark-gap is set for the desired voltage by 
use of a calibration curve or by preliminary calibration by means of a 
voltmeter connected to the low potential side, the ratio of the transformer 
being known. 

A high resistance should be connected in series with the spark-gap to 
prevent the flow of an appreciable amount of current should the potential 
jump across the needle points: this will prevent the accumulation of high 
frequency voltage which might otherwise result. 



462 



THE STATIC TRANSFORMER. 





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JO 20 30 40, ,50 60 -70 00 90 100 HO IZQ 130 MO /50 160 

Kilo Vqlt3 
Fig. 27. Sparking Distances Across Needle Points. 

Transformer for Constant Secondary Current. 

Several methods have been tried with more or less success to obtain con< 
stant current at the secondaries of transformers. 

The simplest and earliest system for obtaining a constant current in the 
secondary is by means of transformers whose primaries are connected in 

CONSTANT CURRENT LINE 




SERIES TRANSFORMERS 



ooooq_r 



CIRCUIT 
POINTS 



\JJJL^JLT 



REACTIVE 
COIL 



s-arc lamps -* 
Fig. 28. 



series, and a constant current maintained in the primary. This is shown in 
diagram in Fig. 28. Series transformers for this purpose have never been 
very successful, due to the trouble caused by the rise of potential in the 



TYPES OF TRANSFORMERS. 



463 



secondary when opened for any cause. Various devices (Fig. 28), such as 
short-circuiting points separated by a paraffined paper, or a reactive or 
choking-coil connected across the secondary terminals, have been intro- 
duced to prevent any complete opening of the secondary by reason of any 
defect in the lamp or other device connected in the circuit. 

Reactive coils used as shunt devices have been used under different 
names ; as compensators, choking coils, and economy coils. 

A device of this kind has been introduced by the Westinghouse Electric 
and Mfg. Company, and others, for use in street-lighting by series incan- 
descent lamps. It is shown diagrammatically in Fig. 29. The lamp is 



m 



r 3_ ir o i__r > i 

— 1 .tJUUL,y ljte.roi Lc2-£j£J- 



CONSXA'NT 



13 — CT 



Fig. 29. 

placed in shunt to the coil ; when the filament breaks, the total current 
passes' through the coil, maintaining a slightly higher pressure between its 
terminals than when the lamp is burning. It is thus evident that the regu- 
lation of the circuit is limited, due to the excessive reactance of the coils 
when several lamps are taken out of circuit. 

Economy Coils or Compensators. 

A modification of the above is built by several companies for use on ordi* 
nary low potential circuits, where it is desired to run two or three arc 
lamps. It is a single coil transformer, and is shown in Fig. 30, and diagram- 
matically in Fig. 31, same page. If any lamp is cut out or open-circuited, 



D. P. SWITCH 
D. P. FUSE BOX 



COMPENSATOR 




S.P.SWITCH 




Fig. 30. Arrangement of Apparatus for 
use of Economy Coil or Compensator. 



Fig. 31. Westinghouse Econ- 
omy Coil, for A. C. Arc Lamps. 



the current in the main line decreases slightly. As more lamps are cut out 
the remaining lamps receive less current, and it is necessary to replace the 
bad lamps in order to obtain normal current through the circuit. 



464 



THE STATIC TRANSFORMER. 



Transformers for Constant Current from Constant 
Potential. 

The transformers represented in Fig. 32 show a design that will give out 
an approximately constant current when connected to constant potential 

circuits. The transformer has its core 

jy .secondary so designed that there is a leakage 

>£\ I ln c ° RE n x X X XX . P atn for tne flux between the primary 

Co) 1| I Ep • " arc lamp^ ^ I and secondary. This is shown in the 

V^l +3LI b L^- — * — x X ti ' diagram at a and 6. At open second- 

primary J _ 1 ar y circuit there is little or no ten- 

dency for the flux to leak across the 
Fig. 32. Constant-Current or Series S a P- When current flows through the 
Transformer. secondary, thus creating a counter 

magneto-motive force, there is then a 
leakage across this path, and if properly proportioned, this leakage will act 
to regulate the current in the secondary, so that it will be approximately 
constant. 

General Electric Constant Current Transformers. 

The transformer thus described has the disadvantage that its regulation 
is fixed for any transformer and may vary in transformers of the same 
design without any ready means of adjustment. The transformer also 
regulates for constant current over but a limited range in the secondary 
loads. 

The General Electric Company constant-current transformer shown in 
Figs. 35 and 36 is constructed with movable secondary coils, and fixed pri- 
mary coils. 




primary circuit 



J FUSE BOX 

f TUBULAR .PLUG SWITCH 




Fig. 33. Constant-Current Trans- 
former showing Counterweight 
and Primary and Secondary 
Leads from Winding. 



Fig. 34. Connections for Alter 
nating Series Enclosed Arc 
Lighting System, with 50, 75, 
or 100 Light Transformer. 



The weight of the movable coil is partially counterbalanced, so that at 
normal full-load current the movable coil or coils lie in contact (see Fig. 
35) with the stationary coil, notwithstanding the magnetic repulsion between 
them. When, however, one or more lamps are out of the circuit, the in- 
creasing current increases the repulsion between the coils, and separates 
them, reducing the current to normal. (See Figs. 35 and 36.) At mini- 
mum load, the distance between the coils is maximum. The regulation is 
thus entirely automatic, and is found to maintain practically constant 
current, or a departure from constant current if desired. The transformer 
can be adjustea for practically constant current for positive regulation; 



TYPES OF TRANSFORMERS. 



465 



i.e., increasing current from full load to light loads, or for a negative regu- 
lation, i.e., decreasing current from full load t light loads. This adjust- 





Fig. 35. Diagram of Connections. 



Fig. 36. Mechanism of Oil-Cooled Con- 
stant Current Transformer— 100 Lamps. 



ment is obtained by changing the position of a cam from which the counter- 
weights are suspended. The curves shown in Fig. 37 show the range obtained 
in a 100-light transformer. 

The transformers are enclosed in cast iron or sheet iron tanks filled with 
transil oil. The oil, in addition to being an insulating and cooling medium, 
serves to dampen any sudden movement of the secondary coils. 

These transformers are connected to the regular constant potential mains, 

















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LOAD 



Vt 

LOAD 



•A 

LOAD 



fUJ-l 
LOAl 



Fig. 37. 



and the larger siaes are arranged for multiple circuits in the secondary. 
After having been started on a run the transformers need no attention, 
as they are entirely automatic in their action. 

In the Westinghouse constant-current transformer the movable coil is 
partially counter-balanced by a weight or another movable coil, depending 
upon the size of the regulator. A dashpot is arranged to permit free sep- 
aration of the coils, but slow approach. This device is important at starting 
and overcomes the tendency to pump, common to such transformers. 

The full-load efficiency of this type is practically the same as that of a 
constant-potential transformer of the same capacity. The power factor of 
the system at full load is about 85 per cent, due to the reactance of alternat- 
ing arc lamps. At fractional loads the power factors necessarily are much 
tower, and it is therefore not desirable to operate such a system at light load, 



466 



THE STATIC TRANSFORMER. 



RE4CTAIVCE FOR 4LTEH\4TOOJ CIJRREIII 
ARC CIRCUITS. 

For low voltage circuits required on transformers, a modification of the 
constant-current transformer has been devised in the regulating reactance 
connected in series with the line. Fig. 38 shows a typical construction 




Fro. 38. Regulating Reactance Coil by Manhattan General Construction Co. 



adopted by one of the leading manufacturers. It consists of a single coil of 
insulated wire arranged to inclose more or less of one leg of a " W "-shaped 
magnet as shown in the following cut. The coil is suspended from one end 

of a lever and counterbalanced by 
a weight on the other, and so 
arranged that at all points of its 
travel it just balances the varying 
magnetic pull of the coil. 

The arc circuit is connected in 
series with this coil with a switch 
to open the circuit. Without cur- 
rent flowing, the normal position 
of the coil is at the top or off the 
leg of the magnet. When the 
switch is closed, current flows in 
the circuit (and coil), and draws 
the coil down on the leg to a point 
where the reactance of the coil 
holds the current strength at a pre- 
determined point; as, say, 6.6 am- 
peres. It is said that this device 
will maintain a current constant 
within one-tenth of an ampere. 

The losses are the iron losses and 
PR losses in the coil, which, with 
constant current, are the same un- 
der all conditions of load. 

As it is not always, or even 
often, that it is necessary to pro- 
vide for regulation of an arc cir- 
cuit to the extent of its full load, 
the makers have adopted the pol- 
icy of supplying instruments to 
care for but that part of the load 
, , . that is expected to vary, in some 

eases 10% of the circuit and in others 75%, thus avoiding the need for 
Arger apparatus, or for insulation for the total voltage of the circuits. 




Fro. 39. "G. I." Series A. C. Regulator. 



POTENTIAL REGULATORS. 



467 



They claim another advantage in being able to connect the device in one 
leg of the series circuit, and allowing the other end of the circuit to be con* 
nected to the mains at any such point as may be the nearest at hand. 




Fio. 40. 
Potential Regulator** 

An alternating current potential regulator is essentially a transformer hav- 
ing its primary connected across the mains, and its secondary in series with 
the mains. The secondary is arranged so that the voltage at its terminals 
can be varied over any particular range. 




Fio, 41, Diagram of Connections for Single-Phase Potential Regulator, 
Westinghouse Elec. and Mfg. Co. 



468 



THE STATIC TRANSFORMER. 



The several different styles of feeder regulators have been devised, differ- 
ing in principle of operation, but all of them have the primary coil con- 
nected across the mains, and the secondary coils in series with the mains. 

The " Stillwell " regulator, which was designed by Mr. L. B. Stillwell, has 
the usual primary and secondary coils, and effects the regulation of the cir- 
cuit by inserting more or less of the secondary coil in series with the line. 
This secondary coil has several taps brought out to a commutating switch, 
as shown in Fig. 40. The apparatus is arranged so that the primary can 
be reversed, and therefore be used to reduce as well as to raise the voltage 
of the line. It is evident from an observation of the diagram that if two 
of the segments connected to parts of the coils were to be short-circuited, it 
would be almost certain to cause a burn-out. To prevent this, the movable 
arm or switch-blade is split, and the two parts connected by a reactance, 



KAPPS MODIFICATION 




Fig. 42. 

this reactance preventing any abnormal local flow of current during the 
time that the two parts of the switch-blade are connected to adjacent seg- 
ments. The width of each half of the switch-arm must of necessity be less 
than that of the space or division between the contacts or segments. 

As the whole current of the feeder flows through the secondary of the 
booster, the style of regulator which effects regulation by commutating 
the secondary cannot well be designed for very heavy currents because of the 
destructive arcs which will be formed at the switch-blades. To overcome 
this difficulty, Mr. Kapp has designed the modification which is shown in 
Fig. 42. In this regulator the primary is so designed that sections of it can 
be commutated, thus avoiding an excessive current at the switch. This 
regulator, however, has a limited range, as the secondary always has an 
E.M.F. induced in it while the primary is excited ; and care must be taken 
to see that there are sufficient turns between the line and the first contact 
in order to avoid excessive magnetizing current on short circuit. 






FROM 


TO LOAD 


SWITCHBOARD 


SECONDARY -f.| L 


PRIMARY 



Fig. 43. Connections for M. R. 
Feeder Regulator of G. E. Co. 



RAISE 
V0LTAaE_^^2DI» *ER VOLTAGE 

•CONTMCL'INa HAND WHEEL 



Fig. 44. Diagram of Con- 
nections of Feeder Po- 
tential Regulator. 



The General Electric Company have brought out a feeder regulator, in 
which there are no moving contacts in either the primary or secondary, and 
which can be adapted for very heavy currents. This appliance is plainly 
shown in Figs. 43 and 44. The two coils, primary and secondary, are set at 
right angles in an annular body of laminated iron, and the central lami- 



THREE-PHASE REGULATORS, 



469 



nated core is arranged so as to be rotated by means of a worm wheel and 
shaft as shown. 

The change in the secondary voltage, while boosting or lowering the line 
voltage, is continuous, as is also the change from boosting or lowering, or 
vice versa. In this regulator, the change of the secondary voltage is effected 
by the change in flux through the secondary coil, as the position of the 
movable core is changed by the turning of the hand wheel and shaft. There 
are, therefore, no interruptions to the flow of current through either the 
primary or secondary coils, and the regulator is admirably adapted for in- 
candescent lighting service, where interruptions in the flow of current, how- 
ever instantaneous, are objectionable. 

Separate Circuit Regulators, 

Where a number of circuits are run out from the same set ol bus bars, 
regulation of each circuit is provided for by the use of a single coil trans- 
former from various points, on the winding of which leads are brought out 
to a regulator head, from which any part or all of the transformer may be 
thrown into service to increase the pressure on the line. 

Three-Phase Jleg-ulators* 

The regulator described above is suitable only for operation on single- 
phase circuits. The primary is connected in a shunt and the secondary 
in series with the circuits to be controlled. Two or three-phase regulators 
of similar design, but having either primary or secondary on the moving 




H3 



Fig. 45. Three-Phase Induction Potential Regulator. 

core, are commonly used. The voltage in such a design is constant in each 
phase of the secondary winding, but by varying the relative positions of 
primary and secondary the effective voltage of any phase of the secondary 
in its circuit is varied from maximum boosting to maximum lowering. 

Referring to the diagram which represents graphically the voltage of a 
single phase of the regulator, e o = Generator voltage or the E.M.F. im- 
pressed on the primary; a o =» E.M.F. generated in the secondary coils, 
and is constant with constant generator E.M.F.; 6' a* = Secondary E.M.F. 
in phase with the generator E.M.F.; e' a' = Line E.M.F. or resultant of 
the generator E.M.F. and the secondary E.M.F. 

The construction of the regulator is such that the secondary voltage o a 
is made to assume any desired phase position relative to the primary E.M.F., 
as o /, o b, o c, etc. 

When its phase relation is as represented by o /, which is the position 
when the north poles and the south poles of the primary and secondary 
windings are opposite, the secondary voltage is in phase with the primary 
voltage and is added directly to that of the generator. The regulator is 
then said to be in the position of maximum "boost," and by rotating the 
armature with reference to the fields, the phase relation can be changed 
to any extent between this and directly opposed voltages. When the 
voltage of the secondary is directly opposed to that of the primary or gen- 
erator, its phase relation is as represented by o d in the diagram, while o b 
represents the phase relation of the secondary when in the neutral position. 



470 



THE STATIC TRANSFORMER. 



TIIREE-I»1I.4*E TRAMIFORHEB§. 

This type of transformer has been commonly used " abroad " for a long 
time and has recently been introduced into American practice. Such 
transformers differ little from the single-phase designs and may be built in 
either core and shell type. 

The three-phase shell type transformer consists simply of the single- 
phase units so united that considerable of the iron in the core becomes 
unnecessary. This is illustrated by the following cuts. 





Fig. 46. Three-Phase Core 
Type Transformer. 



Fig. 47. Core of Three- 
Phase Core Type 
Transformer. 



A three-phase core type transformer consists of three legs of single-phase 
core transformer placed side by side and united at either end by a yoke 
of the same cross section as each single-phase leg. 




Fia. 48, Cross Section of the Cores and Coils of Three Single-Phase 
Air-Blast Transformers. 



liiiiii 
I Hi 




Fio. 49. Cross Section of the Same Coils Combined in One Three-Phase Air- 

Blast Transformer of a Capasity Equal to the Total Capacity of 

Those Above. 



RATIO OP TRANSFORMATION, 



471 




Fig. 50. Three-Phase Air-Blast 
Transformer in Process of Building. 



Fig. 51. A Typical Three-Phase 
Air-Blast Transformer. 



RATIO OIF Tit AX&JFOmiATIOtf T'X IIIREE.PHASfi 

Transformers are usually built with both their primary and secondary 
coils wound in two or more sections in order to facilitate changes of trans- 
formation ratio. This is especially useful where three transformers are 
used in a three-phase system. Let 

n = ratio of transformation from one section of high-tension side 
to one section of low-tensionside, expressed as an integer; 

Y = total number of sections in series in each arm of the star, high- 
tension side; 

D = total number of sections in series in each arm of the delta, high- 
tension side; 

y, and d, being the corresponding quantities for the low-tension side. 



Then, 



H.T. line volts 
L.T. line volts ' 



yVs + d 



This formula is applicable to combination stars and deltas as well as to 
simple stars and deltas. 

Example. ~ Fig. 52 
shows a combined star 
and delta for the H.T. 
side and a simple star 
for the L.T. side. 



Ratio =» 10 



2\/3 4-3 
3\/3 + 



n = 10, 
Y = 2, 
D = 3, 




-• — •- 



L. T. Side 



Fig. 52. 



472 



THE STATIC TRANSFORMER. 



TRAJfiFORMEB COWtfECTIOHTS. 

Some of the advantages claimed for alternating current systems of dis- 
tribution over the direct current systems is the facility with which the 
potential, current, and phases can be changed by different connections of 
transformers. 

On single-phase circuits, transformers can be connected up to change 
from any potential and current to any other potential and current; but in 
a multi-phase system, in addition to the changes of potential and current, 
the phases can be changed to almost any form that may be desired. 

Single -Phase. 

The connections of the single-phase step-down and step-up transformers, 
having parallel connections, need no explanation. For residence lighting, 
a favorite method of supply is through single-phase transformers with 
three-wire secondaries. A tap is brought out from the middle of the sec- 




BALANCING TRANSFORMER 



Fio. 



53. Arrangement of Balancing Transformer for Three- 
Wire Secondaries. 



ondary winding, this tap connecting to the middle or neutral of the three- 
wire system. In this way a few large transformers can be connected by 
three-wire secondaries in a residence or other district, and will take care of 
a large number of connected lamps. 






4 1000 » 








Fig. 55. Single-Phase, 
Fig. 54. Single- with Three- Wire Sec- Fig. 56. Two- Fig. 57. Three- 
Phase. ondary, Useful for Phase, Four Wire, Two- 
Residence Circuits. Wires. Phase. 



TRANSFORMER CONNECTIONS. 



473 



Kapp shows a modification of the three-wire circuits, in which the out- 
side wires are fed by a single transformer, and the neutral wire is taken 
care of by a balancing transformer, connected up at or near the center of 
distribution. The capacity of the balancing transformer need be but half 
the greatest variation in load between the two sides. 

Some makers of transformers have the connection board in their trans- 
formers so arranged that the two primary coils may be connected either in 
series or parallel by mere changes of small copper connecting links, so 
that the same transformer can be connected up for either 1000- or 2000-volt 
circuits, and the secondary for either 50 or 100 volts. 

Two-Phase. 

The plain two-phase or quarter-phase connection (Fig. 56) is simply two 
single transformers connected to their respective phases, the phases being 
kept entirely separate. In the three-wire quarter-phase circuit, one of the 
leads can be used as a common return, as shown in ' g. 57. 

Three-Phase. 

The three-phase connections shown in diagram 58 are known as the 
delta connections, and are of great advantage where continuity of service 
is very important. The removal of any one transformer does not interrupt 




Wj nm nrain 





Fig. 58. Three-Phase 
Delta Connection. 



Fig. 59. Three-Phase 
Star Connection. 



the three-phase distribution, and the removal of two transformers still 
admits of power transmission on a single phase of the circuit. 

The Y or star connection, as shown in diagram 59, has one of the 
terminals of each primary and secondary brought to a common connec- 
tion, the remaining three terminals being brought to the main line and the 
distributing lines. The advantage of the star connection over the delta con- 
nection is, that for the same transmission voltage each transformer is wound 
ior only 58% of the line voltage. In high-voltage transmission this admits 
of much smaller transformers being built for high potentials than is possi- 
ble with the delta connection. 



474 



THE STATIC TRANSFORMER. 



Arrangement of Transformers for Stepping* Up and Down 
for .Long- Distance Transmission. 

Figures GO, 61, and 62 show diagrammatically the connections for adapting 
three-phase transmission to quarter-phase generators, with interchangeable 
and non-interchangeable transformers. 



GENERATOR 



STEP UP 
TRANSFORMER 




8TEP DOWN 
TRANSFORMEP 



Fig. 60. Changing Quarter-Phase to Three-Phase, 
Non-Interchangeable Step-up Transformers. 




Fig. 61. Changing Quarter- 
Phase to Three-Phase, and 
back to Quarter-Phase. 
All Transformers Inter- 
changeable. 



-«2000-V> 
SLSLMJULT 



2000Vt* 
tfiJUUlSJiai STEP UP 



nrjprafftfri transformers 



0000->:<10000V7> 



MV&1*-*-\sxjjxI*-L*SM*Jm) 



^T^^^ 



-110V— 
-110-V— 



Fig. 62. Changing Quarter- 
Phase to Three-Phase. All 
Step-up Transformers Inter- 
changeable. 



TRANSFORMER CONNECTIONS. 



475 



Three-Phase to Six-Phase Connections. 

A rotary converter wound for six-phase has a greater capacity for work 
than the same machine wound for three-phase. Three-phase transmission, 
however, is very economical, and in Figs. 63 and 64 is shown a diagram by 
which six phases can be obtained from three phases by the use of only three 
transformers. 

Each transformer has two secondary coils. One secondary of each trans- 
former is first connected into a delta, then the remaining secondary coils are 



UwwwJ Iwvw w J UvwwvJ SMA/VV^^ 

n/VvWn fVV\AAAa nAA/W\n 



( AAAAA ) /W\A^ 

'PI f 





Six- Phase A 



Figs. 63 and 64. Three-Phase to Six-Phase Connection. 



connected up into a delta, but in the reverse order of the first delta. This 
is an equivalent of two deltas, one of which is turned 180° from the other. 
In the diagram ABC represents one delta, and DEF the other. 



Kvwwf 



! ' .J 



W\AAA/J 



s.j W WW L n A-WWW^ pAMA/W-^ 



Wvww' 




Fig. ( 



Diagrams of Connections for Changing from Three-Phase to 
Six-Phase. 



In the same way the two secondaries can be connected up Y, and one 
Y turned 180° to obtain six phases. The disadvantage of Y connec- 
tion, however, is that in case one transferrer is burned out, it is not possi- 
ble to continue running, as can be done with delta connections 



476 



THE STATIC TRANSFORMER. 



Methods of Connecting: Transformers to Rotary 
Converters. 



vwwwvwJ VwwwvwJ 

A/VWA 




Fig. 66. Two-Phase. 
/VwWa\A/\ WyVWA 




FIG. 68. Three-Phase J. 

WwAwJ Wm\W^ IwWWwW 

^^^^^^ ,, a/vw\a 2, /wyvvv^ 




Fig. 70. Six-Phase Diametrical. 

■ WMNVWWAMM/W VVWWVWWVVW 



M/VWNAAA K/WWW\ 


iL -H 


1 2' c «fcjv|3- 
si. J?2 



FIG. 72. Six-Phase T. 



Wwwwwv wvwvvAW Vwwvww/ 
i3 



^wwv t 7^A^^A-ysAA^J 




Fig. 67. Three-Phase A. 
VwwW IvwwW IwwwJ 

kvw\ kA/vw,tww\ 

2| 3 




Fig. 69. Three-Phase y. 

•WwwwJ UwvJ Uvwww 

l5_ 



Iwwi^A/wvyww] 



|WW\ /WW^ j 



2'f 



L 




y^) 



Fig. 71. Six-Phase A. 

Wwwww/ WW. tvvwwvv! 
JVWVy twwy IvwVvil 



WW^ /VV\AA M/V\A 




L 



Fig. 73. Six-Phase y. 



CONVERTER AND TRANSFORMER CONNECTIONS. 477 



A/N/N, 



^0 







rj 






J™^*^™* 



Fig. 74. Three Transformers Arranged in Inter-connected Star, Operating 
a Three-Phase Rotary Converter on a D. C. Three-Wire System. 

Converter and Transformer Connections. 

The ,, Scott" connection is used a great deal in transmissions and distri- 
butions (See Fig 75.) One transformer is designated the main, and the 
other the teaser. Two transformers are required. They are made exactly 
alike, so that with proper connections either may be used as mam or teaser. 
The winding is provided with a 50% tap and with taps so that 86.6% of 
the winding may be used. 1-2-3 are three-phase voltage, A~A one-phase, 
B-B' the other of the two-phase circuit. Reference to the small diagram 
shows the reason for using 86 6% of winding of one transformer; also the 
necessity for the 50% tap. 



Teaser 




Hvwwwv^ 

Main 100% 




/oo% 



Fw. 75. 




Fig. 76. 



WE1SIBOO POWER O 8IX-PHASE CIBCVIII. 

Use two pairs of wattmeters, each pair connected to one of the three- 
phase circuits as shown in Fig. 76. If power factor is less than 60% one 
meter of each pair will read negative. The algebraical sum of the read- 
ings of each of the two pairs will be the result required. 



478 



THE STATIC TRANSFORMER. 



Y OH A COOTVECTIOl? OF TRANSFORMERS. 

(F. 0. Blackwell. Trans. A. I. E. E M 1903.) 
Transformers. 

Assuming that three transformers are to be used for a three-phase power 
transmission and that the potential of the line is settled, each of the trans- 
formers, if connected in Y, must be wound for — — or about 58 per cent of 

V3 
the line potential, and for the full line current. If connected in A, each 
transformer must be wound for the line potential and for 58 per cent of the 
line current. The number of turns in the transformer winding for Y 
connection is, therefore, but 58 per cent of that required for A connection, 
to avoid eddy current losses that occur when the cross section of the con- 
ductor is too large. 

The Y connection requires the use of three transformers, and if any- 
thing goes wrong with one of them the whole bank is disabled. With the 
A connection, one of the transformers can be cut out and the other two 
still deliver three-phase power up to 86.6 per cent of their aggregate capacity, or 
66.6 per cent of the capacity of the entire bank. 




Fio. 77. Step-down Transformer for 4000 Volt Y Distribution. 

Combined three-phase transformers are now made of any size and are prefer- 
ably Y connected on the high potential side. 

Grounding* the Neutral. 

If the common connection of transformers joined in Y is grounded, the 
potential between windings and the core is limited to 58 per cent of that 
of the line. 

Under normal conditions, the potential between any conductor of a 
three-phase transmission circuit and the ground is 58 per cent of the line 
potential, with either Y or A connection, but the neutral may drift so as 
to increase the potential with an ungrounded system. If one branch is 




Fig. 78. Step-down Transformer for 200 Volt Y Distribution. 



partly or completely grounded, the potential between the other two branches 
and the ground is, of course, increased and may be the full line potential. 
With a grounded neutral Y system, a ground is a short circuit of the trans- 
formers on the grounded branch, and the transmission becomes inoperative. 



CONNECTION OF TRANSFORMERS. 



479 



From the point of view of safety to life and prevention of fires this is a 
desirable condition, especially if the low tension distribution is also grounded. 
If the high tension circuit makes contact with the ground or low potential 
system, it can be immediately cut out by fuses or automatic circuit breakers. 

The difficulty is that a power transmission with grounded neutral is 
likely to be frequently shut down by temporary grounds, such as would be 
caused by a tree blowing against one of the wires. Even if the circuit is 
not opened, the drop in the pressure due to the sudden "short" on the 
line will cause synchronous apparatus to fall out of step. 

Unstable Neutral. 

If two transformers are connected in series, there is no certainty that 
they will divide the potential equally between them. A system in which 
all the electrical apparatus is connected in Y has somewhat the same char- 
acteristics. The neutral may drift out of its proper place and there will be 
unequal potentials between it and the three conductors of the circuit, due 
to unequal loading and differences in the transformers or transmission cir- 
cuits. Such unbalancing would cause unequal heating of the transformers, 
and if a four-wire three-phase system of distribution were employed, would 
seriously interfere with the regulation of the voltage. If transformers, 
therefore, have Y secondaries, it is desirable that the primary should be 
A connected. Two systems in common use with which A primary wind- 
ings should be used, are shown in Figs. 77 and 78. 

Rise of Potential. 

The high potential windings of transformers are necessarily of high 
reactance, and if left in series with a circuit of large capacity, as shown in 
Figs. 79, 80, 81, and 82, the leading charging current flowing over the react- 
ance may set up extraordinarily high pressures. Figs. 79 and 80 represent 
Y-connected banks of three transformers each connected so as to cause such 



rOi 



-mw- 



rWWW- 




Fiq. 79. 



Fig. 80. 



a rise of potential. In Fig. 79 the primary of one transformer is excited by 
a generator, the primary of the other two transformers being open-circuited. 
In Fig. 80 the primary of one transformer is open-circuited, the other two 
being connected to the generator. Figs. 81 and 82 show T-connected banks 
of two transformers, which might be used to transform from either two- 
phase or three-phase to three-phase or vice versa, and are similar in action 
to Fig. 79. If in anyone of Figs. 79, 80, 81 and 82 the secondaries are con- 
nected to a long distance transmission circuit, a pressure of many times the 
normal potential will beset up between A and B, and between B and C, that 
between A and C not being affected. 

It is theoretically possible for a potential 100 times that for which a trans- 
former is wound, to be caused by opening the primary switches of one or 
more of the transformers of a bank connected in Y before the secondary 
switches are used. Actually, the current jumps across the insulation at 
some point in the system before there car. be any such increase in pressure. 
If there are a number of banks of transformers in parallel, this phenomena 
cannot occur except when all but one bank are disconnected. This source 
of trouble could be obviated by employing oil switches on the high poten- 



480 



THE STATIC TRANSFORMER. 



tial side which disconnect the line before the low tension switches are 
used, or by triple pole switches on the primary which open all three branches 
of vhe bank of transformers at once. 

The selection of Y or A connection of transformers for long distance 




r-^ V^ I 1 — 'waaw B 



Fig. 8i. 



Fig. 82. 



transmissions should only be determined after a careful consideration of 
the conditions in each case. 

There is little choice between Y or A without a grounded neutral. 

Note. — For further information on this subject [see discussion on this 
paper in Proceedings of A. I. E. E. for 1903. 

CcJtLXEIl AJL ELECTRIC COMPANY ^EBCIH V 
ARC RECTIFIER!. 



H 



GH 



© 



-WWWWAMr- 

TRANSFORMER 

-A/WW\AAA- 

A.C. SUPPLY 



(By P. D. Wagoner.) 

A detailed idea of the operation of the mercury arc rectifier circuit may 
be obtained from Fig. 83. Assume an instant when the terminal H of the 
supply transformer is positive, the anode A is then positive and the arc is 
free to flow between A and B, B being the mercury cathode. Following 

the direction of the arrows still further the 
I current passes through the load J, through 

the reactance coil E and back to the nega- 
tive terminal G on the transformer. A little 
later, when the impressed electromotive 
force falls below a value sufficient to. main- 
tain the arc against the counter electro- 
motive force of the arc and load, the 
reactance E, which heretofore has been 
charging, now discharges, the discharge 
current being in the same direction as 
formerly. This serves to maintain the arc 
in the rectifier until the electromotive force 
of the supply has passed through zero, 
reverses and builds up to such a value as 
to cause A' to have a sufficiently positive 
value to start an arc between it and the 
mercury cathode B. The discharge circuit 
of the reactance coil E is now through the 
arc A'B, instead of through its former 
circuit. Consequently the arc A'B is now 
supplied with current, partly from the trans- 
former and partly from the reactance coil E. 
The new circuit from the transformer is 
indicated by the arrows inclosed in circles. 
The amount of reactance inserted in the 
circuit reduces the pulsations of the direct 
current sufficiently for all ordinary com- 
mercial purposes. Where it is advisable to still further reduce the ampli- 
tude of the pulsations, as, for instance, in telephone work, this is done with 
very slight reduction in efficiency by means of reactances. 




t© 



F E 



Fio.83. Rectifier Connections 
Shown Diagrammatically. 



WESTINGHOUSE MERCURY ARC RECTIFIER OUTFITS. 481 



wssraveuaoijss: merccry arc rectifieh 

OUTFITS. 

For Arc Lamps* 

These outfits are a development of the constant current transformei 
adapted for use with the mercury rectifier, receiving alternating current at 
a constant potential, and delivering a constant direct current. By a special 




J^flQO.PAQ.Q.Qfl.ri"-- 



.QQ.Q.O.QQ.QQQQft. 




Fig. 84 and Pig. 85. Diagrams of Westinghouse Mercury Arc Rectifier. 

arrangement of coils the usual sustaining reactance is omitted, resulting 
in reduced floor space and an improved efficiency. A boiler iron tank 
with cast iron cover, two alternating currents and two direct currents leads, 
describes the simple and rugged appearance of an outfit. (See Fig. 84.) 

The connections (Fig. 85) explain the operation. P-P and S-S are respec- 
tively the primary and secondary; ST the starting transformer, R the 
rectifier, and A the auxiliary coil for exciting the starting transformer. 



«| — -mm i , . » mmmmm .smj-. < ' - 

5 



Fio. 86. 

The outfit is started by tipping the bulb, causing a spark between the 
terminals of the starting transformer as the current path through the 
mercury is interrupted. This breaks down the high resistance of the nega- 
tive electrode and permits the establishment of the direct current. 

The bulb is carried in a box which is easily slid in or out between guides 
to the bottom of the containing tank, thus making the bulb replacement a 
matter of but a few moments. 

Simple variable weights permit of adjusting the transformer so as to 
deliver its exact rated direct current (Fig. 86), at all loads. 

The power factor at full load averages over 70 per cent and the efficiency 
well over 90 per cent for all sizes of rectifier outfits. These are regularly 
built in 25, 35, 50, 75 and 100 light capacities, either 25 or 60 cycles, for 
2200 V., 6600 V., 11,000 V., and 13,200 V. circuits. 



482 



THE STATIC TRANSFORMER. 



For Battery Charging:* 




Fig. 87. Westinghouse Mercury 
Arc Kectifier for Battery 
Charging. 



These outfits are intended to operate 
from low constant potential circuits and 
deliver a constant D. C. voltage, varying 
from 5 to 125 volts, according to design. 

Fig. 87 indicates a method of connec- 
tion which is essentially the same as for 
the arc lighting outfits. SR is a starting 
resistance, for the rectifier; MN, the auto- 
transformer, BB f the D. C. terminals, and 
A A ' the A. C. terminals. 

These outfits are started by tipping the 
bulb. A spark due to interrupting the 
current in the starting resistance breaks 
down the high negative electrode resist- 
ance, permitting the direct current to be 
established. In this outfit, like the arc 
outfit, a special arrangement of coils per- 
mits the omission of the usual sustaining 
coil. The D. C. voltage is varied by 
changes in the connection to the auto- 
transformer, or by changes in the A. C. 
impressed voltage made by an adjustable 
series reactance. Control panels carrying 
instruments, control dial, circuit breaker, 
etc., are furnished. Thirty amperes, 110 
volts, is at present the maximum capacity 



for which these outfits are built, for either 25 or 60 cycle service. 
TRANSFORMER TESTING. 

Although the standard types of transformers of to-day are made on lines 
found by long experience to be the best for all purposes, and are subject to 
careful inspection and test at the factory in most cases, yet the various 
makers have such different ideas as to the value of the different points, 
that in order to obtain fair bids on such appliances when purchased, it is 
always best to prepare specifications, and the buyer should be prepared to 
conduct or check tests to determine whether the specifications have been 
fulfilled. Large stations should have a full outfit of apparatus for conduct- 
ing such tests ; but smaller purchasers can do quite well by having a compe- 
tent superintendent, or by hiring an outside engineer to witness the tests at 
the factory. It is not always necessary to put each individual transformer 
through all the tests, but the break-down test for insulation should be ap- 
plied to all. 

Prof. Jackson gives the following requirements for guaranties of trans- 
formers. 

Iron loss for 1000-volt transformers and for frequencies over 100 as 
follows : 



Capacity. 


Iron Loss. 


Exciting Current. 


1000 watts 

1500 watts 

2000 watts 

2500 watts 

4000 watts 

6500 watts 

17500 watts 


30 watts 

40 watts 

50 watts 

60 watts 

80 watts 

100 watts 

150 watts 

• 


.055 amperes. 
.080 amperes. . 

.150 amperes. 
.200 amperes. 



For frequencies less than 100 it may be advisable to allow 10 
to avoid excessive cost. 



Note. 
year. 



higher loss 
Guaranties for iron loss should cover ageing for at least one 



TRANSFORMER TESTING. 483 

Drop in secondary pressure not to exceed 3 % between no load and full 
load. 

Rise of temperature after 10 hours' run under full load, 70° F. 
(about 40° C). 

Note. — This measurement was probably meant by Professor Jackson to 
be made by thermometer. It is better to take the rise by resistance meas- 
urement, in which case the allowable temperature is 50° C. 

Disruptive strength of insulation after full-load run, between 
coils and between primary coil and iron, at least 10 times the primary volt- 
age. Insulation resistance to be not less than 10 megohms, and guaranteed 
not to deteriorate with reasonable service. 

Note. — See previous matter as to test voltage. 

Exciting- current for 1000-volt transformers not to exceed values 
given in the above table, when the frequency is above 100. The exciting 
current increases as the frequency decreases, and varies inversely as the 
voltage. For intermediate capacities proportional values may be expected. 

He further says : " Transformers which do not meet the insulation and heat- 
ing guaranties are unsafe to use upon commercial electric lighting and motor 
circuits, while those which do not meet the iron loss, regulation, and exciting 
current guaranties icaste the company's money." 

The characteristics of a transformer, to be determined by tests, are as 
follows : 

(1) Insulation strength between different parts. 

(2) Core loss and exciting current. 

(3) Resistances of primary and secondary and PR. 

(4) Impedance and copper loss, direct measurement. 

(5) Heating and temperature rise. 

(6) Ratio of voltages. 

(7) Regulation and efficiency, which may be calculated from the results 
of tests (2), (3), and (4), or may be determined directly by test. 

(8) Polarity. 

The instruments required to make these tests should be selected for each 
particular case, and consist of ammeters, voltmeters, and indicating watt- 
meters. 

For central station work, the following instruments will suffice for nearly 
any case which may come up in ordinary practice. 

A. C. Voltmeter, reading to 150 volts, and with multiplier to say 2500 volts. 

A. C. Ammeter, reading to 150 amperes, with shunt multiplier if necessary 
to carry the greatest output. 

Indicating wattmeter, reading to 150 or 200 watts. 

Note. — For full data and examples of transformer testing, see pamphlet 
No. 8126, " Transformer Testing for Central Station Managers," by Gen- 
eral Electric Company, and Westinghouse Pamphlet No. 7035. 

Insulation Test. 

This is the simplest and most important test to be made, for the reason 
that one of the principal functions of a transformer is its ability to thor- 
oughly and effectually insulate the secondary circuit from the primary 
circuit. 

Tests of the insulation of practically all high-potential apparatus are now 
carried out by high pressure, rather tnan by test of the insulation resistance 
by galvanometer. Some insulations will show a very high test by galva- 
nometer, but will fail entirely under test with a voltage much exceeding that 
at which it is to be used. On the other hand, it is not uncommon to find 
insulation such that, while the galvanometer tests show low resistance, it 
will not break down at all under the ordinary voltages. For this reason, it 
is common practice among manufacturers of transformers to apply a mod- 
erately high voltage, from two to three times the working voltage, for a 
short period, usually about one minute. 

The Committee on Standardization of the A. I. E. E. has given certain 
voltages which they recommend to be used in the testing of all electrical ap- 
paratus, and the tables and methods of application for the testing of trans- 
formers will be found in paragraphs Nos. 217 to 221, both inclusive in tiie 



484 



THE STATIC TRANSFORMER. 



latest revision of the rules of that Committee which will be found elsewhere 
in the book. 

In standard transformers these insulation tests should be (1) between pri- 
mary and secondary, and between primary and core and frame ; (2) between 
secondary and core and case. 

To obviate any induced potential strain, the secondary should be grounded 
while making the test between the primary and secondary, and between 
primary and core and case. 

In testing between the primary and secondary, or between the primary 
and core and frame, the secondary must be connected to the core and 

It is also important that all primary leads should be connected together 
as well as all secondary leads, in order to secure throughout the winding 
a uniform potential strain during the test. 

Note. — See index for sparking-gap curve, and use new needles after every 
discharge. 

From one point of view, the factor of safety of the secondary need not be 
greater than that of the primary, and if 10,000 volts is considered a sufficient 
test for a 2000-volt primary, 1000 voits might be sufficient for a 200-volt sec- 
ondary. But a thin film of insulation may easily withstand a test of 1000 

volts, although it is so weak mechani- 




O 



CONNECT CALIBRATING 
VOLTMETER BETWEEN 
A AND B 



104 OR 52 VOLT MAINS 



Fig. 88. 



cally as to be dangerous. A 200-volt 
secondary should therefore be tested 
for at least 2500 volts in order to guar- 
antee it against breakdown due to 
mechanical weakness. 

The duration of the insulation test 
may vary somewhat with the magni- 
tude of the voltage applied to the 
transformer. If the test is a severe 
one, it should not be long continued; 
for while the insulation may readily 
withstand the momentary applica- 
tion of a voltage five or ten times the 
normal strain, yet continued applica- 
tion of the voltage may injure the in- 
sulation and permanently reduce its 
strength. 

Attention has been called to the fact 
that in testing between the primary 
and the core or the secondary, the sec- 
ondary should be grounded. In test- 
ing between one winding and the core, for example, an induced potential 
3train is obtained between the core and the other winding which may be 
much greater than the strain to which the insulation is subjected under 
normal working conditions, and greater therefore than it is designed to 
withstand. In testing between the primary and the core, the induced po- 
tential between the secondary and the core may be several thousand volts, 
ind the secondary may thus be broken down by an insulation test applied 
to the primary under conditions which do not exist in the natural use of 
the transformer. 

Attention is further called to the fact that during the test all primary 
leads as well as all secondary leads should be connected together. If only 
one terminal of the transformer winding is connected to the high potential 
transformer, the potential strain to which it is subjected may vary through- 
out the winding, and may even be very much greater at some point than at 
the terminals to which the voltage is applied. Under such conditions the 
reading of the static voltmeter affords no indication of the strain to which 
the winding is subjected. 

Indications which are best learned by experience reveal to the operator 
the character of the insulation under test. The transformer in test requires 
a charging current varying in magnitude with its size and design. From 
the reading of the ammeter, placed in the low potential circuit of the test- 
ing transformer, the charging current may be ascertained. It will increase 
as the voltage applied to the insulation is increased. 

If the insulation under test be good there will be no difficulty in bringing 
the potential up tc the desired point by varying the rheostat. If the insula- 



TRANSFORMER TESTING. 



485 



tion be weak or defective, it will be impossible to obtain a high voltage 
across it, and an excessive charging current will be indicated by the am- 
meter. 

Inability to obtain the desired potential across the insulation may be- the 
result merely of large electrostatic capacity of the insulation and the conse- 
quent high charging current required, so that the high potential trans- 
former may not be large enougn to supply this current at the voltage 
desired. 

A breakdown in the insulation will result in a drop in voltage indicated 
by the electrostatic voltmeter, an excessive charging current, and the burn- 
ing of the insulation if the discharge be continued for any length of time. 

Core JLoss and Exciting Current. 

In taking measurements of core loss and exciting current, the instruments 
required are a wattmeter, voltmeter, and ammeter. 

One of the two following described methods for connecting up the instru- 
ments is usually employed, although several others might be shown. These 
methods differ only in the way of connecting up the instruments, and are as 
follows : 

UEethocl 1. — The voltmeter and pressure coil of the wattmeter are con- 
nected directly to the terminals of the test transformer. When the pressure 
of the voltmeter is at the standard voltage the reading of the wattmeter will 
be the core loss in watts. It is evident from an inspection of diagram 89 
that the wattmeter will indicate, in addition to the watts consumed by the 
test transformer, the I 2 R or copper loss in both the pressure coil of the 
wattmeter and voltmeter. This error, however, being constant for any 
pressure, is easily corrected. This method is very good for accurate results, 
and where the quantities to be measured are small it is most desirable. 



§P 



111 — wvw 



^J> 



VARIABLE 
RESISTANCE 




TEST TRAN8 



Fig. 89. Core Loss (Method 1). 

Method 2. —The current coils of the wattmeter are inserted between 
a terminal of the test transformer and the terminal of the voltmeter and 
pressure coil of the wattmeter (see diagram 90). In this method the error 
introduced is the I 2 R loss in the current coil of the voltmeter. This is a 
very much smaller error than in Method 1, but does not allow of an easy or 
accurate correction, and the results obtained by it must, therefore.be taken 
without correction. For this reason Method 2 is more convenient, and for 
the measurement of large core losses, and for commercial purposes, it is 
sufficiently accurate. 

VARIABLE 

SWITCH RESISTANCE 

-NAAA/W- 




WATTMETER TEST TRANS 



Fig. 90. Core Loss (Method 2). 
Core losses and exciting current should be measured from the low-poten- 
tial side of the transformer to avoid the introduction of high voltage in the 
test. 

Notes on Core Loss and Excitation Current. 

In an ordinary commercial transformer, a given core loss at 60 cycles may 
consist of 70 per cent hysteresis and 30 per cent eddy current loss, while at 
125 cycles the same transformer may have 55 per cent hysteresis loss and 45 
per cent eddy current loss. 



486 THE STATIC TRANSFORMER. 

The core loss is also dependent upon the wave form of the impressed 
E.M.F., a peaked wave giving somewhat lower core losses than a flat wave. 
It is not uncommon to find alternators having such a peaked wave form 
that the core loss obtained, if the transformer is tested with current from 
them, Avill be 5 per cent to 10 per cent less than that obtained if the trans- 
former is tested from a generator giving a sine wave. On the other hand, 
generators are sometimes obtained which have a very flat wave form, so 
that the core loss obtained will be greater than that obtained from the use 
of a sine wave. 

The magnitude of the core loss depends also upon the temperature of the 
iron. Both the hysteresis and eddy current losses decrease slightly as the 
temperature of the iron increases. It is well known that if the tempera- 
ture be increased sufficiently, the hysteresis loss disappears almost entirely, 
and since the resistance of iron increases with the temperature the eddy 
current losses necessarily decrease. In commercial transformers, an in- 
crease in temperature of 40° C. will cause a decrease in core loss of from 5 
per cent to 10 per cent. An accurate statement of core loss thus necessi- 
tates that the temperature and wave form be specified. 

If, in the measurement of core loss, the product of impressed volts and 
excitation current exceeds twice the measured watts, there is reason to 
suspect poorly constructed magnetic joints or higher iron densities than are 
allowable in a well-designed transformer. 

Mea§urement of Resistance. 

Resistance of the coils can be measured by either the Wheatstone Bridge 
or Fall of Potential Method. 

For resistances below one or two ohms it is generally more accurate to use 
the Fall of Potential Method. 

Resistances should always be corrected for temperature, common prac- 
tice being to correct to 20° centigrade. For pure soft-drawn copper this cor- 
rection is .4 % per degree centigrade. Readings should be taken at several 
different current values, and the average value of all the readings will be 
the one to use. (See Index for correction for rise of temperature.) • 

Having obtained the resistance of the primary and secondary coils, the 
PR of both primary and secondary can be calculated ; the sum of the two 
being (very nearly) equal to the copper loss of the transformer. If it is 
preferred to measure the copper loss directly by wattmeter, then we must 
make test No. 4. 

The fall of potential method is subject to the following sources of error : 

(1) Witeh the connections as ordinarily made the ammeter reading includes 
the current in the voltmeter, and in order to prevent appreciable error the 
resistance of the voltmeter must be much greater than that of the resistance 
to be measured. If the resistance of the voltmeter be 1000 times greater, an 
error of ^ of 1 per cent will be introduced, while a voltmeter resistance 100 
times the coil's resistance will mean the introduction of an error of 1 per 
cent. Correction of the ammeter reading obtained in (3) may thus become 
necessary, but whether or not it be essential will depend upon the accuracy 
desired. (See example below.) 

(2) The resistance of the voltmeter leads must not be sufficient to affect 
the reading of the voltmeter. 

(3) Since the resistance of copper changes rapidly with the temperature, 
the current used in the measurement should be small compared with the 
carrying capacity of the resistance, in order that the temperature may not 
change appreciably during the test. If a large current is necessary, read- 
ings must be taken quickly in order to obtain satisfactory results. If a 
gradual increase in drop across the resistance can be detected within the 
length of time taken for the test, it is evident that the current flowing 
through the resistance is heating it rapidly, and is too large to enable accu- 
rate measurement of resistance to be secured. 

It is quite possible to use a current of sufficient strength to heat the wind- 
ing so rapidly as to cause it to reach a constant hot resistance before the 
measurement is taken, thus introducing a large error in the results. Great 
care should be taken, therefore, in measuring resistance to avoid the use of 
more current than the resistance will carry without appreciable heating. 

(4) Considerable care is necessary to determine the temperature of the 
winding of the transformer. A thermometer placed on the outside of the 
winding indicates only the temperature of the exterior. The transformer 



TRANSFORMER TESTING. 



487 



should be kept in a room of constant temperature for many hours in order 
that the windings may reach a uniform temperature throughout. The 
surface temperature may then be taken as indicative of that of the interior. 

Impedance and Copper-IoM Test. 

method 1. — In this method, which was first described by Dr. Sumpner, 
the secondary coil is short-circuited through an ammeter. A wattmeter 
and a voltmeter are connected up in the primary circuit in a manner similar 
to either of the two methods described for the core-loss test. An adjustable 
resistance or other means for varying the impressed voltage is placed in 
series with the primary circuit. 

To make the test, the voltage is raised gradually until the ammeter shows 
that normal full-load current is flowing through the secondary circuit. 
Readings are then taken on the wattmeter and voltmeter. 

This method of measuring the impedance and copper loss of a transformer 
is now seldom used, on account of the liability to error due to the insertion 
of the ammeter in the secondary. In addition to being inaccurate, it usu- 
ally requires an ammeter capable of measuring a very heavy current. 

IfEetliod 2. — This method differs from Method 1 only in that the sec- 
ondary is short-circuited directly on itself, an ammeter being inserted in the 
primary circuit. The diagram of connections is shown in Fig. 91. In con- 
necting up the voltmeter and the potential coil of the wattmeter, the same 
corrections hold as in the measurement of core loss and exciting current, 
and connections made according to whether accuracy of results or simplicity 
of test is the more imporant. 




"I p| vwwv 



H^) 




WATTMETER 



Fig. 91. Impedance Test with Wattmeter. 
Having the readings of amperes, volts, and watts, we obtain from the 
first two the impedance of the transformer. This impedance is the geo- 
metrical sum of the resistance and reactance, and is expressed algebraically 
as follows : 

z = V IP + (2wnL)*> 
where z = Impedance, 
i?= Resistance, 

L = Coefficient of self-induction, 
/= Current in amperes, 
n = Frequency in cycles per second, 
2?r n L = reactance of the circuit. 

In a test on a transformer with secondary short-circuited as in Fig. 91 
above, and primary connected to 2000 volts, the impedance volts were 97 at 
full-load primary current of 2.5 amperes, then 

97 
Impedance = — = 38.8 ohms, 

and 

97 X 100* 
Impedance drop = = 4.85 per cent. 

The reading on the wattmeter indicates the combined T 2 R of the primary 
and secondary coils, and in addition includes a very small core loss, which 
can be neglected, and an eddy current loss in the conductors. 

In standard lighting transformers, the impedance voltage varies from 
2 per cent to 8 per cent. In making this test, careful record of the fre- 
quency should be made, as the impedance voltage will vary very nearly 
with the frequency. 



488 



THE STATIC TRANSFORMER. 



nMM/V 1 Ua/VW-' ^VWvV 




"-mam, 



A/S rAAAAAA- | rAM/W^i 



SECONDARY 
TRANSFORMER NO. 1 
PRIMARY 



TO THREE-PHASE 
ALTERNATOR B 



PRIMARY 
TRANSFORMER NO. 2 



C 



p/VWW- 



single-pha8e 

alternator 

Fig. 92. 



PRIMARY L > /^^ r l-VV\/VVV-' WVW\A/-' 
SECONDARY r V\/W"| r J WVWS f MWA 1 






rAAAMAi 



^ Law-T 



L^yvJ Uaaa-J 



i|ii lift lift ^^^p^p^ 



TO THREE-PHASE ALTERNATOR B 



TO THREE-PHASE 
" ALTERNATOR A 



Fig. 93. 



Figures 92 and 93 show a method of loading three-phase transformer* 
for heat test. 



TRANSFORMER TESTING. 



489 



Heat Vests. 

To test the transformer for its temperature rise, it is necessary to run it 
at full excitation and full-load current for a certain length of time. An 
eight-hour run at full load will usually raise the temperature to its highest 
point, and in the case of lighting transformers a full-load run very seldom 
continues longer than eight hours in practice. If it is desired to find just 
what is the final temperature rise under full load (as is often the case with 
transformers for power work) the transformer can be operated for two or 
three hours at an overload of about 25 %, after which the load should be 
reduced to normal, and the run continued as long as may be necessary. 

There are several methods for making heat runs of transformers, and all 
of them approximate the condition of the transformer in actual service. 

Heat Test, Uletliod 1. — The primary is connected to a circuit of 
the proper voltage and frequency, and the secondary loaded with lamps or 
resistance until full-load current is obtained. The temperature of all acces- 
sible parts should be obtained by thermometer, and the temperature rise 
of the coils determined by increase of resistance. Frequent readings should 
be taken during the run to see to what extent the transformer is heating. 

Heat Test, Tlethod 3. — Where the transformer is of large size, or 
sufficient load is not obtainable, the motor generator method of heat test is 
preferable. Two transformers of the same voltage, capacity and frequency 
are required, and are connected up as shown in Fig. 94. 





AMMETER 

-O-i 



A 



SWITCH 



TO 
CIRCUIT 



THIS VOLTAGE TO BE APPROX. TWICE THE 
IMPEDANCE VOLTAGE OF EACH TRANSFORMER, 
IT MUST BE ADJUSTED UNTIL FULL LOAD 
CURRENT .FLOWS IN. TRANSFORMERS. 

Fig. 94. 



NOTE: 

THI8 VOLTAGE TO BE THAT OF THE 
SECONDARY OF EACH 
TRANSFORMER 



The two secondaries are connected in parallel, and excited from circuit 
A at the proper voltage and frequency. The two primaries are connected 
in series in such a way as to oppose each other. 

The resultant voltage at B will be zero, however, because the voltage of 
the two primaries is equal and opposite. Any voltage impressed at B will 
thus cause a current to flow independent of the exciting voltages at the 
transformer terminals, and approximately twice the impedance voltage of 
one transformer will cause full-load current to flow through the primaries 
and secondaries of both transformers. 

The total energy thus required to run two transformers at full load is 
merely the losses in the iron and copper. Circuit A supplies the exciting 
current and core losses, and circuit B the full-load current and copper 



Heat Test, Ifletliod 3. —When only one transformer is to be tested, 
and this transformer is of large capacity, a modification of the motor gen- 
erator method can be used as described below : 

This method was first used in testing an 830 k.w. 25-cycle transformer made 
for the Carborundum Company of Niagara Falls. The connections are 
shown in Fig. 95. 

Both primary and secondary windings are divided into two parts, the pri- 
mary coils x and y being connected in multiple to the dynamo circuit, but 
an auxiliary transformer capable of adding a few per cent E.M.F. to that 
half of the primary is connected as shown in the y half. 



490 



THE STATIC TRANSFORMER. 



By this means the primary coils are properly magnetized, and full-load 
currents can be passed through them by varying the auxiliary E.M.F. 

The two halves of the secondary coils are connected in series in opposi- 
tion to each other, and are subject to an auxiliary E.M.F. from the same 
generator, but reduced to the proper voltage by the auxiliary trans- 
former B. 

The currents were measured in all three transformer circuits, and the 
E.M.F. of one-half the secondary was measured. 

The method is accurate enough for large units, and is quite handy where 
no large dynamo can be gotten for supplying full-load currents, as in this 
case current is required only for the transformer losses and for supplying 
the auxiliary transformers. 



1 DYNAMO 






y 


X 




b 




a 

.OCOOQ 




i 




II! 










I 




! 




onrai 


Wfr 




oooo.ou 






PRIMARY 


in 










, 1 




SECONDARY 













Fig. 95. 



General Electric Method of Testing One 
Large Transformer. 



Fig. 96 shows connections for heat-run on three single-phase trans- 
formers, or one three-phase transformer. The primaries and secondaries 
are connected in delta, and in one corner of the primary impedance vol- 




TO ALTERNATOR 

SUPPLYING COPPER 

LOSSES 



TO THREE-PHASE 
ALTERNATOR SUPPLYING 
CORE LOSS 



Fig. 96. 



tage for the three transformers connected in series is impressed. The 
current circulates in the delta connections and is entirely independent of the 
secondary voltage. The method outlined above requires only power enough 
to supply the losses. 



TRANSFORMER TESTING. 



491 



Temperature Rise. 

To ascertain the temperature rise of the different parts of a transformer, 
thermometers are placed on the various parts, and readings taken at fre- 
quent intervals. These readings, however, indicate only. the surface tem- 
perature oi a body and not the actual internal temperature. 

The average rise of temperature of the windings can be more accurately 
determined by means of the increase of resistance of the conductor, and 
is determined by knowing the resistances hot and cold. 
Let Re =r resistance of one coil, cold. 

Rh — resistance of one coil, hot. 
Tc =. temperature of one coil in cent, degrees, cold. 
Th = temperature of one coil in cent, degrees, hot. 
K=z temperature of coefficient of copper .004. 
_ i?ft(l + .0047 T c ) — Re 
h — .OOiRc 

This equation is based on the assumption that the resistance of pure cop- 
per increases .4 % of its value at zero for every degree centigrade rise in 
temperature. 

If it be desired to know the temperature rise of both primary and second- 
ary coils, their hot and cold resistances must be determined separately ; but 
it is customary to determine the temperature rise by resistance of only one 
coil, usually the primary, and comparing the secondary temperatures by the 
thermometer measurements. The method for taking these measurements 
is described in the paragraph in this section on measurement of resistance. 

Ratio. 

As a check against possible mistakes in winding the coils and connecting 
up. a test should be made for ratio of voltages. 

The ratio test is made at a fractional part of the full voltage at no-load 
current, and should not be substituted for a regulation test. An error of one 
or two per cent is quite admissible in making this test, because of its being 
taken at partial voltages. 

Reg- ulation. 

The regulation of a transformer can be determined either by direct meas- 
urement or by calculation from the measurements of resistance and reac- 
tance in the transformer. Since the regulation of any commercial trans- 
former is at the most but a few per cent of the impressed voltage, and as 
errors of observation are very liable to be fully one per cent, the direct 
method of measuring regulation is not at all reliable. 

Regulation by Direct measurements. 

Connect up the transformer with a fully loaded secondary, as in Fig. 97. 
If the primary voltage is very steady, voltmeter No. 2 only will be neces- 
sary, but it is better to use one on the primary circuit also as shown. A 



w.tt 


WM. 3 

2 5 

o 


*M* 


LAMP LOAD 




Fig. 97. Test for Regulation of Transformer. 

reading of voltmeter No. 2 is taken with no load, and again with load, the 

difference in the two readings being the drop in voltage on the secondary. 

We, therefore, have, 

~ T:> . ,. ,__ /100 X Reading at full load"* 

% Regulation = 100 — ( =: r . ~ : > 

\ Reading at no loaa / 



492 



THE STATIC TRANSFORMER. 



Reg-iilation Uy Calculation. 

Several methods of calculating the regulation of transformers from the 
measurements of resistance and reactive drop have been devised. 

Below is a method of Mr. A. R. Everest, which has been found to answer 
the requirements of daily use. 

Let 1R = Total resistance drop in transformer expressed as per cent of 
rated voltage. 
IX = Reactive drop, similarly expressed. 
P = Proportion of energy current in load or power factor of load. For 

non-inductive load P = 1. 
W = Wattless factor of primary current. 

(With non-inductive load, W = Magnetizing current expressed as 
a fraction of full-load current. With inductive load, W = Watt- 
less component of load, plus magnetizing current.) 
Then if volts at secondary terminals = 100%, 
Primary voltage — 
For Hon-Inductive Load: 



E = V(ioo + PIR + fT/X) a + (ZX) 2 . 
Cor Inductive Load : 

E = V (100 + PIR + WIXy + (PIX - WIR) 2 . 

In each of these equations the last expression within parentheses repre- 
sents the drop " in quadrature." 

™ . . i/7^ 3 T^ /Core loss\2 
The magnetizing current = y (Exciting current J — ( - J . 

For frequencies of 60 cycles or higher, magnetizing current may be taken 
as 75 per cent of the exciting current. 

Extracting the square root in the expression for regulation may be 
avoided in the use of the following table : 



Quadrature Drop. 


Increase in Primary Voltage. 


2.5 per 

3 

3.5 " 


cent. 


.025 

.04 

.06 


per 
ii 


cent. 


4 

4.5 " 


" 


.08 
.10 


ti 
it 


ii 

ii 


5 

5.5 " 




.13 
.15 




ft 


6 

6.5 " 


« 


.18 
.21 


ii 


u 
ii 


7 

7.5 « 




.24 
.27 


it 
ii 


II 

ii 


8 

8.5 •« 


11 


.31 
.35 


14 


il 
II 


9 

9.5 " 


<< 
it 


.39 
.45 


ii 


II 

ii 


10 


" 


.50 


ii 


" 



EFFICIENCY. 493 

As an example, take a 2 k.w. transformer having the following losses: 

IR drop = 2%. 
IX drop = 3.5%. 

Exciting current = 4% or .04 ; then magnetizing current = 75% of this, 
or .03. 

1. 3f on- Inductive Load. — Secoudary voltage = 100%. 
Primary voltage in phase = 100 + 2% + (.03 X 3.5%) = 102.1%. 
Quadrature drop = 3.5% ; this from table adds .06% of total primary volt- 
age - 102.16%. 

2 16 
The drop is 2.16% of secondary voltage, or ' = 2.11% of primary volt- 

102.1o 
age, which is the true regulation drop. 

2. Inductive Load. — With a power factor of .86, wattless factor of 
load = .5, and adding magnetizing current (which in most cases might be 
neglected on inductive load), W becomes .52. 

The primary voltage in phase is now 100% -f- (2% X .86) + (3.5 X .52) 
= 103.54%. 
The quadrature drop is (.86X3.5%) -(.52X2%) = 1.97. 
From the table 1.97% adds .02% to primary voltage or 

103.54 + .02%= 103.56. 
Primary voltage = 103.56 

3.56 
Regulation drop = ' = 3.43% of primary voltage. Regulation drop 

should always be expressed finally in terms of primary voltage. 

The above-described methods of traasformer testing are in use by one of 
the large manufacturers, and present average American shop practice. 

The following matter is largely from the important paper by Mr. Ford 
and presents the commonest theoretical test methods. 

EFFICIENCY. 

The efficiency of a transformer is the ratio of its net power output to its 
gross power input, the output being measured with non-inductive load. 
The power input includes the output together with the losses which are as 
follows : 

(1) The core loss, which is determined by test at the rated frequency and 
voltage. 

(2) The P R loss of the primary and the secondary calculated from their 
resistances. 

Example. 
Transformer, Type H, 60 Cycles, 5 k.w., 1000-2000 Volts Prim., 100-200 
Volts Sec. 

Amperes. 

Primary, at 2000 volts 2.5 

Secondary, at 200 volts . 25 

Resistance. Ohms at 20° C. 

Primary 10.1 

Secondary 0.067 

At Full Load. 

Losses. Watts. 

Primary PR 63 

Secondary I 2 R 42 

Total PR 105 

Core Loss 70 

Total Loss 175 

Output at Full Load 5000 

Input " " " 5175 

Efficiency 5000/5175 or 96.6% 



494 THE STATIC TRANSFORMER. 

At Half Load. 

Losses. Watts. 

Total PR 26 

Core Loss 70 

Total Loss 96 

Output 2500 

Input 2596 

Efficiency 2500/2596 or 96.2% 

The all-day efficiency of a transformer is the ratio of the output to the 
input during 24 hours. The usual conditions of practice will be met if the 
calculation is based on 5 hours at full load, and 19 hours at no load. 
Output. Watt Hrs. 

5 Hours at Full Load 25000 

19 Hours at No Load 

Total, 24 Hours 25000 

Input. 

5 Hours at Full Load 25875 

19 Hours at No Load (Neglecting PR Loss due 

to Excitation Current) 1330 

Total, 24 Hours 27205 

All-day Efficiency 25000/27205 or 91.9% 

In calculating the efficiencies in both of the above examples, the copper 
loss due to excitation current of the transformer has been neglected. This 
current, in the example given above, is less than 3%, and its effect on the 
loss of the transformer is thus negligible. Even at no load the total P R 
loss introduced by it is less than one watt. It is quite necessary, however, 
that the loss introduced by the excitation current should be checked in all 
cases. In some transformers, for example, the excitation current may 
reach 30 % of the full-load current, and thus its effect is noticeable at large 
loads, while at \ load the loss in the primary winding due to excitation 
current is greater than the loss due to the load current. 

Inasmuch as the losses in the transformer are affected by the tempera- 
ture and the wave form of the E.M.F., the efficiency can be accurately 
specified only by reference to some definite temperature, such as 25° C, and 
by stating whether the E.M.F. is sine or otherwise. 

The foregoing method of calculating the efficiency neglects what are 
known as " load losses," i.e., the eddy current losses in the iron and the 
conductors caused by the current in the transformer windings. The watts 
measured in the impedance test include " load losses " and I 2 R losses to- 
gether with a small core loss. Considering the core loss as negligible, the 
" load losses " are obtained by subtracting from the measured watts the PR 
loss calculated from the resistance of the transformer. It is sometimes 
assumed that the " load losses" in a transformer when it is working under 
full-load conditions are the same as those obtained with short-circuited 
secondary, and it is stated that these losses should enter into the calcula- 
tion of efficiency. Many tests have been made to determine whether or not 
the above assumption is correct, and while the results cannot be considered 
as conclusive, they indicate in every case that, under full-load conditions, 
the "load losses" are considerably less than those measured with short- 
circuited secondary. Inasmuch as these losses, in general, form a small 
percentage of the total loss in a transformer, and in view of the difficulty 
in determining them with accuracy, they may be neglected in the calcula- 
tion of efficiency for commercial purposes. The measurement of watts in 
the impedance test is, however, useful as a check on excessive eddy current 
losses in a poorly designed transformer. 




DATA TO BE DETERMINED BY TESTS 495 



JPOJLAMTY. 

For lighting and other small uses, transformers are generally designed so 
that the instantaneous direction of flow of the current in certain selected 
leads is the same in all transformers of the same type. For example, re« 
ferring to Fig. 98, the transformer there shown is de- 
signed so that the current at any instant flows into the 
primary at " A " and into the secondary at " C." This 
is the system adopted for small transformers by the ma- 
jority of manufacturers. 

The polarity test should be unnecessary when bank- 
ing transformers of the same type and design. When, 
however, transformers manufactured by different com- 
panies are to be run in parallel, it is necessary to test 
them in order to avoid the possibility of connecting 
them in such a way as to short circuit the one on the 
other. Their polarity may be determined by one of 
the following methods: 

In Fig. 98, Primary lead " A " is of opposite polarity 
to the Secondary lead " C." Connect the primary lead 
" A " to the Secondary lead " C." Apply one hundred 
volts, say to the primary " A-B " of the transformer. 
The voltage measured from " A " to " D " will be 

greater than the applied voltage. In other words, a transformer connected 
as shown will act as a booster to the voltage. If the leads " A " and *' B " 
are of the same polarity, voltage measured from " A " to " D " will be less 
than that applied at " A-B." 

If a standard transformer known to have correct polarity and the same 
ratio as the test transformer is available, the simplest method for testing the 
polarity is to connect the primaries and secondaries of the transformers in 
parallel, placing a fuse in series with the secondaries. On applying voltage 
to the primaries of the transformers if they are of the same polarity and ratio 
no current should flow in the secondary circuit and the fuse will remain intact. 
If the transformers are of opposite polarity the connection will short circuit 
the one transformer on the other, and the fuse selected should therefore be 
small enough to blow before the transformers are injured. In nearly all 
transformers there will be a slight current in the secondaries when connected 
as above. This current is known as the " exchange current " and should 
be less than 1 per cent of the normal full load current of the transformer. 

Transformers of large capacity and higher voltage for central station work 
usually have a polarity opposite that shown in Fig. 98. There is, however, 
no standard for these transformers. 

DATA TO BE I>ETJEI*:WLi:VE» I** TJESTS. 

Partly from a paper by Arthur Hillyer Ford- B. S. 
I. Copper loss-, to determine the efficiency. 

II. Iron-core loss, hot and cold, to determine the efficiency : to separate 

the hysteresis from the foucault current loss. 
If JF:= watts output, 

/= watts iron-core loss, 
C= watts copper loss, 
. then the 

Efficiency = 100 - ( y+ ^ +c X 100 ) 

Foucault currents loss should decrease with an increase in tempera- 
ture. 
Hysteresis loss is supposed to be constant regardless of heat. 

III. Open circuit or exciting current. 

IV. Regulation, to determine the magnetic leakage. 

V. Rise in temperature in case and out of case, for no load and full 

load ; with and without oil. 
VI. Insulation. 



496 



THE STATIC TRANSFORMER. 



Methods. 

Opposition Method of Avrton and Sumpner. — This method 
is especially valuable where the transformers to be tested are of large ca- 
pacity, and a source of power great enough to put them under full load in 
the ordinary way is unavailable. A supply of current of an amount some- 
what greater than the total losses of both transformers is all that is neces- 
sary. Following is a diagram of the connections, by which it will be seen 
that the transformers are so connected that one feeds the other, or they 
work in opposition. 



Fig. 




SMALL 
TRANSFORMER 



Diagrams of Connections for Ayrton and Sumpner 
Opposition Method of Testing Transformers. 



In making the test, current is turned on and the resistance R adjusted until 
full-load current flows in the secondary, as shown by the ammeter A, and the 
primary current and voltage in A and V is up tojstandard. Then the watts 
read on W are equal to all the losses in both transformers, and W r ! the losses in 
the copper of the transformers plus the copper loss in the leads and in the cur- 
rent coils of Wi and A. 

The iron loss in both transformers is = W— Wi — A, where A is the loss in 
the leads and instruments which may be calculated by PR. 

Method of I>r. Sumpner. Iron liOss. — The following diagram 
shows the connections for Dr. Sumpner's test for iron losses. The low- 




\Tl . AOJUSTABL 

J^VJ I RESISTANC 

s 1 » R. T 






fi 

I 



Fig. 100. Dr. Sumpner's Test for Iron Losses 



DATA TO BE DETERMINED BY TESTS. 



497 



pressure side is connected to a source of current of the same pressure at 
which the transformer is expected to work, thus producing the same pri- 
mary voltage in the high-pressure side at which it is expected to work. 
With the primary circuit open, the iron losses in the transformer are read 
directly in watts on the wattmeter. 

Copper Lois. — The next diagram shows the connections for determin- 
ing the copper losses. The low-pressure side is short-circuited through an 
ammeter, the high-pressure side being connected to the 100-volt supply- 
mains. The resistance R is then adjusted to obtain full-load or any other 
desired current in the secondary, as shown by the ammeter. The reading 
of the wattmeter will then show the total copper losses in the transformer 
and in the ammeter plus a very small and entirely negligible iron loss. The 
ammeter losses and that in the leads may be calculated by 1 2 R. The small 
iron loss can be separated or determined by disconnecting the ammeter and 




(Enr 



Fig. 101. Dr. Sumpner's Test for Copper Losses. 



adjusting R, until the pressure on the primary is the same as in the copper 
loss test; the wattmeter will then show the small iron loss. 

The iron loss is proportional to (ft 1 * 6 and (ft the magnetic density is pro^ 
portional to the pressure at the terminals of the transformer, therefore the 
iron loss is equal to JjT.tft 1 - 8 where K is a constant and (ft the voltage. In the 
iron-loss test the (ft = 1000 and in the copper loss test 



(ft = 100. 



K X 10001- 6 = 63,000 K 
JTX100 1 - 6 = 1,600 K = 



2.5% of total iron loss. 



Heating 1 . — Tests should be made at no load, at full load, and at inter- 
mediate loads for rise of temperature of the transformers out of their cases, 
in their cases, without oil and with oil, if full data is wanted. If a strictly 
commercial test is all that is necessary, a test with the transformer at full 
load and set up in the condition it is to be run, will be sufficient. 

Surface temperatures can be taken by thermometers laid on and covered 
with cotton waste. In oil-insulated transformers, the temperature of the 
oil should be taken in two places, — inside the coil, and between the coil 
and case. 

Leakage Drop. — The drop in the secondary due to magnetic leakage 
can be found by deducting from the measured total drop in the PR drop due 
to the resistance of the coil. 



498 



THE STATIC TRANSFORMER. 



SPECIFIC AIIOI i* 1 Oil TRAiyiFORMERS. 

It is almost impossible to enumerate the features to be included in speci- 
fications covering transformers, because of the wide range of operation and 
service to which they may be put, necessitating different characteristics 
for the transformers intended for different kinds of services. 

For transformers operating from a fairly expensive source of supply, the 
leading manufacturers have decided on characteristics which, in general, 
will be covered in the following tabulation. 

This gives average characteristics of transformers designed for operation 
on 60-cycle circuits, and the figures given are based on operation of 2000 
volts and sine wave alternator. 



Capacity. 


Core Loss 
Watts. 


Copper Loss 
Watts. 


Exciting Cur- 
rent^,. 


Regulation % 


1 


35 


30 


9.0 


2.8 


2 


45 


50 


7.0 


2.5 


3 


55 


70 


3.0 


2.3 


5 


70 


105 


2.5 


2.2 


7.5 


100 


150 


2.3 


2.2 


10 


120 


180 


2.3 


2.0 


15 


155 


275 


2.2 


1.8 


20 


185 


300 


1.5 


1.7 


30 


235 


475 


1.2 


1.5 


50 


335 


675 


1.0 


1.3 



AGEOG, 

Guarantees against serious ageing of iron should cover a period of at least 
one year. 

RISE OF TEHPERAT1JRE. 

The rise of temperature should be referred to the standard conditions 
of a room-temperature of 25° C, a barometric pressure of 760 mm. and 
normal conditions of ventilation; that is, the apparatus under test should 
neither be exposed to draught nor inclosed, except where expressly specified. 

If the room temperature during the test differs from 25° C. the observed 
rise of temperature should be corrected by i per cent for each C. Thus 
with a room temperature of 35° C. the observed rise of temperature has 
to be decreased by 5 per cent, and with a room temperature of 15° C. the 
observed rise of temperature must be increased by 5 per cent. The ther- 
mometer indicating the room temperature should be screened from thermal 
radiation emitted by heated bodies, or from draughts of air. When it is 
impracticable to secure normal conditions of ventilation on account of 
adjacent engine or other sources of heat, the thermometer for measuring 
the air temperature should be placed so as fairly to indicate the tempera- 
ture which the machine would have if it were idle, in order that the rise 
of temperature determined shall be that caused by the operation of the 
machine. 

The temperature should be measured after a run of sufficient duration to 
reach practical constancy. This is usually from six to eighteen hours 
according to the size and construction of the apparatus. It is permissible, 
however, to shorten the time of the test by running a lesser time on an 
overload in current and voltage, then reducing the load to normal, and 
maintaining it thus until the temperature has become constant. 

In electrical conductors, the rise of temperature should be determined 



LOCATION OF TRANSFORMERS. 499 

by the increase of their resistance where practicable. For this purpose 
the resistance may be measured either by galvanometer test, or by drop 
of potential method. A temperature coefficient of 0.42 per cent per degree 
C. from and at 0° C. may be assumed for copper, by the formula: 

Rt = R (1 + 0.0042 and Rt + = R [1 - 0.0042 (* + 0)] 
where Rt = the initial resistance at room temperature t° C. 
Tt + = the final resistance at temperature elevation 0°- C. 
Ro = the inferred resistance at 0° C. 

These combine into the formula: 

'Tt + - 1> 



0= (238.1+0 ( T ' + n 1 )°C- 



For insulation test see report of Committee on Standardization of 
A. I. E. E., page 514. 



LOCATION OF TRA^§rORHERS. 

1. Where practicable, the transformers should be placed in a boiler 
iron case, capable of withstanding an internal pressure of 50 lbs. per 
square inch, the case to be suitably vented. 

2. Where a sheet iron construction is necessary, the case should be 
made practically air tight and provided with a very large safety valve, 
so that an internal explosion cannot burst the case. 

3. Provision should be made for rapidly drawing off the oil in case it 
becomes necessary to do so. 

4. Individual transformer units, or groups of units, should be located 
in fireproof compartments, such compartments to be suitably drained so 
that in case the oil escapes from the cases, it can flow out where it can do 
no harm. 

5. Adequate means should be provided for extinguishing fire, and the 
station attendants should be trained to know what to do in case of emer- 
gency. 

An oil should be selected which has a flash point not lower than, say, 
175° C. Such an oil, if properly made, will have practically no evapora- 
tion whatever at 100° C, this temperature being higher than will be found 
except under the most extreme conditions of temporary overload. 

Too high a flash test oil is undesirable on account of the viscosity being 
so great that the power to carry heat from the transformer to the cooler 
case is greatly reduced, and on account of it being very unpleasant to 
handle. 

Where rubber-covered leads are used, the rubber should be heavy (not 
less than \" wall per 10,000 volts) and of high quality, and a fireproof 
covering should be used. Extra flexible cable is usually preferable. Rub- 
ber may be tested for dielectric strength, insulation resistance, etc., but its 
qualification for important uses is best judged by its mechanical proper- 
ties. To examine these, remove the braid from the wire for several inches, 
but without cutting the rubber except at the ends of the space. Here it 
should be cut (at both ends) down to the wire. It will be found in many 
makes that there are two joints in the rubber running parallel to the wire. 
A longitudinal cut along the wire, and down to it, should be made midway 
between the joints. This will make it possible to easily remove the rubber 
from the wire. First, test each of the joints by bending them over back- 
wards. The best joints will show some tendency to open, and for this 
reason a double layer of rubber, with joints staggered, is desirable. In 
many (so called) first class wires it will be found that the joints are just 
slightly stuck together, or break open on the slightest provocation. Such 
insulation is worthless. The quality of the rubber may be judged by cut- 
ting long strips, about \" wide, or less, and bending it double and as short 
as possible. It should show no signs of cracking. Pure rubber is very 
elastic and strong, and it loses these properties in proportion as it is adul- 
terated. 



500 THE STATIC TRANSFORMER. 

6PECIFICATIO]V§ FOR THAPI ORMER Oil* 

(C. E. Skinner.) 

In the following will be found a brief specification for a transformer oil. 

(1) The oil should be a pure mineral oil obtained by fractional distil- 
lation of petroleum unmixed with any other substances and without sub- 
sequent chemical treatment. 

(2) The flash test of the oil should not be less than 180° C. (356° F.), 
and the burning test should not be less than 200° C. (392° F.). 

(3) The oil must not contain moisture, acid, alkali, or sulphur com- 
pounds. 

(4) The oil should not show an evaporation of more than 0.2% when 
heated at 100° C. for eight hours. 

(5) It is desirable that the oil be as fluid as possible and that the color 
be as light as can be obtained in an untreated oil. 

The method of making tests to determine the above qualities should be 
distinctly specified so that there can be no misunderstanding on account 
of results being obtained by different methods of test. 

The specification for flash test given above is intended to be low enough 
so that there will be some leeway to allow for slight variations in the oil 
and for variations obtained by different observers. It is expected that an 
oil to fulfill this specification will run something higher than 180° flash test. 



STANDARDIZATION RULES OP THE AMERI- 
CAN INSTITUTE OP ELECTRICAL 
ENGINEERS. 

(Approved by the Board of Directors, June 27, 1911,) 
OEA'ERAL PL4\. 

I. Definitions and Technical Data. 

A. Definitions — Currents and E.M.F.'s. 

B. Definitions — Rotating Machines. 

C. Definitions — Stationary Induction Apparatus. 

D. General Classification of Apparatus. 

E. Motors — Speed Classification. 

F. Definitions — Instruments. 

G. Definition and Explanation of Terms. 

(I) Load Factor, Diversity Factor, Demand Factor. 

(II) Non-inductive and Inductive Load. 

(III) Power Factor and Reactive Factor. 

(IV) Saturation Factor. 

(V) Variation and Pulsation. 

II. Performance Specifications and Tests. 

A. Rating. 

B. Wave Shape. 

C. Efficiency. 

(I) Definitions. 

(II) Measurement of Efficiency. 

(III) Measurement of Losses. 

(IV) Efficiency of Different Types of Apparatus. 

(a) Direct -Current Commutating Machines. 

(b) Alternating-Current Commutating Machines. 

(c) Synchronous Commutating Machines. 
(<2) Synchronous Machines. 

(e) Stationary Induction Apparatus. 

(/) Rotary Induction Apparatus. 

(g) Unipolar or Acyclic Machines. 

(h) Rectifying Apparatus. 

(i) Transmission Lines. 

0") Phase-Displacing Apparatus. 

D. Regulation. 

(I) Definitions. 

(II) Conditions for and Tests of Regulation. 

E. Insulation. 

(I) Insulation Resistance. 

(II) Dielectric Strength. 

(a) Test Voltages. 

(b) Methods of Testing. 

(c) Methods for Measuring the Test Voltage. 

(d) Apparatus for Supplying Test Voltage. 

F. Conductivity. 

G. Rise of Temperature. 

(I) Measurement of Temperature. 

(a) Methods. 

(b) Normal Conditions for Tests. 

500a 



500b standardization rules. 



(II) Limiting Temperature Rise. 

(a) Machines in General. 

(b) Rotary Induction Apparatus. 

(c) Stationary Induction Apparatus. 

(d) Rheostats. 

(e) Limits Recommended in Special Gases. 
H. Overload Capacities. 

III. Voltages and Frequencies. 

A. Voltages. 

B. Frequencies. 

IV. General Recommendations. 

V. Appendices and Tabular Data. 
Appendix A. — Notation. 
Appendix B. — Railway Motors. 

(I) Rating. 

(II) Selection of Motor for Specified Service. 
Appendix C. — Photometry and Lamps. 
Appendix D. — Sparking Distances. _ 
Appendix E. — Temperature Coefficients. 
Appendix F. — Horse Power. 



STANDARDIZATION RULES OP THE AMERI- 
CAN INSTITUTE OP ELECTRICAL 
ENGINEERS. 

(As Approved June 27, 1911.) 
I. OJEJFiA aXIOVS AUD TECHNICAL DATA. 

1. Note. The following definitions and classifications are intended to be 
practically descriptive and not scientifically rigid. 

A. DEFINITIONS. CURRENTS AND E.M.F.'S. 

2. A Direct Current is an unidirectional current. 

3. A Continuous Current is a steady, or non-pulsating, direct current. 

4. A Pulsating Current is a current equivalent to the superposition of an 
alternating current upon a continuous current. 

5. An Alternating Current or E.M.F. is a current or E.M.F. which, when 
plotted against time in rectangular coordinates, consists of half-waves of equal 
area in successively opposite directions from the zero line. 

5a. Cycle. Two immediately succeeding half-waves constitute a cycle. 

5b. Period. The time required for the execution of a cycle is called a period. 

5c. Frequency. The number of cycles per second is called the frequency. 

5d. Wave-Form. The shape of the curve of E.M.F. or current plotted 
against time in rectangular coordinates is ordinarily referred to as the wave- 
form or wave-shape. Two alternating quantities are said to have the same 
wave-shape if their corresponding phase ordinates bear a constant ratio. The 
wave-shape, as ordinarily understood, is thus independent of the scales to 
which the curve is plotted. 

be. Simple Alternating Wave. Unless otherwise specified an alternating 
current or E.M.F. is assumed to be sinusoidal, and the wave a sinusoid, sine- 
wave or curve of sines. On this account a complete cycle is taken as 360 
degrees, and any portion of a cycle may be expressed in degrees from any 
convenient reference point, such as the ascending zero-point. 

5/. A Complex Alternating Wave is a non-sinusoidal wave. A complex 
alternating wave is capable of being resolved into a single sine wave of funda- 
mental frequency, with superposed odd-frequency harmonic waves, or ripples, 
of 3, 5, 7 ... (2 n + 1) times the fundamental frequency, each harmonic 
having constant amplitude, and a definite starting phase-relation to the fun- 
damental sine-wave. It is customary when analyzing a complex wave to 
neglect harmonics higher than the 11th: i.e., of frequency higher than 11 time3 
the fundamental. In special cases, however, frequencies still higher may have 
to be considered. In certain exceptional cases even harmonics are present. 

bg. Root-Mean-Square Value (sometimes called the Virtual or Effective 
Value). Unless otherwise specified, the rating of an alternating-current or 
E.M.F., in amperes or volts, is assumed to be the square root of the mean 
square value taken throughout one or more complete cycles. This is some- 
times abbreviated to r.m.s. The term root-mean-square is to be preferred to 
the terms virtual or effective. The root-mean-square value is indicated by 
all properly calibrated alternating-current voltmeters and ammeters. In the 
case of a sine-wave, the ratio of the maximum to the r.m.s. value is v2. 

bh. Form-Factor of an Alternating Wave. The ratio of the root-mean- 
square to the arithmetical mean ordinate of a wave, taken without regard to 
sign, is called its form-factor. The form-factor for a purely rectangular wave 
is the minimum, 1.0; for a sine-wave it is 1.11, and for a wave more peaked 
than a sine-wave it is greater than 1.11. 

bi. The Equivalent Sine-Wave is a sine-wave having the same frequency 
and the same r.m.s. value as the actual wave. 

bj. The Deviation of wave-form from the sinusoidal is determined by^ super- 
posing upon the actual wave (as determined by oscillograph), the equivalent 
sine-wave of equal length, in such a manner as to give the least difference, and 
then dividing the maximum difference between corresponding ordinates by 
the maximum value or the equivalent sine-wave. 

bk. Phase Difference. When corresponding cyclic values of two sinu- 
soidal alternating quantities such as two alternating currents or E.M.F.'s or 
of a current and an E.M.F., of the same frequency, occur at different instants, 

501 



i 



502 STANDARDIZATION RULES. 

the two alternating quantities are said to differ in phase, their phase difference 
being the time interval, expressed in degrees or as a fraction of a cycle, between 
the occurrence of their corresponding values; e.g., their ascending zeros or 
their positive maxima. 

bl. Equivalent Phase Difference. If two alternating quantities are 
non-sinusoidal, and of different wave shapes, the preceding definition of phase- 
difference is inapplicable, and phase-difference ceases to have exact signifi- 
cance. However, when the two complex alternating quantities are the voltage 
E and current / in a given circuit, the effective power P of which is known, it 
is customary to define the equivalent phase difference by the angle whose 
cosine is the power-factor, P /EI, of the circuit. See Sections 54 and 324. 

bm. Single-Phase. A term characterizing a simple alternating-current 
circuit energized by a single alternating E.M.F. Such a circuit is usually 
supplied through two wires. The currents in these two wires counted posi- 
tively outwards from the source, differ in phase by 180 degrees or half a cycle. 

5m. Three-Phase. A term characterizing the combination of three cir- 
cuits energized by alternating E.M.F.'s which differ in phase by one-third of a 
cycle; i.e., 120°. 

bo. Quarter-Phase, also called Two-Phase. A term characterizing the 
combination of two circuits energized by alternating E.M.F.'s whichldiffer in 
phase by a quarter of a cycle; i.e., 90°. 

bp. Six-Phase. A term characterizing the combination of six circuits ener- 
gized by alternating E.M.F.'s which differ in phase by one-sixth of a cycle; 
i.e., 60°. 

bq. Polyphase is the general term applied to any alternating system with 
more than a single phase. 

6. An Oscillating Current is a current alternating in direction, and of de- 
creasing amplitude. 

B. DEFINITIONS. ROTATING MACHINES. 

7. A Generator transforms mechanical power into electrical power. 

8. A Direct-Current Generator produces a direct current that may or may 
not be continuous. 

9. An Alternator is an alternating-current generator, either single-phase or 
polyphase. 

9a. A Synchronous Alternator comprises a constant magnetic field and an 
armature delivering either single-phase or polyphase current in synchronism 
with the rotation of the machine. 

10. A Polyphase Generator produces currents differing symmetrically in 
phase; such as quarter-phase currents, in which the terminal voltages of the 
two circuits differ in phase by 90 degrees: or three-phase currents, in which 
the terminal voltages of the three circuits differ in phase by 120 degrees. 

11. A Double-Current Generator supplies both direct and alternating 
currents from the same armature winding. 

11a. An Inductor Alternator is an alternator in which both field and arma- 
ture windings are stationary. 

116. An Induction Generator is a machine structurally identical with an 
induction motor, but driven above synchronous speed as an alternating- 
current generator. 

12. A Motor transforms electrical power into mechanical power. 

12a. A Direct-Current Motor transforms direct-current power into me- 
chanical power. 

126. An Alternating-Current Motor transforms alternating-current power 
into mechanical power. 

12c. A Synchronous Motor is a machine structurally identical with a syn- 
chronous alternator, but operated as a motor. 

12d. A Synchronous Phase Modifier, sometimes called a Synchronous Con- 
denser, is a synchronous motor, running either idle or under load, whose field 
excitation may be varied so as to modify the power-factor of the circuit, or 
through such modification to influence the voltage of the circuit. 

12e. An Induction Motor is an alternating-current motor, either single-phase 
or polyphase, comprising independent primary and secondary windings, one 
of which, usually the secondary, is on the rotating member. The secondary 
winding has no conductive connection with the supply circuit. 

12/. A Repulsion Motor is an induction motor, usually single phase, in which 
the magnetic axis of the secondary (a closed coil winding mounted on the 
rotor) is maintained at a certain fixed angle with respect to the stationary 



DEFINITIONS AND TECHNICAL DATA. 503' 

primary coil by means of a multisegmental commutator and short-circuiting 
brushes. 

12a. A Single-Phase Series Commutator Motor is structurally similar to a 
series direct-current motor, except that it is usually provided in addition 
with a series compensating winding distributed around the outer air-gap 
periphery and supported in slots in the pole faces, for the purpose of dimin- 
ishing the armature leakage reactance. 

13. A Booster is a machine inserted in series in a circuit to change its volt- 
age. It may be driven by an electric motor (in which case it is termed a motor- 
booster) or otherwise. 

14. A Motor-Generator is a transforming device consisting of a motor 
mechanically connected to one or more generators. 

15. A Dynamotor is a transforming device combining both motor and gen- 
erator action in one magnetic field, either with two armatures, or with one 
armature having two separate windings and independent commutators. 

16. A Converter is a machine employing mechanical rotation in changing 
electrical energy from one form into another. A converter may belong to 
either of several types, as follows: 

17. a. A Direct-Current Converter converts from a direct current to a 
direct current, usually with a change of voltage. 

18. b. A Synchronous Converter (commonly called a rotary converter) con- 
verts from an alternating to a direct current, or vice versa. 

19. c. A Motor-Converter is a combination of an induction motor with a 
synchronous converter, the secondary of the former feeding the armature of 
the latter with current at some frequency other than the impressed frequency; 
i.e., it is a synchronous converter concatenated with an induction motor. 

20. d. A Frequency Changer converts the power of an alternating-current 
system from one frequency to another, with or without a change in the number 
of phases or in the voltage. 

21. e. A Rotary Phase Converter converts from an alternating-current 
system of one or more phases to an alternating-current system of a different 
number of phases, but of the same frequency. 

21a. Equalizing Connections are low resistance connections between equi- 
potential points of multiple-wound closed-coil armatures to equalize the in- 
duced voltage between brushes. 

C. DEFINITIONS. STATIONARY INDUCTION APPARATUS. 
.22. Stationary Induction Apparatus changes electric energy to electric 
energy through the medium of magnetic energy. It comprises several forms, 
distinguished as follows: 

23. a. Transformers, in which the primary and secondary windings are 
insulated from one another. 

23a. A Primary Winding is that winding of a transformer, or of an induc- 
tion motor, which receives power from an external source. 

236. A Secondary Winding is that winding of a transformer, or of an in- 
duction motor, which receives power from the primary by induction. 

Note. The terms "High-voltage winding" and "Low-voltage winding" 
are suitable for distinguishing between the windings of a transformer, where 
the relations of the apparatus to the source of power are not involved. 

24. b. Auto-Transformers, also called compensators, in which a part of the 
primary winding is used as a secondary winding, or conversely. 

25. c. Potential Regulators, in which one coil is in shunt and one in series 
with the circuit, so arranged that the ratio of transformation between them ia 
variable at will. They are of the following three classes: 

26. (1) Contact Voltage Regulators, also called Compensator Regulators, 
in which the number of turns in use of one of the coils is adjustable. 

27. (2) Induction Potential Regulators in which the relative positions of 
the primary and secondary coils are adjustable. 

28. (3) Magneto Potential Regulators in which the direction of the mag- 
netic flux with respect to the coils is adjustable. 

29. d. Reactors or Reactance Coils, also called choke coils, are a form of 
stationary induction apparatus used to supply reactance or to produce phase 
displacement. 

29a. e. An Induction Starter is a device used in starting induction motors, 
converters, etc., by voltage control, consisting of an auto-transformer com- 
bined with a suitable switching device. 

296. A Leakage Reactance or Series Reactance is a portion of the reactance 
of any induction apparatus which is due to stray or purely self-inductive flux. 



504 STANDARDIZATION RULES. 

D. GENERAL CLASSIFICATION OF APPARATUS. 

30. Commutating Machines. Under this head may be classed the follow- 
ing: Direct-current generators; direct-current motors; direct-current boost- 
ers; motor-generators; dynamotors; converters; compensators or balancers; 
closed-coil arc machines, and alternating-current commutating motors. 

31. Commutating machines may be further classified as follows: 

32. a. Direct-Current Commutating Machines, which comprise a magnetic 
field of constant polarity, a closed-coil armature, and a multisegmental commu- 
tator connected therewith. 

33. b. Alternating-Current Commutating Machines, which comprise a 
magnetic field of alternating polarity, a closed-coil armature, and a multi- 
segmental commutator connected therewith. 

34. c. Synchronous Commutating Machines, which comprise synchronous 
converters, motor-converters and double-current generators. 

35. Synchronous Machines comprise a constant magnetic field and an 
armature receiving or delivering alternating-currents in synchronism with the 
motion of the machine; i.e., having a frequency equal to the product of the 
number of pairs of poles and the speed of the machine in revolutions per second. 

36. Stationary Induction Apparatus include transformers, auto-trans- 
formers, potential regulators, and reactors or reactance coils. 

37. Rotary Induction Apparatus, or Induction Machines, include apparatus 
wherein the primary and secondary windings rotate with respect to each other; 
i.e., induction motors, induction generators, frequency converters, and rotary 
phase converters. 

38. Unipolar or Acyclic Machines, direct-current machines, in which the 
voltage generated in the active conductors maintains the same direction with 
respect to those conductors. 

39. Rectifying Apparatus, Pulsating-Current Generators. 

40. Electrostatic Apparatus, such as condensers, etc. 

41. Electrochemical Apparatus, such as batteries, etc. 

42. Electrothermal Apparatus, such as heaters, etc. 
42a. Regulating Apparatus, such as rheostats, etc. 
426. Switching Apparatus. 

43. Protective Apparatus, such as fuses, circuit-breakers, lightning arresters, 
etc. 

44. Luminous Sources. 

E. MOTORS. SPEED CLASSIFICATION. 

45. Motors may, for convenience, be classified with reference to their speed 
characteristics as follows: 

46. a. Constant-Speed Motors, in which the speed is either constant or 
does not materially vary; such as synchronous motors, induction motors 
with small slip, and ordinary direct-current shunt motors. 

47. b. Multispeed Motors (two-speed, three-speed, etc.), which can be 
operated at any one of several distinct speeds, these speeds being practically 
independent of the load, such as motors with two armature windings, or in- 
duction motors with controllers for changing the number of poles. 

48. c. Adjustable-Speed Motors, in which the speed can be varied gradually 
over a considerable range; but when once adjusted remains practically un- 
affected by the load, such as shunt motors designed for a considerable range of 
field variation. 

49. d. Varying-Speed Motors, or motors in which the speed varies with 
the load, decreasing when the load increases; such as series motors. 

F. DEFINITIONS. INSTRUMENTS. 

49a. An Ammeter is a current-measuring instrument, indicating in amperes. 

496. A Voltmeter is a voltage-measuring instrument, indicating in volts. 

49c. A Wattmeter is an instrument for measuring electrical power, and 
indicating in watts. 

49d. Recording Ammeters, Voltmeters, Wattmeters, etc., are instruments 
which record graphically upon a time-chart the values of the quantities they 
measure. 

49e. A Watt-Hour Meter is an instrument for registering total watt-hours. 
This term is to be preferred to the term "integrating wattmeter." 

49/. A Voltmeter Compensator is a device in connection with a voltmeter, 
which causes the latter to indicate the voltage at some other point of the 
circuit. 



DEFINITIONS AND TECHNICAL DATA. 505 

49fir. A Synchroscope is a synchronizing device which, in addition to indi- 
cating synchronism, shows whether the machine to be synchronized is fast or 
slow. 

G. DEFINITION AND EXPLANATION OF TERMS. 

(I) Load Factor. 

50. The Load Factor of a machine, plant or system is the ratio of the aver- 
age power to the maximum power during a certain period of time. The average 
power is taken over a certain period of time, such as a day or a year, and the 
maximum is taken over a short interval of the maximum load within that 
period. 

51. In each case the interval of maximum load should be definitely specified. 
The proper interval is usually dependent upon local conditions and upon the 
purpose for which the load factor is to be determined. 

(II) Diversity Factor. 

51a. Diversity Factor is the ratio of the sum of the maximum power de- 
mands of the subdivisions of any system or part of a system to the maximum 
demand of the whole system or of the part of the system under consideration, 
measured at the point of supply. 

(III) Demand Factor. 

516. Demand Factor is the ratio of the maximum power demand of any 
system or part of a system to the total connected load of the system or of the 
part of the system under consideration. 

(IV) Non-inductive Load and Inductive Load. 

52. A non-inductive load is a load in which the current is in phase with the 
voltage across the load. 

53. An inductive load is a load in which the current lags behind the voltage 
across the load. A load in which the current leads the voltage across the load 
is sometimes called a condensive or anti-inductive load. 

53a. When voltage and current waves are sinusoidal but not in phase, the 
voltage may be resolved into two components, one in phase with the current 
and the other in quadrature therewith. The former is called the effective 
component (sometimes the energy component), and the latter the reactive 
component of the voltage. The current may be similarly subdivided with 
respect to the voltage, and the two components similarly named. 

(V) Power-Factor and Reactive Factor. 

54. The Power-Factor in alternating-current circuits or apparatus is the 
ratio of the effective {i.e., the cyclic average) power in watts to the apparent 
power in volt-amperes. It may be expressed as follows: 

effective power _ effective watts _ effective current _ effective voltage 
apparent power total volt-amperes total current total voltage * 

55. The Reactive-Factor is the ratio of the reactive volt-amperes (i.e., the 
product of the reactive component of current by voltage, or reactive com- 
ponent of voltage by current) to the total volt-amperes. It may be expressed 
as follows: 

reactive power _ reactive watts _ reactive current _ reactive voltage 
apparent power total volt-amperes total current total voltage * 

56. Power-Factor and Reactive-Factor are related as follows: 

If p = power-factor and q = reactive-factor, then with sine-waves of voltage 
and current, 

p 2 + q} = 1. 

With distorted waves of voltage and current, g ceases to have definite sig- 
nificance. 

(VI) Saturation-Factor. 

57. The Saturation-Factor of a machine is the ratio of a small percentage 
increase in field excitation to the corresponding percentage increase in voltage 
thereby produced. The saturation-factor is, therefore, a criterion of the degree 
of saturation attained in the magnetic circuit at any excitation selected. Un- 
less otherwise specified, however, the saturation-factor of a machine refers to 



506 STANDARDIZATION RULES. 

the excitation existing at normal rated speed and voltage, It is determined 
from measurements of saturation made on open circuit at rated speed. 

58. The Percentage of Saturation of a machine at any excitation may be 
found from its saturation curve of generated voltage as ordinates, against 
excitation as abscissas, by drawing a tangent to the curve at the ordinate cor- 
responding to the assigned excitation, and extending the tangent to intercept the 
axis of ordinates drawn through the origin. The ratio of the intercept on this 
axis to the ordinate at the assigned excitation, when expressed in percentage, 
is the percentage of saturation and is independent of the scale selected for 
excitation and voltage. This ratio is equal to the reciprocal of the saturation- 
factor at the same excitation, deducted from unity. Thus, if / be the satura- 
tion-factor and p the percentage of saturation, 

(VII) Variation and Pulsation. 

59. The Variation in Prime Movers which do not give an absolutely uniform 
rate of rotation or speed, as in reciprocating steam engines, is the maximum 
angular displacement in position of the revolving member expressed in degrees, 
from the position it would occupy with uniform rotation, and with one revo- 
lution taken as 360°. 

60. The Pulsation in Prime Movers is the ratio of the difference between 
the maximum and minimum velocities in an engine-cycle to the average velocity. 

61. The Variation in Alternators or alternating-current circuits in general 
is the maximum difference in phase of the generated voltage wave from a wave 
of absolutely constant frequency of the same average value, expressed in elec- 
trical degrees (one cycle equals 360°) and may be due to the variation of the 
prime mover. 

62. The Pulsation in Alternators or alternating-current circuits, in general, 
is the ratio of the difference between maximum and minimum frequency during 
an engine cycle to the average frequency. 

63. Relation of Variation in prime mover and alternator. If p = number 
of pairs of poles, the variation of an alternator is p times the variation of its 
prime mover, if direct-connected, and pn times the variation of the prime mover 
if rigidly connected thereto in the velocity ratio n; so that the speed of the 
alternator is n times that of the prime mover. 

IJC. PERFORMANCE SPECIFICATIONS A\« TESTS. 

A. RATING. 

65. Rating by Output. All electrical apparatus should be rated by output 
and not by input. Generators, transformers, etc., should be rated by elec- 
trical output: motors by mechanical output, and preferably in kilowatts. 

65a. The following four classes of rating are recognized and recommended: 
they do not cover the rating of railway motors, which is treated in Appendix B, 
and there are other large though less definitely definable classes of service in 
which each case must be treated by itself. Some of these may be later reduced 
to fairly simple terms and introduced into these Rules. 

656. (1) Continuous Rating in which under load there is the attainment of 
approximately stationary temperature, and no other limit of capacity is ex- 
ceeded. 

65c. (2) Intermittent Rating in which one minute periods of load and rest 
alternate until the attainment of approximately stationary temperature and 
no other limit of capacity is exceeded. 

65d. Note. Since the temperature depends upon the losses and the 
capacity of the apparatus to emit them, a constant load may be substituted for 
the intermittent load in determining the temperature, provided the losses are 
equivalent. 

65e. (3) Minute Rating in which under load for one minute, no mechanical, 
thermal, magnetic, or electrical limit of capacity is exceeded and no permanent 
change is wrought in the apparatus. 

65/. (4) Variable Service Rating. It is desirable here to recognize this 
class of rating which is intended to cover the rating of motors for machine- 
tool and similar service, in which the thermal absorptive capacity plays a part. 
The specifications for this rating have not been fully determined at the time 
that this edition of the Rules goes to press. 



PERFORMANCE SPECIFICATIONS AND TESTS. 507 

66. Rating in Kilowatts. Electrical power should be expressed in kilo- 
watts, except when otherwise specified. 

67. Apparent Power, Kilovolt-Amperes. Apparent power in alternating- 
current circuits should be expressed in kilovolt-amperes as distinguished from 
effective power in kilowatts. When the power-factor is 100 per cent, the ap- 
parent power in kilovolt-amperes is equal to the kilowatts. 

68. The Rated (Full-Load) Current is that current which, with the rated 
terminal voltage, gives the rated kilowatts, or the rated kilovolt-amperes. In 
machines in which the rated voltage differs from the no-load voltage, the rated 
current should refer to the former. 

69. Determination of Rated Current. The rated current may be de- 
termined as follows: If P = rating in watts, or volt-amperes if the power- 
factor be other than 100 per cent, and E = full-load terminal voltage, the 
rated current per terminal is: 

P 

70. I = — amperes, in a direct-current machine or single-phase alternator, 

1 P 

71. I = — — — amperes, in a three-phase alternator. 

v3 & 

1 P 

72. I = - — amperes, in a quarter-phase alternator. 

73. Normal Conditions. The rating of machines or apparatus should be 
based upon certain normal conditions to be assumed as standard, or to be 
specified. These conditions include voltage, current, power-factor, frequency, 
wave shape and speed; or such of them as may apply in each particular case. 
Performance tests should be made under these standard conditions unless 
otherwise specified. 

74. a. Power-Factor. Since the inherent capacity of alternating-current 
generators, synchronous motors, and transformers, depends upon their voltage 
and their current, they should be rated in kilovolt-amperes. If the apparatus 
is rated in kilowatts without specification as to the power-factor, a power-factor 
of 100 per cent shall be understood. 

If rated in kilowatts and a power-factor other than 100 per cent be specified, 
this should be understood as defining only the nature of the load, and not as 
implying an increase in the ampere rating of the apparatus, which should be 
based upon the kilowatt rating at 100 per cent power-factor. 

75. 6. Wave Shape. In determining the rating of alternating-current ma- 
chines or apparatus, a sine- wave shape of alternating current and voltage is 
assumed, except where a distorted wave shape is inherent to the apparatus. 
See Sees. 79-80. 

76. Fuses. The rating of a fuse should be the maximum current which it 
will continuously carry. 

77. Circuit-Breakers. The rating of a circuit-breaker should be the max- 
imum current which it is designed to carry continuously. 

77a. Note. In addition thereto, the maximum current and voltage at 
which a fuse or a circuit-breaker will open the circuit should be specified. It 
is to be noted that the behavior of fuses and of circuit-breakers is much influ- 
enced by the amount of electric power available on the circuit. 

78. Indicating Meters should be rated according to their full-scale reading 
of volts, amperes, or watts. In wattmeters the rated volts and rated amperes 
should also be included; i.e., the volts and amperes which can be safely and 
continuously carried by the voltage and current coils respectively. 

78a. Watt-Hour Meters should be rated in volts and amperes. 

B. WAVE SHAPE. 
_ 79. The Sine Wave should be considered as standard, except where a de- 
viation therefrom is inherent in the operation of the apparatus. 

80. A Maximum Deviation of the wave from sinusoidal shape not exceeding 
10 per cent is permissible, except when otherwise specified. See Sees. 5;, 81, 
82, 83. See Sees, he to hi. 

C. EFFICIENCY. 
(I) Definitions. 

84. The Efficiency of an apparatus is the ratio of its output to its input. 
The output and input may be in terms of watt-hours, watts, volt-amperes, 
amperes, or any other quantity of interest, thus respectively defining energy- 



508 STANDARDIZATION RULES. 

efficiency, power-efficiency, apparent power-efficiency, current efficiency, etc. 
Unless otherwise specified, however, the term is ordinarily assumed to refer to 
power-efficiency. An exception should be noted in the case of luminous sources 
(see Sec. 346). 

86. Apparent Efficiency. In apparatus in which a phase displacement is 
inherent to their operation, apparent efficiency should be understood as the 
ratio of net power output to volt-ampere input. 

87. a. Note. Such apparatus comprises induction motors, synchronous 
phase modifiers, synchronous converters controlling the voltage of an alter- 
nating-current system, potential regulators, open magnetic circuit transformers, 
etc. 

88. b. Note. Since the apparent efficiency of apparatus delivering electrio 
power depends upon the power-factor of the load, the apparent efficiency, 
unless otherwise specified, should be referred to a load power-factor of unity. 

(II) Measurement of Efficiency. 

89. Methods. Efficiency may be determined by either of two methods, 
viz.: by measurement of input and output or by measurement of losses. 

90. a. Method of Input and Output. The input and output may both 
be measured directly. The ratio of the latter to the former is the efficiency. 

91. b. Method by Losses. The losses may be measured either collec- 
tively or individually. The total losses may be added to the output to derive 
the input, or subtracted from the input to derive the output. 

92. Comparison of Methods. The output and input method is preferable 
with small machines. When, however, as in the case of large machines, it is 
impracticable to measure the output and input, or when the percentage of 
power loss is small and the efficiency is nearly unity, the method of deter- 
mining efficiency by measuring the losses should be followed. 

93. Electric Power should be measured at the terminals of the apparatus. 
In tests of polyphase machines, the measurement of power should not be con- 
fined to a single circuit but should be extended to all the circuits in order to 
avoid errors of unbalanced loading. 

94. Mechanical Power in machines should be measured at the pulley, gear- 
ing, coupling, etc., thus excluding the loss of power in said pulley, gearing or 
coupling, but including the bearing friction and windage. The magnitude of 
bearing friction and windage may be considered, with constant speed, as inde- 
pendent of the load. The loss of power in the belt and the increase of bearing 
friction due to belt tension should be excluded. Where, however, a machine 
is mounted upon the shaft of a prime mover, in such a manner that it cannot 
be separated therefrom, the frictional losses in bearings and in windage, which 
ought, by definition, to be included in determining the efficiency, should be 
excluded, owing to the practical impossibility of separating them from those of 
the prime mover. 

95. In Auxiliary Apparatus, such as an exciter, the power lost in the auxiliary 
apparatus shouldjnot be charged to the principal machine, but to the plant con- 
sisting of principal machine and auxiliary apparatus taken together. The plant 
efficiency in such cases should be distinguished from the machine efficiency. 

96. Normal Conditions. Efficiency tests should be made under normal 
conditions herein set forth, which are to be assumed as standard. These con- 
ditions include voltage, current, power-factor, frequency, wave shape, speed, 
temperature and barometric pressure, or such of them as may apply in each 
particular case. Performance tests should be made under these standard con- 
ditions unless otherwise specified. See Sees. 73-75. 

97. a. Temperature. The efficiency of ail apparatus, except such as may 
be intended for intermittent service, should be either measured at, or reduced 
to, the temperature which the apparatus assumes under continuous operation 
at rated load, referred to a room temperature of 25° C. See Sees. 267-292. 

98. With apparatus intended for intermittent service, the efficiency should 
be determined at the temperature assumed under specified conditions. 

99. 6. Power-Factor. In determining the efficiency of alternating-current 
apparatus, the electric power should be measured when the current is in phase 
with the voltage, unless otherwise specified, except when a definite phase 
difference is inherent in the apparatus, as in induction motors, induction gen- 
erators, frequency converters, etc. 

100. c. Wave Shape. In determining the efficiency of alternating-current 
apparatus, the sine-wave should be considered as standard, except where a 
difference in the wave form from the sinusoidal is inherent in the operation of 
the apparatus. See Sec. 80. 



PERFORMANCE SPECIFICATIONS AND TESTS. 509 

(III) Measurement of Losses. 

101. Losses. The usual sources of losses in electrical apparatus and the 
methods of determining these losses are as follows: 

(A) Bearing Friction and Windage. 

102. The magnitude of bearing friction and windage (which may be con- 
sidered as independent of the load) is conveniently measured by driving the 
machine from an independent motor, the output of which may be suitably 
determined. See Sec. 94. 

(B) Commutator Brush Friction. 

103. The magnitude of the commutator brush friction (which may be con- 
sidered as independent of the load) is determined by measuring the difference 
in power required for driving the machine with brushes on and with brushes 
off (the field being unexcited). 

(C) Collector-Ring Brush Friction. 

104. Collector-ring brush friction may be determined in the same manner 
as commutator brush friction. It is usually negligible. 

(D) Molecular Magnetic Friction and Eddy Currents. 

105. These losses include those due to molecular magnetic friction and eddy 
currents in iron and copper and other metallic parts, also the losses due to 
currents in the cross-connections of cross-connected armatures. 

106. In Machines these losses should be determined on open circuit and at a 
voltage equal to the rated voltage + Ir in a generator, and — Ir in a motor, 
where I\ denotes the current strength and r denotes the internal resistance of 
the machine. They should be measured at the correct speed and voltage, 
since they do not usually vary in any definite proportion to the speed or to the 
voltage. 

107. Note. The Total Losses in bearing friction and windage, brush fric- 
tion, magnetic friction and eddy currents can, in general, be determined by a 
single measurement by driving the machine with the field excited, either as a 
motor, or by means of an independent motor. 

108. Retardation Method. The no-load iron, friction, and windage losses 
may be segregated by the Retardation Method. The generator should be 
brought up to full speed (or, if possible, to about 10 per cent above full speed) 
as a motor, and, after cutting off the driving power and excitation, frequent 
readings should be taken of speed and time, as the machine slows down, from 
which a speed-time curve can be plotted. A second curve should be taken in 
tha same manner, but with full field excitation; from the second curve the iron 
losses may be found by subtracting the losses found in the first curve. 

109. The speed-time curves can be plotted automatically by belting a small 
separately excited generator (say & kw.) to the generator shaft and connecting 
it to a recording voltmeter. 

(E) Armature-Resistance Loss. 

110. This loss may be expressed by pl 2 r; where r = resistance of one arma- 
ture circuit or branch, / = the current in such armature circuit or branch, 
and p = the number of armature circuits or branches. 

(F) Commutator, Brush and Brush-Contact Resistance Loss. 

111. It is desirable to point out that with carbon brushes these losses may 
be considerable in low-voltage machines. 

(G) Collector-Ring and Brush-Contact Resistance Loss^ 

112. This loss is usually negligible, except in machines of extremely low 
voltage or in unipolar machines. 

(H) FIELD-EXCITATION LOSS. 

113. With separately excited field, the loss of power in the resistance of the 
field coils alone should be considered. With either shunt- or series-field wind- 
ings, however, the loss of power in the accompanying rheostat should also be 
included, the said rheostat being considered as an essential part of the machine, 
and not as separate auxiliary apparatus. 

(I) Load Losses 

114. The load losses may be considered as the difference between the total 
losses under load and the sum of the losses as above specified and determined 



510 STANDARDIZATION RULES. 

115. a. In Commutating Machines of small field distortion, the load losses 
are usually trivial and may, therefore, be neglected. When, however, the 
field distortion is large as in commutating-pole machines, or, as is shown, for 
instance, by the necessity for shifting the brushes between no load and full 
load on non-commutating pole machines, these load losses may be consider- 
able, and should be taken into account. In this case the efficiency may be 
determined either by input and output measurements, or the load losses may 
be estimated by the method of Sec. 116. 

116. b. Estimation of Load Losses. While the load losses cannot well 
be determined individually, they may be considerable and, therefore, their 
joint influence should be determined by observation. This can be done by 
operating the machine on short-circuit and at full-load current, that is, by 
determining what may be called the "short-circuit core loss." With the low 
field intensity and great lag of current existing in this case, the load losses are 
usually greatly exaggerated. 

117. One-third of the short-circuit core loss may, as an approximation, and 
in the absence of more accurate information, be assumed as the load loss. 

(IV) Efficiency of Different Types of Apparatus. 

(A) Direct-Current Commutating Machines. 

118. In Direct-Current Commutating Machines the losses are: 

119. a. Bearing Friction and Windage. See Meas. of Losses (A), Sec. 102. 

120. b. Molecular Magnetic Friction and Eddy Currents. See 
Meas. of Losses (D), Sec. 105. 

121. c. Armature Resistance Losses. See Meas. of Losses (E), Sec. 110. 

122. d. Commutator Brush Friction. See Meas. of Losses (B), Sec. 103. 

123. e. Commutator, Brush and Brush-Contact Resistance. See Meas. 
of Losses (F), Sec. 111. 

124. /. Field-Excitation Loss. See Meas. of Losses (H), Sec. 113. 

125. g. Load Losses. See Meas. of Losses (7), Sec. 114. 

126. Note, b and c are losses in the armature or "armature losses"; d and 
e "commutator losses"; / "field losses." 

(B) Alternating-Current Commutating Machines. 

127. In Alternating-Current Commutating Machines, the losses are: 

128. a. Bearing Friction and Windage. See Meas. of Losses (A), Sec. 102. 

129. b. Rotation Loss, measured with the machine at open circuit, the 
brushes on the commutator, and the field excited by alternating current when 
driving the machine by a motor. 

130. This loss includes molecular magnetic friction and eddy currents, 
caused by rotation through the magnetic field, I 2 r losses in cross-connections 
of cross-connected armatures, I 2 r and other losses in armature-coils and arma- 
ture-leads which are short-circuited by the brushes as far as these losses are 
due to rotation. 

131. c. Alternating or Transformer Loss. These losses are measured 
by wattmeter in the field circuit, under the conditions of test b. They include 
molecular magnetic friction and eddy currents due to the alternation of the 
magnetic field, I 2 r losses in cross-connections of cross-connected armatures, 
I 2 r and other losses in armature coil and commutator leads which are short- 
circuited by the brushes, as far as these losses are due to the alternation of the 
magnetic flux. 

132. The losses in armature-coils and commutator leads short-circuited by 
the brushes can be separated in b and c from the other losses by running the 
machine with and without brushes on the commutator. 

133. d. I 2 R Loss, other load losses in armature and compensating winding 
and I 2 r loss of brushes, may be measured by a wattmeter connected across the 
armature and compensating winding. 

134. e. Field-Excitation Loss. See Meas. of Losses (//), Sec. 113. 

135. /. Commutator Brush-Friction. See Meas. of Losses (£), Sec. 103. 

(C) Synchronous Commutating Machines. 

136. 1. In Double-Current Generators, the efficiency of the machine 
should be determined as a direct-current generator, and also as an alternating- 
current generator. The two values of efficiency may be different, and should 
be clearly distinguished. 

137. 2. In Converters the losses should be determined when driving the 
machine by a motor. These losses are: 

138. a. Bearing Friction and Windage. See Meas. of Losses (A), Sec. 102, 



PERFORMANCE SPECIFICATIONS AND TESTS. 511 

139. b. Molecular Magnetic Friction and Eddy Currents. See 
Meas. of Losses (D), Sec. 105. 

140. c. Armature-Resistance Loss. This loss in the armature is ql 3 r, 
where / = direct current in armature, r = armature resistance, and q, a factor 
which is equal to 1.47 in single-circuit single-phase, 1.15 in double-circuit single- 
phase, 0.59 in three-phase, 0.39 in two-phase, and 0.27 in six-phase converters. 

141. d. Commutator-Brush Friction. See Meas. of Losses (B) , Sec. 103. 

142. e. Collector-Ring Brush Friction. See Meas. of Losses (C), Sec. 104. 

143. /. Commutator, Brush and Brush-Contact Resistance Loss. See 
Meas. of Losses (F), Sec. 111. 

144. g. Collector-Ring Brush-Contact Resistance Loss. See Meas. 
of Losses (G), Sec. 112. 

145. h. Field-Excitation Loss. See Meas. of Losses (H), Sec. 109. 

146. t. Load Losses. These can generally be neglected, owing to the 
absence of field distortion. 

147. 3. The Efficiency of Two Similar Converters may be determined by 
operating one machine as a converter from direct to alternating, and the 
other as a converter from alternating to direct, connecting the alternating 
sides together, and measuring the difference between the direct-current input 
and the direct-current output. This process may be modified by returning 
the output of the second machine through two boosters into the first machine 
and measuring the losses. Another modification is to supply the losses by 
an alternator between the two machines, using potential regulators. 

(Z>) Synchronous Machines. 

148. In Synchronous Machines, the losses are: 

149. a. Bearing Friction and Windage. See Meas. of Losses (A), Sec. 102. 

150. b. Molecular Magnetic Friction and Eddy Currents. See Meas. 
of Losses (D), Sec. 105. 

151. c. Armature-Resistance Loss. See Meas. of Losses (E), Sec. 110. 

152. d. Collector-Ring Brush Friction. See Meas. of Losses (C), Sec. 
104. 

153. e. Collector-Ring Brush-Contact Resistance Loss. See Meas. 
of Losses (GO, Sec. 112. 

154. /. Field-Excitation Loss. See Meas. of Losses (H), Sec. 113. 

155. g. Load Losses. See Meas. of Losses (/), Sec. 114. 

(E) Stationary Induction Apparatus. 

156. In Stationary Induction Apparatus, the losses are: 

157. a. Molecular Magnetic Friction and Eddy Currents measured at open 
secondary circuit, rated frequency, and at rated voltage — Ir, where / = rated 
current, r = resistance of primary circuit. 

158. b. Resistance Losses, the sum of the Pr losses in the primary and in 
the secondary windings of a transformer, or in the two sections of the coil in a 
compensator or auto-transformer, where J = rated current in the coil or section 
of coil, and r = resistance. 

159. c. Load Losses, i.e., eddy currents in the iron and especially in the 
copper conductors, caused by the current at rated load. For practical pur- 
poses they may be determined by short-circuiting the secondary of the trans- 
former and impressing upon the primary a voltage sufficient to send rated-load 
current through the transformer. The loss in the transformer under these 
conditions, measured by wattmeter, gives the load losses + I 2 r losses in both 
primary and secondary coils. 

160. In Closed Magnetic Circuit Transformers, either of the two circuits 
may be used as primary when determining the efficiency. 

161. In Potential Regulators, the efficiency should be taken at the maximum 
voltage for which the apparatus is designed, and with noninductive load, unless 
otherwise specified. 

(F) Rotary Induction Apparatus or Induction Machines. 

162. In Rotary Induction Apparatus, the losses are: 

163. a. Bearing Friction and Windage. See Meas. of Losses (A), Sec. 102. 

164. b. Molecular Magnetic Friction and Eddy Currents in iron, copper 
and other metallic parts; also I 2 r losses which may exist in multiple-circuit 
windings, a and b together are determined by running the motor without 
load at rated voltage, and measuring the power input. 

165. c. Primary I 2 R Loss, which may be determined by measurement of 
the current and the resistance. 



512 STANDARDIZATION RULES. 

166. d. Secondary PR Loss, which may be determined as in the primary 
when feasible; otherwise, as in squirrel-cage secondaries, this loss is measured 
as part of e. 

167. e. Load Losses; i.e., molecular magnetic friction, and eddy currents 
in iron, copper, etc., caused by the stray field of primary and secondary cur- 
rents, and secondary PR loss when undeterminable under (d). These losses 
may for practical purposes be determined by measuring the total power, with 
the rotor short-circuited at standstill and a current in the primary circuit 
equal to the primary energy current at full load. The loss in the motor under 
these conditions may be assumed to be equal to the load losses + Pr losses in 
both primary and secondary coils. 

(G) Unipolar or Acyclic Machines. 

168. In Unipolar Machines, the losses are: 

169. (a) Bearing Friction and Windage. See Meas. of Losses (A), Sec. 
102. 

170. (b) Molecular Magnetic Friction and Eddy Currents. See 
Meas. of Losses (E), Sec. 106. 

171. (c) Armature-Resistance Losses. See Meas. of Losses (E), Sec. 110. 

172. (d) Collector-Brush Friction. See Meas. of Losses (C), Sec. 104. 

173. (e) Collector Brush-Contact Resistance. See Meas. of Losses 
(G), Sec. 112. 

174. (/) Field-Excitation. See Meas. of Losses (H), Sec. 113. 

175. (g) Load Losses. See Meas. of Losses (/), Sec. 114. 

(H) Rectifying Apparatus, Pulsating-Current Generators. 

176. This division includes: open-coil arc machines and mechanical and 
other rectifiers. 

177. In Rectifiers the most satisfactory method of determining the efficiency 
is to measure both electric input and electric output by wattmeter. The 
input is usually inductive, owing to phase displacement and to wave distor- 
tion. For this reason the power-factor and the apparent efficiency should also 
be considered, since the latter may be much lower than the true efficiency. 
The power consumed by auxiliary devices, such as the synchronous motor or 
cooling devices, should be included in the electric input. 

178. In Constant-Current Rectifiers, transforming from constant potential 
alternating to constant direct current, by means of constant-current trans- 
forming devices and rectifying devices, the losses in the transforming devices 
are to be included in determining the efficiency and have to be measured when 
operating the rectifier, since in this case the losses may be greater than when 
feeding an alternating secondary circuit. In constant-current transforming 
devices, the load losses may be considerable, and, therefore, should not be 
neglected. 

179. In Open-Coil Arc Machines, the losses are essentially the same as in 
direct-current (closed coil) commutating machines. In this case, however, 
the load losses are usually greater, and the efficiency should preferably be 
measured by input- and output-test, using wattmeters for measuring the 
output. 

179a. In alternating-current rectifiers, the output should, in general, be 
measured by wattmeter and not by voltmeter and ammeter, since, owing to 
pulsation of current and voltage, a considerable discrepancy may exist between 
watts and volt-amperes. If, however, a direct-current and an alternating- 
current meter in the rectified circuit (either a voltmeter or an ammeter) give 
the same reading, the output may be measured by direct-current voltmeter and 
ammeter. The type of alternating-current instrument here referred to should 
indicate the effective or root-of-mean-square value and the type of direct- 
current instrument the arithmetical mean value, which would be zero on an 
alternating-current circuit. 
(J) Transmission Lines. 

180. The efficiency of transmission lines should be measured with non- 
inductive load at the receiving end, with the rated receiving voltage and 
frequency, also with sinusoidal impressed wave form, except where expressly 
specified otherwise, and with the exclusion of transformers or other apparatus 
at the ends of the line. 

(./) Phase-Displacing Apparatus. 

183. In Synchronous Phase-Modifiers and exciters of induction generators, 
the determination of losses is the same as in other synchronous machines. 



PERFORMANCE SPECIFICATIONS AND TESTS. 513 

184. In Reactors, the losses are molecular magnetic friction, eddy losses and 
Vr loss. They should be measured by wattmeter. The losses of reactors 
should be determined with a sine wave of impressed voltage except where 
expressly specified otherwise. 

185. In Condensers, the losses are due to dielectric hysteresis and leakage, 
and should be determined by wattmeter with a sine wave of voltage or by an 
alternating-current bridge method. 

186. In Polarization Cells, the losses are those due to electric resistivity 
and a loss in the electrolyte of the nature of chemical hysteresis. These losses 
may be considerable. They depend upon the frequency, voltage and temper- 
ature, and should be determined with a sine wave of impressed voltage, except 
where expressly specified otherwise. 

D. REGULATION. 

(I) Definitions. 

187. The Regulation of a machine or apparatus in regard to some charac- 
teristic quantity (such as terminal voltage, current or speed) is the ratio of the 
deviation of that quantity from its normal value at rated load to that normal 
value. The term "regulation," therefore, has the same meaning as the term 
"inherent regulation," occasionally used. 

188. Constant Standard. If the characteristic quantity is intended to 
remain constant {e.g., constant voltage, constant speed, etc.) between rated 
load and no load, the regulation is the ratio of the maximum variation from 
the rated-load value to the no-load value. 

189. Varying Standard. If the characteristic quantity is intended to vary 
in a definite manner between rated load and no load, the regulation is the 
ratio of the maximum variation from the specified condition to the normal 
rated-load value. 

190. (a) Note. If the law of the variation (in voltage, current, speed, etc.) 
between rated load and no load is not specified, it should be assumed to be a 
simple linear relation; i.e., one undergoing uniform variation between rated 
load and no load. 

191. (6) Note. The regulation of an apparatus may, therefore, differ 
according to its qualification for use. Thus, the regulation of a compound- 
wound generator specified as a constant-potential generator will be different 
from that which it possesses when specified as an over-compounded generator. 

192. In Constant-Potential Machines, the regulation is the ratio of the 
maximum difference of terminal voltage from the rated-load value (occurring 
within the range from rated load to open circuit) to the rated-load terminal 
voltage. 

193. In Constant-Current Machines, the regulation is the ratio of the 
maximum difference of current from the rated-load value (occurring within 
the range from rated-load to short-circuit, or minimum limit of operation) to 
the rated-ioad current. 

194. In Constant-Power Apparatus, the regulation is the ratio of maxi- 
mum difference of power from the rated-load value (occurring within the range 
of operation specified) to the rated power. 

195. In Constant-Speed Direct-Current Motors and Induction Motors, the 
regulation is the ratio of the maximum variation of speed from its rated-load 
value (occurring within the range from rated load to no load) to the rated-load 



196. The regulation of an induction motor is, therefore, not identical with 
the slip of the motor, which is the ratio of the drop in speed from synchronism 
to the synchronous speed. 

197. In Constant-Potential Transformers, the regulation is the ratio" of 
the rise of secondary terminal voltage from rated non-inductive load to no load 
(at constant primary impressed terminal voltage) to the secondary terminal 
voltage at rated load. 

198. In Over-Compounded Machines, the regulation is the ratio of the 
maximum difference in voltage from a straight line connecting the no-load 
and rated-load values of terminal voltage as function of the load current to 
the rated-load terminal voltage. 

199. In Converters, Dynamotors, Motor-Generators and Frequency Con- 
verters, the regulation is the ratio of the maximum difference of terminal 
voltage at the output side from the rated-load voltage to the rated-load 
voltage on the output side. 

200. In Transmission Lines, Feeders, etc., the regulation is the ratio of the 



514 STANDARDIZATION RULES. 

maximum voltage difference at the receiving end, between rated non-inductive 
load and no load, to the rated-load voltage at the receiving end (with constant 
voltage impressed upon the sending end). 

201. In Steam Engines, the regulation is the ratio of the maximum varia- 
tion of speed in passing slowly from rated load to no load (with constant 
steam pressure at the throttle) to the rated-load speed. For variation and 
pulsation see Sees. 59-64. 

202. In a Hydraulic Turbine or Other Water-Motor, the regulation is the 
ratio of the maximum variation of speed in passing slowly from rated load to 
no load (at constant head of water; i.e., at constant difference of level between 
tail race and head race) to the rated-load speed. For variation and pulsation 
see Sees. 59-64. 

203. In a Generator-Unit, consisting of a generator united with a prime- 
mover, the regulation should be determined at constant conditions of the 
prime-mover; i.e., constant steam pressure, head, etc. It includes the inher- 
ent speed variations of the prime-mover. For this reason the regulation of a 
generator-unit is to be distinguished from the regulation of either the prime- 
mover, or of the generator contained in it, when taken separately. 

(II) Conditions for and Tests of Regulation. 

204. Speed. The Regulation of Generators is to be determined at constant 
speed, and of alternating apparatus at constant impressed frequency. 

205. Non-Inductive Load. In apparatus generating, transforming or 
transmitting alternating currents, regulation should be understood to refer to 
non-inductive load, that is, to a load in which the current is in phase with the 
E.M.F. at the output side of the apparatus, except where expressly specified 
otherwise. 

206. Wave Form. In alternating apparatus receiving electric power, regu- 
lation should refer to a sine wave of E.M.F., except where expressly specified 
otherwise. 

207. Excitation. In commutating machines, rectifying machines, and 
synchronous machines, such as direct-current generators and motors, alter- 
nating-current and polyphase generators, the regulation is to be determined 
under the following conditions: 

(1) At constant excitation in separately excited fields. 

(2) With constant resistance in shunt-field circuits, and 

(3) With constant resistance shunting series-field circuits; i.e., the field 
adjustment should remain constant, and should be so chosen as to give the 
required rated-load voltage at rated-load current. 

208. Impedance Ratio. In alternating-current apparatus, in addition to 
the non-inductive regulation, the impedance ratio of the apparatus should be 
specified; i.e., the ratio of the voltage consumed by the total internal im- 
pedance of the apparatus at rated-load current to its rated-load voltage. As 
far as possible, a sinusoidal current should be used. 

209. Computation of Regulation. In synchronous machines, the open- 
circuit exciting ampere-turns corresponding to terminal voltage plus armature- 
resistance-drop and the exciting ampere-turns at short-circuit for rated-load 
current should be combined vectorially to obtain the resultant ampere-turns, 
and the corresponding internal E.M.F. should be taken from the saturation 
curve. 

E. INSULATION. . 
(I) Insulation Resistance. 

210. Insulation Resistance is the ohmic resistance offered by an insulating 
coating, cover, material or support to an impressed voltage, tending to produce 
a leakage of current through the same. 

211. Ohmic Resistance and Dielectric Strength. The ohmic resistance 
of the insulation is of secondary importance only, as compared with the dielec- 
tric strength, or resistance to rupture by high voltage. Since the ohmic re- 
sistance of the insulation can be very greatly increased by baking, but the 
dielectric strength is liable to be weakened thereby, it is preferable to specify 
a high dielectric strength rather than a high insulation resistance. The high- 
voltage test for dielectric strength should always be applied. 

212. Recommended Value of Resistance. The insulation resistance of 
completed apparatus should be such that the rated terminal voltage of the 

apparatus will not send more than of the rated-load current through 



PERFORMANCE SPECIFICATIONS AND TESTS. 515 

the insulation. Where the value found in this way exceeds one megohm, it is 
usually sufficient. 

213. Insulation Resistance Tests should, if possible, be made at the pressure 
for which the apparatus is designed. 

(II) Dielectric Strength. 
(A) Test Voltages. 

214. Definition. The dielectric strength of an insulating wall, coating, 
cover or path is measured by the voltage which must be applied to it in order 
to effect a disruptive discharge through the same. 

215. Basis for Determining Test Voltages. The test voltage which 
should be applied to determine the suitability of insulation for commercial 
operation is dependent upon the kind and size of the apparatus, and its normal 
operating voltage upon the nature of the service in which it is to be used and 
the severity of the mechanical and electrical stresses to which it may be sub- 
jected. The voltages and other conditions of test which are recommended 
have been determined as reasonable and proper for the great majority of cases 
and are proposed for general adoption, except when specific reasons make a 
modification desirable. 

216. Condition op Apparatus to be Tested. Commercial tests should, 
in general, be made with the completely assembled apparatus and not with 
individual parts. The apparatus should be in good condition and high- 

i voltage tests, unless otherwise specified, should be applied before the machine 
is put into commercial service, and should not be applied when the insulation 
resistance is low owing to dirt or moisture. High-voltage tests should, in 
general, be made at the temperature assumed under normal operation. High- 
voltage tests considerably in excess of the normal voltages to determine whether 
specifications are fulfilled are admissible on new machines only. Unless 
otherwise agreed upon, high- voltage tests of a machine should be understood 
as being made at the factory. 

217. Points of Application of Voltage. The test voltage should be suc- 
cessively applied between each electric circuit and all other electric circuits 
including conducting material in the apparatus. 

218. The Frequency of the alternating-current test voltage is, in general, 
immaterial within commercial ranges. When, however, the frequency has an 
appreciable effect, as in alternating-current apparatus of high voltage and 
considerable capacity, the rated frequency of the apparatus should be used. 

219. Table of Testing Voltages. The following voltages are recom- 
mended for testing all apparatus, lines and cables, by a continued application 
for one minute. The test should be with alternating voltage having a virtual 
value (or root mean square referred to a sine wave of voltage) given in the 
table, and preferably for tests of alternating apparatus at the normal frequency 
of the apparatus. 

220. Rated Terminal Voltage of Circuit. Rated Output. Testing Voltage. 
Not exceeding 400 volts Under 10 kw. . . 1,000 volts 

4444 44 4t 10 kw. and over . 1,500 " 

400 and over, but less than 800 volts . . Under 10 kw. . . 1,500 " 

44 " 44 44 ,4 " . . 10 kw. and over . 2,000 * 4 

800 M 44 44 1,200 " . . Any 3,500 " 

1,200 " u M 2,500 " . . Any 5,000 " 

2,500 44 44 Any . . Double the normal 

rated voltages. 

221. Exception. — Transformers. Transformers having primary pres- 
sures of from 550 to 5,000 volts, the secondaries of which are directly con- 
nected to consumption circuits, should have a testing voltage of 10,000 volts, 
to be applied between the primary and secondary windings, and also between 
the primary winding and the core. 

222. Exception. — Field Windings. The tests for field windings should 
be based on the rated voltage of the exciter and the rated output of the ma- 
chine of which the coils are a part. Field windings of synchronous motors and 
converters, which are to be started by applying alternating current to the 
armature when the field is not excited and when a high voltage is induced in 
the field windings, should be tested at 5,000 volts. 

223. Rated Terminal Voltage. — Definition. The rated terminal volt- 
age of circuit in the above table means the voltage between the conductors of 
the circuit to which the apparatus to be tested is to be connected; for in- 
stance, in three-phase circuits the delta voltage should be taken. In the 



516 STANDARDIZATION RULES. 

following specific cases, the rated terminal voltage of the circuit is to be de- 
termined as specified in ascertaining the testing voltage : 

224. (a) Transformers. The test of the insulation between the primary 
and secondary windings of transformers is to be the same as that between the 
high-voltage windings and core, and both tests should be made simultaneously 
by connecting the low-voltage winding and core together during the test. If 
a voltage equal to the specified testing voltage be induced in the high-voltage 
winding of a transformer it may be used for insulation tests instead of an in- 
dependently induced voltage. These tests should be made first with one end 
and then with the other end of the high-tension winding connected to the low- 
tension winding and to the core. 

225. (6) Constant-Current Apparatus. The testing voltage is to be 
based upon a rated terminal voltage equal to the maximum voltage which may 
exist at open or closed circuit. 

226. (c) Apparatus in Series. For tests of machines or apparatus to be 
operated in series, so as to employ the sum of their separate voltages, the 
testing voltage is to be based upon a rated terminal voltage equal to the sum 
of the separate voltages except where the frames of the machines are separately 
insulated, both from the ground and from each other, in which case the test 
for insulation between machines should be based upon the voltage of one 
machine, and the test between each machine and ground to be based upon the 
total voltage of the series. 

(B) Methods of Testing. 

227. Classes of Tests. Tests for dielectric strength cover such a wide 
range in voltage that the apparatus, methods and precautions which are essen- 
tial in certain cases do not apply to others. For convenience, the tests will be 
separated into two classes: 

228. Class 1. This class includes all apparatus for which the test voltage 
does not exceed 10 kilovolts, unless the apparatus is of very large static capacity, 
e.g., a large cable system. This class also includes all apparatus of small static 
capacity, such as line insulators, switches and the like, for all test voltages. 

229. Method of Test for Class 1. The test voltage is to be continuously 
applied for the prescribed interval (one minute, unless otherwise specified). 
The test voltage may be taken from a constant-potential source and applied 
directly to the apparatus to be tested, or it may be raised gradually as specified 
for tests under Class 2. 

230. Class 2. This class includes all apparatus not included in Class 1. 

231. Method of Test for Class 2. The test voltage is to be raised to 
the required value smoothly and without sudden large increments and is then 
to be continuously applied for the prescribed interval (one minute, unless 
otherwise specified), and then gradually decreased. 

232. Conditions and Precautions for Class 1 and Class 2. The follow- 
ing apply to all tests: 

233. The Wave Shape should be approximately sinusoidal and the apparatus 
in the testing circuits should not materially distort this wave. 

234. The Supply Circuit should have ample current-supply capacity so that 
the charging current which may be taken by the apparatus under test will 
not materially alter the wave form nor materially affect the test voltage. 
The circuit should be free from accidental interruptions. 

235. Resistance or Inductance in series with the primary of a raising trans- 
former for the purpose of controlling its voltage is liable seriously to affect 
the wave form, thereby causing the maximum value of the voltage to bear a 
different and unknown ratio to the root mean square value. This method of 
voltage adjustment is, therefore, in general, undesirable. It may be noted 
that if a resistance or inductance is employed to limit the current when burn- 
ing out a fault, such resistance or inductance should^be short-circuited during 
the regular voltage test. 

236. The Insulation under test should be in normal condition as to dry- 
ness and the temperature should, when possible, be that reached in normal 
service. 

237. Additional Conditions and Precautions for Class 2. The follow- 
ing conditions and precautions, in addition to the foregoing, apply to tests of 
apparatus included in Class 2. 

238. Sudden Increment of Testing Voltage on the apparatus under test 
should be avoided, particularly at high voltages and with apparatus having 
considerable capacity, as a momentarily excessive rise in testing voltage will 
result. 



PERFORMANCE SPECIFICATIONS AND TESTS. 517 

239. Sudden Variations in Testing Voltage of the circuit supplying the 
voltage during the test should be avoided as they are likely to set up injurious 
oscillation. 

240. Good Connections in the circuits supplying the test voltage are essen- 
tial in order to prevent injurious high frequency„disturbances from being set 
up. When a heavy current is carried by a small water rheostat, arcirig may 
occur, causing high-frequency disturbances which should be carefully avoided. 

241. Transformer Coils. In high- voltage transformers, the low- voltage 
coil should preferably be connected to the core and to the ground when the 
high-voltage test is being made, in order to avoid the stress from low-voltage 
coil to core, which would otherwise result through condenser action. The 
various terminals of each winding of the high-tension transformer under test 
should be connected together during the test in order to prevent undue stress 
on the insulation between turns or sections of the winding in case the high- 
voltage test causes a breakdown. 

(C) Methods for Measuring the Test Voltage. 

242. For Measuring the Test Voltage, two instruments are in common 
use, (1) the spark gap and (2) the voltmeter. 

243. 1. The Spark Gap is ordinarily adjusted so that it will break down 
with a certain predetermined voltage, and is connected in parallel with the in- 
sulation under test. It ensures that the voltage applied to the insulation is 
not greater than the breakdown voltage of the spark gap. A given setting of 
the spark;gap is a measure of one definite voltage, and, as its operation depends 
upon the maximum value of the voltage wave, it is independent of wave form 
and is a limit on the maximum stress to which the insulation is subjected. The 
spark gap is not conveniently adapted for comparatively low voltages. 

244. In Spark-Gap Measurements, the spark gap may bo set for the re- 
quired voltage and the auxiliary apparatus adjusted to give a voltage at which 
this spark gap just breaks down. The spark gap should then be adjusted for, 
say, 10 per cent higher voltage, and the auxiliary apparatus again adjusted to 
give the voltage of the former breakdown, which is to be the assumed voltage 
for the test. This voltage is to be maintained for the required interval. 

245. The Spark Points should consist of new sewing needles, supported 
axially at the ends of linear conductors which are each at least twice the length 
of the gap. There should be no extraneous body near the gap within a radius 
of twice its length. A table of approximate striking distances is given in 
Appendix D. This table should be used in connection with tests made by the 
spark-gap methods. 

246. A Non-inductive Resistance of about one-half ohm per volt should be 
inserted in series with each terminal of the gap so as to keep the discharge 
current between the limits of one-quarter ampere and 2 amperes. The pur- 
pose of the resistance is to limit the current in order to prevent the surges 
which might otherwise occur at the time of breakdown. 

247. 2. The Voltmeter gives a direct reading, and the different values of the 
voltage can be read during the application and duration of the test. It is 
suitable for all voltages, and does not introduce disturbances into the test 
circuit. 

248. In Voltmeter Measurements, the voltmeter should, in general, derive 
its voltage from the high-tension testing circuit either directly or through an 
auxiliary ratio transformer. It is permissible, however, to measure the volt- 
age at other places, for example, on the primary of the transformer, pro- 
vided the ratio of transformation does not materially vary during the test; or 
that proper account is taken thereof. 

249. Spark Gap and Voltmeter. The spark gap may be employed as a 
check upon the voltmeter used in high-tension tests in order to determine 
the transformation ratio of the transformer, the variation from the sine wave 
form and the like. It is also useful in conjunction with voltmeter measure- 
ments to limit the stress applied to the insulating material. 

(D) Apparatus for Supplying Test Voltage. 

250. The Generator or Circuit supplying voltage for the test should have 
ample current carrying capacity, so that the current which may be taken for 
charging the apparatus to be tested will not materially alter the wave form nor 
otherwise materially change the voltage. 

The Testing Transformer should be such that its ratio of transformation 
does not vary more than 10 per cent when delivering the charging current 
required by the apparatus under test. (This may be determined by short- 
circuiting the secondary or high-voltage winding of the testing transformer 



518 STANDARDIZATION RULES. 

and supplying fa of the primary voltage to the primary under this condition. 
The primary current that flows under this condition is the maximum which 
should be permitted in regular dielectric test.) 

251. The Voltage Control may be secured in either of several ways, which, 
in order of preference, are as follows: 

252. 1. By generator field circuit. 

253. 2. By magnetic commutation. 

254. 3. By change in transformer ratio. 

255. 4. By resistance or choke coils. 

256. In Generator Voltage Control, the voltage of the generator should 
preferably be about its approximate normal rated-load value when the full 
testing voltage is attained, which requires that the ratio of the raising trans- 
former be such that the full testing voltage is reached when the generator 
voltage is normal. This avoids the instability in the generator which may 
occur if a considerable leading current is taken from it when it has low voltage 
and low field current. 

257. In Magnetic Commutation, the control is effected by shunting the mag- 
netic flux through a secondary coil so as to vary the induction through the 
coil and the voltage induced in it. The shunting should be effected smoothly, 
thus avoiding sudden changes in the induced voltage. 

258. In Transformer Voltage Control, by change of ratio, it is necessary 
that the transition from one step to another be made without interruption of 
the test voltage, and by steps sufficiently small to prevent surges in the testing 
circuit. The necessity of this precaution is greater as the inductance or the 
static capacity of the apparatus in the testing circuit under test is greater. 

259. When Resistance Coils or Reactors are used for voltage control, it is 
desirable that the testing voltage should be secured when the controlling 
resistance or reactance is very nearly or entirely out of circuit in order that 
the disturbing effect upon the wave form which results may be negligible at 
the highest voltage. 

F. CONDUCTIVITY. 

260. Copper. The conductivity of copper in annealed wires and in electric 
cables should not be less than 98 per cent of the Annealed Copper Standard, 
and the conductivity of hard-drawn copper wires should not be less than 95 
per cent of the Annealed Copper Standard. The Annealed Copper Standard 
represents a mass-resistivity of 0.153022 ohm per metergram at 20° C. or 
873.75 ohms per mile-pound at 20° C; or using a density of 8.89, a volume- 
resistivity of 1.72128 microhm-cm., or microhms in a cm. cube, at 20° C, or 
0.67767 microhm-inch at 20° C. 

G. RISE OF TEMPERATURE. 
(I) Measurement of Temperature. 
(A) Methods. 

261. There are two methods in common use for determining the rise in tem- 
perature, viz.: (1) by thermometer, and (2) by increase in resistance of an 
electric circuit. 

262. 1. By Thermometer. The following precautions should be observed 
in the use of thermometers: 

263. a. Protection. The thermometers indicating the room temperature 
should be protected from thermal radiation emitted by heated bodies, or 
from draughts of air or from temporary fluctuations of temperature. Several 
room thermometers should be used. In using the thermometer by applying 
it to a heated part, care should be taken so to protect its bulb as to prevent 
radiation from it, and, at the same time, not to interfere seriously with the 
normal radiation from the part to which it is applied. 

264. b. Bulb. When a thermometer is applied to the free surface of a 
machine, it is desirable that the bulb of the thermometer should be covered 
by a pad of definite area. A convenient pad may be formed of cotton waste 
in a shallow circular box about one and a half inches in diameter, through a 
slot in the side in which the thermometer bulb is inserted. An unduly large 
pad over the thermometer tends to interfere with the natural liberation of 
heat from the surface to which the thermometer is applied. 

265. 2. By Increase in Resistance. The resistance may be measured 
either by the Wheatstone bridge, the Thomson or Kelvin double bridge, the 
potentiometer method, or the ammeter and voltmeter method. If a tem- 
perature coefficient must be assumed, its value for copper may be taken to be 
0.00394 per degree C. from and at 20° C. or 0.00428 per degree C. from and at 



PERFORMANCE SPECIFICATIONS AND TESTS. 519 

0° C. This value holds for average commercial annealed copper. If the copper 
wire is hard-drawn, or if the conductivity is known, a different value of tem- 
perature coefficient should be taken, according to the explanation and dis- 
cussion of the temperature coefficient in Appendix E. 

The temperature rise may be determined either (1) by dividing the per 
cent increase of initial resistance by the temperature coefficient for the initial 
temperature expressed in per cent; or (2) by multiplying the increase in per 
cent of the initial resistance by T plus the initial temperature in degrees C, 
and then dividing the product by 100. (— T is the "inferred absolute zero 
temperature of resistance" and is given in the last column of the table in 
Appendix E. For average commercial annealed copper it is 233.8.) 

266. 3. Comparison of Methods. In electrical conductors, the rise of 
temperature should be determined by their increase of resistance where prac- 
ticable. Temperature elevations measured in this way are usually in excess of 
temperature elevations measured by thermometers. In very low-resistance 
circuits, thermometer measurements are frequently more reliable than measure- 
ments by the resistance method. Where a thermometer applied to a coil or 
winding indicates a higher temperature elevation than that shown by resistance 
measurement, the thermometer indication should be accepted. 

(B) Normal Conditions for Tests. 

267. 1. Duration of Tests. The temperature should be measured after 
a run of sufficient duration for the apparatus to reach a practically constant 
temperature. This is usually from 6 to 18 hours, according to the size and con- 
struction of the apparatus. It is permissible, however, to shorten the time of 
the test by running a lesser time on an overload in current and voltage, then 
reducing the load to normal, and maintaining it thus until the temperature 
has become constant. 

268. 2. Room Temperature. The rise of temperature should be referred 
to the standard condition of a room temperature of 25° C. 

269. Temperature Correction. If the room temperature during the 
test differs from 25° C, correction on account of difference in resistance should 
be made by changing the observed rise of temperature by one-half per cent 
for each degree Centigrade. Thus with a room temperature of 35° C, the 
observed rise of temperature has to be decreased by 5 per cent, and with a 
room temperature of 15° C, the observed rise of temperature has to be increased 
by 5 per cent. In certain cases, such as shunt-field circuits without rheostat, 
the current strength will be changed by a change of room temperature. The 
heat-production and dissipation may be thereby affected. Correction for 
this should be made by changing the observed rise in temperature in propor- 
tion as the PR loss in the resistance of the apparatus is altered owing to the 
difference in room temperature. 

270. 3. Barometric Pressure. Ventilation. A barometric pressure of 
760 mm. and normal conditions of ventilation should be considered as stand- 
ard, and the apparatus under test should neither be exposed to draught nor 
enclosed, except where expressly specified. The barometric pressure needs 
to be considered only when differing greatly from 760 mm. 

271. Barometric Pressure Correction. When the barometric pressure 

differs greatly from the standard pressure of 760 mm. of mercury, as at high 

altitudes, a correction should be applied. In the absence of more nearly 

accurate data, a correction of one per cent of the observed rise in temperature 

for each 10 mm. deviation from the 760-mm. standard is recommended. For 

example at a barometric pressure of 680 mm. the observed rise of temperature 

• * u ^i a u 760- 680 

is to be reduced by — = 8 per cent. 

(II) Limiting Temperature Rise. 

272. General. The temperature of electrical machinery under regular 
service conditions should never be allowed to remain at a point at which 
permanent deterioration of its insulating material takes place. 

273. Limits Recommended. It is recommended that the following maxi- 
mum values of temperature elevation, referred to a standard room tempera- 
ture of 25° C, at rated load under normal conditions of ventilation or cooling, 
should not be exceeded. 

(A) Machines in General. 

274. In commutating machines, rectifying machines, pulsating-current gen- 
erators, synchronous machines, synchronous commutating machines and 



520 STANDARDIZATION RULES. 

unipolar machines, the temperature rise in the parts specified should not 
exceed the following: 

275. Field and armature, 50° C. 

276. Commutator and brushes, by thermometer, 55° C. 

277. Collector rings, 65° C. 

278. Bearjngs and other parts of machine, by thermometer, 40° C. 

279. (B) Rotary Induction Apparatus. The temperature rise should 
not exceed the following: 

280. Electric circuits, 50° C, by resistance. 

281. Bearings and other parts of the machine, 40° C, by thermometer. 

282. In squirrel-cage or short-circuited armatures, 55° C., by thermometer, 
may be allowed. 

(C) Stationary Induction Apparatus. 

283. a. Transformers for Continuous Service. The temperature rise 
should not exceed 50° C. in electric circuits, by resistance; and in other parts, 
by thermometer. 

284. b. Transformers for Intermittent Service. In the case of trans- 
formers intended for intermittent service, or not operating continuously at 
rated load, but continuously in circuit, as in the ordinary case of lighting 
•transformers, the temperature elevation above the surrounding air-tempera- 
ture should not exceed 50° C, by resistance in electric circuits and by ther- 
mometer in other parts, after the period corresponding to the term of rated 
load. In this instance, the test load should not be applied until the trans- 
former has been in circuit for a sufficient time to attain the temperature 
elevation due to core loss. With transformers for commercial lighting, the 
duration of the rated-load test may be taken as three hours, unless otherwise 
specified. 

285. c. Reactors, Induction- and Magneto-Regulators. Electric cir- 
cuits by resistance and other parts by thermometer, 50° C. 

286. d. Large Apparatus. Large generators, motors, transformers, or 
other apparatus in which reliability and reserve overload capacity are import- 
ant, are frequently specified not to rise in temperature more than 40° C. under 
rated load and 55° C. at rated overload. It is, however, ordinarily undesirable 
to specify lower temperature elevations than 40° C. at rated load, measured as 
above. 

CD) Rheostats. 

287. In Rheostats, Heaters and other electrothermal apparatus, no com- 
bustible or inflammable part or material, or portion liable to come in contact 
with such material, should rise more than 50° C. above the surrounding air 
under the service conditions for which it is designed. 

288. a. Parts of Rheostats. Parts of rheostats and similar apparatus 
rising in temperature, under the specified service conditions, more than 50° C, 
should not contain any combustible material, and should be arranged or in- 
stalled in such a manner that neither they, nor the hot air issuing from them, 
can come in contact with combustible material. 

(E) Limits Recommended in Special Cases. 

289. a. Heat-Resisting Insulation. With apparatus in which the in- 
sulating materials have special heat-resisting qualities, a higher temperature 
elevation is permissible. 

290. b. High Air Temperature. In apparatus intended for service in 
places of abnormally high temperature, a lower temperature elevation should 
be specified. 

291. c. Apparatus Subject to Overload. In apparatus which by the 
nature of its service may be exposed to overload, or is to be used in very high 
voltage circuits, a smaller rise of temperature is desirable than in apparatus 
not liable to overloads or in low-voltage apparatus. In apparatus built for 
conditions of limited space, as railway motors, a higher rise of temperature 
must be allowed. 

292. d. Apparatus for Intermittent Service. In the case of apparatus 
intended for intermittent service, except railway motors, the temperature 
elevation which is attained at the end of the period corresponding to the term 
of rated load should not exceed the values specified for machines in general. 
In such apparatus, including railway motors, the temperature elevation should 
be measured after operation, under as nearly as possible the conditions of service 
for which the apparatus is intended, and the conditions of the test should be 
specified. 



VOLTAGES AND FREQUENCIES. 521 



H. OVERLOAD CAPACITIES. 

293. Performance with Overload. All apparatus should be able to carry 
the overload hereinafter specified without serious injury by heating, sparking, 
mechanical weakness, etc., and with an additional temperature rise not ex- 
ceeding 15° C, above those specified for rated loads, the overload being applied 
after the apparatus has acquired the temperature corresponding to rated-load 
continuous operation. Rheostats to which no temperature rise limits are 
attached are naturally exempt from this additional temperature rise of 15° C. 
under overload specified in these rules. 

294. Normal Conditions. Overload guarantees should refer to normal 
conditions of operation regarding speed, frequency, voltage, etc., and to non- 
inductive conditions in alternating apparatus, except where a phase dis- 
placement is inherent in the apparatus. 

295. Overload Capacities Recommended. The following overload ca- 
pacities are recommended: 

296. a. Generators. Direct-current generators and alternating-current 
generators, 25 per cent for two hours. 

297. b. Motors. Direct-current motors, induction motors and synchro- 
nous motors, not including railway and other motors intended for intermittent 
service, 25 per cent for two hours, and 50 per cent for one minute. 

298. c. Converters. Synchronous converters, 25 per cent for two hours, 
50 per cent for one-half hour. 

299. d. Transformers and Rectifiers. Constant-potential transformers 
and rectifiers, 25 per cent for two hours; except in transformers connected 
to apparatus for which a different overload is guaranteed, in which case the 
same guarantees shall apply for the transformers as for the apparatus con- 
nected thereto. 

300. e. Exciters. Exciters of alternators and other synchronous machines, 
10 per cent more overload than is required for the excitation of the synchro- 
nous machine at its guaranteed overload, and for the same period of time. 
All exciters of alternating-current, single-phase or polyphase generators, should 
be able to give at their rated speed, sufficient voltage and current to excite their 
alternators, at the rated speed, to the full-load terminal voltage, at the rated 
output in kilo volt-amperes and with 50 per cent power-factor. 

301. /. A Continuous-Service Rheostat, such as an armature- or field- 
regulating rheostat, should be capable of carrying without injury for two 
hours a current 25 per cent greater than that at which it is rated. It should 
also be capable of carrying for one minute a current 50 per cent greater than 
its rated-load current, without injury. This excess of capacity is intended for 
testing purposes only, and this margin of capacity should not be relied upon 
in the selection of the rheostat. 

302. g. An Intermittent Service or Motor-Starting Rheostat is used for 
starting a motor from rest and accelerating it to rated speed. Under ordinary 
conditions of service, and unless expressly stated otherwise, a motor is assumed 
to start in fifteen seconds and with 150 per cent of rated current strength^ A 
motor-starter should be capable of starting the motor under these conditions 
once every four minutes for one hour. 

303. (a) This test may be carried out either by starting the motor at four- 
minute intervals, or by placing the starter at normal temperature across the 
maximum voltage for which it is marked, and moving the lever uniformly and 
gradually from the first to the last position during a period of fifteen seconds, 
the current being maintained substantially constant at said 50 per cent excess, 
by introducing resistance in series or by other suitable means. 

304. (6) Other Rheostats for Intermittent-Service are employed under 
such special and varied conditions that no general rules are applicable to them. 



Ill, VOLTAGES A\I> lREUlEXHE«i. 

A. VOLTAGES. 

305. Direct-Current Generators. In direct-current, low-voltage gen- 
erators, the following average terminal voltages are in general use and are 
recommended : 

125 volts. 250 volts. 600 volts 



522 STANDARDIZATION RULES. 

306. Low-Voltage Circuits. In direct-current low-voltage circuits, the 
following terminal voltages are in general use and are recommended: 

115 volts. 230 volts. 550 volts. 

In alternating-current low-voltage circuits, the following terminal voltages 
are in general use and are recommended: 

110 volts. 220 volts. 440 volts. 550 volts. 

307. Primary Distribution Circuits. In alternating-current, constant- 
potential, primary-distribution circuits, an average voltage of 2,200 volts, 
with step-down transformer ratios $> and z Vi * s m general use, and is recom- 
mended. 

308. Transmission Circuits. In alternating-current constant-potential 
transmission circuits, the following impressed voltages are recommended: 

6,600 11,000 22,000 33,000 44,000 66,000 88,000 110,000 

309. Transformer Ratio. It is recommended that the standard trans- 
former ratios should be such as to transform between the standard voltages 
above named. The ratio will, therefore, usually be an exact multiple of 5 or 
10, e.g., 2,200 to 11,000; 2,200 to 44,000. 

310. Range in Voltage. In alternating-current generators, or generating 
systems, a range of terminal voltage should be provided from rated voltage 
at no load to 10 per cent in excess thereof, to cover drop in transmission. If 
a greater range than ten per cent is specified, the generator should be con- 
sidered as special. 

B. FREQUENCIES. 

311. In Alternating-Current Circuits, the following frequencies are stand- 
ard: 

25 cycles. 60 cycles. 

312. These frequencies are already in extensive use and it is deemed ad- 
visable to adhere to them as closely as possible. 

IV. ftJEXEIt AJL llECOnHEADATIO^I. 

313. Name Plates. All electrical apparatus should be provided with a 
name plate giving the manufacturers' name, the voltage and the current in 
amperes for which it is designed. Where practicable, the kilowatt capacity, 
character of current, speed, frequency, type, designation and serial number 
should be added. 

314. Diagrams of Connections. All electrical apparatus when leaving 
the factory should be accompanied by a diagram showing the electrical con- 
nections and the relation of the different parts in sufficient detail to give the 
necessary information for proper installation. 

315. Rheostat Data. Every rheostat should be clearly and permanently 
marked with the voltage and amperes, or range of amperes, for which it is 
designed. 

316. Colored Indicating Lights. When using colored indicating lights 
on switch-boards, red should denote danger, such as "switch closed" or "cir- 
cuit alive"; green should denote safety, such as "switch open" or "circuit 
dead." 

317. When white lights are used, a light turned on should denote danger, 
such as "switch closed" or "circuit alive": while the light out should denote 
safety, such as "switch open" or "circuit dead." Low-efficiency lamps 
should be used on account of their lesser liability to accidental burn-out. 

318. The use of colored lights is recommended, as safer than white lights. 

319. Grounding Metal Work. It is desirable that all metal work near 
high potential circuits be grounded. 

320. Circuit Opening Devices. The following definitions are recom- 
mended. 

321. a. A Circuit-Breaker is an apparatus for breaking a circuit at the 
highest current which it may be called upon to carry. 

322. b. A Disconnecting Switch is an apparatus designed to open a circuit 
only when carrying little or no current. 

323. c. An Automatic Circuit-Breaker is an apparatus for breaking a cir- 
cuit automatically under an excessive strength of current. It should be 
capable of breaking the circuit repeatedly at rated voltage and at the maxi- 
mum current which it may be called upon to carry. 



APPENDICES AND TABULAR DATA. 



523 



V. ArM3I!¥l>i:CJES AND TABILAH DATA. 



Unit. 



volt 

ampere 

ohm 



mho 



b, 


" 


c, 


watt 
farad 
henry- 
maxwell 


I, 


gauss 

gilbert per cm. 

cm. or inch 


t, 


gm. or lb. 
second or hour 



APPENDIX A. NOTATION. 

ilie following notation is recommended: 

Name of Quantity. Symbol. 
«24. Voltage, E.M.F., potential difference E, e. 

Current I, i, 

Resistance R, r, 

Reactance X, x, 

Impedance Z, z, 

Admittance Y, y, 

Conductance G, g, 

Susceptance B, 

Power P, 

Capacity C, 

Inductance C» 

Magnetic flux <p 

Magnetic density (g, 

Magnetic force H, 

Length L, 

Mass M, 

Time T, 

Em, Im and Bm should preferably be used for maximum cyclic values, e, % 
and p for instantaneous values, E and I for r.m.s. values (see Sec. 5g) and P 
for the average value or effective power. These distinctions are not necessary 
in dealing with continuous-current circuits. Vector quantities are preferably 
represented by bold face capitals. 

APPENDIX B. RAILWAY MOTORS. 

(I) Rating. 

325. Introductory Note on Rating. Railway motors usually operate 
in a service in which both the speed and the torque developed by the motor 
are varying almost continually. The average requirements, however, during 
successive hours in a given class of service are fairly uniform. On account 
of the wide variation of the instantaneous loads, it is impracticable to assign 
any simple and definite rating to a motor which will indicate accurately the 
absolute capacity of a given motor or the relative capacity of different motors 
under service conditions. It is also impracticable to select a motor for a 
particular service without much fuller data with regard both to the motor and 
to the service than is required, for example, in the case of stationary motors 
which run at constant speeds. 

326. Scope of Nominal Rating. It is common usage to give railway 
motors a nominal rating in horse power on the basis of a one-hour test. As 
above explained, a simple rating of this kind is not a proper measure of service 
capacity. This nominal rating, however, indicates approximately the maxi- 
mum output which the motor should ordinarily be called upon to develop 
during acceleration. Methods of determining the continuous capacity of a 
railway motor for service requirements are given under a subsequent heading. 

327. The Nominal Rating of a railway motor is the horse-power output at 
the car-axle, that is, including gear and other transmission losses, which gives 
a rise of temperature above the surrounding air (referred to a room tempera- 
ture of 25° C.) not exceeding 90° C. at the commutator and 75° C. at any other 
part after one hour's continuous run at its rated voltage (and frequency, in 
the case of an alternating-current motor) on a stand, with the motor-covers 
removed, and with natural ventilation. The rise in temperature is to be de- 
termined by thermometer, but the resistance of no electrical circuit in the 
motor shall increase more than 40 per cent during the test. 

(II) Selection of Motor for Specified Service. 

328. General Requirements. The suitability of a railway motor for a 
specified service depends upon the following considerations: 

329. a. Mechanical ability to develop the requisite torque and speeds as 
given by its speed-torque curve. 

330. b. Ability to commutate successfully the current demanded. 

331. c. Ability to operate in service without occasioning a temperature rise 
in any part which will endanger the life of the insulation. 

332. Operating Conditions, Typical Run. The operating conditions 



524 STANDARDIZATION RULES. 

which are important in the selection of a motor include the weight of load* the 
schedule speed, the distance between stops, the duration of stops, the rate of 
acceleration and of braking retardation, the grades and the curves; with these 
data at hand, the outputs which are required of the motor may h^ determined, 
provided the service requirements are within the limits of tne speed-torque 
curve of the motor. These outputs may be expressed in the form of curves 
giving the instantaneous values of current and of voltage which must be 
applied to the motor. Such curves may be laid out for the entire line, but 
they are usually constructed only for a certain average or typical run, which 
is fairly representative of the conditions of service. To determine whether the 
motor has sufficient capacity to perform the service safely, further tests or 
investigations must be made. 

333. Capacity Test of Railway Motor in Service. The capacity of a 
railway motor to deliver the necessary output may be determined by meas- 
urement of its temperature after it has reached a maximum in service. If a 
running test cannot be made under the actual conditions of service, an equiva- 
lent test may be made in a typical run back and forth, under such conditions 
of schedule speed, length of run, rate of acceleration, etc., that the test cycle 
of motor losses and conditions of ventilation are essentially the same as would 
be obtained in the specified service. 

334. Methods of Comparing Motor Capacity with Service Require- 
ments. Where it is not convenient to test motors under actual service con- 
ditions or in an equivalent typical run, recourse may be had to one of the two 
following methods of determining temperature rise now in general use: 

335. 1. Method by Losses and Thermal Capacity Curves. The heat 
developed in a railway motor is carried partly by conduction through the 
several parts and partly by convection through the air to the motor-frame 
whence it is distributed to the outside air. As the temperature of the several 
parts is thus dependent not only upon their own internal losses but also upon 
the temperature of neighboring parts, it becomes necessary to determine 
accurately the actual value and distribution of losses in a railway motor for a 
given service and reproduce them in an equivalent test-run. The results of a 
series of typical runs expressed in the form of thermal capacity curves will 
give the relation between degrees rise per watt loss in the armature and in the 
field for all ratios of losses between them met with in the commercial applica- 
tion of a given motor. 

336. This method consists, therefore, in calculating the several internal 
motor losses in a specified service and determining the temperature rise with 
these losses from thermal capacity curves giving the degrees rise per watt loss 
as obtained in experimental track tests made under the same conditions of 
ventilation. 

337. The following motor losses cause its heating and should be carefully 
determined for a given service: PR in the field; PR in the armature; PR in 
the brush contacts, core loss and brush friction. 

338. The loss in the bearings (in the case of geared motors) also adds some- 
what to the motor-heating, but owing to the variable nature of such losses 
they are generally neglected in making calculations. 

339. 2. Method by Continuous Capacity of Motor. The essential 
losses in the motor, as found in the typical run, are in most cases those in the 
motor windings and in the core. The mean service conditions may be expressed 
in terms of the current which would produce the same losses in the motor 
windings and the voltage which, with that current, would produce the same 
core losses as the average in service. The continuous capacity of the motor 
is given in terms of the amperes which it will carry when run on a testing stand 
— with covers on or off, as specified — at different voltages, say, 40, 60, 80 
and 100 per cent of the rated voltage — with a temperature rise not exceeding 
90° C. at the commutator and 75° C. at any other part, provided the resistance 
of no electric circuit in the motor increases more than 40 per cent. A com- 
parison of the equivalent service conditions with the continuous capacity of 
the motor will determine whether the service requirements are within the safe 
capacity of the motor. 

340. This method affords a ready means of determining whether a specified 
service is within the capacity of a given motor and it is also a convenient ap- 
proximate method for comparing the service capacities of different motors. 

APPENDIX C. PHOTOMETRY AND LAMPS. 

341. Candle-Power. The luminous intensity of sources of light is ex- 
pressed in candle-power, The unit of candle-power is the international candle 



APPENDICES AND TABULAR DATA. 525 

maintained by the Bureau of Standards at Washington, D. C. The Hefner 
unit is 0.90 of the international candle. 

342. Lumen. The total flux of light from a source is equal to its mean 
spherical intensity multiplied by 4 tv. The unit of flux is called the lumen. A 

lumen is the -r— th part of the total flux of light emitted by a source having 

47T 

a mean spherical intensity of one candle-power. 

344. Illumination. The fundamental physical unit of illumination is 
the centimeter-candle, or lumen per square centimeter of incident surface. 
This is a very intense illumination. It is, therefore, convenient to express 
illumination practically in thousandths of the fundamental unit; i.e., in milli- 
lumens per sq. cm. In English-speaking countries, the unit of illumination 
commonly employed is the foot-candle or lumen per square foot. A foot- 
candle is nearly the same illumination as a millilumen per sq. cm. and is actu- 
ally the more intense in the ratio 1.0764-, so that n foot-candles = 1.0764 X n 
millilumens per sq. cm. A meter candle, or lumen per square meter, is called 
a "lux." A foot-candle is 10.764 lux, and a millilumen per sq. cm. is exactly 
10 lux. 

346. The Efficiency of Electric Lamps is properly stated in terms of lumens 
per watt at lamp terminals. This use of the term efficiency is to be considered 
as special, and not to be confused with the generally accepted definition of 
efficiency in Sec. 84. 

347. a. Efficiency, Auxiliary Devices. In illuminants requiring aux- 
iliary power-consuming devices outside of the luminous body, such as steadying 
resistances in constant potential arc lamps, a distinction should be made be- 
tween the net efficiency and the gross efficiency of the lamp. This distinction 
should always be stated. The gross efficiency should include the power con- 
sumed in the auxiliary resistance, etc. The net efficiency should, however, 
include the power consumed in the controlling mechanism of the lamp itself. 
Comparison between such sources of light should be made on the basis of gross 
efficiency, since the power consumed in the auxiliary device is essential to the 
operation. 

348. A Standard Circuit Voltage of 110 volts, or a multiple thereof, may 
be assumed, except where expressly stated otherwise. 

340. Watts per Candle. The specific consumption of an electric lamp is 
its watt consumption per mean spherical candle-power. "Watts per candle" 
is the term used commercially in connection with incandescent lamps, and 
denotes watts per mean horizontal candle-power. 

350. Photometric Tests in which the results are stated in candle-power 
should be made at such a distance from the source of light that the latter may 
be regarded as practically a point. Where tests are made at shorter distances, 
as for example in the measurement of lamps with reflectors, the results should 
always be given as "apparent candle-power " at the distance employed, which 
distance should always be specifically stated. 

351. Basis for Comparison. Either the total flux of light in lumens, or 
the mean spherical candle-power, should always be used as the basis for com- 
paring various luminous sources with each other, unless there is a clear under- 
standing or statement to the contrary. 

352. Incandescent Lamps, Rating. It is customary to rate incandescent 
lamps on the basis of their mean horizontal candle-power; but in comparing 
incandescent lamps in which the relative distribution of luminous intensity 
differs, the comparison should be based on their total flux of light measured in 
lumens, or on their mean spherical candle-power. 

352a. Life Tests. Similar filaments may be assumed to operate at the 
same temperature only when their lumens per watt consumed are the same. 
Life tests are comparable only when conducted under similar conditions as to 
filament temperatures. 

353. The Spherical Reduction-Factor of a lamp 

mean spherical candle-power 



mean horizontal candle-power 



354. The Total Flux of light in lumens emitted by a lamp = 4 t X mean 
horizontal candle-power X spherical reduction-factor. 

355. The Spherical Reduction-Factor should only be used when properly 
determined for the particular type and characteristics of each lamp. The 
spherical reduction-factor permits of substantially accurate comparisons being 
made between the total lumens, or mean spherical candle-powers of different 



526 



STANDARDIZATION RULES. 



types of incandescent lamps, and may be used in the absence of proper facili- 
ties for direct measurement of the total lumens, or mean spherical candle-power. 

356. "Reading Distance." Where standard photometric measurements 
are impracticable, approximate measurements of iiluminants such as street 
lamps, may be made by comparing their "reading distances"; i.e., by deter- 
mining alternately the distances at which an ordinary size of reading print can 
just be read, by the same person or persons, when all other light is screened. 
The angle below the horizontal at which the measurement is made should be 
specified when it exceeds 15°. Reading distance methods usually involve the 
comparison of very faint illuminations and hence the results may be seriously 
affected by the Purkinje effect. 

357. In Comparing Different Luminous Sources not only should their candle- 
power be compared, but also their relative form, brightness, distribution of 
illumination and character of light. 

357a. The following symbols are recommended in connection with photom- 
etry: 

Symbol. 
I 
F 
E 
R 
b 
Q 
L 



Photometric magnitude. 
Intensity of light. 
Luminous flux. 
Illumination. 
Specific radiation. 
Brightness. 
Quantity. 
Lighting. 



Unit. 
International candle. 
Lumen. 

Lumen /cm. 2 , foot-candle. 
Foot-candle. 
Candle /cm. 2 
Candle. 
Lumen-second, lumen-hour. 



APPENDIX D. SPARKING DISTANCES. 

358. Table of Sparking Distances in Air between Opposed Sharp Needle- 
Points, for Various Root-Mean-Square Sinusoidal Voltages, in inches and in 
centimeters. The table applies to the conditions specified in Sees. 240-246. 

359. 



Kilovolts Distance. 

R.M.S. Inches. Cm. 

5 0.225 0.57 

10 0.47 1.19 

15 0.725 1.84 

20 1.0 2.54 

25 1.3 

30 1.625 



35. 
40. 
45. 
50. 
60. 
70. 
80. 
90. 
100. 



2.0 
2.45 



8.35 

9.6 

110 10.75 

120 11.85 

130 12.90 



3.3 

4.1 

5.1 

6.2 

7.5 

9.0 

11.8 

14.9 

18.0 

21.2 

24.4 

27.3 

30.1 

32.8 



Kilovolts Distance. 

R.M.S. Inches. Cm. 

140 13.95 35.4 

150 15.0 38.1 

160 16.05 40.7 

170 17.10 43.4 

180 18.15 46.1 

190 19.20 48.8 

200 20.25 51.4 

210 21.30 54.1 

220 22.35 56.8 

230 23.40 59.4 

240 24.45 62.1 

250 25.50 64.7 

260 26.50 67.3 

270 27.50 69.8 

280 28.50 72.4 

290 29.50 74.9 

300 30.50 77.4 



APPENDIX E. TEMPERATURE COEFFICIENT OF COPPER. 

360. The fundamental relation between the rise of temperature and the 
increase of resistance of copper may be expressed thus: 

R t =R tl {\ +a tl [t -*,]), 

where Rt is the resistance at any temperature t° C; Rti is the resistance at any 
"initial temperature" (or "temperature of reference") ti° C; and a tl is the 
temperature coefficient from and at the initial temperature t^C. Obviously 
the temperature coefficient is different for different initial temperatures, and 
this variation is shown in the horizontal rows of the table below. Further- 
more, it has been shown that the temperature coefficient is different for dif- 
ferent conductivities, and that the temperature coefficient is substantially 
proportional to the conductivity. The results of this simple law are shown 
by the vertical columns of the table below. 



APPENDICES AND TABULAR DATA. 



527 



TEMPERATURE COEFFICIENTS OF COPPER FOR DIFFERENT 

INITIAL TEMPERATURES AND DIFFERENT 

CONDUCTIVITIES. 



















-T 


Ohms per 


Per 














"In- 


meter- 


cent 














ferred 


gram at 


conduc- 


«o 


<*15 


«20 


"25 


«30 


«60 


abso- 


20° C. 


tivity. 














lute 
zero." 


0.16108 


95 


0.00405 


0.00381 


0.00374 


0.00367 


0.00361 


0.00336 


-247.2 


0.15940 


96 


0.00409 


0.00386 


0.00378 


0.00371 


0.00364 


0.00340 


-244.4 


0.15776 


97 


0.00414 


0.00390 


0.00382 


0.00375 


0.00368 


0.00343 


-241.7 


0.15727 


97.3 


0.00415 


0.00391 


0.00383 


0.00376 


0.00369 


0.00344 


-240.9 


0.15614 


98 


0.00418 


0.00394 


0.00386 


0.00379 


0.00372 


0.00346 


-239.0 


0.15457 


99 


0.00423 


0.00398 


0.00390 


0.00383 


0.00375 


0.00349 


-236.4 


0.153022 


100 
101 


0.00428 
0.00432 


0.00402 
0.00406 


0.00394 


0.00386 
0.00390 


0.00379 
0.00383 


0.00352 
0.00355 


-233.8 


0.15151 


0.00398 


-231.3 



The quantity ( — T) given in the last column of the above table is the cal- 
culated temperature on the centigrade scale at which copper of the particular 
conductivity concerned would have zero electrical resistance provided the 
temperature coefficient between 0° C. and 100° C. applied continuously down 
to the absolute zero. The usefulness of this "inferred absolute zero tempera- 
ture of resistance" in calculating temperature rise is evident from the following 
formula : 

The presentation of the above table is intended to emphasize the desir- 
ability of determining the temperature coefficient rather than assuming it. 
Actual experimental determination is facilitated by the proportional relation 
between the temperature coefficient and the conductivity; a measurement of 
either quantity gives both. However, if a temperature coefficient must be 
assumed, the best value to take for average commercial annealed copper wire 
is that given in the table for 100 per cent conductivity, viz., 
a Q = 0.00428, a 20 = 0.00394, a 25 = 0.00386. 

This is the value recommended for wire wound on instruments and machines, 
since they are generally wound with annealed wire and experiments have 
shown that the distortions due to the winding of the wire do not appreciably 
affect the temperature coefficient. 

If a value must be assumed for hard-drawn copper wire, the value recom- 
mended is that given in the table for 97.3 per cent conductivity, viz., 
a = 0.00415, a 2 o = 0.00383, a 25 = 0.00376. 

The temperature coefficients in Fahrenheit degrees are given by dividing 
any a above by 1.8. Thus, the 20° C. or 68° F. temperature coefficient for 
copper of 100 per cent conductivity is 0.00394 per degree C, or 0.00219 per 
degree F. 

APPENDIX F. HORSE POWER. 

361. In view of the fact that a horse power defined as 550 foot-pounds per 
second represents a power which varies slightly with the latitude and altitude 
(from 743.3 to 747.6 watts) and ateo in view of the fact that different authori- 
ties differ as to the precise value of the horse power in watts, the Standards 
Committee has adopted 746 watts as the value of the horse power. The number 
of foot-pounds per second to be taken as one horse power is therefore such a 
value at any given place as is equivalent to 746 watts; the number varies 
from 552 to 549 foot-pounds per second, being 550 at 50° latitude (London), 
and 550.5 at Washington. The Standards Committee, however, recommends 
that the kilowatt instead of the horse power be used generally as the unit of 
power. 



ELECTRIC LIGHTING:. 

Revised by Dr. C. H. Sharp. 

Velocity of light 300,000 kilometers per second, or 186,000 miles per 
second. 

Composition of Sunlight. 

Violet produces the maximum chemical effect. 

Indigo. Blue. Green. 

Yellow, the maximum light effect. 

Orange. 

Red produces the maximum heat effect. 

The most luminous part of the spectrum is the yellowish green. 
Colors. 

Primary. Red. Yellow. Blue. 

Secondary. Orange. Purple. Green. 

Laws of Radiation of a Black Body. 

Stefan-Boltzmann law. The total energy radiated by a black body is 
proportional to the fourth power of its absolute temperature. 

£ = ad*. 

Wien's displacement law. The product of the wave-length of the max- 
imum of radiation and the absolute temperature of the radiating body is a 
constant. 

Am0= const. = A. 

The quotient of the maximum radiation by the fifth power of the abso- 
lute temperature is a constant. 

# w 0-5 = const. = B. 

Applying these laws the temperature of radiating bodies can be deter- 
mined with a degree of accuracy which depends chiefly on the degree to 
which the body approaches a black body in its characteristics. Lumraer 
and Pringsheim have found that for polished platinum Am0 = 2630, while 
for a black body Am0 = 2940. Hence the temperatures of other radiating 
bodies such as carbon must lie between the limits set by the two equations 

2630 . a 2940 
= -7 — and 6 = — : 

Am Am 

The Intensity of a Source of light is measured by comparison with 
a source of unit intensity. The unit of luminous intensity commonly 
employed is the candle-power. 

Intensity of Illumination produced on a surface by a source 
of light concentrated at a point is inversely as the square of the distance 
between the surface and the source of light, 

, ... Intensity of source w 
Intensity of illumination = -tt— ^ X cos i, 

where i is the angle of incidence of the rays. 

Units of illumination are the foot-candle and the meter-candle or candle 
lumen (A. I. E. E.) The foot-candle is the illumination produced on the 
surface one foot distant by a source of one candle-power, the rays falling 
uormally on the surface. 

£28 



LIGHT. 



529 



The meter-candle or candle lumen is similarly denned, the meter being 
substituted for the foot. 

The unit of luminous flux is defined as follows : A unit flux is that flux 
sent by a source of unit intensity (candle-power) through a unit solid angle. 
This unit is called the lumen or candle lumen (standardization rules of 
A. I. E. E.) From a source of 1 c.p. the total flux is 4 n lumens. The 
symbol for flux is <f>. 

Flux and intensity of illumination are connected by the following relation: 



Illumination ■ 



Flux 
Surface 



or E 



Mean horizontal intensity is the average intensity in all directions in the 
horizontal plane passing through the source. In case of an incandescent 
lamp this plane is taken perpendicular to the axis of the lamp. 

Mean spherical candle-power is the average candle-power in all directions 
in space. It bears the following relation to the total luminous flux from 
the source, 



Mean hemispherical candle-power is defined as the average candle-power 
in all directions in a hemisphere having the source of light at its center. 

The spherical reduction factor is the ratio of the mean spherical candle* 
power to the mean horizontal candle-power. 

Trotter gives in the following table the intrinsic brightness of different 
sources of light. 

Intrinsic Brightness of Different Sources of JLig-lit. 

(Trotter.) 



Platinum (Violle standard) . . . 

Sun's disk 

Sky, near sun 

Albo carbon on edge 

White paper, horizontal, exposed to 
summer sky, noon ....... 

White paper, sun 60° high, paper fac- 
ing sun 

Albo carbon, flat 

Argand 

Black velvet, summer sky, noon . . 

White paper, reading without strain- 
ing 



C.P. per Sq. In. 



Red. Green. 



120 

487,000 
120 
73.5 

16.5 

8.25 
10.5 
6.8 
0.0333 

0.0018 



120 
1,000,000 
120 
60.7 

35.2 

17.2 
8.7 
5.29 
0.07 

0.0024 



C.P. per Sq. Cm. 



Red. 



18.5 
75.500 
18.5 
11.4 

2.56 

1.28 
1.63 
1.05 
0.0052 

0.00028 



Green. 



18.5 
155,000 
18.5 
9.4 

5.45 

2.67 
1.35 
0.82 
0.0109 

0.00037 



Sperm candle 

Moon, 35° above horizon 

Moon, high 

Batswing (whole flame) 

Methven standard 

Incandescent carbon filament (glow lamp) 
Crater of electric arc 



White. 



I 



White. 



2 
2 
3 

2.26 
4.3 
120 
45,000 



0.31 
0.31 
0.46 
0.35 
0.666 
18.5 
7,000 



530 



ELECTRIC LIGHTING. 



Units and Standards of I.ig-bt. 

The Intensity of a Source of tig-lit is expressed in terms of 
that of some specified unit or standard of reference. 

No very satisfactory standard for all purposes has as yet been produced, 
but those listed below are among the best in use or proposed. 

a. The British standard candle, a spermaceti candle seven-eighths of an 
inch in diameter, weighing one-sixth pound, and burning at the rate of 120 
grains per hour. In case the rate of burning of the candle does not 
equal 120 grains per hour but falls within the limits of 114 to 126 grains 
per hour, the value of the light is to be determined by simple proportion 
assuming that the intensity of the candle light varies in proportion to the 
rate of consumption of sperm. This standard, in spite of many defects, 
is still in extensive use and is legalized in many states. It nominally 
furnishes the unit of measurement in this country. 

b. Harcourt 10 candle pentane standard. This lamp, which is one of 

the best of modern standards, is shown in Figs. 
1 and 2 in the form in which it is constructed by 
the American Meter Co. Its fuel is a gas com- 
posed of a mixture of pentane vapor and air. 
The pentane is a light distillate of petroleum 
passing over at a temperature between 25° and 
40° C. The pentane is contained in the vapor- 
izer at the top of the lamp, from which it flows 
by its own weight down through the small tube 
to the base of an Argand burner, where it forms 
a flame inside a metal chimney. The base of 
the chimney is adjusted accurately to a height 
of 47 mm. above the top of the burner, and it 
is only the portion of the flame which comes be- 
tween the burner and the base of the chimney 
which falls on the photometer. All the light 
from the ragged upper portions of the flame is 
cut off. The flame is adjusted to a definite 
height by observing it through a mica window 
in the chimney. The exposed portion of the 
flame is protected from draughts by a conical 
shield open on one side. The lamp should be 
used in a well-ventilated room free from avoid- 
able draughts. According to Paterson of the 
National Physical Laboratory the candle-power 
of the lamp is expressed by the equation: 

c.p. = 10 + 0.066 (10 - c) - 0.008 (760 - 6), 

in which € is the number of liters of moisture 
per cubic meter of dry air, and b is the baro- 
metric height in millimeters. The quantity € is 




IP found from the equation c = 



X 1000, 



b — e — ei 
in which e equals the vapor pressure of the 
water and ei the vapor pressure of the CO2 pres- 
ent. The constant 10 represents the average 
hygrometric condition in London for a period 
of three years. 
. , the principal French standard, burns 42 grams 
of purified colza oil per hour, the flame being 40 mm. high. MM. Regnault 
and Dumas have proven by experiments that when the consumption of 
colza is at a rate between 40 and 44 grams per hour, the light emitted by 
this standard is proportional to the weight of colza burned. Following is 
a table showing the proper dimensions of this standard. 



Fig. 1. 

The Carcel lamp, 



LIGHT. 



531 




PENTANE10 C. P. LAMP 

HARCOURT TYPE 



Fig. 2. 



532 



ELECTRIC LIGHTING. 



Dimensions of Carcel Lamp. 



External diameter of burner 

Interior diameter of inner air current . . . 
Interior diameter of outer air current . . . 

Total height of chimney 

Distance from elbow to base of glass . . . 
Exterior diameter at level of bend .... 
Interior diameter of glass at top of chimney 
Mean thickness of glass 



23.5 
17.0 
45.5 
290 
61 
47 
34 
2 



Use lighthouse wick weighing 3.6 grams per decimeter and woven with 
75 strands. This standard is quite satisfactory if carefully used. 

d. The platinum standard proposed by Violle is the light emitted by one 
square centimeter of platinum at its melting-point. Violle shows that the 
light emitted by this unit is equivalent to 19 1 to 19f British candles. This 
standard has never been reduced to practice. The French bougie d^cimale 
is supposed to equal the 20th part of the Violle platinum unit. 

e. Hefner Amyl Lamp. The legal standard in Germany is the so-called 
Hefner unit, which is the light given by the Hefner- Alteneck amylacetate 
lamp. This lamp has been exhaustively investigated by the Reichsanstalt, 
which certifies to the accuracy of lamps submitted to it ; its intensity is about 
10 per cent less than that of the English candle, and its normal flame is 40 
millimeters high. It is very uniform and reproducible, and owing to the 
fact that lamps of certified value can be so readily obtained it is widely used, 
not only in Germany, but elsewhere. Careful instructions are issued with 
each lamp, and when used in accordance with these instructions the errors of 
measurement are not more than half those met with in the use of standard 
candles. The color is somewhat against this unit, being a distinctly reddish 
orange, which is a rather serious objection when used as a working standard 
in measurements of Welsbach burners or incandescent and Nernst lamps. 
Even with its faults though, it is probably the best primary standard that 
we have, as it can be reproduced accurately to a most unusual degree. 

This lamp has of late come into very general use as a reliable, moderate- 
priced and easily reproducible standard. It has been recommended by 
the American Institute of Electrical Engi- 
neers and the German Reichsanstalt. 

A cylindrical base contains the amyl acetate, 
which is drawn up through a wick tube of Ger- 
man silver in a specially prepared wick. The 
height of this German silver tube and the 
height of the flame are of vital importance. 
To secure the proper adjustment at the time 
the lamp is used, an optical flame gauge is 
provided, consisting of a small camera with 
lens, and ground glass plate. On this ground 
glass plate a horizontal line determines exactly 
the point at which the top of the flame should 
be kept. An error of 0.2 of a millimeter in 
the height of the flame produces an error of 
i of 1 per cent in the candle-power, so their 
setting must be made closely. 

In using this lamp special care should be 
taken that fresh air in abundance is supplied, 
but the room must be perfectly free from 
draughts or air currents, and it should be 
watched by a person at a distance from it. 
If the flame does not burn steadily the wick 
should be carefully trimmed, making itsome- 
what crowned. Never char the wick by 
burning it too high; after continued use it 
should appear to be only slightly browned. 




Fig. 3> 



LIGHT. 



533 



With a little experience it will be found that the flame can be kept accur- 
ately on the line of the optical flame gauge and quite steady. The variations 
of temperature, humidity and barometer height affect the candle-power of the 




20 30 40 50 60 70 80 90 

CHANGE IN INTENSITY FROM HUMIDITY 

AT DIFFERENT TEMPERATURES 



Fig. 4. 



lamp to a certain extent, but these fluctuations have been investigated fully, 
and corrections are given in the accompanying diagrams (Figs. 4 and 5). 



+5 



TJ 
















JO 

o 

z 
















o 

I 
> 
















m / 




BAROI 


rfETER 


HEIGH 


r MMS 







500 550 600 650 700 750 800 850 900 
CHANGE IN INTENSITY WITH BAROMETER HEIGHT 



Fig. 5. 



Incandescent Lamp* as Secondary Standards. Carbon fila- 
ment lamps which have been seasoned by burning them a few hours until 
their initial period of rise of candle-power at constant voltage has been 
passed, furnish secondary standards of light of remarkable constancy. It 
should be understood, however, that no single lamp can be relied on abso- 
lutely, but rather the average value given by a group of such lamps. The uni- 
formity of results which is obtained in the photometry of incandescent lamps 
in present practice in this country is due in no small measure to the fact that 
incandescent lamp standards, practically all of which emanate from the same 
laboratory, are in nearly universal use. These sub-standards have been 
standardized not by direct reference to a primary standard, none of which 
is entirely constant, but by reference to a series of incandescent lamp secon- 
dary standards, whereby a constant value for the unit is obtained. An 
invariable unit of luminous intensity has been maintained by such a series 
of lamps by the Electrical Testing Laboratories in New York for upwards 
of ten years. The standardization value for these lamps was derived from 
a similar series in the possession of the Edison Lamp Works, which were 
in turn standardized originally by reference to lamps standardized in the 
Reichsanstalt. The basis of this original standardization was the assump- 
tion that the Hefner unit equals 0.88 candle-power. This ratio has since 
received the sanction of the A. I. E. E., and more recently the Bureau of 
Standards in Washington has established its unit of luminous intensity 



534 



ELECTRIC LIGHTING. 



on the same basis. Thus it has come about that photometric measure- 
ments in this country which are nominally based on the British candle as 
a unit are actually, as far as electrical measurements are concerned, based 
on an invariable unit representing one of the values which the variable 
candle may assume, which is maintained by standardized incandescent 
lamps, and which is reproducible only through the intermediary of the 
Hefner standard lamp. Standardized lamps are furnished by the Elec- 
trical Testing Laboratories in New York of any required candle-power and 
voltage and for use either stationary or rotating. A special type of lamp 
has been developed for use in making stationary standards. These lamps 
have two horse-shoe shaped filaments in the same plane, one inside the 
other. The standard direction in these lamps is at right angles to the 
plane of the filaments, as indicated by vertical lines etched in the glass. 
Lamps are also standardized and certified by the Bureau of Standards. 

On account of the adoption of the Harcourt 10 candle pentane lamp 
as the official standard by the Metropolitan Board of Gas Referees of London 
and the introduction of this standard into practice in this country, chiefly 
in the photometry of illuminating gas, a discrepancy has arisen between 
the candle of the electric industry and the candle of the gas industry. 
Recent international determinations of the ratio between the Hefner unit 
and the pentane unit have shown that the Hefner equals 0.915 candle-power, 
the candle being defined as the one-tenth part of the intensity of the 
pentane unit. As has been said, the value of the Hefner in terms of the 
candle of the electrical industry and of the Bureau of Standards is 0.88. 
The matter of this discrepancy is now (Dec, 1907) under advisement by 
a joint committee of the Illuminating Engineering Society, the American 
Institute of Electrical Engineers, and the American Gas Institute. 

The following is a table giving the values of the various standards and 
units in terms of each other. This table is compiled from the most recent 
data on the subject. 



Hefner unit 

10 c.p. pentane . . . 

Carcel 

Bougie de*cimale . . . 

Candle unit. U. S. A. 

Unit National Physical Lab- 
oratory. London 

Unit Laboratoire Central 
d'El£ctricite\ Paris 




PHOTOMETERS. 

A photometer is an apparatus for measuring the intensity of a source of 
light or of an illumination in terms of a standard. Incase the apparatus 
is intended for the latter purpose only, it is sometimes called an ' illumi- 
nometer. " All photometric measurements are made by a visual compar- 
ison of the source to be measured with some standard. The eye cannot 
tell us how many times brighter one light is than another. It can say 
only that one illuminated field is just as bright as another. A photometer 
consists, then, of two essential parts: first, an arrangement whereby two 
fields are obtained in juxtaposition to each other, one of them being illumi- 



PHOTOMETERS. 



535 



nated by the standard light, and the other by the light which is to be measured ; 
second, of an arrangement whereby the brightness of one or both the fields 
can be varied continuously according to a known law, from which the rela- 
tive intensities of the sources can be computed as soon as the conditions 
have been discovered under which the fields are equal in illumination. In 
an illuminometer a further part must be provided; namely, a standard 
plate for the reception of the illumination which is to be measured. 

The law of variation which is most commonly employed is that which 
states that illumination from a punctiform source of light varies inversely 
as the square of the distance to the source. A common form of photometer 
is as shown in Fig. 6. The light to be measured and the standard light 
are set up at opposite ends of a bar on which the sight-box containing a 
photometric screen or disk for testing the equality of illumination can be 
moved. When a setting has been made, the intensities of the two sources 




Fig. 6. Photometer, Queen & Co. 



of light are directly proportional to the squares of their respective distances 
from the photometric screen in the sight-box. 

The forms of sight-box which are most commonly employed are the 
Bunsen and the Lummer-Brodhun. The latter is unexcelled by any other 
photometric device when the lights to be compared are of the same color. 
When color differences are present, the Bunsen is to be recommended, 
especially so when it is equipped with the Leeson star disk. 

In Hansen's photometer a piece of white paper — certain kinds of draught- 
ing paper are good — with a grease spot in its center is placed between the 
two lights with its surface at right angles to the rays. Behind the paper 
in the sight-box are placed two mirrors at an angle of about 140 degrees 
with each other so that both sides of the disk can be viewed simultaneously. 
The box is moved along the bar between the lights until the grease spot is 
seen with equal distinctness on both sides. This indicates an equality of 
illumination, and the general law given above is used to compute the relative 
intensities of the lights. The Leeson star disk is in some respects superior 
to the grease spot disk, and is made as follows : A star-shaped figure is cut 
out of a piece of moderately heavy paper, and the latter is pressed between 
two pieces of tissue paper of the proper degree of transparency. The out- 
Bide pieces may be pasted fast to the middle piece. 



536 



ELECTRIC LIGHTING. 



In the Lummer-Brodhnn photo- 
meter, diagram and cut of the carriage 
of which are shown below, the rays of 
light from the two sources under com- 
parison enter at the sides so as to strike 
the surfaces of the opaque gypsum screen. 
Diffused light from these white surfaces 
reaches two parallel mirrors (inside) at 
an angle of 45°, and is reflected to right- 
angled prisms which have the outer 
portions of their hypothenuse surfaces 
cut away and coated with asphalt varnish 
to secure complete absorption. Light 
entering the prisms from the mirrors is 
Fig. 7. Diagram of Lummer- either transmitted or totally reflected at 
Brodhun Photometer. their surface of contact, so that an ob- 

server at the telescope tube sees a circu- 
lar disk of light from one side of the gypsum screen surrounded by an an- 
nular ring of light from the other side, the boundary line between the 
two being sharply defined. 








Fig. 8. Lummer-Brodhun Photometer Carriage. 



Romford's photometer compares the shadows of an opaque rod thrown 
on a white screen by two lights. 

When the shadows are of equal density, 



H 






In Ritchie's photometer two equal white surfaces are placed at an 
angle with each other, and with the line of light and their brightness com- 
pared, moving back and forth on the line of light until both surfaces are 
alike in illumination ; the relative intensities of the lights are then the same 
as with the Bunsen instrument. 

In Joly's photometer, two slabs of paraffin wax, or translucent glass 
about 3" X 2" X V, are fastened together back to back by Canada balsam, 
a sheet of paper or silver foil being first interposed, after which the edges 
and surfaces are ground smooth. 

This slab is placed between the two lights, with the plane of the joint at 
right angles to the line between the lights, and moved back and forth on 
that line until the observer looking at the edge of the slab finds both sides 
equally illuminated, when the relative intensities are as before. By revers- 
ing the slab, a check can be had on the observation. 



PHOTOMETERS. 537 

* The Test Mate. — Preston S. Millar. In general work the intensity 
of the light incident upon a given surface is the only quantity which it is 
practicable or even desirable to measure. This is not proportional neces- 
sarily to the illuminating effect, which varies as well with the point from 
which the surface is viewed, with the color of the light and with the color 
and character of the surface. 

The criterion by which the light intensity is judged must be strictly 
proportional to the light incident upon the test plate, and must be inde- 
pendent of each of the other improper variables just mentioned, if the 
results of the observation are to show the intensity of the light incident upon 
the surface. 

Whether or not the light falling upon the photometric device varies only 
with that incident upon the test plate, depends upon the design and loca- 
tion of that plate. 

The requirements for a theoretically correct test plate are: 

First, a plain white surface which, when viewed from the point of photo- 
metric observation, obeys Lambert's law of the cosines with reference to 
intensity of illumination produced by light incident upon its surface at any 
inclination and from any direction. 

Second, a material which will not introduce errors due to color differences. 

Third, a plate which may be placed at any angle. 

Fourth, a location such that neither the body of the observer nor instru- 
ment parts shall obstruct light which would otherwise fall upon the plate. 

It is, of course, desirable to measure all of the light which would be inci- 
dent upon an object at the point to be considered. In all interior lighting 
systems there is more or less diffused light, all of which has some illuminat- 
ing value. In order to measure all of the effective light, there must be no 
objective interference with light incident upon the plate at any angle. 
This means that all instrument parts, as well as the observer, must be 
beneath or behind the surface of the test plate. This is possible only when 
transmitted light, instead of reflected light, is measured. 

The only color which is practicable is white, of as great purity as may 
be obtainable, and as free as possible from selective absorption. With such 
a test plate, lights of different colors are credited with approximately their 
true intensities, when the test plate is viewed from the photometric device. 

Prof. Ii. Wefoer has invented a photometer, as follows: 

The apparatus consists of a tube, A, about 30 cm. long, which can be 
moved up and down and swung in a horizontal plane on the upright, c. 
The standard light, S, a benzine lamp, is contained in a lantern fastened to 
the right end of the tube, A . Within the tube, A , a circular plate of opal 
glass can be moved from or towards the light, S; its distance from E is 
read in centimeters on the scale, s, by means of an index fastened to the 
pinion, P. At right angles to tube, A, a second tube, B, is fastened. This 
tube can be rotated in a vertical plane, and its position in reference to the 
horizontal is read on the graduated circle, C, A Lummer-Brodhun prism 
contained in tube B in its axis of rotation receives light from the opal glass 
plate in tube A, and reflects this light towards the eye-piece, O, so that the 
outer half of the field of vision is illuminated by this light; the inner half is 
illuminated by the light entering the tube, B, through g. 

In making measurements, the tube B is pointed toward the source of 
light to be measured. The light has to pass through a square box, g, in 
which may be inserted one or more opal glass plates, in order to diminish 
the intensity of the light, and thus to make it comparable with the standard 
light. The apparatus permits the measurement of light in the shape of a 
flame, as well as the measurement of diffused light. 

Since the measurement of diffused light interests us most at present, a 
short description of the method will not be out of place. 

A white screen, the surface of which is absolutely without luster, fur- 
nished as part of the apparatus, is placed in a convenient position, either 
horizontal or vertical, or at any desired inclination, toward the source of 
light. 

The photometer having been located at a convenient distance from the 
screen, the tube B is pointed to the center of the screen. The distance of 
the photometer from the screen can be varied within very wide limits, the 
only restrictions being that the field of vision receives no other light than 

* Trans. Illuminating Engineering Society, October, 1907. 



538 



ELECTRIC LIGHTING. 



that emanating from the screen. The necessary precautions for adjustment 
having been observed, the opal glass plate in the tube A is moved until both 
halves of the field of vision appear equally illuminated. The distance, r, of 
this glass plate from the standard light at the moment of equal illumina- 




Fig. 9. Prof. L. Weber's Portable Photometer 

R=10,00OMM /^ 




Fig. 10. 



tion is read on the scale on tube A in millimeters, and the intensity of illu- 
mination on the white screen is calculated from the formula, 

1O000 , 
r* 



/- 



-K. 



PHOTOMETERS. 



539 



The constant K is previously determined as follows: 

A standard candle or its equivalent is placed exactly one meter distant 
from the white screen, and the tube, B, of the photometer is pointed towards 
the screen, so that the center of the screen, which is marked by a cross, 
is seen in the center of the field of vision. As indicated in Fig. 6, the photo- 
meter must be so placed that the eye, looking through the eye-piece, sees 
nothing but the white screen. The angle of inclination under which the 
screen is observed may be varied within wide limits without influencing 
the result; it should, however, not exceed 60 degrees from the normal to 
the screen. 

Equal illumination of both halves of the field of vision having been ob- 
tained by means of adjusting the opal glass plate in tube A, the constant, 
fiC, is found by calculation: 

r 2 
K = R^ 

Since r is read in millimeters, and R is made 1 meter or 1000 millimeters, 
1000 instead of 1 must be taken in the formula for calculating the intensity 
of illuminating in meter-candles. 

A second method permits of measurements of diffused light without the 
intervention of a screen; but for further details the reader is referred .to the 
description of the apparatus by Professor Weber, Elektrotechnische Zeit- 
schrift, vol. v., p. 166. 

The whole apparatus can easily be taken apart, and packed in a box 
about 24 X 8 X 12 in hes. In some cases the benzine lamp might well be 
replaced by a small incandescent lamp, provided this lamp is standardized 
before and after each set of experiments. Such miniature lamps have been 
Found very convenient, and quite sufficiently constant in candle-power for 
several hundred observations. 

Sharp-Millar Universal Portable Photometer. —This instru- 
ment is designed for making all the various measurements of candle-power 




Fig. 11. 



and illumination which the Weber is fitted for, while it is more portable, 
convenient, and accurate than the latter instrument, and less complicated 
and expensive. The instrument is illustrated in Fig. 11.* 

Integrating- Photometers. — Photometers can be constructed, so 
that they will measure directly the mean spherical candle-power of lamps. 
Such photometers have been designed by Professor Matthews both for arc 
and incandescent lamps. (Trans. A. I. E. E.) 

* See Electrical World, LI. p. 181, Jan. 25, *08. Electrical Review, LII. 
p. 141, Jan. 25, '08. Electrician (London), LX. p. 562, Jan. 24, '08. 



540 ELECTRIC LIGHTING. 

A simple form of this type of photometer is the Ulbricht sphere photo- 
meter. This consists of a large sphere coated on the inside with dull white 
paint and furnished with a small window of diffusing glass. The lamp 
is introduced into the interior and a screen is so placed that the direct rays 
of the lamp cannot fall on the window, which is consequently illuminated 
by reflected rays alone. The theory shows that the intensity of such illu- 
mination is proportional to the total luminous flux, or the mean spherical 
candle-power of the source within, so that it is necessary only to photo- 
meter the light issuing from the window to have a measure of these quan- 
tities. The sphere must be calibrated by the "substitution method," 
using an incandescent lamp standardized for mean spherical candle-power. 

Rating* of Illuminants. — Illuminants are rated according to their 
candle-power and their volts, amperes or watts. Differences occur in 
practice as to what is meant by the candle-power, that is, in what direction 
the candle-power is to be measured. In the earliest days incandescent 
lamps were rated by their maximum candle-power; now, however, the most 
common practice is to use the mean horizontal candle-power. In compar- 
ing lamps having differently shaped filaments this is in general not a fair 
basis, since two lamps might give the same total flux of light and yet one 
of them might have a much smaller mean horizontal candle-power than 
the other. These differences are recognized by the differences in the spher- 
ical reduction factors of the two. A small difference in spherical reduc- 
tion factor may have a very large influence on the results obtained in a 
life-test. The fair way is to use the total flux of light or the mean spherical 
candle-power as the basis for comparing lamps or illuminants of different 
types. The American Nernst lamp is usually rated by its maximum candle- 
power, that is, the candle-power immediately below it. The intensity in 
this direction is increased considerably by the light reflected from the heater 
coils and other parts of the lamp. No standard method for candle-power 
rating of arc lamps has ever been adopted in America. In Germany the 
mean lower hemispherical intensity is chosen for this purpose. 

raCAWIMBSClSira JLAIttPS. 

Watts per candle. — The condition of operation of an incandes- 
cent lamp is usually specified by the watts per candle, meaning, ordinarily, 
the watts per mean horizontal candle. The efficiency of a lamp is inversely 

{)roportional to its watts per candle. The life history of a carbon filament 
amp is characterized by a small initial increase in candle-power lasting for 
about 50 hours in the case of a 3.1 watt per candle-lamp and then by a 
unform decrease in candle-power until the lamp fails. This is accom- 
panied by a regularly increasing blackening of the bulb. It has been 
shown (Sharp, Electrical World, Vol. 48, p. 18), that the age of a lamp 
may be estimated by an examination of the degree of bulb blackening. 
The light from frosted lamps decreases more rapidly than that from un- 
frosted ones, an effect which has been shown (Millar, Electrical World, April 
20, 1907) to be due to the increased absorption of that portion of the light 
which suffers multiple reflections. Any lamp may be operated at any watts 
per candle simply by raising or lowering the impressed voltage, but the life 
of a lamp decreases very rapidly with decreased watts per candle. In opera- 
tion it is necessary to strike a balance between increased efficiency and in- 
creased cost of lamp renewals. The standards are 3.1, 3.5 and 4.0 watts 
per candle. Closely regulated voltage is essential to successful 3.1 watts 
per candle operation. 

After a lamp has reached a certain point in its decline in candle-power 
and efficiency, it is more economical to replace it with a new one than to 
consume energy in a wasteful device. The period of the life at which this 
condition is reached is called the ''smashing point," of the lamp. The 
smashing point may be computed, but it is found in practice that it is most 
satisfactory to assume uniformly that its point has been reached when the 
candle-power has decreased 20 per cent from the initial value. This con- 
stitutes by common consent the close of the "useful life" of a carbon fila- 
ment lamp. 

Spherical Candle-power and Distribution Curves. — A 
lamp filament giving a certain total flux of light may be made to give a 
greater or a smaller proportion of this in the horizontal direction. There- 



INCANDESCENT LAMPS. 



541 



fore the mean horizontal candle-power is not a true basis for comparing the 
performance of lamps of different types. The "spherical reduction fac- 
tor," or ratio of mean spherical to mean horizontal candle-power must be 
taken into consideration. The following curves and table give values for 
this factor for different types of lamps and the axial distribution of candle- 
power about the same types. The curves show also the Rousseau diagrams 
for the lamps, that is, curves the area enclosed by which is proportional 
to the mean spherical candle-power. The data were obtained at the Elec- 
trical Testing Laboratories. 



Lamp 
Type. 



Description. 



Double loop. 

Oval. 

Small spiral; single turn. 

Large spiral; single turn. 

Medium spiral; single turn. 

Short-legged spiral; double turn. 

Elliptical spiral, double turn, axis of ellipse horizontal. 




Lamp Type. 
Watts. 



End-on c.p 

Mean horizontal c.p. . . . 
Mean spherical c.p. . . . 
-p f - . Mean spherical c.p. 



Mean horizontal c.p. 
Mean spherical c.p. 
End-on c.p. 
End-on c.p. 
Mean horizontal c.p. 
Watts per mean spherical . 
Watts per mean horizontal 
Watts per end-on .... 



Ratio: 



Ratio: 



1 
49.6 



5.06 
16.00 
12.82 

0.802 



2.54 



0.316 

3.88 
3.10 
9.8 



2 
49.6 



3 
63.5 



7.3 
16.0 
13.19 

0.825 



1.81 



0.456 

3.76 
3.10 

6.78 



7.7 
16. C 
13.42 

0.840 



1.74 



0.481 

4.73 
3.97 

8.26 



4 
56.6 



16.0 
13.63 

0.854 



1.42 



0.602 

4.15 
3.52 
5.90 



5 

53.8 



9.31 
16.0 
13.78 

0.862 



1.48 



0.582 

3.91 
3.36 

5.78 



59.3 



11.4 
16.0 
14.07 

0.880 



1.23 



0.712 

4.22 
3.70 
5.20 



7 
64.74 



15.9 
16.0 
15.72 

0.983 



0.864 



0.992 

4.09 
4.02 
4.04 



542 



ELECTRIC LIGHTING. 



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544 ELECTRIC LIGHTING. 

The Proper Use of Incandescent Lampg. 

(From a Circular of the General Electric Company.) 

A lamp to give satisfaction must not only be properly made, but it must 
also be properly used. A lamp of the highest quality may be so misused as 
to give only a small fraction of its rated light capacity. Proper use, produ- 
cing a maximum of light at a minimum expense, requires : 

That the lamps be burned at marked voltage. 

That the voltage be kept constant. 

That lamps be replaced whenever they get dim. 

The last requirement is not considered economical by many users who 
prize lamps' that have long life, and insist on using them as long as they 
will burn. Let us see by an example if extremely long life is desirable. 

As the cost of current varies greatly, we will assume an average cost of 
one-half cent per lamp hour. If a rated 16-candle-power lamp, burned 
for 1000 hours, be burned an additional 1000 hours, it takes practically the same 
current during the last period, but gives an average light of only about 8 
candles. The cost of current for the 2000 hours is $10.00. A new lamp costs 
20 to 25 cents; and had three lamps, with a life of about 700 hours each, been 
used during the entire period, the average light would have been fully 
doubled, at an added expense of not more than 50 cents, or 5 % of cost of 
current. In other words, by adding 5 % to operating expense (representing 
the cost of the two renewal lamps) the customer would add 100 % to the 
light given. One new lamp gives a light equal to two old ones at half the 
cost of current. If the old lamps gave light enough, the new lamps would 
halve the number of lamps in use, and produce the same light with half the 
current. 

It is important to note that the above example is based on results obtained 
with the highest grade of lamps. With an inferior quality of lamp the ar- 
gument against extremely long life would be still stronger and the neces- 
sity of frequent renewals of lamps much greater. 

Thus, from any point of view, it is false economy to select lamps with a 
sole regard for long life. Lamps should be renewed when dim, for in no 
other way can light be produced economically. 

The points to be remembered are as follows : 

Do not run pressure above the voltage of the lamps. Increased pressure 
means extra power; and although the old lamps may thus give more light 
for a while, every new lamp that does not break from the excessive pressure 
will deteriorate very rapidly and give greatly diminished light. 

Do not treat incandescent lamps like lamp chimneys, and use them until 
they break. They should be renewed whenever they get dim. 

TAfe and Candle-power of Lampi. 

Since the prime function of an incandescent lamp is to give light, the best 
lamp is that which gives maximum light at minimum cost. This is an 
exceedingly simple axiom, and yet few users of lamps follow it out in prac- 
tice. Lamps are repeatedly selected for long life, irrespective of good, uni- 
form candle-power. Lamps are often continued in use long after their 
candle-power has seriously diminished. 

An examination of the characteristics of an incandescent lamp will give 
a clear understanding of the principles applying to their selection and use. 
A theoretically perfect lamp would maintain its normal candle-power 
indefinitely, or until the lamp was broken. In practice the deterioration of 
the lamp filament causes a steady loss of candle-power. 

Reg-arding* f ,«>** in Candle-power. — The drop in candle-power 
is a characteristic of an incandescent lamp always to be borne in mind. 
The relative drop or loss of candle-power, other things being equal, 
determines the comparative value of different lamps. We may have a 
lamp that loses 50 per cent in candle-power inside of 200 hours on a 3- 
watt basis. Considered from the standpoint of life only, such lamps are 



INCANDESCENT LAMPS. 545 

excellent, because their filaments deteriorate to such a degree that it is 
practically impossible to supply enough current to brighten them up to the 
breaking point, but no discerning station manager would want such dim 
lamps, even with unlimited life. As in the selection of incandescent lamps 
so in their use — the exclusive consideration of life leads to poor results 
Loss of candle-power in a lamp sooner or later makes it uneconomical to 
continue in use. 

A customer cares little how efficiently a station is operated, but is much 
concerned about the quality of light furnished. Some means of keeping the 
average life below 600 hours should be adopted by every lighting company 
that has any regard for the economical production of light, or the satisfac- 
tion of their customers. 

A simple method is to fix the average life at 600 hours or less, and then 
determine from the station record how many lamps should be renewed each 
month to keep the average life within this limit. The required number of 
lamps should be renewed each month. 

If, for example, a station decides on an average life not to exceed 600 
hours and the station records show that on the average 60,000 lamp hours of 

current are supplied monthly, then it would be necessary to renew ■ ' or 
100 lamps a month. 



The Importance of Good Regulation. 

Proper Selection and Use of Transformers* — Poor regulation 
of voltage probably results in more trouble with customers than any other 
fault in electric lighting service. 

Some central station managers act on the theory that so long as the life 
of the lamp is satisfactory, an increase of voltage, either temporary or per- 
manent, will increase the average light. The fact is that when lamps are 
burned above their normal rating the average candle-power of all the 
lamps on the circuit is decreased; and if the station is on a meter basis, it 
increases the amount of the customers' bills. 

Evil* of Excessive Voltage. — Excessive voltage is thus a double 
error — it decreases the total light of the lamps, and increases the power 
consumed. The loss of light displeases the customers and discredits the 
service. If light is sold by meter, the increased power consumption dissat- 
isfies the customers; if light is sold by contract, the additional power is a 
dead loss to the station. If increased light is needed, 20 candle-power 
lamps should be installed, instead of raising the pressure. Their first cost 
is the same as 16 candle-power lamps; they take but little more current 
than 16 candle-power lamps operated at high voltage, and give greater 
average light. 

Increased pressure also decreases the commercial life of the lamp; and 
this decrease is at a far more rapid rate than the increase of pressure, as 
shown in the following table. This table shows the decrease in life of 
standard 3.1 watt lamps, due to increase of normal voltage. 

Per Cent of Normal Voltage. Life Factor. 

100 1.000 

101 0.795 

102 .615 

103 .49 

104 .40 

105 .34 

106 .29 

From this table it is seen that 3% increase of voltage halves the life of a 
lamp, while 6% increase reduces the life by two-thirds. 

Irregular pressure, therefore, necessarily results in the use of lamps in 
which the power consumption per candle is greater than a well-regulated 
pressure would allow. The result is reduced capacity of station, and 
reduced station efficiency. 



546 ELECTRIC LIGHTING. 

These remarks apply with special force to alternating-current stations, 
since we have here two sources of possible irregularity in voltage — the 
generator and the transformer. Poor regulation is most apt to occur in the 
transformers, and the utmost care should, therefore, be taken in their selec- 
tion and use. The efficiency of the average lamp on alternating systems 
is nearly 4 watts per candle. With good regulation obtained by the intelli- 
gent use of modern transformers, the use of lamps of an efficiency of 3.1 
watts per candle becomes practicable. It is thus possible to save 25 % in 
power consumption at the lamps, and increase the capacity of the station 
and transformers by the same amount. 

The general adoption of higher voltage secondaries gives smaller loss in 
wires, and permits the use of larger transformer units, thus greatly improv- 
ing the regulation. On this account 50-volt lamps are gradually going 
out of use. The replacement of a number of small transformers by one 
large unit, and of old, inefficient transformers by modern types, has also 
been of immense advantage to stations. A large number of stations, 
however, still retain these old transformers, and load their circuits with 
large numbers of small units. Such stations necessarily suffer from loss 
of power, bad regulation, and a generally deteriorated lighting service. 
Simply as a return on the investment, it would pay all such stations to scrap 
their old transformers and replace them with large and modern units. 

Proper care in the selection of transformers considers the quality and the 
size. Quality is the essential consideration, and should have preference over 
first cost. No make of transformer should be permitted on a station's cir- 
cuit that does not maintain its voltage well within 3 per cent from full load 
to no load. The simple rule regarding size is to use as large units as possible, 
and thus reduce the number of units as far as the distribution of service 
permits. Every alternating station should aim to so improve regulation as 
to permit the satisfactory use of 3.1- watt lamps. 

Good regulation is eminently important to preserve the average life and 
light of the lamps, to prevent the increase of power consumed by the lamps, 
and to permit the use of lamps of lower power consumption, so that both 
the efficiency and capacity of the station may be increased. 

Constant voltage at the lamps can be maintained only by constant use of 
reliable portable instruments. No switchboard instrument should be 
relied on, without frequent checking by some reliable standard. Owing to 
the varying drop at different loads, constant voltage at the station is not 
what is wanted. Pressure readings should be taken at customers' lamps at 
numerous points, the readings being made at times of maximum, average 
and minimum load. Not less than five to ten readings should be made at 
each point visited, the volt-meter being left in circuit for four or five min- 
utes, and readings being taken every fifteen seconds. The average of all the 
readings gives the average voltage of the circuits. Lamps should be or- 
dered for this voltage, or if desired, the voltage of the circuits can be re- 
duced or increased to suit the lamps in use. The practical points are to 
determine the average voltage at frequent periods with a portable volt- 
meter at various points of the circuits, and then to arrange the voltage of 
the lamps and circuits so that they agree. 

Candle-Hours — The It emulation of lamp Value. 

The amount of light given by lamps of the same efficiency is the only 
proper measure of their value. The amount of light given, expressed in 
candle-hours, is the product of the average candle-power for a given period 
by the length of the period in hours. 

Many of the best central station managers consider that a lamp has passed 
its useful life when it has lost 20 % of its initial candle-power. In the case 
of a 16 candle-power lamp, the limit would be 12.8 candle-power. The 
period of time a lamp barns until it loses 20 % of its candle-power may 
therefore be accepted as its useful life. The product of this period in hours 
by the average candle-power gives the '* candle-hours " of light for any 
given lamp. 

The better a lamp maintains its candle-power under equal conditions of 
comparison the greater will be the period of "useful life," and therefore 
the greater will be the "candle-hours." This measure is, therefore, the 
only proper one with which to compare lamps and determine their quality. 



INCANDESCENT LAMPS. 



547 



The practical method of comparison is as follows : Lamps of similar 
candle-power and voltage are burned at the same initial efficiency of 3.1 
watts per candle on circuits whose voltage is maintained exactly normal. 
At periods of 50, 75, or 100 hours the lamps are removed from the circuits 
and candle-power readings taken, the lamps being replaced in circuit at the 
end of each reading. Readings are thus continued until the candle-power 
drops to 80 % of normal. The results obtained are then plotted in curves, 
and the areas under these curves give the "candle-hours" and the relative 
Value of the different lamps. 



Variation in Candle -power and Efficiency. 

In the following table is shown the variation in candle-power and effi- 
ciency of standard 3.1 watt-lamps due to variation of normal voltage. 



Per Cent of Normal 
Voltage. 


Per Cent of Normal 
Candle-power. 


Watts per Candle. 


90 


53 


4.68 


91 


57 


4.46 


92 


61 


4.26 


93 


65 


4.1 


94 


69* 


3.92 


95 


74 


3.76 


96 


79 


3.6 


97 


84 


3.45 


98 


89 


3.34 


99 


94* 


3.22 


100 


100 


3.1 


101 


106 


2.99 


102 


112 


2.9 


103 


118 


2.8 


104 


124* 


2.7 


105 


131* 


2.62 


106 


138* 


2.54 



Example: Lamps of 16 candle-power, 105 volts, and 3.1 watts, if burned 
at 98 % of normal voltage, or 103 volts, will give 89 % of 16 candle-power, or 
14J candle-power, and the efficiency will be 4.34 watts per candle. 

lamp Renewals. 

The importance and necessity of proper lamp renewals applies forcibly 
to all stations, regardless of the cost of power, and whether lamp renewals 
are charged for or furnished free. The policy of free-lamp renewals at the 
present low price of lamps is, however, preferable for both station and cus- 
tomer. Free lamp renewals give a station that full and complete control of 
their lighting service so requisite to perfect results. 



Points to be Remembered. 

That a constant pressure at the lamps must be maintained. 

That the lamps are not to be used to the point of breakage — they should 
be renewed when they become dim. 

That satisfaction to customers, and the success of electric lighting, are 
dependent upon good, full, and clear light, which old, black, and dim lamps 
cannot give. 



548 



ELECTRIC LIGHTING. 



That to furnish a good, full, and clear light is as much a part of the light* 
ing company's business as to supply current to light the lamps. 

That a company should always endeavor to keep, the average life of lamps 
within 600 hours. 

That to renew dim lamps properly en the free renewal system, inspectors 
should examine the circuits regularly when the lamps are burning. If 
lamp renewals are charged to customers, induce them to exchange their 
dim lamps. 

Ltmiiiio*it v of Incandescent Lampi. 

As showing the quality of incandescent light, we present here a curve 
showing the relative luminosity of an incandescent lamp at different regions 
of the visible spectrum. 

On this subject Prof. E. L. Nichols states the following : 
" The most important wave-lengths, so far as light-giving power is con- 
cerned, are those which form the yellow of the spectrum, and the relative 



LUMINOSITY OF 
INCANDESCENT LAMP 
CFERRY.) 




400 RELATIVE 
WAVE LENGTH 



RED ORANGE' YELLOW 



Fig. 13. Regions of Spectrum. 



luminosity falls off rapidly both toward the red and the violet. The longer 
waves have, however, much more influence upon the candle-power than the 
more refrangible rays. 

" Luminosity is the factor which we must take into account in seeking a 
complete expression for the efficiency of any source of illumination, and 
the method to be pursued in the determination of luminosity must depend 
upon the use to which the light is applied. If we estimate light by its 
power of bringing out the colors of natural objects, the value which we 
place upon the blue and violet rays must be very different from that which 
would be ascribed to them if we consider merely their power of illumina- 
tion as applied to black and white. In a picture gallery, for instance, or 
upon the stage, the value of an illuminant increases with the temperature 
of the incandescent material out of all proportion to the candle-power, 
whereas candle-power affords an excellent measure of the light to bo 
used in a reading room. 



INCANDESCENT LAMPS. 



549 



Metallized Carbon or Gem lamps, — The so-called " metal- 
lizing" process as applied to carbon filaments consists in heating the filaments 
to an enormously high temperature both before and after flashing, using 
a carbon tube electric furnace for the purpose. The term "metallized" 
is applied on account of the positive temperature coefficient which the 
filaments acquire in the process. The useful life of the metallized filament 
lamps at 2.5 w. p. c. is said to be the same as that of the ordinary carbon lamp 
at 3.1 w. p. c. 



label Hating* of Gem Lampi. 

The style of label employed for Gem Lamps is as here shown. These 
labels are printed for all the voltages from 100 to 130 and 
for the various sizes of lamps. 

As shown in the cut of label, only the total wattage of 
lamp and the volts are printed. Candle-power values 
are not given, as these values vary with the different 
forms of reflectors. (See candle-power distribution 
curves.) The voltage markings are arranged to show 
three voltages in steps two volts apart, and this provides 
a ready method of varying the efficiency and life of lamps 
to suit different conditions. The values at each of the 
three voltages are shown in the following table : 

Lamps should, of course, be ordered at the " Top" or 
first voltage (VI) whenever possible, so as to secure the full 
lighting value and maximum efficiency and brilliancy. Fig. 14. 




Table of Values at 1st, 2nd and 3rd Voltages. 



Voltage of Circuit. 


Per 

cent 
Total 
Watts. 


Per cent 
of c. p. 
Values. 


Eff. in 
w. p. c. 
(mean 
horizontal 
c. p.) 


Useful 

Life 

in 

hours. 


Same as " Top" or 1st Voltage (VI) 
Same as "Middle " or 2nd Voltage (V2) 
Same as ■ • Bottom ' ■ or 3rd Voltage ( V3) 


100% 
95% 
90% 


100% 
90% 
80% 


2.5 

2.65 

2.8 


500 

700 

1,000 



TA]¥TAirM LAMP. 

The filament of this lamp is a fine wire of metallic tantalum. The high 
melting point and low vapor pressure of this metal make it possible to 
operate the lamps at 2.0 w.p.c. with a life comparable with that of the 
ordinary lamp at 3.1 w. p. c. The life on alternating current is much shorter 
than on direct current and is a function of the frequency. Fig. 15 shows 
free-hand drawings of microscopic views of the tantalum filament as affected 
by rise on alternating and direct current. The vertical distribution of 
intensity changes during the life of the lamp, the horizontal intensity 
diminishing more rapidly than the spherical, due chiefly to more rapid 
bulb blackening in the horizontal zone. On this account the spherical 
reduction factor also changes. (See Fig. 16.) Characteristic life curves 
of tantalum lamps manufactured in Germany in about 1904, are shown 
in Figs 17 and 18. These tests were made in the Electrical Testing Lab- 
oratories. (See Sharp, New Types of Incandescent Lamps, Proc. A. I.E.E- 
10Q5, p. 809.) 



550 



ELECTKIC LIGHTING. 




ALTERNATING CURRENT 130 rv 300 HOURS 



ALTERNATING CURRENT 60 rv t57 HOURS 



^T^F 



ALTERNATING CURRENT 25 *V 467 HOWRS 



jTy*^ yrnr ^^7rfrir^^\ ^rf>m m ' ■■ ..i.* m i l .. >f f " T *' -* ;.■ >, . . ■ ■■ t — - 



OIRECT CURRENT 492 HOURS 




NEW LAMP 

Fig. 15. Microscopic Views of the Tantalum Filament. 




Fig. 16. 



INCANDESCENT LAMPS. 



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LIFE CURVES OF REPRESENTATIVE 

TANTALUM LAMPS 

TE6TED ON DIRECT CURRENT AT RATED VOLTS 

ELECTRICAL TESTING. LABORATORIES 






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ELECTRIC LIGHTING. 



HOURS 
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HOURS 

Fig. 18. Curves of Tantalum and Carbon Lampe. 



INCANDESCENT LAMPS. 



553 



TuaresMsar iamp. 

The metal tungsten has such a high melting point (about 3200° C. f 
according to Waidner and Burgess) that when it has been worked into lamp 
filaments by special processes, the lamps so produced can be operated at 
very high efficiencies. The most favorable condition of operation is at 
about 1.25 watts per candle, which is the point most commonly selected by 
makers in this country. Even at this low value the rate of deterioration in 
candle-power and efficiency is very slow until near the end of the life when 
it may become very rapid. Because of the high conductivity of the metal 
it has as yet been found impracticable to make 100-volt lamps of lower 
candle-power than 25, but tungsten lends itself admirably to the construc- 
tion of heavy current, low-voltage lamps for use in series on constant 
current street-lighting circuits. Life curves of six German- made tungsten 
lamps (Osram lamps) are shown in Fig. 19. 




Fig. 19. Tests of Six Tungsten Lamps. 



Effect of Chang-es in Voltug-e. 

Change with 5 per cent increase in voltage above normal. 

Candle-power. Watts per Candle 

Carbon +30% -15% 

Metallized +27% -13% 

Tantalum +22% -11% 

Tungsten +20% -10% 



554 



ELECTRIC LIGHTING. 




95 100 105 

PERCENTAGE VOLTS 



Fig. 20. Characteristic Curves of Tungsten, Tantalum, Metallized 
and Carbon Lamps. 




FfG. 21. Tungsten 
60-Watt Lamp. 



These data show that Tungsten lamps are less 
affected by voltage fluctuation than are other 
lamps. The operating temperature of the Tung- 
sten is so high that the light is of peculiar and 
agreeable whiteness, much better fitted for the 
matching of colors than is that of the carbon 
lamp. 

Lamps are now on the market rated at 100, 60, 
and 40 watts for use on circuits of 100 to 125 volts. 
Series burning lamps for street lighting are also 
available. The life of a Tungsten multiple lamp 
at 1.25 watts per candle is said to be 800 
hours. 

The following statement and table are from a 
Bulletin of the Engineering Department of the 
National Electric Lamp Association. 

Operating* Cost. — Table 5 shows the total 
cost of operating various lamps on various costs 
of power. The combined cost of power and lamp 
renewals, for a period of 1000 hours, shows the 
saving effected by the use of high efficiency lamps, 
when the cost of power is high. 

At costs of power greater than two cents per 
kilowatt hour the Tungsten lamp is the cheapest, 
considering both the first cost of the lamp and 
the cost of power, excepting only the higher 
candle-power Tantalum lamp. The latter is 
cheaper than the Tungsten at costs of power 
below two and one half cents per kilowatt hour 
on 60-cycle alternating and four cents per kilowatt 
hour on direct current. 



INCANDESCENT LAMPS. 



555 



WHEN Atfl> HOW J[]¥CA]¥I>Ef8C 1 E]¥T LAMP! 
ARE I ISJEI*. 

By Mortimer Norden. 

The following data have been collated to show the yearly consumption of 
current per 16 c.p. lamp on the circuits of a large central station company, 
giving the yearly average of current used in kw.-hours. The data represent 
ten plants all operated by the one company : 

Totals of JLverag-e Consumption, Showing* Yearly Con- 
sumption per IG-c.p. Lamp Connected. 



1 Green house 

24 Colleges and schools 

127 Churches Q 

3 Parks 

1343 Residences 

64 Dentists' and physicians' offices 

344 Factories 

8 Signs 

14 Public halls 

6 Dressmakers 

1 Grain elevator 

102 Municipal buildings, hospitals, armories and 

city halls 

104 Clubs and lodge rooms 

147 Nine o'clock stores 

401 Seven o'clock stores 

449 Eight o'clock stores 

137 Livery stables and stables 

26 Eleven o'clock stores 

287 Office buildings and offices ...'.... 

10 Theaters 

9 Road houses 

45 Banks and insurance companies 

11 Ten o'clock stores 

2 Cold storage companies 

4 R. R. terminals and docks 

180 Drug, confectionery and cigar stores . . . 

640 Saloons, restaurants and concert halls . . 

327 Six o'clock stores 

22 Wholesale butchers 

25 Commission dealers 

8 Twelve o'clock stores 

3 Steamship docks 

5 Hotels 

23 Railroad stations 

2 All night stores 

4904 customers, 



Lights. 



Kw.-hours. 



54 


1.33 


2,863 


5.70 


11,616 


7.75 


416 


9.24 


40,095 


10.73 


1,066 


15.10 


21,936 


15.53 


365 


18.48 


1,781 


18.81 


111 


20.24 


24 


20.75 


14,654 


24.79 


7,391 


24.82 


4,433 


26.35 


17,623 


26.55 


13,228 


27.10 


1,775 


29.56 


624 


30.01 


7,363 


30.65 


10,581 


32.13 


305 


32.70 


3,322 


33.80 


339 


38.34 


158 


40.82 


854 


42.14 


4,370 


42.44 


17,592 


43.62 


23,584 


45.61 


1,012 


46.92 


518 


48.06 


170 


52.44 


2,293 


61.71 


1,099 


65. 


909 


118.98 


410 


218.06 



214,934 
Grand average 27.28 



556 



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558 ELECTRIC LIGHTING. 



COOPER-HEWITT ^lEHCI HY VAPOR LAMP, 

Characteristic*. — This lamp is an arc lamp rather than an incandescent 
lamp, the arc having a mercury cathode and passing through vapor of mercury 
at low vapor tension. The light probably results from the electro-lumines- 
cence of the mercury vapor and not from any very high temperature pro- 
duced either at the anode, the cathode or in the arc stream. Being produced 
in this way, the light shows not a continuous spectrum of ail the colors, 
but a discontinuous or line spectrum characteristic of mercury. The per- 
centage of the electrical energy which is converted into light is relatively 
high, and the lamp is very efficient. It would constitute for many purposes 
an almost ideal source of light were it not for the unfortunate fact that 
in the spectrum of mercury red is almost entirely lacking. The result is that 
the light of this lamp has a tint which to most people is very distasteful, 
namely a strongly greenish hue. Red objects look black or purple in it, 
and all colors containing red are falsely rendered. When this character- 
istic is not objectionable the Cooper-Hewitt lamp may be used to good 
advantage. It is asserted that the light is very favorable for the eyes, 
causing little fatigue. It has been used in draughting rooms to some ex- 
tent. Its actinic powers are high, due to the presence of bright violet lines 
in its spectrum, hence it Is a desirable source of light for night photography, 
for copying, blue-printing, etc. 

Photometry. — The photometry of the Cooper-Hewitt lamp is attended 
with considerable difficulties due to the large linear dimensions of the lamp, 
and to the wide divergence of the color of its light from that of other sources. 

As a result of its large linear dimensions it is necessary to place the lamp 
at a considerable distance from the photometer. For distances which 
are small in comparison with the length of the lamp, the intensity of the 
light does not diminish as the square of the distance. The difficulties due 
to the color of the light are two-fold. In the first place photometer settings 
are difficult and uncertain to make unless a nicker photometer is used, and 
the personal equation of the operator is a large one. In the second place 
what is known as the Purkinje Phenomenon plays an important part in the 
results. This is a physiological effect, according to which if a reddish and 
a greenish or a bluish light appear equally bright when the intensity of 
each is high, the reddish light appears much fainter than the other when 
the intensity is greatly diminished. It follows from this that the apparent 
candle-power of the Cooper-Hewitt lamp when photometered against an 
ordinary standard, such as an incandescent lamp, is higher the farther the 
lamps are removed from the photometer or the dimmer the illumination 
on the photometer disk. In order to get even approximately accurate 
results in the photometry of this lamp a standard illumination on the 
photometer disk must be chosen and adhered to. No such standard illum- 
ination has as yet been designated and established. 

The following matter is condensed from an article in the Electrical Age. 

The Cooper-Hewitt lamp consists essentially of a glass tube, from which 
all the air has been exhausted, but which contains a small amount of liquid 
mercury and is filled with mercury vapor. At the ends of the tube are 
means for introducing the electric current. At the positive end the tube 
swells out, forming a chamber, which is called the condensing chamber. 
A platinum wire is sealed into each end of the lamp. At the positive end 
the wire connects either with a small puddle of mercury or a piece of iron, 
according to the type of electrode used, and this constitutes the positive 
electrode, or anode. At the negative end the wire connects with a small 
puddle of mercury constituting the negative electrode, or cathode. 

The lamp may be made of such dimensions as to make it suitable for a 
direct-current line of any assigned voltage. Most lamps are designed to 
run at a pressure of about 115 volts. A lamp about 4 feet in length and 
1 inch in diameter would be suitable for this voltage and would work best 
on a current of about 3 amperes. 

Before being started, the electrical resistance of a mercury vapor lamp 
is very high. 

This negative electrode resistance to starting may be almost totally 
destroyed in various ways. One method consists simply in tilting the 
lamp until the two electrodes are brought into connection by a thin stream 
of liquid mercury along the length of the tube; then, upon tilting back, 



INCANDESCENT LAMPS. 559 

an arc is started which prevents the high cathode resistance from making 
its appearance, and the lamp continues to operate until the current is turned 
off. Another method of starting is to send a small, momentary high- 
tension current from an inductance coil through the lamp, which at the 
same time is connected with the low-voltage mains. This high-tension 
current penetrates the high cathode resistance, and the current from the 
low-voltage mains follows, and if this latter current be great enough the 
high cathode resistance does not again make its appearance until the cur- 
rent is turned off; and if it is desired to relight the lamp the same procedure 
has to be repeated. To facilitate the starting of the lamp by this method 
the so-called "starting band" is employed. This is simply a narrow, thin, 
metallic band attached to the outside surface of the lamp in the neighbor- 
hood of the cathode, and connected by a wire to the positive terminal of 
the lamp. 

In the latest model of automatic lamps this operation is accomplished 
by the use of a "shifter." This consists of an evacuated glass bulb con- 
taining mercury which is shifted by the action of an electromagnet when 
the circuit is closed and which interrupts the current. Thereby a high 
potential is induced which starts the lamp. 

A view of this lamp is shown in Fig. 22, of the interior of the auxiliary box 
in Fig. 23, and a diagram of connections in Fig. 26. 



^ Fig. 22. Type " P " Lamp. 

The resistance which a mercury arc offers to the passage of electric 
current may be separated into three distinct parts: — First, the resist- 
ance encountered by the current in passing from the anode into the 
vapor ; second, the resistance of the vapor column itself; and third, the re- 
sistance encountered by the current in passing from the vapor into the 
cathode. 

In the commercial lamp the potential drop over the anode is about eight 
volts and is approximately independent of the magnitude of the current 
flowing and the diameter of the tube. The anode resistance, then, varies 
inversely with the current. The potential drop over the cathode is about 
five volts and is approximately independent of the diameter of the tube 
and of the magnitude of the current flowing, provided that the current is 
above a certain minimum value, depending upon the inductance and re- 
sistance in series with the lamp. If the current falls below this minimum 
value, the cathode resistance immediately becomes enormous and the 
lamp is extinguished. A certain amount of inductance and resistance is 
usually placed in series with the lamp, as this has a beneficial effect, caus- 
ing the lamp to operate more steadily. 

In fixing the resistance of the vapor to the passage of the current, four 
quantities predominate, namely, the length of the tube, the diameter of the 
tube, the magnitude of the current, and the density of the vapor. 

The results can be roughly expressed as follows: — The resistance of 
a lamp increases directly with its length; it decreases with increase of its 
diameter and at a greater rate when the current and diameter are small 
and the vapor density large; it decreases with increase of the current and 
at a greater rate when the current and diameter are small and the vapor 
density large; it increases with increase of the vapor density and almost 



560 



ELECTRIC LIGHTING. 



directly, although at a certain value of the density (varying -with different 
currents and different diameters), the rate of increase changes somewhat 
abruptly and is less for values of the density greater than this value than 
it is for lesser values. 

When the vapor density is quite high, say for values greater than those 
corresponding to a pressure of three millimeters of mercury, the luminous 
column no longer fills the tube; and when the density is very high it is of 
very small cross section and passes along the axis of the tube. The vapor 




08E THESE POSTS FOJ» 
110-1.20 VOLTS 
T00-T10 « 




Fig. 23. Auxiliary for "P" 
Lamp (casing removed). 1. 
Ceiling Plate. 2. Nipple. 3. FlG 24 Wiri Diagram. 

Insulating Joint. 4. Binding Type "P" Lamp 

Post for Main. 5. Inductance JH H * 

Coil. 6. Ballast. 7. Shifter. 
8. Actuating Armature. 9. 
Terminal Block. 

pressure of a lamp operating under normal conditions is in the neighbor- 
hood of one millimeter of mercury. 

It has been observed by Dr. Hewitt that there is a value of the vapor 
density at which the light efficiency of a lamp is greatest, and lamps are 
designed to run at this density when they are to be operated under com- 
mercial conditions. In order to maintain the density at the proper point 
the condensing chamber mentioned at the beginning of this article is em- 
ployed. This chamber usually, though not necessarily, surrounds the 
positive electrode at the upper end of the lamp. By virtue of its size it 
has a considerable radiating surface exposed to the air, and consequently 
the temperature within it, except in that portion of it which is quite close 
to the electrode, is low, compared with that in the other parts of the lamp. 
In consequence of this the pressure also is low in this region, and the mer- 
cury vapor from the main part of the tube rushes into the chamber and con- 
denses there. The effect of all this is to keep the vapor density in the con- 
ducting column at a lower value than it would otherwise assume. 

By making the condensing chamber of the proper dimensions, the vapor 
density can easily be made that corresponding to the greatest light effi- 
ciency. In connection with all this, it should be remembered that the mer- 
cury at the cathode is continually vaporizing, owing to the heat produced 



INCANDESCENT LAMPS. 



561 



by the current. After condensing in the condensing chamber the mercury 
falls back into the cathode end, and after a while again takes its turn at 
being vaporized. 

The efficiency is said to be somewhat higher than that of the arc lamp, 
and much higher than that of the incandescent light. 




Fig. 26. 



Diagram Illustrating the Method of Op- 
erating Lamps in Series. 



* 



-MMH 



QUICK-BBEAK SWITCH 
RESISTANCE 



— \smsmsisuir— 

INDUCTANCE COIL 



STARTING 
BAND 



& 



Fig. 27. Diagram illustrating the method of starting by high-tension dis- 
charge. To light the lamp, the main switch, which is mounted on a small 
panel board, is closed, and then the lever handle on the quick-break 
switch is pressed down, thus completing a circuit through the series 
resistances and inductances, charging the coil. On releasing the 
handle the quick-break switch automatically opens the circuit and 
the discharge of the coil passes through the lamp, breaking down 
its resistance and establishing a path for the main current. 



562 



ELECTRIC LIGHTING. 



THE * E1J \*T IAMP. 

Early in 1898 Dr. Walther Nernst exhibited in this country his new 
type of incandescent electric lamp. Mr. Westinghouse purchased the 
patents and placed at work upon it a staff of engineers, who have developed 
it into the present commercial form in this country. 

The light -emitting element of the lamp as developed by the Nernst Lamp 
Company of Pittsburgh, is termed a "glower." It is made by pressing 
through a die, a dough composed of the oxides of the rare earths mixed 
with a suitable binding material. The porcelain-like string thus formed 
is cut, after drying, into convenient lengths. It is then baked, and ter- 
minals are attached, by means of which a current of electricity may be passed 
through the glower. 

The glower of a standard 220-volt Nernst lamp is about 1" long by 3Y' 
in diameter. It is an oxide incapable of further oxidation, therefore 




„ HOLDING SCREW I 

ALUMINUM PLUG I 

1 ARMATURE SUPPORT/ 

— L.POST> 

ballastI 

■-- cut out coil 1 

armature 1 
~-tct silver contact stop 

" housing i 

contact sleeve porcelain/ 

globe holding screw 

holder porcelain) 

HEATER PORCELAINf 

0.0^ HEATER TCIBEl" 

GLOWER' 



GLOBE 



Fig. 28. 



operative in the open air. The presence of oxygen is essential. Glowers are 
insulators when cold, but become conductors when hot, hence they must be 
heated before they will conduct electricity sufficiently well to maintain 
themselves at a light -emitting temperature. 

The characteristic of the glower with reference to voltage is as follows: — 
As the current traversing the glower is increased, the voltage across its ter- 
minals rises, at first rapidly and then more and more slowly to a maximum; 
it then drops off with increasing rapidity as the current through the glower 
and the resulting temperature continues to increase. The glower is oper- 
ated on the ascending part of the curve at a point just preceding that of 
maximum pressure. Beyond this point the rapid decrease in the resistance 
of the glower makes the current difficult of control without a steadying 
resistance in series with it. This ballasting is accomplished by means of 
a fine iron wire mounted in a small glass tube filled with hydrogen. The 
diameter of this wire in a 0.4 ampere ballast is about .045 mm. Iron wire 
possesses, on reaching its so-called critical temperature, the property of 
increasing its resistance with great rapidity with rising temperature. 



THE NERNST LAMP. 



563 



The negative resistance temperature coefficient of a glower may thus 
be more than counter-balanced by the temperature coefficient of the iron 
*vire ballast placed % in series with it. For a 10% rise in current the resist- 
ance in the ballast increases 150%, so that a glower thus protected at once 
becomes operative through a wide range of voltage. 

The construction of a commercial lamp requires a device to heat the 
glower in starting. 

The heaters consist of thin porcelain tubes wound with fine platinum wire 
which in turn is held in place and protected from the intense heat of the 
glowers by a refractory paste. 

The automatic lamp is constructed with a cut-out to disconnect the 
heater from the circuit as soon as the glowers light. 

A general idea of the construction of the lamp and of its principal parts 
together with an understanding of its electrical connections may be gained 
from a study of Figs. 28, 29, and 30. 



Lamp Utrm/nals 




Fio. 29. 



SGlower Lamp 
Fig. 30. 



The action of a Nernst lamp when the switch is turned on is as follows: 
(1) The current passes through the heater, bringing it to a white heat; 
(2) the proximity of the glower to the heater results in the glower becom- 
ing a conductor, through which the current then passes; when the current 
through the glower has reached a predetermined amount; (3) the cut-out 
coil becomes energized by virtue of the glower current passing through it; 
(4) the armature of the cut-out which had heretofore closed the heater cir- 
cuit is attracted; and (5) this opens the heater circuit, leaving only the 
glowers in operation until the next time the lamp is turned on. Opening 
the switch which controls the lamp circuit allows the cut-out armature to 
fall into place again, thus connecting the heaters ready for starting. 

Efficiency. — It may be noticed that the efficiency of the Nernst lamp 
increases as the number of glowers increases. This is due to the fact that 
the glowers in the multiple glower lamps are operated in a highly heated 
atmosphere by virtue of the mutual heating effect of the several glowers. 
This causes the glowers to have a much lower voltage at the normal 



564 



ELECTRIC LIGHTING. 



current in the multiple glower lamp than is the case when they are operated 
in the open air, this difference amounting to about 16 volts in the six- 
glower lamp. 

Photometric Vests of Various Illuminants by National 
Electric JLiprlit Association. 



Illuminants. 


Multiple 
D.C. Arc. 


Multiple 
A.C. Arc. 


Nernst 6-Glower. 


Globes and Shades. 


Opal. 
Inner. 
Clear 
Outer. 


Opal. 
Inner. 
Clear 
Outer. 


Clear 
Globe. 


Opal. 
Globe. 


Clear 
H. C. 
Opal. 
Shade. 


E.M.F 

Current 

Watts 

Power Factor 

Mean Spherical c.p. . . 
Mean Hemispherical c.p. 
Watts per Spherical c.p. 
Watts per Hemispher. c.p. 


110 

4.9 
529 

1 
182 
239 

2.90 

2.25 


110 
6.29 

417 
.6 

140 

167 
3.02 
2.53 


226 

2.4 
542 

1 
163.9 
289 

3.30 

1.88 


226.5 
2.4 

543 
1 

168.6 

258.6 
3.22 
2.10 


226 

2.4 
542 

1 
155.8 
264.2 

3.48 

2.05 



Illuminants. 


Nernst 3-Glower. 


Nernst 1 -Glower. 


Globes and Shades. 


Clear 
Globe. 


Sand 
Blasted 
Globe. 


Clear 

H. C. 

Opal. 

Shade. 


Clear 
Globe. 


Sand 
Blasted 
Globe. 


E.M.F 

Current 

Watts 

Power Factor 

Mean Spherical c.p. . . 
Mean Hemispherical c.p. 
Watts per Spherical c.p. 
Watts per Hemispher. c.p. 


218.8 
1.2 

262 
1 
65.1 

112.6 
4.04 
2.33 


219.5 
1.2 
263 
1 
61.5 
96.9 
4.28 
2.72 


220 

1.2 
264 

1 

68.5 

118.3 

3.86 

2.23 


223.7 

0.4 
89 

1 
21.8 
38.7 

4.11 

2.31 


220.5 
0.4 
88 
1 
20.5 
31.8 
4.3 
2.78 



The British unit of c.p. used in above. 

The arc lamp figures were taken from the Report of the Committee for 
Investigating the Photometric Values of Arc Lamps, read before the 
National Electric Light Association in May, 1900. The Nernst lamp data 
were obtained from the report of the same committee which was presented 
at the Twenty-Sixth Convention in May, 1903. 

maintenance. — The frame and connections of the Nernst lamp form 
a permanent structure having an indefinite life, but its perishable parts 
have from time to time to be renewed. Of these, the ballast has a life 
averaging 25,000 hours. The heater has a life averaging about 8 months 
in ordinary use. The glower, however, like the incandescent lamp filament, 
has a practically definite term of use at the end of which it would be 
advisable to replace it whether burnt out or not. 800 hours are given by the 
company as the guaranteed life on 60 cycles. 

Behavior on Alternating- and IMrect Current. — Unlike 
the carbon incandescent lamp the life of glowers is not the same on 
direct current as on alternating current, and is affected even by the 
frequency of the latter. The American glower was constructed originally 
for use on alternating current only, while in Europe direct current lamps 
predominated. The direct current lamp in this country is a comparatively 
recent development and its glower life is shorter than that of the glower 
used with alternating current. 



THE MOORE VACUUM TUBE LIGHT. 



565 



THE TlOOltE VACCTM TUBE JLHSMT. 

The Moore Vacuum Tube Lighting System, invented by D. McFarlan 
Moore, has been in commercial service since 1903 and consists essentially 
of a glass tube about If inch diameter and of any form or length desired 
up to 200 feet. The tube is attached to the ceiling or walls by supporting 



XUBE DISTRIBUTED IN 

ANY FORM DESIRED 
TO LENGTHS OF 200 FT. 




DIAGRAM SHOWING ES'S^ENTfAL 
[ FEATURES OF THE MOORE LIGHT 



Fig. 31. 



fixtures at intervals of about 8 feet. A graphite electrode (3, Fig. 31) is 
sealed into each end of tube and the two electrodes enclosed within a steel 
terminal box (2) which also contains a static trans- 
former (4) and regulating device (6) called a feeder valve 
(see Fig. 32). The completed tube is exhausted to a 
pressure of about 1/10 mm. of mercury. The feeder valve 
performs the important service of feeding the tube some 
pure gas to take the place of that which is used up by the 
passage of the electric current through the tube. All 
vacuum tubes or bulbs through which current passes 
tend to attain a higher vacuum due to solidification or 
combination of the residual gases. There is a critical 
pressure, about 0.08 mm. of mercury, at which the con- 
ductivity is a maximum and the greatest current will 
flow. The pressure of maximum light efficiency is, how- 
ever, slightly higher, i.e., 0.1 to 0.12 mm., hence the 
feeder valve is adjusted to maintain the pressure at this 
point which it does as follows: 

A carbon plug (8, Fig. 31) is cemented into the mouth 
of the small bore tube (9) which connects to the lighting 
tube. This plug is normally covered by mercury the 
level of which is varied by the glass displacer (7) which 
also carries the iron core of the solenoid coil (5) which 
is connected in series with the transformer (4). As the 
pressure in the lighting tube falls the conductivity and 
therefore the current increases, and the plunger rises, 
allowing the surface of the mercury to fall and expose 
the tip of the carbon plug. A minute quantity of air FEEDER VALVE 
or whatever gas is supplied to the feeder valve, filters p IG 32 

through the porous carbon plug and finds its way to the 
lighting tube, the action continuing until the pressure is brought back to 




566 



ELECTRIC LIGHTING. 



normal. The device is capable of very close adjustment. The transformer 
is usually supplied with alternating current at 220 volts and raises the 
voltage to 2000 volts or more, depending on the length of tne tube. 

The tube is self-starting and responds at full brilliancy instantly upon 
closing the switch. 

The intensity may be made anything desired from 5 to 50 candle-power 
per lineal foot, the normal commercial brilliancy being 12 candle-power per 
foot, the radiation being uniform in all directions in planes perpendicular 
to the axis of the tube. The efficiency is said to vary from 1.4 to 2 watts 
per candle-power depending upon the length of tube, the light intensity, 
etc., and is not affected by variation of supply voltage. See Fig. 33. 

In practice, tubes are said to have a life of from 3000 to 5000 hours and 
then can be renewed at small cost. The efficiency is said to remain constant 
after the first 50 hours' run. 



«,« S 








































B^ 




4 5* I 1 














oC^ 


+£ 




in 










4 




^> 






■z 

% 15 3 "6000 

z 

*T 10 2 4000 








p 


i^v 




vt\^ 


p« 


D 




\ 


s 


/ 




^ 


^ 










o 


4 


/, 


>• 






W/ 


^TTS f 


ER H 


:fner 


C 


J 5 1 2000 
















/ 



















25 50 75 100 125 150 175 ,200 225 
LENGTH OFTUBE IN FEET 

Fig. 33. 



The color depends upon the gas supplied to the feeder valve. It i3 
exactly the same shade of white diffused daylight when fed with pure nitro- 
gen, and orange-pink when fed with air. 

The intrinsic brilliancy is claimed to be the lowest of any known illumi- 
nant and therefore is extremely soft and agreeable to the eyes and does 
not require to be shaded or diffused to avoid glare but may be reflected to 
obtain any distribution desired. An intensity of 0.66 candle-power per 
square inch corresponds with 12 candle-power per lineal foot. 



Efficiency of Tioore Tube. 

Early in 1907, Sharp & Millar conducted a series of tests on a Moore 
tube that had been installed in Assembly Room, No. 7, of the United 
Engineering Societies Building, and reported the following results. 

The tube was 176 feet long and approximately 1| inches diameter. It 
was fed with nitrogen gas, and operated as a 60-cycle system. 

Total watts consumed by tube system 3451 

Line volts 220.3 

Amperes 21 . 5 

Volt-amperes (apparent watts) 4736 

Power factor . 73% 

Total lumens produced 17,400 

Efficiency as light producer — lumens per watt .... 5.5 

Lumens per apparent watt 3 . 68 

Watts per equivalent mean spherical candle-power ... 2.49 
Apparent watts per equivalent mean spherical candle- 
power 3.41 



THE MOORE VACUUM TUBE LIGHT. 



567 



This installation of Moore Tube was compared with three installations 
of incandescent carbon filament lamps in the same room; they were as 
follows: 



No. 1, 



Installation 
Moore Tube. 
Installation No. 

Lamps under Tube. 
Installation No. 

Lamps in Rectangles. 



3.—: 



Installation No. 4.- 

Lamps with Reflectors. 



Moore Tube, 176 feet long, running around the 
room close to the cove. 

One hundred 16-c.p. lamps placed horizontally 
5 inches beneath the tube, and equally spaced. 

Eighty-four 16-candle-power lamps bare, ar- 
ranged in equal rectangles, 15 feet, 4 inches, 
above the floor. 

Same as No. 3, except that the lamps were 
equipped with Holophane distributing reflec- 
tors No. 7381. 



Results of the Comparative Tests. 



Instal- 
lation 
Number. 


Number 

of 
Lamps . 


Mean 
Horizon- 
tal c.p. 


Mean 

Spherical 

c.p. 


Watts per 
Horizon- 
tal c.p. 


Watts per 

Spherical 

c.p. 


Total 

Watts. 


1 
2 
3 
4 


1 

100 

84 

84 


(per ft.) 

8.1 

13.82 

11.31 

11.11 


(per ft.) 

7.9 

11.41 

9.33 

9.16 


2.39 
3.48 
4.26 
4.32 


2.48 
4.21 
5.16 
5.23 


3451 
4810 
4040 
4027 





. 


[llumination Values 


Efficiency Values. 


31 


Foot Candles. 


Lamp. 


Gross . 


Net. 


a 


Maxi- 
mum. 


Mini- 
mum. 


Mean. 


Vari- 
ation. 


Lumens 

per 

Watt. 


Lumens 
Effective 
per Watt. 


Lumens 
Effective 
per Lumen 
Generated. 


i 

2 
3 

4 


4.38 
3.27 
2.10 
2.51 


3.18 

2.28 
1.16 
1.26 


3.69 
2.69 
1.71 
1.97 


16.2% 
18.4 
27.5 
31.7 


5.05 
2.98 
2.44 
2.40 


2.08 
1.08 
0.82 
0.95 


41.2% 
36.2 
33.6 
39.6 



The above table shows that, with regard to the uniformity of the dis- 
tribution of illumination, the Moore Tube performance was very good, but 
that the performance of the incandescent lamps arranged beneath the tube 
was practically the same. 

A disadvantage from which the Moore Tube suffers is that it flickers in 
unison with the alternating current which feeds it. On 60-cycle current 
this flickering is not noticeable, except when the eye is moved rapidly or 
when an object is moved rapidly before the eye. It then becomes notice- 
able, and for certain work is very objectionable. It, however, has the great 
advantage of throwing a very soft light of low intrinsic brilliancy, which 
does not need to be diminished by diffusing glasses in order to make it 
entirely bearable for the eye. The test shows that its efficiency, while not 
equalling that of the tungsten lamp, is about equal to that of the tantalum 
lamp, and greater than that of any other incandescent lamp. 



568 ELECTRIC LIGHTING. 

ARC LAM IP* AN» ARC IIGHTIIira 

Revised by J. H. Hallberg, Consulting Engincm 

The arc lamp is an electrical apparatus in which an electric j»rc is struck 
and maintained between two or more electrodes, giving a brilliant illumi- 
nation, the color and intensity of which depends upon the composition 
and diameter of the electrodes, the kind of current supplied and the watts 
consumed. 

Owing to the extremely high temperature of the electric arc (varying 
between 2500 and 4000° C.) the electrodes must have a high volatilization 
point in order to obtain sufficient life from one set of them to make the 
lamp practical. Carbon has been found to be the most suitable material for 
the purpose. A pair of carbon electrodes of proper diameter to maintain a 
steady arc with a given current strength and voltage drop, will consume 
at the approximate rate of 1.25 inches per hour in open arc lamps, and .16 
inch per hour in those of the enclosed type. If cross section of the carbon 
be too large, the arc crater will cover a comparatively small part of the 
carbon point. The shifting of the arc moves the crater to a cooler point, 
which makes a considerable change in the resistance of the arc. This 
change is so rapid that the lamp mechanism cannot compensate for it as 
quickly as required, hence a variation in the candle-power of the lamp 
which makes the use of carbons of large diameter impractical. With car- 
bons of too small cross section, the candle-power is greater, and the arc is 
very steady, but the life of the electrodes is too short for practical purposes. 

In Europe, the practice is to use carbons of comparatively small diameter, 
of extra length, or to trim often in order to secure perfectly steady illumi- 
nation at maximum efficiency. In the United States, the practice has 
been to use carbons of larger diameter, giving longer life with one trim and 
limiting the length of the carbon to about twelve inches, thereby reducing 
the cost of the carbons and labor required, but sacrificing steadiness of 
illumination and efficiency. 

Developments have been made in the manufacture of carbons for the 
flaming arc for open arc lamps, which have more than doubled their effi- 
ciency, and give four times the efficiency of the enclosed arc. The intro- 
duction of arc lamps with electrodes placed points downward at an angle 
to each other (instead of one above the other as in the old style of lamp) 
makes it possible to use carbons over twenty-four inches long, if necessary, 
without making the lamp impracticably long. 

The metallic oxide electrode has also been successfully developed, and 
open arc lamps commonly known as "magnetite" lamps have been put on 
the market and show a marked increase in efficiency over that of the 
enclosed arc. 

There are seven governing factors to be considered by the designer of arc 
lamps: 

1. Steadiness of the light. 

2. Watt consumption per useful candle-power. 

3. Maximum practical length of the electrodes. 

4. Length of life with one trim. 

5. Cost of the electrodes. 

6. Cost and reliability of the lamp. 

7. Adaptability of lamp to the several systems of electrical distribution 
in general use. 

(ri^IIKATlOX Of ARC liAUEPS. 
Open Arcs, Direct Current : 

Ordinary open arc lamp with carbon electrodes. Series or multiple, 
6 to 10 amperes, 45 to 50 volts at terminals for constant current series; 
50 to 60 volts at terminals for constant potential multiple or multiple series 
operation. Life of carbons, 10 to 14 hours, approximately .6 watt per 
candle-power, clear globe. 

"Magnetite" arc lamp with metallic oxide electrodes in series only od 



ARC LAMPS AND ARC LIGHTING. 569 

constant current, 4 amperes, 75 to 80 volts at terminals. Life of elec- 
trodes, ) 60 \iours, approximately .3 watt per candle-power, clear globe. 

''FlarniLq:'' arc lamp, carbon electrodes with chemical core filling. Series 
or multip/1, 8 to 12 amperes, 45 to 50 volts at terminals for constant current 
series; 5^ to 60 volts at terminals for constant potential multiple or mul- 
tiple ser'.BS operation. Life of carbons, 10 to 18 hours, approximately .22 
watt p^r candle-power yellow flame, approximately .3 watt per candle- 
powe", white flame, clear globe. 

Open Arcs, Alternating: Current: 

Ordinary open arc lamp with carbon electrodes in multiple only, 10 to 16 
amperes, 40 volts at terminals — minimum practical frequency - — 60 cycles. 
Life of carbons 1\ to 12 hours, approximately .75 watt per candle-power, 
clear globe. 

"Flaming" arc lamp carbon electrodes with chemical core filling. Series 
or multiple, 10 to 14 amperes, 40 to 45 volts at terminals for constant current 
series; 50 to 60 volts at terminals for constant potential multiple or multiple 
series operation; minimum practical frequency, 25 cycles. Life of carbons, 
10 to 16 hours, approximately .25 watt per candle-power, yellow flame; 
approximately .33 watt per candle-power, white flame with clear globe. 

Enclosed Arcs, IMrect Current : 

Ordinary enclosed arc lamp with carbon electrodes. Series or multiple, 
3 to 7^ amperes, 75 to 85 volts at terminals for constant current series; 
100 to 250 volts at terminals for constant potential multiple or multiple 
Beries operation. Life of carbons, 75 to 150 hours, approximately 1 watt 
per candle-power, clear globes. 

Enclosed arc lamp with inclined electrodes of pure carbon. Multiple 
operation, 8 to 10 amperes, 100 to 120 volts at terminals. Life of carbons, 
30 hours, approximately .45 watt per candle-power, clear globe. 

Enclosed Arcs, Alternating* Current t 

Ordinary enclosed arc lamp with carbon electrodes. Series or multiple, 4 
to 1\ amperes, 75 to 85 volts at terminals for constant current series; 100 to 
120 volts at terminals for constant potential multiple, or multiple series 
operation; minimum practical frequency, 40 cycles. Life of carbons, 70 to 
100 hours, approximately 1.33 watts per candle-power, clear globes. 

Enclosed arc lamp with inclined electrodes of pure carbon. Multiple 
operation, 10 amperes, 100 to 120 volts at terminals; minimum practical 
Frequency, 40 cycles. Life of carbons, 20 to 25 hours, approximately .6 watt 
per candle-power, clear globe. 



OPEI ARC I^AIflPS. 

Iow>Ten»on l^aiiip requires for most successful results high-grade 
carbons, cored positive and solid or cored negative. Lamps with either 
shunt or differential carbon feed-control, operate 2 in series on 100 to 125 
volts, direct-current circuits with any current adjustment between 6 and 
12 amperes. The arc should be set for an average of 42 volts, and sufficient 
resistance must be introduced in series with each pair of lamps to make up 
the difference between the required lamp voltage and the voltage of the 
supply circuit. Attempts have been made to operate from 4 to 10 lamps 
in series on constant potential circuits of 200 to 600 volts, but with only 
partial success. 

On alternating current the low-tension open-arc lamp requires a very 
high grade of carbon both cored and of the same diameter and length. 

The following are the best dimensions for the carbons: 

Ten amperes, 94 X \ inches; 14 to 16 amperes, 9£ X I' inches giving 
about 10 to 12 hours' life. 

The alternating current, open arc lamp requires about 30 volts at the 
arc with 35 to 40 volts at the terminals. The carbon feed is controlled by 
a simple magnet connected in series with the arc. The lamp is, therefore, 
a strictly multiple, 35 to 40-volt lamp, and requires special means for pro- 



570 ELECTRIC LIGHTING. 

viding this pressure. For large installations a special transformer reduc- 
ing to about 35 volts is used. Where only a few lamps are required a 
small ("economy") single-coil transformer with taps for one, two, or three 
lamps is used. 

The illumination from the open arc, alternating current lamp has never 
been altogether satisfactory, mostly on account of low candle-power, exces- 
sive amount of violet rays, and noise. 

The low-tension, open arc lamp has not been in general use in the United 
States since 1900, having been superseded by that of the enclosed type. 
In Europe, however, this form of lamp has been in use until quite recently, 
as the enclosed arc was never very generally adopted there. The flaming 
arc lamp is now, however, replacing many of the other forms of open arc 
lamps. 

Hisrti-TViiMion lamp requires ordinary grade carbons, both of which 
may be solid, although in some cases it is of advantage to use a cored posi- 
tive. The usual carbon dimensions are, for 6 to 7 amperes, 12 X /* inch 
upper and 7 X ie inch lower; and for 9 to 10 amperes, 12 X \ inch upper 
and 7 X i inch lower. This is a strictly constant current series lamp 
operating any number in series up to the capacity of the generator. Con- 
stant current series arc generators have been built for single circuits of 175 
to 200 lamps, requiring as much as 10,000 volts. Later practice is to build 
generators for 100 to 150 lamps, but bringing out leads for several circuits, 
thus reducing the maximum potential of the system and still securing the 
benefits due to the use of fewer and larger generators of higher efficiency. 
The brush multi-circuit arc generators, as built by the General Electric 
Company, represent the latest development in large arc-lighting units for 
direct current series lighting. 

The high-tension lamp has either shunt or differential carbon feel and is 
built for 6.8 amperes with 42 to 45 volts at the arc, usually rated at 1200 
nominal candle-power; and for 9.6 amperes with 45 to 50 volts at the arc, 
rated at 2000 nominal candle-power. The high-tension series open arc 
lamp, operating on direct-current arc generators was the standard for street 
lighting in the United States until about 1900, since which time many of 
them have been replaced by enclosed arc lamps. 

The " magnetite " Arc Lamp is of the high-tension, direct-current, 
open-arc type metallic oxide electrodes. It is especially designed for outdoor 
lighting, to which it is limited on account of the fumes and heavy deposit 
from the electrodes. The positive electrode is made of pure copper, or from 
copper in combination with small non-conducting particles. Another 
form of positive electrode for this lamp is made of convoluted strips of 
laminated copper and iron, and is 1 inch long by \ inch diameter. The nega- 
tive electrode consists of a steel tube, tightly packed with a fine powder, 
the principal ingredients of which are: oxide of iron (magnetite), oxide of 
titanium and oxide of chromium. The steel tube serves as a conductor for 
the current to the crater and is also the holder of the oxide powder, making 
a binder unnecessary. The oxide of iron gives conductivity to the fused 
mixture when cold, the other oxides being conductors only when hot. The 
titanium oxide has the property of rendering the arc luminous. The oxide 
of chromium prevents too rapid consumption, thus giving long life to the 
electrode. 

Unlike all other arc lamps the maximum illumination in the "Magnetite" 
lamp comes from the negative end of the arc. The General Electric Com- 
pany have designed their "Magnetite" lamp with the negative electrode 
below the positive, while the Westinghouse Electric <fe Manufacturing Com- 
pany place the negative electrode above in their metallic oxide lamp. Ad- 
vantages are claimed for both forms of construction. An electrode having 
12 inches to burn will last about 150 to 175 hours. The positive electrode, 
of copper, although only one inch long, is generally renewed but once a 
year. 

The metallic arc electrodes, being chiefly composed of oxides of iron 
titanium and chromium, do not burn away to an invisible gas, as does a 
carbon stick, but are volatilized bodily, and the vapors instantly condense 
on leaving the arc to a fluffy reddish soot. This soot if allowed to come 
in contact with the reflectors or globes will smudge them badly in a few 
minutes. It will also condense and settle on the electrodes, hiding the light, 
so special means are introduced for carrying it off. Air currents are 
saused to circulate past the arc, under the reflector and within the globe 



ARC LAMPS AND ARC LIGHTING. 



571 



in such a manner that all soot deposit is carried up through a chimney in 
the center of the lamp and out in the open air. The success of the "Mag- 
netite" lamp depends to a large extent upon the creation of air currents 




Non Luminous 
Bright 
Fused Slag 
Reflection 




Bright Reflection 

-Non Luminous 

Non Luminous 




Bright 



Fig. 34. A. Metallic Arc, with negative below. B. Candle flame. 
C. Metallic Arc, with negative above. 

within the globe, and it has been a great problem to get sufficient natural 
circulation and to control it with the short chimney permissible in an arc 
lamp. 




"^j 



Fig. 35. General Electric Co. 's Magnetite Arc Lamp. 



The "Magnetite" lamp has a white dazzling arc of great intensity, but 
rather small volume. The candle-power is greatest at 10 degrees to 20 
degrees below the center line of the arc. This fact makes it especially 



572 



ELECTRIC LIGHTING. 



valuable for street lighting. For this purpose the "Magnetite" lamp is 
built for 4 amperes and adjusted for about 78 volts at the arc. The elec- 
trode is fed intermittently by a shunt cut-out coil which causes the mechan- 
ism to restrike the arc. This form of 
feed is practical for a constant cur- 
rent series system, but will not per- 
form properly on constant potential 
circuits. The efficiency of the lamp 
is about 98 per cent. 

The "Magnetite" lamp may be 
operated in series on constant direct 
current, derived from a constant 
current arc generator or from the 
mercury arc rectifier in conjunction 
with a constant current transformer 
or automatic reactive coil supplied 
from constant potential alternating 
current generators. 

The cost of the "Magnetite" 
system (1907), including C.C. Trans- 
former, mercury rectifier with start- 
ing transformer, switch panel and 
lamps is about $53 per lamp. 

The cost of the negative electrode 
is S50 per M. 

The positive electrode in the 
General Electric lamp lasts 4000 
hours and costs 45 cents each. 

The full load efficiency of the 
entire system, taken at the prim- 
ary of the constant current trans- 
former, is 85 to 90 per cent, and 
the power factor is about 65 per 
cent. 

flaming; Arc I- amps. — From 
time to time since 1890 it has been 
proposed to impregnate carbon elec- 
trodes for arc lamps, so as to add 
metallic vapors to the arc, thereby 
greatly increasing its size and bril- 
liancy. Several methods of combining metallic salts with the carbon have 
been tried, but great difficulty has been experienced in securing a uniform 
mixture, which would consume evenly without the formation of slag 
which would eventually interrupt the service of the lamp. Hugo Bremer 
of Neheim, Germany, has secured a number of patents on special electrodes 
for arc lamps, composed of "an intimate mixture" of carbon and metallic 
salts or metalloids, as calcium, magnesium, glass, fluor-spar, or the like. 
Mr. Bremer has also developed a line of arc lamps for his special electrodes. 
It has been found by experience that the Bremer electrodes are difficult to 
operate, and the lamp rather complicated in order to remove the insulating 
slag formation and insure good contact between the electrodes when cold. 
The carbon manufacturers appreciating the great commercial value and 
efficiency of the flaming arc have developed a line of cored carbons, the shell 
of which consists of carbon, the core being made up of a mixture of pow- 
dered carbon, mineral salts and a suitable binder. This electrode has 
absolutely removed the difficulty from the slag formation with the Bremer 
electrode, allowing the use of very simple arc lamps arranged to feed the elec- 
trodes with points downward at an angle towards each other. Careful 
tests prove the watt efficiency of the flaming arc to be about eighteen times 
that of the ordinary incandescent lamp, three times that of the ordinary 
open arc, and six times that of the enclosed arc. The intrinsic brilliancy of 
the arc flame is about one-third that of its positive and negative craters. 
The candle-power distribution in the flaming arc is approximately as fol- 
lows: Positive crater, 20 per cent; negative crater, 5 per cent; and the arc 
flame, 75 per cent. 

By placing the carbon points downward, maximum illumination is 
obtained from the craters without interference and shadows. If the arc 




Fig. 36. Westinghouse Elec. & Mfg. 
Co.'s Metallic Oxide Arc Lamp. 



ARC LAMPS AND ARC LIGHTING. 



573 



voltage is maintained too high, which means a large carbon separation, the 
mist around the arc flame will be excessive and interfere somewhat with 
the light from the craters. The flaming arc becomes unsteady at voltages 
above 40 on alternating current, and 45 on direct current. By reason of the 
fact that the arc is at the lower end of the two electrodes, with points down- 
ward, it becomes necessary to provide means for maintaining it at the 
extremity of the points, as otherwise the heat of the flame will induce an 
upward draft which will carry the arc up between the electrodes, soon 
hiding the craters and preventing proper combustion. It is well known 
that the electric arc may be controlled by magnetic lines of force. This 



//Q-/2S Vo/C A,C. Source 

JL/$ht<s 
Open C/rcuftfnjj P/ug Skv/tcn ^/^ 



Fuse 



u 



* L/$ntn/n<$ % 
Arrester 




Start /n^ 
Transformer 



Constant Current 
Transformer w/th 
Reactance 

80 Jl Loacf Tap-+\ 

/OOJL Loacf Tap 



Short C/fca/t/h0 
P/ap Stv/tch 



Pose 

Pr/mary Pfug 
Switch 



To 2200Vo/t A.C. Source 

Fig. 37. Diagram Connections G. E. Magnetite Arc Lighting System. 



principle has been taken advantage of in the flaming arc lamp, which is pro- 
vided with a "blow-down coil" having the iron circuit so arranged that the 
arc flame is forced downward, as if held in a downward draft of air. The 
magnetic control of the flame makes the arc self-regulating, which makes it 
unnecessary to use complicated mechanisms for maintaining the current 
constant. A fixed carbon separation, with some means for feeding the 
carbons and maintaining the arc length constant, is all that is required. 

The large arc flame having an area of about \ inches square, furnishes 
75 per cent of the illumination. This great tongue of light is forced down 
towards the center of the globe, which is preferably made of light alabaster 
glass, illuminating it at a high intensity and without shadows. The ilium- 



574 ELECTRIC LIGHTING. 

ination from the flaming arc lamp with light alabaster globe is practically 
uniform in all directions, beginning about 10 degrees above the horizontal 
center line of the arc. The downward illumination is slighty greater, due 
to the light from the craters, but as the flame throws the greater part of its 
light in the horizontal direction, the practical result is uniform illumination 
of the entire globe. Flaming arc lamps should be hung high, 20 to 60 feet 
above the floor or street level, excepting for advertising purposes where they 
may be hung lower. If the lamps are placed 50 feet above the floor and 100 
feet apart, a practically constant and uniform illumination of great intensity 
will be the result. 

The Constant Potential I>. C. Flaming- Arc lamp requires 50 
to 60 volts at the terminals and is adjusted for 45 volts at the arc. One lamp 
operates in multiple on 50 to 60 volts, two lamps in series on 100 to 125 
volts, four on 250 volts, ten on 500 volts, twelve on 600 volts, and fifteen on 
750 volts. When more than two lamps are to operate in series, an external 
automatic cut-out with equalizing resistance must be put in multiple with 
each lamp to protect it against excessive voltage. The standard amperage 
is 10 to 12; the positive carbon is 10, and the negative 9 mm. in diameter. 
A pair of carbons 500 mm. long give 12 hours' life outdoors and 13 to 14 
hours indoors; the 600 mm. carbons give 16 hours outdoors and 18 hours 
indoors. 

The Constant Potential A. C. Flaming* Arc lamp requires 
50 to 60 volts at the terminals and is adjusted for 38 to 40 volts at the arc. 
One lamp operates in multiple on 50 to 60 volts, or two in series on 100 to 120 
volt circuits. When one lamp is to operate in multiple on 100 to 120- volt 
circuit, a small auto-transformer is required to reduce the voltage to 50 or 
55. Similar auto-coils should be used when lamps operate on 200 to 460- 
volt systems. When a large number of lamps are to be used a regular three- 
wire system can be installed with 55 volts between each outside wire and 
the center wire. One large transformer reducing from the primary poten- 
tial to 110 — 55 volt three- wire system — should be installed, allowing the 
flaming arc lamp to operate in multiple on 55 volts without loss and extra 
expense for separate auto-transformers or other compensators. The flam- 
ing arc lamp will operate successfully on any frequency from 25 to 140 
cycles. Below 40 cycles, lamps should always be operated in multiple on 
55 volts. The standard current adjustment is 12 amperes. The carbons 
are both 9 mm. in diameter. The 500 mm. carbon gives 10 to 11 hours 
outdoors and 11 to 12 hours indoors. Carbons 600 mm. long give 13 to 15 
hours outdoors and 14 to 16 hours indoors. The alternating current lamp 
is practically noiseless and gives a very steady illumination. The efficiency 
of the alternating current flaming arc lamp on constant potential is about 
80 per cent and the power factor about 90 per cent. The efficiency and 
quality of the illumination compares favorably with that of the direct current 
lamp, which is an important point in favor of the flaming arc lamp for alter- 
nating current circuits. 

The Constant I>. C. Series Flaming* Arc Lamp requires 45 volts 
at its terminals and is adjusted for 43 volts at the arc. The lamp is iden- 
tical in construction with the direct current constant potential lamp, but 
requires no resistance in series with the arc. An automatic cut-out is used 
with each lamp to shunt the current in case the carbons should stick or be 
prematurely consumed. The lamp can be operated in series on the regular 
9.6 ampere arc dynamos used for the ordinary high-tension open arc lamps. 
The mercury arc rectifiers with constant current transformers can also be 
used to supply current for the direct current flaming arc lamp. As a matter 
of fact, it may be operated in series with the old style, high-tension, open arc 
lamp. The size and life of the carbons is the same as for the direct current 
constant potential lamp. 

The Constant A. C. Series Flaming* Arc Lamp requires 40 
volts at the terminals and is adjusted for 38 volts at the arc. The constant 
current lamp is practically the same as that for constant potential, but is 
provided with an automatic cut-out to shunt the current. The lamp oper- 
ates with 10 to 12 amperes in series on constant current circuits controlled 
by constant current transformers or automatic reactive coils. As present 
alternating current series circuits for street lighting carry only 4 to 7£ 
amperes, it is necessary to install with each lamp on such circuits a small 
series transformer or series auto-coil which will deliver from its secondary 
10 to 12 amperes at 40 volts to the lamp. In conjunction with series Tung- 



18 to 


K.JKJH. 

20 


30" 


35 


50" 


60 


75 " 


90 


90" 


100 


,25 '• 


150 



ENCLOSED ARC LAMPS. 575 



sten lamps, operating on the same circuit, the entire street lighting field 
can be covered, furnishing both large and small units from the same wires. 
The size and life of the carbon is the same as for the constant potential 
alternating current lamp. 

The 500 to 600 watt direct current flaming arc lamp, with yellow flame 
carbons, gives approximately 2700 mean spherical candle-power; white 
flame carbons give about 2000 candle-power. 

The candle-power of the alternating current flaming arc lamp is about 
10 per cent less than that given for the direct current lamp of the same 
watt consumption. 

Searchlight Projectors and focusing lamps for theatrical use and 
for photo-engraving, etc., take large and varied quantities of current, as 
they are always connected across the terminals of constant potential cir- 
cuits, with a regulating resistance in series with the lamp. The General 
Electric Company state in one of their bulletins the following as being the 
approximate currents taken by the different sizes of searchlights: 

Diam. of Projector. 

12 inch 

18 " 
24 " 
30 " 
36 " 
60 " 



EICLOMEO ARC IjAJKPS. 

It has been found that by enclosing the arc in a small globe, more or less 
approaching air-tight conditions, combustion of the carbons is practically 
complete, leaving no dust, and takes place at a slow rate, burning with a 
12 X i-inch carbon 75 to 100 hours without attention. The enclosed arc 
cannot be properly maintained below 65 volts, and 70 to 75 volts is the usual 
arc potential for alternating current lamps, and 75 to 85 for the direct 
current lamp. The minimum current is 3 and the maximum for enclosed 
arcs is 1\ amperes. 

The long arc, low amperage and enclosing globe all tend to lower the 
illuminating efficiency of the enclosed arc lamp, but notwithstanding this 
it has superseded most of the open arc lamps for general illumination. The 
long life of the carbon has greatly reduced the cost of trimming and the 
cost of carbon renewals. It permits the use of very simple mechanism, 
actuating a clutch which operates directly on the carbon. Enclosed arc 
lamps are made for all commercial circuits. 

Constant Potential ». C. Enclosed Arc Lamp requires 100 to 
250 volts at the terminals with 75 to 160 volts at the arc. The minimum 
amperage is 2\ and the maximum is 6. The 2\ to 4-ampere lamps use 
A to f-inch carbons. The 5 to 6-ampere lamps use & to ^-inch carbons, 
12 inches long, giving 75 to 150 hours life. Each lamp is fitted with a 
resistance coil, and is a complete unit for multiple connection on 100 to 
125 volts with 75 to 85 volts at the arc, or on 200 to 250 volts with 140 to 
160 volts at the arc. The constant potential lamp is controlled by a series 
magnet. If the lamp is provided with differential clutch controlling mag- 
net, automatic cut-out and equalizing resistance, it can be connected in 
series on constant potential circuits, as follows: 2 on 220 volts, 5 on 500 
volts, and 6 on 600 volts. 

Constant Potential A. C. Enclosed Arc Lamp requires 100 
to 125 volts at the terminals, and is adjusted for 70 to 80 volts at the arc. 
The amperage maybe anywhere between 4 and 1\. The alternating current 
constant potential lamp is not operated in series. The power factor of the 
lamp is about 70 per cent. The minimum frequency giving satisfactory 
illumination, is 50 cycles; and the maximum frequency, in general use, for 
which this style of lamp is built, is 140 cycles. The carbons are usually 
10 inches long X f to \ inch in diameter and give from 65 to 100 hours' 
life. 

When alternating current constant potential lamps are to operate on 



576 ELECTRIC LIGHTING. 

voltages above 125, an auto-transformer or other converter for reducing 
the voltage should be used. A reactive coil is also put in the top of the 
alternating current lamp. 

Constant I>. C. Series [Enclosed Arc Lamp requires 75 to 80 volts 
at the terminals. The arc is set for 73 to 78 volts. The amperage is between 
5 and 7, depending upon the candle-power desired. The lamp has differen- 
tial feed and is provided with automatic cut-out to shunt the current, if the 
carbon sticks or is consumed. The lamps operate in series on any constant 
current source of supply. The carbon is 12 X 2 inch and lasts about 100 
hours. 

Constant A. C. Series Enclosed Arc lamp requires 75 to 80 
volts at the terminals. The arc is set for 72 to 77 volts. The minimum 
amperage is 4 and the maximum is 1\. The feed control may be either 
shunt or differential. The carbon is 10 X \ inch and lasts 75 to 100 hours. 
Each lamp has an automatic cut-out. The lamps operate in series on con- 
stant current circuits, usually controlled by constant current transformers 
or automatic reactive coils. The efficiency of a complete system, including 
transformer and lamps, is about 85 per cent, and the power factor is between 
70 and 80 per cent at full load. The system operates on any frequency 
from 50 to 140 cycles. 

Method* of Regulation in Arc Lamps may be classified as 
follows: 

Carbons lifted or separated by direct or main magnet; shunt magnet 
acting on a variable resistance to cut out the main magnet in feeding. 

Carbons lifted by main magnet as before, and shunt acting to put the 
main magnet (made movable) into position for feeding. 

Carbons separated by main magnet armature; shunt circuiting magnet 
acting to divert or shunt the magnetism of the main magnet from its arma- 
ture. 

Carbons separated by main magnet and shunt acting to free the carbon- 
holder, independently of the support given by the main magnet. 

Carbons separated by a spring allowed to act by the main magnet lifting 
a weight which otherwise holds the spring from acting; shunt magnet acts 
against the spring, to feed and regulate the length of arc. 

One carbon, generally the lower, separated by main magnet, while the 
other holder is released for feeding only, such feeding being under the con- 
trol either of a differential system or a shunt magnet only. 

Carbons separated by main magnet, which lifts the shunt and its arma- 
ture together, while the shunt magnet armature, acting on the feeding 
mechanism, controls the arc and feed of the carbons. 

Carbon feeding mechanism independently attached to main magnet arma- 
ture and to shunt armature so as to receive opposite movements of separa- 
tion, and feed from each respectively. 

Carbons separated by a feeding mechanism moved by the main magnet, 
and fed by a further movement of said mechanism, causing release or re- 
turn of same under the accumulated force of both shunt and main magnets, 
acting in the same direction. 

Differential clock gear for separation and feed of carbons under control 
of the regulating magnet system, either simple or differential. Some of the 
older clock-work lamps embodied this principle. 

Carbons controlled by armature of a small electric motor under control of 
a differential field which turns the armature in one direction for separating 
and in the other or reversed direction for feeding the carbons. 

Carbons controlled by a motor running at a certain speed when the arc is 
of normal length, and varying in speed when the arc is too short or too long, 
combined with a centrifugal governor on the shaft of the motor, acting on 
variations of speed to gear motor shaft to screw carbons together or apart, 
as needed to maintain the normal arc. This mechanism has been applied 
to large arc lamps, such as naval searchlights, and has the advantage of 
great positiveness, and an ability to handle heavy mechanism. 

There are also a considerable number of modifications of these principles. 



ENCLOSED ARC LAMPS. 577 

Tents for Arc Ug-lit Carbons. 

For Open Arcs. 

The satisfactory working of arc lamps is largely dependent upon the 
quality of the carbons used. If carbons are made of impure materials, they 
will jump and flame badly. If not baked properly, they may cause annoy- 
ance by excessive hissing or flaming, or become too hot because of high 
resistance. If the material of which they are made has not been properly 
prepared in its preliminary stages, the carbons will have either too short a 
life, through giving a good quantity and quality of light, or will have good 
life, but will burn with an excessive amount of violet rays, hence with poor 
illumination. 

For indoor use a free-burning, uncoated carbon of medium life should 
be used, so as to give a good quality and quantity of light. If longer life is 
desired they may be lightly coated with copper without materially interfer- 
ing with the light. (About 1| lbs. to 2 lbs. of copper per thousand, /g" x 12" 
carbons, and a half pound more for \" x 12" carbons will give good results, 
increasing the life from an hour to an hour and a half.) 

For out-door use a more refractory burning carbon may be used to advan- 
tage, giving a longer life, as the quality of the light is not so important. 
Copper-coated carbons are also usually employed, and may have about four 
pounds of copper per thousand for /g" x 12" carbons, and five pounds for 
|" x 12". Other sizes in proportion. 

All plain molded carbons, and most of the forced carbons, deposit dust 
when burned in the open arc. Those depositing the most dust give out the 
most light, but have the least life. Those depositing the least dust usually 
have the longest life, but the light is of inferior quality on account of the 
increase in the proportion of violet rays. 

The quality of any carbon may be very quickly tested in any station by 
using the following method, which has been largely employed by carbon 
manufacturers. 

The important points to be determined are therang-e, including the hiss- 
ing, jumping, and flaming points, the resistance, and the life. 

The Xtangre is found by trimming a lamp with the carbons to be tested, 
allowing them to burn co good points and the lamps to become thoroughly 
heated; then connect a voltmeter across the lamp terminals, and very 
slowly and steadily depress the upper carbon until the lamp hisses, when 
the voltage will make a sudden drop. This is called the Hissing-Point, 
and varies according to the temper of the carbon. It should be between 40 
and 45 volts — preferably 42 volts. Then lengthen the arc somewhat, and 
allow it to become longer by the burning away of the carbons. Presently 
the arc will make small jumps or sputters out of the crater in the upper 
carbon. This is the Jumping*- Point, and should be not less than 58 or 
60 volts. Let the arc still increase in length, carefully watching the volt- 
age, and in most carbons there will soon be a decided naming. This is the 
flamingr-Point. This should not be less than 62 to 65 volts. Very im- 
pure carbons will commence to jump and flame almost as soon as the volt- 
age is raised above the hissing-point, and even the hissing-point in such 
cases is very irregular and difficult to find. The Range is important as 
being a practical test of the purity of the material used in the manufacture 
of the carbon, an increase of a quarter of one per cent of impurity making 
a very decided reduction in the extent of the Range. The hissing-point 
should be 4 or 5 volts below the normal adjustment of the lamp to insure 
steady burning. 

Resistance. — The resistance is measured on an ordinary Wheatstone 
bridge. Care must be taken that the contact points go slightly into the 
carbon. A T 7 g " x 12" plain carbon should have a resistance of between .16 
and .22 ohms, and £" x 12" between .14 and .18 ohms. T 7 B " x 12" carbons coated 
with three pounds of copper per thousand, have a resistance between .05 and 
.06 ohms, and \[* x 12" with four pounds of copper between .04 and .05 ohms. 

JLife. — The life of a carbon is most easily tested by consuming it 
entirely in the lamp, observing, of course, the current and average voltage 
during the entire time. A very quick and accurate comparative test of dif- 
ferent carbons can be made, however, by burning the carbons to good points, 
then weighing them, and let them burn one hour, then weigh them again. 
The amount burned by both upper and lower carbons shows the rate of 
consumption which will accurately indicate the comparative merits of the 
carbons tested as to life. 



578 



ELECTRIC LIGHTING. 



To calculate the life from a burning test of one hour, both carbons should 
be first weighed, the upper carbon broken off to a 7-inch length, in order to 
make the test at the average point of burning, and with the lower carbon, 
burned to good points, weighed again, and after burning one hour in a 
lamp that has already been warmed up, taken out and weighed. The 
amount of two carbons 12 inches long consumed in a complete life-test is 63 
per cent of the combined weight of both upper and lower carbons. There- 
fore 63 per cent of the weight of the two carbons, divided by the rate per 
hour obtained as above, will give the life approximately. 

Dust. — The dust from burning carbons can be collected in the globe, or 
better, in a paper bag suspended below the lamp. In an ordinary plain 
molded carbon this dust amounts to 4 per cent of the weight of the upper 
carbon. A variation below this amount will indicate good life, but inferior 
light. An excessive amount of dust would show a short life, but usually a 
good quantity and quality of light. Coating a carbon with copper eliminates 
this deposit of dust entirely. 

Enclosed Arc Carbons. 

Carbons for enclosed arcs can be very conveniently tested as to their rel- 
ative values in an open arc lamp as described above. As their diameters 
regulate the admission of air to the inclosing globe, thus greatly affecting 
their life, they should be carefully measured with micrometer calipers. A 
greater variation than .005 inch from the required diameter should not be 
permitted. The deposit on the inside of the inclosing globe is caused by 
impurities, principally in the core. The relative injurious amount of this 
deposit can be measured by carefully taking the globes off the lamps after 
burning, and measuring the amount of light absorbed by them with an 
ordinary photometer, using an incandescent lamp as a source of light, and 
cutting the light down by means of a hole in a screen so that it will pass 
through the part of the globe to be measured. Twice the light so measured 
through the globe, divided by the amount coming through the unobstructed 
hole, will give the per cent of the light transmitted through the globe from 
the arc. That carbon whose globe absorbs the least amount of light is, of 
course, the most desirable. 

The resistance of forced carbons, whether cored or solid, used in inclosed 
arc lamps, is very important. Carbons of high resistance are difficult to 
volatilize, and hence there is trouble in establishing the arc where small 
currents are used, and in case of any interruption in reestablishing it after- 
wards. This is especially true of carbons used in alternating arcs, and of 
cored carbons. The resistance of forced carbons is usually much higher 
than that of molded, ranging from two to four times as much. This will 
undoubtedly be corrected when the manufacturers become more familiar 
with the requirements. The lower the resistance the better the quality of 
the light and the operation of the lamp. 



Sizes of Carbons for Arc Lamps. 


Open Arcs. 


Continuous Current. 


Upper. 


Lower. 


6.8 amperes 
9.6 " 
9.6 " 
9 . 6 amperes * 
9.6 M 


12 in. X A in. 
12 •• X I " 
12 •• X f " 

12 in. X A in. X I in. 

llf "Xi"Xl u 


7 in. X i 7 s in. 
7 " X * " 
7 ** X 1 '* 

6f in. X t 7 s in. X 1 in. 

7i " X * " XI " 




Alternating Current. 


15 amperes 


9£ in. X f in. | 9£ in. X S in. 



Enclosed Arcs. 



Continuous Current. 



5 amperes 
3 amp eres 



12 in. X h in. 

12 " XI " 



5i in. X £ in. 
6 "XI" 



* These are elliptical in cross section, for higher candle-power and longer 
burning. 



ENCLOSED ARC LAMPS. 



579 



Carbons Recommended for Searchlight Projectors. 

(Columbia or Hardtmuth or Schmeltzer.) 



Size of Lamp. 


Positive. Cored. 


Negative. Cored or 
Solid. 


9 


inch 


5i in. X h in. 


3i in. X fs in. 


13 


" 


6 


1 X f " 


4* 4I X * 44 


18 


44 


8* 


• X H" 


5 " X f " 


24 


44 


12 


4 X 1 " 


7 " X t 44 


30 


■• 


12 


• X 1* M 


7 44 X I 44 


36 


" 


12 


• X U " 


7 " XI 44 


48 


44 


15 


4 xitt" 


12 "XI A 44 


60 


" 


15 " X 2 " 


12 " XU" 



Carbons Recommended for Automatic and Hand-Feed 
focusing: Lamps. 



Continuous Current. 




Amperes. 


Positive. Cored. 


Negative. Solid. 


5 to 10 
10 " 18 
18 " 20 
25 " 30 


6 in. X & in. 
6 " X f " 

6 " X f " 
6 " X I " 


6 in. x t 7 5 in. 
6 " X h " 
6 " X I " 

6 " X 1 " 


Alternating Current. 




5 to 10 
10 " 18 
18 '• 20 
25 " 30 


6 in. X & in. 
6 " X * " 
6 " X f u 
6 " X i " 


Same as for Positive. 



Candle-power of Arc Lamp*. 

The candle-power of an arc lamp is one of the most troublesome things to 
determine in all electrical engineering ; the variations being great the arc 
unsteady, and the implements for use in such determination being so liable 
to error. Again, what is the candle-power of an arc lamp, or rather, what 
is the meaning of the term ? 

When the lamp was first put forward, for some reason, now in great ob- 
scurity, the regular 9.6 ampere lamp was called 2000 candle-power, and it 
has always since been so called, although the word " nominal " has been 
tacked on to the candle-power to indicate that it is a rating, and not an 
actual measurement. 

The candle-power of the arc varies with the angle to the horizon on which 
the measurement is made ; in continuous current arcs the maximum can- 
dle-power is at a point about 45 degrees below the horizontal if the upper 
carbon is the positive, and of course above the horizontal if the negative 
carbon is above. 

In alternating current lamps there are two points of maximum light, one 
about 60 degrees above the horizontal, and the other about the same angle 
below the line, and the mean horizontal intensity also bears a greater ratio 



580 



ELECTRIC LIGHTING. 



to the mean spherical intensity than in the direct current arc. In the 
alternating current arc much of the light is above the horizontal plane, 
and it is necessary to arrange a reflector above the arc to throw that portion 
of the light downward. 

Mean Spherical Candle-power is the mean of the candle-power 
measured all over the surface ot a sphere of which the arc is the center, 
usually about one-third of the maximum candle-power. In practice the 
spherical candle-power is seldom fully determined, but a fair approximation 
may be had by the following formula : 

Let 



Then 



S = mean spherical candle-power, 
H— horizontal candle-power, 
M = candle-power at the maximum. 
H M 

s ~-2 + T' 



In a test of arc lamps in November, 1889, for the New York City Bureau 
of Gas, Captain John Millis found the following results in his trial of the 
Thomson-Houston lamps. 

The same lamp was used, but connected to the different street circuits, all 
measurements were made at 40 degrees below the horizontal, and ^g-mch 
copper-plated carbons were used. 

Ten readings were taken on each of four sides of the lamp when con- 
nected to each circuit, with the following results : 





Candle-power. 


Watts 


Circuit No. 1. 


2072.7 


482.88 


" " 2. 


1981.0 


485.10 


" " 3. 


2048.5 


493.22 


44 41 4# 


2000.2 


494.40 


44 44 5. 


2067.0 


495.36 


Means 


2033.9 


490.19 


Mean current, amperes 
Mean volts .... 




. . e 10.36 




. . . 47.32 



The results of tests of candle-power of arc lamps at the Antwerp Exposi- 
tion, shown in the table below, would tend to verify the above trials. 







Maxi- 
mum 
C.P. 




Upper 


Lower 






Am- 
peres. 


Volts. 


Horizon- 
tal C.P. 


Hemi- 
sphere 


Hemi- 
sphere. 


Mean 
C.P. 


Watts. 








Mean C P. 


Mean C.P. 






4 


37.2 


390 


74 


17 


119 


136 


157 


6 


46.2 


1090 


168 


63 


298 


361 


259 


6.8 


46 


1240 


240 


65 


320 


385 


313 


8 


46 


1550 


334 


70 


385 


454 


350 


10 


45.5 


2070 


421 


102 


640 


750 


491 



Arc liig-ht Efficiency. — The light efficiency of an arc lamp is 
the ratio of its mean spherical candle-power to the watts consumed between 
the lamp terminals. Some energy is used up in the lamp-controlling mechan- 
ism, in the carbons themselves, and the remainder is used on the arc. Arc 
lamp efficiency is sometimes described as the ratio of the watts used in the 
arc to the watts used between the lamp terminals. This is true of the lamp 
as a machine; but the first statement is the correct one, as it is fight that is 
turned out, and not watts consumed in the arc that is the object of the 
lamp, and the two depend so much on quality and adjustment of carbons, 
even with the same consumption of current, as to make the latter method 
erroneous. 



ENCLOSED ARC LAMPS. 581 



Seat and Temperature Developed by tbe Electric 
Arc. 

The temperature of the crater, or light-emitting surface of the arc, is the 
same as the point of volatilization of carbon, and therefore constant under 
constant atmospheric pressure. This temperature is variously stated by 
different investigators: Dewar gives it as 6000° C; Rosetti, the positive as 
3200° C, and the negative 2500° C. 

The carbon in the crater is in a plastic condition during burning; and with 
the same adjustment of carbons, as to length of arc, the light per unit of 
power increases with the current. 

Hissing, naming, and rotating of the arc are some of the defects. Hissing 
is due to a short arc, and was a constant accompaniment of the low poten- 
tial, high current arc so prevalent during the earlier days of arc lighting. 

Flaming and rotating in open arc lamps are due to long arcs and to impure 
carbons, or carbons not properly baked. 

With good carbons the length of arc, or distance between carbon tips 
for open arcs direct current, continuous current lamps, should be, for 6.8 
ampere lamp, & inch; and for 9.6 or 10 ampere lamps, is to 3 j inch. 

Balancing' Resistance for Arc Stamps on Constant 
Potential Circuit. 

As the ordinary arc lamp takes but 45 to 50 volts, when used on constant 
potential circuits of more than 50 volts, it is necessary to introduce a cer- 
tain resistance in series, in order, first, to take up part of the voltage, and 
second, to act in a steadying capacity to the arc; in fact, until the dead 
resistance was introduced in series with the arc lamp on constant potential 
circuits, such lamps were entirely unsuccessful. 

Prof. Elihu Thomson says, "a certain line voltage as a minimum is abso- 
lutely necessary in working arc lamps on constant potential lines, whether 
they be open arcs or enclosed arcs. Thus two 45- volt arcs in series, with 
uncored carbons like the brand known as 'National,' cannot be safely 
worked below 110 volts on the line without resistance in series with them. 
More than 100 volts should, of course, be maintained for safety of the 
service. 

M The tests show, also, that with a cored upper carbon, the limit is lowered 
several volts on the average, and it is known that the voltage of the arcs 
may be safely reduced somewhat when cored positives are used. 

"It is also shown that a 75 to 80- volt enclosed arc, run upon a constant 
potential line, is stable at a considerably less line voltage than the open arc. 
It would appear, also, that with either open or enclosed arcs at ordinary 
current strengths of from 5 to 10 amperes, the steadying resistance in the 
branch is required to cause a drop of about 15 to 20 volts, or waste energy 
at the rate in watts of 15 to 20, multiplied by the amperes of current used 
in the lamp." 

Let E = E.M.F. or difference of potential between the circuit leads. 

e = E.M.F. required at arc lamp terminals. 

i = current required by the arc lamp. 

R = dead resistance to be put in series. 

r = resistance of the arc lamp burning. 

r' = total resistance of dead resistance 4- lamp. 
Then 

r = -. (1) 

% 

r, = -r (2) 

x 

R = r, - r. (3) 

As the E.M.F. of most of the circuits on which lamps of this type are used 
is more than 100 volts, it is customary, and in fact economically necessary, 
to place two arc lamps in series, and the formula (3) then becomes, 

R = r, - 2r. 



582 



ELECTRIC LIGHTING. 



Street rig-htiiigr t>J Arc lamps. 

For good illumination, distance apart of arc lamps should not exceed six 
times height of arc from ground. 

For railroad yards, 10 ampere arc lamps 30 feet from the ground and about 
200 feet apart are found to give good results. 

The following table shows some arrangements of arc lamps in foreign 
cities: 



Arc Lamps in Foreign Cities. 


Amperes 
per Arc. 


Distance 
Apart in Ft. 


Height of 
Arc in Ft. 


City of London Streets . 
Glasgow Streets 






10 

10 

10 

• 15 

10 
15 
10 
10 
10 
10 
15 


115 
160 
300 
137 
80 to 100 

90 

180 

60 to 80 

75 

90 

33 

41 


17.6 
18.0 


Hastings Streets 




18.0 


Berlin Streets . .... 




26.7 


Milan Streets . 




25.0 


Charing Cross Railroad Station 
Cannon Street Railroad Station 
St. Pancras Railroad Station . 
Central Station, Glasgow 
St. Enoch's Station, Glasgow . 
Edinburgh Exhibition, 1886 
Edinburgh Exhibition, 1886 




18.0 
35.0 
14.0 
19.5 

12.6 
18.0 


] 


Dr. 


►ff 

B] 


by Grlol»c 

ELL. 


,S. 





With respect to porcelain and glass, the following table gives the general 
results obtained by several experimenters on the absorption of various 
kinds of globes, especially with reference to arc lights. 

Per cent. 

Clear glass 10 

Alabaster glass 15 

Opalescent glass 20 to 40 

Ground glass 25 to 30 

Opal glass 25 to 60 

Milky glass 30 to 60 



Too much importance should not be attached to this large absorption, 
since it has already been shown that in most cases, so far as useful effect is 
concerned, diffusion and the resulting lessening of the intrinsic brilliancy 
is cheaply bought, even at the cost of pretty heavy loss in total luminous 
radiation. 

The classes of shades commonly used for incandescent lamps and gas 
lights have been investigated with considerable care by Mr. W. L. Smith. 

The experiments covered more than twenty varieties of shades and re- 
flectors, and both the absorption and their distribution of light were inves- 
tigated. One group of results obtained from 6-inch spherical globes, in- 
tended to diffuse the light somewhat without changing its distribution, 
was as follows, giving figures comparable with those just quoted: 

Per cent. 

Ground glass 24 . 4 

Prismatic glass 20.7 

Opal glass 32.2 

Opalescent glass t 23.0 



ENCLOSED ARC LAMPS. 583 

The prismatic globe in question was of clear glass, but with prismatic 
longitudinal grooves, while the opal and opalescent globes were of medium 
density only. 

Etched glass has considerably more absorption than any of the above, 
the etching being optivally equivalent to coarse and dense grinding. Their 
diffusion is less homogeneous than that given by ordinary grinding, so that 
they may fairly be said to be undesirable where efficiency has to be seri- 
ously considered. 

Trimming; Arc LampN. 

One trimmer can handle the following number of lamps per day: 

Walking. Riding. 

Regular open double carbon street arcs .... 80 100 to 120 

Magnetite lamps 80 100 " 120 

Flaming arcs 80 100 " 120 

Enclosed arcs 50 100 

The number of commercial lamps which one man can trim depends so 
much upon local conditions that it is not possible to give any general figure. 



ILLUMINATING ENGINEERING. 

Revised by Dr. C. H. Sharp. 

The problem of the illuminating engineer may be stated in general terms 
as follows: to obtain the illuminating effect desired in any case with the 
maximum economy, having due regard to the protection of the eyes from 
disagreeable or harmful effects and to architectural and aesthetic consider- 
ations. 

Illumination may be direct, coming straight from the lamps which then 
are visible, or indirect, as when the lamps are hidden from view by a cornice 
and the illumination is due to the light reflected from a cove above. 

Measurements of candle-power values are horizontal, vertical and normal 
illuminations, according to the position of the plane of reference, horizontal, 
vertical or normal to the light rays. 

Curves of illumination have as their abscissas distances from the source 
of light measured along a horizontal line and as their ordinates intensities 
of illumination. If the vertical distribution curve of the source of light is 
known the corresponding illumination curves can be computed according to 
the following equations, in which E is the illumination, h the height of the 
lamp above the plane of reference, I the distance from the point in question 
to the point immediately beneath the lamp, and Iq the intensity of the 
lamp at an angle with the vertical 



: A* + p 

Iq COS Iq h Iq cos 8 



Eh = 



Ev = 



Iq sin IqI I 

h 2 + P (h* + P)t ~ h 



sin* 



In considering the availability of any source of light due regard must be 
given to the proper selection of shades, reflectors, etc., which may be used 
in connection with it. These appurtenances serve the following purposes: 
to direct the light most advantageously; to diffuse the light, decreasing the 
apparent specific intensity of the source and thereby safeguarding the eyes; 
pure decoration. The efficiency of an illumination installation often 
depends to a very great degree on the selection of proper auxiliaries. 

The illumination on a surface is equal to the luminous flux in lumens 
per unit area of the surface, e.g. the foot-candles are equal to the lumens 
per square foot. The average illumination on a plane of reference is equal 
to the lumens through the plane divided by its area. Hence we have the 
following definitions: The net efficiency of an illumination installation is 
equal to the ratio of lumens through the horizontal plane of reference to the 
total lumens generated by the lamps. The gross efficiency of an installation 
is the ratio of the watts supplied to the lamps to the lumens on the plane of 
reference. 

The net efficiency depends only on the method of installing the lamps, 
on the reflectors, etc., used, and on the coefficient of reflection of the walls, 
ceiling, floor and contents of the room. If we represent this average co- 

* The values of sin 3 and cos 3 are given in Table I. 

584 



ILLUMINATING ENGINEERING. 



585 



efficient by fc, multiple reflections theoretically increase the illumination 

1 * 
in the ratio _ . • In practice this is found to be modified by many 

conditions. A general knowledge of the value of the net efficiency to be 
expected in any case enables the illuminating engineer to form a very ready 
estimate of the number of lamps required. 



Table I. 





0° to 29 


o 




30° to 5S 


°. 


60° to 89°. 


e. 


Cos 3 9. 


Sin 3 9. 


9. 
30 


Cos 3 9. 


Sin 3 9. 


9. 
60 


Cos 3 9. 


Sin 3 0. 





1.0000 


0000 


. 6495 


1250 


0.1250 


6495 


l 


. 9994 


0000 


31 


.6299 


1366 


61 


.1139 


6690 


2 


.9982 


0000 


32 


.6098 


1488 


62 


. 1035 


6882 


3 


.9958 


0001 


33 


.5900 


1615 


63 


.0936 


7073 


4 


.9928 


0003 


34 


.5697 


1749 


64 


.0843 


7261 


5 


.9886 


0007 


35 


.5498 


1887 


65 


.0755 


7444 


6 


.9836 


0011 


36 


.5295 


2031 


66 


.0673 


7623 


i 


.9777 


0018 


37 


.5093 


2180 


67 


.0596 


7800 


8 


.9712 


0027 


38 


.4893 


2334 


68 


.0526 


7971 


9 


.9636 


0038 


39 


.4693 


2492 


69 


0460 


8137 


10 


.9551 


0052 


40 


.4495 


2656 


70 


.0400 


8298 


11 


.9458 


0069 


41 


.4299 


2824 


71 


.0345 


8452 


12 


.9357 


0090 


42 


.4103 


2996 


72 


.0295 


8604 


13 


.9251 


0114 


43 


.3913 


3172 


73 


.0250 


8745 


14 


.9135 


0142 


44 


.3722 


3353 


74 


.0209 


8883 


15 


.9011 


0173 


45 


.3535 


3535 


75 


.0173 


9011 


16 


.8883 


0209 


46 


.3353 


3722 


76 


.0142 


9135 


17 


.8745 


0250 


47 


.3172 


3913 


77 


.0114 


9251 


18 


.8604 


0295 


48 


.2996 


4103 


78 


.0090 


9357 


19 


.8452 


0345 


49 


.2824 


4299 


: 79 


.0069 


9458 


20 


.8298 


0400 


50 


.2656 


4495 


80 


.0052 


9551 


21 


.8137 


0460 


51 


.2492 


4693 


81 


.0038 


9636 


22 


.7971 


0526 


52 


.2334 


4893 


82 


.0027 


9712 


23 


.7800 


0596 


53 


.2180 


5093 


83 


.0018 


9777 


24 


.7623 


0673 


54 


.2031 


5295 


84 


.0011 


9836 


25 


.7444 


0755 


55 


.1887 


5498 


85 


.0007 


9886 


26 


.7261 


0843 


56 


.1749 


5697 


86 


.0003 


9928 


27 


.7073 


0936 


57 


.1615 


5900 


87 


.0001 


9958 


28 


.6882 


1035 


58 


.1488 


6098 


88 


.0000 


9982 


29 


.6690 


1139 


59 


.1366 


6299 


89 


.0000 


9994 



* Values of k are given in Table II. 



586 



ILLUMINATING ENGINEERING. 



Table II. Showing; the Intensity of the Illumination in Foot 
Candles Produced at Various Points in Horizontal Planes by 
a liig-ht Source of I.C. P. : the Angle Made by the Xiig-ht Ray 
and a Fine Perpendicular to the Horizontal Plane. 

From a Pamphlet by the National Electric Lamp Association. 



Horizontal Distance in feet from Point Directly under Lamp to Point where 
Intensity of Illumination is desired. 



72 

o 

♦a 
09 

a 







2 


4 


6 


8 


10 


3 


"3 


Foot 




5 


Foot 


"3) 


Foot 


15b 


Foot 




fi 


Foot 


12) 


Foot 




— 


d 


Candles 


< 


Candles 


1 


Candles 


1 


Candles 


< 


Candles 


-51 


Candles 


o9 






o 


' 




o / 




o / 




o 


/ 




o / 




Ch 


2 





.250 


45 




.0883 


63 25 


. 02240 


71 35 


. 00790 


76 





. 00355 


78 40 


.001907 





4 





.0625 


26 


35 


.0447 


45 


. 02206 


56 20 


.01064 


63 


25 


. 00560 


68 10 


. 003220 


6 





.02775 


IS 


25 


. 02365 


33 40 


.01600 


45 


. 00980 


53 


5 


. 00602 


59 


. 003802 




8 





.01563 


14 





.01428 


26 35 


01119 


36 50 


. 008015 


45 





. 00552 


51 20 


.003815 




10 





.010 


11 


20 


.009417 


21 50 


. 007997 


31 


. 00630 


38 


40 


.004757 


45 


. 003530 


<H 


12 





. 006945 


9 


30 


. 00665 


18 25 


. 00592 


26 35 


. 00496 


33 


40 


. 00400 


39 50 


.003120 


d 


14 





.005105 


8 


10 


. 004905 


16 


. 00453 


23 10 


. 00397 


29 


45 


. 003335 


35 35 


.002745 




16 





.00391 


7 


10 


.003818 


14 


. 003567 


20 35 


. 003202 


26 


35 


. 002795 


32 


. 002383 


r 


18 





. 00309 


6 


20 


. 003030 


12 30 


. 002875 


18 25 


. 002648 


24 





. 002353 


29 5 


. 002060 


cj 


20 





. 00250 


5 


45 


. 002460 


11 20 


. 002355 


16 40 


. 002197 


21 


50 


. 002000 


26 35 


.001786 


hI 


22 





. 002065 


5 


10 


. 002047 


10 20 


.001963 


15 15 


.001852 


20 





.001711 


24 30 


.001553 





24 





.001736 


4 


45 


.001715 


9 30 


.001662 


14 


. 001582 


18 


25 


.001480 


22 35 


.001365 


43 


26 





.00148 


4 


25 


.001465 


8 45 


.001428 


13 


.001369 


17 


5 


.001290 


21 5 


.001200 


^ 
Nl 


2s 





.001276 


4 


5 


.001265 


8 10 


.001225 


12 5 


.001190 


16 





.001132 


19 40 


.001062 


"8 


30 





.001111 


3 


50 


.001105 


7 35 


.001080 


11 20 


.001045 


14 


55 


.001002 


18 25 


.000947 



1 

*a 

os 
d 


2 

4 
6 
8 
10 
12 
14 
16 
18 
20 
22 
24 
26 
28 
30 


12 


14 


16 


18 


20 


| 

0> 


Angle 


Foot 
Candles 


Angle 


Foot 
Candles 


Angle 


Foot 
Candles 


Angle 


Foot 
Candles 


Angle 


Foot 
Candles 


3 

S 

G 

> 
z 

1 

.9 
a 
6 

o9 

O 
+a 

A 
U 

« 


o / 
80 35 
71 35 
63 25 
56 20 
50 10 
45 
40 40 
36 50 
33 40 
31 
28 35 
26 35 
24 45 
23 10 
21 50 


.001109 
.001975 
.002485 
. 002665 
. 002623 
. 002450 
. 002220 
.002001 
.001781 
.001575 
.001398 
.001240 
.001108 
.000991 
. 000889 


o / 
81 50 
74 5 
66 50 
60 15 
54 30 
49 25 
45 
41 10 
37 55 
35 
32 36 
30 15 
28 20 
26 35 
25 


. 000722 
.001436 
.001689 
.001913 
.001960 
.001900 
.001801 
.001665 
.001517 
.001375 
.001240 
.001118 
.001008 
.000911 
. 000826 


o / 
82 55 
76 
69 25 
63 25 
58 
53 5 
48 50 
45 
41 40 
38 40 
36 5 
33 40 
31 35 
29 45 
28 5 


. 000473 

. 0008875 

.001207 

.001402 

.001490 

.001506 

.001455 

.001380 

.001288 

.001189 

.001088 

.001000 

.000915 

.000834 

. 000765 


o t 
83 40 
77 30 
71 35 
66 
60 55 
56 20 
52 10 
48 25 
45 
42 
39 20 
35 50 
34 45 
32 45 
31 


.000341 
000631 
. 000876 
.001050 
.001149 
.001181 
.001178 
.001142 
.001090 
.001025 
000955 
. 000890 
.000821 
.000758 
. 000700 


o / 
84 15 
78 40 
73 20 
68 10 
63 25 
59 
55 
51 20 
48 
45 
42 20 
39 50 
37 35 
35 35 
33 40 


. 000242 
.000476 
. 000654 
. 000805 
. 000897 
. 000950 
. 000965 
. 000954 
. 000927 
. 000883 
.000835 
.000785 
. 000736 
.000686 
.000640 



GRAPHIC ILLUMINATING CHART. 587 

Graphic Illuminating* Chart. 

A. E. Parks, Trans. I. E. S., Oct., 1907. 
The equation upon which the chart is based is the well-known one, 

T C 3 

W 2 c a ' 

Where / = Illumination in foot-candles normal to the plane to be illumi- 
nated. 
C = Candle-power reading from a photometric curve, 
a = Angle made by reading C with normal to plane illuminated. 
H = Minimum distance source of illumination to this plane. 

Solving this equation by logarithms consists, as is well known, of finding 
log of C, log of cos 3 a, adding same together and subtracting log of H 2 t 
the remainder giving the logarithm of the result desired, this being exactly 
the graphic method followed in working the chart. 

In Fig. 1, if the distance A-B be laid off representing log C, and 'A—C a 
distance representing log cos 3 a, completing the rectangle will give point D. 
It is desired to add the length of A—C to the length A—B, however, and 
fortunately we may do this graphically if from D we draw a line D-E at an 
angle of 45 degrees till it outs the line A-B produced. A-E now represents 
log C + log. cos 3 a We now wish to subtract from A-E a distance equal 
to log H 2 . 

Laying off vertically from E such a distance E-F, we may, by means of 
a 45-deg?ee line through F, subtract from A-E this distance E-F, giving us 
the point G, A-G then representing the solution of the problem or A-G = 
\og C + log cos 3 a — log H' 2 . If now the diagonal G-F be properly labeled, 
ill values of E-F falling on this line will have the same foot-candle readings, 
And for every other foot-candle reading there will be a diagonal parallel to 
F-G. 

While a chart constructed exactly as per the foregoing description may 
*)e conveniently used, the form here presented is somewhat different in 
arrangement, for by a proper manipulation of axes, one set of diagonals may 
be made to do duty for both D-E and F-G functions, and considerable 
saving in space and complexity results. 

A few samples will elucidate the working of the chart. 

Say that from a photometric curve we get 50 candle-power in a vertical 
lirection, and 100 candle-power at an angle of 45 degrees. It is desired to 
find the illumination on a plane at six feet below the source of light. 

Taking first the 50 candle-power reading. As a in this case is 0, we find 
JO on the top candle-power scale, and follow the diagonal lines to the right 
hand margin, giving the point 5. We now follow horizontally toward the 
left to the vertical through the point 6 found on the lower inclined margin. 
Following a diagonal again to the right hand margin we find for the value 
required 1.40 foot-candles. 

Again from 100 candle-power on the top scale we follow vertically to the 
horizontal line through 45 degrees found on left hand margin, from this 
intersection follow diagonal to right hand margin to 3.5. 

Proceed toward the left horizontally to vertical through 6 as before, and 
again along a diagonal fromthis intersection to the right hand margin, giv- 
ing 1 foot-candle as the desired result. 

As an example of the reversibility of the chart, the following problem will 
be solved. Let it be required to construct a photometric curve that will 

Eroduce a uniform illumination of 1.5 foot-candles upon a plane seven feet 
elow the light source. Find the intersection of the diagonal from 1.5 on 
right hand margin with vertical through 7 on lower scale. 

Follow horizontally to the right to right hand margin, continue from this 
point along a diagonal toward the top, and where this diagonal cuts the 
several degree lines, will be found the candle-power readings required at 
these angles. As 205 candle-power at 45 degrees, 165 candle-power at 40 
degrees, 132 candle-power at 35 degrees, 110 candle-power at 30 degrees, 
96 candle-power at 25 degrees, etc. etc., to 72 candle-power at zero degrees. 



588 



ILLUMINATING ENGINEERING. 



Caudle Power s="C" 

o o o <: 



ooooooooooo 




12345678 9 1011121314 151617 181920212223242526 272829303132333435 
Horizontal Distance 

Fig. 1. 



GBAPHIC ILLUMINATING CHART. 



589 



Table III. Required Illumination for Various Classes 
of Service. 

From a pamphlet by the National Electric Lamp Association. 

Class of Service. Light 

Intensity in 
General illumination of: Foot-Candles. 

Auditoriums 1 to 3 

Theaters 1 to 3 

Churches 3 to 4 

Reading 1 to 3 

General illumination of residences 1 to 2 

Desk illumination 2 to 5 

Postal service 2 to 5 

Bookkeeping 3 to 5 

Stores, general illumination 2 to 5 

Stores, clothing 4 to 7 

Drafting 5 to 10 

Engraving 5 to 10 



Table IV. Snowing- Saving; by the Use of Hig-h Efficiency 

Lamps. 

From a pamphlet by the National Electric Lamp Association. 





Carbon. 


Carbon. 


Gem. 


Tanta- 
lum. 


1 Candle-power 


20. 


20. 


20. 


20. 


2 Watts per candle, nominal . . . 


3.5 


3.0 


2.5 


2.1 


3 Watts per candle, actual . . . 


3.48 


3.04 


2.5 


2.1 


4 Total watts 


69.6 
1040. 


60.8 
520. 


50.0 
560.0 


42 


5 Hours total life 


600. 


6 Cost of lamp 


SO. 16 


$0.16 


$0.20 


$0.54 


7 Cost of renewals per year of 1000 
hours 


0.154 


0.308 


0.36 


0.90 


8 Cost of power per year of 1000 
hours at 10 c. per k.w. hour . . . 


6.96 


6.08 


5.00 


4.20 


9 Cost of power and lamp renewals 
per year of 1000 hours .... 


7.11 


6.39 


5.36 


5.10 


10 Saving over 3.5 W. P. C. lamp . 




0.72 


1.75 


2.01 


11 Saving over 3.0 W. P. C. lamp . 






1.03 


1.29 



Line 5 gives our best knowledge of the life of our lamps with good volt- 
age regulation. A slight difference in standards, a variable regulation or a 
poor regulation will cause lamps to average better or poorer than these 
figures. Line 6 shows the cost of lamp in 10,000 quantity. 



590 



ILLUMINATING ENGINEERING. 




f*-^, 80 # C XN 




\> 70* ^ 

O ^ 60? 




Fig. 2. 



DATA ON ILLUMINATING VALUES. 



591 




?\g. 3. 



592 ILLUMINATING ENGINEERING. 

Experimental Data on Illuminating* Values. 

From paper by Sharp & Millar before Edison Association. 

This auditorium is equipped with a cove-lighting installation and with an 
arrangement of ceiling lamps and side brackets. The Edison Company 
undertook the work of arranging such temporary installations as were 
required for the purpose of the test. These installations were selected at 
the suggestion of the advisory committee in such a way as, first, to bring 
out the relative illumination efficiencies obtainable with similar illuminants, 
variously arranged and variously equipped with reflectors, etc.; second, to 
give a basis for reliable comparisons -of the illuminating efficiencies of 
illuminants of different types. 

The fact should be emphasized, however, that the results here given apply 
in all strictness only to the room in question, and that in using these data 
in connection with other installations, proper consideration should be given 
to this fact. 

The sixteen candle-power carbon incandescent lamps which were used in 
the installations requiring such lamps, were new lamps taken from a package 
which had been purchased recently subject to the inspections of the Elec- 
trical Testing Laboratories, and which could therefore be considered as 
well-rated lamps. These lamps were burned about fifty hours before the 
first test was undertaken. The frosted lamps were selected in a similar 
manner. The actual candle-power and watts of these lamps were deter- 
mined by selecting a considerable number of representative ones and photo- 
metering them in the laboratory, at the actual voltages used in the tests. 
The deterioration of these test lamps in successive tests was also deter- 
mined in this way. 

It is desirable, also, to know what ratio of the total light which is emitted 
by the lamps in a room may be expected to fall on a plane of reference, 
i.e., the horizontal plane on which measurements of the intensity of the 
illumination are commonly made. This ratio of the light generated to the 
light utilized on the plane of reference gives a value for the net efficiency 
of the installation. However, in order to arrive at an expression for this 
efficiency, it is necessary to employ some unit in which the total light from 
the lamps and the total light falling on the plane of reference can be expressed. 
For this purpose the notion of the flux of light is used, and the unit in which 
luminous flux is measured is introduced. This unit is the "lumen," which 
is defined as the flux of light emitted by a source of one candle-power in a 
unit solid angle. The total luminous flux from a source of light is equal to 
47r, or 12.57 times its mean spherical candle-power. We can measure in 
lumens not only the output of the lamps, but also the flux of light through 
the plane of reference, and the ratio of the lumens through the plane of 
reference to the lumens yielded by the lamps gives the net efficiency of the 
installation. In a similar way the efficiency of the lamps may be measured 
by their lumens per watt; and the gross efficiency of the illumination instal- 
lation can be measured by the lumens on the plane of reference per watt 
expended in the lamp. The lumens on the plane of reference are deter- 
mined by multiplying the intensity of illumination on this plane, as ex- 
pressed in candle-feet, by the area of the plane in square feet, i.e., the flux 
through a plane is equal to the intensity of the illumination on the plane 
multiplied by the area of the plane, or the illumination on the plane is equal 
to the density flux of the light falling on that plane. 

In measuring the illumination, forty-five stations were selected, equally 
spaced over the floor of the auditorium. The values of illumination were 
then plotted on a map of the floor area, and then all points having the same 
illumination were connected by lines. This gives a set of lines which we 
have called equilucial lines, by analogy with equipotential lines of an elec- 
trostatic or a magnetic field. 

If the lines are plotted representing in all cases the same percentage 
variation of illumination, the closeness of the lines to each other represents 
the illumination gradient, or the rate at which the illumination is changing 
from place to place on the plane of reference, and consequently the lack of 
uniformity in the illumination. Diagrams of this character have been 
prepared for the various tests. 

A number of such diagrams are given on pages 590 and 591 . These, in 



DATA ON ILLUMINATING VALUES. 593 

each case, show the arrangement of the lamps and a condensed description 
of the type of installation is given. These diagrams show lines of uniform 
illumination for various types of installation. The equilucial lines show 
differences in intensity of ten per cent. Diagram 1 shows the effect of the 
cove lighting alone; 2, ceiling lamps and brackets frosted; 3, concentrating 
prismatic reflections, high level; 4, mirror reflectors, high level; 5, distribut- 
ing reflectors, low plane; 6, gem lamps; 7, tungsten lamps; 8, arc lamps, 
with diffuser shades. 

In a general way the tests made were intended to show, first, the compar- 
ison between the various permanent installations in the auditorium; second, 
the increase in illumination efficiency resulting from equipping the ceiling 
lamps with various reflectors, and the effect of using frosted instead of clear 
bulb lamps; third, the effect of lowering the same equipment to a point 
nearer the floor. Furthermore, gem lamps, tungsten lamps, Nernst lamps 
and arc lamps were installed with the idea of obtaining comparative data 
on their illuminating values as used in a room of the dimensions and char- 
acteristics of this auditorium. These varying results are summarized in 
the accompanying table. 

By a comparison of the lumens which become effective on the plane of 
reference with the lumens which are generated by the lamps, we get a value 
for the net efficiency of the installation. The value of this efficiency indi- 
cates the degree of skill with which the installation has been planned and 
carried out. It is totally unaffected by the efficiency of the lamps employed 
and refers only to the illumination installation as such, irrespective of the 
illuminants used. It is, however, largely affected by the character of the 
room which is illuminated, as is also the gross efficiency of the installation. 

Coefficients of Reflections. 

Bell. 

Many experiments have been made to find the absolute loss of intensity 
due to reflection. This absolute value of what is called the coefficient of 
reflection, that is to say, the ratio of the intensity of the reflected to that 
of the incident light, varies very widely according to the condition of the 
reflecting surface. It also — in case the surfaces are not without selective 
reflection in respect to color — varies notably with the color of the inci- 
dent light. 

The following table gives a collection of approximate results derived 
from various sources. The figures show clearly enough the uncertain char- 
acter of the data. 



Material. 



Coefficient 


of Reflection 




.92 


.70 to 


.85 


.70 " 


.75 


.60 " 


.70 




.60 


.60 " 


.80 


.50 " 


.55 


.40 " 


.50 



Highly polished silver . . 
Mirrors silvered on surface 
Highly polished brass . . 
Highly polished copper . 
Highly polished steel . . 
Speculum metal .... 

Polished gold 

Burnished copper .... 



Smooth papers and paint give a very considerable amount of surface 
reflection of white light, in spite of the pigments with which they may be 
colored. The diffusion from them is very regular, except for this surface 
sheen, and may be exceedingly strong. When light from the radiant point 
falls on such a surface it produces a very wide scattering of the rays, and 
an object indirectly illuminated therefore receives in the aggregate a very 
large amount of light. A great many experiments have been tried to 
determine the amount of this diffuse reflection which becomes available 
for the illumination of a single object. The general method has been to 
compare the light received directly from the illuminant with that received 
from the same illuminant by a reflection from a diffusing surface. 



594 



ILLUMINATING ENGINEERING. 





Table V. 


Comparative Values of Illumination and 




Installation. 




Equipment. 








s 


a 

o 
















s 












u 








-1 


43 


c 




<0 


5 » 


o 











b£)o 




'd 


+a 


o V 


© 












•r. 


u 


(3 


► a 


<T3 








o 




0, 


o 




o ^ 


© 








B 


«£ 


H 
1 


A 


o 


Ott 


tf 






Cove 


121 


10-8 






Clear 






Permanent 


Brackets 


42 


8-0 


2 


Clear 


Clear 


Clear 






Installation, 


















A 


16 c.p. 
Lamps Oval 


Border 


104 


14-10 


3 


Clear 


Clear 


Clear 


















Clear 


* 




Anchored 


Center 


98 


15-6 


4 
5 


Frosted 
Frosted 


Frosted 
Frosted 


Frosted 
Clear 










— 




6 






Frosted 






16 c.p. 

Lamps 

Suspended 

from 
Alternate 
Sockets 










Holophane 




Center 


52 


14-9 


7 


All 


All 


No 


Concen- 
trating 


B 










Lamps 


Lamps 


Side 


Holophane 




Border 


48 


14-1 


8 
9 


Clear 


Clear 


Lamps 


Diffusing 
Mirrored 
Concen- 




















trating 












10 








Holophane 












11 








Concen- 




Same at 


Center 


52 


12-6 




All 


All 


No 


trating 


C 


Different 








12 


Lamps 


Lamps 


Side 


Holophane 




Height 


Border 


48 


11-10 




Clear 


Clear 


Lamps 


Diffusing 
Mirrored 












13 


























Concen- 












- 








trating 


















Mirrored 




















Pendent 




Same 
Lamps 


Center 


38 


14-9 


14 


Clear 


Clear 


Clear 


Concen- 


n 


Border 


48 


14-1 










trating 




Brackets 


12 


8-0 




Clear 


Clear 


Clear 


Mirrored 












15 








Tilted Con- 








— 




- 








centrating 








Gem 


Gem 




Holophane 




No. 16, Gem 








16 


Frosted 
Tip 


Frosted 
Tip 


Border 
Center 


Bowl 

Holophane 
Concen- 
trating 
Holophane 


E 




Center 


12 


13-5 


17 


Tungsten 


Tungsten 






No. 17, 


Border 


12 


13-5 




Clear 


Clear 




Bowl 




Tungsten 




















Nos. 18 & 19, 


Center 


12 


13- 


18 


Opal 


Opal 








Nernst 


Border 


12 


13- 


19 


Opal 


Opal 




Holophane 
Diffusing 










38" 


Con- 


Diffuser 


Outer 
















centric 




Alabaster 




5 Ampere 
















Bobesche 


F 


Enclosed 
D.C. Arc 




9 


12-5 


20 

21 






Alabaster 
Globe 
Clear 


Inner Clear 

Outer 
Inner 



DATA ON ILLUMINATING VALUES. 



595 



Efficiency of Various methods of liig-hting-. 





Photometric Data. 




Illumination Values 
Foot Candles. 


Lamp. 


Efficiency 

Values 

Illumination. 


m 

ft 

£ 

hi 

o 
6 

121 




03 . 

13.42 


2 a 
3.08 


CO O 

3.73 


GO 
+9 
+3 

o3 

t£ 

o 
H 


a 

03 


a 
| 

'1 




o 

'■♦3 

«s 
> 

% 
29.7 


52°. 
1.48 


2"o2 

J* 

h3 ft 


Gross Lumens 
Effective 
per Watt. 


Net Lumens 
Effective 
per Lumen 
Generated. 


16.28 


6210 


2.27 


l.n 


1.72 


3.38 


0.8 


% 
23.7 


244 


14.8 


12.2 


3.26 


3.95 


11600 


7.10 


3.92 


6.18 


25.7 


5.52 


3.16 


1.54 


48.8 


365 


14.05 


11.59 


3.38 


4.05 


17300 


8.41 


5.60 


7.58 


21.0 


6.72 


3.06 


1.265 


41.3 


244 


13.86 


11.41 


3.48 


4.36 


11930 


6.53 


3.70 


5.65 


25.1 


5.07 


2.89 


1.365 


47.3 


365 






3.12 


3.84 


17760 


8.00 
3.80 


5.57 
T98 


7.23 
3.30 


16.85 
28.5 


6.42 


3.03 


1.18 


39.0 


100 


15.5 


12.78 


4910 




3.28 


1.91 


58.2 


100 


15.33 


12.64 


3.22 


3.89 


4930 


5.47 


2.08 


4.07 


36.8 




3.23 


2.35 


72.7 


100 


15.17 


12.5 


3.26 


3.95 


4940 


5.16 


2.08 


4.02 


38.3 




3.19 


2.31 


72.4 


100 


15.43 


12.71 

13.28 


3.17 
3.06 


3.85 

3.72 


4900 


7.69 
4.15 


1.50 
"2^38 


4.92 
3.50 


62.9 
25.3 




3.26 


2.86 


87.7 


100 


16.11 


4940 




3.38 


2.02 


59.8 


100 


14.72 


12.13 


3.30 


4.0 


4865 


5.83 


1.85 


3.94 


50.9 




3.13 


2.30 


73.5 


100 


15.4 


12.69 


3.22 


3.9 


4951 


5.92 


1.91 


4.28 


46.9 




3.22 


2.46 


76.4 


100 


15.33 


12.63 


3.19 


3.87 


4892 


8.20 


1.12 


4.45 


72.4 




3.25 


2.59 


79.6 


98 


14.9 


12.28 


3.29 


3.99 


4798 


7.07 


.83 




66.4 


4.70 


3.76 


2.79 


88.3 


98 


15.25 


12.58 


3.19 

2.67 
2.43 


3.87 

3.14 
2.93 


4775 


6.82 
4.61 


.64 
2.08 


3.33 


76.9 
37.8 


3.92 


3.26 


2.33 


71.5 


«( 


39.1 
105.8 


32.9 

87.8 


4328 




4.21 


2.0 


52.2 


24 


79.3 


63.4 


1.19 


1.49 


1694 


4.75 


1.88 


3.29 


30.2 




8.46 


5.52 


65.2 


24 




37.0 




3.15 


2802 


3.08 


1.14 


2.09 


46.4 




3.98 


2.12 


53.2 


24 




36.9 




3.16 


2798 


3.55 


.95 


2.24 


58.0 




3.98 


2.28 


57.3 


9 




22.9 




2.7 


5530 


7.88 


2.07 


4.31 


S7.5 




4.54 


2.22 


48.9 


9 


. 


22.9 




2.7 1 


5530 


6.46 


1.73 


4.01 


58.6 




4.54 


2.06 


45.3 



596 



ILLUMINATING ENGINEERING. 



The following table gives an aggregation of the results obtained by sev- 
eral experimenters, mostly from colored papers: 



Material. 



White blotting paper 

White cartridge paper .... 

Ordinary foolscap 

Chrome yellow paper 

Orange paper 

Plane deal (clean) 

Yellow wall paper 

Yellow painted wall (clean) . . 

Light pink paper 

Yellow cardboard 

Light blue cardboard 

Brown cardboard 

Plane deal (dirty) 

Yellow painted wall (dirty) . . 

Emerald green paper 

Dark brown paper 

Vermilion paper 

Blue green paper 

Cobalt blue 

Black 

Deep chocolate paper . . . . 
French ultra-marine blue paper 

Black cloth 

Black velvet 



Coefficient of 
Diffuse reflection. 



.40 



.82 

.80 

.70 

.62 

.50 

to . 

.40 

.40 

.36 

.30 

.25 

.20 

.20 

.20 

.18 

.13 

.12 

.12 

.12 

.05 

.04 

035 

012 

004 



50 



Interior Illumination. 

Bell. 

To illuminate a room 20 ft. square and 10 ft. high on the basis of a mini- 
mum of 1 candle-foot, will require from 80 to 144 effective candle-power, 
according to the arrangement of the lights, if the finish is light, and half 
as much again, at least, if the finish is dark. The floor space being 400 
sq. ft. it appears that the illumination is on the basis of about 3 to 5 sq. ft. 
per effective candle-power. The former figure will give good illumination 
under all ordinary conditions; the latter demands a combination of light 
finish and very skillfully arranged lights . 

For very brilliant effects, no more than 2 sq. ft. per candle should be 
allowed, while if economy is an object, 1 c.p. to 4 sq. ft. will furnish a 
very good groundwork of illumination, to be strengthened locally by a 
drop-light or reading lamp. The intensity thus deduced may be compared 
to advantage with the results obtained by various investigators, reducing 
them all to such terms as will apply to the assumed room which is under 
discussion. 



Just deduced 
Uppenborn 
Piazzoli . . 
Fontaine . . 



1 c.p. per 3 sq. ft. 

1 c.p. per 3.6 sq. ft. 

1 c.p. per 3.5 sq. ft. 

1 c.p. per 7.0 sq. ft. (approximation). 



In very high rooms the illumination just indicated must be materially 
increased, owing to the usual necessity for placing the lamps rather higher 
than in the case just given, and on account of the lessened aid received 
from diffuse reflection. The amount of this increase is rather uncertain, 
but in very high rooms it would be wise to 'allow certainly 1 c.p. for every 
2 sq. ft., and sometimes, as in ball-rooms and other special cases requiring 
the most brilliant lighting, as much as 1 c.p. per square foot. 

Perhaps the most important rule for domestic lighting is never to use, 
indoors, an incandescent or other brilliant light, unshaded. Ground or 
frosted bulbs are particularly good when incandescents are used, and opal 



INTERIOR ILLUMINATION. 



597 



shades, or holophane globes, which also reduce the intrinsic brilliancy, are 
available with almost any kind of radiant. Ornamental shades of tinted 
glass or of fabrics are exceedingly useful now and then, when arranged to 
harmonize with their surroundings. 

The table below is intended as a hint about the requirements for domes- 
tic lighting, and while it is laid out for a fairly large house, containing 
twenty rooms and three baths, its details will furnish suggestions appli- 
cable to many cases. An 8-c.p. lamp of the reflector variety should be 
placed in the ceiling of every large closet, and controlled by a switch from 
the room or by an automatic switch, turning it on when the door is fully 
opened. 



Room. 



8 c.p. 



Hall ....... 

Library 

Reception room . . 
Music room . . . 
Dining room . . . 
Billiard room . . . 

Porch 

Bedrooms (6) . . . 
Dressing rooms (2) 
Servants' rooms (3) 
Bathrooms (3) . . 
Kitchen 

Pantry 

Halls 

Cellar 

Closets (4) . . . . 

Total .... 



64 



16 c.p. 



14 
4 
3 
3 



30 



32 c.p. 



| Sq. Ft. 
per c.p 



4.7 
3.1 
7.0 
3.0 
2.7 
2.3 

7.0 

4.7 
9.4 
5.0 



Remarks. 



8-c.p. reflector lamps 



Eight reflector lamps 
32 c.p. with reflectors 



Reflector lamps 



Watt* at lianip Terminals Per Square Foot floor Space 
for Hig-lt Class Arc JLig-liting-. 

(By W. D'A. Ryan.) 



Building. 


Range. 


Average 
Condi- 
tions. 


Machine shops; high roofs, electrically driven 
machinery, no belts 

Machine shops; low roofs, belts, other obstruc- 
tions 


.5 to 1 

.75 to 1.25 
.5 to 1 

.75 to 1.25 
1 to 1.5 

.9 to 1.3 
1.1 to 1.5 
1.25 to 1.75 
1.5 to 2 


.75 
1 


Hardware and shoe stores 


.75 


Department stores; light material, bric-a-brac, 
etc 


1 


Department stores; colored material .... 

Mill lighting; plain white goods 

Mill lighting; colored goods, high looms . . . 

General office; no incandescent s 

Drafting rooms 


1.25 
1.1 
1.3 
1.6 

1.75 







( 



Note : Energy based on watts at lamp terminals. 



598 



ILLUMINATING ENGINEERING. 



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GENERAL ILLUMINATION. 599 



General Illumination. 

The subject of illumination has been divided by Mr. E. L. Elliott, to 
whom we are indebted for many suggestions, into, the following sub-divisions: 
Intensity or brilliancy, distribution, diffusion, and quality. 

Intensity of Brilliancy. — The average brilliancy of illumination 
required will depend on the use to which the light is put. "A dim light 
that would be very satisfactory for a church would be wholly inadequate 
for a library, and equally unsuitable for a ballroom." 

The illumination given by one candle at a distance of one foot is called 
the "candle-foot" or "foot-candle, " and is taken as a unit of intensity. In 
general, intensity of illumination should nowhere be less than one candle- 
foot, and the demand for light at the present time quite frequently raises 
the brilliancy to double this amount. As the intensity of light varies 
inversely with the square of the distance, a 16 candle-power lamp gives a 
candle-foot of light at a distance of four feet. A candle-foot of light is a 
good intensity for reading purposes. 

Assuming the 16 candle-power lamp as the standard, it is generally found 
that two 16 candle-powder lamps per 100 square feet of floor space give good 
illumination, three very bright, and four brilliant. These general figures 
will be modified by the height of ceiling, color of walls and ceiling, and 
other local conditions. The lighting effect is reduced, of course, by an 
increased height of ceiling. A room with dark walls requires nearly three 
times as many lights for the same illumination as a room with walls painted 
white. With the amount of intense light available in arc and incandescent 
lighting, there is danger of exceeding " the limits of effective illumination 
and producing a glaring intensity," which should be avoided as carefully as 
too little intensity of illumination. 

Distribution of Ug-lit. — Distribution considers the arrangement of 
the various sources of light, and the determination of their candle-power. 
The object should be to " secure a uniform brilliancy on a certain plane, or 
within a given space. A room uniformly lighted, even though compara- 
tively dim, gives an effect of much better illumination than where there is 
great brilliancy at some points and comparative darkness at others. The 
darker parts, even though actually light enough, appear dark by contrast, 
while the lighter parts are dazzling. For this reason naked lights of any 
kind are to be avoided, since they must appear as dazzling points, in 
contrast with the general illumination." 

The arrangement of the lamps is dependent very largely upon existing 
conditions. In factories and shops, lamps should be placed over each ma- 
chine or bench so as to give the necessary light for each workman. In the 
lighting of halls, public buildings, and large rooms, excellent effects are 
obtained by dividing the ceiling into squares and placing a lamp in the 
center of each square. The size of square depends on the height of ceiling 
and the intensity of illumination desired. Another excellent method con- 
sists in placing the lamps in a border along the wall near the ceiling. 

For the illumination of show windows and display effects, care must be 
taken to illuminate by reflected light. The lamps should be so placed as to 
throw their rays upon the display without casting any direct rays on the 
observer. 

The relative value of high candle-power lamps in case of an equivalent 
number of 16 candle-power lamps is worthy of notice. Large lamps can be 
efficiently used for lighting large areas, but in general, a given area will be 
much less effectively lighted by high candle-power lamps than by an equiva- 
lent number of 16 candle-power Tamps. For instance, sixteen 64 candle- 
power lamps distributed over a large area will not give as good general 
illumination as sixty-four 16 candle-power lamps distributed over the same 
area. High candle-power lamps are chiefly useful when a brilliant light is 
needed at one point, or where space is limited and an increase in illuminat- 
ing effect is desired. 

Diffusion of Lig^ht. — "Diffusion refers to the number of rays that 
cross each point. The amount of diffusion is shown by the character of the 
shadow. Daylight on a cloudy day may be considered perfectly diffused ; 
it produces no shadows whatever. The light from the electric arc is least 
diffused, since it emanates from a very small surface ; the shadows cast 
by it have almost perfectly sharp outlines. It is largely due to its high 
state of diffusion that daylight, though vastly more intense than any artifi- 
cial illumination, is the easiest of all lights on the eyes. It is a common 



I 



500 ILLUMINATING ENGINEERING. 

and serious mistake, in case of weak or overstrained eyes, to reduce the 
intensity of the light, instead of increasing the diffusion." 

Quality of* Eig-ht. — " Aside from difference in intensity, light pro- 
duces many different effects upon the optic nerves and their centers in the 
brain. These different impressions we ascribe to difference in the quality 
of the light. Thus, 'hard light,' 'cold light,' * mellow light,' 'ambient 
light,' etc., designate various qualities. Quality in light is exactly analogous 
to timbre or quality in sound, which is likewise independent of intensity. 
The most obvious differences in quality are plainly those called color. But 
color is bv no means the element of quality. The proportion of invisible 
rays and the state of diffusion, are highly important factors, but on account 
of not being directly visible, they have been generally overlooked, and are 
but imperfectly understood." 

Xiie Correct "Use of I^igJis. 

How to Avoid Harmful Effects on the Eyes. — An objection 
frequently urged against the incandescent lamp is that it is harmful to the 
eyes and ruins the sight. This is true only in so far as the lamp may be im- 
properly used. Any form of light as frequently misused would produce the 
same harmful results. Few people think of attempting to read by an un- 
shaded oil lamp, and yet many will sit in the glare of a clear glass incan- 
descent lamp. Incandescent lamps are more generally complained of, 
because, unlike oil or gas, they can be used in any position. Bookkeepers 
and clerks are often seen with an incandescent lamp at the end of a drop 
hanging directly in front of their eyes — an impossible position of the light 
from gas or oil. 

The first hygienic consideration in artificial lighting is to avoid the use of 
a single bright light in a poorly illuminated room. In working under such 
a light the eye is adapted to the surrounding darkness, and yet there is one 
spot in the middle of the eye that is kept constantly fixed on the very bright 
light. The brilliancy of the single light acting on the eye adjusted to dark- 
ness, works harm. There should be a general illumination of the room in 
addition to any necessary local light. If sufficient general illumination is 
provided, the eye is adjusted to the light, and the local light can be safely 
used. The ideal arrangement provides general illumination so strong that 
a pencil placed on the page of a book casts two shadows of nearly equal 
intensity — one coming from the general light and the other from the local 
light. 

Care should also be taken to prevent direct rays from striking the eye. 
The light that reaches the eye by day is always reflected. In reading or 
writing, to avoid shadows, the light should come over the left shoulder. 
Only the reflected rays can then reach the eye. 

Another point to be avoided is the careless, general use of clear glass, 
unshaded lamps. Frosted bulbs should be used in place of clear glass 
where soft light for reading is required. The intensity of light reflected 
from a small source is increased, and intense light injures the eye. With a 
clear glass globe the whole volume of light proceeds directly from the small 
surface of the lamp filament. With a frosted bulb the light is radiated 
from the whole surface of the bulb, and while the total illuminating effect 
is practically undiminished, the light is softened by diffusion, to the great 
comfort and relief of the eyes. 

Finally, the use of old, dim, and blackened lamps, giving but a small 
fraction of their proper light, is very often a source of trouble in not supply- 
ing a sufficient quantity of light. Users of lamps are not otfen aware of 
the loss in candle-power a lamp undergoes, and so it happens that lamps 
are retained in use long after their efficient light-giving power has vanished. 
Proper attention to lamp renewals on the part of Central Stations is neces- 
sary to correct this evil. 

The correct use of light requires : 

That there should be general illumination in addition to the light near at 
hand. 

That only reflected light should reach the eye. The light should be so 
placed as to throw the direct rays on the book or work, and not in the eye. 

That the light should be placed so that shadows will not fall on the work 
in hand. 

That shades and frosted bulbs should be used to soften the light. 

That lamps be frequently renewed to keep the light up to full candle- 
Dower. 



CONCEALED LIGHTING SYSTEMS. 601 



Distribution of B.ig-ht l>\ Incandescent Lanip<«. 

The best form of lighting interiors is to have single lamps uniformly dis- 
tributed over the ceiling; unless the room has been especially designed 
with this in view, it is sometimes difficult to accomplish. 

Another method giving most excellent results, but requiring more candle- 
power, is the arrangement of lamps around the sides of the room close to 
the ceiling. If the walls and ceiling are of a light color, this method is 
quite satisfactory, and easier to wire. 

If the chandeliers, or more correctly in this case, electroliers, are used, 
it is best to have but one main or large one in the room, balancing the light 
by side brackets. 

All such suspended lights should be above the line of vision as far as 
convenient. » 

The most economical distribution, as far as candle-power necessary, is the 
first mentioned, where lights are evenly distributed over the ceiling. To 
obtain the same luminosity by using clusters of lamps more widely distrib- 
uted instead of single ones, will require much more candle-power. 

The 16 candle-power lamp is the universal standard in the United States 
when rating lamps or illumination, and following are given some ratings 
on which illumination of different classes of buildings is figured. 

Ordinary illumination, 1 lamp, 8 feet from floor for 100 square feet, as in 
gheds, depots, walks, etc. 

In waiting-rooms, ferry-houses, etc., 1 lamp for 75 square feet. 
In stores, offices, etc., 1 lamp for 60 square feet. 

Of course the above must be varied to suit the circumstances, such as 
dark walls or other surroundings requiring more light, as the walls reflect 
little of that furnished; and in rooms with dead white walls the reflection 
approaches 90 per cent, and less lamps would be required than in interiors 
having worse reflecting surfaces. 

A very ingenious and satisfactory method of illuminating high arched 
and vaulted interiors, developed first by Mr. I. R. Prentiss of the Brush 
Company, is to place a number of lamps around the lower edge of the arch 
or dome, with reflectors under them, and so located behind the cornice as 
to be invisible to the eye from the floor. 

The dome or arch will reflect a large part of the light so placed, giving a 
very fine, even illumination to the whole interior, without shadows, and very 
restful to the eye. 

Of course the arch must be of good color for reflecting the light, or much 
of it will be wasted. 



Concealed Lig-hting- Systems. 

The elements of inefficiency of systems in which the lighting is by con- 
cealed sources of light, or different lighting systems, have been classified by 
Millar* under four heads as follows: 

1. Light absorbed by ceilings and walls. 

2. Loss due to unnecessary intensity at unimportant points. 

3. Ineffectiveness of sharply inclined rays. 

4. Higher intensity necessary with diffused lighting. 

Some of his experimental data illustrating these elements quantitatively 
are given in the following tables. 

* Millar, Trans. Illuminating Engineering Society, Oct., 1907. 



i 



602 



ILLUMINATING ENGINEERING. 



Table VII. 

Millar. 





Temporary 
Installation at 
Electrical Test- 
ing Laboratories. 


Harlem Office of 
New York 

Edison 
Company. 




System. 


System. 




Direct. 


Diffused. 


Direct. 


Diffused. 


Total flux of light, lumens .... 
Flux on working plane, lumens . . 
Efficiency of light utilization . . . 
Efficiency of illuminants (lumens 

per watt) 

„ , . a. „ Diffused 
Relative en. of systems; ~. 

Sacrificed to secure diffusion . . . 


424 
180 

42.3% 

2.92 

28 pei 
72 pei 


4824 
579 
12.0% 

2.01 
• cent. 
' cent. 


13938 30532 
6642 4689 
47.7% 15.4% 

3.34 3.34 
32 per cent. 
68 per cent. 



Table VIII. Illumination Intensity Required for 
Reading-. 

Millar. 









Foot-Candles. 




Angle of Paper 
















Observer. 


with 
Horizontal. 






Diff. in Per 






Direct. 


Diffused. 


Cent of 
Direct. 


H. E. Allen .... 


46° 


2.5 


4.7 


184 


Night watchman 






42° 


3.7 


4.8 


130 


Dynamo tender . 






35° 


1.85 


2.7 


144 


H. E. Allen . 








47° 


3.0 


5.3 


180 


W. S. Howell . 








47° 


2.95 


6.3 


217 


C. H. Sharp . 








44° 


3.6 


5.0 


140 


Z. N. Corraz 








49° 


2.3 


3.1 


135 


P. S. Millar . 








46° 


2.75 


5.0 


181 


F. M. Farmer 








49° 


2.1 


5.0 


237 


E. Fitzgerald . 








49° 


2.9 


2.6 


100 




2.7 


4.45 


165% 



Note. — The last value obtained, in which the experimenter required 
the same intensity of illumination with the diffused lighting system that was 
desired for the direct lighting system, differs from all the other values- 
Subsequently it was learned that this observer was influenced by the bright- 
ness of the walls to select the stated intensity upon the paper, feeling 
that greater brightness upon the walls would be annoying and unpleasant 



LIGHTING SCHEDULES. 603 

Millar's conclusions are as follows: 

"The conditions of the installations were such that the increase in inten- 
sity required for reading with diffused lighting was probably larger than may 
be considered a representative value. The factor is a function chiefly of 
the brightness of the walls and of the extent to which the walls and other 
brightly illuminated objects come within the angle of vision. 

"It was found that if a placard was viewed at a distance of eight or ten 
feet, thirty times as much light was required to enable an observer to read 
it as well with the diffused lighting as with the direct lighting arrangement. 
In this test large portions of the walls were within the angle of vision, and 
exercised a powerful influence upon the eyes of the observer with both light- 
ing systems. With the direct lighting system the walls were relatively 
dark, influencing the pupilary action of the eye so that a low intensity upon 
the placard appeared satisfactory. With the diffused lighting system they 
were brilliantly illuminated and so affected the eye that a very intense 
illumination was required upon the placard. 

"From the foregoing, the writer has drawn the following conclusions: 
In diffused lighting systems of the class considered, where the illumination 
of a working plane is one of the prime objects, a large proportion of the light 
is lost; that which is not lost becomes less effective; brilliant illumination 
is produced where it is useless and even undesirable; and conditions are 
established which create a demand for an unduly high intensity of illumi- 
nation on objects viewed. 

"These effects are present in varying degree in all systems in which con- 
trol of any large proportion of the light is lost. Among such are cove light- 
ing, lighting with skylight effects, tube lighting, and all systems in which 
the brilliancy of the light source is reduced by diffusing surfaces used with- 
out any directing adjuncts. Lighting with large sources is more liable to 
these effects than lighting with small sources. 

"The facts indicate the need for devoting as much care to securing suit- 
able minimum intensities, as is generally expended in striving for maximum 
values. In certain classes of lighting where more light is asked for, the 
requirements may be served by reducing the intensity of illumination on 
unimportant objects which are unnecessarily well illuminated. By taking 
advantage of opportunities to minimize intensities at unimportant places 
efficiency is gained, and, in the opinion of many, good lighting as well." 

MftHTINC} §(HEI)iLES, 
General Rule for Construction of Schedules. 

JVEoonligrht Schedules. — Start lamps one half hour after sunset 
until fourth night of new moon; start lamps one hour before moonset. 

Extinguish lamps one hour before sunrise, or one hour after moon-rise. 

No light the night before, the night of, and the night after full moon. 

During summer months there will be found nights near that of full moon 
when, under the rule, the time of lighting would be very short. It may not 
be positively necessary to light up during such times. 

If better service be desired, but not full every night and all-night service; 
lamps can be started at sunset and run to 12 or 1 o clock on full-time sched- 
ule, and after 12 or 1 on the moonlight basis. 

The above rules by Alex. C. Humphreys, M.E., have been modified by 
Frund as follows: Light every night from dusk to 12 o'clock; after 12 o'clock 
follow Humphrey's rule for moonlight schedule, excepting there will be no 
light after 12 o'clock during the three nights immediately preceding full 
moon. 

AU-Nig-ht, Every-Hig-lit Schedule. — Start lamps one half horn 
after sunset, and extinguish them one half hour before sunrise every day 
in the year. Full schedule commonly called 4000 hours for the year. 

All the above rules serve to make schedules for any locality, and such 
schedules must be based on sun time for the locality, and not on standard 
time. 

Permanent average schedules are used in New York City, but for other 
cities they are usually made up fresh every year. 

Following will be found New York City time tables, also another set by 
Humphreys that is a good average for sun time in any locality. 



604 



ILLUMINATING ENGINEERING. 



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LIGHTING TABLE. 



605 



•Sat 
-tun a 

GUI IX 



P M CO M CC CO W M ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ t ^ t ^ ^ # ^ ^ ^T ^T 'T ^ ^ ^r 

-' eo co eo co co co co co co co" co co co* co' co co co co* co" co co' co co* ci co' co" co* co" co' co" co" 



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jcococoM^^^^^^^^^^^^^ou^cicwioou'ii^ciqioifliA 
:«o»w«c©<d©^^©^©^©©©^^©©<o<©<o<o<©<o<o<©<oo«o 



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Hioidioiooio'iowiocoioiooioioiaoioioioioiQiaiaioioioioiQio 



•Sax 
-rung 
©mix 



^*T*i^00rHC0t-©T^Tti©a9i^COiOt^©^CN^©t>-^COTt<©t>-l>00©'--i 
£cOCOCOTt<^T*T^lOiqiqiO©0©©OrHr^i-HrHi^CNCNC>^ 

J, CN CN CN* CN CN CN* CN CN <N* CN* CN* CO* CO CO* CO CO* CO* CO* CO* CO* CO* CO CO* CO CO CO CO CO CO CO 



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e^C0^»O«Or>-Q0C35©^CNCOrH»O©b-00O»©T-i 



SSSSSSSSSSSS 



606 



ILLUMINATING ENGINEERING. 



Summary of New York City I^igrliting* Tahle. 



January . 
February 
March . . 
April . . 
May . . 
June . . 
July . . 
August 
September 
October . 
November 
December 



Hours for 


Average. 


Average 


the Month. 


Day. 


h.m. 


h.m. 




413.10 


13.19 


18th 


355.27 


12.15 


15th 


341.29 


11.01 


16th 


290.17 


9.40 


16th 


264.39 


8.32 


15th 


238.51 


7.57 


12th 


256.12 


8.16 


17th 


286.26 


9.14 


16th 


316.48 


10.33 


15th 


368.50 


11.54 


16th 


392.59 


13.05 


14th 


424.52 


13.42 


10th 



Total hours 



3950 



Shortest 
Longest 

Average 




Note. — Lights started 30 minutes after sunset. Lights stopped 30 min- 
utes before sunrise. 

For commercial lighting : add 1 hour for part night lights, add 2 hours for 
all night lights to above schedule. 

Table Showing- lumber of Hours Artificial liig-ht i* 
deeded in Each month of the Year. 

Dr. Louis Bell. 



Evening from 



Dusk to 6 o'clock 
Dusk to 7 o'clock 
Dusk to 8 o'clock 
Dusk to 9 o'clock 
Dusk to 10 o'clock 
Dusk to 11 o'clock 
Dusk to 12 o'clock 
All night .... 



Morning from 

4 o'clock to dawn 

5 o'clock to dawn 

6 o'clock to dawn 

7 o'clock to dawn 



13 

44 

75 

116 

217 



82124 



62 80 

92 111 

122(142 

152173 



102 112 155 182 204 189 



133 
164 
307 



16 



142 186;212 
172 217 242 
345 421 473 



110 
80 
50 
20 



235 
266 
527 



137 

106 

75 

44 



b 


c3 










a 


3 


A 












o 
u 

3 




>> 

03 


a 

»-5 


1-5 


fe 


S 


< 


s 


65 


33 

61 


4 
31 








96 


4 






127 


89 


62 


28 


4 




158 


117 


93 


58 


29 


8 


189 


145 


124 


88 


60 


38 


220 


173 


155 


118 


91 


68 


251 


201 


186 


148 


122 


98 


512 


411 


382 


295 


242 


195 


137 


93 


71 


28 


2 




106 


70 


40 


3 






75 


42 


9 








44 


14 





















722 
472 
269 
122 



LIGHTING TABLE. 



607 



SI 

s2 

8^ 



£> S3 



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-iqioiowio^^wnwconrtcjNHrjrtHHqqoqiciqifl^ 



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j; -i d d c c <i d d d ci 'i c d d w m' c o ic c ui ic c c c w c o 



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608 



ILLUMINATING ENGINEERING. 



o £228388888388883388883833888888 

jgoooooowooooooocooooododooooooooooooooooooooooodoocooocooocjo 






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^<*w*^®^««©3222;3SS;$S38SSc3&S8&c588 



LIGHTING TABLE. 



609 



c~ 



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a 

1 v 

c <i 

£ O 

"5 ^ 

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Is 

u -z 

ft w 

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coooqoHH«fjc]N«n««nMioicooooooooHHS 



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^t^t>*^t>t^r>t^t>"^t^t>^^t>'^i>"^i^^t^t>°^t^t>r^t>"a~c^t^t^^ 



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i-iHrtT-(rtilT-lr-lHrtCN(NC^CSCNC5^WCSC4CO?) 



610 



ILLUMINATING ENGINEERING. 



Bo 






8 ^ 

Si 

II 

g *5 W 

8t& 



ft w 

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.coeoeoeoeoeoeococoeocoeoeoeocoeocoeoc^e^ 






55 



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Swwco§§^^5§^§^S§SS§^§§OoOOoooSo^h 






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9 
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rt^CO , *»OCOt-aOaO'-"C^COrf<iO«ONOOOSOHeqcO'flfltON0005QH 



<NCS<M<NC?$<N<M<N&e<5eO 



LIGHTING TABLES. 



611 



Hoars of JLig-litiug- per Annum by Different Schedules. 

Regular all-night schedule ......... 4000 hours 

New York City schedule 3950 hours 

Philadelphia schedule t 4288 hours 

Providence schedule ........... 4012 hours 

Philadelphia moonlight schedule , 2190 hours 

Frund schedule 3000 hours 



Hours of Burning- Commercial lights. 

Time of Sunrise and Sunsets. 





1 


o 


o 


og 


oi 


oH 


© J 




All night 




mm Am 


^ s 

w ft 
►3-30 


w ft 
Do 


<V © 


P2 


it 


&2 


pi v 


lights. 




- o p 

h3 60 C 






h.m h.m 


h.m. 


h.m. 


h.m. 


h.m. 


h.m. 


h.m 


im. 


h.m. 


h.m. 


Jan. 15 


4.55; 4.30 


3.30 


4.30 


5.00 


5.30 


6.30 


7.30 


7.25 


8.00 


15.30 


Feb. 15 


5.31 5.00 


3.00 


4.00 


4.30 


5.00 


6.00 


7.00 


6.56 


7.30 


14.30 


Mar. 15 


6.06 5.30 


2.30 


3.30 


4.00 


4.30 


5.30 


G 30 


6.12 


6.45 


13.15 


April 15 


6.41 6.15 


1.45 


2.45 


3.15 


3.45 


4.45 


5.45 


5.16 


5.45 


11.30 


May 15 


7.13 6.45 


1.15 


2.15 


2.45 


3.15 


4.15 


5.15 


4.39 


5.15 


10.30 


June 15 


7.37 7.00 


1.00 


2.00 


2.30 


3.00 


4.00 


5.00 


4.24 


5.00 


10.00 


July 15 


7.32 


7.00 


1.00 


2.00 


2.30 


3.00 


4.00 


5.00 


4.39 


5.15 


10.45 


Aug. 15 


7.00 


6.30 


1.30 


2.30 


3.00 


3.30 


4.30 


5.30 


5.08 


5.45 


11.45 


Sept. 15 


6.09 


5.30 


2.30 


3.30 


4.00 


4.30 


5.30 


6.30 


5.40 


6.15 


12.45 


Oct. 15 


5.19 


4.45 


3.15 


4.15 


4.45 


5.15 


6.15 


7.15 


6.13 


6.45 


14.00 


Nov. 15 


4.39 


4.00 


4.00 


5.00 


5.30 


6.00 


7.00 


8.00 


6.52 


7.15 


15.45 


Dec. 15 


4.31 


4.00 


4.00 


5.00 


5.30 


6.00 


7.00 


8.00 


7.20 


7.45 


15.45 


Aver'ge ) 
for y'r j 


6.06 


5.30 


2.30 


3.30 


4.00 


4.30 


5.30 


6.30 


5.54 


6.26 


13.00 



Graphic Ug-hting* Schedule for London, England. 



*T>.M. 


J 4 


5 


6 


7 8 9 10 11 MI0.1.AM. 2 3 4 


5 6 7 8 1 








\ 


1 i "I""" 


iii: 


■W- 


* 










v - 


^ 1 




p 




FEB. 

f 
MAR. 








>U , ii 


; ' • r 


'■• ' /a 














\ 


. 




/ 


m 








APR. 












0\ 






/ / 










JUNE 












y\ 






;' 






















J /l 




























P V ' 








V 


















/ 


' J - 






V 








OCT. 






u/y i ^ 








S\j* \ 






DEC. 


/ jj j 1 1 







< ?' t" ~J he snaded area represents the time during which light la 
required. The horizontal lines show the months of the year. The vertical 
lines show the hours of the day and night. The inner dotted lines show the 
time of sunset and sunrise. The outer lines show the time of lighting up 
and extinguishing. Each square is an hour month, i.e., 30.4 hours? 



"HIS )s 



oum 



ELECTRIC RAILWAYS. 

Revised by A. H. Armstrong, C. Renshaw and N. W. Storer. 



The electric railway motor has made such rapid strides in traction that it 
has pre-empted the entire urban field, taken most of the traffic from the 
suburban steam lines and is now appearing as a formidable competitor to 
the steam locomotive in heavy haulage. In considering, therefore, the appli- 
cation of the electric motor to traction work, it is necessary to determine its 
capacity and characteristics for city service and single car operation, and 
also for electric locomotives hauling heavy trains, either high speed passenger 
or slow speed freight. Small cars weighing 10 to 12 tons may be fitted with 
two 35 h.p. motors and be geared for a maximum speed of 25 to 30 m.p.h. 
Larger cars of the single truck variety weighing close to 15 tons may be 
equipped with motors of 40 h.p. capacity. Single truck cars are used (to a 
large extent) for city work, although in this class of work the use of double 
truck cars is rapidly increasing. 

Suburban cars weighing 18 to 25 tons and measuring 45 ft. overall may 
be equipped with four 50 h.p. motors and be geared for a maximum speed 
of 40 m.p.h. Such cars usually make stops approximately every mile, and 
a schedule speed of about 20 m.p.h. outside of the city limits. Larger types 
of suburban cars 50 ft. overall, seating 52 passengers, weigh 28 to 30 tons 
and are equipped with four 75 h.p. motors geared for maximum speed of 
45 m.p.h. These cars usually make a stop every mile and a half, and a 
schedule speed of 25 m.p.h. for the local and 35 m.p.h. for the express cars 
outside of the city limits. The largest type of suburban car, of which that of 
the Aurora, Elgin & Chicago is typical, is equipped with four 125 h.p. motors, 
is geared for maximum speed of 60 m.p.h. and stops but once in two or three 
miles, making a schedule speed of about 35 m.p.h. These cars represent 
the highest type of interurban electric railway and their use seems justified 
under certain conditions. 

Orades. — Grades upon city lines may run as high as 13 percent, and to 
surmount these it is necessary to have every axle on the cars equipped with 
motors; thus a single-truck car would require two motors and double-truck 
cars four motors; and even then the cars will be unable to surmount these 
grades with very bad conditions of track. Surface cars operating over city 
streets have no option but to use the prevailing grades, hence for city work 
where heavy grades are liable to be met, the motor capacity per car should 
be liberal, not so much on account of the danger of overheating the motors, 
as to prevent undue sparking when surmounting the heavy grades. The 
tendency of the suburban roads is to operate over private right of way, and 
grades on these roads do not generally exceed two or three per cent, except 
for very short runs where they may reach four or five per cent. Grades 
exceeding these are infrequent, and on the best high speed suburban roads 
two per cent grade is the maximum allowable. The effect of grades upon 
the heating of motors is largely compensating as the motors cool off nearly 
as much in coasting down grades as they overheat when doing extra work 
in surmounting the grades. 

Curves. — In city work sharp curves are necessary in rounding street 
corners and curves of 50 ft. radius are sometimes met. These curves are 
oftentimes so sharp as to prevent the use of heavy, long double-truck sub- 
urban cars. Such curves cannot easily be avoided and city cars are designed 
with short wheel base of trucks, generally not over 6 ft. in order to be able 
to round these sharp curves. The maximum speed of city cars is limited 
to about 15 m.p.h., so that these sharp curves cannot interfere seriously with 
the schedule. 

Suburban cars operate over much straighter track and have a maximum 
speed of 25 to 50 miles per hour. It is seldom that the curves are sharp 
enough to seriously inconvenience the purely suburban class of service. 
Roads operating over private right of way endeavor to limit the curves to 
five degrees, which can be rounded at a speed of 35 miles per hour, so that 

612 



ELECTRIC RAILWAYS. 613 

they do not seriously interfere with the schedule. Very high speed suburban 
roads will not permit curves of more than three degrees, as a sharper curva- 
ture interferes with free running speed of the cars, which sometimes 
approaches 60 miles per hour. Sharp curves are more detrimental to the 
maintenance of high speed than grades of four or five per cent unless the 
latter be of considerable length. 

Systems of Operation. — There are four systems of operation now in 
use for electric railways, each of which has some distinctive advantages 
warranting its use under certain conditions. 

1. D. C. generation and D. C. distribution with the possible use of boosters 
or floating storage batteries. — This system is pre-eminently adapted to the 
very congested travel of the more densely populated sections of our larger 
cities. It is not well adapted to the operation of roads covering large areas 
and is rapidly becoming obsolete, owing to the great amount of feeder 
copper required to transmit large amounts of energy at 600 volts, which is 
the standard potential used. The use of boosters is objectionable for con- 
tinuous work as they add largely to the fuel expense, while a floating storage 
battery at the end of a long feeder is oftentimes more expensive to install 
and operate than some of the other systems described later. The direct- 
current generating system for larger supply is rapidly becoming obsolete, 
except in localities where the conditions are very favorable for its retention. 

2. Alternating current generation and transmission to rotary converter 
substations. — This system is being used almost entirely for our suburban 
roads and larger city systems. Alternating current generation and trans- 
mission offers the advantage of the ability to transmit great power over 
long distances at very high potentials, in some cases reaching 60,000 volts, 
so that the copper expense is relatively small. New York City is fed entirely 
from rotary converters which receive their power from alternating current 
generators and alternating current transmission lines at 11,000 and 6,600 
volts. The office of the rotary converter substation, which was first used 
in 1897, is to reduce the high potential alternating current to low potential 
alternating current, then convert it into 600 volts direct current which feeds 
into the trolley or third rail, as the case may be. 

3. Three-phase alternating current feeding direct into high potential trolley 
and thence into three-phase motors upon the cars is used on some European 
roads. 

4. The single-phase alternating current commutating motor has been devel- 
oped in several forms since 1904, and there are now quite a large number 
of roads' operating in this country and abroad, using this type of motor. 
This motor is said to be more flexible than the three-phase motor, as it has 
a variable speed characteristic very similar to that of the direct current 
series motor. Its application in the railway field is therefore much more 
general and it will undoubtedly find considerable use in suburban work 
and in the heavier class of electric railways. 

Train friction. — The resistance offered by air against the front and 
sides of a rapidly moving car forms a very important factor and has been 
the subject of a large number of experiments. The most complete are 
probably the Berlin-Zossen experiments where speeds of 125 miles per hour 
were reached and wind pressures noted. A large number of formulae have 
been introduced by different authorities covering the resistance offered by 
the air, rails, journals, etc., when operating single cars and trains at different 
speeds. The formulae developed by steam railroad experimenters using 
heavy trains of many cars may be discarded as worthless when applied to 
electric traction using single car units. In the same way the results obtained 
from the operation of single cars cannot be applied to trains, as the wind 
friction of the succeeding cars is not as great as that of the leading car. 
These train friction results will be treated and commented on later on in 
this chapter. Wind friction plays a very important part in determining 
the power consumption of electric cars operating at high speeds, and both 
the energy consumption and capacity of the motive power plant must be 
carefully determined with a full experimental knowledge of wind friction 
in view. [ 

Car Equipments. — Car equipments have increased from motors of 
25 h.p. for small single-truck cars on city streets to motors of 550 h.p. each, 
as in the "Mohawk" type of electric locomotive designed for the New York 
Central Railroad. Electric motors can be designed to meet practically any 
conditions of operation, but the standard lists of manufacturers run from 



I 



614 ELECTRIC RAILWAYS. 

25 h.p. to 200 h.p. in about 25 h.p. steps, in the larger sizes, and less differ- 
ence in capacities in the smaller sizes. It is better to refer to the manufac- 
turers when a motor is to be selected for a given class of service which 
differs materially from a known service upon which full data is at hand. 
With such a wide range in capacity of motors it is necessary to study the 
conditions very carefully in order to properly determine the correct size of 
motor to use. Some general curves are given later from which reasonably 
correct approximations can be made, but these should be verified by con- 
sultation with experts in motor design. 

locomotives. — Electric locomotives have been built for a variety of 
purposes from yard shifting to the hauling of passenger trains weighing 900 
tons at speeds approaching 60 miles per hour. Nearly all these electric 
locomotives so far have been equipped with direct current series wound 
motors operating at 600 volts. A number of locomotives in Europe, how- 
ever, have been equipped with three-phase alternating current motors and 
a few with single-phase motors. In this country there are now in operation on 
the Spokane & Inland Railway, 1907, six 50-ton locomotives, each equipped 
with four 150 h.p. single-phase motors arranged to operate on either 600 
volts direct current, or 6600 volts single-phase alternating current. The 
Westinghouse Electric & Manufacturing Company, who built these locomo- 
tives, have recently completed thirty-five 88-ton electric locomotives, each 
equipped with four 250 h.p. single-phase motors arranged to operate on 
either 600 volts direct current, or 11,000 volts single-phase, alternating 
current for the New York, New Haven & Hartford Railroad, and also six 
60-ton locomotives, each equipped with three 240 h.p. motors for operation 
on 3300 volts alternating current for use by the Grand Trunk Railroad in 
the Sarnia Tunnel. The use of electric locomotives is rapidly increasing 
as the economic operation and other advantages of their operation are 
appreciated. 

]>esirable Points in motors and Car Equipment. — It is desir- 
able that motors should be electrically sound, i.e., that their insulation should 
be high, mechanically strong, and waterproof. It is of great advantage in 
this connection if the entire frame of the motor can be insulated from the 
car truck and consequently from the ground, thus relieving the insulation 
of the armature and fields of half the strain. The mechanical difficulties 
in the way of accomplishing this, however, go a great way towards counter- 
balancing the advantage gained. 

A high average efficiency between three quarters and full load should be 
obtained if possible, but mechanical points should not be neglected to obtain 
this. 

A motor should run practically sparkless up to § of its rated capacity. A 
low starting current obviously is desirable, and for obtaining this nothing 
is better for continuous current operation than a multiple series controlling 
device, which cuts the starting current in half. This device also enables 
cars to be run at a slow speed with good efficiency. 

Mechanically, the motor should be simple. The fewer the parts, and 
especially the wearing parts, the better. It should be well encased in a cover- 
ing strong enough not only to keep out water, pebbles, bits of wire, etc., 
encountered on the track, but to shove aside or slide over an obstruction 
too high to be cleared. At the same time, the case should be hinged so that 
by the removal of a few bolts access can be had to the whole interior of the 
motor. The brush holders and commutator should be easily accessible 
through the traps in the car floor at all times. As much of the weight of 
the motor as possible should be carried by the truck on springs ; if practicable 
all of it. This arrangement saves much of the wear and tear on the tracks. 

A switch in addition to the controlling stand should always be provided, 
by which the motorman himself can cut off the trolley current, in case of 
accident to the controlling apparatus. 

Roads having long, steep grades should have their cars provided with a 
device for using the motors as a brake in case the wheel brake gives out. 
There are several methods of accomplishing this, but limited space prohibits 
any description of them. 

Last, but by no means least, all wearing parts should be capable of being 
easily and cheaply replaced. 



WEIGHTS OF RAILS. 
weights OF RAIIS. 



615 



Pounds per 


"Weight per Mile. 


Weight per 1000 7 . 


Yard. 


Long Tons. 


Long Tons. 




640 




986.7 




25 


39 2240 
320 


39.286 


7 ^240 
2080 


7.441 


30 


47 2240 


47.143 


8 2240 
933.3 


8.929 


35 


55 
1920 


55 


10 2240 
2026.6 


10.417 


40 


62 2240 
1600 


62.857 


11 2240 
880 


11.905 


45 


70 2240 
960 


70.714 


13 2240 
635.5 


13.393 


48 


74 2240 
1280 


74.428 


14 ~2240 
1973.3 


14.284 


50 


78 2240 
1600 


78.571 


14 2240 
1066.7 


14.881 


52 


81 2240 
960 


81.714 


15 2240 
826.6 


15.477 


55 


86 2240 


86.428 


16 2240 


16.369 


56 


88 
320 


88 


1604.4 
16 2240 

586.7 


16.667 


58 


91 2240 
2080 


91.143 


17 2240 
^1920 


17.262 


58} 


91 2240 
640 


91.928 


17 2240 
920 


17.411 


60 


94 2240 
960 


94.286 


17 2240 
1013.3 


17.857 


62 


97 2240 


97.428 . 


18 2240 
1680 


18.452 


63 


99 
1760 


99 


18 2240 
2013.3 


18.75 


63} 


99 2240 

1rtO 320 


99.785 


18 2240 
773.3 


18.899 


65 


102 2240 
103 1600 

2240 


102.143 


iy 2240 
1440 


19.345 


66 


103.714 


19 2240 


19.643 




irv. 1120 




1773.3 




66} 


104 2-240 


104.5 


19 ^2240" 
2106 


19.792 


67 


105 

2240 

1920 


105.286 


19 2240 
533.3 


19.940 


68 


106 2240 


106.857 


20 ^240 
2000 


20.238 


70 


110 
111 280 


110 


' 20 2240 
293.3 


20.833 


71 


2240 


111.125 


21 ~2240 


21.131 



616 ELECTRIC RAILWAYS. 

WJEIOHTS OF It AIL§ — Continued. 



Pounds per 
Yard. 


Weight per Mile. 
Long Tons. 


Weight per 1000 '. 
Long Tons. 


72 
75 

77 
78 
80 
82 
85 

90 
91 

98 
100 


320 
113 2240 

1920 
117 2240 

121 

122^ 
2240 
1600 

125 2240 
1920 

129 2240 
1280 

133 2240 

960 
141 2240 

143 

154 

„320 
157 2240 


113.143 
117.857 

121 

122.143 

125.714 

129.857 

133.571 

141.428 
143 
154 
157.143 


960 
21 2240 

720.2 
22 2240 

2053.3 

22 2240 
480 

23 2240 
1813.3 

23 2240 
906.6 

24 2240 
666.6 

^2240 

1760 

26 2240 

^186.6 

27 2240 

373.3 
29 2240 

1706.7 
29 2240 


21.429 
22.322 

22.917 
23.214 
23.810 
24.405 
25.298 

26.786 
27.083 
29.167 
29.762 



For iron or steel weighing 480 lbs. per cubic foot : Cross-section in square 
inches =: weight in lbs. per yard -7- 10. 



Gross tons of rails in 1 mile single track — 



weight per yard X 11 



RADII OF CITRVEi FOR DIFFEREUT Dt^KHKM 
OF CURVATURE. 





CO +a 

■js « 




GO ^J 

P <Q 




02 -fj 

P O 





CO ■*> 

P O 
2 <» 

«.g 




CO -+J 

P <£> 


i 


5730 


ii 


522 


21 


274 


31 


187 


41 


143 


2 


2865 


12 


478 


22 


262 


32 


181 


42 


140 


3 


1910 


13 


442 


23 


251 


33 


176 


43 


136 


4 


1433 


14 


410 


24 


241 


34 


171 


44 


133 


5 


1146 


15 


383 


25 


231 


35 


166 


45 


131 


6 


955 


16 


359 


26 


222 


36 


162 


46 


128 


7 


819 


17 


338 


27 


214 


37 


158 


47 


125 


8 


717 


18 


320 


28 


207 


38 


154 


48 


123 


9 


637 


19 


303 


29 


200 


39 


150 


49 


121 


10 


574 


20 


288 


30 


193 


40 


146 


50 


118 



ELEVATION OP OUTER RAIL ON CURVES. 



617 



GRADES 


1 % PER CEIT A N 1> RISE 1 I¥ FEET. 




Rise in Feet at Given Distances. 


Per Cent Grade. 










500 Feet. 


1000 Feet. 


5,280 Feet (1 Mile). 


* 


2.5 


5 


26.4 


1 


5 


10 


52.8 


1.5 


7.5 


15 


79.2 


2 


10 


20 


105.6 


2.5 


12.5 


25 


132 


3 


15 


30 


158.4 


3.5 


17.5 


35 


184.8 


4 


20 


40 


211.2 


4.5 


22.5 


45 


237.6 


5 


25 


50 


264 


5.5 


27.5 


55 


290.4 


6 


30 


60 


316.8 


6.5 


32.5 


65 


343.2 


7 


35 


70 


369.6 


7.5 


37.5 


75 


396 


8 


40 


80 


422.4 


8.5 


42.5 


85 


448.8 


9 


45 


90 


475.2 


9.5 


47.5 


95 


501.6 


10 


50 


100 


528 


11 


55 


110 


580.8 


12 


60 


120 


633.6 


13 


65 


130 


686.4 


14 


70 


140 


739.2 


15 


75 


150 


792 



Note No. 1. — For other distances interpolate the table by direct multi- 
plication or division. 

ELEVATIOIV OF OUTER UAIL OI¥ CURVES. 





o . 






Speed 


in Miles per 


Hour 








10 


15 


20 


25 


30 


35 


40 


45 


50 


60 


a 


« 






Elev? 


ition c 


)f Outer Rai 


L in Ir 


ches. 






i 


5730 


A 


ft 


i 

4 


i 7 * 


s 


41 


1ft 


If 


iH 


2* 


2 


2865 


¥ 


>? 


A 


,* 


1* 


ift 


2ft 


2| 


2ft 


4H 


3 


1910 


tIt 


± 


+i 


Aft 


i* 


2* 


*ft 


4* 


5* 


7# 


4 


1432 


i 


* 


A 


}tt 


2* 


3f 


*i 


4ft 


m 


9f 


5 


1146 


S 


% 


i* 


« 


% 


d. 3 


5ft 


6J 


8* 


12ft 


6 


955 


T'* 


,** 


H 


*ft 


?** 


5 


<*ft 


8* 


10ft 




7 


818 


* 


{ft 


ltt 


3 


!ft 


5£ 


1% 


9ft 


llf 




8 


716 


ft 


i 


2 T 3 s 


3ft 


3* 


6H 


ffi 


10fr 






9 
10 


636 
573 


h 


J* 


2* 
2f 


3fi 

4* 




7* 

8ft 


10| 


12H 






11 
12 


521 
477 




1* 


3 

3ft 

3fif 


4Ii 

5* 


4 

7 T 5 ^ 


9* 










14 


409 


H 


2 T 3 S 


5H 


8 T 9 TT 


111 










16 
18 
20 


358 
318 
286 


1A 

if 


Ol 

2f 
3ft 


4i 

5& 


6H 

7f 
8£ 


m 

10| 

12 













Note No. 1.— When E = elevation in inches of outer rail above the hori- 
zontal plane: 

V: 

R: 



: velocity of car in feet per second ; 
- radius of curve in feet ; 
V 2 
Therefore E = 1.7879 —when gauge of track is 4'-8£" 



R 



618 



ELECTRIC RAILWAYS. 



§PIKE§. 



Size. 


No. per Keg of 
200 Lbs. 


Lbs. per Spike. 


Spikes per Lb. 


4*X£ 


533 


.3752 


2.66 


5 Xt*s 


650 


.3077 


3.25 


5 X* 


520 


.3846 


2.6 


5 Xi 9 s 


393 


.5089 


1.96 


bhXh 


466 


.4292 


2.33 


5* X r 9 s 


384 


.5208 


1.92 


6 Xft 


350 


.5714 


1.75 


6 Xf 


260 


.7692 


1.3 



spikes jpjeu looo a\d per mile ii^gle 
track:, with four spikes per tie. 



Spacing of Ties. 


Per 1000 7 . 


Per Mile. 


10 ties to 30 7 rail 


1333£ 


7040 


11 " " " " 


1466| 


7744 


12 •* " " " 


1600 


8448 


13 " «• " " 


1733£ 


9152 


14 " " " " 


1866| 


9856 


15 " " " " 


2000 


10560 


16 " " " " 


2133£ 


11264 



JOINTS PER MILE 


OE SINGLE 


track:. 




Per lOOCX. 


Per Mile. 


Joints — 30 / rails 

Angle bars 


66§ 
133| 

266§ 
400 
533£ 
800 


352 
704 


Bolts — 4 hole bars 

6 " " 

8 » " 

" 12 " " 


1408 
2112 
2816 
4224 



TIES PER lOOO A]¥» PER MILE, 




BOARD FEET, CUBIC EEET, AID SQX T ARE EEET 
OE BEARING SUREACE PER TIE. 



Size. 


Board Feet. 


Cubic Feet. 


Bearing Surface 


5" X 5" X V 


14.56 


1.213 


2.91 


5" X 6" X V 


17.5 


1.458 


3.5 


5" X 7" X V 


20.41 


1.7 


4.08 


5" X 8" X V 


23.33 


1.944 


4.66 


6" X 6" X V 


21 


1.75 


3.5 


6" X 7" X V 


24.5 


2.041 


4.08 


6" X 8" X V 


28 


2.333 


4.66 


6" X 9" X 7' 


31.5 


2.625 


5.25 


6" x 10" x 7' 


35 


2.916 


5.83 


0" X 8" X 8' 


32 


2.666 


5.33 


C" X 9" x 8' 


36 


3 


6 


6"xl0" x 8' 


40 


3.333 


6.66 



PAVING. 



619 



REPORT OF U. S. DEPARTMENT OF AGRICUI- 
TURE ON DrRABILITY OJP RAILROAD TIES. 

White oak 8 years. 

Chestnut 8 « 

Black locust 10 " 

Cherry, black walnut, locust 7 « 

Elm G to 7 " 

Red and black oaks 4 to 5 " 

Ash, beech, and maple 4 « 

Redwood 12 " 

Cypress and red cedar 10 " 

Tamarack 7 to 8 " 

Longleaf pine 6 " 

Hemlock 4 to 6 " 

Spruce 5 « 

PAVMG. 

Paving prices vary so that it is difficult to state even an approximate cost 
chat will not be dangerous to use. Prices are not at all alike for asphalt, 
even in cities in the same localities ; other styles vary according to prox- 
imity of material, cost of labor, and amount of competition. 

Square yards of paving between rails, 4' 8|" gauge, less 4" for width of 
carriage tread : 

Per 1000 / run = 485.89 sq. yards. 
Per mile run = 2565.5 
Square yards paving for 18" outside both rails : 

Per lOuO 7 run rz 333£ sq. yards. 
Per mile run = 1760 " 



Approximate Cost of Paving 



(Davis.) 



PAVEMENT 




Cost of all Material 
and Labor. 


Cost of 
Tearing up 
Existing 
Pavement 
and Repla- 
cing as 
Found. 




u 


JO 

B 

O e« 
u 

<0 


O 

cu.5 



"So 

U 

PM 




Granite blocks on gravel foundation 
Gravel blocks on concrete foundation 
Asphalt on concrete foundation . . 
Vitrified brick on broken stone . . . 

Wood without concrete 

Cobble without concrete 

Macadam 




$ 

2.80 
3.60 
3.80 
2.15 
1.50 
2.00 
1.00 


$ 

2.24 
2.88 
3.04 
1.72 
1.20 
1.60 
.80 


$ 
12000 
15500 
16000 
9000 
8000 
8500 
4500 


$ 

.35 
.45 

.45 

.30 
.50 


$ 

1900 
2400 

2400 

1600 






2700 



ESTIMATE OF TRACK IAYOG FORCE, 

One engineer, 1 rodman, 1 foreman of diggers, 1 foreman of track-layers, 
tspikers, 20 laborers, 2 general helpers. Such a gang can lay from 400 to 
900 feet of single track per day. 

In case it is desired to proceed more rapidly, the above number of men 



620 



ELECTRIC RAILWAYS. 



should be increased proportionately, omitting the engineer and rodman, as 
these two will be able to handle any ordinary number of gangs, no matter 
how widely scattered, if a horse and buggy is placed at their disposal. 

Tools for Track Gang* as Above. — One portable tool-box pad- 
locked, 1 small flat car, 1 portable forge, 4 cold chisels, 2 ball pein hammers, 
6 lbs.; 1 sledge,12 lbs.; 2 axes, 2 adzes, 1 cross-cut saw, 1 large double-handled 
saw, 6 track wrenches, 2 monkey wrenches, 1 complete ratchet track drill 
with bits, 1 track "Jimmy" for bending rails, 1 reel line cord, braided; 30 
picks, 15 extra pick-handles, 25 long-handled, round-nose shovels, 6 short 
handled, square-nose shovels, 10 tampers, 5 wheelbarrows, 2 track gauges, 
1 level, 1 straight-edge, 4 pair rail tongs, 6 spiking hammers, 3 crow-bars, 
one end sharp, the other end chisel-pointed, 2 spike claw-bars, 1 engineer's 
transit, 1 leveling-rod, 10 surveyor's marking-pins, 1 steel tape, 10 red lan- 
terns, 1 box lump chalk, 1 squirt oil-can, 1 quart black oil, 5 gals, kerosene, 
I flag-rod, 1 paper of tacks, 1 broad-blade natchet. 



RAILWAY TIRXOUTS. 

By W. E. Harrington, B. S. 

For example, assume a railway to operate 4 cars, the distance between 
terminals four miles, the time of round trips 60 minutes, and the headway 
15 minutes, with a lay over at each end of five minutes. Take a piece of 
cross-section paper, and make the 
vertical lines represent distance, 
and the horizontal lines represent 
time. 

The time necessary to run from 
terminus to terminus is half of 60 
minutes, less £ of ten minutes (the 
layover time), or 25 minutes. Let 
each division on the ordinate axis 
represent the distance traversed by 
a car in one minute, which in the 
above case is 844.8 feet per minute,as- 
suming that the car is to run at the 
average speed of 9.6 miles per hour. 
Let each division on the axis of ab- 
scissas represent five minutes. The 
first car will travel from terminus to 
terminus as represented by the diag- 
onal line OA. This line shows the 
car's position at any instant of 
time, assuming, of course, that the 
car is running at a uniform rate of 
speed. The car upon its a nival at 
the other terminus will have a lay- 
over of five minutes as repre- 
sented by the horizontal space AB 




Fig. 1. 



Location of Street Railway 
Turnouts. 



Upon the expiration of the time of lay-over the car starts upon its return 
run. This determines the locus of the several turnouts, as the car has to 
pass each of the remaining cars. The line of the return run is represented 
by the line BC. Upon the arrival of the car at the original terminus and a 
lay-over of five minutes, the cvcle of trips will be repeated. During tne 
time the first car is running its round trip the other cars are leaving at in- 
tervals of 15 minutes, as represented by the lines DE. FG, and HI. Where 
these three lines intersect the line BC turnouts must be located, as the cars 
meet and pass at these points. The distance apart of the turnouts, as well as 
th'eir distance from the starting terminus O, may be readily determined by 
projecting the intersections on the axis of ordinates OY. 

1. The number of turnouts for a given number of cars is one less than the 
number of cars running. 



RAILWAY TURNOUTS. 621 

2. The time consumed running between turnouts must be the same 
between all the turnouts. For instance, if it is found necessary to irregu- 
larly locate turnouts for any reason, then the time consumed by a car run- 
ning between these two turnouts farthest apart determines the time the 
cars must run between the remaining turnouts, even though two or more of 
the turnouts be only a slight fraction of the distance apart of the two 
greater ones. 

3. The time consumed running between two consecutive turnouts is one- 
half the running time between cars. 

For determining the distance apart of turnouts without the aid of graph- 
ical methods : 

Rule. — To the length of the railway from terminus to terminus add the 
distance a car would travel running at the same rate of speed as running on 
the main line, for the time of lay-over at one terminus. Divide the above 
result by the number of cars desired to be run, the result is the distance 
between turnouts. Multiply this latter result by two less than the number 
of cars, and deduct the result obtained from the length of the line from ter- 
minus to terminus, and divide by two. The result is the distance from 
either terminus and the first adjacent turnout. 

To operate more or less cars on a railway than it is designed for is a ques- 
tion most frequently met in railway practice. 

Rule 1 tells us that we must have one turnout less than the number of 
cars running. In Fig. 1 we have four cars and three turnouts. If we pro- 
pose running three cars we would use two turnouts, by omitting the middle 
turnout. The result is at once apparent ; for according to Rule 2, the time 
to run between turnouts is determined by the time consumed in running 
between those two turnouts farthest apart. Since the distance is doubled, 
the time consumed is doubled. Where with four cars, with fifteen minutes 
between cars, and sixty minutes for the round trip, with three cars the time 
between cars as by Rule 2 is thirty minutes, and the time of round trip is 
ninety minutes, making at once a very pronounced loss. . 

The better plan, and the one usually pursued by railway managers, is to 
run the lesser number of cars on the same trip time as the railway was 
designed for. In our example above, the three cars would be run as if the 
four cars were running, with the exception that the space which the car 
should be running in will be omitted, leaving an interval between two of 
the cars of thirty minutes, giving only the loss occasioned by the omission 
of one car. 

Another method to pursue, especially so where additional cars will be 
run at times, such as holidays, excursions, and other times of travel requir- 
ing more than the regular number of cars to accommodate the travel, is to 
provide and locate more turnouts. The expense of doubling the number of 
turnouts, while they would be a great convenience, would not be warranted 
without the railway were doing a large and growing business, with a fluctu- 
ating number of cars in service. Two cases should be considered. 

First — If a certain fixed number of cars are to be operated for the greater 
portion of time and the extra cars for odd and infrequent intervals, locate 
the turnouts to suit the regular business. 

Second— In the case of a railway running an irregular number of cars — 
for instance, a railway running a heavy business at certain times of the day 
— as the lesser number of cars are subordinate to the greater number, 
locate the turuouts to run the greater number of cars the most efficiently. 

In conclusion, we might state that the grades, the running through 
crowded business streets, stoppages occasioned by grade railroad crossings, 
and varying business, all enter in and must be considered while designing. 



622 



ELECTRIC RAILWAYS. 



i:le(thi( hailway automatic block 

SICHJTAXJLIJra. 

By Charles F. Hopewell, S.B. 

Block signalling on single-track railways accomplishes two purposes, 
namely, that of ensuring safety and of obviating delays in traffic necessitated 
by cars always meeting at predetermined turnouts. 

Electric Railway Signal Systems have three positions of signal display, 
viz.: normal; safety, indicated by green; danger, indicated by red. The red 
signal is at the leaving end of a block and the green signal operating in 
unison with it is at the entering end of the block. Were it not so, a car 
entering a block could not determine if it set a danger signal or the same 
was set by another car entering from the other end. This requires the 



TypaA. 



Douh/eTracks ^\poubk Acting Tnilley Switch 

=5 ia HO 



OeuhleActmo f > -*c OoubleActing 

< Sinale Track. MyS mtct L/ Turn^^out. ^ro lle ^wifch^ 



Swirc'hi'/nel] p'iff'n'o/I/n?s"\ rs'rsK'n'L'ines. 



-JOOfeet *-" b? ' , M *ft— 

Signa/ 3c a Signal oca 



Swikhi'nes 1 j" 
loo fee t - A * 



—/aofect-^ 

SlflMlSoj 



Sin gle Act ing TrvS/eyJWitcne*. 
>eCorLenf~f?i 




TypeB. 



Single AcringTrvlleySwhthes 



- Sing It Track> 



trleng/fcd 1 \ bjN/^„ 

-O^ .l— I *>rn-vt r — V^ 



S#itc'nLin*s. ] XS/'g no/ lines Swirch L ■', 



—won 

•Si'nqleActinq 
TrollejSWJTtAi 



Br^-g? 



Double fenV^'^ 



Signal Bo*. SignalBbx, 

TypeC 

Single ^ Trac, 



dt 



S/gnetBax. 



Oovb/'Actinf 
Tnli/Stfi*y Turrtciif 



-Noft- 
Arro#jSh0\ 
CarDirtcTion. 



socft. ^1 — J ^T_J- /aoA. £ 



ggTxy ^i 



$fah 



Jw'i/cnUne's' ' 



SifnolBo/. SicjnalBax 

Typical Methods of Blocking. 



UNI SIGNAL CO. 
BOSTON 'Mastf 



Fig. 2. 



normal position of signalling to be when no car is in the block. A motorman 
of a car approaching a block may have one of three indications signalled 
to it: No distinctive signal or light, indicating that the block is clear; a 
green signal indicating that a car has entered the block proceeding in the 
same general direction as the observing car, and a red signal indicating that 
a car has entered the block from the distant end and is coming towards the 
observer. 

There are three distinctive methods of blocking a single track for operating 
in both directions. These are represented in Fig. 2. Type A shows 
the trolley switches which operate the signalling mechanisms located at 
each end of the section between turnouts or double tracks. The signal 
boxes are set one pole stretch in advance of the trolley switches. This 
type requires two differentiating double-acting trolley switches per block. 
A condition sometimes happens that a car has a red or danger signal set 
against it just before it passes under a trolley switch, due to a car entering 
the block from the distant end. Under this condition the car could not be 
stopped before it had passed under the switch. It will, therefore, be neces- 
saiy that when the car backs out it must have its trolley pulled down, and 



BLOCK SIGNALLING. 623 

coasts under the switch, otherwise it would restore the signal set by the 
car already in the block. 

Type B. — In this type the trolley switches are located on the double 
tracks or turnouts. These switches are single acting and will only set or 
restore the signal as arranged for. This type requires four switches per 
block, but has the advantage that a car can pass under the switch in the 
reverse direction without restoring the signal. It requires that the cars 
shall take the turnouts in one fixed direction. 

Type C represents a combination of Type A and Type B, and can be 
used to meet special conditions of road and travel. 

The Requirements of a jSig-nal System are as follows: 

Mechanical and electrical simplicity of all signal movements and appliances 
Must be automatic, non-interfering and interlocking; 
Must be incapable of wrong indications under any of the following men- 
tioned conditions, and must not permit restoring to normal except under 

normal conditions of operation, otherwise it could be set or reversed by 

another car entering the block. 

Loss of current on signal lines. 

Cross of signal lines. 

Ground on the setting signal lines or on the restoring signal lines. 

Cross with the trolley wire between the setting or restoring signal lines. 

If the signal is set in one direction and the line then opened, it must be 
incapable of being set from the other direction, i.e., the signal must be 
interlocking 

If a car should run under a trolley switch when the signal is set against it, 
it must not restore the signal, i.e., it must be non-interfering. 

It should employ as few wires as possible. 

It must be impossible to get two safety signals should cars operate the 
switches at each end simultaneously. In this case both signal move- 
ments would set, and it is desirable that they may be automatically 
restored by the car leaving the block without being required to be manually 
reset. 
The installation of an electric railroad signal requires at each end of a 

block which passes cars in both directions the following, with the necessary 

connections. 

A signal movement and a lighting and extinguishing switch. 
The wires required are these: 

A lighting switch wi^e from same to signal box. 

An extinguishing switch wire from same to signal box. 

The signal line wires. 

Generally a lighting and an extinguishing signal line wire running between 
the signal boxes at each end of the block. 

A ground connection between signal movement and rail. 

A permanent feed connection between signal movement and trolley. 

A lightning arrester should be attached to the permanent feed wire and one 
each to the signal line wires. 

It should be remembered that the trolley is connected to the ground when- 
ever the signal is set and thus a path of low resistance and inductance is 
provided for any lightning discharge which may take place on the trolley 
lines. 
The above is based upon the signal systems that are in practical operation 

to-day on trolley roads, and does not apply to systems as used upon elevated 

railroads. The latter are operated by track instruments and give only 

clear and danger indications. 

The manual system consists simply of a group of lamps at each end of a 

block, and a switch to light and extinguish the same. This system operates 

ina manner similar to the automatic system referred to in the first part of 

this article but requires the stoppage of the car to set the same or to restore 

the signal, and in practice it has been found that the signal has at times been 

tampered with by people who are able to reach the switches which are 

located on poles alongside the track. 

The trolley switches in use are of two types. One consists of a parallel 

way upon which the trolley runs and in so doing connects the two sides of 

the switch. One side is permanently connected to the trolley wire and 

the other to the signal movement. This switch will not differentiate in 



624 ELECTRIC RAILWAYS. 

direction and must therefore be placed upon turnouts and not upon the 
main line. 

The other type is a mechanically operated switch which has a pendant 
lever hanging down and straddling the trolley wire. The trolley wheel 
strikes this and moves it in the direction in which the car is going. As the 
pendant arm is about four inches long it remains in contact with the trolley 
wheel only about one-fifth of a second for a car speed of a mile per hour and 
proportionally less for higher speeds. This requires that all switches have 
a retarding device to keep the contacts closed longer than would the trolley 
wheel. The most common switches to-day use a pallet and wheel escape- 
ment as retarding devices. 



Typical Automatic Two-JLine Wire. Non-Interfering* 
Block Signal. 

The following description of the Block Signal System made by the Uni 
Signal Co. of Boston, Mass., is illustrative of what such a signal must accom- 
plish. Fig. 3 shows the wiring for a complete block and Fig. 4 the detail 
wiring at each end of the block. 

The signal movement consists of iron back plate upon which are mounted 
three magnets known respectively as the lighting magnet, extinguishing 
magnet, and locking magnet. The first two mentioned are of 70 ohms 
resistance while the third is of 10 ohms resistance. The magnets are of the 
well known semaphore type. The lighting and extinguishing magnets have 
notched iron cores in which loosely play one arm of a switching lever. 
In the extinguishing magnet there is also an additional magnet core which 
when down closes a pair of contacts. The other two contacts are shown 
in Fig. 4 directly above the large magnets and are circular contact discs 
loosely mounted upon a rod between stops. These rods rest directly upon 
the magnet cores and are moved to open or close the contacts as the move- 
ment operates. The armature of the locking magnet is attached directly 
to the rod over the extinguishing magnet and is so adjusted that it is against 
its seat when that contact is made and the rod in its lowest position. The 
lamps are of 110 volts and one-half ampere and the resistance plate of 600 
ohms is clearly shown. 

The operation of the signal is as follows, and can be seen by reference to 
Fig. 3. t . 

When a car enters a block it causes current to pass from the trolley wire 
through the lighting magnet and resistance plate to ground at that end. 
This causes the switch lever to be thrown over to the left hand contact, 
thus causing current to be taken from the leaving end of the block, passing 
through the red lamp, locking magnet at that end, and then through the 
lighting signal line to the entering end, where it traverses the green lamp 
and resistance plate to ground. 

To extinguish the signal, current is taken from the trolley at the leaving 
end of the block through the extinguishing magnet at that end, thence 
through extinguishing line to the entering end and through the extinguishing 
magnet at that end to ground through the resistance plate. It might appear 
at first sight that there would be current through both magnets at the enter- 
ing end, and under such condition impossible for the switch lever to be 
restored to its normal position. Examination, however, will show that 
as soon as current is established in the extinguishing circuit the gravity 
armatures, so called, at their lower end, are raised, and the one in the leaving 
end of the block cuts off the current of the lighting magnet in the entering 
box, thereby allowing the extinguishing magnet in that box to operate.^ By 
taking the permanent feed from the leaving end and also opening that circuit 
at that end, it will be apparent that grounds on the lighting line will not 
prevent the restoration of the signal. A cross between the signal lines will 
not restore the signal, but will extinguish the green signal, which will, 
however, relight as soon as the cross is removed. Grounds on either lines 
will not restore the signal when set. Ground over 1500 ohms resistance will 
not affect the operation of the signal even if on both signal lines at the same 
time. Tlri s . is equivalent to £ ampere leak while the normal current in the 
signal circuit is only \ ampere. Loss of current will not restore the signal 



BLOCK SIGNALLING. 



625 



when set and when the current is returned the signal will indicate the same 
as before. 

Should the lighting circuit be open after the signal is set, for instance by a 
lamp being burned out, and another car at distant end should enter the 
block, it will be seen by Fig. 3 that the switch lever in that signal move- 
ment at that end would be thrown over to the left-hand contact as in the 
box shown at the left hand, the result being that the permanent feed is cut 
off at both ends and no signal is obtained. Lack of green signal on entering 
is construed as a danger or cautionary signal. 

Suppose that a car should pass under the lighting switch at the red lamp 
end of a block, as represented by the movement at the right hand side 
of Fig. 3, it will be seen that current will be taken through the lighting 
magnet at that end and thence through the resistance plate to ground. This 



Trolley Wire, 

light ivg M 1 Y-£icr>/to(//shtni 




SnteringBtd ofB/ock 

Jig not Set 
Green LamfiL rghted. 



L ft Lighting 

L.A± ightntng Arrestor. j^ 



LeavingEndofB/ddf 



SignatSet 
1La 



Cqmpletefflock Signal fo<* Lamp Lighted. 
Double AcringTrolley Switches 



Fig. 3. 



would tend to move the lever or switch arm over to the left hand contact, 
and thus put out the signal were it not for the locking magnet whose sole 
function is to prevent this movement. As soon as the lighting circuit has 
been established the locking magnet at the red end is energized and its core 
being against its seat at that time it is held there. To the core is attached 
a tail rod at the other end of which is one of the contact discs mentioned 
before. This tail rod pressing against the lever arm prevents the lighting 
magnet from operating it. It will be noted that the locking magnet is 
instantaneous as it has no moving part to operate before locking, and on 
account of its closed magnetic circuit is more powerful than the lighting 
magnet, whose armature is retracted at that time, and has a large air gap 
in circuit. The signal thus is made non-interfering. 



626 



ELECTRIC RAILWAYS. 



In Type B signal made by the same company, the wiring is the same 
except that the resistance plate is placed in the permanent feed, and two 
additional graphite resistance rods of 600 ohms are placed in each trolley 
switch leg. Each lamp is further protected by a paper shunt which closes 
the circuit when the lamp burns out. Furthermore there is a magnet opera- 
ting a red, and one operating a green semaphore disc signal, which are cut 
into the circuit adjacent to the red and green lamps. 

The trolley switches are double acting and differentiating, operating as 



EtiinguishinqSignalLirtt. 



■Srr/ftS>. 
2 /t/n/t,fi/4* 




Bex v 

F*$r/n orttnt Fits*. 

F~vs*2#mp$. 



X. rfMrnq firmafrr*. 
] 



WIRING Fo^2 WIRE 
Automatic Block 
Signal 

Uni Signal Co 



Switch Csntocts. 



Fig. 4. Signal Set at Entering End of Block, Green Lamp Lighter. 



follows: The first blow of the trolley wheel hits a pendant hanging over the 
wire and brings the switch contacts into mechanical lock. At the same 
time it winds up a pallet escapement, which, when it runs down, kicks the 
lock off and allows the contact to open after a predetermined time. The 
working parts are in balance and made as light as consistent with strength. 
There are two contacts, but only one common escapement. The switch 
lights when passed under in one direction, and restores the signal when 
operated in the other direction. A time element is necessary, as it requires 
about \ second for the signal mechanism to operate. The power required 
to operate the signal switch is 2h pounds pull, while the tension on a trolley 
wheel to hold it against the trolley wire is over twenty pounds. 



BLOCK SIGNALLING. 



627 



[Distributed Signal Block System. 

(Developed by R. D. Slawson, Electrical Engineer of Easton Transit Co.) 

This is a manual system, and is used by the Easton Transit Company on 
the Easton, Palmer and Bethlehem division, and differs from others in having 
the signals distributed along the line between turnouts. There are two sets 
of signals, one being used for out-bound and one for return cars. The signal 
lamps .are enclosed in galvanized iron boxes, attached to poles along the 
line. Signal poles are also painted with two 12 inch bands of white, and a 
band of either red or green, as the case may be. Switches are located at 
each end of the turnouts on poles and the covers are marked "Throw on " 



Trolley Wire 





~^~ 



Fiq. 5. Diagram of Connections of Slawson's Distributed Signal Block 
System for Single-Track Railways. 



and "Throw off," and each conductor is responsible for maintaining his own 
right of way. 

No. 14 insulated iron wire is used for the signal circuits. 16 c.p. 110 
volt lamps are used for signals, and as the signal boxes are triangular, the 
lamp can be seen from almost any position. 

The red lamps are used for out-bound, and the green for return cars. 
The operation of the system is as follows: The conductor of a car leaving 
a terminal out-bound, first throws the switch marked 
"Throw on." This lights the five lamps in the red boxes in 
the section ahead of him, and he proceeds to the first turn- 
out, and, if there is no green lamp burning at that place, he 
throws off the red signals behind and sets the red lights in 
the section ahead. 

If a lamp should burn out while the car is running be- 
tween turnouts, warning of the fact is given by the absence 
of the red light, and by watching the green signals the motor- 
man can tell when a car is coming in the opposite direction. 

If the out-bound car, coming to a turnout, finds the red 
signal burning for the section ahead, showing that the section 
is occupied by a car going in the same direction, it must 
wait until the section is cleared by the car ahead. 

The signals may then be reset, and the car can proceed. 

Switch Used. Should a crew find that they are unable to light the red 

signals, they may use the reverse, or green signal, to the next 

turnout. On the return the green signals are used in the same manner as 

described above for the red signals and an out-bound car. 

If signal switch boxes are placed about a car's length outside of the ends 
of turnouts, cars will always approach at slow speed, which is quite desirable 
in running into a turnout. 



\ 

Slate 


Q 


1 


101 




id 


Q 









Fig. 6. 



628 



ELECTRIC RAILWAYS. 



LIST OE MATERIAL REQUIRED EOR O^E Tf ITE 

OF OVERHEAD LI1¥E FOR ELECTRIC 

STREET RAILWAY. 









1 Mile Overhead. 


Curve Overhead 
Material. 


Anchor- 


Material for 

Railway 
Construction. 


Cross 
Suspen- 
sion. 


Bracket 
Suspen- 
sion. 


Main 
Line. 


Branch 
Line. 


© 

O 

H 


age. 


H 


© 

O 


u 

H 
© 

02 


H 

© 

o 

ft 


u 

H 

© 
13) 
.9 


u 
H 

© 

o 


H 
S3 


•J 
H 
© 

O 

ft 


© 

g 


H 

O 




No. B. & S. 
H. D. Trolley 


Ft. 
Lb. 


5280 
1685 


10560 
3369 


5280 
1685 


10560 
3369 










250 

80 




z 


No. OB.&S. 
S.D. F'd'rT'ps 


Ft. 
Lb. 


400 
154 


500 
192 


90 
35 


180 
69 



















7 strand 
No. 12 span 


Ft. 
Lb. 


3600 
756 


3600 
756 






800 
168 


800 
168 


800 
168 


800 
168 


200 
42 


400 
84 


600 
122 




7 strand 
No. 15 guy 


Ft. 
Lb. 


3000 
300 


4500 
450 


1500 
150 


2000 
200 


100 
10 


100 
10 


100 
10 


100 
10 








Plain ears .... 
Strain ears .... 
Splicing ears . . . 
Feeder ears .... 


45 

1 
10 


90 

2 
20 


45 

1 
10 


90 

2 
20 


5 
2 


10 

4 


5 
1 


15 
2 


4 






Insulating caps . . 
Insulating cones . . 


45 
45 


90 
90 


45 

45 


90 
90 


7 

7 


4 
4 


6 
6 


17 
17 


4 
4 






g| Straight line . . 
«,§ Single curve . . 
£-3 Double curve . 

HI Bracket . , . 


45 


90 


45 


90 


3 
4 


3 
11 


3 
3 


5 
12 


4 




Sti 
Tu 
Se 
Ft 
Fr 
Ha 
Ey 
Ca 
Ga 
Cr< 


ain insulators . . 
rnbuckles . . . 
ition insulators 
3gS 


90 

90 

2 

45 
90 

45 


90 

90 
4 

45 
90 

45 


2 

45 
45 

48 


4 

90 
90 

48 


4 
4 

2 


4 

4 

2 


2 
2 

1 

2 


2 
2 

2 
1 

2 


2 

2 
2 


1 
2 

2 


2 
2 


og crossings . . . 
irdwood pins . . 
e bolts 


2 


st-iron brackets . 
s-pipe arms . . . 
>ss arms (1|"-18) . 




Cr< 

Bo 

La 

e 

La 

a 
La 


)ss-arm braces 

J"X8") 

Its for brackets 
&"X4") 


90 

45 
144 


90 

45 
144 


45 
45 


90 
90 














y screws for brack- 
ts ($"x7") • • • 
g screws for cross 
rms (§"x3") . . 
% screws for braces 




Poles, 125-ft. apart . 


90 


90 


45 


45 


2 


2 


2 


2 




2 


2 


Bonds 


400 


800 


400 


800 


• 














Lightning arresters . 


3 


3 


3 


3 
















Section switch boxes 


2 


2 


2 


2 






1 









STANDARD IRON OR STEEL TUBULAR POLES. 629 



ESTIMATE OE COST TO PRODUCE OAE II B LE OF 

DOUBLE TltACK OVERHEAD TROLLEY 

CONSTRUCTION EOR CTT1 STREETS. 

(Report of Bion J. Arnold, November, 1902.) 

100 Iron poles, set in concrete, at $28 $2,800.00 

50 4-pin iron cross arms, with pins and ins., at $3.95 . . . 197.50 

100 Small Brooklyn insulators for spans, at 50c 50.00 

100 Globe strain insulators for spans, at 22c 22.00 

90 Straight line hangers, at 32ic 29.25 

10 Feed-in hangers, at 50c 5.00 

140 Soldered 9-inch ears, at 16c 22.40 

12 Live cross-overs (estimated), at $3 36.00 

8 Insulated cross-overs (estimated), at $6 . 48.00 

8 2- way frogs (estimated), at $3 24.00 

3000 Feet 5-16 inch galv. strand wire for spans, at $10 per M. 30.00 

6 Strain plates (strain layout), at 32c 1.92 

12 Small Brooklyn (strain layout) at 50c. ...... 6.00 

12 Globe insulators (strain layout) at 22c 2.64 

1500 Feet i-inch galv. strand wire (strain layout), at $7 . 25 per M . 10 . 88 

20 Double hangers (2 double curve layouts), at 44c. ... 8.80 

20 Single hangers (2 double curve layouts), at 35c. ... 7.00 

1000 Feet ^-inch strand wire (2 double curve layouts), at $.725 per M. 7.25 

4 Heavy Brooklyn (2 double curve layouts), at 70c. . . 2.80 

10560 Feet 2-0 trolley wire, 4246 pounds, at 13ic 562.59 

2 00 splicing ears, at 50c 1 . 00 

Labor, placing spans, trolleys, etc 225.00 

Total cost exclusive of feeder wire $4,100.03 

Cost of feeder wire estimated average per mile 4,000.00 



$8,100.03 



STANDARD IRON OR STEEL TURULAR POLES. 

Tubular poles for electric railway lines are made up of the regular pipe 
sections, both standard and extra heavy. 
The combinations in common use are : 

Pole made of standard tubing. 

Pole made of extra heavy tubing. 

Pole made with bottom section of extra heavy tubing, and other sections of 

standard weight. 
Pole made with bottom and middle sections of extra heavy tubing, other 

sections of standard weight. 

Standard lengths are 28 feet end to end for side or line poles, and 30 feet 
for corner or strain poles. The standard joint insertion is 18 inches, and 
total weights can be calculated from regular standard pipe list (see pages 
1426-1427). Two section poles are most commonly made up of 6 and 5 and 
7 and 6 inch-pipe, for side or line poles; and 8 and 7 inch pipe for corner or 
strain poles. 

Three section poles are 6 and 5 and 4 or 7 and 6 and 5-inch pipe for side 
or line and 8 and 7 and 6-inch for corner and strain poles. 



630 



ELECTRIC RAILWAYS. 



Standard Pole JLine Construction. 

For most urban and all interurban or suburban lines, wooden poles are 
used, and are either octagon or shaved. The following cuts show common 
standards of dimensions and arrangments of cross arms, brackets, etc. 



% x 7 Lag Screws 




Fig. 7. Standard Pole Line Construction of the 
Union Traction Company of Indiana. 



DOUBLE TRACK CENTER POLE CONSTRUCTION. 



631 



Double Track Center Pole Construction. 

Electric roads use a greater distance between track centers than do steam 
roads hence permitting center pole construction, with less cost per mile 
than would be the case if double pole bracket or cross suspension construc- 
tion were used, although the latter is often preferred. 



Barb Wire 
Mach.Bolt^ 

'_ Tfl"7£- 



IJfi Top Grove Insulator 

. — .I.BOHfif.x"' 

6 "S. %"x MvJV "it* "IsProvo Glass Insulator 
3/A iW P^12^=18^i8:fe^27fe Special Insulator Pins 

78 _ „.??.— !e=^V U V ± ^J Q • , «__«_„ a. 



Carriage Bolts' 



%xl2Machine^olt y 




Special Pine Cross Arm 6x4% x'6% 
Galv. Iron Braces 24x1 }^'x % 
S(«cial Pine Cross Ana 



,J<Galv. Iron Braces S^M"* 
•3 SO'xlfc"* X" 
V Lag Screws 
"*- tfk 4" 



^ x 12 Bolt 
Threaded both Enda 



Fia. 8. Typical Center Pole Construction. 



632 



ELECTRIC RAILWAYS. 



Plate Box Poles. 

BY BUFFALO BRIDGE AND IRON WORKS 




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POLES. 



633 



TIBILAR I«0\ OR STEEL POLES. 

By Morris, Tasker, & Co. (Inc.). 



Size. 








Wrought Iron or 
Steel. 


Length. 


Weight. 


No. 1, light . 
No. 1, heavy 
No. 2, light . 
No. 2, heavy 
No. 3, light . 
No. 3, heavy 
No. 4, light . 
No. 4, heavy 








5 in., 4 in., 3 in. 

5 in., 4 in., 3 in. 

6 in., 5 in., 4 in. 

6 in., 5 in., 4 in. 

7 in., 6 in., 5 in. 

7 in., 6 in., 5 in. 

8 in., 7 in., 6 in. 
8 in., 7 in., 6 in. 


27 ft. 

27 ft 

28 ft. 
28 ft. 
30 ft. 
30 ft. 
30 ft. 
30 ft. 


350 lbs. 

500 lbs. 

475 lbs. 

700 lbs. 

600 lbs. 
1000 lbs. 

825 lbs. 
1300 lbs. 



POLES. 

Dimensions and Weights W rousht'Iron and Steel Poles. 



Length. 


Diameter. 


Weights. 


27 ft. 

28 ft. 
30 ft. 
30 ft. 
28 ft. 
30 ft. 


5 in., 4 in., 3 in. 

6 in., 5 in., 4 in. 

6 in., 5 in., 4 in. 

7 in., 6 in., 5 in. 

8 in., 7 in., 6 in. 
8 in., 7 in., 6 in. 


350 lbs. to 515 lbs. 
475 lbs. to 725 lbs. 
510 lbs. to 775 lbs. 
600 lbs. to 1000 lbs. 
775 lbs. to 1260 lbs. 
825 lbs. to 1350 lbs. 



Cubic Contents of Wooden Poles, in feet. 



Length. 


Diameter. 


Section. 


Cubic Feet. 


27 ft. 


6 in. X 8 in. 


Circular 


7.36 


27 ft. 


7 in. x 9 in. 


Circular 


9.56 


27 ft. 


7 in. x 9 in. 


Octagonal 


10.1 


28 ft. 


7 in. x 9 in. 


Circular 


9.92 


28 ft. 


7 in. X 9 in. 


Octagonal 


10.46 


28 ft. 


8 in. x 10 in. 


Circular 


12.52 


28 ft. 


8 in. x 10 in. 


Octagonal 


13.2 


30 ft. 


7 in. x 9 in. 


Circular 


10.63 


30 ft. 


7 in. x 9 in. 


Octagonal 


11.21 


30 ft. 


8 in. X 10 in. 


Circular 


13.41 


30 ft. 


8 in. x 10 in. 


Octagonal 


14.15 


30 ft. 


9 in. X 12 in. 


Octagonal 


19.06 



Rake of Poles. 

Wooden poles should be given a rake of 9 to 18 inches away from the 
street. Iron or steel poles set in concrete need be given but 6 to 9 inches 
rake. Corner poles, and those supporting curves, should bo given additional 
rake or be securely guyed. 



634 



ELECTRIC RAILWAYS. 



AVERAGE WEIGHTS OF VARIOUS WOODS, IN 

POMDS. 



Kind. 



Live oak 

White oak .... 

Red oak 

Chestnut 

Southern yellow pine 
Northern yellow pine 
Long-leaf yellow pine 
Norway pine . . . 

Spruce 

Hemlock 



Condition. 


Weight per 
Cubic Foot. 


Perfectly dry 


59 


Perfectly dry 


48 


Perfectly dry 


35 


Perfectly dry 


41 


Perfectly drv 


45 


Perfectly dry 


34 


Unseasoned 


65 


Perfectly dry 


46 


Perfectly dry 


25 


Perfectly dry 


25 



The weight of green woods may be from one-iifth to one-half greater than 
the weight when perfectly dry. 



RIP 



WIRE. 



(Merrill.) 

The following tables give the dip of the span wire in inches under the 
combined weight of span wire and trolley wire, for various spans and strains. 
Length of trollev wire between supports, 125 feet. Weight of trolley 
wire, 319 lbs. per 1000 feet. Weight of span wire, 210 lbs. per 1000 feet. 

Single Trolley W r ire. 



Spans in 


Strain on Poles, in Pounds. 


Feet. 


500 


800 


1000 


1500 


2000 


2500 


3000 


30 


7.8 


4.9 


3.9 


2.6 


1.9 






40 


10.6 


6.5 


5.3 


3.5 


2.7 






50 


13.6 


8.5 


6.8 


4.5 


3.4 


2.7 




60 


16.7 


10.4 


8.3 


5.6 


4.2 


3.3 


2.8 


70 


19.9 


12.4 


9.9 


6.6 


4.9 


4 


3.3 


80 


23.2 


14.5 


11.6 


7.7 


5.6 


4.6 


3.9 


90 


26.7 


16.7 


13.4 


8.9 


6.6 


5.3 


4.5 


100 


30.3 


18.9 


15.2 


10.1 


7.6 


6.1 


5.1 


110 


34 


21.3 


17 


11.3 


8.5 


6.8 


5.7 


120 


37.9 


23.7 


18.9 


12.6 


9.5 


7.6 


6.3 




Note. — See also chapter on Conductors. 
For table of stranded wire for spans and guys see page 200, Properties 
of Conductors. 



SIDE BRACKETS. 



635 



Span Wires should be stranded galvanized iron or steel, sizes i inch 
diameter T 6 S , £, or | inch according to the weight of trolley wire, etc., to be 
supported. Where wooden poles are used it is not necessary to provide 
other insulation for the span wire, and the wire can be secured to the loop 
of an eye-bolt that is long enough to pass through the pole at a point from 
twelve to eighteen inches below the top, and that has a long thread to allow 
taking up slack. Where metal poles are used it is necessary to insulate the 
span wire from the pole. This has been done in some cases by inserting a 
long wooden plug in the top of tubular poles, capping it with iron, the wooden 
plug then being provided with the regular eye-bolt. The most modern way 
is to provide a good anchor bolt or clasp on the pole, then insert between 
the span wire and this bolt one of the numerous forms of line or circuit- 
breaking insulators devised for the purpose. If the anchor bolt is not made 
for taking up slack, the insulating device can be so designed as to be used 
as a turnbuckle. Of course insulation must be provided for both ends of 
the span wire. 

Span wire must be pulled taut when erected so that the sag under load will 
be a minimum. Height above rail surface should be at least 18 feet after 
the trolley wires are in place. This height is regulated by statute in some 
states, and runs all the way from 18 to 21 feet. 

Side Brackets. — Along country roads and in such places as the track 
is along the side of the roadway or street, it is customary to use single poles 
with side brackets to support the trolley wire. 

Where side brackets are used it is not safe to place the pole less than four 
feet away from the nearest rail, and to give flexibility to the stranded sup- 




Fig. 10. Single Suspension. 
For Wood Poles. 



porting wire, now always provided for the trolley wire, the bracket should 
be long enough to reach the distant rail, thus giving a little more than two 
feet of cable for flexibility. A common length of bracket is 9 feet. 

Figures 10 and 12 show the simple form of side bracket in most general 
use, and Figs. 11 and 13 show variations of the same. It is obvious that this 
method of support may be made as elaborate and ornamental as may be 
desired. 

On double-track roads center-pole construction is sometimes used, in which 
poles are placed along the center line between the two tracks, and brackets 
are erected on each side of the poles overhanging the tracks. Where wooden 
poles are used a good form of construction is to bore the pole at the proper 
height and run through it the tube for the arms, this long tube being properly 
stayed on both sides of the pole by irons from the pole-top to the bracket 
ends, or by braces against the pole. The trolley supporting wire can extend 
from end to end of the brackets through the pole, or can be cut at the 
pole, aed eye-bolts be used, as in the tide-bracket construction shown by 



636 



ELECTRIC RAILWAYS. 




Fig. 11. Single Suspension. 
For Wood Poles. 




Fig. 12. Single Suspension. 
For Iron Poles. 




Fig. 13. Single Suspension. 
For Iron Poles. 



TROLLEY WIRE SUSPENSION. 637 

Figures 14 and 15 illustrate simple forms of center-pole brackets. 




Fig. 14. Double Suspension. For Wood Poles. 



Center-pole construction is quite often used on boulevards in cities, where 
the brackets and poles can be made quite ornamental. 




Fio. 15. Double Suspension. For Iron Poles. 



TROLLEY W'IRl! SUSMJWlSIO^. 



The support of the trolley wire along straight lines is 
a simple matter and needs no explanation; at curves 
and ends there have been some simple forms developed 
in practice that are handy to have at hand. Following 
are some of the points: 

Terminal anchorage. — Single track. See 
Fig. 16. 

Line anchorag-e. — See Figs. 17 and 18. To be 
placed at the foot of all grades, at the top of hills, 
and at tangents, three (3) per mile is good practice; 
where curves are frequent they will afford all the 
anchorage necessary. 




Fig. 16. 




~ 



Fig. 17. Single Track. 



Fig. 18. Double Track, 



638 



ELECTRIC RAILWAYS. 



Turnout and Siding* Suspension. — Following is a sketch of a 
very simple arrangement of suspension and guys for a single-track turnout. 




Fig. 19. 



Curves, Suspension, and Guys.— The suspension of the trolley wire 
at curves is complicated or simple, according as the track may be single or 
double, or the curve may be at a crossing or a simple curve. Below are 
sketches of several types of suspension for different forms of curves, for 
single and double track, for cross suspension, and for center-pole construc- 
tion. 





Fig. 20. Simple Right-angle 
Curve, Single Track. 



Fig. 21. Single Track, Obtuse Angle. 





Fig. 22. Double Track, Right-angle 
Turn, Cross Suspension. 



FlG. 23. Double Track, Right- 
angle Turn, Center Pole. 



TROLLEY WIRE SUSPENSION. 



639 





Fig. 24. Single Track Crossing, 
Cross Suspension. 



Fig. 25. Single Track Crossing, 
Cross Suspension. 



Crossing's, Suspension, and Guys. — Simple crossings of tracks 
make no complication in the suspension of the trolley wires. When curves 
are added to connect one track with the other, complications begin, and 
where double tracks cross double tracks, and each is connected to the other 
by curves each way, the network of trolley wires becomes very complicated. 
Above are sketches of a couple of simple crossings which will clearly 
enough illustrate the methods of suspension commonly used. 





CROSS SUSPENSION WITH GUARDS 
FOR TROLLEY WIRE. 



Fig. 2a 



Guard Wires. 

Where trolley wires are used in cities or in any location where there are 
other overhead conductors liable to fall across the trolley wire, it is custom- 
ary to place guard wires parallel with but above the trolley wire, as shown 
in the above sketch. A piece of No. 6 B. & S. galvanized iron or steel 



640 



ELECTRIC RAILWAYS. 



wire is drawn taut above the regular suspension wire ; porcelain insulators 
are secured to the same at a point about a foot or 18 inches either side of the 
trolley wire, and through these insulators is threaded and tied a No. 10 gal- 
vanized iron wire. This guard should be broken at least every half-mile 
where it is in any great length, as it is not advisable to have it a continuous 
conductor for any great distance, and it is advisable to avoid its use where- 
ever possible. 



CJLTE1VARY TROLLEY CONSTRUCTION FOR 

ALTERHrATI^G CURREII RAILWAYS. 

Abstract of G. E. Co. Bulletin, Nov., 1907. 

The radical departure in the design of trolley line construction made 
necessary by the advent of high tension alternating current distribution 
for electric railway operation has resulted in the catenary system of line 
construction, which while providing ample insulation surface for the high- 



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.02 .04 .06 .06 -/O J2 J4 J6 

T/>r?e Seconds 



Fig. 27. 



est potentials used or contemplated, also incidentally affords marked me- 
chanical improvement which is important with the high speeds of modern 
suburban and interurban operation, and steam railroad electrification. 

The catenary system which is equally applicable to bracket or cross span 
construction, consists essentially of an arrangement of a slack messenger 



CATENARY TROLLEY CONSTRUCTION. 



641 



cable and suitable hangers so distributed as to maintain the trolley wire 
practically without sag between suspension points, or to limit the sag as 
may be necessary for various conditions of operation. 

The blow of a collector passing suspension points at high speed is thus 
greatly reduced. The shorter distance between hangers necessitates less 
stress in the trolley wire and reduces danger of break in the line. 

The catenary system, therefore, offers the mechanical advantages of a 
longer pole spacing and a natter trolley wire, and a flexibility in the line 
which obviates the hammer blow of the collector at suspension points, and 
reduces danger of mechanical breakage. 

The three-point suspension in which, with 150 ft. pole spacing, the 




5 re 9 to 
jD$f/ec6/o/7 /r?c/7e<s 



Fig. 28. 



hangers are 50 ft. apart, has been found ample to maintain a sufficiently 
level trolley wire for operation with wheel collector at speeds up to sixty- 
five miles per hour. A new element is, however, introduced by the sliding 
pantograph or bow trolley which, on account of its great inertia, requires 
a closer spacing of the trolley support. 

Fig. 27 shows comparative curves of time required for vertical vibration 
of wheel and pantograph trolley respectively. It has been found that an 
eleven-pomt suspension renders the trolley wire sufficiently level for the 
relatively sluggish action of the pantograph collector. This brings the 
hangers 13.6 feet apart, and for all operative conditions with sliding collec- 
tors the eleven-point suspension is recommended. 

Fig. 28 shows the effect of temperature variation on sag and stress in 
troller- wire with the three-point construction. 



642 



ELECTRIC RAILWAYS. 



Steel Strand. 

Common galvanized strand is not recommended for any purpose in cate 
nary construction, and wherever steel strand is used it should be one of tlu 
three special grades, properties of which are given in the following table. 



Physical Properties of Seven IFire Extra Gralvanized 
Steel Strand. 



Extra Galvanized Siemens-Martin Strand 90,000 per Sq. In. 

Elongation. Lay. 



I" 



Tensile 


Elastic 


Strength. 


Limit. 


30601b. 


1830 lb. 


4860 " 


2910 " 


6800 " 


4080 " 


9000 " 


5300 " 


11000 " 


6600 " 


19000 " 


11400 " 



6-9% 
6-9% 
5-8% 
5-8% 
5-8% 
4-6% 



3" 

3£" 

4" 

W 

4£" 

5" 



Extra Galvanized High Strength (Crucible) Steel Strand. 
Diameter. tensile Elastic Elongation . Lay . 



i" 

A" 

I" 

f 

t" 



5100 lb. 

8100 " 
11500 " 
15000 " 
18000 " 
25000 " 



3315 lb. 
5265 " 
7475 " 
9500 " 
11700 " 
16250 " 



3-5% 
3-5% 
3-5% 
3-5% 
3-5% 
2-4% 



31" 
4 // 

4£" 

5" 

5" 

w 



Extra Galvanized Extra High Strength (Plow) Steel Strand. 
Diameter. ct™°"fv» Elongation. Lay. 



i" 



Tensile 


Elastic 


Strength. 


Limit. 


7600 lb. 


5700 lb. 


12100 " 


9075 " 


17250 " 


12930 " 


22500 " 


16800 " 


27000 " 


20250 " 


42000 " 


31500 " 



2H% 
2M% 

2M% 



4" 

4J" 

5" 

5}" 

5j" 

6" 



For ordinary conditions, the messenger cable should be of &' extra gal- 
vanized Siemens-Martin steel. For pull-offs \" cable is satisfactory, and 
for general guying purposes \" extra galvanized Siemens-Martin strand is 
generally recommended. Special conditions may call for " high strength" 
cable, but as this cable requires mechanical fastenings on account of its 
stiffness, it should be used only where absolutely necessary. 



CATENARY CONSTRUCTION. 



643 



Ijine Material per Mile of Tangent Track for Catenary 
Construction. 



messenger 



Span wire 
hangers 

Strain insulators 

Brackets 

Insulator pins 

Messenger insulators . . . 

4" hangers 

12f " hangers 

4" hangers 

4f " hangers 

6j" hangers 

9" hangers 

12£" hangers 

17£" hangers 

Splicing sleeves 

Anchor hangers . 

Anchor eyes 

Anchor turnbuckles 

Anchor clamps 

Material for curves, 
crossings, etc., depen- 
dent upon local con- 
ditions : 

Strain insulators 

Steady braces 

Steady brace ears 

Spreaders 

12" pull-off hangers 

15" pull-off hangers .... 

18" pull-off hangers 

Anchor hangers 

Feeder ears 

Anchor eyes 

Anchor clamps 

Anchor turnbuckles 

Section insulators 

Strain insulators 

Frogs 

Crossings 

Line Material : 

3-bolt cable clamp 

Eye-bolts 

Anchor rods 

Feet of grooved trolley 
wire 

Feet of messenger strand 

Feet of anchor strand . . 

Feet of cross span and 
pole guy strand 

Feet of pull strand 



Single Track. 



Bracket 
Construc- 
tion. 



3 
Point 



5300 
5400 
1400 



11 
Point 



36 

72 

72 

72 

72 

72 

3 

4 

2 

4 



5300 
5400 
1400 



Cross Span 
Construc- 
tion. 



3 

Point 



36 


36 


80 


80 


"'36' 




68 






36 




72 




72 




72 




72 




72 


3 


3 


4 


4 



88 
88 

72 

5300 
5400 
2600 

3200 



11 

Point 



88 
88 

72 

5300 
5400 
2600 

3200 



Double Track. 



Center Pole 
Construc- 
tion. 



Point 



8 


8 


72 


72 


72 


72 


72 


72 


72 




136 






72 




144 




144 




144 




144 




144 


6 


6 


8 


8 


4 


4 


4 


4 



72 

10600 
10800 
2600 

3200 



11 

Point 



10600 
10800 
2600 

3200 



Cross Span 
Construc- 
tion! 



3 

Point 



72 
136 



88 

88 
72 

10600 
10800 
2600 

3200 



11 
Point 



72 



72 
144 
144 
144 
144 
144 



88 
88 
72 

10600 
10800 
2600 

3200 



644 



ELECTRIC RAILWAYS. 



Stag-g-ering* Trolley for Sliding- Contact* 

Where a sliding collector is to be used, it is recommended that the tan- 
gent line be staggered by means of steady braces in bracket construction, 
or pull-off, in span construction, to avoid wearing grooves in the collector 
contact surface. 

For this purpose the trolley wire should be displaced approximately eight 
inches on each side of the center line of the track every 1000 ft., i.e., there 
should be one complete wave from the extreme position on one side across 
the track and back to the extreme position on the same side in each 2000 ft. 
of line. 

When the road bed is new, it is well to simply make provisions for stag- 
gering the trolley wire, but to defer actual staggering until the road bed is 
settled and put in final shape, as the sway of the car due to irregularities in 
the track may be great enough to throw the sliding contact entirely off the 
wire. 

Bracket Construction. 

After the poles are installed the brackets should be located at a height 
of sixteen inches more than the required distance between the top of the 
rail and the trolley wire. This allows for two inch sag of the bracket due 
to the yielding of the pole when loaded, in single track construction. For 
double construction this distance should be fourteen inches greater than 
the desired height of trolley above top of rail. The messenger wire should 
next be adjusted for tension to give a sag at the center of span of about 9 
inches at 30° F., 10 inches at 60° F., and 11 inches at 85° F. 



Span Construction. 

In span construction the span wire should be installed so that when the 
weight of the messenger and trolley is put on it, there will be a sag of at 
least three or four feet between a straight line drawn through the points of 
support of the span wire and the point on the span wire where the mes- 
senger hanger is attached. When unusually long distances are necessary 
between the poles the sag should be greater. The back guys should be 
insulated for full line potential. 




Fig. 29. Catenary Construction. Single Track Bracket. 



CATENARY CONSTRUCTION. 



645 




Fig. 30. Catenary Construction. Double Track Span. 




Fig. 31. Catenary Curve Construction Using Steady Brace. 

ft 




Fig. 32. Spreader Curve Construction. 



646 



ELECTRIC RAILWAYS. 




Fig. 33. Catenary Construction. Street Corner. 



Number and Xieng-th of Hangrers Required per Span for 
Tangent Track. 

Eleven-Point Construction. 



Length Pole 
Spacing. 


Points. 


4" 


4f" 


6£" 


9'' 


10' 


Uif 


12f" 


14" 


15£" 


17J" 

2 

2 

3 


18£" 


Number of hang- 
ers required. 




150 ft. 


11 
9 
8 
7 
6 
5 
4 


1 


2 


2 


2 

1 


'2" 


'2" 
2 


2 
'2" 




125 " 


2 
*3*' 


'2" 

2 
2 




110 " 








? 


95 " 












91 


80 " 
















2 


70 " 


















2 


55 " 




















4 



























Three- Point Construction. 



150 ft. 


3 
3 
3 
3 
3 
2 
2 


1 












2 










125 " 






1 








2 
2 

i" 


*2" 
2 




110 " 










1 




.... 




95 " 














80 " 


















70 M 





















55 " 


















































CATENARY CONSTRUCTION. 



647 



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648 



ELECTRIC RAILWAYS. 



"Where three or more tracks are equipped as on the New York, New 
Haven & Hartford Railroad, the trolley wire is generally supported from 
two catenary cables, which are carried on steel bridges, placed 300 feet 
apart. Heavier bridges are used at intervals to anchor the system, and 
views of one of these anchor bridges are shown in Figs. 34, 35, and 36." 




BRIDGE SUPPORT FOR TROLLEY. 



649 




r 



Fig. 35. End View of Bridge for Supporting Catenary Hung Trolley, 
N.Y..N.H. &H.R.R. 



050 



ELECTRIC RAILWAYS. 



9UJ7 A\n?!|ixrtV' « « 




Fig. 36. Plan View of Bridge for Supporting Catenary Hung Trolley, 
NY., N.H. &H. R.R. 



CATENARY CONSTRUCTION. 



651 




Fig. 37. Detail of Catenary Construction, Spendersfelds Line 




Fig. 38. T-Iron Bracket with Main Insulator and Steady Strain. 



The future development of the A. C. motor is in no way handicapped by 
the ability of the trolley construction to withstand high potential, as A. C. 
trolleys have been worked successfully at 10,000 volts and 15,000 volts. 



652 



ELECTRIC RAILWAYS. 



E\ERG1 COHSIJMPTIOI. 

Power Curves. — For convenience in quickly ascertaining the horse- 
power required to propel a car of known weight under known conditions of 
speed and grade, the curves shown below have been calculated. 

The left-hand portion of the lower horizontal line represents the speed in 
miles per hour; the right-hand portion of same line, the h.p. per car; the 
oblique lines in left-hand side of cut, the per cent grade as marked on each 
line; the oblique lines on right-hand side of cut, the weight of car as marked; 
while the vertical line in center of cut represents the h.p. per ton. This 
curve is based upon a flat friction rate of 20 lbs. per ton (2000 lbs.) for all 
speeds and weight of cars, and is approximate only. 





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Fig. 39. 



HORSE-POWER OF TRACTIOX. 



653 



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Wn , 



H. p. — -^_ (ir+2000 sin 0). W 
37o 



Load in tons. n = Speed in miles per hour, 
= Wn X .0026| (K + 2000 sin 0). K— Resistance in lbs. per ton. K'—^q 

Hz= Constants of power required to move ONE ton on level at speeds in 

table with K— 10. 
E'— Constants of additional power required to raise one ton on 

grader and at speeds given. 
Hx WK f — T&. P. required on levels alone for speeds given. 
i? 7 X JF = H. P. additional on grades alone for speeds and % given. 
W(K'H± BO = total H. P. required. 

Example: Given a motor car, total weight 9 tons, to ascend a 7 per 
cent grade at a speed of six miles per hour. What is the estimated horse- 
power required, with K= 30 lbs. ? 



654 



ELECTRIC RAILWAYS. 



30 

H for 6 miles per hour is . 16, which, multiplied by 9 Xtq, = 4.32 h.p., in 

overcoming the track resistances alone. 

H' = 2.240, which, multiplied by 9, = 20.16. The sum of the two will 
give the total theoretical, i.e., 24.48 h.p. required. Allowing 50 per cent as 
the combined efficiency of motors and gearing, to operate this car would 
require a draft of 48.96 h. p. upon the line. 





HOR§£-POW£R OF TRACTIOI, 


(Davis.) 






c3 


Speed in Miles per Hour. 


T3 
c3 




o 


4 


6 


8 


10 


12 


15 


20 


25 


30 


35 


40 


50 


60 


3 






























% 


Horse-Power Required to Propel One Ton at Various Speeds up 


£ 


Various Grades. 





.32 


.48 


.64 


.80 


.96 


1.20 


1.60 


2.00 


2.40 


2.80 


3.20 


4.00 


4.80 


i 


.53 


.80 


1.07 


1.33 


1.60 


2.00 


2.66 


3.33 


4.00 


4.66 








2 


.74 


1.12 


1.49 


1.87 


2.24 


2.80 


3.63 


4.66 


5.60 










3 


.93 


1.44 


1.92 


2.40 


2.88 


3.60 


4.80 


6.00 












4 


1.17 


1.76 


2.34 


2.93 


3.52 


4.40 


5.47 














5 


1.39 


2.08 


2.77 


3.46 


4.16 


5.20 
















6 


1.60 


2.40 


3.20 


4.00 


4.80 


















7 


1.86 


2.72 


3.62 


4.53 




















8 


2.02 


3.04 


4.05 






















9 


2.24 


3.36 


4.48 






















10 


2.47 


3.68 


4.90 






















11 


2.67 


4.00 
























12 


2.88 


4.32 
























13 


3.09 


























14 


3.29 


























15 


3.52 



























Note No. 1. — The h.p. required to propel a car equals the total weight 
of car plus its load (in tons) multiplied by the h.p. in table corresponding to 
assumed grade and speed. 

STRKKI RAILWAY, 
Tractive Force, 

F. E. Idell, M. E. 

On Good Track. - To start car 116 lbs. per ton. 

To keep in motion at 6 miles per hr. 15.6 lbs. per ton. 
On Bad Track. — To start car 135 lbs. per ton. 

To keep in motion 32 lbs. per ton. 

On Curves. — To start car from to 6 miles per hour . 284 lbs. per ton. 

average, 264 feet per minute. 



TRACTION. 



655 



TRACTION. 

(Davis.) 







Load of Trailer Cars in Tons which a Motor 


Per cent 
Grade. 


Tractive Force 
in Pounds 
per Ton. 


Car of one Ton will Haul. 












Snowy Kail. 


Wet Rail. 


Dry Rail. 





30 


8.50 


12.33 


16.00 


1 


50 


4.70 


7.00 


9.00 


2 


70 


3.07 


4.21 


6.14 


3 


90 


2.17 


3.44 


4.55 


4 


110 


1.60 


2.63 


3.54 


5 


130 


1.19 


2.07 


2.84 


6 


150 


0.90 


1.66 


2.33 


7 


170 


0.70 


1.35 


2.00 


8 


190 


0.50 


1.10 


1.63 


9 


210 


0.35 


0.90 


1.38 


10 


230 


0.24 


0.74 


1.17 


11 


250 


0.14 


0.60 


1.00 


12 


270 


0.05 


0.48 


0.85 


13 


290 


Wheels slip. 


0.38 


0.77 


14 


310 




0.30 


0.61 


15 


330 










0.21 


0.51 


16 


350 










0.14 


0.43 


17 


370 










0.08 


0.35 


18 


390 










0.02 


0.28 


19 


410 










Wheels slip. 


0.22 


20 


430 












0.16 


21 


450 












0.11 


22 


470 












0.06 


23 


490 












Wheels slip. 



Note No. 1 . — Multiply figures in table by weight of motor car (in tons) 
to get weight of trailer (in tons) that said motor car will haul up corre- 
sponding grades. 

HEVOLlIIO\S PER ]HII¥UTE OF YARIOVi §IZED 
WHEEL! TO MAKE VARIOUS SPEERS. 





Miles per Hour. 


Diameter 


2 


4 


6 


8 


10 


15 


20 


25 


30 


40 


of 

Wheel. 






















Feet per Minute. 




176 


352 


528 


704 


880 


1320 


1760 


2200 


2640 


3520 


24 in. 


28 


56 


84 


112 


140 


210 


280 


350 


420 


560 


26 in. 


26 


52 


78 


103 


129 


194 


258 


323 


388 


517 


28 in. 


24 


48 


72 


96 


120 


180 


240 


300 


360 


480 


30 in. 


22 


45 


67 


90 


112 


168 


224 


280 


336 


448 


33 in. 


20 


41 


61 


82 


102 


153 


204 


255 


306 


408 


36 in. 


19 


37 


56 


75 


93 


140 


187 


234 


280 


374 


42 in. 


16 


32 


48 


64 


80 


120 


160 


200 


240 


320 



656 



ELECTRIC RAILWAYS. 



POWER KiailREI) FOR BOiBLE AND ftl'XGJLi: 

truck: cars. 

Wattmeter placed on car. (McCulloch.) 





DQ 

o 

tJO 
e3 
u 

<v 

< 


Average Watt-hours per 
Car-mile. 


o o 


4a 

<X> 

m 

u 
<v 

e3 

u 


a 
o 
H 

Pi 
©•■A 

+a ft 

«i 

Pi 


Average Watt-hours per 

Cai Mile per 1000 

Passengers. 


Double-truck car. Seats 
36 ; weight, 11.75, tons ; 
average for entire day 


12040 


1334 


9.03 


335 


1025 


5.9 


Same as above. Average 
for heaviest trip . . . 


13080 


1412 


9.25 


335 


1025 





pingle-truck car, no 
trailer. Seats 28; 
weight, 8 tons .... 


8471 


921 


9.20 


303 


1060 





Single-truck car. Trail- 
ers operated 26% of the 
time. Average for the 
entire day 


9400 


1110 


8.42 


254 


1088 


7.9 


Single-truck motor and 
open trailer. Seats, 
63; weight, 10.5 tons. 
Average for heaviest 
trip 


12680 


1440 


8.84 


201 


1208 


— 



TTeuio for Determination of Power Required for 
Operation of Street Railways, 



H.P. 



H.P. = 



Pounds torque X R.P.M. 
5252 

Pounds tractive effort X M.P.H. 
375 



Pounds j 
tractive ( 
effort 



Number gear teeth X 24 X gear efficiency X pounds torque 
Number pinion teeth X inches diameter of wheels. 

Miles ( _ Inch diameter of wheels X number pinion teeth X R.P.M . 
Per Hour. J ~~ 336 X number gear teeth 

Assumed — 3 miles per hour speed on curve, 4 ft. 8J in. gauge. 



KILOWATTS ON GRADES. 



657 



TRACTIVE E FJFOItT OX GRADES. 
Pounds per Ton for 15 Ton Car. 









Speed — Miles per Hour. 




Grade. 










Per Ct. 
























2 


4 


6 


8 


10 


12 


14 


16 


18 


20 





15.03 


15.11 


15.24 


15.42 


15.66 


15.95 


16.29 


16.69 


17.14 


17.64 


1 


35.03 


35.11 


35.24 


35.42 


35.66 


35.95 


36.29 


36.69 


37.14 


37.64 


n 


45.03 


45.11 


45.24 


45.42 


45.66 


45.95 


46.29 


46.69 


47.14 


47.64 


2 


55 03 


55.11 


55.24 


55.42 


55.66 


55.95 


56.29 


56.69 


57.14 


57.64 


2* 


65.03 


65.11 


65.24 


65.42 


65.66 


65.95 


66.26 


66.69 


67.14 


67.64 


3 


75.03 


75.11 


75.24 


75.42 


75.66 


75.95 


76.29 


76.69 


77.14 


77.64 


3* 


85.03 


85.11 


85.24 


85.42 


85.66 


85.95 


86.29 


86.69 


87.14 


87.64 


4 


95.03 


95.11 


95.24 


95.42 


95.66 


95.95 


96.29 


96.69 


97.14 


97.64 


5 


115.03 


115.11 


115.24 


115.42 


115.66 


115.95 


116.29 


116.69 


117.14 


117.64 


6 


135.03 


135.11 


135.24 


135.42 


135.66 


135.95 


136.29 


136.69 


137.14 


137.64 


7 


155.03 


155.11 


155.24 


155.42 


155.66 


155.95 


156.29 


156.69 


157.14 


157.64 


8 


175.02 


175.11 


175.24 


175.42 


175.66 


175.95 


176.29 


176.69 


177.14 


177.64 


9 


195.03 


195.11 


195.24 


195.42 


195.66 


195.95 


196.29 


196.69 


197.14 


197.64 


10 


215.03 


215.11 


215.24 


215.42 


215.66 


215.95 


216.29 


216.69 


217.14 


217.64 



KILOWATTS OX GRADES. 
15 Ton Oar. Energy measured Input to Car. 



Grade 








Speed — Miles pei 


Hour. 








Per 

Cent. 








2 


4 


6 


8 


10 


12 


14 


16 


18 


20 





1.09 


2.19 


3.31 


4.45 


5.67 


6.92 


8.25 


9.65 


11.15 


12.75 


1 


2.54 


5.07 


7.65 


10.25 


12.90 


15.60 


18.35 


21.20 


24.10 


27.20 


H 


3.26 


6.52 


9.80 


13.15 


16.50 


19.90 


23.42 


27.00 


30.62 


34.40 


2 


3.98 


7.96 


12.00 


16.09 


20.10 


24.22 


28.50 


32.80 


37.20 


41.70 


2* 


4.71 


9.41 


14.15 


18.90 


23.70 


28.60 


33.60 


38.50 


43.70 


48.90 


3 


5.43 


10.85 


16.30 


21.80 


27.30 


32.90 


38.60 


44.30 


50.20 


56.20 


3* 


6.15 


12.30 


18.50 


24.70 


30.90 


37.22 


43.70 


50.10 


56.70 


63.30 


4 


6.87 


13.75 


20.70 


27.60 


34.60 


41.60 


48.70 


55.80 


63.20 


70.60 


5 


8.32 


16.65 


25.00 


33.40 


41.80 


50.30 


58.90 


67.40 


76.20 


85.00 


6 


9.77 


19.60 


29.40 


39.20 


49.10 


58.90 


69.10 


78.00 


89.30 


99.40 


7 


11.20 


21.48 


33.80 


45.00 


56.30 


67.60 


79.20 


90.50 


102.50 


114.00 


8 


12.65 


25.30 


38.10 


50.80 


63.50 


76.30 


89.30 


102.20 


115.30 


128.50 


9 


14.10 


28.30 


42.50 


56.50 


70.70 


85.00 


99.40 


113.80 


128.50 


143.00 


10 


15.56 


31.10 


46.70 


62.10 


78.30 


95.10 


109.80 


125.8 


141.50 


157.20 



The above table is based upon an average efficiency of 83 per cent for the 
motor equipment. This efficiency is assumed flat for all loads, hence giving 
values slightly high for the low kilowatt car inputs and slightly low for the 
heavier inputs. 



658 



ELECTRIC RAILWAYS. 



Power Consumption. Schedule Speed 25 UI.P.H. 
35 Ton Car. 



Stops per Mile. 


Kilowatts. 


Maximum Speed. 


Total Motor Capacity. 





29 


25 m.p.h. 


143 


.2 


35 


29 


175 


.4 


44 


31 


186 


.6 


51 


33 


207 


.8 


63 


37 


245 


1.0 


79 


43 


301 


1.2 


100 


51 


395 



The energy values given in above table represent input to the car not 
including any line losses. The maximum speed values represent maximum 
speed reached during the run. Motor capacity is based upon a temperature 
rise of 60° C, above surrounding air, taken at 25° C, after a full days' run 
at the schedule of 25 miles per hour noted. 

Possible Schedule with 45 HE.P.H. Maximum Speed with 
Varying* .Frequency of Stops. 35 Ton Car. 



Schedule Speed. 


Kw. Input. 


45 


106 


40 


101 


35 


97 


30 


93 


25 


87.5 


20 


84. 



Number Stops per Mile. 










.18 




.40 




.70 


1 


.08 


1 


.80 



WO. 



OF CARS OW TEUT MILES OF TRACK, VARI- 
OUS §PEED§ AXR HEADWAYS. 



Minutes 
Apart 






Average Speed in Miles per Hour. 






or 




















ITdway. 


6 


7 


8 


9 


10 


12 


15 


20 


25 


30 


1 


100 


8Q 


75 


67 


60 


50 


40 


30 


24 


20 


2 


50 


44 


38 


33 


30 


25 


20 


15 


12 


10 


3 


33 


29 


25 


22 


20 


17 


13 


10 


8 


7 


1 


25 


22 


19 


14 


15 


13 


10 


8 


6 


5 


5 


20 


17 


15 


13 


12 


10 


8 


6 


5 


4 


6 


17 


14 


13 


11 


10 


8 


7 


5 


4 


3 


7 


14 


12 


11 


10 


9 


7 


6 


4 


3 


3 


8 


13 


11 


9 


8 


8 


6 


5 


4 


3 


3 


10 


10 


9 


8 


7 


6 


5 


4 


3 


2 


2 


15 


7 


6 


5 


4 


4 


3 


3 


2 


2 


1 


20 


5 


4 


4 


3 


3 


3 


2 


2 


1 


1 


30 


3 


3 


3 


2 


2 


2 


1 


1 


1 


1 



Note. — Fractions above one-half are considered whole numbers, and 
fractions below one-half are neglected. 



VARIOUS SPEEDS. 



659 



To obtain the number of cars required to operate any length road, divide 
the number found in the table under the desired average speed and head- 
way by ten, and multiply by the length of the road in question. Should it 



PRESSURE IN POUND PER SQUARE FOOT OF CR0S8 SECTION* 




£J £ 2 £ 



Fig. 4a 



1 Effect of Shape of Moving Body on Air Resistance," Crosby's 
Experiments. 



be desired to run at different average speeds on various portions of the road, 
treat each portion as a separate road, and add the results together. To the 
number of cars thus obtained should be added 20 per cent for reserve for 
roads under 20 cars. For roads over 20 cars, 10 per cent reserve will be 
enough 



660 



ELECTRIC RAILWAYS. 



Formula: — 

Let n = number of cars required. 
m = miles of track. 
S = average speeds in miles per hour. 
/ = interval or headway in minutes. 



Then, 



m X 60 

S X I ' 



HEADWAY, IPEED, AYI) TOTAL YHIBER OE 

CARS. 

Total number of cars on a given length of street on which cars are running 
both ways = (length of street X 120) -7- (headway in minutes X speed in 
miles per hour). 



IIIXES PER HOUR Il¥ FEET PER MIRUTE 
AND PER SECOND. 



(Merrill.) 



Miles 


Feet 


Feet 


Miles 


Feet 


Feet 


per 


per 


per 


per 


per 


per 


Hour. 


Minute. 


Second. 


Hour. 


Minute. 


Second. 


1 


88 


1.46 


16 


1408 


23.47 


2 


176 


2.94 


17 


1496 


24.93 


3 


264 


4.4 


18 


1584 


26.4 


4 


352 


5.87 


19 


1672 


27.86 


5 


440 


7.33 


20 


1760 


29.33 


6 


548 


8.8 


21 


1848 


30.8 


7 


616 


10.26 


22 


1936 


32.26 


8 


704 


11.73 


23 


2024 


33 . 72 


9 


792 


13.2 


24 


2112 


35.2 


10 


880 


14.67 


25 


2200 


36.67 


11 


968 


16.13 


26 


2288 


38.14 


12 


1056 


17.6 


27 


2376 


39.6 


13 


1144 


19.07 


28 


2464 


41.04 


14 


1232 


20.52 


29 


2552 


42.50 


15 


1320 


22 


30 


2640 


44 



RATING STREET-RAILWAY MOTORS. 661 

RATING §TREET.RAIIWA¥ MOTORS. 

(Condensed from W. B. Potter in Street Railway Journal.) 

Rise of temperature after one hour's run under rated full load not to ex- 
ceed 75° C. ; room being assumed at 25° C. Average load for a day's run 
should not exceed 30 per cent of its rated full load, which will give a rise of 
temperature of about 60° C. 

The above ratings are based on a line potential of 500 volts, but the aver- 
age performance can generally be increased in proportion to the increase in 
line voltage ; that is, a motor will do approximately 10 per cent heavier 
service for the same temperature rise when operated at 550 volts. 

With electric brakes, motors must have increased capacity, as heating 
increases 20 to 25 per cent. The 20 per cent increase is on roads having few 
grades and stops, while the 25 per cent is on hilly roads with frequent stops. 

Approximate rated horse-power of motors = 

(total weight of car in tons) x (max. speed in miles per hour on level). 

_ 

For equipments with electric brakes, divide by 4 instead of 5. When 
maximum speed is not known, it may be assumed as twice the schedule 



Example 1: 

20 ton car (loaded) x 50 m. p. h. ___ , . _. , T 
* J *- = 200 h. p., or four 50 h. p. motors. In 

this case, if the line pressure were raised to 600 volts, electric brakes could 
be used on the equipment by changing the gear ratio so as to have the same 
maximum speed. 

Example 2 : 

11 ton car (loaded) x 25 ra. p. h. pp , _. _ , 

2 , — = 55 h. p., or two 30 h. p. motors, 

5 

These rules indicate minimum capacity under ordinary conditions. 

Tractive Effort, 

Tractive effort is dependent on the rate of acceleration, grade, car fric- 
tion, and air resistance, which latter is ordinarily included in friction. 
Acceleration is expressed in miles an hour per sec. 1 mile per hour per sec. 
= 1.466 feet per sec. Excluding car friction, a tractive effort of 92A lbs. per 
ton (2000) will produce an acceleration of 1 mile per hour per sec. on a level 
track, and the rate of acceleration will vary in direct proportion to the 
amount of tractive erfort. On ordinary street cars, tractive effort during 
acceleration often rises to 200 or 300 lbs. per ton. 

On elevated or suburban roads the maximum tractive effort is generally 
100 to 150 lbs. per ton. For heavy freight work with slow speeds, the trac- 
tive effort seldom exceeds 30 to 40 lbs. per ton. 

Grades are commonly expressed in percentage of feet rise in 100 feet of 
distance, and tractive effort for a grade is the same percentage of the 
weight to be drawn as the rise is of the length of 100 feet. For instance, 
the tractive effort for a weight of one ton (2000 lbs.) up a grade of 3 per 
cent would be 3 per cent of 2000 lbs., or 60 lbs. For the total tractive effort 
there must be added to this, the effort for overcoming the car, wind, and 
rolling friction on a level. 

Average tractive efforts from numerous tests are shown in the following 
table : 

Tractive effort in 
lbs. per ton. 

15 ton car, up to 25 m. p. h 25 

" *« " " " 50 " " " 50 

25 " " " «' 25 " *« " 20 

" " " " " 50 " " " 25 

100 " train " " 25 " " " 15 

Heaw freight train, ud to 25 m. p. h. - , , , . , o to K0. 

J.D.Q above rates have to be increased ror snow and ice on the track. 



662 ELECTRIC RAILWAYS. 



Tractive Coefficient. 

This coefficient is usually expressed as the ratio between the weight on 
the driving-wheels and the tractive effort, and varies largely with the con- 
dition of the rails. 

In train work, the weight on drivers should be six times the tractive 
effort. 

Example: — Required the weight of a locomotive to draw a 100-ton 
train up a 2 per cent grade. 
For train. 

100 tons X 15 lbs. for friction = 1500 lbs. 
" " x 40 " " grade = 4000 " 

5500 lbs. 
Assume a 20-ton locomotive. 

20 tons x 15 lbs. for friction == 300 lbs. 
20 " X 40 " " grade = 800 H 

Total tractive effort, 6600 lbs. 

6600 lbs. equals 16.5 per cent of 20 tons, or a tractive coefficient of 16.5 per 
cent. Starting the train on a 2 per cent grade with acceleration of i m. p. h. 

91.1 
per sec. would mean additional tractive effort equivalent to — ^— =30.4 lbs. 

per ton. 

This would add to the requirements as follows : 

Train 100 tons, for friction and grade as above . . . 5500 lbs. 
44 44 " at 30.4 lbs. for acceleration 3040 44 

Total for train 8540 lbs. 

Assume 35-ton locomotive with motors on all axles. 

35 tons at 15 lbs. for friction 525 lbs. 

44 ' 4 il 40 " " grade 1400 44 

44 44 44 30. 4 for acceleration 1064 44 

Total tractive effort . . . 11529 lbs. 

or a tractive coefficient of 16.5 per cent for the 35-ton locomotive. 
Tests show the following tractive coefficients : 

Sanded 
per cent. per cent. 

Dry rail 28 30 

Thoroughly wet rail 20 25 

Greasy moist rail . 15 25 

With ice and snow on the track, the coefficient is lower, and the rolling- 
friction higher. 

Average energy. — Approximate capacity of a power station may be 
assumed as about 100 watt-hours per ton mile of schedule speed for ordinary 
conditions of city and suburban service. 

Example : — 15-ton car, 12 miles per hour schedule, 

k.w. at stations 100 x 15 X 12 = 18 k.w. 
If stops are a mile or more apart, only 60 to 70 watt-hours may be neces- 
sary. 
Frequent stops and high schedule speeds take 120 or more watt-hours. 



TRAIN PERFORMANCE DIAGRAMS. 663 

The following table of efficiencies will be found convenient in estimating 
the power required for operation of motor cars, using three-phase trans- 
mission and direct current motors. The efficiencies would vary somewhat 
with the load factor, but can be taken as generally applicable. 

Considering the I.H.P. of the engine as a basis, for the 

Average efficiency of engine 90 per cent. 

44 44 " generator 94 " 44 

44 44 44 high potential lines .... 95 " 44 

44 44 44 substations 90 " 44 

44 44 " direct current lines .... 92 44 44 

44 44 44 motors, including losses of 

control 72 44 44 

Combined efficiency of the motors and series parallel 
control during period of cutting out the controller 

may be taken as 63 44 44 

Efficiency of motors after cutting out the controller, 
depending on size of motors 80 to 86 per cent. 

THAIBT PERFORHAWCE DIACHAMS. 

In order to accurately ascertain the power required to operate a given 
railway system it is necessary to analyze the performance of its trains or 
other units of transportation. This is best done by constructing train per- 
formance diagrams. Such diagrams may be constructed for a desired 
schedule and other data, in order to determine the size and type of motor 
best adapted to the purpose; or they may be made up from the characteristic 
curves of a given motor, to determine if that particular motor will fit the 
case in point, or just what will be the result from its use. Such diagrams 
are also useful in predetermining the heating effect upon the motors. 

The diagram ordinarily includes: 

Speed- time curve. 
Distance-time curve. 
Current curve. 
Voltage curve and 
Power or kilowatt curve. 

While it is possible to construct a performance diagram for a given line 
of road, this diagram must be based upon the characteristics of some known 
motor, and it is necessary therefore that the schedule be stated, and 
requirements as to heating and economy be given and that motors to pro- 
duce these results be designed by makers of such apparatus — or that motors 
from their standard designs be selected, which come nearest to fitting the 
requirements of the case; and in determining this fitness, performance dia- 
grams can be constructed from the known characteristics of the motor 
selected. 

In stating the conditions it is obvious that profile and contour maps of 
the road must be had in order to determine the effect of grades and curves. 

In describing the method of laying out these curves, the first case given 
will be based upon a straight and level track and the simplest possible con- 
ditions, and a second example will be shown which includes grades and 
curves. 

Figure 42 is a diagram of train performance, which shows the speed-time 
curve, distance-time curve, and the current curve, as well as the schedule 
required, and the distance between stops. This diagram is simply typical, 
to indicate methods. 

Figure 41 is a typical Railway Motor characteristic, and for simplicity 
shows but two curves, that of tractive-effort and of speed, the speed being 
given in miles per hour and the tractive-effort in pounds draw-bar pull for 
33-inch wheels and gear ratio 3.09. The ampere consumption at the 
different rates of speed is also given. Unless armature revolutions instead 
of speed in miles per hour be used, it always will be necessary to state the 
diameter of wheel and the gear ratio. 



664 



ELECTRIC RAILWAYS. 































































a 




























































A. 




























































fej 


























































« 












| 








TYTIUAL 
RAILWAY MOTOR 
CHARACTERISTIC 

33*WHEELS 
PINION 23, GEARS 71, 
RATIO 3.09 






















W 


12 










\ 




























.S? 










\ 




























n 












\ 




























3800 
3600 


3C 
34 
32 
30 
88 












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\ 




































\ 


































V 




































































3000 
2800 










































^ 


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A 


& 




































\ 


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2400 






















\ 


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20 


























































2000 










































Of, 


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■2*1 
















14 
12 


























































1400 
1200 


















































































































8 




















/ 






































800 
600 
400 
200 
















< 


y 








































•i 














s 


y 


















































s 


y 









































































































40 50 60 70 SO 90 110 



130 150 

Amperes 
Fig. 41. 



170 190 210 230 250 



Acceleration. — Acceleration is the time rate of velocity and is pro- 
duced by the application of force. The application of a constant force will 
tend to result in constant acceleration. The force of gravity will accelerate 
a falling body 32.2 feet per second. The relation of acceleration to train 
performance will be shown by the following formula: Let 

T ==» the total tractive-effort or force applied in pounds. 

t = tractive effort in pounds per ton due to train resistance. 

a = acceleration in miles per hour per second, covering all train and motoi 
friction. 
W = weight in tons being accelerated. 

w = weight in tons being accelerated plus 10 per cent for fly-wheel effect. 

5280 feet per mile 



1.467 = 



91.1 



3600 seconds in an hour 
1 . 467 X 2000 



Then. 



(91 
T 



91 



32.2 
1 aW) + tW 

- tW 

TW' 



If the fly-wheel effect be considered, then 
T = (91.1 aw) + tW; 

T - tW 
a 9l.lu>* 



TRAIN PERFORMANCE DIAGRAMS. 665 

Grades. — A grade of one per cent means a change in altitude of one 
foot for each 100 feet of track on the grade, and this is equivalent to a 
tractive force of 20 pounds per ton, which will be positive, or to be added 
to the tractive effort per ton, if the train is going up grade; or to be deducted 
from the same if the train is on down grade. Then if g = grade per cent X 20 
the formula becomes 

T = (91 . 1 aw) 4- (t ± g) W and 

T - (t ± g) W 
a ~ 91.1 w. 

Curves. — Values of railway curves are expressed in terms of the 
central angle subtended by a chord 100 feet long; thus a one degree curve 
means one such that the angle at the center end of the radius will be one 
degree, or a radius of 5730 feet, thus 

de e = 5730 # 

radius in feet 

Experiment shows that the effect of curves is to introduce a resistance of 
about .6 pound per ton per degree of curve; thus a two degree curve will 
require a tractive effort of 1 . 2 pounds per ton of train to overcome the 
resistance. 

If c = tractive effort of a curve at d, degrees, the formula will become 

T = (91.1 aW) + (t+cyW; 

T - (t+c)W 
a ~ Ql.lu;. 
A combination of a grade and a curve will make the formula: 

T = (91 . 1 aW) + (* + c ± g) W; 

= T - (t + c ± g) W 
a 91.1 w 

The use of the polar planimeter will very much facilitate the construction 
of these diagrams. 

The method of constructing the speed-time curve as described below is 
about as simple as can be made and was used by Mr. H. N. Latey in laying 
out the work of the Interborough Company in New York. 

For purpose of explanation the following example of train performance 
is given: 

Example 1. for Train Performance Diagram. 

Train 3 motor cars, 2 trail cars. 

Schedule 20 miles per hour. 

Stops 2 per mile. 

Acceleration a = 1.25 m.p.h. per second. 

Braking b = 1.5 m.p.h. per second.^ 

Tractive effort t = 13 pounds per ton of train. 

Fly-wheel effect 10 per cent of train weight. 

Motors 4 for each motor car. 

Motor cars weigh 60,000 pounds each. 

Trail cars weigh 40,000 pounds each. 

Weight of train W = 130 tons. 

Fly-wheel effect =13 tons 

Total =143 tons. 

Weight on drivers all motor cars = 180,000 pounds. 

Tractive effort due to weight on drivers 18 % = 32,400 lbs. 

Tractive effort, T = (a X w X 91 . 1) + tW, 
or, T = (1.25 X 143 X 91.1) +13 X 130 = 17,974 lbs. 

and T per motor = 17974 -i- 12 = 1498 lbs. 

From motor curve, Fig. 41, 1498 lbs. = 20 miles per hour at a = 1.25. 
20 miles per hour at 1.25 miles per hour per second is the first point p on curve 



666 ELECTRIC RAILWAYS. 

Other points, P\, P2, P3» etc., are determined by the formula, 

T — t W 

a = , where T is taken from the motor curve at the miles per hour 

91.1 w 

the train is moving. 

Then, let T — tW = B, and a = , from which the following table 

may be constructed for the diagrams: 



Table I. 




M.P.H. T. Motors T. tW 


B a 


at 20 = 1498 lbs. X 12 = 17974 - 1690 = 
44 22 = 1100 " X 12 = 13200 - 1690 = 
" 24 = 840 44 X 12 = 10080 - 1690 = 
" 26 = 700 44 X 12 = 8400 - 1690 = 
" 28 = 590 " X 12 = 7080 - 1690 = 
" 30 = 500 " X 12 = 6000 - 1690 = 
" 32 = 420 " X 12 = 5040 - 1690 = 


16284 = 1.250 
11510 = .840 
8390 = .644 
6710 = .515 
5390 = .414 
4310 = .331 
3053 = .257 


Coasting after shutting off current = 


tW 
91.1 w 


13X130 1690 
91.1X143= 13027= ' 129 mph ' 


per second. 


Table II. 




Amperes per motor. 


Amperes per train 


at 20 m.p.h. = 134 X 12 = 
22 " = 108 X 12 = 
24 44 = 93 X 12 = 
26 " = 83 X 12 = 
28 44 = 75 X 12 = 
30 " = 68 X 12 = 
32 44 = 62 X 12 = 


1608 
1296 
1116 
996 
900 
816 
744 



Construction of Speed-Time Curve. — An inspection of 
Fig. 42 will show that the speed- time curve is divided into four parts: (a) 
the acceleration due to starting the motors and bringing the train up to 
the speed that will be given by cutting out all resistance, and leaving them 
in multiple connection. This is shown on the diagram by o.P. (b) the 
acceleration in multiple, running from P to s; (c) at which point the cur- 
rent is cut off and the train allowed to coast for the distance indicated 
between s and n; and (d), where brakes are applied, and from n to g the 
curve is diagonally downward, assuming that the train retards at a regular 
rate, which obviously is never the case, but is near enough so to be indi- 
cated by the straight line as shown. 

Referring to Fig. 42: The straight part of the curve, from o to p, is laid 
on the drawing at an angle determined by the rate of acceleration, which in 
this case is 1.25 miles per hour per second. The example shows that at 
this rate of acceleration and for the weight of train given, and at a tractive 
effort of thirteen pounds per ton, a total tractive effort per motor of 1498 
pounds will be necessary, and by reference to the curve of tractive effort in 
Fig. 41, it is found that 1498 pounds correspond to a speed of twenty miles 
per hour, which becomes the first point P on the acceleration curve. At 
this point the resistance of the controlling devices is all cut out and the 
motors are in multiple from this point on, to the point s. When the current 
is cut off for coasting, the speed will be accelerated at a gradually decreasing 
rate as shown. The lines between the points p, p 1t vi Va and p 4 represent 
the average rate of acceleration for speeds of 22-24-26-28 and 30 miles per 
hour, and in each case start from a point half way between the lines which 



TRAIN PERFORMANCE DIAGRAMS. 



667 



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° 








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c 
















s, 


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668 ELECTRIC RAILWAYS. 

represent the rates of speed named, the acceleration curve o, », being ex- 
tended one-half of the speed interval selected, or to pointy, the other sec- 
tions being attached to the ends. 

The angle of these lines is determined by the rate of acceleration for the 
intervals shown, and in this example is based upon rates of speed varying 
by intervals of two miles. 

* ji tjy 

Table I has been calculated from the formula a = -£— — , T being 

taken from curve sheet, Fig. 41. 

An examination of Table I shows that at the rate of speed of 20 m.p.h., the 
rate of acceleration is 1.25 m.p.h.per second; at the average rate of 22 m.p.h., 
or from 21 miles to 23 miles, per hour, the rate of acceleration is .84 m.p.h. 
per second; at 24 m.p.h., or from 23 to 25 miles per hour, the rate of accelera- 
tion is .644 m.p.h. per second, etc., etc. In practical work intervals of one 
mile each should be taken, as the curve will then be more nearly correct. 

Coasting*. — At the point s current is cut off and the train allowed to coast 
to the point where brakes are applied and the train brought to rest at the 
point g, 85 seconds from the starting point o. The rate of retardation, or 
as it is sometimes called, deceleration a, of coasting is determined by the 

tW 
formula, az=— , or in this case, — .129 m.p.h. per second. 

Braking*. — This line is laid on the sheet at an angle representing the 
rate of 1.5 m.p.h. per second stated in the example. 

Locating* the Coasting- JLine. — The area inclosed by the 
rectangle o,m, x, y, represents the distance traveled by train in the time 
shown, or a speed of twenty miles per hour, for a half mile, with a stop of 
5 seconds duration. Therefore, the area inclosed by the speed-time curve 
o, p, 5, n t <7, must be equal to that of the rectangle o, m, x, y, which can be 
best determined by a polar-planimeter. The coasting line s, n is then 
adjusted up or down, always retaining the angle due to the rate of acceler- 
ation, until the area inclosed by the speed-time curve is the same as that of 
the rectangle. The maximum speed will then be shown by the point s, in 
this case 30.5 miles per hour. 

Distance-Time Curve. — This curve should be plotted at the 
same time and in connection with the speed-time curve. Its value may be 
determined for as many points as desired, but it will be sufficient for all 
practical purposes if plotted for two second intervals at the start and at the 
end, as shown on Fig. 42, and at longer intervals, say 5 seconds for the 
straight part of the curve. The values may be calculated at any point 
along the speed-time curve and this has been done on Fig. 42, at the same 
points as were assumed for calculating the speed-time curve. 

If D = distance from starting point in feet, 
and d = distance in feet traversed in time t y then 

. 5280 vt 

d = -3600- = a - 466 Vt > 
and D = d + d x + d 2 + d 3 + d 4 , etc., etc. 

If the speed-time curve is very irregular it is more convenient to use a 
polar-planimeter in getting the average rate of speed, but in cases like that 
shown in Fig. 42, where the sections of the curve are drawn in straight lines, 
the average rate of speed will be at the center point of each section, and 
the time interval t is the time space covered between the ends of the 
section. For instance, to locate the first point on the distance-time curve 
at t, the average speed for the time interval of 10 seconds is 12.5 -5- 2 = 6.25, 
then 6.25 X 10 X 1.467 = 91 feet and this value laid off on the sheet over 
the time 10 seconds, and at a value of 91 feet on the scale of " distance 
feet" shown at the right, gives the point t. 

The average speed on the speed-time curve between 12.5 miles per hour 
and 21 miles per hour, is 16.75 miles per hour for the time interval t, 
between the two points shown, of 6.5 seconds; then 16.75 X 6.5 X 1-467 = 159, 
and 

X) = 91, + 159 = 250, or the point t } on the distance-time curve. Again 



DISTANCE-TIME CURVE. 



669 



the average speed between the next two points p and p t is 22 miles per hour, 
and the time interval is 2.5 seconds, thus, 

22 X 2.5 X 1.467 = 80 and D = 250 + 80 = 330, 
which is the location of point fo. 

The above described process is repeated to obtain each point on the curve. 
Table III has been constructed in this way in order to show the progressive 
value of D. 

Great care should be exercised in plotting both speed-time and distance- 
time curves as errors of location are cumulative, and when many points are 
used the error at the end may throw the result quite out of line. 

Table MI. — Data For Distance-Time Curve. 













Total 




v = 


t = 

Time 

Interval. 


Total 


1.467v* 


Distance 


Point 


Average 


Time 


= 


in feet 


Numbers. 


Speed in 


from 


Distance 


from 




M.P.H. 


Start. 


Intervals. 


Starting 
Point. 


1 


6.25 


10 


10 


91 


91.0 


2 


16.75 


6.5 


16.5 


159 


250 


3 


22 


2.5 


19 


80 


330 


4 


24 


3.0 


22 


105 


435 


5 


26 


3.50 


25.5 


133 


568 


6 


28 


4.75 


30.25 


195 


763 


7 


29.7 


5.25 


35.5 


228 


991 


8 


30 


4.5 


40 


197 


1188 


9 


29.5 


5 


45 


215 


1403 


10 


28.7 


5 


50 


210 


1613 


11 


28 


5 


55 


204 


1817 


12 


27.5 


5 


60 


200 


2017 


13 


26.7 


5 


65 


195 


2212 


14 


26.2 


3 


68 


113 


2325 


15 


22 


5 


73 


158 


2483 


16 


14.2 


5 


78 


103 


2586 


17 


6.7 


5 


83 


48 


2634 


18 


1.5 


2 


85 


4 


2638 



Current Curve. — From the speed curve on Fig. 41, the current, 
taken at a speed of 20 miles per hour, is found to be 134 amperes, which for 
12 motors will be 1608 amperes for the train. Point c is thus located, and 
the current taken with motors in multiple is twice that required for series 
running, which locates point d. 

At 22 miles per hour the curve shows that the motor will require 108 
amperes, or 1296 for the 12 motors, which locates point c. Table II gives 
the location of all the points on the current curve, having been made up 
from the curves on Fig. 41. 

Voltagre Curve. — It is only possible to plot this curve from actual 
test, though in estimating, it is common practice to assume an average 
voltage in order to work out the power curve. 

rower or Kilowatt Curve. — This curve is plotted from a 
combination of the current curve and the voltage curve, the instantaneous 
values of each being multiplied to obtain the value of the power at the 
point taken. For simplicity neither of the last two curves are plotted here. 
In practice the kilowatt ourve is ordinarily plotted by using the average 
line potential together with the current curve. 

Example ]¥o. M. — This run is of the same length as that in Example 
No. I, i.e. one half mile, but instead of being all straight and level track, 
includes several grades and curves with a portion of track which is straight 
and level. At the right of Fig. 43 is shown the profile and contour of the 
line giving the length of each change, and opposite each section will be 
found the tractive effort per ton necessary to overcome the various condi- 
tions, thus: it requires 13 pounds per ton to overcome the train resistance 
on straight and level track; grades require an additional 20 pounds per ton 
for each per cent of change, and the values are shown in column g. In the 



670 



ELECTRIC RAILWAYS. 



SUOX 08T 




DISTANCE-TIME CURVE. 



671 



third column are shown the various efforts per ton necessary to overcome 
the resistance of the curves, at the rate of . 6 pounds per ton per degree. 
The fourth column shows the combined values of all the tractive efforts 
for each division of the run, and in the last column are given the total 
tractive effort for the train of 130 tons weight. 

Table IV. — Data for Speed-Time Curve, Fig-. 43. 





T. 




T. 


M.P.H. 


Per 


No. 


for 




Motor. 


Motors. 


Train. 


20 


1498 


12 


17974 


21 


1300 




15600 


22 


1100 




13200 


23 


960 




11520 


24 


870 




10440 


25 


760 




9120 


26 


700 




8400 


27 


640 




7680 


28 


580 




6960 


28.5 


560 




6720 


28.7 


550 




6600 


29.7 


500 




6000 
Coast 


29 


540 




6480 
6110 

Braking 

Coast 
Braking 



tw. 


B. 


B 

a 13027 


- 1690 


16284 


1.250 


- 1690 


13910 


1.068 


- 1690 


11510 


.883 


- 1690 


9830 


.754 


- 1690 


8750 


.672 


- 1690 


7430 


.570 


- 1690 


6710 


.515 


- 1846 


5834 


.448 


- 1846 . 


5114 


.393 


- 1846 


4874 


.375 


- 4290 


2310 


.177 


- 1924 


4076 


.313 


- 1924 


1924 


- .148 


- 6890 


- 410 


- .032 


- 1690 


+ 4420 


+ .340 


- 1690 


- 1690 


- .130 

- 2.05 


- 1690 


- 1690 


- .130 

- 1.5 



Table V. — Data for Distance-Time Curve, Tig-. 43. 



Point 
Numbers. 


v. 


t. 


Total 
Time 
from 
Start. 


1.467* 

Distance 
Intervals. 


Total 
Distance 

from 
Starting 

Point. 


1 


6.25 


10.0 


10.0 


91 


91 


2 


16.50 


6.5 


16.5 


157 


248 


3 


21.00 


1.5 


18.0 


46 


294 


4 


23.00 


2.5 


20.5 


84 


378 


5 


25.00 


3.5 


24.0 


128 


506 


6 


26.50 


2.25 


26.25 


87 


593 


7 


27.50 


2.25 


28.50 


91 


684 


8 


28.13 


0.75 


29.25 


21 


705 


9 


28.60 


4.65 


33.90 


195 


900 


10 


29.70 


1.60 


35.50 


69 


1969 


11 


28.70 


5.50 


41.00 


238 


1207 


12 


29.00 


4.75 


45.75 


200 


1407 


13 


28.70 


7.15 


52.90 


300 


1707 


14 


29.50 


7.85 


60.75 


340 


2047 


15 


27.50 


2.5 


63.25 


100 


2147 


16 


23.70 


7.0 


70.25 


240 


2387 


17 


18.75 


5.0 


75.25 


148 


2527 


18 


11.25 


5.0 


80.25 


83.5 


2610 


19 


3.75 


5.0 


85.25 


28.5 


2638 



672 



ELECTRIC RAILWAYS. 



The speed-time curve on Fig. 43 is worked out in the same manner as that 
on Fig. 42, except that while the speed-time curve in Fig. 42 may be plotted 
without reference to the distance- time curve, in the case of Fig. 43, they 
both must be plotted together, as care must be taken that the speed-time 
curve is not carried beyond the point where the tractive effort, and, therefore, 
the acceleration changes, as at T, T it T it etc. 



Table VI. — Current Data for Wig. 43. 



M.P.H. 


Amps, per Motor. 


Amps, for Train. 
12 Motors. 


20 


134 


1608 


22 


108 


1296 


24 


93 


1116 


26 


83 


996 


28 


75 


900 


30 


68 


816 


29 


71 


852 



Tables IV and V are made up as the plotting progresses, and in the former 
give the values of a at which to lay the speed-time curve, and in the latter 
show the distance D and the time t u being respectively the distance and 
time from the starting point o. 

It requires considerably more care to work out one of these irregular 
curves for, while the method here explained is probably as short and as 
simple as any, yet it requires much cut-and-try to make the sections of the 
two curves fit for time and distance, and the location of the point s, at which 
current is cut off and coasting begins, requires experience and judgment, 
in order that the total area of the speed-time curve o, p, s, n, g, may equal 
that of the schedule o, m, x, y. 

Both the previous examples have dealt with short runs where the motors 
are never left in circuit long enough to reach their speed and current limit. 
In case of long runs as on suburban lines, current is left on in full, and the 
train is accelerated until the values of T = tW, and B is therefore zero and 
there is neither acceleration or deceleration, the train moving forward at a 
level rate^ of speed, as the tractive effort is just enough to overcome the 
whole train resistance. 

The values of T and tW will then only be varied by grades and curves, 
and the prolongation of the acceleration curve will have to be plotted to 
the point when coasting can begin in order to complete the time schedule. 
Of course if the track is straight and level, after T = tW, the speed-time 
curve will be straight and level to the coasting point s, and the current 
curve also will have reached a constant value and its curve will be a straight 
line until cut off for coasting. 

Curves must be plotted for each run, then motors best adapted for all 
purposes can be selected and the amount of power needed and the best 
equipment for producing the same can be determined. After all points 
have been carefully considered, due attention must be given to future needs, 
and great care be taken that the equipment has not been worked up to s 
fine a point that no allowances have been made for the idiosyncrasies of 
the motorman who, in many cases, will entirely undo all the results of fine 
calculation. 

Curves like that in Example II are seldom calculated as rolling-stock; 
being operated in both directions, grades practically neutralize each other, 
so that a curve like that in Example I for straight and level track is 
quite accurate enough for all practical purposes. 



RATING THE CAPACITY OF RAILWAY MOTORS. 673 



IMTiVG THE CAPACITY OF R1IIWAT MOTORS 
FROM PERFORMANCE CURVE*. 

The limiting condition in rating the capacity of a railway motor is the 
heat developed in its use. 

"When a motor is carrying any load, certain copper and iron losses take 
place in it, which depend upon the load. It is these losses, which appear 
as heat, that tend to raise the temperature of the windings. Thus a loss of 
three watts (neglecting radiation) will raise the temperature of one pound 



—el- 
-1400 
-1300 
-1200 
-1100 
-1000 
-900 
-800 




















1 / 






WESTING HOUSE 
No. A RAILWAY MOTOR 

500 Volts 
Iron Loss Curves 




VI 




























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-200 

-100 
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2C 


10 21 


Volts 
300 3£ 


4( 


41 


« 


X) 51 


)0 



Fig. 44. 



of copper approximately 1° C. per minute, or of one pound of iron approxi- 
mately .8° C. per minute. The copper loss depends upon the current only, 
and is proportional to its square, but the iron, or core loss, depends upon 
both the current and the voltage and does not follow any simple law. The 
iron loss in the motors in question, when carrying any given current at any 
given voltage, is shown in Figs. 44 and 45. Its dependence on both 
current and voltage may be seen in Fig. 44, from the fact that 20 
amperes at 500 volts produces the same loss as 105 amperes at 305 volts. 

Owing to the great mass of metal in its frame, a motor has a considerable 
amount of heat-storage capacity. Instead of only a few hundred pounds of 
copper in the windings to be acted on, the temperature of the frame must 
also be raised ; when cooling, the entire mass must cool off simultaneously- 



674 



ELECTRIC RAILWAYS. 



That is, when the temperature of the windings is rising, that of the frame 
must also rise, and similarly when falling. The actual temperatures of the 
different parts may, of course, be widely different. Owing to this action, 
the temperature of the windings of the motor does not fluctuate in accord- 
ance with the instantaneous losses but rises at a fairly uniform rate depending 
on their average value. 

The important factor as regards the effect of the service loads on the 
motors, provided that the maximum loads are within the proper limits, is 
thus the average value of the losses, averaged, of course, over the entire 
time of the cycle. It is evident that the average copper loss in any case is 



J2 






















/ 


£ 






WESTINGHOUSE 

No. B RAILWAY MOTOR 

500 Volts 

Iron Loss Curves 






/ 


-5500 
-5000 
-4500 
-4000 
-3500 
■3000 
-2500 
-2000 
-1500 
-1000 
-500 










/ 


















A. 




/ 




































/ / 




























































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fs 


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s* 










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5^ 
































P^ 




































50 100 J« 


200 250 300 350 400 450 500 550 U0 ) 
1 Volts I I I I I 



Fig. 45. 



equal to that which would be produced by the continuous application of a 
current equal in value to the root mean square of the service currents. 
Thus, if this current and voltage is applied to the motor for the entire cycle, 
the average losses in the motors — both copper loss and iron loss — will 
have the same value and the same distribution as the losses due to the 
service loads. This voltage may be called the "equivalent" voltage of the 
service. 

This method of equating the service loads on a railway motor to simple 
and intelligible terms was devised by Mr. N. W. Storer, of Pittsburg, and 
gives a convenient way of expressing the service capacity of railway motors 
in a usable manner. 

The limiting capacity of any type of motor may be readily expressed by 
the manufacturer in terms of the current (root mean square) which it will 
carry continuously at various voltages (equivalent voltage) with a safe rise 
in temperature. In choosing a motor for a given service, the root mean 



RATING THE CAPACITY OF RAILWAY MOTORS. 675 

square current and equivalent voltage can be calculated from the speed- 
time curves and a comparison of these results with the values allowable for 
the motor in question will determine its fitness. Where motors are already 
installed, the continuous equivalent of the service can be found by means 
of comparatively simple tests and the relation of the actual loads carried 
by the motors, to their safe capacity, thus determined. 

It has been found that where the equivalent voltage is less than 300, a 
reduction of voltage, with the same current, makes but little difference in the 
temperature attained. Even when the equivalent voltage is changed from 
300 to 400 volts only a comparatively slight reduction in current is neces- 
sary in order to maintain the same temperature rise. Thus the capacity 
need be stated at only one or two different voltages. 

In many cases where tests or calculations are made to determine the 
approximate service loads on a motor, the average voltage at the motor 
terminals is a sufficient indication of the iron losses, and the equivalent volt- 
age need not be determined. 

An ammeter in the circuit of one motor and a voltmeter at the terminals 
of the same motor, read at suitable intervals during a typical round trip 
over a given route, will thus give sufficient data for determining the loads 
which a motor is carrying in service. From the current readings, the root 
mean square current can be found, and from the voltage readings, the average, 
or the equivalent voltage. The starting current is a most important factor 
in determining the copper loss, hence it is essential to get an accurate idea 
of this. On account of the rapid variations of the current while the car is 
starting and the short duration of the starting currents, readings should be 
taken at very close intervals, preferably at intervals of five seconds, or less, 
in order that the large currents used in starting may be duly represented 
in the results. 

The capacity of a railway motor is expressed in two different ways : 

1st Commercial Rating*. — This is the horse-power output of the 
motor that will give a temperature rise of 75° C. above the surrounding air 
after a run of one hour. It also is about the maximum momentary output 
which the motor is called upon to deliver in service. The commercial or horse- 
power rating of a motor does not indicate its capacity to do work in regular 
operation where the demands upon the motive power are very irregular; 
hence there has arisen the need of a service rating by means of which the 
proper motor can be selected for a given service without the necessity of 
going through a mass of tedious calculations. 

2nd Service Capacity. — The temperature of a railway motor in 
service should not rise more than 65° C. above that of the air, as a higher 
temperature is liable to cause deterioration of the insulation and thus 
increase the cost of maintenance. 

The most convenient service rating of a railway motor shows the relation 
between the rate horse-power (commercial) and the weight of car in tons it 
can propel at any speed. This should be given also for both single car and 
train operation in order to comply with the different train friction rates 
with different composition of trains. 

Example. — Given a 48-ton car running singly at 45 miles per hour, 
what capacity motor is required with a four-motor equipment? See curve 
sheet, Fig. 48, made from "C" friction curve for single car operation. Four- 
motor equipment and 48 tons gives 12 tons per motor. Follow 12-ton line 
horizontally until it cuts curve labeled 45 miles per hour, drop to scale at 
bottom and find 115 horse-power motor required. Select next larger size 
from standard 'lists of manufacturers. 

Curve sheets 46, 47, 48 are made for 

"A" Trains of 10 cars or more. 
"B" Trains of two cars. 
"C" Single cars. 

The four curves on each plate are made for 30, 45, 60 and 75 miles per 
hour, and these values represent the maximum speed the car will reach with 
550 volts on the motors and on a level tangent track. 

Do not make the mistake of choosing a motor too small for the work to 
be done, as it will cost more in the end, due to increased cost of maintenance. 



676 



ELECTRIC RAILWAYS. 



Lay-over«, — Should there he considerable lay-over at the ends of the 
run, it may be possible to select the next size smaller standard motor to the 
one indicated bv the curves. By a considerable lay-over is meant 15 per 
cent of the running time. Thus a run of 20 miles, requiring 60 minutes for 
a suburban run, should have a lee-way or lay-over at each end of the run of 
10 minutes, in which case it would be feasible to select the next smaller 
standard size motor than the one indicated by curves. 



MOTOR CAPACITY CURVES 
60°CLtise 
A- Friction Curve 
550 Volts 
Gross acceleration 120 Lbs. per ton 
Braking 120 " u kl 

Duration of stops 15 Sec. 
Coasting 10 « 

Level tangent track 



y 

85 
80 
75 

70 










































































































































































































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5b 

50 
45 
40 
85 
30 
25 
20 
15 
10 
































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.40 60 80 100 120 140 160 

Commercial H. P. Rating of Kotor 



180 200 



Fig. 46. Motor Capacity Curves, 60° C. Rise. A-Ffiction Curve. 



MOTOR SERVICE CAPACITY CURVES. 



677 



SERVICE CAPACITY CURVES 

B-Friction Curve 
550 Volts 
Gross acceleration 120 Cbs. per ton 
Braking- 130 " " *» 

Duration of stops 15'Sec. 
Coasting 10 u 

Level tangent track 



f- 










































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64 
60 


















































































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48 
44 


































































































































































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32 
28 
24 
20 
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JL0 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 
Commercial H.P. Eating of -Motor 

Fig. 47. Motor Capacity Curves, 60° C. Rise. B-Friction Curve. 



ELECTRIC RAILWAYS. 



SERVICE CAPACITY CURVES 

G -Friction Curve 

550 Volts 

Gross acceleration "120 Lbs. per ton 
^Braking - 120 u . M *• 

Duration of stops 15 Sec. 
Coasting 10 *■» 

Level tangent track 



o 










































68 

64 
60 
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, 10 20 HO 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 
v Commercial H.E. Rating of Motor 

Fig. 48. Motor Capacity Curves, 60° C. Rise. C-Friction Curve. 



ENERGY REQUIRED FOR ELECTRIC CARS. 



679 



GRAPHICAL APPROXIMATION OF ENERGY 
REdllRED FOR ELECTRIC CARS. 

Mr. A. H. Armstrong has developed a series of curves, based upon the 
friction diagram, Fig. 49, from experiments by W. J. Davis, Jr. By the use 
of these curves a quick approximate determination of power required may 
be made. The curves shown in Figs. 50, 51, and 52, are referred to curves 
A, B t C, respectively on diagram, Fig. 49. 



100 
90 
80 
70 

S 50 



10 



TRAIN FRICTION CURVES 

A Ten or more 40 ton ears 



Two 40 ton cars 
One 40 ton car 





-4- —> 


t z 


/a / Z 


-t A y 


FT 7 z ^ 




h ^ y y 




\ / /- 


I ~f~7^ 


14-/ 


t~tz 


-4/ - T 


Mf 


liY- 


t 


t T - 


\f 


._. 



10 



30 40 50 

Lbs. per Ton 



Fig. 49. Friction Curves. 



Example: — Given an eight-car train for a schedule speed of 25 miles per 
hour; to find the maximum speed and watt-hours per ton-mile, at one 
stop per mile. 

Look along the bottom of the diagram. Fig. 50, for one stop per mile; 
vertically above this, opposite 25 miles per hour will be found a curve; follow 
this curve upward to the left to the zero stops per mile where will be found the 
maximum speed 45 miles per hour. Again, above the one stop per mile the 
maximum speed curve of 45 miles per hour crosses, opposite 68 watt-hours 
per ton-mile in the first column. 



680 



ELECTRIC RAILWAYS. 





190 


95 




180 


90 




170 


85 




160 


80 




150 


75 




110 


70 




130 


65 


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120 


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60 


30 




50 


25 

i 




40 


20 




30 


16 




20 


10 




10 


5 











SPEED AND ENERGY CURVES 
A-Friction Curve 
550 Volts 
Gross acceleration 120 Lbs per Ton. 
Braking 120 •» " •* 

Duration of stops .15 Sec. 

Coasting 1Q " 

Level tangent track 















































































































































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1.5 2 2.5 

Stops per Mile 



3.5 



Fig. 50. Speed and Energy Curves. Referred to A-Friction Curve of Fig. 49. 



ENERGY REQUIRED FOR ELECTRIC CARS. 



681 



I 



SPEED AND ENERGY CURVES 

B-Friction Curve 
550 Volts 
Gross acceleration 120 Lbs. per Ton. 
Braking 120 " " " 

Duration of stops 15 Sec. 

Coasting 10 " 

Level tangent track 



190 95 

180 90 

170 85 

160 80 

150 75 

140 70 

130 65 

120 60 

110 £ 55 

100 ^ 50 
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70 35 
60 30 

50 25 
40 20 
30 15 


























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20 10 

10 5 













































































Fig 



.5 1 1.5 2 2.5 3 3.5 4 

Stops per Mile 

51. Speed and Energy Curves. Referred to B-Friction Curve of Fig. 49. 



682 



ELECTRIC RAILWAYS. 



190 
180 
170 
160 
160 
140 
o 130 

E 120 

o ffi 

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1,100 S 

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80 5 

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70* 

60 
50 
40 
30 
20 
10 




SPEED AND ENERGY CURVES 

C-Friction Curve 
550 Volts 
Gross acceleration 120 Lbs per Ton. 
Braking 120 » •« " 

Duration of stops 15 Sec. 

Coasting 10 k ' 

Level tangent track 









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Fig. 52. Speed and Energy Curves. Referred to C-Friction Curve of Fig. 49. 



ENERGY REQUIRED FOR ELECTRIC CARS. 



683 



The controlling factor in all of these curves is the friction curve, which 
includes track, rolling, journal and wind-friction. 

The constants assumed in calculating the above curves are those pertain- 
ing to average high-speed suburban work as follows: 

Gross accelerating rate 120 lbs. per ton 

Braking effort (average) 120 lbs. per ton 

Duration of stop 15 seconds each. 

Track assumed to be perfectly straight and level. 

In the above curves, due consideration is given to all the losses occurring 
during acceleration with the standard series-parallel controller and direct- 
current motors. 



70 








1 Car 


Train 








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Fia. 63. - Train Resistance Curves for 1 Car Train 



The inertia of the rotating parts of the equipment generally amounts to 
5 per cent and this value is taken throughout, being perhaps a little high 
for the higher speeds and low for the lower speeds. The speed curve of a 
standard 125 horse-power motor is used throughout. The energy curves 
given are somewhat affected by the amount of coasting done, although this 
is not so determining a factor in high-speed work as it is in slow-speed accel- 
erating problems. In order that the energy curves should be conservative, 
they are plotted with only 10 seconds of coasting permitted and therefore 
the schedule speeds given are nearly the maximum possible, and the energy 
curves given are also practically the maximum possible with the maximum 
speeds assumed. Should power be shut off earlier and more coasting be 



684 



ELECTRIC RAILWAYS. 



permitted, the energy consumption would have been decreased and the 
schedule speeds decreased somewhat also, especially with the more frequent 
stops per mile. .„ , . 

An inspection of these three sets of curves will bring out the very great 
effect of the wind-friction when using trains of one or two cars at very high 
speeds* in fact at 75 miles per hour maximum speed the operation of single 
car trains becomes impracticable with light 40-ton cars of standard construc- 
tion, and even at 60 miles per hour is questionable. To quote from the 
curves, it requires an energy consumption of 47 watt-hours per ton-mile 
for a train of several cars, as against 137 watt-hours per ton-mile for a single 

















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) 40 50 60 

Speed in Miles per Hour 
Fiq. 54.-Train Resistance Curves for 5 Car Train 
Length of Car, 51 V' 
Height, 89M" 
Diameter of wheel, 33 * 
Effective area, 96 square feet. 
jtfo. of units,5. 



car operating at 75 miles per hour without stops ; that is, a single car opera- 
tion would demand 3.7 times the energy per ton that would be required 
for the operation of a train of many similar cars. Even a two-car train 
will require but 92 watt-hours per ton-mile, or only 67 per cent of the energy 
required per ton for single car operation. As these values are for constant- 
speed running, while more or less frequent stops would obtain, a comparison 
at say one stop in 4 miles would be nearer the actual results in practice. 
Here a single car requires 157 watt-hours per ton-mile, a two-car train 
requires 120 and a train of several cars 79 watt-hours per ton-mile. 

With one stop in 8 miles it is possible to make a schedule of 61 miles per 
hour with maximum speed of 75 miles per hour, and a schedule of 28 miles 
per hou. with maximum speed of 30 miles per hour. If stops be increased 



MOTOR CHARACTERISTICS. 685 

so that they average one per mile, however, the schedule speed possible with 
a maximum speed of 75 miles per hour is dropped to 29 miles per hour, while 
the 30 miles per hour maximum speed permits of a schedule speed of 22 
miles per hour. Thus while 30 miles is but 40 per cent of the higher maxi- 
mum speed it permits a schedule at one stop per mile of 76 per cent of that 
possible with 75 miles per hour maximum speed. The fallacy of using high- 
speed equipments for frequent stops is forcibly brought out by referring to 
the energy curves in Figs. 50, 51, and 52. With one stop per mile it requires 
200 watt-hours per ton-mile with 75 mile maximum speed equipment, and 
the 30 miles maximum speed equipment can obtain 76 per cent of the same 
schedule with an expenditure of only 28.5 per cent of the energy. 

Figs. 53 and 54 show the comparative values of train resistance as deter- 
mined by various authorities. Following are several train resistance 
formulae. 

Baldwin, R = 3 + Jr 
o 
V 

Engineering News, R = 2 + — 

Davis (45-ton car), R = 4 + .13 V + ' * T [l + .1 (N - 1)] 

, Smith, R - 3 + .167 V + .0025 ^ V* 



Mailloux, R =(~7= + ff) + .15 V + 



.02 AT + .25 y2 



Where 

R = resistance in pounds per ton. b- = constant depending on diame- 

V = velocity in miles per hour. ter of wheels and journals (6 to 9). 

A = cross section of car in square feet, g = constant depending on condi- 
T = weight of train in tons. tion of track (2 to 5). 

N = number of cars per ton. n = total number of cars in train. 



MOTOR CHARACTERISTICS. 

Railway motor characteristics are generally expressed in curve form as 
speed in miles per hour for 33 inch wheel, tractive effort at the rim of a 
33-inch wheel and efficiency. The efficiency is ordinarily expressed as 
tlie relation between the electrical input to the motor and the mechanical 
output from its armature shaft. When the losses in the gears connecting 
the armature shaft with the car axle are also deducted, the efficiency thus 
obtained gives the relation between the electrical input to the motor and 
the output at the rim of the car wheel. This relation is ordinarily referred 
to as "efficiency with gears." The efficiency with gears is the one most 
generally used, although it is best to have both given in order to eliminate 
errors made by determining gear and friction losses by different methods of 
unequal degree of accuracy. 

Motor characteristics form the basis of all calculations involving maxi- 
mum and schedule speeds and are generally determined for 500 volts, 
although nearly all railway motor are now designed to operate at 600 volts. 
Several typical motor characteristics follow. It is not practicable to include 
more, as styles of motors change so rapidly. 

Note. — In changing gear ratio on the same class of motor the sum of the 
number of teeth in gear and pinion must always be the same. For example, 
for GE-58-A-3; GE-58-A-4; the sum of the number of teeth in gear 
and pinion is always 84. 



686 



ELECTRIC RAILWAYS. 



40 H.P. output at 71 Amp. input 

Volts at Motor Terminals 500 

Diameter of car wheel 33" 



Armature 3 turns, Field Spools 110.5 turns 
Pinion 19, Gear 59, Ratio 3.42. 



100 


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40 20 30 40 50 60 70 80 90 100 110 
Amperes 

Fig. 55. G. E.-67-A-4. 



65 H.P. output at 113 Amp. input 
Volts at Motor Terminals 500 
Diameter of car wheel 33" 



Armature 2 turns, Field Spools 70.5 turns 
Pinion 25, Gear 64, Ratio 2.56. 





60 




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20 40 .60 80 100 120 140 160 180 20C 
Fig. 56. G. E.-74-A-9. 



MOTOR CHARACTERISTICS. 



687 



J5H. P. output at 130 Amp. input . _ . M «+,' fl tn^ia o ./Large 80 turns 
Volts at Motor Terminals 500 ^mature 2 turns, Field Spools { Sm | n 4 



Diameter of car wheel 33" 
56 



48 
44 

40 
36 
32 



Pinion 24, Gear 51, Ratio 2.12. 



L 40 turns 



100 
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Amperes 



35 H. P. output at 65 Amp. input Armature 3 turns, Field spools 143 turns 
Volts at motor terminals 500 Pinion 15, Gear 69, Ratio 4.6 

Diameter of Wheels 33" 



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688 



ELECTRIC RAILWAYS. 



100 
90 
80 

o 

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o 

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| 40 

(2 so a 

20 



10 




125 H.P. output at 208 Amp. input 

Volts at motor terminals 500 

Diameter of Wheels 33" 

Armature 1 turn, Field spools | Large 56 turns 

i Small 29 turns 

Pinion 29, Gear 60, Ratio 2.07 



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100 120 140 160 180 200 220 240 260 
Amperes 



200 H.P. output at 340 Amp. input 
Volts at motor terminals 500 
Diameter of Wheels 33" 

Armature 1 turn, Field spools \ Lar S e 35 turn s 
( Small 35 turns 
Pinion 20, Gear 63, Ratio 3.15 





40 

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MOTOR CHARACTERISTICS. 



I 



40 H.P. output at 72 Amp. input 

Volts at motor terminals 500 

Diameter of car wheel 33' 

Armature 3 turns* Field spools 110.5 turns 

Pinion 17, Gear 69. Ratio 4.06 





28 


2400 




26 


2200 


100 


24 


2000 


90 


22 


1800 


80 


20 


1600 


70 


18 


1400 


60 


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1200 


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800 


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4 







10 20 30 40 50 60 70 80 90 100 110 
Amperes 

Fig. 61. G. E.-80-A-1- 



690 



ELECTRIC RAILWAYS. 



100 
90 
80 
70 
60 
50 
40 
30 
20 
10 



36 
32 
28 
24 
20 
16 
12 
8 
4 




I 



2000 
1800 
1600 
1400 
1200 
1000 
800 
600 
400 
200 




40 ti.P. output at 72 Amp. input 

Volts at motor terminals 500 

Diameter of car wheel 33' 

Armature 3 turns, Field spools 110.5 turns 

Pinion 19. Gear 67, Ratio 3.53 





















































































_\_ 


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Fig. 62. G. E.-80-A-3. 



MOTOR CHARACTERISTICS. 



691 



£ 



40 H.P. output at 72 Amp. input 

Volts at motor terminals 500 

Diameter of car wheel 33' 

Armature 3 turns, Field spools 110.5 turns 

Pinion 22. Gear 64. Ratio 2.91 



100 


40 


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36 


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Amperes 

Fig. 63. G. E.-80-A-4. 



692 



ELECTRIC RAILWAYS. 



I 



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3200 



3000 
2000 





26 


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€OAf.& output at /05 Amp. input 
Vo/Cs at motor terminaAs 0~00 
Diameter of car pvneeis 33" 
Armature 2 turns. r~/e/c? spooAs 87. S turns 
Pinion /6~ Gear 7/. Ratio <4*44 



T 


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Amperes 



Fig. 64. G. E.-87-A or B-l. 



MOTOR CHARACTERISTICS. 



693 



t 

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Vb/ts at motor ter/n/naAs 300 
O/ameter of car wneete 33" 
Armature 2 turns. r7e/aTspoo/s 67.3 turns 
P/n/on 23. Gear 64 . f?at/o 2. 73 



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Fig. 65. G. E. -87-A or B-4 



694 



ELECTRIC RAILWAYS. 



^snt Ter S trac- 5e HP ' out P ut at 88 Am P- m P"t Armature 2 turns, Field 
pffipi hmir tivA Volts at motor terminals 500 spools 90.5 turns 

Diameter of car wheels 33" Pinion 17, Gear 69, Ratio 4.06. 



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ency effort Diameter of car wheels 33" Pinion 22, Gear 64, Ratio 2.91. 





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695 



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ELECTRIC RAILWAYS. 















































WESTINGHOUSE 

No. 12A-25 RAILWAY MOTOR 

500 VOLTS 

GEAR RATIO, 14 TO 68 WHEELS 33' 

CONTINUOUS CAPACITY 21 AMPERES AT 300 VOLTS 

OR 20 AMPERES AT 400 VOLTS 
















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697 











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WESTINGHOUSE 
No. 92 A RAILWAY MOTOR 

500 VOLTS 
GEAR RATIO, 18 TO 66- 83* WHEELS 
CONTINUOUS CAPACITY 30 AMPERES AT 300 VOLTS 
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ELECTRIC RAILWAYS. 











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WESTINGHOUSE 

No. 101 B RAILWAY MOTOR 

500 VOLTS 

GEAR RATIO, 18 TO 66-33 WHEELS 
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MOTOR CHARACTERISTICS. 



699 





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WESTINGHOUSE 

No. 92 A RAILWAY MOTOR 

500 VOLTS 

CONTINUOUS CAPACITY, 30 AMPERES AT 300 VOLTS 
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700 



ELECTRIC RAILWAYS. 











1 1 II 1 1 1 1 1 1 II i 1 II 






o 

-13- 














WESTINGHOUSE 

No. 93 A RAILWAY MOTOR 

500 VOLTS 

CONTINUOUS CAPACITY 50 AMPERES AT 300 VOLTS 
i( n 4 6 ii tt 400 ii 






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MOTOR CHARACTERISTICS. 



701 











1 1 ii i i 1 . i i .i i ii i ii 1- 








— i 










.WESTINGHOUSE 

No, 112 RAILWAY MOTOR 

500 VOLTS 

GEAR RATIO, 16 TO 73 - 33" WHEELS 

CONTINUOUS CAPACITY 60 AMPERES AT 300 VOLTS 

. « 55 - " "400 « 










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702 



ELECTRIC RAILWAYS. 



WESTINGHOUSE 

No. 113 RAILWAY MOTOR 

550 VOLTS 

GEAR RATIO 1 9 !64- 36*WHEELS 
CONTINUOUS CAPACITY WITH COVERS ON, 1 50 AMPS. AT 350 VOLTS 







--W- 



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Amperes 

I I i II I I ! I 



Fig. 76. 



MOTOR CHARACTERISTICS. 



703 





_ 
















±±__ _ _ 




_, / 


No. 121 RAILWAY IV 


OTOR IL y 






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J 














CONTINUOUS CAPACITY 80 AMPERE 


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" " 75 " 


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704 



ELECTRIC RAILWAYS. 



WESTIT 








K|a 11Q RAI 


1 WAY MOTOR 






















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\ / / 


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/°/ i X 




VII 






100 -10 400 r?x&~ ' 


' 1000 80 










it L* // I£^o 






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:::::::::::??:::::::::::::;:;: 


=f^^^R^irW>;r 


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IN MTTPl 1 ' 1 1 1 1 ' ' 1 

00 ^0O 400 






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i 


Mill T 



Fig. 78. 



MOTOR CHARACTERISTICS. 



705 



- ■■ ■ i n 111 ii 1 1 1 1 1 1 1 1 1 1 


I I I ' II l i 1 1 I II 1 1 1 1 1 1 1 I I 


1 1 1 1 1 1 ii 1 1 1 1 1 1 ii M 


I I I i I I 1 1 | I I I I 1 1 1 1 II I 






~:: _~:::_ westi 


nJGHOUSE z i: 






; ::: no. 119 rah 


-WAY MOTOR BZ « 










_ I_ 550 


VOLTS g fj 










CONTINUOUS CAPACITY 5 


5 AMPERES AT 300 VOLTS _^T _T? 






M (i 


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Fig. 79. 



706 



ELECTRIC RAILWAYS. 



DETERMOATIOl OF EXFROTT. 

Gotshall gives the following as a method of approximating the demand 
for energy of an electric railway. 

Let 
W = maximum weight of loaded car, or train unit, in tons of 2,000 pounds each. 
D = length of road. 

T =time in minutes occupied in running between termini = single trip. 
K = energy consumption in watt hours per ton mile. 

N = number of cars or train units on the road during time of maximum 
service of minimum headway. 

Then, 
W X D = ton mile per trip = P. 

1* V K 

= energy per trip in kilowatt hours. 



1000 
P XK 

1000 
P XK 

1000 



X -^ = mean rate of energy input per car or train unit. 
.. 60 



X N = A = total maximum average energy required at the 

car motors for maximum service condition. 
If to the foregoing, 25 per cent be added for transmission losses and heat 
and light, 

60 X P X K X N X 100 n no PXKxN . 

— nnr . „ — = 0.08 — = maximum average demand = R. 

JLUUU X J- X . (O 1 

To R must be added the fluctuations, which will vary from . 2 R to . 33 R, 
as the number of train units in regular service are great and the average load 
consequently relatively high, or as the number of train units in regular ser- 
vice are few and far apart, and the consequent relative increase of the load 
during certain hours relatively great. 

In the foregoing, the quantity K is the important quantity. K will vary 
with the schedule and the location, the distance between, and number of 
stops and stations, as well as with the alignment and gradients. Table VII, 
has been compiled from data showing relations between schedule speed 
and energy consumption in watt hours per ton mile. These figures are 
based upon approximately straight and level roads. As the effect of grades 
upon energy consumption is, to a large extent, compensating, the data may 
be used with safety. The compensating effect above referred to is due to 
the fact that while a car going up-grade is consuming more energy, per 
contra a car going down-grade consumes much less or none, thereby equal- 
izing the effect of, or compensating for, the gradients. 



Table VII. 







Watt Hours per Ton Mile for Schedule Speeds of 


Stops. 


40 miles 
per hr. 


35 miles 
per hr. 


30 miles 
per hr. 


25 miles 
per hr. 


20 miles 
per hr. 


15 miles 
per hr. 


Miles. 
3 

2* 
2 
H 
1 
i 

! 


Feet. 

15,840 

13,200 

10,560 

7,920 

5,280 

2,640 

1,320 


110 
121 
142 


80 

90 

99 

123 


78 
83 
86 
95 
128 


65 
74 
80 
85 
90 
145 


53 
54 
60 
68 
74 
119 


40 
40 
41 
43 
50 
56 
120 


Train friction in 
pounds per ton 


35 


30 


27.5 


25 


20 


15 



ALTERNATING CURRENT SYSTEMS. 707 

The breaking effort or retardation is taken at 150 pounds per ton. The 
stops are taken at 15 seconds each, except in the case of the 15 miles per 
hour schedule, where the stop is taken as 10 seconds. 

The foregoing figures are for cases of approximately level and approxi- 
mately straight roads. 

For a schedule of 40 miles per hour the speed attained will be between 60 
and 65 miles per hour. A schedule of 25 miles will require speeds of from 
40 to 50 miles per hour, etc. 

The rate of acceleration for the long runs varies from 75 to 110 pounds per 
ton, going as high as 210 pounds per ton for short runs. 

The foregoing applies to single car units. If units of more than one car 
be used, the friction in pounds per ton will decrease and with it will also 
decrease the energy consumption in watt hours per ton mile. 



IL\fwLE.PHl§E ALTERHATOO CUR REIT 
SYSTEMi OF RAILW AY IHOTOIIS. 

The use of the single-phase commutator type motor for electric traction 
was first seriously advocated by the Westinghouse Electric & Manufacturing 
Company, and a description of a single-phase system, proposed by that 
company for the Washington, Baltimore & Annapolis Railway was read by 
Mr. B. G. Lamme before the American Institute of Electrical Engineers in 
October, 1902. The development of this type of motor was at once taken 
up by other manufacturers including the General Electric Company in this 
country and a number of prominent companies in Europe. The first rail- 
way to employ the system on a large commercial scale was the Indianapolis 
& Cincinnati Traction Company, which began operation over a short portion 
of its track on December 30, 1904. t • 

Practically all manufacturers employ a laminated field, an armature wind- 
ing similar in general to that used in direct-current machines, and an auxiliary 
or compensating vending on the field, to neutralize the armature reaction. 
In general, also, the single-phase motors of all manufacturers are designed 
for operation on 250 volts or less. 

A frequency of twenty-five cycles has been used exclusively in this country. 
In Europe, however, some roads employ this frequency, some lower and 
some higher frequencies. Lower frequencies are now being advocated in 
the United States. 

Sizes of motors up to 250 horse-power have been built. Those in service 
at the present time range from 40 to 150 horse-power and are used in both 
two and four-motor equipments. 

One of the essential advantages of the single-phase system is the economy 
of feeder copper which is secured, due to the use of a high trolley voltage. 
The higher the voltage the greater the saving thus effected. On the other 
hand, the greater the trolley voltage the greater the difficulty of insulating 
the line. 

Trolley voltages of 3300, 6600, 11,000 and as high as 13,000 are in use. 
No attempts have been made to standardize trolley voltages at present, but 
the general tendency seems to be toward the use of 6600 volts for ordinary 
trolley roads and of 11,000 volts for the electrification of existing steam 
railways. 

Single-phase equipments in general include, in addition to the motors, a 
specially designed trolley to collect the high-voltage current, a transformer 
to reduce the voltage for use at the motors, and the necessary controlling 
devices to regulate the supply of the current and control the speed of 
the car. These latter devices consist of drum-type controllers for small 
equipments and single car operation and unit switches operated by inde- 
pendent power for large equipments, or where multiple unit service is 
desired. 

The single-phase alternating current motor will operate equally well on 
direct current of the proper voltage and by connecting two or more motors 
in series a single-phase car equipment can be arranged to run from an 
ordinary direct-current trolley as well as from a high voltage single-phase 
trolley. With such an arrangement, cars can be run over the same tracks 
as ordinary city cars when entering a town. 



708 



ELECTRIC RAILWAYS. 



Figure 80 shows a diagram of connections for a double equipment oi 
50 horse-power single-phase motors with hand control as supplied by the 
Westinghouse Electric & Manufacturing Company. It will be seen from 




the diagram that there are five different notches on the controller, by means 
of which the motors may be connected to live different points on the trans- 
former and that the motors may be run continuously on any notch, thus 
giving five different car speeds. When running at less than the maximum 
speed, the power required is reduced in approximate proportion to the 
speed. 



ALTERNATING CURRENT SYSTEMS. 



709 



Figure 81 shows a schematic diagram of a car equipment for multiple 
unit operation on either direct or alternating current. In this equipment 
the main circuits are opened or closed by unit switches operated by com- 
pressed air from the brake system in the same way as those employed in 
the Westinghouse unit switch system of control for direct-current motors. 
The main switches are controlled by means of magnet valves operated 
through auxiliary circuits from a master switch. The auxiliary circuits 
are carried from car to car by flexible connections in the usual way so that 
the operation of the master switch on any car operates the main switches 
on all motor cars simultaneously. See Figs. 81 and 82. 

The auxiliary circuits between the master switch and the main switches 



.A.C. Trolley d.C. Trolley 




Sequence of Switches 



2 


n-j 


♦ 


tfff 


•a 




2 


• 


H 


•s 




• 


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ss 


i. . 




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b 


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O Running Notches 



Fia. 81. Schematic Diagram of Westinghouse A. C— D. C. Car Equipment. 



are led through an automatic change-over switch, which normally remains 
in the position for direct-current operation but which changes to the position 
for alternating-current operation whenever alternating current is supplied 
to the car transformer. By this arrangement operating the same master 
controller closes different main switches, according to whether direct current 
or alternating current is being used by the car. 

For the sake of clearness the auxiliary circuits are not shown on this 
diagram. 

Figure 83 shows a schematic diagram of a car equipped with four 50 horse- 
power single-phase motors for operation on 3300 volts. 

Figure 84 shows diagram of connections for a quadruple equipment of 
75 horse-power motors with hand control, as supplied by the General Electric 
Company for operation on alternating current only, and figure 85 shows 
diagram of connections for the same equipment with multiple unit control 
for operation on both alternating current and direct current. 

Figure 85 shows performance curves of typical single-phase motors 
manufactured by the Westinghouse and General Electric Companies. 



710 



ELECTRIC RAILWAYS. 



£ 



C»lt*KltrSK*tt 




itft* Chimin \\ysiBfiaKAw l mOuMtt Afasfer 

n/>;rp.tt„e,r Cwt/vlter 

tr/la/UPvmp. 



Q 




Fig. 82. Diagram of Apparatus for Unit Switch System of Multiple Control, 
A. C. Equipment. 



\Confri1ke 





Ma/ n Cylinder 



LoA^Cy/indtr^^^ockw/thOum 

/bA/'r/Teserva/r 
> Conduit. orHandPurnp. 



-V 



I Contro/Je/r 



V 



te=e> Si 



Pre yen/in /^revet/titr 
Co/'/ RtsistoKt. 




Main 
Auto-Trvnsror/nit 



Fig. 83. Diagram of Apparatus for Hand Control, A. C. Equipment- 
General Electric Company's Hand Potential Control 
System. 

This being a system of hand control for alternating current running only- 
it is less complicated and somewhat lighter than a train system. The General 
Electric potential control is also used for combined alternating current and 
direct current running by the addition of starting resistances and a commu- 
tating switch, whose office is to make the necessary change in connection. 
This potential control gives a higher efficiency equipment than is provided 
by any form of resistance control. 



ALTERNATING CURRENT SYSTEMS. 



711 




<M 



L=pi 






712 



ELECTRIC RAILWAYS. 




SINGLE-PHASE MOTOR CHARACTERISTICS. 



713 



SIWOI/E-MIASE MOTOR CHARACTERISTICS. 

Following are a number of curves showing the characteristics of the 
General Electric and Westinghouse single-phase railway motors of this date, 
November, 1906. 















rtETMETDAI PI FHTRIf 
























COMPENSATED A. C. MOTOR 

75 H. P. 200 Volts 

33' Wheel 25 Cycles 

A. C. Characteristics 


























z 


I 














o 
en 
Ul 


a. 
S 














100 


50 


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5 
















u. 

u 










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> 












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80 


40 


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;cm, 






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4 

ON 


70 




14 


"iO 






















■*^£ 


§£* 


cv- 


> FRICT 

> LOSS 




4 


13 


DO 


































60 


30 


1200 






































1100 


































B0 




1000 






































900 


































40 


20 


800 






































700 
















<sV 


















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600 














4 


Y 








^£ 














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500 












r 


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20 


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f 


























1 

300 


































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1 

100 














































































4 


) 


8 





1 


1 

AMPER 



ES 


2 


36 " 


2 


40 


2 


80 


3 


.0 











































Fig. 86. 



714 



ELECTRIC RAILWAYS. 















o.tiwc-DAi pi pot Din 


















H 




COMPENSATED A. G. MOTOR 

75 H. P. 150 Volts 

33" Wheel 

D. C. Characteristics 










H 




O 












UJ 

O 

a. 


X 


111 

> 










a 




o 
< 

BE 













100 


50 


20C 


















































90 




180 





















































— ££ 


S£*> 


(S4t 




















80 


40 


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c 


foft 


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fr a 


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f^x 
















70 




HO 













































































60 


30 


12C 

















}, 


w 

I / 






































J?/ 




















50 




IOC 















& / 




























































40 


20 


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30 




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20 


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4C 





























































i'P£ 


ED 














10 




20 



























































































































4 





B 





12 





160 

AMPERES 


2 


)0 


2- 





21 




















































Fig. 87. 



SINGLE-PHASE MOTOR CHARACTERISTICS. 



715 



fc 

o 




£ 


u 


K 


90 


a 




160 


80 


140 


70 


120 


60 


100 


60 



40 20 10 





#132 RAILWAY MOTOR 
225 Volts 3000 Alts. 








\ 36"Wheels Gear Ratio 20:63 

\ Performance of Westinghouse 
\ 100 H . P . Single Phase M otor 
\ operating at normal voltage 
\ on alternating current. 










"1 




































Ffficie 


""" s — i? 


1^ 


o*. 












































i? 


f/ 




























4 


V 


^ 












/ 











































4000 



3000 



400 
Amperei 



Fig. 88. 



716 



ELECTRIC RAILWAYS. 



o 
L80 


w 

90 


X 


60 


80 


40 



140 70 



100 60 



80 40 20 



60 80 



40 20 10 



#132 HAILWAr MOTOR 

150 Volts Direct Cucrent 

36"Wheels Gear Ratio 20:63 

Performance of Westinghouse 
100.H.P.. Single Phase Motor 
operating four in series on 
600 volts direct current. 







Fig. 89. 



SINGLE-PHASE MOTOR CHARACTERISTICS. 



717 



a*- 

LOO 



80 400 



60 300 



SO 



20 100 







#130 RAILWAY MOTOR 
220 Volts— 3000 Alts. 






^ 






Single Phase Gearless 
62 "Wheels 
Performance oi~250H..P. 
~Westinghouse gearless 
Single Phase Motor foT 
New York, New Haven 
& Harftord JEtaUtaoad. 






o 
8 
g 










1 










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sooo 










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cy*"-—— 


























4000 




















3000 












u^V 






« 










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f 




















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/ 










1000 









































800 1000 

Amperes 



1100 1200 1400 1600 



Fig. 90. 



718 



ELECTEIC RAILWAYS. 




HIGH SPEED TRIALS. 719 



Weig-nts of JLlte matins-Current motor Equipments. 

The alternating-current motors are somewhat heavier than direct-current 
motors of equal capacity. 



Comparative Weights 15 Horse-Power, four Motor 
Equipment. 

Direct Current. Alternating Current. 

Car body 22,000 lbs. 22,000 lbs. 

Trucks 14,000 lbs. 14,000 lbs. 

Motors 15,000 lbs. 20,000 lbs. 

Transformers and control 6,000 lbs. 8,000 lbs. 



Total 57,000 lbs. 64,000 lbs. 

A C 

Increased weight p ' p' = 12.3 per cent for total equipped car. 



HIGH SPEED TRIAL* OUT LAKE EJLCCTRIC 
RAJLJLWAY. 

The motor equipment of car No. 18 with which the records were made 
comprises four G. E. No. 66 125 horse-power motors, and G. E. type C 
controller, connected up for train control. A speed of 65 miles per hour 
was attained at a pressure of 575 volts. The car requires between 400 
and 600 amperes during acceleration, and 260 amperes at full running 
speed. It is vestibuled at both ends, seats 56, and is 49' 6" long by 8' 6" 
wide, weighing, loaded, 36 tons. 

On a night run from Fremont to Toledo and return, with a loaded car 
weighing 36 tons and with a clear track, the distance of 33.16 miles was 
covered in 1 hour, 11 minutes and 10 seconds on the down trip and 1 hour 
and 10 seconds on the back trip, an average of 34.3 miles per hour on 
the down trip and 35.3 miles per hour on return trip. From Fremont to 
the Toledo city limits, 30.42 miles, the time was 52 minutes and 10 
seconds, and on the return trip 44 minutes and 30 seconds, the former 
an average of 41.2 miles, and the latter an average of 41.85 miles per 
hour. It will be noticed from the accompanying table marked "theater 
run," that when the car was making its highest speed the watts per ton 
mile were practically equal to the speed in miles per hour. The current 
consumption within the city limits of Toledo where city cars were in 
operation, and where there were many bad curves, was about three times 
as great as on a straight level track and with less than one-fifth the speed. 
The increase of current consumption caused by grades and curves is also 
marked. 



720 



ELECTRIC RAILWAYS. 



8 

U 

S 

V 



c 



e 



N 
M 
N 






s 


Twenty-five stops. 

Thirty stops. 

Left Fifth Street 15 minutes late. 

Time slow; many stops on account city cars. 


d 

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aj<u0.42<uD«cJCvia; k 5D-c;cya;^D.cj(Da) P*^ 


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HIGH SPEED TRIALS. 



721 





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ELECTRIC RAILWAYS. 



I\rEHiniM\ CAR TESTS. 

By W. E. Goldsborough and P. E. Fansler. Trans. A. I. E. E. 
Tests Made upon Cars of the Union Traction Company of Indiana. 

The cars used measure 52 feet 6 inches over all and weigh 63,100 pounds- 
The motive power equipment consists of two number 50 C Westinghouse 
motors, which are mounted on the forward truck and are nominally rated 
at 150 horse-power each. The motors are geared with the ratio of 20 to 
51 and are geared to 36-inch wheels. Records were obtained from 10 
cars of this type. 

The following tables give the results for several different cars used on 
various routes, a special test of three cars, and a table showing the personal 
factor of different motormen: 



Table X. Train liOgr. 



Train No. 


Car No. 


Direction. 


K.W.H. 


K.W.H. 
Per Car Mile. 


1 
12 
19 
28 
35 


246 
246 

246 
246 
246 


East 
West 
East 
West 
East 


131.2 
128.5 
125.6 
134.8 
119 


2.32 
2.28 
2.21 
2.38 
2.11 


Average, East 








2.21 


Average, West 








2.33 












9L 
18L 
25L 
34L 


250 
250 
250 
250 


East 
West 
East 
West 


107.4 
123.8 
108.5 
119.6 


1.9 
2.19 
1.92 
2.11 


Average, East 








1.91 


Average, West 








2.15 












39 
32 

44 


252 
252 
252 


East 
West 
West 


128.7 
139.5 
113.1 


2.27 
2.46 
2.00 


Average, East 








2.27 


Average, West 








2.23 












6 
13 
22 
29 
41 
42 


254 

254 • 

254 

254 

254 

254 


West 
East 
West 
East 
East 
West 


142.5 

137.6 

139.2 

162 

119.0 

126 


2.52 
2.43 
2.46 
2.86 
2.10 
2.23 


Average, East 








2.46 


Average, West 








2.40 















INTERURBAN CAR TESTS. 
Table X. Train I^og*. — Continued. 



723 



Train No. 


Car No. 


Direction. 


K.W.H. 


K.W.H. 
Per Car Mile. 


10L 
17L 
26L 
33L 


255 
255 
255 
255 


West 
East 
West 
East 


101.0 

96.0 

106.0 

101.0 


1.77 
1.70 
1.87 
1.78 




1.74 


Average, West 








1.83 










2 
7 
15 
]6 
23 
38 


260 
260 
260 
260 
260 
260 


West 
East 
East 
West 
East 
West 


122.4 
130.6 
127.5 
114.2 
133.5 
128.5 


2.16 
2.30 
2.25 
1.85 
2.35 
2.27 


Average, E 


ast . 








2.30 








2.09 












31 
8 

24 


261 
261 
261 


East 
West 
West 


156.5 
142.0 
132.8 


2.59 
2.51 
2.34 


Average, East : 


2.59 


Average, W 


r est 








2.42 










30 
3 
14 
21 
37 


263 
262 
262 
262 
262 


West 
East 
West 
East 
East 


127.0 
111.0 
122.0 
123.0 
112.5 


2.24 
1.96 
2.15 
2.17 
1.98 


Average, East 


2.03 


Average, West 








2.19 












11 
20 
27 
40 
43 
4 


263 
263 
263 
263 
263 
263 


East 
West 
East 
West 
East 
West 


124.5 
135.5 
94.5 
134.0 
118.5 
140.0 


2.20 
2.39 
2.48 
2.37 
2.09 
2.48 


Average, East . 








2.26 


Average, West 








2.41 















724 ELECTRIC RAILWAYS. 

Table XI. Comparison of Car Tests. 



Number of car 


255 


252 


252 


Service, west bound 


semi-limited 


local 


limited 


Weight 


63,100 


63,100 


63,100 




23:48 
122 


20:51 
156 


20:51 


Total time trip, min 


126 


Time urban work, min 


44 


40 


34 


Time interurban work, min. . . 


78 


116 


92 


Average speed for trip, m.p.h. . 


28 


22 


27 


Average urban speed, m.p.h. . . 
Average interurban speed, m.p.h. 


8 


9 


10 


39 


26 


33 




18 
5 


44 
15 


12 


Urban starts 


7 


Interurban starts 


13 


29 


5 


Maximum speed, m.p.h 


64 


52 




Running speeds 


50-55 


40-45 


40-45 


Running currents 


173 


145 


145 










lbs. per ton 


27.7 


19.9 


19.9 


Time to reach 25 m.p.h 


30 


30 


30 


Acceleration current, max. series 


280-340 


200-300 


200-300 


Acceleration current, max. par . 


320-540 


250-300 


250-300 


Consumption, k.w.h., p. cm., west 


2.20 


2.44 


2.10 


Consumption, k.w.h., p. cm., east 


2.38 


2.80 


2.32 


Consumption, watt-hour per ton 








mile, west 


69.7 


77.5 


66.7 


Consumption, watt-hour per ton 








mile, east 


75.5 


89.0 


73.5 


Sq. root mean sq. current, west . 


95.6 


92.1 


78.0 


Sq. root mean sq. current, east . 


105.5 


98.4 


87.2 


Running factors, west 


43.5 


37.8 


36.2 


Running factors, east 


43.3 


31.5 


37.6 


Average voltage, west 


485 


429 




Total consumption k.w.h., west . 


124.9 


138.0 


118.8 


Total consumption k.w.h., east . 


134.3 


176.2 


131.2 



Ta1>le XII. Personal Factor of Hlotormen. Local Runs. 





East. 
Total K.W.H. 


West. 
Total K.W.H. 


Trips. 


Name. 


















Min. 


Average 


Max. 


Min. 


Average 


Max. 


East 


West 


Eller 


122 


135 


148 


114 


125 


136 


6 


6 


Lee . . 








116 


121 


126 


124 


129 


130 


4 


4 


Robbins 








122 


131 


138 


119 


124 


128 


4 


4 


Green 








113 


123 


131 


126 


134 


141 


3 


3 


Young . 








118 


122 


128 


112 


128 


145 


3 


6 


Griffin . 








124 


130 


140 


127 


131 


134 


3 


4 


Embry . 








108 


126 


154 


134 


135 


135 


3 


2 






127 






130 




26 


29 



INTERURBAN CAR TESTS. 



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RAILWAY MOTORS, STANDARD SIZES AND RATINGS. 729 



Two JflLotor vs. Four Ufotors per Car. 

Test by United Railways and Electric Company of Baltimore. 
Reported by H. H. Adams. 

Car No. 710. — 31-foot body; double trucks; 33-inch wheels; weight, 
45,000 pounds empty; seats 44 passengers; 4 Westinghouse 101 B motors; 
gear ratio 1:3.66. 

Car No. 730. — 31 foot body; maximum traction truck; 33-inch driving 
wheels; weight, 31,700 pounds empty; seats 46 passengers; 2 Westinghouse 
56 motors; gear ratio. 1:3.56. 



Test. 



Horse-power . . . 

Gear ratio .... 

Average kw. . . . 

Average amperes 
(assuming 500 v.) 

K.W.H. per car mile 

Watt-hours per ton 
mile 

Average number 
passengers carried 
per round trip 



Car No. 710. 



Relative 
per cent. 



Car No. 730. 



Relative 
per cent. 



160 
18:66 

28.47 

56.95 
3.525 

155.5 



145 



100 
100 
100 

100 
100 

100 
100 



110 
18:64 
25.65 

50.6 
3.17 

200 
148 



8.7 



97 
90 



90 
90 



128 
102 



Railway .Tlotor*. Standard Sixes and Rating-*, \ov. 1900. 



Type. 


Make. 


Rating. 


Weight. 


12A 


Westinghouse 


30 H.P. 


2200 lbs. 


49 




35 " 


1920 " 


92 




35 " 


2265 " 


68 




40 " 


2280 " 


101 




' 40 " 


2730 " 


38B 




45 '• 


2390 " 


56 




50 " 


3000 " 


93 




50 " 


3350 " 


112 




65 " 


3490 44 


76 




75 M 


3840 " 


121 




90 " 


4300 " 


119 




125 " 


4600 44 


50F 




150 " 


5550 " 


114 




160 M 


5300 " 


86 




200 M 


6600 " 


113 




200 M 


6550 " 

Weight including Gear 
and Gear Case. 


G.E. 800 


Gen. Elec. 


25 H.P. 


1800 lbs. 




52 


" " 


25 " 


1725 " 




' 1000 


14 II 


35 44 


2180 " 




67 


II II 


40 M 


2385 " 




70 


II II 


40 " 


2530 M 




80 


II II 


40 M 


2530 " 




57 


• < II 


50 M 


2972 * 4 




74 


<• II 


65 •' 


, 3534 44 




73 


II II 


75 M 


4022 " 




66 


II II 


125 M 


4378 " 




•' 55 


II II 


160 " 


5415 44 




69 


it II 


200 M 


6100 ' 4 



730 



ELECTRIC RAILWAYS. 



Weigrbts of Railway Equipments, including 1 Control 
Apparatus, Car Wiring- and HEotors. 



Type of Motor. 


Number of 
Motors. 


Type of 
Control. 


Weight. 


G.E. 800 


2 


K 10 


4,750 lbs. 


" 800 


4 


K 6 


8,740 " 


52 


2 


K10 


4,390 " 


52 


4 


K 12 


8,100 M 


" 1000 


2 


K 10 


5,310 " 


M 1000 


4 


K 6 


10,290 " 


67 


2 


K10 


5,710 " 


67 


4 


K 6 


11,090 " 


57 


2 


Kll 


6,994 " 


57 


4 


K14 


14,108 M 


74 


2 


Train Type M 


9,000 " 


74 


4 






16,586 " 


73 


2 






11,044 " 


73 


4 






20,768 " 


66 


2 






13,230 " 


66 


4 






23,760 " 


55 


2 






13,680 M 


55 


4 






26,640 " 


69 


2 






13,600 M 


69 


4 






26,600 " 


Westinghouse 12 A 


2 


Kl( 


5,400 " 


12A 


4 


K12 


10,100 M 


49 


2 


K 10 


4,900 M 


49 


4 


K12 


9,300 " 


92A 


2 


K 10 


5,570 " 


92A 


4 


K28 


10,500 " 


68 


2 


K 10 


5,700 M 


68 


4 


K 6 


10,700 " 


101B 


2 


K10 


6,600 M 


101B 


4 


K28 


12,500 M 


38B 


2 


Kll 


5,950 " 


38B 


4 


K 14 


12,150 M 


101D 


2 


Kll 


6,600 M 


101D 


4 


K28 


12,500 " 


56 


2 


K 11 


7,200 M 


56 


4 


K14 


14,600 M 


93A 


2 


Kll 


7,310 " 


93A 


4 


K14 


14,700 M 


76 


2 


K 6 


9,450 " 


76 


4 


L 4 


19,000 " 


112 


2 


K28 


8,000 M 


112 


4 


L 4 


15,750 ■« 


93A 


4 


Unit Switch 


15,145 " 


112 


4 






16,205 M 


121 


2 






10,370 " 


121 


4 






19,485 " 


119 


2 






11.495 M 


119 


4 






2lil00 " 


114 


2 






12,915 " 


114 


4 






24,455 " 


113 


2 






15,785 M 


113 


4 






29,535 " 



COPPER WIRE FUSES FOR RAILWAY CIRCUITS. 731 
TORQUE 4\I> HORSE-POWER. 



H.P. per Lb. Applied at Periphery at 100 Rev. per Min. 


Diameter 
Wheel. 


26" 


28" 


30" 


33" 


36" 


H.P. 


.02062 


.02221 


.0238 


.02618 


.02856 


Pounds at Periphery per H.P. at 100 Rev. per Min. 


Diameter 
Wheel. 


26" 


28" 


30" 


33" 


36" 


Lbs. 


48.481 


45.018 


42.017 


38.197 


35.014 




Lbs 


126050.9 
Diam. 


X H.P. 
X Rev. 







H.P. = .00000793 X diam. wheel X rev. X lbs. at periphery. 
H.P. per lb. at periphery at one mile per hour = .002667. 
Lbs. at periphery per H.P. at one mile per hour = 374.9. 



Note on Emergency Braking* of Cars. 

In case of emergency, motormen often reverse the motors, which brings 
the car up with a severe jerk, and is quite apt to strip gears. This is 
not necessary, and should never be done unless the canopy switch is first 
thrown off, then when the motors are reversed and the controller handle 
thrown around to parallel, the motors will act as generators and will bring 
the car to an easy stop with no harm to the apparatus. In case circuit 
breakers are used in place of the plain canopy switches, the reversal of the 
motors will draw so much current from the line that the circuit breakers, 
if properly adjusted, will open the circuit and the controller can then be 
used as suggested above. 



COPPER WIRE EUSES EOR RAIIWAY CIRCUITS. 



B. &S. 
Gauges. 


17 


16 


15 


14 


13 


12 


11 


10 


9 


8 


7 


Fuse Point 

in 
Amperes. 


100 


120 


140 


166 


200 


235 


280 


335 


390 


450 


520 



732 



ELECTRIC RAILWAYS. 











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DIMENSIONS AND WEIGHTS OF CARS AND TRUCKS. 



735 



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DIMENSIONS AND WEIGHTS OP BRILL CARS. 737 



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738 



ELECTRIC RAILWAYS. 



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ELECTRIC LOCOMOTIVES. 



739 



ELECTllIC LOCOMOTIVES. 

The number of electric locomotives in commercial operation is rapidly 
increasing. The service ranges from yard shifting, for which they are 
particularly well adapted, up to the hauling of passenger trains of 900 tons 
at 60 miles per hour. The motor capacity varies from two 50 horse-power 
motors of the geared type up to the four 550 horse-power gearless motors 
on the "Mohawk" type of the New. York Central locomotive. 

The following list is of interest: 1907. 







t' 






fl.S 




09 






7jj 


.* 




$ 


si 




A 




Locomotives. 


IS, 
S 


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ft 

= 

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Cayadutta .... 


1894 


l 


35 


500 


500 


58/17 


40 /r 


Freight 


96-Ton Baltimore & 


















Ohio 


1895 


3 


96 


625 


720 


Gearless 


62" 


Passenger 


Hoboken R.R, . . . 


1897 


1 


28 


500 


560 


54/17 


40" 


Freight 


Buffalo &• Lockport . 


1898 


2 


36 


500 


*300 

f600 

900 


52/21 


36" 


Freight 


Paris & Orleans . . 


1898 


8 


55 


575 


78/19 


49" 


Passenger 


Compagnie Francais 


















Thomson-Houston 


1899 


1 


38 


500 


600 


56/17 


42" 


Freight 


St. Louis & Belleville 


1901 


2 


50 


500 


360 


56/17 


33" 


Freight 


G. E. Co. 30-Ton 


















Yard Locomotive. 


1902 


1 


30 


250 


J150 
§300 


72/17 


36" 


Switching 


160-Ton Baltimore & 
















Ohio 


1903 


2 


160 


625 


1600 


81/19 


42" 


Passenger 


Bush Terminal Co. . 


1904 


1 


50 


500 


360 


52/21 


33" 


Freight 


G. E. Co. 40-Ton 


















Yard Locomotive. 


1904 


1 


40 


250 


J340 
§680 


59/18 


33" 


Switching 


N.Y. C. & H. R. R.R. 


















G. E. Co 


1904 




95 


625 


2200 


Gearless 


44" 


Passenger 


N.Y., N.H., & H. 


















R.R., W. E. & M. 


















Co 


1906 


II 


88 


600 


1000 


Gearless 


62" 


Passenger 



* Motors in series. J 250 Volts, 
t Motors in multiple. § 500 Volts. 



Operates also on 11,000 volts, A. C. 



No standard electric locomotive design has been reached, although many 
locomotives equipped with geared motors have the general shape shown 
in Fig. 92 (G. E. Co.). The motors, four in number, are geared to the 
axle by single reduction gears and are mounted on two bogie trucks, having 
about six-foot wheel base. The main cab contains the controller, and the 
sloping ends contain the necessary starting resistances. While this design 
using bogie trucks is suitable for locomotives of small capacity, it is not 
adapted to withstand the strains to which the larger locomotives are sub- 
jected, hence there has been developed a type having a solid cast-steel 
frame containing the motors of which the later B. & O. locomotives are 



740 



ELECTRIC RAILWAYS. 




Fig. 92. Typical Electric Locomotive of G. E. Co. 



typical. A cross section is shown in Fig. 93 of a half unit of the B. & O. 
locomotive. This locomotive has a rigid wheel base and contains four 
geared motors of a total capacity of 1600 horse-power. It is well adapted 
to stand the shocks of the most severe service and handles all passenger 
trains in the tunnel at Baltimore. 




Fig. 93. Electric Locomotive used in Baltimore tunnel by B. & O. R.R. 



The 6000 or "Mohawk" type of locomotive adopted by the New York 
Central R.R., shown in Fig. 94, differs from others in having four gearless 
motors mounted directly upon the axles. The armatures are not even 
spring suspended, but are keyed solidly to the axles. The dead weight 

f)er axle is said to be less than. in the case of the larger types of steam 
ocomotives. The fields are bipolar and are so arranged that the same 
flux passes through the four sets of fields in series, returning partly through 
.the side frames and partly through an overhead longitudinal frame. The 
departure from the previous methods of construction, using geared motors, 
is pronounced, and exhaustive tests seem to prove its wisdom for the pro- 
posed service. In Fig. 95 are given the motor characteristics of the 550 



ELECTRIC LOCOMOTIVES. 



741 




W 



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742 



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Fig. 95. 



ELECTRIC LOCOMOTIVES. 



743 



horse-power motor. Fig. 96 gives a specimen speed run of the 6000 loco- 
motive hauling a train of 336 tons or a total train weight of 431 tons, in- 
cluding the locomotive itself. The speed reached, 63 miles per hour, has 
since been greatly exceeded, one run being made during which a speed 
of 84 miles per hour was recorded. 

A locomotive which is of particular interest is that shown in Fig. 97. 
This is equipped with four 250 horse-power single-phase gearless motors, 
which are arranged for operation on either 600 volts direct current or 
11,000 volts single-phase alternating current. This locomotive is the first 
of thirty-five (1907), which the Westinghouse Electric and Manufacturing 
Co. has supplied to the N.Y., N.H. & H. R.R. 

It is of the double-truck type and has two swiveling trucks with a wheel 
base of 8 feet each and a distance between truck centers of 14 feet 6 inches. 























































































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Fio. 96. 



Preliminary Speed Run of N. Y. C. Locomotive 6000. 
November. 1907. 



This arrangement eliminates any danger of nosing and insures easy riding. 
The armatures of the motors are built on hollow shafts or quills which 
surround the axles and are connected to the driving wheels on each side 
by seven driving horns. These driving horns are surrounded by springs 
and fitted into pockets in the wheel hubs. The frames of the motors are 
spring supported from the journal boxes. The wheels are 62 inches in 
diameter and thus raise the center of gravity of the locomotive high above 
the track, similar to that of a steam locomotive. This arrangement, to- 
gether with the spring supports of the motors, makes the locomotive par- 
ticularly easy on the track. The general shape is such that ample room 
is obtained in the cab for mounting all apparatus so that it is readily 

The tracks of the N.Y., N.H. & H. R.R. are equipped with an 11,000 
volt overhead trolley wire, but those of the New York Central Railroad, 



744 



ELECTRIC RAILWAYS. 




INSTALLATION OP ELECTRIC CAR MOTORS. 745 

over which the trains must run from Woodlawn Junction to Grand Central 
Station, are equipped with a direct current third rail. For this reason 
these locomotives are arranged to operate from either of these conductor! 
and to change from one to the other without slackening speed. 

The motors are cooled by means of an air blast forced through them by 
motor-driven blowers in the cab and on this account they are capable of 
developing 200 horse-power each continuously, although an ordinary rail- 
way motor of the same nominal rating could operate continuously at only 
about 110 horse-power. The performance of the motor is shown by the 
curves in Fig. 90, p. 717. 

The weight of the locomotive complete is approximately 88 tons. A 
single unit is capable of handling a train of 200 tons in local service or a 
train of 250 tons in through service, and two or more units may be readily 
coupled together and operated as one for handling heavier trains. 



IA8TA114TIOA OF EIECTRIC CAR MOTORS. 

(General Electric Company.) 

In General. 

In locating the various parts of the equipment and in wiring the car, par- 
ticular attention should be taken to secure the following results : 

1. Maintenance of high insulation. 

2. Exclusion of all foreign material, particularly grease, dirt, and water, 
from the electrical equipment. 

3. The avoiding of fire from arcs, naturally occurring at fuse-box, light- 
ning arrester, etc. 

4. The prevention of mechanical injury to the parts. 

5. The placing of the parts so as to be accessible for operation and inspec- 
tion, and yet out of the way of passengers. 



Preparation of the Car Body. 

The floor should be provided with a trap-door of such size as to allow as 
free access as possible to the motors. Particular attention is called to the 
advisability of having the bar across the car between the trap-doors remov- 
able, in order that the top of either motor can be thrown back. 

The roof should be provided with a trolley board which strengthens it, 
and protects in case the trolley is thrown off; it also deadens the noise. 
A firm support should be provided for the light clusters. Grooves should 
be cut for the leading wires in the roof molding, and also in two of the 
corner posts, one for the trolley wire, the other for the ground wire of the 
lighting circuit. 

On a closed car four 2-inch holes should be bored through the car floor 
under the seats, one as near each corner of the car as possible. 

On one side of the car, four f-inch holes should be bored in a line, and 4 
inches apart, to receive the taps from the cable to the leads of motor No. 1. 
The exact location of these holes depends on the type of motor used. The 
distance from the center of the axle to the center of this group of holes 
should be about two and one-half feet for G. E. motors. On the same side 
of the car, and in the same line, four other f-inch holes should be bored 
4 inches apart, to receive the taps from the cable to the resistance boxes. 
On the other side of the car three f-inch holes in a line and 4 inches apart 
should be bored to receive the taps from the cable to the leads of motor 
No. 2, and on same side of car and in the same line five other f-inch holes 
4 inches apart should be bored to receive the taps for the trolley, resistance, 
and shunt for Motor No. 2. 

Reference should be made to diagram in order that each set of holes shall 
be on the proper side of the car, and at such a distance from side-sills as to 
be out of the way of wheel throw. 



746 ELECTRIC RAILWAYS. 

Measuring about 38 inches from the brake-staif and a suitable distance 
inside of the dash rail, an oval hole 5 in. x 2| in. should be cut in each plat- 
form to receive the cables. 

On an open car no holes need be bored for the floor wiring except those 
through the platform. 

Installing: Controllers. 

In the standard car equipment one controller is placed on each platform 
on the side opposite the brake handle, in such a position that the controller 
spindle and the brake-stall shall not be less than 36 inches, nor more than 
40 inches apart. The exact position depends somewhat on the location of 
the sills sustaining the platform. The feet of the controller are designed to 
allow a slight rocking with the spring of the dasher. Two one-half inch 
bolts secure the feet to the platform. An adjustable angle iron is furnished 
to be used in securing the controller to the dash-rail. A wire guard is also 
furnished, to be secured to the platform in such a position that the cables 
pass through it into the controller. A rubber gasket is furnished with each 
controller, to be placed between the wire guard and the platform,to exclude 
water. For dimensions of controller, see Figs. 104 and 105. 

Wiring. 

This work can be conveniently divided into two parts; namely, roof 
wiring- and floor wiring*. 

Roof -wiring* includes the running of the main circuit wire from the 
trolley through both main motor switches down the corner posts of the car 
to a suitable location for connecting to the lightning arrester and fuse box ; 
also wiring the lamp circuit complete, leaving an end to be attached to the 
ground. Whenever wires lie on the top of the roof, they need not be 
covered with canvas or moulding, except to exclude water where they 
pass through the roof. In such cases a strip of canvas the width of the 
moulding, painted with white lead, should be laid under the wire, and over 
this and the wire should be placed a piece of moulding extending far enough 
in either direction to exclude water. The moulding should be firmly 
screwed down and well painted. 

The above wiring should be done if possible while the cars are being 
built. 

Floor wiring* may be done after the car is completed without injuring 
the finish. 

IfEade np cables give far better protection to the wiring, and are 
easier to install than separate wires, and should be used in the floor wiring 
if possible. The simplest way of installing them on box cars seems to be as 
follows : 

After the car bodies are prepared according to the above instructions, the 
cables (one on each side of the car) should be run through holes in the plat- 
form, and the connections made to the motors and controllers. 

After making connection to the controllers, all slack should be pulled up 
inside of the car under the seats, and held in place, preferably against the 
side of the car, by canvas or leather straps. Motor taps should project 
through the sills for attachment to the flexible motor leads just far enough 
to permit easy connection, leaving as little chance as possible for vibration. 
No rubber tubing will be required on taps, as they all have a weather-proof, 
triple-braided cotton covering outside of the rubber insulation to prevent 
abrasion. All joints should be thoroughly soldered and well taped. The 
portions of the cables passing under the platforms should be supported by 
feather straps screwed to the floors or sills. Cables should never be bent 
at a sharp angle. The ground wire should run under the car floor rather 
than under the seats. 

On open cars all wires and cables must be run under the car, and should 
be well secured to the floor with cleats or straps. 

A good joint can be made by separating the strands of the tap-wire, and 



INSTALLATION OF ELECTRIC CAR MOTORS. 747 

wrapping the two parts in opposite directions around the main wire. Both 
Okonite and rubber tape are furnished. It is desirable that Okonite should 
be used first and rubber tape put over it, as the latter will not loosen and 
unwrap as Okonite will. All openings in the hose should be sewed up as 
tightly as possible around the wires. 

Separate wires can be installed if necessary, observing the following 
directions : ' 

The floor wires on box cars should be placed under the seats as much as 
possible. In the few places where it is necessary for wires to cross, wood 
should intervene in preference to a piece of rubber tubing or loop in the 
air. This rubber tubing is not necessary where wire is cleated under the 
floor (as on open cars), if it does not pass over iron work, or is not ex- 
posed to mud and water. Where so exposed, it should be covered with 
moulding, but where moulding is used it should be carefully painted inside 
and out with good insulating compound to exclude water. The wire passing 
to the fuse box should be looped downward to prevent water running along 
the wire and into the box. Care should be taken to avoid metal work about 
the car in running the wires, and that nails or screws are not driven into 
the insulation. 

In general it is not desirable to use metallic staples and cleats for car- 
wiring, except about the roof, or inside the car. Where wires are subject 
to vibration, as between the car bodies and motors, flexible cable must al- 
ways be used. A certain amount of slack should be left in the leads from 
the motor to the car body, depending on their length. On cars with swivel- 
ing trucks a greater amount of slack is necessary. As slack gives greater 
opportunity for abrasion, care should be taken to leave only what is abso- 
lutely necessary. 

Operation and Care of Controller. 

When starting, regulate the movement of the handle from point to point 
so as to secure a smooth acceleration of the car. 

Do not ran between points. 

The resistance points 1st, 2d, 3d, 6th, and 7th, are intended only for the 
purpose of giving a smooth acceleration, and should not be used contin- 
uously. 

For continuous running, use the 4th, 5th, 8th, and 9th points, which are 
shown by the longest bars on the dial. 

When using the motor cut-out switches be sure that they are thrown up 
as far up as they will go. 

In case the trolley is off and the hand-brakes do not hold the car, an 
emergency stop may be accomplished by reversing the motors, and turning 
the power-handle to the full speed, or next to full speed point. 

To examine the controller, which should be done regularly, open the 
cover, remove the bolt with wrench attached, and swing back the pole-piece 
of the magnet. 

The contact surfaces and fingers should be kept smooth, and occasionally 
treated with a small amount of vaseline to prevent cutting. 

All bearings should be regularly oiled. 

A repellent compound, paraffine, rosin, and vaseline, equal parts by 
weight, placed in the water-caps of the power and reversing shaft, is an 
eflicient protection against water. 

Dirt must not be allowed to collect inside of the controller. 



Diagrams of Car Wiring*. 

In general car wiring is carried out in about the same manner for all 
styles and sizes of car, more particular description being given above. Wir- 
ing differs mainly in details, governed by the number, style and horsepower 
of motors used. 



748 



ELECTRIC RAILWAYS. 



Diagrams of standard wiring for two motors per car and for four motors 
per car follow in Figs. 98, 99, 100, 101. They are all from the G. E. Co. lists, as 
controllers made by that Company are almost universally used, although 
many of older design by other companies are still in the held. 



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WIRING DIAGRAM OF ELECTRIC CAR MOTORS. 749 




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ELECTRIC RAILWAYS. 




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WIRING DIAGRAM OF ELECTRIC CAR MOTORS. 751 







752 ELECTRIC RAILWAYS. 



EaUIPMEM LISTS. 

The following is a list of material required for the electrical equipment of 
one car fitted with two motors: 

QUANTITY. 

1 Trolley pole. 

1 Trolley base. 

2 Motor circuit switches. 
1 Lightning arrester. 

1 150 ampere magnetic cut-out (fuse-box). 

1 Resistance box. 

1 Resistance box. 

1 Core for kicking coil. 

2 Controllers (includes wire guard and gasket, supporting bracket, 

cap screws, and washers for fastening to dasher). 
1 Controlling handle. 

1 Reversing handle. 

One of each of these handles is always shipped with each pair of 
controllers unless specified to the contrary. 

No. 6 B. & S. strand wire (7-. 061 in.) for roof-wiring. 

100 or 150 ampere fuses. 

Two-way connectors, i-inch hole, No. 6. 

Brass corner cleats, T Vinch slot. 

Brass flat cleats, r Vmch slot. 

£-inch No. 4 R. H. brass wood screws for brass cleats. 

Wood cleats, J-inch slot. 

Wood cleats, f-inch slot. 

li-inch No. 8 R. H. blued wood screws for wood cleats. 

Solder. 

f-inch Okonite tape. 

1-inch adhesive tape. 

Material for set. of cables as follows: 

No. 6 B. & S. strand wire (7-. 064 inches), single braid. 

No. 6 B. & S. strand wire (7-. 064 inches), triple braid for taps. 

Brass marking- tags. 

1^-inch cotton hose. 

Rubber tape. 

Paragon tape. 

Solder. 

This material can be procured made into a "set of cables" with- 
out extra cost. 
Car-lighting equipment. 



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CONTROLLERS. 



753 



CONTROLLERS. 

Under this heading are included all that type of appliance used for starting 
and stopping the motors and controlling the speed of the same. As almost 
all the old forms of rheostat with different steps have been abandoned for 
the so-called series-parallel controller, it is not necessary to describe any 
other here, nor will any detailed description of those now in use be attempted. 

But one form is now in general use, viz., the magnetic blow-out type, made 
by the General Electric Company and used also by the Westinghouse Electric 
and Manufacturing Company. 

The principle of the magnetic blow-out type was first developed by Prof. 
Elihu Thomson, i.e., that an electric arc in a strong magnetic field is blown 
out of line and extinguished or cut in two. This fact is taken advantage of 
in the controller of the General Electric Company by using a strong electro- 
magnet to extinguish the arcs formed at the contact-points, when the circuits 
are broken. The construction is shown in the cut of series-parallel controller, 
Form K2, following. 

Controllers are now made in so many forms and varieties that it is im- 
possible to give more than a few of the combinations which are practically 
the same everywhere in the United States. 




Fig. 102. Series-Parallel Controller, Form K2. 
General Electric Company. 



Used also by the Westinghouse Electric and Manufacturing Company, 
and others. 



754 



ELECTRIC RAILWAYS. 



The General Electric Company manufactures controllers for all conditions 
of electric railway and power service. They are divided for convenience in 
designation into five general classes, each designated by an arbitrary letter. 

Type JB Controllers may be of either the series parallel or rheo- 
static type, but always include the necessary contacts and connections for 
operating electric brakes. 

Type K Controllers are of the series parallel type and include 
the feature of shunting or short circuiting one of the motors when changing 
from series to parallel connection. 

Type JL Controllers are also of the series parallel type, but 
completely open the power circuit when changing from series to parallel. 




Fig. 103. " R " Type of Rheostatic Controller. 



Type It Controllers are of the rheostatic type and are designed 
to control one or more motors by means of resistance only. 

The Type Iff Control System developed by the General 
Electric Company with particular reference to the operation of motor cars 
in trains, is also suitable for operation of large equipments, where the size 
and weight of a cylinder type controller are objectionable. 

This system of control consists essentially of a number of electrically 
operated switches called "contactors" that close the various power and 
motor circuits, and which are in turn controlled by small master controllers 
which are called upon to carry only the current for the operating coils of the 
contactors. The motors are reversed by electrically operated reversing 
switches also controlled by the master controller. Where equipments are 
operated together in trains, the control circuits are connected between 
adjacent cars by suitable couplers and the operation of the contactors and 
reversers on all the cars in the train are controlled simultaneously from any 
master controller on the train. 



CONTROLLERS. 



755 



Series Parallel Controllers. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


K-2 


Two 40 h.p. 
Motors. 


5 Series. 
4 Parallel. 


For motors using loop or shunted field only. 


K-4 


Four 30 h.p. 
Motors. 


5 Series. 
4 Parallel. 


For motors using loop or shunted field only. 


K-6 


Two 80 h.p. 
Motors or 
Four 40 h.p. 
Motors. 


6 Series. 
5 Parallel. 




K-10 


Two 40 h.p. 
Motors. 


5 Series. 
4 Parallel. 




K-ll 


Two 60 h.p. 
Motors. 


5 Series. 
4 Parallel. 


Similar to K-10 but has connecting wires 
and blow-out coil of larger capacity. 


K-12 


Four 30 h.p. 
Motors. 


5 Series. 
4 Parallel. 


Similar to K-ll but has reversing switch 
arranged for four motors. 


K-13 


Two 125 h.p. 
Motors. 


7 Series. 
6 Parallel. 




K-14 


Four 60 h.p. 
Motors. 


7 Series. 
6 Parallel. 




K-27 


Two 60 h.p. 

Motors. 


4 Series. 
4 Parallel. 


Similar to K-ll but is arranged for oper- 
ation on metallic circuit, having con- 
tacts for opening both sides of the circuit. 


K-29 


Four 40 h.p. 
Motors. 


6 Series. 
5 Parallel. 


Similar to K-6 but is arranged for operation 
on metallic circuit, having contacts for 
opening both sides of the circuit. 


K-31 


Four 30 h.p. 
Motors. 


4 Series. 
4 Parallel. 


Similar to K-27 except has reverse switch 
arranged for four motors. 


K-32 


Two 40 h.p. 
Motors. 


4 Series. 
4 Parallel. 


Similar to K-27 except has connecting wires 
and blow-out coil of smaller capacity. 


L-2 


Two 175 h.p- 

Motors. 


4 Series. 
4 Parallel. 




L-3 


Four 150 h.p. 
Motors. 


8 Series. 
7 Parallel. 




L-4 


Four 100 h.p. 
Motors. 


4 Series. 
4 Parallel. 


Similar to the L-2 but with additional 
reversing switch parts for four motors. 


L-7 


Four 200 h.p. 
Motors. 


9 Series. 
6 Parallel. 





Electric Brake Controllers. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


B-3 


Two 40 h.p. 
Motors. 


4 Series. 
4 Parallel. 
6 Brake. 


Superseded for general use by the B-13. 


B-7 


Two 100 h.p. 
Motors. 


6 Series. 

5 Parallel. 

6 Brake. 


Has separate brake handle. 


B-8 


Four 60 h.p. 
Motors. 


6 Series. 

5 Parallel. 

7 Brake. 


Has separate brake handle. 


B-13 


Two 40 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Supersedes the B-3 from which it differs in 
that the braking connections are such as 
to render the skidding of the car wheels 
practically impossible. 



ELECTRIC RAILWAYS. 



Electric Brake Controllers.— Continued. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


B-18 


Two 40 h.p. 
Motors. 


4 Series. 
4 Parallel. 
6 Brake. 


Similar to B-3 but arranged for rheostatic 
braking only. 


B-19 


Four 40 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Similar to B-8, having separate handles for 
power and brake. Supersedes B-6. 


B-23 


Two 60 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Similar to the B-13 but has connecting 
wires and blow-out coil of larger capac- 
ity. 


B-29 


Two 60 h.p. 
Motors. 


5 Series. 
4 Parallel. 
7 Brake. 


Similar to B-23 but has separate brake 
handle. 



Electric braking is made little use of owing to the fact that it adds con- 
siderably to the heating of the motors. The conditions are such that the 
motors are already over-taxed and the use of brake controllers necessitates 
an increase in the size of motor required. Air-brakes are in almost uni- 
versal use on the heavier cars owing to their smaller expense of installation. 

Rlieostatic Controllers. 



Title. 


Capacity. 


Controlling 
Points. 


Remarks. 


R-ll 


One 50 h.p. 
Motor. 


6 


For motors using shunted field for running 
points only. 


R-14 


Two 35 h.p. 
Motors. 


5 


Very short and specially adapted to mining 
locomotives. Motors connected perma- 
nently in parallel. 


R-15 


Two 80 h.p. 
Motors. 


6 


Motors connected permanently in parallel. 


R-16 


Four 40 h.p. 
Motors. 


5 


Similar to R-15 but has reversing switch 
arranged for four motors. Motors con- 
nected permanently in parallel. 


R-17 


One 50 h.p. 
Motor. 


6 




R-19 


Two 50 h.p. 

Motors. 


6 


Similar to R-17 but has reversing switch 
arranged for two motors. Motors con- 
nected permanently in parallel. 


R-22 


Two 50 h.p. 
Motors. 


5 


Similar to R-14 but has connecting wires 
and blow-out coil of larger capacity. 


R-29 


Four 25 h.p. 
Motors. 


6 


Similar to R-19 but has reversing switch 
arranged for four motors. Motors con- 
nected permanently in parallel. 


R-37 


Two 50 h.p. 

Motors. 


5 


Similar to R-22 but has extra contacts on 
the reversing switch for connecting the 
motors either in series or parallel. 


R-38 


Two 35 h.p. 
Motors. 


5 


Similar to R-37 but has connecting wires 
and blow-out coil of smaller capacity. 


R-48 


Four 75 h.p. 
Motors. 


8 




R-55 


Two 150 h.p. 
Motors. 


7 


Has series parallel reversing switch same as 
R-37. It is specially adapted to mining 
locomotive service. 



These controllers are used with single motor equipments or for loco- 
motive work where the speed is very low, as in yard shifting service. 



CONTROLLERS. 



757 



8 

ft 

►4 
& 

>> 


3 


HceNaowHt . . H-* . H»HH . H«*w|ceio|ao .... 
OOt> . . .00 . . »0 <N .O5i-i00 . . . . 

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3 


HIM H» ! ! ! «Nt | | Hoo r-lH '. H-^Hoo 

iO CO CO . . .CO . . 00 05 »0 M ■* . CO iCOift 

<<H rH MD <N <N rH rH rH Jh 




M l° . «... 

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OOI> . . .00 . . W N . 05 H 00 . . . . 
^H • , n<<N<M rH rl 


o 
tab 

H 




HSH-IHloOlOlW rllNH|O0HaO«>l»»4»HlM«H' ^ '. H^H-Hr-Jr-.*^ 

iONM^HfO^O5CDCON»O00C0 , "5 N ?D ^ 

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CO 

M 


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iObW^HCO^Oi©CONiOOOCO . iO N O ^ 
CO t^ <M <N rH rH 


8 

1 

M 


ciH<HMwN<in|ao HnHhHhHhHc^HhmHi HS * H^'-ihr-iprth 
OOOOW^HCONCOOOCONiClOOO) . ■**< CO *C T* 
CO ^ M (N H H 




^pHSi-llQOldoO HlC^HlaoHcei^aOtoloOHe*"!"* "U ! H^HHHh' H 

iONfO^HCO^O>CO?DN^OOOO . WJ N CO rt< 
CO ^ IN (N H H 


M 


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ft O »0 . O . , O O 00 O H . ^ o *0 *0' 

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\k 


CON(Nt)*HCO(NOO'*ON'00000 . ift l> CD «* 
CO rj( (N (N H H 


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3 


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CO Tjl (N (N H H 


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0000C0T}tHC0NC000tDNOC005 . tP CO *C "** 
CO Tj( CO (N H H 


I 


HtSHShwhc* ,^HN^w|ooieraoHe*eoH» "U ' h*Hh 4^*4-1 
«5NINtHHCOCOO>iO(ON"500CO . UJ N <0 ■* 

CO «* <N <N rH rH 


M 


HSHShoohn HNHNHoOMloOko|ooHNco|H* HS ; H^HrHHH^P 
^NW^HCOCOCJiOON^OOOO , iO N «D rj< 
CO 'J.NINHH 


















<MOQWfaOWWrJSCPui^aDt3>r^r*< 



758 



ELECTRIC RAILWAYS. 




|*o 




Fig. 104. Type K. 



Fig. 105. Type L. 




J D. j 



i r 
. i i 

H| I 



^^° 



Fig. 106. Type B. 




Type R. 



Diagrams for Dimensions of Controllers. 



CONTROLLERS. 



759 



o 

ft 
>> 


CO 


h N CO . . .05 . .cONiOOOOO^l^O^ . 
CM CM tH tH 


CM 
<M 
1 


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rH t> CM " ' 00 ' "tONiOOOOOiON©^ 
CM CM rH rH 


05 
1 


m K°|2hqoio|qo HNnlSlSKHSiolooHNeoHi HrnV^HSrlSHS | | 
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1 


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CD 

T 

P4 


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3 


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CO T* rH rH 


i 
P3 


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s 


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1 

pq 


rH|"#ifl|oo Hc^H^ojooHooiHlc^Hoofoh* co|aoH^Hoo ">h | 
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CO «tf CO <M CM CM rH 


05 
1 


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COO5COTHrHCOTj<O5Tj<»OiOiO00O5iOcOiOiO0000 
CO ^ CM CM CM CM 


00 

*? 

pq 


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OOOM^HCO^OOOCJuOOlOOCDOifO^ . . 

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CO 

T 

pq 


r-H»O|o0 HC^H^^OOHoOH^r-lloOCClrr «foOr-^H<» "^H \ ) 

0005^^rHC0«0O«0i-iCN>»O0505»OCNiOi0 . . 
CO tH CO <M CM CM rH 


pq 


i-Htcolso ! ! ! irH ; * eo|ooHooeoNi Hoodoo e^«N«ioiaoMN<MNi 
NhiO . . . O . .000iiO05NT)*N«0O0i00 

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i 

pq 


.qirHrHNiwloo * * * i-iH^ * * wjoo rHJoo nH* H<» fofco coH< mN< io|oo e^lao eol-* 
500^ . . .iO . ;NOOiC©HT)tNCO(OCiOOO 

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3 

pq 


HrHH|e0r1iH»O|e0 HN Hh °TH HrH wlaOMh* r^r^HrHr-NtHiH * " 

cOOOCO"^rHCO""*Oe00505i00500t005COTt< . . 

CO tH CO CM rH rH 








<JPQOQHlHOWr<rq^CrMr4D>^^^S 



760 



ELECTRIC RAILWAYS. 

MOTOR COMBINATIONS 



RES. MOTOR 1 MOTOR 2 




"2-mO— O— AW/J— O — WA-I— 

i-^Ql}— O— WW^-O w^J— 

-^QD- po— ^v^f -Q — w-l- 
X^- pO — ww-Jp o — wA-1— 
-L-Cnj ^-o — "w^p o — w^l— 

--Ml[} i T O n -W^|-<H|-WAjJ— 



RES. MOTOR 1 MOTOR 2 




^-Qtm — o — vwvJ— o — v/v/J— 

J= 3ru— o — Wj-o — w^i— 



-Efiffl- T-o — w^j -o — v*^— 
- nrb - j-o — v^( -o — wa-I — 
-^Jl- ro-Wr o — w^ — 
-L-QUhl- ro — v^-'i -o — vw-i— 



CONTROLLER 



RES. MOTOR 1 MOTOR 2 

__ rrm _ pO-JWW-, rO-V*V-L_ 

■^niHi^i^zi— l^Iv^wJ 

-HIIIH1o-a^mH-o^^ 
' l" rW. i-o-^^-il t-o-v*AN-. | 

~HIi]} TLo- v< ^3 i [ €5-w^-i~ 
-HIII} tl<>3|m^[ C<^^ 

17^ r-O-W^-,1 f-Q-W^-, I 



Fig. 108. 



SERIES L2 CONTROLLER MULTIPLE 



RES. MOTOR 1 MOTOR 2 
B — O — VW — O — W/>— 




g O — WW— O — WW— 




' OPEN 

CHANGES TO MULTIPLE 

8EE NEXT COLUMN 

Fig. 109. 






B K HUh 
HK>-Wtf- r 

jj rO-W-l 

B K HW-i 

g u o-w*- r 



r-O-W^-L. 






ELECTRIC MULTIPLE UNIT CONTROL. 761 



THE SFRAGUE GENERAL ELE( THK MULTIPLE 
OIT CONTROL. 

The multiple unit control is designed primarily for the operation of motor 
cars in trains. Motor cars and trail cars may be coupled in any combination 
and the whole operated as a unit from any controller on the train. The 
system may also be used to advantage on individual equipments and loco- 
motives. 

The control apparatus for each motor car may be considered as consisting 
essentially of a motor controller and a master controller. 

The former comprises a set of apparatus, — usually located underneath 
the car, — which handles directly the power circuits for the motors, con- 
necting them in series and parallel and commutating the starting resistance 
in series with them. This motor controller is operated electrically and its 
operation in establishing the desired motor connections is controlled by the 
motorman by means of the master controller. The latter is similar in con- 
struction to the ordinary cylinder controller and is handled in the same 
manner, but instead of effecting the motor combinations directly, it merely 
controls the operation of the motor controller. 

The latter consists of a number of electrically operated switches, or " con- 
tactors" which close and open the various motor and resistance circuits, 
anol an electrically operated "reverser" that connects the field and armature 
leads of the motors to give the desired direction of movement of the car. 
Both the contactors and reverser are operated by solenoids, the operating 
current for which is admitted to them by the master controller. 

In addition to the motor and master controllers, each motor and trail car 
is equipped with train cable consisting of nine or ten individually insulated 
conductors connected to corresponding contacts in coupler sockets located 
at each end of the cars. This train cable is connected identically on each 
motor car to the master-controller fingers, and the contactor and reverser 
operating coils ; and the train cable is made continuous throughout the train 
by couplers between the cars, connecting together corresponding terminals 
in the coupler sockets. 

All wires carrying current supplied directly from the master controller 
fprm the "control circuit;" those carrying current for the motors, form the 
"motor" or "power circuit." 

Inasmuch as the motor controller operating coils are connected to this 
control train line, it will be appreciated that energizing the proper wires by 
means of any master controller on the train, will simultaneously operate 
corresponding contactors on all the motor cars, and consequently establish 
similar motor connections on all cars. 

In case the "power" circuit is momentarily interrupted for any reason, 
the system of control provides for the immediate restoration of the motor 
and resistance connections, which were in effect immediately preceding such 
interruption. Should the motorman remove his hand from the operating 
handle of the master controller, the current will immediately be cut off from 
the entire train, thus diminishing the danger of accident in case the motorman 
should suddenly become incapacitated. The system must be supplied with 
a potential of at least 300 volts to insure successful operation. 

The approximate total weight of control equipments, exclusive of supports 
is as follows: 

Aggregate H.P. of Motors. Weight of Equipment in Pounds. 

125 1500 

250 2000 

400 3000 

500 4500 

800 5000 

The approximate weight of the apparatus for each trail car, which included 
tram cable, coupler sockets and connection boxes, is 100 pounds. 
; The position of the handle on that master controller which the motorman 
is operating always indicates the position of motor-control apparatus on all 
cars. The motor controller which handles all the heavy arcing is located 
underneath the car. 



762 



ELECTRIC RAILWAYS. 



Apparatus. 

Contactors. — The contactors are the means of cutting in and out the 
various resistance steps, of making and breaking the main circuit between 
trolley and motors and of changing from series to parallel connection. 

Each contactor consists of a movable arm carrying a renewable copper tip 
which makes contact with a similar fixed tip, and a coii for actuating this 
arm when supplied with current from the master controller. The contactor 



<Zor>n&c£./or->s of 
/''or- r*vo aOO H. /=> //totorj 




Cot//D/(?r 

JocA«ts 




Fig. 110. 

is so designed that the motor circuit is closed only when current is flowing 
through its operating coil; and gravity, assisted by the spring action of the 
finger, causes the arm to drop and open this circuit immediately, when the 
control circuit is interrupted. 

In order to save space and eliminate interconnections as much as possible, 
several contactors are mounted on the same base. The contactors should 
preferably be located under the car, and boxes are therefore supplied 
which facilitate installation, protect the contactors from brake-shoe dust 
and other foreign material, and provide the necessary insulation. 



Reverier. 

The general design of the reverser is somewhat similar to that of the 
ordinary cylindrical motor-reversing switch with the addition of electro- 
magnets for throwing it to either forward or reverse position. In general 
construction, the operating coils are similar to those used on the contactors, 
but in order to secure reliability of action the coil is given full line potential. 
The reverser is provided with small fingers for handling control-circuit 
connections and when it throws, the operating coil is disconnected from 
ground and is placed in series with a set of contactor coils, thus cutting the 



ELECTRIC MULTIPLE UNIT CONTROL. 



763 




^ b* 



764 



ELECTRIC R'AILWAYS. 



operating current down to a safe running value. These coils are protected 
by a fuse, which will open the circuit if the reverser fails to throw. If the 
position of the reverser does not correspond to the direction of movement 
indicated by the reverse handle on the master controller, the motors on that 
car cannot take current. While the motors are taking current the operating 
coil is energized, and the electrical circuits are interlocked to prevent possi- 
bility of throwing. * 



L 0/m€>03/ons of C-2S Cont rotter 
form A 



iOn// 




Fig. 112. Master Controller Sprague G. E. Multiple Unit System. 



Master Controller, — The master controller is considerably smaller 
than the ordinary street-car controller, but is similar in appearance and 
method of operation. Separate power and reverse handles are provided, as 
experience has led to the adoption of this arrangement in preference to 
providing for the movement of a single handle in opposite directions. 

An automatic, safety, open-circuiting device is provided, whereby, in case 
the motorman removes his hand from the master-controller handle, the 
control circuit will be automatically opened by means of auxiliary contacts 
in the controller, which are operated by a spring when the button in the 
handle is released. This device is entirely separate and distinct in its action 
from that of the main cylinder. Moving the reverse handle either forward 
or backward makes connections for throwing the reverser to either forward 
or backward position. The handle can be removed only in the intermediate 
or off position. As the power handle is mechanically locked against move- 



ELECTRIC MULTIPLE UNIT CONTROL. 



765 



ment when the reverse handle is removed, it is only necessary for the motor- 
man to carry this handle when leaving the car. 

When the master controller is thrown off, both line and ground connections 
are cut off from the operating coils of important contactors, and none of 
the wires in the train cable are alive. 

The current carried by the master controller is about 2.5 amperes for 
each equipment of 400 horse-power or less. 




Fig. 113. 



Details of Top of Master Controller Sprague G. E. Co., Multiple 

Unit System. 



Master Controller Switch. — A small enclosed switch with magnetic 
blow-out is used to cut off current from each master controller; and it is 
supplied with a small cartridge fuse enclosed in the same box. When this 
switch is open all current is cut off from that particular master controller 
which it protects. 

Bridge Connection. — A noteworthy feature of the control is 
the method of accomplishing the series-parallel connection of the motors. 
This is by the so-called "Bridge" method of connections, which are so 
arranged that the circuit through the motors is not opened during the tran- 
sition from series to parallel and substantially the full torque of both motors 
is preserved at all times, from the series to the full parallel connection. This 
connection does away with any serious falling off in the rate of acceleration 
which is sometimes noticed when the motor circuit is interrupted during 
transition from series to parallel in other methods of control. The " Bridge 
connection is therefore particularly adapted to high rates of acceleration 
which can thus be sustained throughout the accelerating period without 
causing discomfort to passengers. 



766 ELECTRIC RAILWAYS. 



7/7o-£,or- C/'rca/d; Com^/r-j<yt,/or-> or*" . 
sS'proyc/e- Senero/ £/ectr/c /77v/t,//=>/G Ury/^. Gr"tct$e <Zor-»tJ-0/ 

.Serves ^/'r-s-6. ^o/'rt-t. 



— 0-AV r LT L - r ir i - r LP- r U 1 — 

/>70't.0/-<S ■ 



r?/?eos-6oti. 
^~c/// Serves >? 



r -<7Hvv L -'-^r^^ 



?-w~© — L-ophpku^ir — 



i*~c/// 5er/<?5 ^ 



© -M^H--ap-ap-ap- r ir — ! 




t -CHtv — ap j ir- r ipkn — L c 
<? -avkd — - j in-ar ur LP^ir — Li 



r~<^// Par-a//ct/ 
/O 9 <3 g 



/O 9 <9 7> 

o «^vvHi)--^nWphrHr^^ r ' 

Fig. 114. 



WESTIXCWHOI'**: OIT SWITCH SYSTEMS OJF 
JJKITLTIPJLE <OMU<M 

The system of multiple unit control developed by Westinghouse Electric 
and Manufacturing Company employs a combination of electromagnetic 
and pneumatic devices to produce a method of controlling from a single 
point a single car or train of cars, all or part of which are equipped with 
motors. It is applicable alike to alternating and direct-current motors, 
and to double and quadruple equipments. It may be arranged for either 
automatic or non-automatic acceleration and for operation with or without 
a train bus line. 

The complete equipment comprises apparatus pertaining to the main 
control system, which operates the motors on each independent car; the 
auxiliary control system, which consists of the electric circuit which actuates 
and controls the various devices but is entirely separate and distinct from 
the main motor control system; and a number of safety devices and attach- 
ments which protect the apparatus and safeguard its operation. 

TI ain Control. — The active element of the main control system 
is made up of the following apparatus: 



WESTINGHOUSE MULTIPLE CONTROL. 767 

A group of unit switches which regulate the supply of current to the 
motors. 

A set of resistances or an auto-transformer which is used in connection 
with the unit-switch group to control the supply to the motor. 

A line switch which controls the main supply of current to the unit-switch 
group. 

A reverse switch which governs the direction of car movement. 
Auxiliary Control. — The auxiliary control system derives its 
operating energy from a storage battery which forms part of each car equip- 
ment, and actuates the main control through the intervention of compressed 
air drawn from the brake supply. It comprises the following apparatus: 
The master controller. 
The train line. 
The line relay switch. 
The series limit switch. 
The control cut-out switch. 
The auxiliary control regulates the operation of the main control by the 
action of the master controller which governs the circuits connecting the 
storage battery mains and the valve magnets which regulate the air supply 
to the switches of the main control system. By the admission of air to the 
operating cylinders of the switch group, the motors are connected in the 
desired combinations. 

ft witch Group. — The switch group consists of a number of powerful 
circuit-breakers mounted in a common frame and assembled with their 
air cylinders in such a manner that when a valve magnet is energized the 
air will be admitted to the cylinder, forcing the piston forward and closing 
the switch. 

The switch contacts consist of two heavy L-shaped pieces of hard-drawn 
copper which close the circuit first at the tip and then roll and slide on each 
other, finally resting at the heel under the full air pressure. The switches 
are opened by the action of powerful springs. As their normal position is 
open, any failure of the air supply or interruption of the circuit is accom- 
panied by the immediate opening of all switches. A magnetic blow-out 
assists in the breaking of he arc. 

Resistance or Auto-transformer. — The main control resist- 
ance consists of a suitable number of grids mounted in frames and so 
connected to the unit switches that they regulate the current flowing through 
the motors as the switch group advances through its cycle of operation. 

With a single-phase alternating-current railway equipment an auto- 
transformer may be used in place of a resistance to regulate the voltage 
supplied to the motors. 

.Line ft witch. — The line switch comprises a group of switches — 
one for each motor of a double equipment or each pair of a quadruple equip- 
ment — connected each in circuit with its motor and carrying the current 
of that circuit alone. Their construction is similar to that of the units 
forming the switch group, except that each has an independent magnetic 
circuit for the magnetic blow-out and is provided with an automatic trip 
which opens and renders inoperative the auxiliary control whenever the 
current in the blow-out coil becomes excessive, allowing all the switches 
of both the line switch and switch group to drop out. 

Reverse ft witch. — In the direct-current reverse, an insulating 
block carrying two sets of metal strips arranged to make contact with sta- 
tionary fingers is operated forward and back in a straight line motion by a 
pair of pneumatic pistons which form part of the auxiliary control. The 
operating cylinders are governed by magnet valves which are interlocked 
with those of the switch group in such a way that the reverse can be thrown 
only when the main control circuit is open. 

The reverse for alternating-current equipment is of the drum type. 
Main ftwitch and fuse. — As an additional safeguard a switch 
and fuse may be introduced in the main line to open the circuit in case the 
automatic overload trip should fail, or if a ground or short circuit should 
occur on any unprotected portion of the main control system. When it is 
open the connection between the third-rail shoes or trolley and the main 
control apparatus is broken. 

Master Controller. — The master controller consists of a mov- 
able drum and stationary contact fingers. The handle is brought to the 



768 



ELECTRIC RAILWAYS. 



central or "off" position by the action of a spring which is compressed by 
motion of the handle in either direction and is always returned to thio 
position when the operator releases the controller handle. When it is 
desired to arrest the operation of the car or train at intermediate points, 
the controller handle is simply moved off the contact, opening the circuit 
and preventing a further advance of the unit switches. 

Interlock Switches.— The interlock switches which form part of the 
auxiliary controisystem.consist of spring contact fingers sliding on segments 




-Section Pneumatic Unit Switch 

Fig. 115, 

and are electrically connected with the magnet valves in such a manner that 
the closing of one energizes the valve magnet of the switch next succeeding, 
producing an automatic progressive action which provides a uniform accel- 
eration with a practically constant motor current. 

Train Line. — The train line consists of seven small wires which 
extend through the entire train, together with the junction boxes, connector 
sockets and jumpers. It connects the several portions of the auxiliary 



WESTINGHOUSE MULTIPLE CONTROL. 769 

control system to the storage batteries by which the operating current is 
supplied. The potential of these circuits is about 14 volts. 

Electrical connection between cables of adjoining cars is formed by means 
of sockets permanently mounted on the ends of the cars and a jumper which 
consists of a pair of plugs connected by a short piece of cable. 

Motor Control Cut-out Switch.. — To cut any motor out of 
service a control cut-out switch is provided with each equipment. It con- 
sists of a wooden drum with copper segments which make contact with 
fingers arranged on either side and forming part of the auxiliary control. 

Series JLimit Switch. — Regulation of the motor current during 
acceleration is accomplished by a small switch in the auxiliary control 
circuit governing the progressive action of the unit switches, through the 
coil of which passes current of one motor, so that the switch is opened and 
the progressive action of the switch group arrested whenever the current 
exceeds a pre-determined limit. When the current again falls below this 
limit, the switch closes by gravity and the progressive action of the switch 
group is continued. 

liine Relay. — ■ To protect the motors from an abnormal rush of 
current in case the main line circuit is suddenly reestablished after inter- 
ruption, a line relay is introduced in the controlling system and arranged to 
open the unit switches in case of failure of the line supply, but is held closed 
unless the main current is interrupted. This action takes place on each 
car individually, so that if the current supply is interrupted on any car the 
switch group on that car will be cut out independently of all other cars in 
the train, and if the current supply is restored while the master controller 
is in a running position, the line relay will restore the battery connection of 
the control circuit and the switch group will then pass through its cycle 
under the control of the limit switch and again supply current to the motors. 

Storagre Batteries. — The current which operates the magnet 
valves of the control system is supplied by a storage battery in duplicate, 
each consisting of seven cells. The potential of this controlling current 
is about 14 volts. One battery is on charge by connection in series with 
the air compressor or the car lighting system while the other is in service. 

The batteries on each car are connected in common leads which are carried 
through the entire train as positive and negative of the train line. The 
batteries of the several cars are therefore connected in parallel, and the 
negative side is also connected to one side of the magnet valves on each car, 
making the demand on the batteries more or less local. 

l<ine Switch Cut-out and Overload Trip Reset. — Two 
small knife switches located within easy reach of the operator are so 
connected that when the first is open the line switches throughout the train 
cannot be closed, so that no current can be taken from the line, but the 
switch group may be operated through its cycle for the purpose of test or to 
"buck" the motors and effect a sudden stop in an emergency. 

The second or overload trip reset switch is normally held open by a spring. 
When it is closed, with the master controller in the "off," or "semi-off, ' 
or coasting position, any trip that may be open will be reset. 

Bus Line. — That the current supply to every car maybe continuous, 
even though the trolley or third-rail shoes of any car be not in contact with 
the feeding circuit, a bus line is sometimes used throughout the train, con- 
nected from car to car by jumpers, plugs and sockets. 

Some of the Advantages Claimed. 

A control power wholly independent of the line power and voltage. 

Safety secured by the impossibility of short circuits, the line power control 
being local to each car. 

Absence of trouble with control circuit contacts. 

Low potential train line, practically eliminating train line trouble and 
short circuits of the control system. 

Great power at the switch contacts, made available by the use of com- 
pressed air, which secures greater carrying capacity and permits the use of 
powerful springs which insure operation of the switches under all conditions. 

Effective circuit-breaking devices with powerful magnetic blow-outs. 

Absolute independence in the regulation of the current input of each car. 

A simple motor cut-out switch. 

Automatic return of the main control to the "off" position if the current 



770 



ELECTRIC RAILWAYS. 



supply of any or all cars fails, and automatic return to action when the 
current is restored. 

A main control which is not brought into action by the auxiliary control 
when current is cut off. 

A main control which may be operated when the power is off for the pur- 
pose of test or to stop the train in an emergency. 

APPROXIHATE Hill* OF REPRECIATIO^ ©1* 

ELECTRIC STIlEiyi RAILWAYS. 



Buildings 1 

Turbines 7 

Boilers 8 

Dynamos and Engines, 

belted plants ... 5 

Belts 25 

Large, slow-speed steam 

engines 4 

Large, slow-speed direct- 
driven plants ... 4 
Stationary transformers, 5 
Storage batteries in cen- 
tral stations .... 9 
Trolley line 4 



(Dawson.) 



to 



2< 

9 
10 

10 ' 
30 



11 



Feeder cables .... 3 to 5 % 
Lighting and current 

meters 8 

Cars 4 

Repair shop and test- 
room fittings ... 12 

Motors 5 

Rotary transformers . . 8 

Boilers and engines . . 6 

Spare parts 1 

Track work 7 

Bonding 6 

On remaining capital ex- 
penditure 4 



10' 



15" 
8" 
10 " 
10" 
2' 
13' 
10' 

6" 



If interest rate is 5 per cent, and plant has to be renewed at the end of 20 
years, 3 per cent of original outlay must be reserved annually to provide for 
renewal. 

DEPRECIATIOI OJF STREET RAILWAY »!■ 
CHI^ERY A1¥I> E-aUIPUIEIVT. 

Rates Stated toy Chicag-o City Railway in u Street Railway 
Journal," Dec, l&OS. 

Engines, 8 per cent ; Boilers, 8 per cent ; Gene- 
rators, 3 per cent ; Buildings, 5 per cent. 

Cable machinery, 10 per cent ; Cables, 175 per cent. 

Rails, 5.5 per cent ; Ties, 7 per cent. 

Granite, 5 per cent ; Cedar blocks, 16 per cent ; 
Brick, 7 per cent ; Asphalt, 7 per cent ; Macadam, 
6 per cent. 

Car bodies, 7 per cent ; Trucks, 8 per cent. 

Armatures, 33 per cent ; Fields, 12 per cent ; Gear 
cases, 20 per cent ; Controllers, 4 per cent ; Com- 
mutators, 33 per cent. 

Wiring and other electrical equipment, 8 percent. 

Iron poles, 4 per cent ; "Wood poles, 8 per cent ; In- 
sulation, 12 per cent ; Trolley-wire, 5 per cent ; 
Trolley insulation, 7 per cent ; Bonding, 8 per 
cent. 
All based upon renewals and per cent of wear. 

CAR MEATlirO RY ELECTRICITY. 

Test on Atlantic Avenue Railway, Rrooklrn. 



Power-Station. 

Cable Jflachinery 

Roadbed. 
Paving*. 



Cars, 
Rolling* Stock 



Line Equipment. 



Cars. 


Temperature F. 


Watts 


Doors. 


Windows. 


Contents, 
Cu. ft. 


Outside. 


Average 
in car. 


Consumed. 


2 


12 


850£ 


28 


55 


2295 


2 


12 


850£ 


7 


39 


2325 


2 


12 


808£ 


28 


49 


2180 


2 


12 


913£ 


35 


52 


2745 


4 


16 


1012 


7 


46 


3038 


4 


16 


1012 


28 


54 


3160 



TRACK RETURN CIRCUIT. 



771 



TRACK RETURN CIRCUIT. 

It goes without saying that the return circuit, however made, whether 
through track alone or in connection with return feeders, should be the best 
possible under the circumstances. Few of the older roads still retain the 
bonds and returns formerly considered ample and good enough. 

Electrolysis and loss of power have compelled many companies to replace 
bonds and return circuits by much better types. The British Board of Trade 
paid especial attention to the return circuit in the rules gotten out by them 
(see page 781), and many American railroads would have been much in 
pocket to-day if such rules had been promulgated in the United States at 
the beginning of the trolley development. 

With few exceptions the practice of engineers has been to connect the rail 
joints by bonds, both rails of a track together at intervals, and both tracks 
of a double-track road together. To this has sometimes been added track 
return wires laid between the rails, and in other cases return feeders from 
sections of track have been run to the power house on pole lines or in ducts 
underground. 

The writer favors the full connection return with frequent insulated over- 
head return feeders where there may be danger from electrolysis of water 
and gas pipes ; in fact, ample return circuit has been proved time and again 
to be the only preventive of that trouble. 

On elevated railways where the structure is used for the return, the ends 
of abutting longitudinal girders are likewise bonded together at the expan- 
sion joints. Tests have shown that the riveted joints, where well riveted, 
have a conductivity nearly equal to that of the girder itself, hence it is not 
necessary to bond them. The return circuit of the New York Subway is 
designed for an extreme drop of five volts. 

Careful and continuous attention should be given to bonds from the 
moment cars are started on a line. 





SINGLE TRACK TURNOUT 



DOUBLE TRACK TURNOUT 



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CROSSING OF TWO ELECTRIC ROADS CROSSING OP ELECTRIC AND STEAM RQAD$ 

Fig. 116. Showing Cable Connections for Bonding Around " Special Work." 

Dr. Bell gives the following ratios of track return circuit to overhead 
system as being average conditions. 

Let R\ = resistance of track return circuit, and 

R = resistance of overhead system. 



Then 

R x = . 1 to . 2R. 
R x = . 2 to . 3R. 
R t = . 4 to . QR. 
R t = .2 to .3R. 
R t = .3 to .7R. 
R t = .7 to I. OR. 



Exceedingly good track and very light load. 
Good track and moderate load. 
Fair track, moderate load. 
Exceptional track and large system. 
Good track, large system. 
Poor track, large system. 



772 



ELECTRIC RAILWAYS. 



In exceptional cases track resistance may exceed that of overhead system. 
It is sometimes assumed that R ± = .25R, but this is rather better than 
usual. 

Under ordinary conditions R x = . 4R is nearer correct. 

If formula for copper circuit = cm. = ^ — : then for R t = . 4R, the 

constant 11 should be increased to between 14 and 15 in order that copper 
drop may bear correct proportion to that of the ground return. 

Type of lloiulv 

(By F. R. Slater.) 

Bonds are divided into two general classes. (1) those which are fastened 
to the surface of the rail or girder to be bonded, commonly called "soldered" 
bonds, and (2) those having terminals with a shank which is expanded into 
a hole in the rail or girder to be bonded, commonly called "riveted" bonds. 
In both classes that portion which is attached to the rail is called the terminal, 
the remainder the body of the bond. 

Soldered Bonds. — These are formed in various ways but in 
general by a series of thin strips of annealed copper bent in the form of an 




~w 



i°a m 



Fig. 117. Soldered Bond. Fig. 118. Bond Attached to Base of 

Rail by Soldering only. 

arch for the greatest degree of flexibility, with a pair of feet or terminals 
to provide contact surface. The strips of each foot are soldered or welded 
together, making a solid terminal, while the intermediate strips of the arch 
are free and unattached to each other so that they can readily take up vibra- 
tions. Figs. Ill and 112 illustrate this type. 

Shawmut Soldered Bond. — This bond is constructed of copper 
laminations .023 inch thick, the ends separately tinned, clamped together 




Fig. 119. Soldered Bond Applied to Head of Rail. 




Fig. 120. Soldered Bond Applied inside of Angle Bar. 



TYPE OF BONDS. 



773 



X 



and dipped, then covered with a tinned wrapper, thus insuring perfect union 
when heated, and the form of construction 
assuming a great degree of flexibility. 

In applying soldered bonds too much care 
cannot be exercised. The rail must be cleaned 
perfectly at the point of application and then 
tinned. The bond is then clamped in position 
and heat applied to both feet at once by 
means of a double burner gasolene torch, the 
solder being applied with zinc chloride flux. 

Bonds can be applied to the ball, web, or 
base of a rail, and each of the feet of the bond 
should be able to withstand a mechanical 
strain of two thousand pounds shearing stress, 

the electrical resistance not exceeding that of more than three feet of the 
rail to which it is applied. 



Fig. 121. Soldered Bond 
Applied to Base of Rail. 



Q 




Fig. 



122. Soldered Bond Applied 
to Head of Rail. 



Fig. 123. Soldered Bond Applied 
to Flange of Rail. 



Figure 124 shows the result of tests made on three sizes of soldered bonds 
250,000 cm., 370,000 cm., and 640,000 cm., to determine at what current 
the bond would melt off. The rise in temperature at the terminals and 
center of the bond is given. The 640,000 cm. bond melted off at 5,500 
amperes, melting both at the terminal and at the arched portion. The 
great difference in the heating of the two terminals of the 370,000 cm. was 
due to the imperfect soldering of one of them. 



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TEMP$— °C. 
Fig. 124. 



774 



ELECTRIC RAILWAYS. 



Riveted Bonds. — These are formed of a length of wire or cable 
having a copper terminal pressed or welded to its ends. Solid wire bonds 
of this type break easily from track vibration if short, and are used most 
largely for connecting around special work. This type of bond is sub- 
divided into several styles, according to the way the shank of the terminal 
is fastened into the hole in the rail. 

1. Bolt Expanded Terminal. — In this one the shank of the 
terminal is made with a hole through its center. Through this hole is 
passed a steel bolt which is threaded on one end and has a beveled shoulder 




Fig. 125. 

on the other. After the shank is fitted into the hole, it is expanded by pull- 
ing the bolt through the terminal by means of a nut, the tapered shoulder 
expanding the shank into the hole. This is shown in Fig. 125. 

£. Pin Expanded Terminal. — In this type the terminal is 
made with a hole through the center of the shank which is fitted into the 
hole it is to occupy and a beveled steel pin is driven through its center, 
expanding the shank to a tight fit. This is shown in Fig. 126. 





Fig. 126. 



Fig. 127. 



These two types are used principally for bonding the channel rails of the 
conduit system of electric railways. 

In both types the shank of the terminal should practically fit the hole 
before the pin or bolt is driven in. 

3. IKachine Hiveted Terminals. — In this type the shank 
of the terminal is made solid and is compressed into the hole by means of 
mechanical or hydraulic pressure (Fig. 127). 

Terminals of bonds should never be riveted by hammer as the shank is 





Fig. 128. Poorly Riveted Terminal. Fig. 129. Well Riveted Terminal. 



not properly expanded into the hole (Fig. 128). An imperfect contact 
increases the resistance besides making the bond liable to further deteriora- 
tion by reason of the accumulation of moisture between the shank and the 
hole. By means of the compressor the back of the terminal is first held 
securely against the face of the rail, then the shank of the terminal is ex- 
panded, forcing the soft metal back toward the base, making a uniform 
contact throughout the thickness of the rail, filling the hole so completely as 



TYPE OP BONDS. 



775 



to fill even the tool marks of the drill, and moreover, greatly increases the 
area of contact between the bond and the rail on account of the button head 
caused by the compressor (Fig. 129). This contact surface is an essential 
feature, and the efficiency of the bond depends upon this connection being 
made in the best possible manner. 

Tests show that it takes twice the power to turn the compressed terminal 
in its hole that it does to turn the pin-driven terminal. As the only resist- 
ance against turning is the friction between the copper in the terminal and 
the sides of the hole, the compressed terminal must have much the superior 
contact. 






Fig. 130. 



Fig. 131. 



Fig. 132. 



Figures 130 and 132 show respectively the double-screw and hydraulic 
compressors which have been successfully used on bonds in the web of the 
rail, and Fig. 131 shows a hydraulic compressor used successfully for putting 
bonds in the base of the rail. 

The requirements for a good bond are: 

1. Terminal should be made as an integral part of the stranded or body 
portion, in such a manner as to form practically a molecular union and 
thereby introduce a minimum resistance between the two. 

2. Its terminal should be so proportioned as to have contact surface with 
the rail sufficient to carry the same amount of current as the body portion of 
the bond. 

3. Its body portion should be so constructed as to possess sufficient flex- 
ibility to withstand all vibrations to which it may be subjected, such as 





Fig. 133. 



Fig. 134. 



hammer blows, of passing car wheels on the track, and expansion and con- 
traction of the rails due to temperature variations. 

4. A method cf applying the bond which will insure the permanency of 
the contact with the steel and reduce depreciation to a minimum. 

In all cases it is desirable to have the bonds as little exposed as possible 
both for appearances, and to prevent their being stolen. This is particu- 
larly true of those in the return circuit. Bonds should also be made as short 
as possible to make their cost a minimum. For these reasons it is highly 



776 



ELECTRIC RAILWAYS. 



desirable that the bonds be placed under the splice plates whenever possible. 
In new installations standard splice plates are now procurable which have 
ample space between their inner surfaces and the rail to allow for the bonds, 
and in changing over old installations the saving in the initial t cost of the 
bonds and the saving from loss by theft will go far towards paying for new 
splice plates. 

With the idea of placing the bonds under the splice plates, manufacturers 
have designed them in suitable shapes, either by flattening the strands, 




Fig. 135. 

or the use of flat wires in the strands. Figures 133 and 134 show girder 
rails with bonds under the splice plates, and Fig. 135 shows a standard "T" 
rail similarly bonded. 

Resistance of Bonds. — The total resistance of a bond is com- 
posed of three factors, the resistance of the copper in the bond, the resistance 
between the body of the bond and the terminal, and the contact resistance 
between the terminal and the rail. The following table gives the resistance of 
some of the more common sizes of bonds used: 



Size 

of 

Bond. 


Length of Bond. 


5" 


6" 


7" 


8" 


9" 


10" 



00 

000 

oooo 


.000047 
.000039 
.000033 
.000028 


.000056 
.000046 
.000038 
.000032 


.000064 
.000052 
.000043 
.000036 


.000072 
.000059 
.000048 
.000040 


.000081 
.000053 
.000053 
.000044 


.000089 
.000072 
.000059 
.000048 



For any given size of bond the only variable factor in its resistance with 
the length is the resistance of the copper in the bond, the other two factors 
remaining constant. Hence the resistance of different sizes can be plotted 
as is done in Fig. 136, using resistance in ohms and length in inches 
as ordinates. 

At least i inch extra length of short bonds should be allowed for extreme 
contraction of rails due to changes in temperature, and bonds shorter than 
9 inches are liable to excessive breakage due to vibration. 

The most common practice has been to have the bond holes drilled at the 
rolling mills. Hence, when it is desired to do the bonding, the holes are 
rusty and will need to be reamed out until clear and bright. The cost of 
having the holes drilled at the mill at the current price ($1.00 per ton of 
rail) usually amounts to about 20 cents per hole, and the reaming to about 
5 cents per hole — a total of 25 cents per hole, while if the holes are drilled 
just as the bonding is done, they will cost about 1\ cents each, including 
tools and supervision. Punched holes cost about 4 cents each. These 
costs will vary with conditions and rates of wages, the above being based 
on $2.00 for a day of eight hours. There is no material disadvantage in 
drilling the holes with oil. 



RESISTANCE OF BONDS. 



777 



RESISTANCE IN OHMS 

b 2 c> * & b 

1 § 8 S 8 

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RESISTANCE OF 
COPPER BONDS 

AT 75°F 








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Fig. 136. 



778 



ELECTRIC RAILWAYS. 



Care should be taken to see that the holes are free from all moisture, as 
its presence greatly reduces the efficiency of the bond, hence bonding should 
never be done during damp or wet weather. 

After the holes have been properly prepared the surface of the metal 
directly around the hole should be reamed so as to provide a bright, clean 
surface for the base of the terminal on the one side, and the button head, 
when riveted, on the other. If the shank of the terminal becomes oxidized 
or dirty it should be cleaned before being put into the rail. 

Third Hail .Bonding*. — The practice in third rail bonding has been 
to bond the rail slightly in excess of its conductivity, in order to make the 
rail nearly a uniform conductor. In order to accomplish this it has been 
necessary to bond the base of the rail as well as the web. Special malleable 
iron splice jplates are used which allow sufficient space for the bonds. Fig. 
137 shows the bonding of the third rail of the Interborough Rapid Transit 
Company (New York Subway). 

VFelded Joints. — On many systems where the rails are imbedded 
they are made practically continuous by the use of welded joints, and but 



3-^2 ,6% 



L-l)*/ Drilled Hole 







Punched Hole 




Fig. 137. 



little trouble is experienced by broken joints or bent rails. These are not 
practicable on third rails or track rails that are not embedded and thus 
exposed to all temperature changes. 

In the electrically welded system an iron plate is welded across the joint 
on each side of the rail web by means of heavy current of electricity applied 
by special low voltage machinery. 

The cast weld joint is simply a large lump of steel cast about the joint 
in a mould after the rail ends have been cleaned. 

Voynow Joint,— (Street Railway Journal.) The Voynow joint con- 
sists of what may be called two special channel bars which are riveted to 
the ends of the rail. These plates are not made to fit the fishing sec- 
tion of the rail; on the contrary, spaces are left under the head, tram 
and around the foot of the rail. The flat surfaces of both sides of the 
rails and of the joint bars having been previously cleaned by sand-blast, 
these spaces are filled with molten zinc, which enters into and fills out all the 
irregularities of the rolled surfaces, thus giving a continuous bearing through- 
out the whole length and width of the flanges of the plates. The adhesion 
of the molten zinc to the rails and plates, together with the body-bound 
rivets, holds the joint permanently tight, and at the same time prevents 
expansion, thus making rails continuous. As the rail ends and inside of the 
plates are cleaned to the metal by sand-blast, the joint is also of the best, 
electrically considered. 

Thermit Rail- Welding*. — The thermit process is a purely chemi- 
cal operation, based upon the fact that metallic aluminum, under proper 
conditions, will reduce many of the other metals from their compounds to 
their simple form; as, for instance, if aluminum is mixed with oxide of iron 
and the mixture is ignited, the aluminum will unite with the oxygen of the 
oxide, forming aluminum oxide (which is commercial corundum), leaving 
the iron free. As the process of reduction liberates a great amount of heat, 
the temperature of the mixture during the reaction rises rapidly (to about 
5000° F.), changing the iron to a molten low-carbon steel. Expressed in 



RESISTANCE OF TRACK RAILS. 



779 



chemical terms, the equation, according to which the reaction takes place, 
would toe Fe 2 3 + 2A1 = Al 2 3 + 2 Fe. This is the process utilized in 
welding rails. The oxide of iron is mixed with powdered aluminum in the 
right proportion, and introduced into a crucible lined with magnesia, or 
with material obtained from a previous fusion. In order to set off the con- 
tents of the crucible, a small quantity of ignition powder (barium peroxide 
and pulverized aluminum) is put in a small heap on top of the mixture, and 
is ignited by means of a match or red-hot iron rod. The reaction propagates 
itself quickly through the whole mixture, with the result that in a few seconds 
the whole charge is a mass of white-hot fluid material. The contents of the 
crucible have separated into two layers, the molten metal reduced by the 
aluminum being at the bottom and the molten aluminum oxide above it. 

In the application to rail-welding, a cone-shaped crucible, with magnesite 
lining, is mounted on a tripod over the joint to be welded, a properly pre- 
pared iron sand clay mould having been previously clamped around the joint. 
The conical crucible has a hole in the bottom, and before the operation a 
small iron rod or pin is placed in this hole with its end projecting several 
inches below the crucible. Above the head of the pin in the bottom of the 
crucible is first carefully fitted an asbestos washer, and on top of this is 
placed a solid circular metal washer to hold it in place. About 15 pounds or 
20 pounds of powdered aluminum and oxide iron are then poured into the 
crucible. This mixture is known as "Thermit," and is furnished properly 
mixed and ready for use in small bags by the manufactures. On top of the 
mixture is placed a quantity of ignition powder, about enough to cover a 
50-cent piece, When all is ready, a match is applied to the powder and a 
conical cover with a central opening is hastily placed on the crucible. In a 
few seconds the reaction commences, and within thirty seconds the contents 
of the crucible become a seething, boiling mass of molten metal. As soon 
as the reaction has reached its height, a man strikes the pin projecting from 
the bottom of the crucible with a rod or small shovel, driving the pin upward, 
thus freeing the hole and allowing the molten metal to flow down into the 
mould around the joint, depositing a mass of metal around the joint and 
welding the ends of the rails into one piece. 

Resistance of Track Rails. 

The resistance of the commercial steel track rails is about thirteen times 
that of copper. On this basis the following table of resistances of rails is 
computed. 



Weight 


Sectional 


Equivalent 


Resistance 


of 


Area 


Cir. Mils 


per Mile 


Rail. 


Sq. Inch. 


of Copper. 


Ohms. 


45 


4.4095 


431,883 


. 13074 


50 


4.8994 


479,884 


.11766 


55 


5.4874 


536,034 


. 10502 


60 


5.8794 


575,505 


.09806 


65 


6.3693 


623,887 


.09051 


70 


6.8592 


671,825 


.08404 


75 


7.3491 


719,380 


.07844 


80 


7.8392 


767,763 


.07354 


85 


8.3291 


814,873 


.06922 


90 


8.8190 


863,766 


.06537 


95 


9.3089 


911,767 


.06193 


100 


9.7988 


1,072,068 


.05883 



Area in cir. mils 



Equivalent cir. mils of copper 



1,000,000 X weight per yard 



10.2052 X 
Area in cir. mils t 
13 



7854 



780 



ELECTRIC RAILWAYS. 



EXPEHI^IEXTS IFOR DETERMIXATIOX OJF THE 

RELATIVE VAMJJE OJF RAJTJLS l\I) 

BONDED JOIVI*. 

(W. H. Cole.) 

Fifteen rails were used, giving three joints for each of the five different 
classes, and in making the tests and observations an average of the results 
for the three rails of its class was given. Micrometer calipers were used in 
measuring the wear of the rails each month, three different measurements 
were made at each place, and an average was calculated from these three 
measurements, viz.: 

A. At a point at or near the gage line. 

B. At a point in the center of the tread. 

C. At a point near the outside of the rail. 

The joints that were bonded were fished with standard fish plates, bolted 
with eight 1-inch bolts, screwed up tight; the rail ends butting each other 
were laid, fished and bonded in the maximum heat of the day, and immedi- 
ately covered and paved around them. 

No. 1. Three joints fished as above and bonded around the fish plates 
with standard Chicago bonds No. 00 B. & S. gage, two bonds to each joint. 

No. 2. Bonded with "Crown" concealed bonds, with two bonds of a 
section equal to two No. 00 copper B. & S. gage, and the fish plates bolted 
over them. 

No. 3. No. 2 plastic bonds, made by Harold P. Brown, and carefully 
installed according to instructions, by a man formerly experienced in this 
work. 

No. 4. Three joints welded by the Falk process. 

No. 5. Three joints welded by the Goldschmidt thermit process. 

The rails were laid continuously so the same cars passed over the same 
section containing the different types of joints. The subjoined tables 
give the results, from which the writer has arrived at the following con- 
clusions: 

That for electric street railways under average traffic conditions, rails 
should give a life of about forty years if the joints are made continuous, and 
are composed of 

Carbon 55 to .58 

Silicon 10 or under 

Phosphorus 08 or under 

Sulphur 06 or under 

Manganese 83 or under 



Ingredients of Rails Under Test. 



Carbon. 



Carbon 
Silicon . . 
Phosphorus 
Sulphur . 
Manganese , 

Iron . . , 



Soft. 



.284 
.061 
.105 
.085 
.784 

1.299 
98.701 



Medium. 



.572 
.235 
.052 

.078 
.981 



1.918 
98.082 



100.000 100.000 100.000 



Hard. 



.591 
.057 
.098 
.060 
.830 

1.636 
98.364 



Note. — Metalloids ignored. 



BOARD OF TRADE REGULATIONS. 



781 



The following would be the electrical efficiency and loss at the beginning 
and end of the first year: 



Class of Joint. 



Chicago bonds 

Crown bonds 

Plastic bonds 

Falk cast weld . . . . 
Goldschmidt thermit weld 



Electrical 
Per Cent 
Efficiency 
at Begin- 
ning of 
Year. 



89.51 

86.71 

89.72 

101.16 

101.14 



Electrical 

Efficiency 

at End 

of Year. 



74.43 
73.72 
77.84 
86.53 
100.39 



Per cent 
below 

Equal Sec- 
tion of 
Rail. 



29.57 
26.28 
22.16 
10.44 
100.39 + 



BOARD ©J? TRADE HEGlLATIO.\§. 

for Oreat Britain. 

Regulations prescribed by the Board of Trade under the provisions of 
Section of the Tramways Act, 189 — , for regulating the employ- 
ment of insulated returns, or of uninsulated metallic returns of low resist- 
ance; for preventing fusion or injurious electrolytic action of or on gas or 
water pipes, or other metallic pipes, structures, or substances; and for min- 
imizing, as far as is reasonably practicable, injurious interference with the 
electric wires, lines, and apparatus of parties other than the company and 
the currents therein, whether such lines do or do not use the earth as a 
return. 

Definitions. 

In the following regulations : 

The expression " energy" means electrical energy. 

The expression "generator" means the dynamo or dynamos or other 
electrical apparatus used for the generation of energy. 

The expression " motor " means any electric motor carried on a car and 
used for the conversion of energy. 

The expression " pipe " means any gas or water pipe, or other metallic 
pipe, structure, or substance. 

The expression " wire " means any wire apparatus used for telegraphic, 
telephonic, electrical signaling, or other similar purposes. 

The expression "current" means an electric current exceeding one- 
thousandth part of one ampere. 

The expression " the company " has the same meaning or meanings as in 
the Tramways Act, 189—. 

Regulations. 

1. A.ny dynamo used as a generator shall be of such pattern and con- 
struction as to be capable of producing a continuous current without appre- 
ciable pulsation. 

2. One of the two conductors used for transmitting energy from the gen- 
erator to the motors shall be in every case insulated from earth, and is 
hereinafter referred to as the M line"; the other may be insulated through- 
out, or may be insulated in such parts and to such extent as is provided in 
the following regulations, and is hereinafter referred to as the " return." 

3. Where any rails on which cars run, or any conductors laid between or 
within three feet of such rails, form any part of a return, such part may be 
uninsulated. All other returns or parts of a return shall be insulated, 
unless of such sectional area as will reduce the difference of potential be- 
tween the ends of the uninsulated portion of the return below the limit 
laid down in Regulation 7. 

4. When any uninsulated conductor laid between or within three feet of 
the rails forms any part of a return, it shall be electrically connected to 
the rails at distances apart not exceeding 100 feet, by means of copper 



782 ELECTRIC RAILWAYS. 

strips having a sectional area of at least one-sixteenth of a square inch, or 
by other means of equal conductivity. 

5. When any part of a return is uninsulated it shall be connected with 
the negative terminal of the generator, and in such case the negative termi- 
nal of the generator shall also be directly connected, through the current- 
indicator hereinafter mentioned, to two separate earth connections, which 
shall be placed not less than twenty yards apart. 

Provided that in place of such two earth connections the company may 
make one connection to a main for water supply of not less than three 
inches internal diameter, with the consent of the owner thereof, and of the 
person supplying the water ; and provided that where, from the nature of 
the soil or for other reasons, the company can show to the satisfaction of an 
inspecting officer of the Board of Trade that the earth connections herein 
specified cannot be constructed and maintained without undue expense, the 
provisions of this regulation shall not apply. 

The earth connections referred to in this regulation shall be constructed, 
laid, and maintained so as to secure electrical contact with the general 
mass of earth, and so that an electromotive force not exceeding four volts 
shall suffice to produce a current of at least two amperes from one earth 
connection to the other through the earth, and a test shall be made at least 
once in every month to ascertain whether this requirement is complied 
with. 

No portion of either earth connection shall be placed within six feet of 
any pipe, except a main for water supply of not less than three inches in- 
ternal diameter, which is metallically connected to the earth connections 
with the consents hereinbefore specified. 

6. When the return is partly or entirely uninsulated, the company shall, 
in the construction and maintenance of the tramway (a), so separate the 
uninsulated return from the general mass of earth, and from any pipe in 
the vicinity ; (b) so connect together the several lengths of the rails ; (c) 
adopt such means for reducing the difference produced by the current be- 
tween the potential of the uninsulated return at any one point and the po- 
tential of the uninsulated return at any other point ; and (d) so maintain 
the efficiency of the earth connections specified in the preceding regulations 
as to fulfill the following conditions, viz.: 

(1.) That the current passing from the earth connections through the in- 
dicator to the generator shall not at anytime exceed either two amperes 
•per mile of single tramway line, or 5 per cent of the total current output of 
the station. 

(2) That if at any time and at any place a test be made by connecting a 
galvanometer or other current indicator to the uninsulated return, and to 
any pipe in the vicinity, it shall always be possible to reverse the direction 
of any current indicated by interposing a battery of three Leclanche cells 
connected in series, if the direction of the current is from the return to the 
pipe, or by interposing one Leclanche cell, if the direction of the current is 
from the pipe to the return. 

In order to provide a continuous indication that the condition (1) is com- 
plied with, the company shall place in a conspicuous position a suitable, 
properly connected, and correctly marked current indicator, and shall keep 
it connected during the whole time that the line is charged. 

The owner of any such pipe may require the company to permit him at 
reasonable times and intervals to ascertain by test that the conditions 
specified in (2) are complied with as regards his pipe. 

7. When the return is partly or entirely uninsulated, a continuous record 
shall be kept by the company of the difference of potential during the work- 
ing of the tramway between the points of the uninsulated return furthest 
from and nearest to the generating station. If at any time such difference 
of potential exceeds the limit of seven volts, the company shall take imme- 
diate steps to reduce it below that limit. 

8. Every electrical connection with any pipe shall be so arranged as to 
admit of easy examination, and shall be tested by the company at least once 
in every three months. 

9. Every line and every insulated return or part of a return, except any 
feeder, shall be constructed in sections not exceeding one half of a mile in 
length, and means shall be provided for insulating each such section for 
purposes of testing. 



BOARD OF TRADE REGULATIONS. 783 

10. The insulation of the line and of the return when insulated, and of all 
feeders and other conductors, shall be so maintained that the leakage cur- 
rent shall not exceed one-hundredth of an ampere per mile of tramway. 
The leakage current shall be ascertained daily, before or after the hours of 
running, when the line is fully charged. If at any time it should be found 
that the leakage current exceeds one-half of an ampere per mile of tram- 
way, the leak shall be localized and removed as soon as practicable, and the 
running of the cars shall be stopped unless the leak is localized and removed 
within twenty-four hours. Provided, that where both line and return are 
placed within a conduit this regulation shall not apply. 

11. The insulation resistance of all continuously insulated cables used for 
lines, for insulated returns, for feeders, or for other purposes, and laid be- 
low the surface of the ground, shall not be permitted to fall below the 
equivalent of 10 megohms for a length of one mile. A test of the insulation 
resistance of all such cables shall be made at least once in each month. 

12. Where in any case in any part of the tramway the line is erected over- 
head and the return is laid on or under the ground, and where any wires 
have been erected or laid before the construction of the tramway, in the 
same or nearly the same direction as such part of the tramway, the com- 
pany shall, if required to do so by the owners of such wires or any of them, 
permit such owners to insert and maintain in the company's line one or 
more induction coils, or other apparatus approved by the company for the 
purpose of preventing disturbance by electric induction. In any case in 
which the company withhold their approval of any such apparatus, the 
owners may appeal to the Board of Trade, who may, if they think tit, dis- 
dispense with such approval. 

13. Any insulated return shall be placed parallel to, and at a distance not 
exceeding three feet from, the line, when the line and return are both 
erected overhead, or 18 inches when they are both laid underground. 

14. In the disposition, connections, and working of feeders, the company 
shall take all reasonable precautions to avoid injurious interference with 
any existing wires. 

15. The company shall so construct and maintain their systems as to 
secure good contact between the motors, and the line and return respec- 
tively. 

16. The company shall adopt the best means available to prevent the oc- 
currence of undue sparking at the rubbing or rolling contacts in any place, 
and in the construction and use of their generator and motors. 

17. In working the cars the current shall be varied as required by means 
of a rheostat containing at least twenty sections, or by some other equally 
efficient method of gradually varying resistance. 

18. Where the line or return or both are laid in a conduit, the following 
conditions shall be complied with in the construction and maintenance of 
such conduit : 

(a) The conduit shall be so constructed as to admit of easy examination of, 

and access to, the conductors contained therein, and their insulators 
and supports. 

(b) It shall be so constructed as to be readily cleared of accumulation of 

dust or other debris, and no such accumulation shall be permitted to 
remain. 

(c) It shall be laid to such falls, and so connected to sumps or other means 

of drainage as to automatically clear itself of water without danger 
of the water reaching the level of the conductors. 

(d) If the conduit is formed of metal, all separate lengths shall be so jointed 

as to secure efficient metallic continuity for the passage of electric 
currents. Where the rails are used to form any part of the return, 
they shall be electrically connected to the conduit by means of cop- 
per strips having a sectional area of at least one-sixteenth of a square 
inch, or other means of equal conductivity, at distances apart not ex- 
ceeding 100 feet. Where the return is wholly insulated and contained 
within the conduit, the latter shall be connected to earth at the gen- 
erating station through a high resistance galvanometer, suitable for 
the indication of any or partial contact of either the line or the return 
with the conduit. 



784 ELECTRIC RAILWAYS. 



(e) If the conduit is formed of any non-metallic material not being of high 
insulating quality and impervious to moisture throughout, and is 
placed within six feet of any pipe, a non-conducting screen shall be 
interposed between the conduit and the pipe, of such material and 
dimensions as shall provide that no current can pass between them 
without traversing at least six feet of earth; or the conduit itself shall 
in such case be lined with bitumen or other non-conducting damp- 
resisting material in all cases where it is placed within six feet of any 
pipe. 

(/) The leakage current shall be ascertained daily before or after the hours 
of running, when the line is fully charged, and if at any time it shall 
be found to exceed half an ampere per mile of tramway, the leak shall 
be localized and removed as soon as practicable, and the running of 
the cars shall be stopped unless the leak is localized and removed 
within 24 hours. 
19. The company shall, so far as may be applicable to their system of 

working, keep records as specified below.' These records shall, if and when 

required, be forwarded for the information of the Board of Trade. 

Daily Records. 

Number of cars running. 

Maximum working current. 

Maximum working pressure. 

Maximum current from earth connections (vide Regulation 6 (1) ). 

Leakage current (vide Regulation 10 and 18/.). 

Fall of potential in return (vide Regulation 7). 

Itloiitnly Records. 

Condition of earth connections (vide Regulation 5). 
Insulation resistance of insulated cables (vide Regulation 11). 

Quarterly Records. 

Conductance of joints to pipes (vide Regulation 8). 

Occasional Records. 

Any tests made under provisions of Regulation 6 (2). 
Localization and removal of leakage, stating time occupied. 
Particulars of any abnormal occurrence affecting the electric working of 
the tramway. 

Signed by order of the Board of Trade this day of 189 



Assistant Secretary, Board of Trade. 



• 
OVERHEAD CONDUCTING SYSTEM. 785 



CAlCrLATIl¥G THE OVERHEAD COIDUCTOG 
llSTtn Ol EJLFCTJR JLC RAILWAYS. 

Dr. Louis Bell gives the following steps as the best to be followed in 
entering upon the calculation of the conducting system of a trolley road: 

Extent of lines. 

Average load on each line. 

Center of distribution. 

Maximum loads. 

Trolley wire and track return. 

General feeding system. 

Reinforcement at special points. 

It must be said at once that experience T skill, and good judgment are far 
better than any amount of theory in laying out the conducting system of 
any road. 

Much depends upon the character of the load factor, i.e., the ratio of 
average to maximum out-put ; and this, varying from . 3 to . 6, can only be 
judged from a study of the particular locality, the nature of its industries 
and working people, the shape of the territory, and the nature of the sur- 
rounding country. 

Map out the track to scale, noting all distances carefully, and dot in 
any contemplated extensions, so that adequate provision may be made in 
the conducting system for them. Note all grades, giving their length, gra- 
dient, and direction. Divide the road into sections such as may best sug- 
gest themselves by reason of the local requirements, but such as will make 
the service under ordinary conditions fairly constant. 

The average load on each section will depend, of course, upon the 
number of cars, and the number of cars upon the traffic. This can only be 
arrived at by a comparison with similar localities already equipped with 
street railway, and even then considerable experience and keen judgment 
of the general nature of the towns are necessary in arriving at anything 
like a correct result. 

If the road has been correctly laid out as to sections, the load on each 
will be uniform and may be considered as concentrated at a point midway 
in each section. Now, if a street railway were to be laid down on a per- 
fectly level plain where the cost of real estate was the same at all points, 
and wires could be run directly to the points best suited; then it would only 
be necessary to locate the center of gravity of the entire system, and build 
the power station at that point, sending out feeders to the center of each 
section. Unfortunately for theory, such is never the case; and cost of real 
estate, availability of the same, convenience of fuel, water, and supplies 
will govern very largely the selection of a location for the power-house. 
Even when all the above points necessitate the placing of the power-house 
far from the center of gravity of a system, it may be possible to use such 
center as the distributing point for feeder systems, and even where this is 
not possible, it is well to keep in mind the center, and arrange the dis- 
tributing system as nearly as possible to fit it. 

All this relates, however, to preliminary determinations for the system 
as determined at the time, and in large systems will invariably be supple- 
mented by feeders, run to such points as the nature of the traffic demands. 
A basebail field newly located at some point on the line not known to the 
engineer previous to* the installation, will require reinforcement of that 
particular section; and often after a road has been running for some time, 
the entire location of traffic changes, due to change in facilities, and feeder 
systems then have to be changed to meet the new conditions, so that after 
all, location of the center of distribution depends largely on judgment. 

The maximum current will rise to four or five times the average where 
but one or two cars are in use; will easily be three times the average on 
roads of medium size, while on very large systems it may not be more than 
double the average. If speeds are maintained on heavy grades the maxi- 
mum is still further liable to increase. 

Another point to be considered in connection with maximum load is the 
location, not only of heavy grades, but of parks, ball-grounds, athletic fields, 
cemeteries, and other such places for large gatherings of people that are 
liable to call for heavy massing of cars, many of which must be started 



786 ELECTRIC RAILWAYS. 

practically at the same time, and for which extra feeder, and in some cases 
extra trolley capacity, must be provided. 

Having determined the average current per section of track, the maximum 
for the same, and the extraordinary maximum for ends, park locations, etc., 
as well as the distances, all data are obtained necessary for the determina- 
tion of sizes of feeders. 

The selection of the proper size of trolley wire is somewhat empirical, but 
the size may be governed by the amount of current that is to be carried. It 
is obvious that with given conditions the larger the trolley wire the fewer 
feeders will be necessary, and yet with few feeders the voltage is liable to 
vary considerably. In ordinary practice of to-day No. OB. &.S. and No. 00 
B. &. S. gauge, hard-drawn copper are the sizes mostly in use, the latter on 
those roads having heavier traffic or liable to massing of cars at certain 
localities. On suburban roads using two trolley wires in place of feeders, 
0000 B. & S. gauge will probably be best. 

Track return circuit has been treated fully in a previous chapter (see page 
771); and all that is needed to say here is, that some skill in judgment is 
necessary in settling on the value of the particular track return that may be 
under consideration, in order to determine the value of the constant to be 
used in the formula for computing the size of wire or overhead circuit. In 
ordinary good practice this value may be taken as 13, 14, or 15, according as 
the bonding and rail dimensions are of good type and large. 

It is quite obvious that the current-carrying capacity of the feeder must 
be taken into consideration, in spite of any determination of drop; and this 
can be found in the chapter on Conductors. Sizes of conductors are also 
governed to some extent by convenience in handling, and it is found that 
2,000,000 cm. is about the largest that can be safely handled for under- 
ground work, while anything larger than 500,000 cm. for overhead circuits 
is found to be difficult to handle. 

CONTINUOUS CURRENT fKEUERK LOAD I)KTE«. 
MIIATIOA T . 

The first step towards determining the load is to draw a train diagram 
from the proposed time-table or schedule of trains. Such a diagram, having 
as abscissae the length of the line and as ordinates the hour of the day, 
shows in a graphic form the course of every train and the number of trains 
on the line at any time. The stops may be omitted if they are very short 
compared to the runs, but in any case it is usual to show the course of 
each train by a straight line over each run, variations of speed being 
ignored unless of considerable duration and magnitude. An example of such 
a train diagram is given in Fig. 138, in which each train is indicated by a 
special kind of line in order to illustrate how it travels to and fro. The load 
at any time is estimated by counting how many train curves cut the line 
representing that particular time. Knowing the average amperes per train 
the total amperes are easily estimated for any time of day and may be 
plotted in the form of a load diagram. The average value of amperes for 
this purpose is obtained by plotting the curves of current for each run and 
adding the ampere hours of all these runs. The total ampere hours divided 
by the total number of hours occupied by the runs, is the average current 
taken by a train. 

The method of plotting the current curves is described on page 667. 

Economical Hesig*n of feeders. — The investment in a system 
of feeders may be expressed as an initial cost, or as an annual interest or 
percentage thereof. The value of the kilowatt-hours lost in the feeders is 
most conveniently expressed as an annual expense. The sum of these two 
annual items is the total annual expense of the feeders. If the cost of 
feeders be proportional to the amount of copper and if the energy loss be 
computed for exactly the same part of the system as the first cost expense, 
the total cost will be a minimum when the interest and energy items are 
equal. This is known as Kelvin's Law. Unfortunately the conditions 
which are necessary for the correct application of this rule are not usually 
met with in practice. The cost of conductors is seldom proportional to the 
amount of copper owing to the existence of such items as cost of manu- 
facture, installation and insulation. When, however, it is desired to find 
the most economical size of feeder to connect to a trolley wire or contact 



CONTINUOUS CURRENT FEEDERS. 



787 



1 1 


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ii 

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11 

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A.M. 



Train Diagram 
Fig. 138. 



788 



ELECTRIC RAILWAYS. 



rail, the total energy loss in the combined system is more important than 
the loss in the feeder wires alone, so that in this case it is advisable to 
make a minimum the sum of the energy loss in the whole system and the 
interest and depreciation on part of the system, and the most economical 
case must be worked out by trial. A table showing how to do this is given 
herewith and should be used in connection with that on "Distribution of 
Copper," which is given below. In the former table the system of most 
economical distribution (Case 3) of the latter table, is assumed to be used, 
but this is not necessary, and is not even applicable if there is no drain of 
current from the conductors. 



Volts 
drop 

to 
end 

of 
line 

V. 



Kw, 
hrs.lost 

per 
annum 

with 
R.M.S. 
current 
5.2 aV 



Annual 
cost of 
energy 

at n 
cents 

per 
kw.-hrs. 
$.052 

naV. 



Total 

C.M.- 

feet 

4 oL 2 

9 k * V 



Exist- 
ing 
con- 
ductors 
CM.- 
Ft. 



Extra 
C.M.- 

Ft. 
reg.'d 



Feet 
of 

C.M. 
cable 
req.'d 



Total 

cost 

of 

new 

cables 



Interest 
main- 
tenance 

and 
depreci- 
ation on 
cable at 
• - •% 



Total 
annual 
ex- 
pense, 
sum of 
third 
and last 
items. 



a = square root of the mean of the currents squared. 



Limiting- Potential Brop.- The total drop in the positive and 
negative feeders is regulated by several conditions some of which, unfor- 
tunately, may be contradictory. The line voltage must always be high 
enough to supply current for starting a car on an up-grade, and to keep the 
lights bright. For a multiple-unit system, the line voltage must be 
sufficient to operate the contactors and air compressors with certainty 
The General Electric Company's type M system of control should have 
at least 300 volts. The permissible drop is also influenced by considera- 
tions of economy, and in grounded feeders is often required not to exceed 
a certain limit fixed by law, this limit varying according to the locality. In 
England the maximum drop allowed in the grounded conductors is seven 
volts, whereas in most American cities no limit at all exists, it being only 
necessary for the railway company to take whatever precaution may be 
requisite to prevent electrolytic trouble. 

Two Classes of feeders. — Any direct current feeder system 
consists of two parts, the conductors which carry the current to the line 
and the line conductors (trolley wire) which serve as contact media to con- 
vey current to the cars. One set of conductors may be so designed as to 
fulfil these two functions, or the lines from the power station may be quite 
distinct from the contact rail or wire. In this latter case, the conductors 
from the power station carry the same current along their entire length, 
so that problems relating to drop, etc., may be treated by Ohm's Law. The 
contact conductors in either the first or second case mentioned above 
require somewhat different treatment owing to the fact that the current 
depends on the distribution of cars on the line. 



CONTINUOUS CURRENT FEEDERS. 



789 



Varioua arrangements of feeder and contact conductors are shown in 
Figs. 139, 140, 141, 142, and 143. Fig. 139 shows the simple ladder system 
in which the feeders and trolley wire are joined at intervals so as to form vir- 




TROLLEY WIRE 



TRACK RETURN 
CIRCUIT 



Fig. 139. 



tually a single conductor. In its best form the cross section of the feeder is 
tapered according to the rules given below. Fig. 140 shows a modification 
of the last scheme. In this case the trolley wire is cut into sections, so 
that while losing the extra conductivity of the continuous trolley, each section 



TROLLEY IN SECTIONS 
I) 



L" 



TRACK RET.UR8 
CIRCUIT 



Fig. 140. 

may be cut out in case of trouble without depriving the remainder of the 
system of current. Each section may be protected by a fuse and switch 
or a circuit breaker, but it is a disadvantage to have such apparatus scat- 
tered along the line. Fig. 141 shows a system where the current leaves the 




Fig. 141. 




TRACK RETC0B8 
CIRCUJT 



Fig. 142. 



790 



ELECTRIC RAILWAYS. 



station by several lines, thereby enabling a number of small circuit breakers 
to be used instead of the large one required by the other systems. It, how- 
ever, has the disadvantage of being uneconomical in copper, as the long lines 
carry very little of the load near the generators. The system shown in 
Fig. 142, is in many respects ideal from an operating standpoint, but it is 
very uneconomical in copper and energy. Each section of the trolley wire 



. Station Bus 



.Kail 



Fig. 143. 

or third rail may be controlled by a circuit breaker in the power station thus 
giving the operators complete control in case of overload, short-circuit, or 
accident of any kind. It is also quite advantageous to replace a large circuit 
breaker by a number of small ones where thousands of amperes have to 



SUB-FEEDER 



HEAVY GRADES 40 



TRACKRETURN 
CIRCUIT 



Fig. 144. 

be transmitted. A combination of the last two systems is where the sections 
are connected by switches which can be opened in case of accident, but 
are normally kept closed. Fig. 143 shows a system that is useful for nega- 
tive return conductors in cases where it is important to keep down the drop 



.1 



BALL PARKAT END OF LINE 



TRACK RETURN 
CIRCUIT 



Fig. 145. 



in the grounded rails. The numerous taps drain off the current in their 
neighborhood and so prevent the current in the rails being great at any 
point. The drop of potential in these insulated feeders will be considerable, 
but in the grounded ones it will be very little. This is in some cases more 
economical and certainly more simple than a "negative booster." 



CONTINUOUS CURRENT FEEDERS. 791 



caicciatiox ojf nini:\^iov^ ojf conductors. 

The problem of determination of the proper size of conductors to be 
used in distributing the current for an electric railway is somewhat com- 
plicated by the fact that the load is moving or changing its location all 
the time, and more so by the always changing condition of the resistance 
of the ground return, due to load, to track bending, condition of the earth 
return, and nearness of water and other underground pipes. Owing to this 
changing condition of the ground return part of the circuit it is necessary 
to assume some arbitrary value for it, in comparison with that of the over- 
head or insulated portion. The resistance of the ground return is seldom 
as high as that of the overhead part, nor is it often as good as .25 of that 
value ; these values change with the load and track conditions, and it is 
now most universal to use the factor 14 as a number which represents the 
value of both overhead and return conductor, in place of 10.8, the resistance 
per mil-foot of copper, and that value is therefore used in the formulae 
for calculating the sizes of overhead conductors, and has been found to 
produce good results in practice. 

Let d == distance from switchboard to end of conductor. 
CM = cir. mils area of the conductor. 
V = drop in volts at far end of line. 
/ = current. 
W = watts. 

E = volts at switchboard. 
10.8 = resistance of arc mil-foot of commercial hand drawn copper 

wire at 20° C or 68° F. 
14 = resistance factor, including track return. 
% = per cent expressed as a whole number, as 10 or 20. 

Then for plain feeders between switchboard or other source of supply 
and the attaching point to the system, 



CM — 


V 
1400 Xd XI 


CM = 

r = 
v = 


% XE 
1400 X^X watts 


% XE* 
14 X d x I 


CM 

% XE 



100 

The above formulae can be used for nearly all practical determinations of 
feeder and other conductor sizes, but must always assume the load to be 
concentrated at one point or center. For other formulae for calculation of 
the size of conductors see chapter on conductors. 

Distribution of Current. — It is usual to assume the drain of 
current from the contact conductor to be uniform, so that the current at 
any section is given by the ordinates of a straight line sloping down from the 
power station. The error in this assumption is decreased on account of the 
motion of the cars as this causes the load to act as if more distributed. 

Distribution of Copper — As the feeders carrying the same 
current along their entire length can be treated by the simple formulae shown 
above, it is only necessary to consider those along which there is a uniform 
drain of current. Four typical cases are shown in the table with their respec- 
tive formulae for circular mils, CM. ft., watts lost, and potential drop. The 
following abbreviations are used. 

Where conductors of iron or aluminum are used it is best to reduce them 
to equivalent sections of copper. 

The volts drop given by the formulae are from the far end of the line ; in 
order to get the drop from the power station, the values obtained by the 
formulae must be subtracted from V. 



792 



ELECTRIC RAILWAYS. 
Uniform Drain of Current. 



AMPS.jv 



CM, 




Fig. 146. Case 1. 
Conductor Uniform. 

10.8X1X1 



Watts lost = - IV. 



10.8 X Txd' 




Fig. 147 



Case 2. 



Conductor Uniformly Tapered. 



CM. = 
CM. ft. = 



10.8 X IXd 

V 

10.8 XlXP 

2 V 



Watts lost — -IV. 



Volts drop 



10.8 XlXd 
CM. 



CONTINUOUS CURRENT FEEDERS. 



793 



AMPS. 



CM, 




CM. — 

CM. ft. = 



Fig. 148. Case 3. 
Conductor Most Economically Tapered. 

2xl0.8X/xVlx^ 



3 V 
4 X 10.8 X / X I 2 
9 V 



Watts lost — - IV. 
5 




Fig. 149. Case 4. 

Conductor Uniform. Current X at Station and i at 
Distant End. 



CM. = 
CM. ft. = 



10.8x(/+i)* 

2 V 
10.8X(/-HW 2 

2 V 



Watts lost = 
Total drop, V— 



10.8xlX(I 2 +H + i 2 ) 

CM. X 3 
10.8x?X(/+i) 
CM. X 2 



794 



ELECTRIC RAILWAYS. 



In case 3, the formula for CM. gives the most economical distribution of 
copper to produce a certain drop V to the far end of the line. It is, of course, 
impossible to get this exact arrangement in practice as conductors of definite 
size must be used. The conductors are, therefore, arranged in steps of 



AMPS. 
CM. 











•s, 




' — ~* 




% ^ v v^ 




\ 



Fig. 150. 



decreasing area as shown in Fig. 150, each of which may be treated as an 
example of case 4. 

Miscellaneous formulae. — Watts lost, assuming uniform drain 
of current. 

Watts = amperes per foot X area of "Drop" curve in volt-feet. 

Potential drop in uniform conductor with any distribution of current. 

Volts = ohms per foot X area of current curve in ampere-feet. 

Most economical distribution of copper with any distribution of current. 

Cross section of copper proportional to * current. 

Note. — Do not connect trolley wire to feeder too close to power line or sub- 
stations, as if done this will cause frequent opening of circuit breakers. 



Drop and .Loss, etc., in Line between Two Substations of 
Unequal .Potential. Assumptions. 

One train moving between S.S. with constant speed and constant current. 

/ = current per train. 

L = distance between sub-stations. 

R = resistance of line per mile of track. 

E x = potential of S.S. No. 1. 

E 2 = potential of S.S. No. 2. 



S.S. 1. 



$= 



S.S. 2. 



Fig. 151. 



IMPEDANCE OF STEEL RAILS. 



795 



.Haximiim Drop at 


Train. 








Dmax j / 
Dmaz 2 \ 


IRL 

4 ~ 


E x - 
2 


E 2 + 




ill 


2 


- E 
2RL 






61 


L + E 

2 " 


1 -E 2 
2IR 




Averitgre Drop at Train. 








Dave i 1 
Dave 2 ) 


6 " 


E x - 
2 


E 2 




!;! 


/ + E t 

2 - 


— E2 
RL 




Averagre 


XiOss between S.S. 










_ PRL 


(Ei ~ 


- E 2 ) i 



(E x - E 2 )* 
4JRL 



RL 



IMPEDANCE OF STEEI HAII8 TO AI^TEIti^ATINO 
CU«IIJE]¥T. 

The impedance of iron or steel conductors to alternating currents is 
a complicated phenomenon which varies with the frequency of the current 
flowing with the area and the shape of the perimeter of the cross section and 
the permeability; and the permeability depends upon the current in the con- 
ductor; therefore statements of the impedance of iron or steel conductors 
to alternating currents convey little true meaning without a statement of 
all the conditions named above. Owing to the complexity of these con- 
ditions it is practically impossible to compute the values which must there- 
fore be determined by experiment. 

Following are tables showing the results of experiments upon steel track 
rails. 

Experimental Determination of Impedance of Steel Rails* 

(A. H. Armstrong, G. E. Co.) 

45-pound Rail. 

Measured cross section — 4 . 26 square inch. Perimeter — 15 . 875 inches. 
Direct current resistance of 180 feet — .00371 ohm. 



Cycle 


Amps. 


Volts 


Power 
Factor 


Imped- 
ance 


Watts 


Efif. Res. 


React. 


25 
25 
25 


223.2 
332 

438 


4.18 
6.75 

8.85 


.834 

.852 
.864 


.01875 

.0203 

.0202 


776 
1910 
3350 


.0156 

.01735 

.01747 


.0103 
.0106 
.0102 


40 
40 
40 


223.2 
332 

438 


5.37 

8.8 
11.47 


.826 
.876 
.889 


.0241 
.0265 
.0262 


990 
2560 
4450 


.0199 
.0233 
.0232 


.0136 
.0129 
.0120 


60 
60 
60 


223.2 
332 

438 


6.88 
11.06 
14.46 


.850 
.901 
.877 


.0308 
.0334 
.0330 


1308 
3305 
5550 


.0262 
.0300 
.0289 


.0162 
.0145 
.0158 



796 



ELECTRIC RAILWAYS. 



OO-pound rail. 

Measured cross section — 6 square inches. Perimeter — 18.75 inches. 
Direct current resistance of 180 feet — .00185 ohm. 



Cycles 


Amps. 


Volts 


Power 
Factor 


Imped- 
ance 


Watts 


Eff. Res. 


React. 


25 
25 
25 


296 
398 
622 


6.32 

8.64 

11.73 


.826 
.849 
.861 


.0213 
.0217 
.0189 


1545 
2920 
6280 


.01765 
.01841 
.01625 


.0120 

.01145 

.00961 


40 
40 
40 


296 
398 
622 


7.95 
10.98 
15.4 


.896 
.871 
.870 


.0268 
.0276 
.0248 


2110 
3800 
8340 


.0241 
.0240 
.02155 


.0119 

.01355 

.0122 


60 
60 
60 


296 
398 
622 


10.13 
13.74 
19.15 


.901 
.916 
.869 


.0343 
.0345 
.0308 


2700 

5010 

10350 


.0308 
.0317 
.0268 


.0149 
.0138 
.01525 



SO-pound rail. 

Measured cross section — 7.77 square inch. Perimeter — 21.5 inches. 
Direct current resistance of 180 feet — .002035 ohm. 



Cycles 


Amps. 


Volts 


Power 
Factor 


Imped- 
ance 


Watts 


Eff. Res. 


React. 


25 
25 
25 


392 
620 
820 


6.1 
10.01 
12.83 


.796 
.756 
.834 


.01555 

.0162 

.01565 


1905 
4700 
8760 


.0124 

.01225 

.0130 


.0094 
.0106 
.00863 


40 
40 
40 


392 
620 

820 


7.61 

12.98 
17.35 


.816 
.837 
.866 


.0194 
.0209 
.0212 


2440 

6720 

12300 


.0159 
.0175 
.0183 


.0112 

.001145 

.0106 


60 
60 
60 


392 
620 
820 


10.15 
17.03 
21.65 


.863 
.898 
.853 


.0259 
.0275 
.0264 


3430 

9460 

15150 


.0223 
.0246 
.0225 


.0131 
.0121 
.0138 



Experiment on Interworks Tracks of Westingrhouse 
E. & M. Co. 

"In order to determine the drop in voltage in a circuit composed of a 
trolley wire and a pair of track rails and to determine also the effect of the 
addition of a feeder, the following tests were 
made on the Westinghouse Interworks Rail- 
way, in March, 1905. The section of the road 
selected was 4000 feet long and consisted of 1200 
feet of double catenary construction and 2800 
feet of single catenary construction. The trolley 
wire was No. 000 and the track rails were 70 
pounds. The trolley wire was 24 feet above 
the track on the double catenary portion and 22 
feet on the single catenary. The messenger 
cable consisted of yVmch stranded steel cable. 
A No. 0000 feeder was located approximately 3 
feet above and 8 feet to the side of the trolley 
wire, as indicated in sketch (Fig. 152). 



-4000 <- 



D 



Fig. 152. 



EXPERIMENT ON INTERWORKS TRACKS. 



797 



With the end of the trolley wire grounded to the track and an alternating 
current of 25 cycles applied at the points B, C, the following results were 
obtained, with the aid of the No. 0000 feeder used as a voltmeter lead. 





Total 


Volts 


Volts 


Total Im- 


Power 


Amperes 


volts 
B - C 


A - B 


A - C 


pedance 
B - C 


Factor 


50 


23.5 


15.5 


8 


.47 


.646 


100 


46.2 






.465 


.637 


150 


68.5 


45 


22 


.456 


.639 


200 


89.6 


63.2 


29.5 


.448 


.63 


300 


138.4 


97 


44 


.448 


.62 








Average 


.457 


.634 



On direct current the average resistance of the total circuit B-C was 
.248 ohm; of the portion B-D, .219 ohm; and of the portion C-D, .0266 
ohm. 

It will be .seen from the above that the drop in voltage in this circuit, 
composed of trolley and track, was 45 . 7 volts per 100 amperes and that 
approximately two-thirds of this was due to the trolley wire and one-third 
due to the rails. 

In the second set of tests, current was supplied to the No. 0000 feeder 
and trolley wire in parallel and with 25 cycles alternating current, the 
following results were obtained. 



Total 
Amps. 


Amperes 
in trolley 


Amps, in 
feeder 


Voltage 


Imped- 
ance 


Power 
Factor 


100 
150 
200 


51.5 

72.7 
95.3 


48.5 

77.3 

104.7 


32.5 

48.4 
63.2 

Average 


.325 
.323 
.316 

.321 


.553 
.544 
.54 

.542 



On direct current the resistance of this circuit was . 1298. 

It will be seen from these results that the addition of the No. 0000 feeder, 
which reduced the resistance from .248 ohm to .1298 ohm, or nearly cut 
it in half, reduced the drop with alternating current from 45 . 7 volts per 
100 amperes to 32.1 volts per 100 amperes or only about one-third. 

This indicates that for single-phase railways the most economical use of 
copper is to place it in the trolley wire only and to so locate the feeding 
points that proper voltage will be obtained. 

In general, with a circuit consisting of No. 000 trolley and a pair of 70- 
pound rails, the drop in voltage with 25 cycle alternating current is approx- 
imately 60 volts per 100 amperes per mile, but only from 60 to 65 per cent 
of this voltage represents a loss of energy. 

With the alternating current system using a trolley and track return, there 
is an inductive drop in the trolley and rails, with an additional loss in the 
latter case due to eddy currents and hysteresis. Measurements made upon 
the Ballston line indicate an apparent trolley resistance of 1.3 times the 
ohmic resistance, and a rail resistance 6 . 55 times the ohmic resistance. 



798 



ELECTRIC RAILWAYS. 



Comparative A. C. and ■>. C. Resistance Trolley and 
Track, Per UEile of Circuit. 



^ 


p.c. 

Resistance 


A.C. Resist. 
25 Cycles 


v + - A.C. 


Two trolleys in series 

One trolley and double track .... 
Two trolleys and double track . . . 
Double track alone 


Ohms. 
.318 

.167 

.088 

.0174 


Ohms. 
.417 

.259 

.155 

.114 


1.31 
1.55 
1.76 
6.55 



The impedance of an electric railway conducting system consisting of a 
trolley wire overhead, placed in some sort of location above the two track 
rails, is a still further complication, and this impedance comprises the resist- 
ance and reactance of the trolley wire, and if of catenary construction, the 
messenger wires; the resistance and inductance of the rails; the inductance 
of the circuit bounded by the rails and the trolley wire, and the mutual 
inductance of the currents in the two rails. The calculation of this imped- 
ance is therefore hardly possible and in all cases its value must be deter- 
mined by experience. 



TESTS OE STREET RAILWAY CIRCUITS. 

The following tests are condensed from an article by A. B. Herrick in the 
Street Hallway Journal, April, 1899. 
The following instruments will be required : 

A barrel water rheostat to take say 100 amperes. 
A voltmeter reading to 600 volts. 
A voltmeter reading to 125 volts. 
An ammeter reading to say 150 amperes. 

A pole long enough to reach the trolley wire, with a wire running along it 
having a hook to make contact. 

Use one generator at the station, and have the attendant keep pressure 
constant. 



Test for Drop and Resistance in Overhead Lines and 
Returns. 

The car containing the above equipment of instruments is run to the end 
of the section of conductor which it is desired to test, where a line circuit- 
breaker divides the sections. 

The instruments are then connected as shown in Fig. 153. 

It is clear now that if the switch G be closed, current will flow through 
the rheostat and be measured by the ammeter. We now have the trolley 
and feeder B for a pressure wire back to the station, and the reading of 
voltmeter C therefore gives the drop between the station and the point A 
in the feeder and trolley carrying the load. Voltmeter D shows the drop 
across the rheostat ; and if the sum of readings C and D be deducted from th« 
station pressure, the difference will be the drop in the ground return. 



TESTS OF STREET RAILWAY CIRCUITS. 



799 




Fig. 163. 

The station pressure can be taken by changing the lead of voltmeter C 
down to F as shown by the dotted line. 

The drop on A and its resistance having been found, the trolley-pole can 
be swung around and the same data be determined for the circuit B. 

To Read the Ground Return Drop Directly. 

Open the station switch on that feeder that is being used as pressure wire, 
and ground the feeder to the ground bus through a fuse for safety. 

Connect the instruments as shown in the following cut ; then when the 
switch G is closed and current flows, the drop from A to F read on voltmeter 
C will be the drop in the ground return from F to X. 




Pig. 154. 



800 



ELECTRIC RAILWAYS. 



To Determine Drop at End of line. 

For use on double-track lines only, unless a pressure wire can be run to 
the end of line from the last line circuit-breaker. 

Break all cross connections from feeder to trolley-wire for one track, as 
at n ; connect this idle trolley to the next one back toward the station, as 
at C, then make the tests as in the two methods described above, connections 
being shown in the following cut. 




Fig. 155. 

To Determine the Condition of Track Bonding:, and the 

Division of Return Current tbroug-h Rails, Water 

or Ga§ Pipes, and Ground. 

The cut below shows the connections for this test as applied to a single 
track, or to one track of a double-track road. 

Ground the feeder A at the station, or rather connect it to the ground bus 
through a fuse. Then connect the track at C to A by the pole E through 
the ammeter M. The drop between points F and D will be the drop through 
the rail circuit between C and D, due to the current flowing. 

If connection be made to a hydrant, or other water connection, and to a 
gas-pipe, as at X, still retaining the rail connection at C, more current will 




Fig. 156. 



TESTING RAIL BONDS. 



801 



flow through ammeter M, due to providing the metallic return through A 
for the water-pipe, and the first reading of the ammeter M is to the second 
reading as the resistance of the water-pipe is to that of the rail return, and 
the current returning to the station will distribute itself between the two 
paths in proportion to the readings mentioned. If ammeter G be read at the 
same time, the difference between its reading and the sum of the other 
two readings will be the amount of current returning by other paths than 
the rail and water-pipe. If C is near the station it may be necessary to 
break the ground connection between rails and bus, so that all current may 
return over the metallic circuit A. 

To determine condition of bonds, move the contact C back towards D, and 
the decrease in drop as shown by the vm. will be very nearly proportional 
to the length of track, except where a bad or broken bond may be located, 
when the change will be sudden. 

XESTI\(» Hill ltO\B>*. 

It is not commercially practicable to measure the exact resistance of rail 
joints, as such resistance is small under ordinary circumstances, and all the 
conditions vary so much as to prevent accurate measurement being made. 
The resistance of rail joints is therefore measured in terms of length of the 
rail itself, and there are numerous instruments devised for the purpose, 
nearly all being based upon the principle of the wheatstone bridge, the 
resistance of the rail joint being balanced against a section of the rail, as in 
the following diagram. 





MILLI-VOLTMETER , 
CENTER-ZERO < Vl 0HM 



Fig. 157. Diagram of Method of Testing Rail Joints. 



A Weston or other reliable milli-voltmeter, with the zero point in the mid- 
dle of the scale, is the handiest instrument for making these tests. The 
points b and c are fixed usually at a distance of 12 inches apart, the point a 
is then moved along the rail until there is no deflection of the needle when 
both switches are closed. The resistance of the joint or the portion between 
the points b and c is to that of the length, x, inversely as the length of the 
former is to that of the latter, all being in terms of the length of rail, or, 
Let 



then, 



x = distance in inches between points a and c, 

y = distance between the points c and 6, 

v = resistance of joint in terms of length of rail, 



802 



ELECTRIC RAILWAYS. 



and if x — 36 inches and y = 12 inches, 
then 

36 

v = — = 3 times its length in rail. 

Another scheme for testing rail joints is pointed out by W. N. Walmsley 
in the M Electrical Engineer," December 23, 1897. 

In the following cut, the instrument is a specially designed, double milli- 
voltmeter, both pointers having the same axis, and indicating on the same 
scale. 



DOUBLE 
MILIVOLTMETER 




WAL'MSLEY'S RAIL, TESTER 



Fig. 158. 



The points ab are at a fixed distance d, the point c being movable along 
the rail. Points a and b are set on the rail astride the joint, as shown ; the 
point c is then moved along the rail until the pointers on the instrument 
coincide, indicating the same drop. Then the resistance of x is the same 
as dj in terms of the size of rail used. 

Harold P. Brown has devised an instrument for testing rail joints with 
little preparation. It consists of two specially shielded milli-voltmeters of 
the Weston Company's make, put up in a substantial wooden case, the top 
of which is made up in part of two folding legs which, when unfolded, cover 
six feet of rail. These legs form one length, which is divided by slots into 
two lengths, one of one foot, the other five feet long. The instrument is 
placed alongside the track in such position that the leg rests on the rail, and 
the joint to be tested is between the ends of the shorter branch or leg, while 
five feet of clear rail are included between the ends of the longer leg. 

The instrument terminals are connected to small horseshoe magnets, that 
fit into the slots in each leg, and when rested on the rail always make the 
same pressure of contact, the poles being amalgamated and coated with a 
special soft amalgam, called Edison Flexible Solder. 

With the five feet of rail as a shunt, the instrument will read to 1500 am- 
peres. 

There are several separate resistance coils and binding-posts supplied for 
different sizes of rail in common use, so that the dial of the milli-voltmeter 
needs but one scale. 

The second milli-voltmeter measures the drop around the one foot of 
joint, and has coils so arranged to permit of reading .15, 1.5, 15. volts. 

A reading of the current value is taken from the five feet of rail, and a 
simultaneous reading of the drop across the joint and one foot of rail is also 
made. The resistance of the latter is then found by ohm's law, 



B = 



E 



TESTING RAIL BONDS. 



803 




A B C 

Fig. 159. Brown's Rail-bond Testing Instrument. 
Street Railway Motor Vesting*. 

Barn test for efficiency : — 

Put a double-flange pulley on the car axle for the application of a prony 
brake, pour water inside the pulley to keep it cool. Use common platform 
scale, as shown in cut. 




Fig. 160. 

Then let D = distance from center of axle to point on scales in feet, 
measured horizontally. 
n — 3.1416, 

R ■=. revolutions per minute, 
E = voltage at motor, 
Iz=. amperes at motor, 
Tzz force applied to balance scales, in pounds. 



Then B. H. P. = 



2tt BR T 
33,000 



B. H. P. at 500 volts = 
EI 



[2,DRX^\T 



E J 



33,000 
=z E.H.P. supplied to motor. 
500 / 



746 



Efficiency of motor = 



: E.H.P. supplied to motor at 500 volts. 



B.H.P. 



X 



B.H.P. at 500 volts 



E.H.P. ~ E.H.P. at 500 volts 



Draw-bar Pull and Efficiency Test Without Removing 1 
motor from Car. 



Rig up lever as shown in cut, being sure the fulcrum A is strong enough 
to stand the pull. Posts, as shown, make good fulcrum ; have turn buckle 
F for taking up any weakness. 



804 



ELECTRIC RAILWAYS. 




Fig. 161. 

Let D = diameter of car wheel in feet. 

7T = 3.1416, 

T== force on scale in pounds, 
L == length of long arm of lever, 
L, ■=. length of short arm of lever, 
R = revolutions per minute. 
Place a jack-screw under each side of the car, and lift the body until there 
is only friction enough between wheels and rail to keep the speed of revolu- 
tions down to the normal rate. 
Then 



Draw-bar pull := T 



and 



V 



T-^-DnR 
B.H.P. : & 



33,000 

and the efficiency is the same as before, 
B.H.P. 



i.e. 



E.H.P. 



: efficiency. 



Mr. A. B. Herrick has devised a testing-board for street-railway repair 
shops that will greatly assist in making all inspection tests, and which is 
described in the " Street Railway Journal " for January, 1898, pages 11 
and 12. 

Testing 1 Drop in Railway Circuits. — For this test use can 
be made of any car that is in good order, and it should be carried out 
after the last car is in the barn, and the track is clear. Run the car over 
the line starting from the point nearest the power house, making the test 
at any points that may be selected. The following cut No. 162 shows the 
arrangement of instruments. 





Fig. 162. 



E = drop a to b without load, and in clear dry weather this should be 
same as at the switchboard. In wet weather or with poor insu- 
lation the drop without load may be considerable. 



FAULTS AND REMEDIES. 805 

Ei = drop a to 6 taken with the brakes set and the controller on the 
first notch. 
/ = amperes of current under conditions E\. 
E — E\ = e — drop in circuit due to current /. 

R = j — resistance of entire circuit of trolley wire; feeders, and rail 

returns. 
Ri = resistance of feeders and trolley wire as calculated from their 
known dimensions. 
R — Ri = resistance of the return circuit. 

FAULTS A XU REMEDIES. 

Car Will not Start: 

a. Turn on lamps ; if they burn, trolley and ground wires are all right 
and current is on line. 

b. If lights die down when controller is thrown on, trouble may be poor 
contact between rails and wheels, or car may be on '• dead " track. 

c. If car works all right with one controller, fault may be open circuit, or 
poor contact in the other. Throw current off at canopy, or pull down the 
trolley and examine the controller. 

d. See that both motor cut-outs are in place. 

e. Fuse may be blown ; throw canopy switch and replace. 

/. See that motor brushes are in place and intact, and make good contact. 

a. Car maybe standing on "dead" or dirty rail ; in either case connect 
wheels to next rail by wire. It is better to open canopy switch while con- 
necting wire to wheels, or a shock may be felt. 

h. Ice on trolley wheel or wire will prevent starting. 

Sparking* at Commutator Brushes: 

a. Brushes may be too loose ; tighten pressure spring. 

b. Brushes may be badly burned or broken,' and therefore make poor con- 
tact on the commutator. Replace brushes with new set, and sandpaper 
commutator surface smooth. 

c. Brushes may be welded to holder, and thus not work freely on commu- 
tator surface. 

d. Commutator may be badly worn and need renewing. 

e. Commutator may have a flat bar, or one projecting above the general 
surface ; commutator must then be turned true in lathe. 

/. Dirt or oil on commutator may produce sparking ; clean well. 

Flame at the commutator may be produced by : — 

a. Broken lead wire or coil, producing a greenish flame, and burning two 
bars usually diametrically opposite each other. If left too long the two 
bars will bebadly burned, as will also the insulation between. 

Temporary relief can be had by putting a juniper of solder or of small 
wire across the burned bar, connecting the two adjacent bars to each other ; 
one juniper is enough. 

b. A short-circuited field coil, or a field coil improperly connected, will 
produce flare at commutator. Short-circuited coil can be found by volt- 
meter test across terminals showing drop in coil. Wrong connection can be 
detected by pocket compass. 

Incandescent lamps sometimes burn out or break. Replace with 
new ones. If they do not burn when switch is on, 
a. Examine each for broken filament. 
6. Examine for poor contact in socket. 

c. Examine switch for poor contact or broken blades. 

d. Examine each part of circuit, switches, line, and sockets with magneto, 
which will locate opening. The wire may be broken at ground or trolley 
connections. 

Brakes fail ta Operate: 

In great emergency only, throw controller handle to off, reverse reversing- 
switch, and turn controller handle to first or second notch. 



806 



ELECTRIC RAILWAYS. 



In sliding down grades, or when there is time, proceed as follows : 

a. Throw controller handle to off point. 

b. Throw canopy switch off. 

c. Reverse reversing-switch. 

d. Throw controller handle around to last notch. Both methods are 
more or less strain on the motors, but the second is somewhat less so than 
the first. 

Grounds : Either on field or armature coils will nearly always blow 
fuse ; it can then be tested out. 

Bucking 1 : When running along smoothly, a car will sometimes com- 
mence jerky, bucking motions, and should be thoroughly examined at once. 
It may be due to a ground of field or armature that may short-circuit one or 
the other, either fully or intermittently. Injured motor may usually be 
located by smell of burning shellac, and can be cut out at the controller, 
•and the car run in with the good motor. 

Mud and water splashing on commutator will sometimes produce bucking, 
and often a piece of wire caught up from the track may do the same. 

Miscellaneous "Xote. 

Experiments show that four arresters per mile of trolley wire are plenty for 
safety. 

Green wooden poles should not be painted for at least a year after they 
are set, as the paint will peal off and not give good results. 

Loose ornamental joint caps frequently used on iron or steel poles collect 
moisture and rust out the pole. 



Wiring- Diagrams for JLightiiig; Circuits on Street Cars. 




trLH i^^^^ 



Head Light 



i 




Fig. 163. Diagram for two Circuits Fig. 164. Diagram of Wiring to 
Headlights, Platform Lights and permit use of 32-p. Headlight. 

Sign Lights Interchangeable. 



r X — pn rf==^ 

L/ • Three Point ^SJ^ I j: | j 

j jf-— ' Switch ^ 1 \J^' 

Head. Light Head Light 



'■3 F 



Fig. 165. Diagram of Wiring where Fig. 166. Same as above but three- 
Headlights are placed on Hoods. point Switch located on Trolley 

End of Car. 



SPECIAL METHODS OF DISTRIBUTION. 



807 




Fig. 168. Same as above 
three-point Switch. 



except 



Fig. 167. Diagram of Wiring for 
five-light Circuit with four-point 
Switch for Headlights and Plat- 
form Lights. 

Special methods of Distribution. 

For cases requiring excessively large currents carried a considerable dis- 
tance, or for ordinary currents carried excessive distances, it is usually 
economy to adopt some special method ; and among those most commonly 
mentioned are : the three-wire system, the booster system, the substation 
system. 

Three-Wire System. This system, patented some time ago by the 
General Electric Company, has been seldom used, and where used has met 
with little success, owing to the difficulty met in keeping the system bal- 
anced. 

The diagram below will assist in making the method plain. Two 500-volt 
generators are used, as in the lighting system of the same type. The rail 
return is used as the neutral conductor; and if both trolley wires could be 
made to carry the same loads, and to remain balanced, then the rail return 




THREE WIRE SYSTEM 
Fig. 169. Three-Wire System. 

would carry no current, and no trouble would occur from electrolysis. The 
overhead conductors could also be very much smaller, as currents would 
be halved, and the full voltage would be practically 1000. 

A balanced three-wire system has been proposed and is in limited use 
abroad in which the car carries two trolley poles, making contact with both 
trolley wires. The motor equipment is in duplicate, thus each set of motors 
is fed from 600 volts making the current through the return practically zero, 
and the whole equipment forming a balanced three- wire system in itself. 
This system is the only practical three- wire system and offers some advan- 
tages for transmitting large amounts of power over considerable distances. 

The Booster System. — Where current must be conveyed a long 
distance, say five to ten miles, and be delivered at 500 volts, it is hardly 
good economy to install copper enough to prevent the drop ; and if the volt- 



808 



ELECTRIC RAILWAYS. 



age of the generator be raised sufficiently to deliver the required voltage, 
the variations due to change of load will be prohibitive. 

In such cases a "booster" can be connected in series with the feeder, 
and automatically keep the pressure at the required point, as long as the 
generator delivers the normal pressure. 

The "booster" is nothing more than a series-wound dynamo, connected 
so that all the current of the feeder to which it is attached flows through 
both field and armature coils, and the voltage produced at the armature 
terminals is added to that of the line, and as the voltage so produced is in 
proportion to the current flowing, it will be seen that the pressure will rise 
and fall with the current. This is now used in many instances, both in 
lighting and for railway feeders, and especially in feeding storage batteries, 
and has met with entire success. The following cut is a diagram of the 
connections. 



6 TO 1tt M1UE8 




OVERHEAD RETURN 



BOOSTER SYSTEM 
Fig. 170. 

Return Feeder Booster. — Major Cardew, Electrical Engineer for 
the Board of Trade, some time ago devised a method of overcoming exces- 
sive drop in track return circuits by the use of insulated return feeders, in 
series with which he placed a booster. 

The booster draws current back toward the station, adding its E.M.F. to 
that in the feeder. Cardew used a motor generator, the series field of 
which was separately excited by the outgoing feeder for the same section of 
road. Thus the volts " boosted " were in direct proportion to the current 
flowing. H. F. Parshall, in adopting the return feeder booster for some of 
his work in England, used a generator in place of the motor generator of 
Major Cardew, exciting the field by the current flowing out on the trolley 
feeder, thus producing volts in the armature in proportion to the current 
flowing. The following diagram shows Parshall's arrangement. 




TROLLEY WIRE 



SEPARATELY EXCITED) 
'-\- VGENERATOR A 

BUS BAR* AT 6TATJOI* 

T* 



GENERAT0R8 

Fig. 171. Modification of Major Cardew's System of Track Return 
Booster for Preventing Excessive Drop in Rail Return Circuits. 



ELECTRIC RAILWAY BOOSTER CALCULATIONS. 809 

Electric Railway Booster Calculation*. 

(H. S. Putnam.) 

The following method of calculating the size and characteristics of electric 
railway boosters, and the graphic representation of the results will be found 
useful. 

A\ A 2 , A 3 , A*, etc., = load in amperes at various points along the line. 
These loads should be taken from schedule, and should ordinarily represent 
an average maximum condition. 

R 1 , R 2 , R 3 , R*, etc., = feeder resistance (including trolleys) to the corre- 
sponding load points. 

2 = drop in volts to the point at which it is proposed to feed into the 
system with the booster. 

V = allowable volts drop in feeder system with the booster in circuit. 
/ = amperes in booster. 

E = volts boost. 

E 

V = r = ratio of volts boost to amperes boosted. 

Rb = resistance of booster feeder. 
R = resistance of feeder system to point selected for the booster feed. 

Then assuming that all the load beyond the point at which it is proposed 
that the booster should feed into the system is concentrated at the latter 
point, 

2 = A* R* + A 2 R 2 + A 3 R\ etc. —A b R. 
2- V 



I 



R 



V 
Rb =j + p. 

E = / X p. 

V - Rb -f 

These equations give the necessary data to determine the required size 
and ratio of the booster and its feeder. In case it is desired to install a 
negative booster, the same method is followed. 

In case the load is uniformly distributed over the line, or is assumed as 
distributed in that manner, the voltage drop at any desired point on the 
line is found from the equation: 

v (2 L - d + 1) dIR 
2= ^ ' 

in which L = total length of line in feet. 

d = distance to point selected. 

I = amperes per foot. 

R = resistance of feeder system per foot. 

If desired these units can be expressed in 1000 feet or miles or any other 
unit of distance. 

When the drop to the end of the line is desired, this equation becomes: 



810 



ELECTRIC RAILWAYS. 



It is often desirable to represent these calculations graphically. Special 
cases are shown in Figs. 172, 173 and 174, in which the potential diagram 
is shown for different conditions and schedules. In the preparation of 
these diagrams it will be found convenient to plot the schedule and 
feeder and return resistances on the same sheet. In Fig. 172 it is seen that a 
negative booster is not required though one is included. Fig. 173 shows a 
system in which a booster is used at either end. Fig. 174 illustrates a different 
and more severe operating condition than shown in Fig. 173. 



























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Kelvin's Law can be applied to the booster distribution as well as to other 
methods of distribution. In most cases, however, it will be found that the 
voltage requirements will govern. The question as to whether a booster, 
more feeder copper or a sub-station shall be employed, is one which must 
be determined from the annual charges against the investment and the cost 
of the power lost in each method. In calculating the cost of the power lost, 
the load factor must be considered. 

In selecting a booster care must be exercised that its overload capacity 
shall be sufficient to take care of the maximum operating condition which 
occasionally arises in any system where boosters are likely to be employed, 
namely, when all the cars are accelerating at once. As such occasions may 
be rare, it is only necessary that the voltage shall be maintained above the 
minimum voltage at which contactors will operate, if such contactors are 
employed, that the booster motor shall carry such overload, and that the 
machines shall properly commutate at the overload current. 

By varying the value of "p" the ratio of the volts of boost to the amperes 
boosted, the size of the booster feeder and the amount of power lost in the 
booster system is changed. By Kelvin's Law the annual charges on the boos- 
ter feeder and booster should equal the annual cost of the power lost in the 
booster system. 



ELECTRIC RAILWAY BOOSTER CALCULATIONS. 811 



-- ia6oq tnoA w» v 




9 CO 

1 s 

3 *i 



1 i § i § i § i 



§ * 



812 



ELECTRIC RAILWAYS. 







© ?. oj <-• O S ■* a> §2 



ELECTRIC RAILWAY BOOSTER CALCULATIONS. 



813 



Series Boosters for Railway Service. — The amount of varia- 
tion allowable in the voltage characteristic of a series booster for 500- 
volt railway service is an important factor in its design, as it largely 
determines the amount of material required and therefore the cost. The 
actual voltage characteristic of commercial series boosters is not a straight 
line but a curve, which at partial load will be above the theoretical line as 
shown in the accompanying diagram. The amount of variation from the 
straight line is principally affected by the saturation of the magnetic circuit ; 
if the saturation is high, the variation of the voltage characteristic will be 
great. By increasing the amount of iron in the magnetic frame and there- 
fore keeping the saturation low, the voltage characteristics can be made 
to more nearly approximate a straight line; but, obviously, a machine so 
designed is more costly than a booster having a voltage characteristic 
departing further from a straight line. These facts are particularly im- 
portant in cases where high voltage boosters are used, as may be seen from the 
following example: 

In the accompanying diagram of a 200-kilowatt, 400-volt booster, the 
potential at half load is 240 volts, that is, 40 volts, or 10 per cent of the full 



400 




































* 


/ 










































































































































































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/ 








































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/ 








































































































































































































/ 






































/ 


7 








































V 








































/ 









































125 250 375 500 

Amperes 

Fig. 175. Characteristics of a 200-Kw. 400- Volt Booster. 



/oad voltage, higher than a theoretical straight line characteristic. Had less 
iron been used in the magnetic circuit the potential at half load would have 
been higher, and estimating an inctance of 320 volts, the potential would 
be 120 volts too high, or, at 695 volts, assuming a generator potential of 
575 volts. This high voltage might burn out the car lights and would 
increase the speed and subject the motors to a severe strain. 

While a straight line characteristic is not essential, the variation from a 
straight line must be kept within reasonable limits. 

Unless otherwise specified, the voltage characteristic variations of all 
series boosters of different potentials should not exceed the following values 
at partial current load and at constant speed: 



Full Load Voltages of Boosters. 

50 to 100 volts 
100 to 150 volts 
150 to 250 volts 
250 to 500 volts 



Maximum Variation 
of Full Load Voltage 
at Partial Load. 
20 per cent 
15 per cent 
12^ per cent 
10 per cent 



814 



ELECTRIC RAILWAYS. 



Temperature. — After a run of twenty-four hours at full rated 
volts and amperes, the temperature of no part of the machine should be 
more than 40° C. above the temperature of the surrounding air, provided 
the conditions of ventilation are normal and the temperature of the sur- 
rounding air does not exceed 25° C. If the temperature of the surrounding 
air differs from 25° C., the observed rise in temperature is to be corrected by 
one-half per cent for each degree centigrade that the temperature of the 
surrounding air differs from 25° C. 

The booster should be capable of standing an overload of 25 per cent of 
the full load ampere and volt capacity of the machine for one-half hour; 
and as this corresponds to the 25 per cent voltage overload, the overload 
capacity in kilowatts will be about 50 per cent. The boosters should be 
capable of standing a momentary overload of 50 per cent of the rated capacity 
in amperes at full load or about 100 per cent in kilowatt rating. 



§IB.«TAT10V SYSTEM!. 

Where traffic is especially heavy, and a railway system widespread, it is 
now the practice to use one large and economical power station with high- 
pressure generators, now invariably polyphase alternators, and to distribute 
this high-pressure alternating current to small sub-stations centrally located 
for feeding their districts, and there changing the current by means of static 
transformers and rotary converters into continuous current of the requisite 
pressure, in the case of railways 550 to 600 volts. 

The following diagrams will assist in making the system plain. 



SUB*8TATI0M 
NO. 2 



STATIC 
TRANS- 
FORMERS 




SUBSTATION, 
NO. 1 



DISTRIBUTION FROM 
SUB-STATIONS 



Fig. 176. 



The universal use of rotary converters has led to many similar designs of 
sub-stations. It is customary to install the rotaries in buildings designed for 
the purpose and Figs. 178 and 179 show a typical station in plan and eleva- 
tion. As each sub-station is in reality a complete supply station.it is neces- 
sary to install suitable protective devices for both high-tension alternating 



SUB-STATION SYSTEM. 



815 




816 



ELECTRIC RAILWAYS. 



current and 600 volts direct-current circuits. The necessary connections are 
shown in Fig. 180. . 

In Fig. 181 is shown a cross section of one of the latest types (1907) as 
developed for the United Railways and Electric Company of Baltimore, 
by Mr. L. B. Still well. This station has an unusually large capacity for 
one center of load. 

In designing sub-stations, their equipment should be based upon taking 
care of the maximum load of the stations, while a central power station 
operating through rotaries may be designed to take the average load only. 




PLAN 
Fig, 178. Rotary Converter Sub-Station. 



SUB-STATION SYSTEM. 



817 




Fig. 179. Rotary Converter Sub-Station. 



818 



ELECTRIC RAILWAYS. 



*s[swiNGINa!c.S.F. MNElj c.S.R. PANEL I A - T ' RJ 
» BRACKET! $oov AMp 600V. 300 K.W. JS0OO0VJ 



■♦■RAILWAY BUS 



TO BELL 

LOwfl 
VOLTASE — 
RELEASE 



CONNECTIONS 

SHOWN DOTTED 

SHOULD BE MADE 

ON I. C.S.R. PANEL 

0*lY 



AJTJTfAHZl 

80000*. /"~ 
60000 V 



u 

i.e. bIssl 



INCOMING LINE 




Fig. 180. Diagram of Connections for Proposed Rotary Converter 
Sub-Station. 



SUB-STATION SYSTEM. 



819 




Fig. 181. Cross section of typical large sub-station (1907) 12,000- kilowatt 
13, 000- volts alternating current, 575- volts direct current. 
L. B. Still well, Engineer. 



Portable Sub-Stations. — Many roads have a heavy traffic on 
certain lines for a portion of the year only, thus making it hardly feasible to 
expend a large sum in a permanent sub-station. For such cases, the porta- 
ble sub-station has been designed, consisting of a box car containing step- 
down transformers, rotary converter and all necessary protecting devices. 
Such a sub-station can be run out on any line having a transmission system 
connected up, and put into service in a very short time. It therefore 
forms a reserve sub-station. A plan, elevation and diagram of connection, 
of a typical portable sub-station is shown in Fig. 182. 

A portable sub-station having as high as 1000-kilowatts capacity is in 
use, see Street Railway Journal, November 4, 1905 and June 23, 1906. 



820 



ELECTRIC RAILWAYS. 




W 



& 



2 



THIRD RAIL SYSTEMS. 821 

THIRD RAIL SYSTEMS, 

{By F. R. Slater.) 

For certain classes of electric railways, such as elevated, interurban and 
underground, a steel conductor insulated from and alongside the track, 
commonly called the third rail, is much used in place of the copper over- 
head trolley wire. 

This conductor is easily installed, cheaply maintained, presents a large 
surface area for conducting and collecting the current, and is, therefore, 
particularly suitable for high speed and heavy service. With costs cal- 
culated on the basis of equal conductivity in rail and trolley wire, the 
third rail is the cheaper, except where the necessary trolley wire would be 
of considerable less conductivity than would be obtained with the smallest 
size of steel rail that would ordinarily be used. Even in such cases the 
lower cost of maintenance, together with the advantage of adaptability 
(particularly in the case of terminals, yards and very heavy high speed 
service), will frequently offset the higher first cost of the third rail and 
make it the preferable means of conducting the current from the power 
station to the car motor. 

With the coming of the heavy high-speed service of the past few years, 
the resistance of standard "T" rails has been found to be so high, that 
rails of higher specific conductivity were sought, and specifications have 
been drawn, usually based on the fact that the conductivity of a metal is 
generally directly proportionate to its purity. 

Resistance of Rails with Varying* Composition. — Mr. 
J. A. Capp, of Schenectady, conducted a series of tests of steel for 
electric conductivity. He says in part: "In most cases the purity of the 
iron specified for such rails has been so high, that not only was it difficult 
to obtain, but the iron was also correspondingly high in price. One of the 
factors governing the choice between a third rail and a trolley wire is the 
relative price of steel and copper, allowance being made for the difference 
in conductivity. Hence a balance must be struck between high conduc- 
tivity (which is equivalent to saying a high degree of purity or freedom 
from the usual metalloids associated with iron) and the cost of producing 
the steel of the composition necessary for the conductivity required. 

"Table XVII below states the electrical resistance and the chemical com- 
position of 47 samples of steel, and Table XVIII similar data on 7 samples 
of wrought or refined iron: 



822 



ELECTRIC RAILWAYS. 



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ELECTRICAL AND CHEMICAL QUALITIES OF IRON. 823 



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->* 

s 

o 


+ 

+ 


OOcO 00 00 tH ^ OS t^ <N 0000 tOrHCO OS^OS<£CO 

coco^t>^totoTt<iocotOTt<rHooeQtocorHcot^<N''roscoTf< 

hhhhhOOhhhOOhOOhOhhOhOOhh 






00 CD rji 00 H^OiN 0000 iOHC0005^05 05CO 
tO<NC0i>C0C00300O>— (COtOCOO'^'-trHCOCOt^CO'^OSOiOO 

OiOiooi>oooooc^ooi>t^oo^t^i>^^cocDi>coco # ^»oco 


in 


CD .... ROCOCO 00t^ rH COOOOi . ^ . 
NNM»hhHNONOiOHOHO^HOO^CO CO 

qqqHBHHooqqqoqqqqqqooho . o 

• 


QQ 


tJh CO COOS 
tO tH tJH 00 00 ^ «cH t^ lO lO rH rH CNJ CO *■« lO t-( CO l> ^ "# CO "tf rH tO 

OOOOOCOWOOOOOOOHOOOOOOOOhO 




Ph' 


00 T*<T^rH r*CS ^ Tft-» (M rHlOrHTj* 

00005 05N(M05 00h(NN^^(N05N(MOO(NOOhNiO>0 






OStOrHCO00cO1^00tOrH00l>tOt^OSl>rH00©c>q00tOr-i(NOS 
-* ^ ^ # ^ # 'tf "3 to "* to rJH tjh lO <M # CO tJi CO «* CN ^ ^ # CO # t(J Oq CN rH 


d 


-^ 00 <N to 
COi-liOTtiOOOq05«DO"^CO^OtOCOa>r^OOI>00«DtOCT>r-(iO 

CCM(NHH(MHHHH(M(NHNNHCqMO(MHHHINO 




6 

1 

to 
'55 


4) • 

ftrH 

&II 
P 


ococqoqtocqcocO'^cqiococq^cO'HOcocDOoooooooo 
05 tjh tjh tjh co NHoqqoj os os i> t^ i> r* # co co # co ^ # ^ # co <n ^ 

00* 00* 00 00* 00* 00* 00* 00* 00 00 t> t>* ^ 1> t>* t>* 1>* I> 1> 1> t>* 1> 1> t»* CO 


:g 

O 

S3 

a 
o 
O 


a . 

0>T3 
02 lL 

1-8 

^05 


rHiHrHrHTHC^CNCQC^C^C^CQC^C^OQO^C^COCOCOCOCOCOCO^O 


o 

a 

a 

OQ 

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0) 

o 

"o 
9 


ad 


o o o o o 

to toto _ to iO 
o .o ..ooo .ooooo .oooooooooo 

OiOSOCOCOOSOSOSOSOSOSOSTHOSCiOSOSOSOSCSOOOSOSOS 
THrHC^t>lC^THrHrHTHrHrHTH(^rHrHrHrHrHrHrHCN<NrHrHrH 


1°. 

M 

ft 


C^t^OCOCQtOCOCDCOOt^^OrHOt^tOOOOOt^t^COOSCOr-f 
CO tO r}< I> CD rH O 00 00 00 CO CO Oi CO CO CN CNJ h rH O 00 t> O»0 
tO* tH t** Ti* rJH tJ* «rj* CO* CO* CO* CO* CO* CO CO* CO* CO* CO* CO* CO CO* CN <N* (N <N rH* 



824 



ELECTRIC RAILWAYS. 



fl 

2 

- 

8 

« 



u 

© 

to 

B 



- 
M 



i 























cc 


















+ 




CD 


l- 


cq 


CO 


«o 


iO 




02 
+ 
Ah 


o 


oo 


"* 


co 


r^ 


CO 


1> 




CO 


*-* 


cq 


'I 


T— ( 


q 


q 




















-H O 


















J^ 


00 


o 




CO 


o 


^ 


CO 








o 


00 


«* 


t^ 


oo 


io 


d 




*0 


Tjl 


**. 


CO 


CO 




CO 


















o 




























T^ 


r- 


CO 


*o 






10 


CO 


o 


CO 


t>. 






o 


zn 


i— 1 




i—i 


q 


q 


q 


q 


a 


















a 

8 










• 
























<W 








r^ 


oo 


CO 




r-l 


1 

fl 


m 


CO 


CM 


CO 


o 


CO 


*■* 




q 


q 


q 


q 


q 


H 


© 


















O 


































V 


















Ph 






CD 






^ 


^ 


OS 




fc 


CO 


CO 


CO 


CO 


i> 




<tf 






q 






q 


q 


q 






00 


T}H 


«tf 




t^ 




oo 




fl 


o 


CD 


t^ 




CO 


o 






£ 


q 


q 


q 




q 




q 




d 


lO 


iO 


CD 


00 


n> 


00 

>o 


CO 










q 


rH 


q 




c5 


















o 


Ih 
















fl 

c3 




CO 


00 


rH 


rH 


CO 


i> 


CO 


+a 


00 


"*. 


"*. 


•H 


I> 


rH 


1—1 


SB 


1> 


t>* 


t»* 


1> 


CD* 


CD* 


CO* 


"8 


o 
















p* 




















St3 

CQ m 
TO 03 


00 


1> 


o 


r^ 


O 




«* 




^l 


CO 


CO 

CO* 


CO* 


o 


oo 
rj* 


CO 

CO* 


CO 

CD 


13 

fl 



















o 


















c5 


O. . 


o 






o 


o 







fl 

a 

-*5 

QQ 

1 


ad 


iq 


o 


o 


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*o 


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CO 


»o* 


iO* 


^ 


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H 


<M 


CO 


CO 


CO 


CO 


CO 


CO 


































M 


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CO 


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o 


*5 


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CO* 


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a 














" 1 

1 



RESISTANCE OF STEEL. 



825 



"A study of the tables shows that manganese preponderates in influ- 
encing the resistance of steels and that for lowest resistivity this element 
must be present in very small quantity, much smaner than is usual in mer- 
chant or structural steels. While all the other elements must be present 
only in very small percentages, so great is the preponderance of the in- 
fluence of manganese that they may be tolerated in quantities which the 
steel makers would consider reasonable, without unduly increasing the 
resistance." 



Resistance of Steel. Variation *vif li Jflangranese. 

(Carbon from 0.17 to 0.23 Per Cent.) 



Sample 
Number. 


Manganese. 


Resistance. 
Copper =1. 


Carbon. 


P + S + Si. 




Per Cent. 




Per Cent. 


Per Cent. 


2 


1.09 


12.12 


0.17 


0.144 


4 


0.95 


11.55 


0.20 


0.23 


7 


1.08 


11.51 


0.22 


0.210 


13 


0.80 


9.94 


0.23 


0.065 


16 


0.89 


9.48 


0.23 


0.073 


19 


0.68 


9.36 


0.22 


0.197 


25 


0.48 


8.36 


0.188 


0.17 


26 


0.56 


8.22 


0.22 


0.058 


27 


0.57 


8.16 


0.192 


0.058 


31 


0.48 


7.95 


0.23 


0.057 


35 


0.49 


7.73 


0.23 


0.028 


36 


0.37 


7.71 


0.19 


0.15 


43 


0.21 


7.38 


0.19 


0.099 


44 


0.22 


7.28 


0.215 


0.164 



Resistance of Steel. Variation with ITIang-anese. 

(Carbon from 0.27 to 0.33 Per Cent.) 



Sample 
Number. 



1 
14 
15 
18 
21 
22 
37 
38 
40 



Manganese. 


Resistance. 
Copper = 1 . 


Carbon. 


P + S 4- Si. 


Per Cent. 




Per Cent. 


Per Cent. 


1.27 


13.20 


0.33 


0.190 


0.95 


9.86 


0.30 


0.083 


0.99 


9.86 


0.29 


0.104 


0.65 


9.42 


0.28 


0.193 


0.49 


8.90 


0.33 


0.138 


0.45 


8.46 


0.31 


0.166 


0.41 


7.70 


0.27 


0.035 


0.28 


7.66 


0.28 


0.111 


0.42 


7.60 


0.28 


0.070 



826 



ELECTRIC RAILWAYS. 



Resistance of Steel. Variation with Carbon. 

(Manganese from 0.15 to 0.28 Per Cent.) 



Sample 
Number. 


Carbon. 


Resistance. 
Copper = 1. 


Manganese. 


P + S 4- Si. 




Per Cent. 




Per Cent. 


Per Cent. 


3 


1.40 


12.09 


0.222 


0.112 


9 


1.61 


10.76 


0.147 


0.125 


33 


0.10 


7.92 


0.25 


0.11 


38 


0.28 


7.66 


0.28 


0.111 


43 


0.19 


7.38 


0.21 


0.099 


44 


0.215 


7.28 


0.22 


0.164 


45 


0.05 


6.40 


0.19 


0.143 



To determine the influence of carbon in the above table, those steels 
have been selected which have manganese constant at from 0.15 to 0.30 
per cent, with carbon as the principal variable. 

Resistance of Steel. Variation with Carbon. 

(Manganese from 0.4 to 0.49 Per Cent.) 



Sample 
Number. 


Carbon. 


Resistance. 
Copper = 1. 


Manganese. 


P 4- S + Si. 




Per Cent. 




Per Cent. 


Per Cent. 


21 


0.33 


8.90 


0.49 


0.138 


22 


0.31 


8.46 


0.45 


0.166 


23 


0.25 


8.42 


0.41 


0.17 


24 


0.144 


8.42 


0.46 


0.17 


25 


0.188 


8.36 


0.48 


0.17 


28 


0.16 


8.06 


0.48 


0.144 


30 


0.14 


8.02 


0.41 


0.169 


31 


0.23 


7.95 


0.48 


0.057 


35 


0.23 


7.73 


0.49 


0.028 


37 


0.27 


7.70 


0.41 


0.035 


39 


0.07 


7.66 


0.40 


0.163 


40 


0.28 


7.60 


0.42 


0.070 


42 


0.15 


7.40 


0.45 


0.044 



Resistance of Steel. Influence of Carbon. 

(Results of M. Le Ch atelier.) 



Resistance. 




Composition. 




Microhms. 


Copper = 1. 


C. 


Mn. 


Si. 






Per Cent. 


Per Cent. 


Per Cent. 


10 


5.78 


0.06 


0.13 


0.05 


12.5 


7.22 


0.20 


0.15 


0.08 


14 


8.10 


0.49 


0.24 


0.05 


16 


9.25 


0.84 


0.24 


0.13 


18 


10.40 


1.21 


0.21 


0.11 


18.4 


10.64 


1.40 


0.14 


0.09 


19 


11.00 


1.61 


0.13 


0.08 



RESISTANCE OF STEEL. 



827 



Resistance of Steel. Variation with Carbon. Results of 

Barrett, Brown and Hadfleld. Temperature 19° C. 





Resistance. 


Composition. 




Sample 












Mark. 


Microhms. 












per 
Cu. CM. 


Copper = 1. 


Carbon. 


Manganese. 


Silicon. 








Per Cent. 


Per Cent. 


Per Cent. 


1392G 


19.1 


11.19 


1.23 


0.14 


0.12 


1392L 


17.6 


10.31 


1.09 


0.32 


0.17 


1392A 


17.9 


10.49 


0.85 


0.32 


0.17 


1392B 


17.2 


10.07 


0.84 


0.18 


0.20 


13921 


16.7 


9.78 


0.83 


0.25 


0.06 


1392H 


16.1 


9.43 


0.78 


0.10 


0.10 


1166A 


13.4 


7.85 


0.14 




0.08 



R'EKlMTi.YCE Of STEE-L. 

Compiled by H. N. Latey. 

C. Greater than .50%. 



c. 


Mn. 


Si. 


P. 


S. 


R. 

Cu. = 1 


Authority. 


Remarks. 


.535 

.568 
.588 
.610 
.740 
.780 


.592 

.608 

.632 

.650 

.580 

.100 

.250 

.180 

.240 

.320 

.200 

.580 

.320 

.210 

.140 

.620 

.140 

.222 

.130 

.147 

3.810 

7.000 

13.000 

15.25 

18.50 

11.50 


.201 

.204 

.214 

.220 

.200 

.100 

.060 

.200 

.130 

.170 

Tr. 

.490 

.170 

.110 

.120 

.460 

.090 

.082 

.080 

.092 

.630 

.630 

.630 

.630 

.630 

.630 


.051 
.053 
.056 
.062 
.043 


.059 
.061 
.065 
.071 
.036 


11.30 

11.40 

11.50 

12.90 

11.40 

8.50 

8.87 

9.36 

9.25 

9.55 

9.78 

13.00 

10.10 

9.25 

10.20 

13.70 

10.64 

10.76 

11.00 

10.76 

25.70 

32.40 

37.10 

38.55 

40.10 

35.80 


Parshall 

G. E. Co. 

Barrett 

Chatelier 
Barrett 
G. E. Co. 
Barrett 

Chatelier 
Barrett 

Chatelier 
G. E. Co. 
Chatelier 
G. E. Co. 

Barrett 


T Rail. 
Bar. 


.830 
.840 








.840 








.850 






Bar. 


.900 
1.000 
1.090 


.040 


.030 


Bar. 


1.210 
1.230 
1.250 






Bar. 


1.400 








1.400 

1.610 

1.610 

.780 


.010 
' .015 


.018 
' .018 


Bar. 


1.200 








1.230 








1.500 








1.540 








1.660 

















828 



ELECTRIC RAILWAYS. 



ASSISTANCE OV ^TEEl. 
C. Less Than .50%. 



c. 


Mn. 


Si. 


P. 


S. 


R. 
Cu.= 1 


Authority. 


Remarks. 


.028 


Tr. 


.070 


.004 


.005 


5.96 


Barrett 


Iron bar, annealed. 


.028 


Tr. 


.070 


.004 


.005 


6.06 


" 


Iron bar, not an- 
nealed. 


.030 


.036 


.140 


.004 


.005 


6.38 


" 


Iron bar. 


.045 


.200 


Tr. 


.040 


.030 


6.58 


G. E. Co. 


<i « 


.050 


.180 


.020 


.013 


.011 


6.68 


Barrett, G.E. 


it M 


.050 


.180 


.020 


.004 


.005 


6.60 


Barrett 


** " 


.050 


.190 


.030 


.054 


.059 


6.50 




T Rail. U. R. Co., 






London. 


.058 


.100 


.012 


.014 


Tr. 


6.17 


G. E. Co. 


Bar, Swedish iron. 


.060 


.130 


.050 






5.78 


Chatelier 




.070 


.400 


.013 


' .080 


" .070 


7.66 


G. E. Co. 




.080 


Tr. 


.024 


.130 


.008 


7.11 


" 


Staybolt iron. 


.090 


Tr. 


.011 


.015 


.030 


6.58 


" 




.090 


.210 


.020 


.030 


.050 


7.43 


Campredon 


Wire, 3 M.M. diam. 


.100 


.240 


.020 


.040 


.050 


7.74 


" 


44 44 44 


.100 


.250 


.050 


.040 


.020 


7.92 


G. E. Co. 




.100 


.260 


.020 


.040 


.060 


8.00 


Campredon 


Wire, 3 M.M. diam. 


.100 


.310 


.020 


.050 


.050 


8.16 


11 


44 44 44 


.100 


.400 


.020 


.040 


.070 


8.67 


44 


44 " 44 


.100 


.550 


.024 


.080 


.050 


8.04 


G. E. Co. 




.110 


.350 


.030 


.060 


.060 


8.41 


Campredon 


Wire, 3 M.M. diam. 


.110 


.490 


.030 


.060 


.060 


9.08 


11 


44 44 4 * 


.120 


.330 


.030 


.050 


.070 


8.30 


44 


44 M " 


.120 


.400 


.020 


.070 


.070 


8.74 


" 


M 41 II 


.140 


Tr. 


.080 


.004 


.005 


7.43 


Barrett 


Bar. 


.140 


.410 


.009 


.110 


.050 


8.02 


G. E. Co. 




.144 


.460 


Tr. 


.090 


.080 


8.42 


44 


TRail,A.E.&C.Ry. 


.150 


.064 


.130 


.036 


.020 


7.48 




Bar, reinforced 
iron. 


.150 


.068 


.150 


.130 


.020 


7.82 




Bar, reinforced 
iron. 


.150 


.450 


Tr. 


.011 


.033 


7.40 


" 




.160 


.018 


.015 


.049 


.011 


6.12 


" 


Bar, Norway iron. 


.160 


.074 


.100 


.120 


.027 


7.41 


" 


Bar, refined iron. 


.160 


.380 


.009 


.080 


.040 


7.48 


" 




.1*60 


.480 


.010 


.091 


.040 


8.06 


" 




.160 


.660 


.014 


.074 


.030 


9.36 


44 




.170 


.027 


.077 


.074 


.022 


6.76 


44 


Bar, spec. ref. iron. 


.188 


.480 


Tr. 


.090 


.080 


8.36 


44 


TRail.A.E.&C.Ry. 


.190 


.210 


.034 


.025 


.040 


7.38 


44 




.190 


.370 


.010 


.090 


.050 


7.71 


*• 




.192 


.570 


Tr. 


.024 


.340 


8.16 


14 




.200 


.150 
.500 


.080 
.130 






7.22 
8.42 


Chatelier 
Barrett 




.200 


' .0*04 


' .005 


Bar. 


.200 


.950 


.050 


.100 


.080 


11.55 


G. E. Co. 


TRail. 


.215 


.220 




.051 


.113 


7.28 




4 




.220 


.560 


" Tr. ' 


.024 


.340 


8.22 




4 




.220 


.680 


.050 


.077 


.070 


9.36 




* 




.230 


.490 


.004 


.024 


Tr. 


7.73 




4 




.230 


.480 


.023 


.024 


.010 


7.95 




4 




.230 


.890 


.005 


.058 


.010 


9.48 




* 




.230 


.800 


.016 


.046 


.033 


10.06 




• 




.240 


.570 


.003 


.029 


.010 


7.93 




4 




.250 


.370 


.018 


.040 


.030 


7.74 




4 




.250 


.410 


.030 


.100 


.040 


8.42 







RESISTANCE OF STEEL. 



829 



RESISTANCE Of SMIEIi — Continued. 
C. Less Than .50%. 



c. 


Mn. 


Si. 


P. 


S. 


R. 
Cu. = l 


Authority. 


Remarks. 


.260 


.830 


.004 


.053 


.010 


9.44 


G. E. Co. 




.270 


.410 


.001 


.024 


.010 


7.70 


■■ 




.280 


.280 


.040 


.027 


.034 


7.66 


*• 




.280 


.420 


.008 


.022 


.040 


7.60 


M 




.280 


.650 


.050 


.083 


.060 


9.42 


«« 




.290 


.990 


.010 


.084 


.010 


9.86 


«« 




.300 


.950 


.010 


.063 


.010 


9.86 


'* 




.310 


.450 


.026 


.100 


.•040 


8.46 


" 




.330 


.490 


.020 


.068 


.050 


8.90 


•• 




.360 


.800 


.047 


.100 


.040 


11.51 


" 




.360 


.870 


.040 


.080 


.090 


10.04 


»• 


T Rail. 


.370 


.730 


.060 


.090 


.040 


9.94 


»* 


M 


.378 


.550 


.181 


.040 


.041 


10.80 


Parshall 


" 


.410 


.720 


.110 


.039 


.041 


10.56 


G. E. Co. 




.430 


.770 


.066 


.100 


.040 


11.51 


" 




.446 


.568 


.188 


.046 


.044 


11.10 


Parshall 


T Rail. 


.490 


.240 

3.500 

5.400 

15.400 

10.100 

1.090 


.050 
.130 
.130 
.130 
.630 
.004 






8.10 
17.28 
19.65 
37.80 
37.10 
12.12 


Chatelier 
Barrett 

G. E. Co. 




.080 






Bar. 


.150 








.150 






«« 


.160 






«« 


.170 


.090 


.050 


T Rail. 


.220 


1.080 


.060 


.100 


.050 


11.51 


" 


" 


.240 


1.000 

13.000 

5.15 

1.27 


.130 
.130 
.130 
.050 






13.70 
35.80 
21.75 
13.20 


Barrett 

<« 
G. E. Co. 


Bar. 


.260 








.320 






«« 


.330 


.09 


.05 


T Rail. 


.360 


4.00 
4.75 
2.25 


.130 
.130 
.130 






16.70 
17.10 
17.00 


Barrett 


Bar. 


.360 








.410 






«« 











For a satisfactory third rail, the lowest possible resistance (from 6 to 
6.5 times that of copper?) is not necessary; and the great cost of making 
such extremely pure steel is not warranted. Assuming, then, that a rail made 
from steel having a resistance not greater than eight times that of copper 
(13.8 microhms at 20° C.) would be desirable, the figures tabulated seem 
to indicate that the following extreme composition would be permissible: 

PER CENT. 

Carbon up to 0.2 

Manganese up to 0.4 

Phosphorus up to 0.06 

Sulphur up to 0.06 

Silicon up to 0.05 

This composition, however, would be extreme, and any overstepping 
Df bounds might result in too great resistance; therefore, for resistance 
up to eight times that of copper, the specified analysis should be: 

PER CENT. 

Carbon not to exceed 0.15 

Manganese not to exceed 0.30 

Phosphorus not to exceed 0.06 • 

Sulphur not to exceed 0.06 

Silicon not to exceed 0.05 



830 



ELECTRIC RAILWAYS. 



This latter composition is one which could be made easily in any open- 
hearth furnace, and it should present no difficulty in rolling to a shape 
suitable for conductor rails, such as that shown 
(Fig. 183). In fact, steel of this composition has 
been successfully rolled into sheets as thin as 0.014 
in., and was for a long time a standard product 
of a large sheet-mill. 

A section of a conductor-rail has been designed 
by Mr. W. B. Potter, Chief Engineer of the Rail- 
way Department of the General Electric Co., 
which, when 2.5 in. wide by 4 in. high, will weigh 
about 98 lb. to the yard. This shape, which is 
shown in Fig. 189, may be easily rolled in any 
merchant-bar mill heavy enough to attempt sec- 
tions of this weight. A dovetail at the bottom 
provides an easy means of securing by fish plates 
of special forms, and any of the common forms 
of bond may easily be applied. 

The Manhattan Railway Company (Elevated) 
and the Interborough Rapid Transit Company 
(Subway), of New York City, both purchased 
their rails upon specifications as to their chemical 
composition. Each rolling was analyzed, and 




Fig. 183. Cross Section 
of a New Conductor 
Rail, Designed by Mr. 
W. B. Potter. 



the resistance of several samples measured. 
Following are the analyses and specifications: 



Weight of rail . . . 

Area of cross section 

Carbon 

Manganese .... 

Phosphorus .... 

Sulphur 

Silicon 

Specific resistance 
(microhms) . . . 

Temperature of test. 

Conductivity . . . 

Resistance — Copper 
= 1 

Equivalent of cop- 
per, CM 



Manhattan. 



Specifications. 



100 lbs. 
9.8 sq. in. 
.10 
.55 
.10 
.08 
.03 



8.31 
1,500,000 



Analysis. 



.098 
.485 
.085 
.158 
.022 

15.883 
26° C. 
11.13% 

8.98 

1,389,000 



Interborough. 



Specifications. 


Analysis. 


75 lbs. 




7.4 


sq. m. 




.08- 


.15 


.161 


.50- 


.70 


.561 


.10 




.091 


.05 




.055 


.05 




Trace 
14.99 




23° C. 




11.68% 


8.37 




8.56 


1,125,000 


1,100,000 



location of Third Rail. — The location of the third rail with refer- 
ence to the track rails has been different for each road using it. The Penn- 
sylvania, Long Island, New York Central and Interborough Rapid Transit 
railroads have agreed upon a location which will not interfere with the 

f>assage of any of their rolling stock, either freight or passenger. This 
ocation is as follows: "The third or conductor rail shall be located outside 
of and parallel to the track rails so that its center line shall be 27 inches 
from the track gauge line and its upper face 3^ inches above the top of 
the track rail." 



THIRD RAIL INSULATORS. 



831 





From Top of 


From Track 


Relative Location of Third Rail 


Third Rail 


Gauge Line 


on Different Railway Systems. 


to Top of 


to Center of 




Track Rail. 


Third Rail. 


General Electric Railroad, Schenectady 


3" 


28" 


Met. West Side Elevated, Chicago .... 


6J* 


20£" 


Lake Street Elevated, Chicago 


6¥ 


20£" 


South Side Elevated, Chicago 


e>r 


20i" 


Northwestern Elevated, Chicago 


6i" 


2or 


Brooklyn Elevated, Brooklvn 


6" 


22|" 


Manhattan Elevated, New York .... 


7V 


20f* 


Albany & Hudson, New York 


6" 


27" 


Boston Elevated, Boston 


6" 


20|" 


Aurora, Elgin & Chicago, 111 


6 5-16" 


20i" 
27" 


Columbus, Buckeye Lake & Newark. Ohio 


6" 


Columbus, London & Springfield, Ohio . . 


6" 


27" 


B. & 0. R.R., Baltimore 


2f* 


24" 


N.Y., N.H. & H. R.R., Connecticut . . . 


W 


Center 


Central London. England 


w 


Center 



THIRD RAIL 1.\H'L1T01|K, 

The requirements for a third rail insulator are: 

(a) That it shall have sufficient strength to carry the weight of the 
rail and not crush under the vibration of passing trains. 

(b) That its insulating body shall be made of a thoroughly vitreous 
material, practically impervious to heat and moisture, and having its 
exposed surface well glazed. 

(c) That its resistance shall, when wet over its entire surface, be 1 megohm 
at least. 

(d) That it have a drip edge between the rail and ground. 

(e) That the portion upon which the rail rests shall allow free move- 
ment of the rail, laterally and longitudinally _ to allow for expansion and 
contraction, and vertically to allow for depression of ties during the passage 
of trains. 

(/) That it must be capable of easy and quick renewal. 

Those here illustrated show the two general types which have been most 
widely used (Fig. 184 and Fig. 185). Fig. 184 consists of a metal base 
surrounded by an insulating body of vitreous material to which are clamped 
the clips which hold the rail. Fig. 185 is practically the same, except 
that in place of the clips clamping the insulating body there is a metal 
cap setting over it, having ears which may or may not be bent over the rail. 





Fig. 184. 



Fig. 185. 



These insulators are usually placed 10 feet apart, except on sharp curves, 
where they are generally placed on 5-foot centers in order to keep the rai' 
up to gauge, to allow for the expansion and contraction. The rail is usually 
anchored at the two center insulators, any movement being taken up at 
the joints where a sufficient distance has been left between rails for 



832 



ELECTRIC RAILWAYS. 



the purpose. This is either done (1) by making the portion of the insu- 
lator upon which the rail rests in such way that it may be bolted to the 
web of the rail, or (2) by making the portion of the insulator upon which 
the rail rests with a lug that fits into a slot punched in the bottom flange 
of the rail. 

Where the shoe or current collector leaves the third rail at the ends 
on straight track and at the side at switches and crossovers, suitable in- 
clines must be provided, because the shoes normally hang lower than the 
top of the third rail. (See Fig. 186.) 




^ Tbircl Rail Shoe. — These shoes are of practically but two types 
viz., the link shoe and the slipper shoe. 

The link shoe is shown in Fig. 187, and is attached to the coil spring seat 
of the truck, and the shoe proper is suspended by two links from the yoke 



Motor Lead 




Fig. 187. Link Shoe, used on Manhattan Elevated Railway. 

which is in turn bolted to castings on the shoe beam. This type of shoe is 
not entirely satisfactory because it has a tendency for the shoe to ride 
on its nose when the speed is high, and does not permit of adequate pro- 
tection of the rail from the weather. 



THIRD RAIL INSULATORS. 



833 



The slipper shoe shown in Fig. 188 is also carried from the shoe beam, 
which in turn is fastened to the spring seat. This type of shoe is quieter 




Fig. 188. 



Shoe. 



sparks less under heavy currents and allows of the use of a top guard, 
usually a plank or wide channel section of light steel. (See Fig. 189.) 




P Z\W I^S .rq 



Tie 



Fig. 189. 

Direct metallic connection is maintained from the shoe to the motor 
in the types of shoes shown, by copper terminals bolted to both yoke and 
shoe, these two being connected to each other and to the motor by extra 
flexible copper leads. 



834 



ELECTRIC RAILWAYS. 



Hew York Central Third Rail. — This arrangement of contact 
rail is the joint invention of W. J. Wilgus and Frank J. Sprague, and as will 
be noted in the illustration, is supported every eleven feet by iron brackets, 
which hold the insulation blocks by special clamps. These blocks, which 
are in two pieces, are six inches long by f inch in thickness, and are inter- 
changeable. Between supporting brackets the upper part of the rail is 



If 2 6 To Gauge Line 




Laterally and Longitudinally 

Section of Protection 
Sheathing 

Fig. 190. Details of Third Rail Construction, New York Central R.R. 



covered by wooden sheathing, which is applied in three parts and nailed 
together. At the joints where the third rail is bonded, and at the feeder 
taps, the wooden sheathing is mortised. This rail is given a little play 
in the insulators for expansion and contraction, except at certain central 
points, where it is anchored. It weighs 70 pounds per yard; is of special 
section and composition; and has a resistivity between seven and eight 
times that of copper. The under or contact surface is placed 2f inches 
above the top of the service rail, and its center is 4 feet 9 1 inches from 
the center line of the service track, or 2 feet 5 inches from the gauge line 
of the near rail. 



CONDUIT SYSTEMS OP ELECTRIC RAILWAYS. 835 



AJPrROXIlflATE X§TIiVATED COST OF OSTE mi fi 

ow so«L£ track: or PROIECTED third 

RAIL. 

(W. B. Potter.) 
6-Inch Channel Iron Protection. 

5260' 75-lb. 3" X %¥ conductor rail at $43 per ton (66 tons) . . $2,840.00 
528 Reconstructed granite insulators, clamps and lag screws 

at 40 cents per set 211.00 

352 No. 0000 GE 9" Form B bonds at 38 cents _ 134.00 

$3,185.00 
5280' 31^-lb. 6" channel iron guard for conductor rail at $45 

per ton (27.71 tons) $1,248.00 

792 Malleable-iron guard supports at 36 cents 286.00 

176 Malleable-iron fish plates and bolts at 25 cent 44.00 

$1,578.00 
Approximate labor for installation, including drilling rails and 

channels 900.00 

Total cost $5,663.00 

8-Inch Channel Iron Protection. 

5280' 75-lb. 3* X 2\" conductor rail at $48 per ton (66 tons) . . $2,840.00 
528 Reconstructed granite insulators, clamps and lag screws 

at 40 cents per set 211.00 

352 No. 0000 GE 9" Form B bonds at 38 cents 134.00 

$3,185.00 
5280' 48-lb. 8" channel iron guard for rail at $45 per ton (42.24 

tons) $1,900.00 

792 Malleable-iron guard-rail supports at 36 cents 286.00 

176 Malleable-iron fish plates and bolts at 25 cents 44.00 

$2,230.00 
Approximate labor for installation, including drilling rails and 

channels 900.00 

Total cost $6,315.00 

8-Inch Wood Protection. 

5280' 75-lb. 3" X 2£" conductor rail at $43 per ton (66 tons) . . $2,480.00 
528 Reconstructed granite insulators, clamps ana lag screws 

at 40 cents per set 211.00 

352 No. 0000 GE 9" Form B bonds at 38 cents _ 134.00 

$3,185.00 
5280' Ash plank H" X 8" at $48 (M board feet) in the rough, 

5280 board feet $253.00 

792 Malleable-iron guard-rail supports for wooden guard 

plank at 39 cents 308.00 

176 Malleable-iron fish plates and bolts at 25 cents 44.00 

$605.00 

Approximate labor for installation, including drilling rails . . . 750.00 

Total cost $4,540.00 

CONDUIT SYSTEMS OJF EIECTRIC RAILWAYS. 

Previous to 1893 many patents were granted on conduit and other -sub- 
surface systems of carrying the conductors for electric railways, and hun- 
dreds of experiments were carried on; but it has been only since that year 
that capitalists have had the necessary courage to expend enough money 
to make a really successfully operating road. The work was put into 
the hands of competent mechanical engineers, who perfected and improved 
the mechanical details, and the electrical part of the problem was by that 
means rendered very simple. 



836 ELECTRIC RAILWAYS. 

The Metropolitan Street Railway Company of New York, and the Metro- 
politan Railroad Company of Washington, decided, in 1894, that, by build- 
ing a conduit more nearly approaching cable construction, the underground 
electric system could be made a success. The former contracted for its 
Lenox Avenue line, and the latter for its Ninth Street line. The New York 
road was in operation by June, 1895; the Washington road by August of 
the same year ; and they continue to run successfully. While modifications 
have been made in some details since these roads were started, yet the 
present construction is substantially the same. These roads were the first 
to avoid the almost universal mistake of spending too little and building 
unsubstantially where new enterprises are undertaken. The history, in 
these particulars, of the development of overhead trolley and conduit roads 
is to-day repeating itself in the third-rail equipment of branch and local 
steam roads. 

The Metropolitan Railroad, in Washington, used yokes of cast iron placed 
on concrete foundations, and carrying the track and slot rails. The slot 
rails had deep inner flanges, with water lips to prevent dripping on con- 
ductors. The conductor rails were T bars 4 inches deep, 13 feet 6 inches 
long, 6 inches apart, and were suspended from double porcelain corrugated 
insulators filled with lead and mounted on cast-iron handholes. A sliding 
plow of soft cast iron collected the current. During the first few months of 
its operation there were but few delays, mostly due to causes other than 
electrical defects. Some trouble came from short-circuiting of plows, which 
was remedied by fuses on plow leads, and a water rheostat at the power- 
house. The flooding of conduits did not stop the road, although the 
leakage was 300 to 550 amperes. Under such circumstances the voltage was 
reduced from 500 to about 300. The average leakage on minus side, when 
tested with plus side grounded, was one ampere over 6,500 insulators. The 
positive side always showed higher insulation than the negative, possibly 
due to electrolytic action causing deposits on the negative pole. 

The Lenox Avenue line of the Metropolitan Street Railway was the first 
permanently successful underground conduit line in the United States. 
The cast-iron yokes were similar to those used on their cable lines, placed 
5 feet apart. Manholes were 30 feet apart, with soapstone and sulphur ped- 
estal insulators located under each, carrying channel beam conductors, 
making a metallic circuit. At first the voltage was 350, but it was gradually 
raised to 500. The pedestal support was afterwards abandoned, and sus- 
pended insulators used every 15 feet, at handholes. At one time iron-tube 
contact conductors were tried, but they proved unsatisfactory. 

The details of track construction for underground or sub-surface trolley 
railroads are essentially of a special nature, and are determined in every 
case by the local conditions and requirements. They belong to the civil en- 
gineering class entirely, and will not be treated here in any way other than 
to show cuts of the yokes and general construction. 

The requirements of the conduit for sub-surface trolley conductors are 
first, that it shall be perfectly drained, and second, that it be so designed 
that the metallic conductors are out of reach from the surface, of any- 
thing but the plow and its contacts. Another requisite is that the conduct- 
ing rails and their insulated supports shall be strong and easily reached for 
repairs or improvement of insulation. 

The conducting rails must be secured to their insulating supports in such 
a manner as to provide for expansion and contraction. This can be done by 
fastening the center of each section of bar solid to an insulated support at 
that point, and then slotting the ends of the bar where they are supported 
on insulators. The ends of the bars will be bonded in a manner somewhat 
similar to the ordinary rail bonding. 

The trolley circuit of the sub-surface railway differs from the ordinary 
overhead trolley system in that while the latter has a single insulated con- 
ductor, and return is made by the regular running rails, the former has a 
complete metallic circuit, local, and disconnected in every way from track 
return. 

The contact rails must be treated like a double-trolley wire, and calculations 
for feeders and feeding in points can be made after the methods explained 
for overhead circuits and feeders earlier in this chapter. Feeders and mains 
are usually laid in underground conduits for this work, and the contact rails 
may be kept continuous or may be divided into as many sections as the ser- 
vice may demand, taps from the mains or feeders being made to the contact 



CONDUIT SYSTEMS OF ELECTRIC RAILWAYS. 



837 





838 



ELECTRIC RAILWAYS. 




Fig. 193. Drainage at Manhole of Conduit. Metropolitan Railroad, 
Washington, 1895. 



h 



|-\ 









^.A-J^j- J °J_ END ELEVATION OF CLIP 








Pl*N OF CLIP 

Fig. 194. Clip and Ear for Conduit, Metropolitan Railroad, Washington, 

1895. 

rails at such points as may be determined as necessary. All the insulated 
conductors should be of the highest class: may be insulated with rubber or 
paper, but should in any case be covered with lead. Especial care should 
be taken in making joints between the conducting rail and copper conductor 
so that jarring will not disturb the contact. 

Other than the above few general facts it is difficult to say much regard- 
ing this type of electric railway, for it is so expensive to install that it can 
be used in but a few of the largest cities, and in every case will be special, 
and require special study to determine and meet the local conditions. The 
reader is referred to the files of the street railway journals for complete 
descriptions of the few installations of this type of electric railway. 



CONDUIT SYSTEMS OF ELECTRIC RAILWAYS. 



839 



Following are a number of cuts showing the standard construction of 
electric conduits as designed and built by the Metropolitan Street Railway 
Company, of New York. The system of railway may be said to use all the 
latest methods, including wire-carrying conduits along side or under the 
tracks, as will be seen by the next cut. 

The porcelain insulator here shown for supporting the contact rails is 
very substantial in design and construction, and by its location at a hand- 
hole is easily reached for cleaning, repairs, and replacement. The plow has 
also received careful attention, and those now used as standard by the Met- 
ropolitan Company leave little to be desired. 




Fig. 195. Section of Conduit, Metropolitan Street Railway, New York. — 
Standard Work, 1897-98. 




Fig. 196. Section, Side and End Elevation of Plow, Metropolitan Street 
Railway, New York. — Standard Work, 1897-99. 



840 



ELECTRIC RAILWAYS. 




TOP OF TRAM. RAILJ 



Fig. 197. Plan and Elevation of Plow Suspension 
from Truck, Metropolitan Street Railway, ISIew 
York. — Standard Work, 1897-98. 



*£^=£*=:=F3SP 




mg.198. Section and Elevation of Insulator, Metropolitan Street Railway, 
New York. — Star dard Work, 1897-98. 



SURFACE CONTACT OH 1 LF(TIH>..tI tCXETIC 

iYSTEKIS. 

The development of surface contact systems began even earlier than the 
use of the overhead-trolley wire, and many patents have been issued on the 



WESTINGHOUSE SURFACE CONTACT SYSTEM. 841 

same. Most of these failed through ignorance of the requirements, and 
timidity of capital in taking up a new device answers for others. 

The Westinghouse Electric and Manufacturing Company and the General 
Electric Company finally took the matter up, and being equipped with vast 
experience of the requirements, and the necessary engineering talent and 
apparatus, have each developed a system that is simple to a degree, and is 
said to cost but half as much to install as the conduit system, ai^d to oifer 
advantages not known to that or other systems. 

I quote as follows from a bulletin issued by the Westinghouse Electric 
and Manufacturing Company. 

Some Advantages of the System. 

No poles, overhead wires, or troublesome switches are employed. The 
streets, yards, and buildings are left free of all obstructions. 

The facility with which freight cars can be drilled in yards and through 
buildings, without turning the trolley whenever the direction of a motor 
car or locomotive is reversed, and the absence of the necessity of guiding 
the trolley through the multiplicity of switches usually found in factory 
yards and buildings, is of great advantage, permitting, in fact, the use of 
electric locomotives where otherwise electricity could not be used. 

The only visible parts of the system, when installed for street railway 
work, are a row of switch boxes between the tracks, flush with the pave- 
ment, and a double row of small contact buttons which project slightly 
above the pavement, and do not impede traffic in any way. 

This system can be used in cities where the use of the overhead trolley is 
not permitted, and if desired the continuation of the road in the suburbs 
can be operated by the cheaper overhead system. It would only be neces- 
sary to have a trolley base and pole mounted on the car, the pole being 
kept down when not in use. 

There are no deep excavations to make. The system can be installed on 
any road already in operation without tearing up the ties. 

The cost is only about one-half that of a cable or open conduit road. 

The insulation of all parts of the line, the switches, and the contact but- 
tons is such that the possibility of grounds and short circuits is reduced to a 
minimum. 

The system is easy to install, simple in operation, and reliable under all 
conditions of track and climate. 

Finally, the system is absolutely safe. It is impossible for anyone on the 
street to receive a shock, as all the contact buttons are " dead " except- 
ing those directly underneath the car. 

Requirements. 

In devising this system the following requirements of successful working 
were carefully considered. 

The insulation must be sufficient to prevent any abnormal leakage of 
current. 

The means for supplying the current to the car must be infallible. 

The apparatus must be simple, so that inexperienced men may operate it 
without difficulty. 

The system must operate under various climatic conditions. 

Finally, absolute safety must be assured. 

WESTHtfGHOUSE §¥STEH. 

This system includes the following elements. 

First. Electro-magnetic switches, inclosed in moisture-proof iron cases. 
Each switch is permanently connected to the positive main or feeder which 
is laid parallel to the track. 

Second. Cast-iron contact plates or buttons, two in each group, placed 
between the rails and electrically connected to the switches. A separate 
switch is provided for each group of buttons. 

Third. The conductor forming the positive main or feeder. This is com- 
pletely inclosed in wrought-iron pipe, and is connected to the various 
switches. 



842 



ELECTRIC RAILWAYS. 



Fourth. Metal contact shoes or bars, suspended from the car trucks ; 
two bars on each car. 

Fifth. A small storage battery carried upon the car. 

The operation of the system is described as follows, and is illustrated by 
cuts making plain the text. 




Fig. 199. Diagram of Switch Connections. 



OAR WIRING 



CONTROLLER 



Dj^- STORAGE BATTERY' 

A r 




Fig. 200. Diagram of Car Connections. 

Electro-magnetic switches, X lf X 2 , X 3M inclosed in water-tight casings, 
are installed at intervals of about 15 feet along the track to be operated. 
Each switch is provided with two windings, I and H, which are connected 
by the wires N and M to two cast-iron contact buttons, 1 and 2, which are 
mounted on suitable insulators and placed between the rails. 

Each car to be operated on this system is provided with two spring- 
mounted T steel contact bars, Qj and Q 2 , and a few cells of storage battery 
in addition to the usual controllers and motors. The contact bars are 
mounted at the same distance apart as the contact pins, 1 and 2, so that as 
the cars advance along the track the bars will always be in contact with at 
least one pair, as the length of the bar exceeds the distance between any 
two pairs by several feet. 

Suppose a car is standing on the track over the switch X 2 , the contact 
bars, Qi and Q 2 , being then in connection with the buttons 1 and 2 respec- 
tively. The first step is to " pick up " the current, i.e., render the buttons 
1 and 2 alive. 

Switch A is first closed ; this completes the circuit from the storage bat- 
tery, D, through the wiring, R, contact shoe, Q 1? button No. 1, and shunt 
coil, H, to the ground. The current passing through H magnetizes the 
core, S, which in turn attracts the armature, P, closing the switch and es- 
tablishing connection between the 500-V main feeder K, and button No. 2, 
through the contacts, JJ, coil I, and wiring N. Switch C is now closed and 
switch A opened ; the switch X, is kept closed, however, by the current 
flowing from button No. 2 through bar Q 2 , connection T, resistance L, con- 
nection R, bar Q,, button No. 1, connection M, coil H to ground. 

The car now proceeds on its way, current from the main passing through 
connection T, to the controller and motors. When the car has advanced a 
short distance the contact bars make connection with the pair of buttons 
connected to switch X 3 . Current then passes from bar Q, through the 
shunt coil of this switcli. The operation described above is then repeated. 
As soon as the bars leave the buttons 1 and 2, current ceases to pass through 
the coils I and H of switch X 2 , and this switch immediately opens by grav- 



WESTINGHOUSE SURFACE CONTACT SYSTEM. 843 

ity, leaving the buttons connected to it dead and harmless. As connection 
with the main has already been established through switch X 3 , there will 
be a continuous flow of current from the feeder, and no flash will occur 
either at the button or the switch. 

It will be observed that all the current passing to the car from the main 
through switch contacts J J passes through the series coil, I, holding the 
switch firmly closed and precluding all possibility of its opening while cur- 
rent is passing through the contacts, even should the circuit through coil H 
be interrupted. Although the act of "picking up the current" requires 
some time to describe, it takes in practice only a few seconds. 

Two separate switches, A and C, are shown in the diagram; but in practice 
one special switch of circular form is provided, and the necessary combina- 
tions required for " picking up the current " are made by one revolution of 
the switch handle. 

The battery need only be employed to lift the first switch; for after thac 
has been closed, the contact shoes bridge the main voltage over from one set 
of pins to another, as described, thus closing the successive switches, with- 
out further attention from the motorman. 

The battery is charged by leaving switches A and C closed at the same 
time. 

The Switch. 

Fig.201 shows the general arrangement of switch, bell, and pan. The 
switch and magnet are mounted upon a marble slab, which is secured in 
the bell by means of screws to the bosses, B B. 

The switch magnet, M, is of the iron-clad type. It is secured to the upper 




Fig. 201. Section of Switch, Bell, and Pan- 

side of the marble base, and is provided with a fine (shunt) winding for the 
" pick up " current, and a coarse (series) winding through which the work- 
ing current passes. 

When magnetized the poles attract an armature attached to a bridge piece, 
J,each end of which carries a carbon disk, N. R, R, are guides for the bridge 
piece, J. Directly above each of the carbon disks, N, is a stationary disk, 
O, mounted upon a marble base. One of the disks, O, is permanently con- 
nected by means of one of the contact cups, Gj, as explained later, to the 
positive main cable, and the other, through the series coil and cup, G„ to 
the positive contact button. 



844 



ELECTRIC RAILWAYS. 



The pan, C, is provided with four bosses, S, to support the vertical split 
pins, F, which are insulated from the pan. These pins slide into recepta- 
cles, G, on the switch base. The pins, F, are provided with connectors, I, 
for the purpose of making connection with the several cables, H, which pass 
through the holes in the under side of the pan. The pan is completely filled 
with paramne after the connections are made, thus effectually keeping out 
all moisture. 

The object of the bell, A, and the pan, C, with the split pins, F, and the 
cups, G, is to provide a ready means of examination of the switch without 
disconnecting the wires. The bell can be lifted entirely free of the pan. 
In replacing it, it is only necessary to see that a lug, T, on the side of the 
cover, fits into a slide, U, on the frame. When in this position the split 
pins make connections with their corresponding cups, G. 

The bell, A, is provided with lugs, L, to facilitate handling ; and also a 
double lip, W. The inner portion of this lip fits into and over the annular 
groove, D, of pan C. This groove is filled with a heavy non-vaporizing oil. 
The outer portion of lip, W, prevents water from entering the groove. The 
object of the groove, D, and the lip, W, is to make a waterproof joint to pro- 
tect the switch and cable terminals without the necessity of screw joints or 
gaskets. The bells are all tested with 25 pounds air pressure ; they may be 
entirely submerged in several feet of water without affecting the operation 
of the system. 

The Contact Buttons are made of cast iron. They are about 4£ inches 
in diameter, and, when installed on paved streets, project about five-eighths 
of an inch above the pavement and offer no obstruction to traffic. This is 
sufficiently high to enable the collector-bars to make contact, and at the 
same time to entirely clear the pavement. For open-track installations they 
are substantially mounted in a combination unit as described below. 




Fig. 202. Section of Combination Unit. 
The Combination Units. 

The bell and pan are entirely inclosed in a cast-iron switch-box. This box 
and the contact buttons are made into a complete unit as shown in Fig. 101. 
Each unit consists of three separate castings. The cylindrical cast-iron 
box, which incloses the switch, bell, and pan, is bolted into a recess provided 
for that purpose in the bottom of the spider-like structure, which is a sep- 
arate casting, consisting of box rim, receptacles for the button insulators, 
and supporting arms. The removable lid is the third casting. 

The insulators, A, Fig.202,are made of a special composition, and are ce- 
mented into the tapered cups, B, and supported by the iron plates, C. The 
contact buttons, E, are mounted on top of these insulators and stand, when 
installed, about one inch above the rail. > - 

The four arms, G, are secured to the ties by means of the bosses, H, thus 
reducing to a minimum the labor of leveling the boxes and avoiding the 
necessity of special ties. 



WESTINGHOUSE SURFACE CONTACT SYSTEM. 845 

Mains and Wiring-. 

The positive main or feeder is incased in a lj-inch iron pipe, and passes 
directly through each switch-box, and a tap is made to each switch, the 
switch-boxes being all connected by the iron pipe, as per cut below. 



n n n 




Fig. 203. Track Equipped for Track Return Circuit. 

No additional wires are used to interconnect the coils or contacts of ad- 
jacent switches. 

The Contact Bars are of steel, of ordinary T section. They are sup- 
ported from the car trucks by two flat steel springs and adjustable links. 
These bars are inclined at the ends so that they may readily slide over the 
buttons and over any ordinary obstacle. 

Insulated Return JLinc*. 

In case it is considered best not to use the rails as the return line, insu- 
lated mains for this purpose may be included in the system. It is only 
necessary to install another row of contact buttons, another collecting bar, 




Fig. 204. Track Equipped for Insulated Return Circuit. 

and to use double-pole switches. Fig. 204 illustrates an installation of this 
kind. For all ordinary work, however, the ground return is satisfactory. 



Modifications of the System. 

The description given on the preceding pages applies to the system as in- 
stalled for yard and similar work. Modifications can be made and detail 
matters arranged according to the requirements of each case. 

Street Railway Work. 

The foregoing description applies to installations where the track is open 
(unpaved),and where it is unnecessary to make provision for traffic crossing 
the tracks except at certain points. For street railway work, the switch- 
boxes are preferable installed outside the track, while the buttons are 
placed between the rails and mounted on a light metal tie, as shown in Fig. 
205. 



846 



ELECTRIC RAILWAYS. 



The operation of the system is exactly the same as in open-track work. 
Connecting wires pass from the buttons under the tie to the switch-boxes. 
For double-track work the switches are installed between the two tracks, 
and the boxes may be built to hold two switches, one for each track. 



UNE_or_PAvmG 




CHANNEL IRON. 



Fig. 205. Section of Track Equipped for Street Railway Service. 

"When, as is sometimes necessary, the buttons are placed in a single row, 
it is necessary that the "pick-up" current should be of the same voltage 
as that of the main circuit, and consequently the car-wiring indicated in 
Fig. 206 is used, instead of that shown in Fig. 200. 



STORAGE BATTERY 




Fig. 206. Diagram of Car- Wiring. 

Referring to Fig.206, the method of "picking up" the current is as fol- 
lows : Switch A is first closed ; this completes the circuit from a storage 
battery D, through a small 500-volt motor-generator F, which immediately 
starts. As soon as it is up to speed, which only requires a few seconds, 
switch B is closed ; current then passes from F through the wiring R, to 
contact shoe Q, and then through the switch magnet, as explained on page 
538. Switches A and B are then opened, thus stopping the motor-generator, 
which need only be used to operate the first switch. The successive 
switches are closed, as described on page 842. 

This arrangement of a high-voltage "pick-up " may also be used advan- 
tageously with two rows of buttons where the track is liable to be obstructed 
by mud or snow. 

Sectional Rail Construction. 

For suburban railway or similar service two light rails may be substituted 
for the two rows of contact buttons, as shown in Fig. 207. The cars are 
then equipped with contact shoes instead of bars. These rails are insulated 
from the ground, and may also be insulated from each other wherever 
desirable, thus breaking them up into sections, which are each controlled by 
a single switch. The sections may be made of any desired length to suit the 
conditions. For example, between stations they may be 500 or more feet 
long, while near stations or crossings, where anyone is liable to come in 
contact with the rail, the length of a section may be reduced to 50 feet or 
less. The electrical operation of two-rail installations is the same as when 
two rows of buttons are used. The sectional switches along the tracks are 
entirely under the control of the motorman, and the rails may be rendered 
11 dead " at any moment should occasion arise. 



G. E. CO. SURFACE CONTACT SYSTEM. 



847 




Fig. 207. Sectional Rail Installation. 



GENERAL ELECTRIC SYSTJEIfl OE SURFACE 
CONTACT RAILWAY. 

Following is a description of the surface contact system, as developed b> 
the General Electric Company, and practical application of it has been 
made at Monte Carlo, and at the company's works at Schenectady. The 
description is from a report made by W. B. Potter, Cf . Eng. of the Railway 
Department, and written by Mr. S. B. Stewart, Jr. 

In the operation of electric cars, by the closed conduit surface plate con- 
tact system of the General Electric Company, the current is collected for 
the motor service by means of two light steel shoes carried under the car, 
making contact with a series of metal plates, introduced along the track 
between the rails, automatically and alternately energized or de-energized 
by means of switches grouped at convenient places along the line ; the 
method of the switch control being such that in the passage of the car, in 
either direction, it is impossible for any plate to become alive except when 
directly under the car body. 

In ordinary street car practice, the contact plates are spaced approxi- 
mately ten feet apart, positive and negative plates being staggered, as 
shown in Eig. 208, which admits of but three plates ever being covered at any 
one time by the shoes, which are so designed as not to span more than two 
plates of the same polarity. 

In grouping the switches it is customary to locate them either in vaults 
constructed between or near the tracks, or in accessible places along the 
side of the street, the location and spacing of groups and number of 
switches in each group being based upon a comparative cost between the 
style of vault or other receptacle, and the amount of wire with ducts be- 
tween the contact plates and their corresponding switches. 

The main generator feeder is carried to each vault or group, and auxiliary 
feeders from it are distributed to each switch, the track rail being utilized 
for the return circuit. 



848 



ELECTRIC RAILWAYS. 



The operation or performance of this system can be readily traced out by 
reference to Fig. 208. It will be seen that the current in its passage to the 
motor from the positive generator conductor passes to contact A of switch 
No. 2 through the carbons on its magnet armature (which has been lifted 
by the energized coil G) to contact plates B and C, through the contact shoe 
D to the controller and motor, coming out at contact shoe E to the contact 
plate F, when it passes through the coil of the automatic switch G, ener- 
gizing it and returning by the track-rail H ; thus maintaining contact at 
switch No. 2 armature carbons as long as the shoes remain on the contact 
plates C and F. It should now be noted that contact plate B is energized 



MOTOR <^q /^ 



SB 



3EI 




Fig. 208. Diagram of Connections for Surface Contact Railway Plate 
System, General Electric Co. 

as stated above. As the car proceeds, the shoe D spans the plates B and C» 
thereby keeping the coil of switch No. 2 energized after shoe has left plate 
C, and until shoe E comes in contact with plate J, which immediately ener- 
gizes coil No. 1, thus making the preceding contact plate energized, prepara- 
tory to the further advance of the car. It will be noted in the above 
description of the performance of the system, that we have assumed switch 
No. 2 on Fig.208as closed; it should therefore be understood that an aux- 
iliary battery circuit is necessary in starting or raising a first switch, pre- 
paratory to its armature being held in contact position by the generator 
current, which current energizes the preceding contact plates consecutively 
as described above. 

The battery current is brought into the automatic switch circuit momen- 
tarily during the period of first movement of handle of the controller in 
starting a car, the transition of the controller cylinder also bringing the 
generator current in connection with the battery for a short period cf time, 
thus replenishing the elements sufficiently to operate the switches. The 
battery is also used to supply current for lighting the car, the generator 
circuit being disconnected while the car is at rest. 

Surface Contact Plates. 

The surface contact plates are made of cast iron, with wearing surfaces 
well chilled, designed to be leaded into cast-iron seats in such a manner 
that they are thoroughly secure, but can be readily removed by special 
tongs for the purpose. The seat is imbedded in a wooden or composition 
block set into a cast-iron box, the latter being spiked or screwed to the tie. 
A brass terminal is fastened to the seat for the reception of the connecting 
wire from the switch. See Fig. 209. 



Gr. E. CO. SURFACE CONTACT SYSTEM. 



849 



As stated above, the plates are usually located 10 feet apart for straight 
line work, but somewhat closer on curves, depending upon the radius of the 
curve and length of contact shoe. The negative and positive contact plates 
are staggered with a uuiform angular distance between them, situated not 
less than 10 inches from the track rails. 




Fig. 209. Plan and Section of Track, Monte Carlo, Europe. 
General Electric Company's Surface Contact System, 1898, 

Surface Contact Switch. 

The automatic switches are constructed on the solenoid principle, the 
armature or core of which is employed in closing the contacts as shown in 




Fig. 210, Automatic Switch for Open Conduit, Burface Plate Contact System. 



850 ELECTRIC RAILWAYS. 



Fig 210. The end of the armature core is provided with a pressed sheet- 
steel carbon-holder, for the purpose of supporting the carbon contacts which 
are held in place by bronze clips and cotter pins which can easily be re- 
moved. The pressed-steel carbon-holder can also be detached with little 
trouble by removing the end holding it to the core. Copper plates are se- 
cured to the slate base for contact surfaces and the attachment of feeder- 
wires. The wire of the solenoid is wound on a copper &pool and placed in 
a bell-shaped magnet frame, and a pole-piece, slightly recessed to receive 
the end of the armature core when the switch is in a closed position, is at- 
tached to the top cover, and extends part way down through the winding. 
The recess in the armature increases the range of the magnet, making the 
attraction uniform except at the point of contact where the power increases 
rapidly, thus securing an excellent contact. A blow-out magnet coil is con- 
nected in series with the feeder current, and so situated that the influence 
of its poles is used to rupture any arc that might be formed while the switch 
is opening ; however, this blow-out magnet is used simply as a precaution- 
ary device, as under ordinary conditions there is no arcing, the succeeding 
automatic switch closing the circuit before it is opened by the preceding one. 
Each vault or group of switches should be provided with cut-outs or an 
automatic circuit breaker to protect them in the event of short circuits. 

Surface Contact Shoes. 

The contact shoes are made of " T " steel of light section, the suspension 
for which is an iron channel beam extending longitudinally with the truck 
frame directly under the motors, with a substantial wooden cross-arm at- 
tached to each end for the shoe-supporting casting, the shoes being attached 
to these supporting castings by a spring equalizing device for maintaining 
the shoes at the proper height, and also for making them flexible enough to 
meet any slight variations in the contact plates and track rails. The shoes 
when in their correct position should never drop over one-fourth inch below 
the surface contact plates, and are designed so that they may raise three- 
fourths of an inch or more above them. See Fig. 211. 




Fig. 211. Collecting Shoes, Monte Carlo, Europe. 
General Electric Company's Surface Contact System, 1898. 

A screw adjustment is provided to lower the shoes as they wear away, or 
to take care of any other discrepancies due to wear of parts, etc. ; if they 
are allowed to drop too low they will interfere with rail crossings, causing 
short circuits. 

Storage Batteries. 

It requires for closing the first automatic switch when starting, and for 
lighting the car approximately, ten storage battery elements capable of 35 
amperes rate of discharge for five hours. 



G. E. CO. SURFACE CONTACT SYSTEM. 851 

The batteries are only slightly exhausted in making the initial connec- 
tions through the automatic switch, as it only takes approximately 15 am- 
peres momentarily to perform this work, the battery is immediately 
recharged by current which has passed through the motors. The battery 
serving as a rheostatic step, this momentary charging does not represent 
any extra loss of energy. 

The circuit connections of the battery are accomplished in the controller 
and require no attention on the part of the motorman. 

Car Lighting-. 

The amount of recharging derived from the motor circuits is sufficient to 
operate the automatic switches, but where lighting of the car is done from 
the same battery, an additional recharge is required. 

Assuming that 10 20-volt lamps are used for lighting a car, the batteries 
will need to be recharged every night about five hours, at an approximate 
rate of 25 amperes. 

It is customary to run leads from both the positive and negative terminals 
of the batteries to charging-sockets attached to the under side of one of 
the car sills in a convenient place for connection to the charging-wire. 

A small generator of low potential (30 volts) driven by a motor or other 
method is required for supplying current for recharging the batteries where 
the desired low-potential current is not accessible, and the wiring from the 
charging source should be run to a location in the car-house most convenient 
for connections to the battery sockets. These locations may be fixed either 
in the pits or on posts at the nearest point to where the cars will be sta- 
tioned, and there should be flexible lead wires attached to plugs for connect- 
ing to the battery circuit on the car. In wiring the car-house for the 
battery connections, it would be found convenient to designate the polarity 
of the various wires either by different colored insulation or tags, and the 
plugs at the ends of the flexible leads should be marked plus and minus to 
avoid mistakes in making connections with the car battery receptacle. 

Motors and Controllers. 

The motor and controller equipment used with the surface plate contact 
system is standard apparatus as ordinarily employed for electric car service, 
with the exception that provision is made in the controller for cutting in 
and out the storage battery while starting the car. 

Care of Apparatus. 

As success in the operation of the contact plate system depends largely 
on the care of the apparatus, a few general remarks on the subject will not 
be out of place here. 

Care should be taken that the contact plates are kept clean, and they 
should be frequently inspected, the roadbed being well drained. Any small 
quantity of water temporarily standing over the tracks, however, would do 
little harm, as the leakage through the water would not be sufficient to 
create a short circuit, although this condition should not be allowed to 
exist any length of time. 

The automatic switches should be carefully inspected and all cast-iron 
parts thoroughly coated with heavy insulating paint, and a test for insula- 
tion or grounds be made frequently, and all the parts kept clean and free 
from moisture. 

The contact shoes, in order to prevent leakage, should have their wooden 
supports well protected with a coating of an insulating paint, and should 
also be occasionally cleaned. 

The storage batteries should be properly boxed and should have the cus 
tomary care which is necessary to keep them in good working order. 



DETERIORATION OP UNDERGROUND 
METALS DUE TO ELECTRO- 
LYTIC ACTION. 

Revised by A. A. Knudson, Electrical Engineer. 

In view of the different phases and effects of electrolytic action herein 
presented, it seems essential, where a clear insight of the subject is desired, 
that a reference to the causes which underlie the principles of such action 
should first be given. 

To this end the following is abstracted from the Report of the Electrical 
Bureau of the National Board of Fire Underwriters, Pamphlet No. 5, dated 
August, 1896, viz : This -deals with early discoveries and represents the 
gist of opinions given by several authorities on this subject at that time. 
The balance of this article is treated in a purely practical manner. 

Recent reports show that the destructive effects of electrical currents on 
subterranean metal pipes are becoming sufficiently marked in many parts 
of the country to seriously interfere with the service the pipes are intended 
to perform. 

Underground water mains have broken down, because of faults unques- 
tionably due to electrolytic action; and smaller service pipes have been 
weakened to such an extent as to break at critical moments, when excess 
pressure is put upon them at intervals during a fire. Measurements show 
that conditions unquestionably exist in nearly every district in the United 
States covered by a trolley road, which are favorable for destructive action 
on the subterranean metal work in the vicinity, and pipes taken up in many 
of these districts show unmistakable signs of harmful effects. The general 
nature of this action, and the causes which bring it about, are too often 
seen to need elaborate description. Briefly it may be compared to the 
action which takes place in an electro-plating bath. 

The current which enters the bath through the nickel or silver metal sus- 
pended therein, flowing through the bath and out through the object to be 
plated, ultimately brings about the destruction of the suspended piece of 
metal. Similarly, _ the current from a grounded trolley system flowing 
through the earth in its course from the cars back to the generating station 
selects the path of least resistance,* which is generally for the whole or a 
part of the way the underground mains, and at points where it leaves 
the pipes to reach the station the iron of the pipe wastes away until at 
points the walls become too thin to withstand the pressure of the water, 
and a breakdown ensues. The difference of potential necessary to bring 
about this action is very small, — a fraction of a volt, — and consequently 
in all districts where potential differences are found between water-pipes 
and the surrounding earth, such actions can be assumed to be taking place, 
for dampness, and the salts necessary to produce electrolysis, are present in 
all common soils. 

Whenever, then, a reading is shown by an ordinary portable voltmeter 
registering tenths of a volt with the positive binding-post in electrical con- 
nection with a water-pipe or # hydrant, and the negative binding-post in elec- 
trical connection with an adjacent lamp-post, car track, or metal rod driven 
in the earth, electrolytic action will be found upon examination to be tak- 
ing place at that point which will ultimately result in the destruction of the 
water-pipe, provided that the resistance of the soil is sufficiently low to 
conduct current. 

Referring to the diagram shown in Fig. 1, it is seen that the current will 

gass from the generator out over the trolley line, through the motor to rail, 
ack to the power house. There are obviously two paths open for the 

* The correct statement would be that the current follows the law of 
divided circuits taking all paths offered, rails, earth, pipes, etc., in inverse 
proportion to their respective resistances. 

862 



ELECTROLYTIC ACTION. 853 

current. One a return through the rail, the other a return through the 
earth and any existing gas-pipes, water mains, or other metallic structures 
that may be in its path in the earth. The current flowing through these two 
paths in parallel is plainly inversely proportional to the resistance of these 
two paths. Therefore, in a general way the current will leave the rails at 
A, flowing into the water-pipe at B, and will again leave the water-pipe at 
C and enter the rails. Here, then, is an electric current flowing between 
metallic structures that may be called electrodes at places in the return 
path from the motor to station. All that remains, then, to promote 
electrolytic action is the presence of some solution which will act as an 
elect rolvte 

Observation has shown that the earth, especially in the larger cities, con- 
tains a large percentage of metallic salts in solution, which will readily act 
as electrolytes upon the passage of electric current. It can be seen, then, 
referring to this diagram, that if there exists in the ground sufficient moist- 
ure of some metallic salt, electrolytic action will take place between the 
electrodes A and B, and between the electrodes C and the rails. In the earlier 
electric roads the positive terminals of the generators were connected to 
ground. This arrangement of the polarity of . the street railway has a 
tendency to distribute the points of danger on water-pipes, gas-pipes, cable- 
sheathing, or any other underground metallic structure throughout a large 
and extended territory. By reversing the polarity of the railway generator, 






i * i r imm 




Fig. 1. 

bringing the positive terminal to line and negative to ground, the points 
where the current leaves these metallic structures will be brought much 
nearer the power station, and will be localized in a much smaller area. 

From the electric railway standpoint, the prohibitive expense of the 
requisite addition of copper to make a complete circuit is advanced, to- 
gether with the impracticability of a double-trolley system that is appar- 
ently a necessary concomitant of the metallic return; and these arguments 
have a certain weight. There is no question but that the complete metallic 
return is in the beginning a more expensive installation, but per contra few 
railway companies have any idea of the energy now expended in returning 
the energy delivered by the power station through the poor conductivity of 
the average railway track with its surrounding earth. 

Destructive Effects. — In the process of electrolysis upon under- 
ground pipes there are two distinct phases of action considered as follows: 

A, the lateral effect which is most common, illustrated by Figs. 2, 3, 4 and 

B, the joint effect as shown in Fig. 6. 

A. Where the current is leaving a cast iron main and passing into the soil 
the iron is usually removed in spots, causing pittings of varied size and depth, 
and in aggravated cases, furrows and holes. The pittings are small at first, 
being 1-16 to £ inch in depth and varying in diameter at the surface from I 
to 1 in.; those more advanced are from £ to 1 in. or more in depth, with corre- 
spondingly larger surfaces. 

When a section of cast iron pipe containing such pittings has been removed 
from the soil and exposed to the sun, the graphitic carbon and impurities, 
of which the pittings are filled, become dry and hard and drop out or are easily 
removed. In appearance they are flat, or nearly so, at the surface of the 
pipe and oval in depth, as in Fig. 2. 

These are | of the actual size and shape taken from a pipe. In weight 
they are about the same as dry wood of equal dimensions. 

Where electrolytic action has been severe and the main has burst, the most 
of these impurities will have become detached or washed out by the force of 



854 



ELECTROLYSIS. 



escaping water, and the spots and holes are plainly revealed. Fig. 3 is 
an example of severe action and represents a section of a 6-in. cast iron 
water main taken from a street in Brooklyn, N. Y. The water from this 




Section 



i ACTUAL SIZE 



Section 



action /*^ 



Plan 



Section 



Plan 



o 

Plan 



Fig. 2. 



leak escaped into a canal, did not appear on the street, and the leak was only 
discovered by accident. The length of time the water was running to waste 
is not known. Fig. 4 is a 6-in. section from Reading, Pa. Fig. 5, also from 
Reading, Pa., replaced Fig. 4 and failed again in about one year. 




Fig. 3. Section of 6-inch Cast Iron Water Main Destroyed by •'Electroly- 
sis," removed from Wallabout Place, East of Washington Avenue, 
Brooklyn, N. Y., January 21, 1903. 




Fig. 4. 




Fig. 5. 



ELECTROLYTIC ACTION. 



855 



B. Joint Effect. — This is caused by electric currents flowing through or 
along the pipes lengthwise, and by reason of resistance at the joints, elec- 
trolytic action takes place. Resistance is caused partly by the coating of 
asphalt varnish upon both the inside and outside of the pipe, making a partial 
insulation; and partly by corrosion due to the continued presence of water 
upon the inside, and moisture upon the outside. In such case the current 
shunts the joint, the damage occurring at points where it leaves, causing 
pittings in the iron close to the lead, softening of the lead, resulting in leaks. 
Fig. 6 — the spigot end of a cast iron pipe — shows cause of a leak through 
disintegration of the iron near the lead of the joint ; the furrow of pittings — 
between chalk-marks — extend half way around the pipe; the left end of 
the pipe softened three-eighths of an inch deep was cut with a pocket knife. 
The extent of joint damage depends upon the strength of current flowing in 
a given time. 

The action upon wrought iron or steel pipes differs somewhat from that 
upon cast iron. In the reduction of wrought iron by the process, there is 




Fig. 6. 



a seamy, or shredded appearance, with but little residual carbon. Upon 
steel such as the base of steel rails, or rail chairs (the latter now little used), 
the effect is a melting away of the metal, leaving sharp edges at their bottom 
portions. This effect is found where rails are positive to pipes. 

The action upon lead service pipes, or lead covering upon cables, is some- 
what similar to that upon cast iron so far as pittings and furrows are con- 
cerned, but instead of the graphitic residue there is left in the pittings and 
the surrounding soil a whitish matter consisting of the oxide or residue of 
lead. 



Increase of Current Flow upon Ufa in* due to Bonding- 
Same to Rails or to Negative Conductors. 

Measurements in different cities under varying conditions sbow the in- 
creased flow of current through mains after bonding the mains to the rails, 
from four to ten times above the normal at points near the bonds, in some 
cases very much higher. In one case where 5 amperes maximum was found 
flowing through a 6" main a temporary connection with ammeter and leads 
was made between main and P. H negative with result of over 150 amperes. 
The flow in excess of normal is generally less as the distance is increased 
from a bond. 



856 



ELECTROLYSIS. 



The following tables represent actual measurements made in different 
cities. Measurements made near the bonds, except in No. 3, Table 1. 



Table I. 





Flow in 


Amperes. 






No. of 






Notes. 




Test. 










Normal. 


Connected. 






1 


21.0 


41.7 






2 


21.0 


60.2 


3 bonds. 




3 


30.5 


4.3 


3000 ft. from bond. 




4 


5.0 


128.0 


In negative district 5 mile? 








from P.H. 




5 


6.0 


32.0 


Geneva, Switzerland. 




6 


11.5 


37.5 






7 


80.0 


125.0 






8 


27.7 


45.1 






9 


9.8 


30.5 






10 


6.6 


10.5 







Table II. 



Three Cases Difference of Potential in Average Volts. 



No. 1 
No. 2 
No. 3 




Connected. 



0.25 

0.3 

2.5 



In one city examined by the writer two water mains in front of a power 
house were connected by copper cables directly to the negative bus bar of 
the switchboard. The estimated amount of current flowing by this path was 
found at times to be oyer 1000 amperes; a very much smaller flow has been 
known to damage the joints of mains. 

Current Movements upon Underground Tlaim. — The 
flow of current upon underground mains is proportional to the traffic 
upon the car lines. When railway traffic is heavy mornings and eveningi 
more current output is required at the power house than during hours oi 
light loads. Such changes are faithfully reflected by current flowing in the 
mains. This is illustrated in curve sheet, Fig. 7, where the load line of a 
24-hour log of a power house is shown, and directly above it is placed the 
line of current strength flowing through a 36-inch water main. It will be 
noticed that the rise and fall of current strength upon the water main takes 

Elace at the same hours of the twenty-four as the load changes at the power 
ouse. This effect is more or less common in all cities where electric railways 
with the usual ground return prevail. 

Many instances of railway currents flowing through and across waterways 
have been discovered, where, as is often the case, the power house is located 
upon the banks. 

mr? ne mstance °f such action was discovered at Bayonne, N.J., November, 
1904. At that time current was supplied from the power house in Jersey 
krtVf five miles from the central part of Bayonne. The city is nearly sur- 
rounded by salt water. Mains in streets near the shore and in salt marsh 



ELECTROLYTIC ACTION. 



857 





COMPARISON CURVES 
SHOWING CURRENT VARIATIONS 

ON 36"WATER MAIN 24 HRS. 
AND ALSO 

POWER STATION LOAD 24 HRS. ENDING I 2 MDT. 




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Fig. 7. 



858 



ELECTROLYSIS. 



have been destroyed by the returning railway currents delivering at such 
grounds, causing a heavy loss in piping property to the city by electrolysis. 
There was no point in the city where mains were positive to the rails; 
the flow was from rails to mains, thence to shore and to power house. 
A similar case was discovered by the writer in 1906 during a survey in 
the city of Toronto, Canada, where mains adjacent to the shore of Lake 
Ontario, 2 to 4 miles distance from the power house, were badly damaged. 
The conditions in Bayonne have been changed by the placing of a sub 
power station in that city. 

Such returning currents usually enter the power house through pipes 
used for condensing. Cases have been found where much damage has 
been caused to apparatus in the steam plant. 

Other current movements may be cited where metal bridges cross a river 
as in map, Fig. 8, as was discovered in the city of New York. 

The power house is located near the Navy Y'ard, in Brooklyn. A portion 
of the returning currents, as shown by arrows, flows over the New Y r ork and 
Brooklyn Bridge to Manhattan, thence north to the new Williamsburg 
Bridge by way of underground mains, subway structures and other metals, 
and passes over that bridge back to Brooklyn, thence through mains, to 




Fig. 8. 



rails and negatives, to power house. In this case damage may be expected 
at three points, viz., where currents leave bridge metals on the Manhattan 
side, where they leave pipes to enter Williamsburg bridge, where they leave 
same bridge fof pipes on Brooklyn side. When the two bridge structures 
are connected in Manhattan as proposed, then there will be further changes 
in this direction of current. 

Before the new bridge was built, these currents recrossed through the 
river bed, leaving mains all along the docks on the Manhattan side, for the 
river, and leaving the river for mains or other metals along the docks of 
the Brooklyn side. Traces of these currents have been found as far north 
as 23d St., a distance of over two miles from the Brooklyn Bridge. 

Since the Williamsburg Bridge has been built, nearly all traces of these 
currents flowing north of it have disappeared, showing that the mass of 
metal composing the structure acts as a "short circuit " or path of lower 
resistance and now carries practically all of the returning currents flowing 
from Manhattan back to Brooklyn. 

Electrolytic Effect* upon "Water TOeters. — This is a compara- 
tively recent discovery, and is due to the location in which manv meters 
are placed. Those found damaged by electrolysis in one citv examined have 
in every case been taken from pits in the cellar bottoms of dwellings, stores, 
stables, and near water fronts, where tide water had access. 

The meter pits in many cases are constructed of boards at the bottom 
and sides, with a loose fitting wooden cover; this pit, being the lowest point 
in a cellar, acts as a catch basin and collects the drainage when water is 
present, partially or wholly submerging the meter very often in stagnant; 
water. 



ELECTROLYTIC ACTION. 859 

The quality of such liquid makes a convenient electrolytic for any current 
of electricity. Railway or other current passing to the meter through 
the service pipes, and out of the meter into this liquid, in time causes a 
rupture of the thin iron shell of the small sizes where the top is iron. 

The actual weight of iron lost through electrolysis by a 4-inch meter located 
in a ferry house and subject to tide water was in about six years 15 pounds. 
This meter was near a power house where the p. d. at times reached 25 
volts, with mains positive to rails. These severe electrical conditions have 
since been modified by the railway company improving their track return. 

Meters constructed of bronze have had holes eaten through their base 
where resting on damp soil in cellars. Such grounds often attract trolley 
current through the service pipes.* 

Danger from Tire or JE x.plosions. — Currents entering buildings 
which contain explosives, through water or gas mains, are dangerous owing 
to sparks when gas mains are separated or the cross-connecting and discon- 
necting of pipes containing current, by movable metals is made. 

The usual course of such currents is to enter a building on one pipe and 
pass out upon another when a cross-connection is made between the two 
systems anywhere inside of a building. When the connection is broken the 
spark appears, and it may appear at any point in the building, possibly 
in the presence of explosives. 

Bonding the pipes together where they enter the building has proved 
effective as a temporary remedy in some cases. As no two cases are alike, no 
particular rule can be laid down as a remedy. Where the conditions are 
considered dangerous the services of a specialist should be engaged. 

Electrolysis in Steel Frame JSuilding-s. — While no instance of 
serious damage to a steel structure through the disintegration of supports 
caused by electrolytic action can be cited, still this question is now receiving 
attention by architects and others, and methods for safeguarding against 
such corrosive effects are being applied. One such instance of protection is 
the new New York Times building. In one of their publications the fol- 
lowing is stated in reference to this structure: 

"The danger that in case of the steel frame rusting the disintegration 
of electrolysis would hasten the process of dissolution so much as to make 
structures of this kind prematurely unsafe through the destruction of their 
supports, was recognized in time to permit of ample safeguarding in the 
case of the steel frame of the Times Building. 

" It is axiomatic that columns to which moisture has no access will not be 
impaired by rusting, and that those effectually insulated from vagrant 
electrical currents will not be affected by electrolysis. The first considera- 
tion was to keep the basements dry; hence the thorough waterproofing 
and draining of the retaining walls already described, which was also carried 
under the floor of the pressroom, occupying the great area of the sub- 
basement. As a further safeguard, all the steel members up to the street 
level are incased in Portland cement mortar to the minimum thickness of 
three-fourths of an inch. This is effectual protection against rust deteri- 
oration. Under these conditions electrolytic disintegration is deemed 
impossible, but the probabilitv of its occurrence in even microscopic degree 
is rendered still further remote by as perfect insulation as can be provided. 
There is sufficient grounding to relieve any electrical tension which may 
exist in anv part of the steel frame by drawing off the current at points 
where electrolvtic action cannot be set up. This also makes i it lightning- 
proof to the extent to which it is possible to impart that quality to a Duiid- 
ing. " 

For results of experiments by the writer upon metals in concrete, see 
February, 1907, Proceedings of the A.I.E.E. in a paper. entitled Electro- 
lytic Corrosion on Iron or Steel in Concrete." discussion in April numoer. 

Current Swapping-.— The transfer of currents between the tracks ot 
different companies through underground routes, often by way of mains, 
is of frequent occurrence, particularly if the lines parallel even for a short 
distance. 

Th's is more noticeable at the terminus of suburban lines, but also pre- 
vails in cities. 



* Case illustrated in abstract of the writer's report for Providence, R.I. 
in Water and Gas Review, N.Y., March, 1907. 



860 ELECTROLYSIS. 

One case in a city where the termini of two different lines were but a few 
feet apart, showed upon measurement a heavy delivery at times, leaving 
tracks of one company for tracks of another, soil conditions continually 
wet, consequently a large percentage was flowing through soil and the 
water mains. Another case near suburban terminals of two railway 
lines about 600 feet of 6-inch water main with a number of service 
pipes were practically destroyed by electrolysis; the main acted as an inter- 
mediate conductor; the pipes were destroyed under the tracks of one road 
by the currents from the other. An attempt to remedy was made by bonding 
the two tracks together. This method cut the potential difference be- 
tween mains and rails from 6.7 volts down to about 2 volts. After six 
months' standing no further breaks in the mains have occurred. This plan 
was considered of value in affording temporary relief, but is not now of 
importance as the tracks of the two lines have been joined by new tracks 
in a cross street. 

Current swapping is more frequent than generally supposed, and is caused 
largely by local conditions, such as swamps, rivers or other waterways to 
which a company's tracks connect and are grounded, offering paths which 
attract their own as well as foreign currents. In the case cited of damaged 
mains, the flow was from newly constructed tracks, seeking grounds on another 
road where rails were in wet soil. Usually, however, the cause is due to 
opposite reasons, viz., currents seeking a track return of lower resistance. 

A well^constructed road bed on suburban lines will often avoid such 
opportunity for grounds, and current swapping. 

Alternating-Current Electrolysis. 

The possibility of damage to underground structures by alternating 
currents has been investigated by several authorities both in this and 
foreign countries. As no actual damage has yet been discovered so far as 
known to the writer, these investigations are necessarily confined to labor- 
atory experiments. The following abstracts from a few papers give a fair 
idea of what is known of the subject, and where further information may be 
obtained. 

The Ultimate Solution of the Electrolysis Problem by S. P. Grace, paper 
before the Pittsburg, Pa., Branch A.I.E.E., read December 12, 1905: 
" Our many hundreds of laboratory tests have shown us that the electrol- 
ysis to be expected from alternating currents is by no means negligible, 
and that while it is far less than that encountered with direct currents, in 
practice we should anticipate that it is only a question of time until its 
action would destroy many millions of dollars of underground metallic 
structures." 

From transactions of the Farady Society, Volume I, February, 1906, Part 4. 

Alternating -Current Electrolysis as shown by Oscillograph Records, 

by W. R. Cooper, M.A.B. Sc, read October 31, 1905: 

Photographic reproductions of oscillograph records are given illustrating 
results of his investigations. The author also gives results of several other 
investigators of this subject. 

From transactions of the Farady Society, Volume I, August, 1905, Part 3. 

Alternate Current Electrolysis by Prof. Ernest Wilson, paper read 

July 3, 1905: 

The author gives results upon different metals at different frequencies 
and in different solutions, and begins by saying, "It is well known that if 
an alternate current be passed between metal electrodes in an electrolyte, 
electrolysis may take place." 

The Electrolysis Problem from the Cable Manufacturers' Standpoint, by 
H. W. Fisher, paper before A. I. E. E., Pittsburg, Pa. Branch, read 
December 12, 1905: 

44 My experiments have not been very comprehensive, but I have found 
under certain conditions, destructive electrolytic action may occur with 
alternating currents operating at a frequency of 60 cycles per second. 

The solution I employed for the electrolyte was water containing common 



ELECTROLYTIC ACTION. 



861 



salt and salammoniac, all of which may occur in and around duct systems. I 
found that with a current density of 0.1 ampere per sq. in. of lead, there 
was no electrolytic action. 



Amperes per sq. in. 
of Surface. 


Lead Destroyed per 

Ampere, per hour, 

per sq. in. 


3.04 
11.8 
17.9 


.004 Grammes. 

.136 

.237 * " 



with a frequency of 25 cycles per second, the alternating 

current action would probably be greater than shown by my tests." This 
latter statement agrees with Prof. Wilson's tests above referred to, where 
he says, " It will be seen from the table that the total diminution in weight, 
which was equally distributed between the two plates, in a given cell is 
nearly twice as great at low frequency as it is at high frequency." 

Remedies. — Several methods have been suggested for counteracting 
the evil effects of electrolysis. 

The insulated metallic circuit. 

The underground, known as the "slotted conduit," has been in success- 
ful practical use in the borough of Manhattan, city of New York, some 
ten years, and for a still longer time in the city of Washington, D. C. 

The double overhead trolley has been in successful practical use in the 
suburbs of the city of Washington for some years, and in the city of 
Cincinnati, Ohio, since 1889, and more recently has been established in the 
city of Havana, Cuba. 

Both outgoing and return conductors of either construction are insu- 
lated; where there is no connection to the rails or ground the currents which 
propel the cars are confined to their respective conductors, consequently 
no damage to underground metals is possible. 

Improved Track Return. 

Next to the double trolley, this method is probably the best, although 
a modification of the trouble. 

In some cities a large amount of copper for returns has been placed for 
this purpose, as well as heavy double bonding at the rail joints. The expense 
involved in providing copper returns sufficient to give a fair degree of pro- 
tection to mains, would in most cases be considered unnecessary by the 
railway companies, unless compelled by law. 

Bonding Mains to the Track Circuit. 

This has been done in some cities for the purpose of protecting a positive 
area where electrolysis was found to be acute; usually this is near a power 
house. Some effects of such bonding have been mentioned. 

While this may protect from injury the immediate area where such con- 
nections are made, it is likely to aggravate joint corrosion by the increased 
flow which has been pointed out. 

Meters. — A remedy for exterior electrolysis upon meters is to place 
them in iron or other receptacles under a sidewalk where they will be free 
from liquids or damp soil. Such methods are used in the cities of Cleveland, 
Ohio; Richmond, Va.; and Louisville, Ky. Official reports show in such case 
they are in no danger from electrolysis, or from freezing, and are easily 
accessible for reading, and removing when desired. 

Insulating* Joints in Mains. — This is a further attempt at remedy, 
and much attention has been given to this phase of the subject by rail- 
way companies in Boston, Mass., with the Metropolitan Water Works 
cooperating. 

The Metropolitan Official Report dated January, 1905, contains much 
information on this and other attempts to stop the current action which 

* In this case a large hole was eaten through the lead, and the surface 
exposed to electrolytic action was nearly a square inch. 



862 



ELECTROLYSIS. 



was causing great damage to their mains. Several insulated joints have 
been set, and are found to be fairly efficient in arresting the flow of current 
through a main. Usually, however, it is at the expense of diverting flow 
into other mains. 

In one case an experiment was tried of two joints in a 48-inch main, one 
insulated with wood and the other with rubber. A measurement made 
when the writer was present showed the one with wood insulatioD 
than that of the rubber after six months' use. 

The following sketch will illustrate the tests. 



*kEi 



WOOD 
/INSULATION 



No. I 



RUBBER 
INSULATION 




Fig. 9. 

Ammeter test between A and C gave 60 to 110 amperes, representing 
the flow if there were no joints. Between A and B, flow passing through 
No. 2 (rubber) 0.6 to 1.0 ampere. Between B and C, flow passing through 
No. 1 (wood) 0.1 ampere. This reading should not be taken as the true 
value for all cases owing to varying conditions. The efficiency of either one 
for stopping current was in this particular case very good. 

Fig. 10 represents a pair of insulated joints ready to place in a 6-inch main. 
They are made up of wood slats driven in the hubs; a flange of wood rests at 




Fig. 10. 



the bottom of the hub. The three screw posts are for wires which are led 
to the surface for testing efficiency of each joint. 

Fig. 11 shows the same joints connected in the main at the bottom of 
the pit, and wirer run to ammeter. Before the pit was filled in, wires were 
run through small pipe to the surface of the street, the ends being secured 
by cap, for future testing. 

A test with low reading ammeter failed to show any sign of current pass- 
ing through either joint, when first set. After two years one joint shows 
leak of 0.1 ampere; the other perfect, short circuit around both joints shows 
5 amperes. 

A water pressure of 110 lbs. to the square inch was put on this main, and 
neither joint leaked. Two joints were used in case one failed, and to pro- 
vide opportunity for testing efficiency of either one. 

Experience in Boston is, joints of wood are preferable to those of rubber, 
on the ground of expense, and equally efficient for stopping current flow. 

Surface Insulation. — Wrapping a 48-inch main with burlap 
saturated with asphalt cement applied hot, is another attempt to stop 
electrolytic action near a power house. 

After two years' trial, results show, after careful examination, this method 
to be unsuccessful, and it has been abandoned. This class of insulation has 
long been known by electricians to be no -protection to metals where subject to 
continual moisture. 



ELECTROLYTIC ACTION. 



863 




Fio. 11. 



Summary. 

1. The tendency of return currents on long lines five to ten miles from a 
power house is to leave the tracks near a terminus and seek "grounds." 
This may be by way of other tracks, by way of underground mains, or by 
water routes. Recent tests show that a very good return construction will 
not wholly prevent such diversion of currents. 

2. Low spots in a company's road bed, where rails are in contact with 
wet soil, offer an attractive outlet for their own, or foreign, currents. 

3. Bonding rails to mains always invites heavier flow of currents to the 
mains, with corresponding increase of damage at joints. 

4. All establishments manufacturing or carrying explosives should be 
often examined, particularly if contiguous to electric railways, and if metal 
pipes of any kind pass to them the passing of straying currents into and 
through such establishments is quite possible and oftentimes dangerous. 

5. Protection of metal foundations of important structures, such as tall 
office buildings, bridges, etc., from electrolytic action should be well con- 
sidered before their construction and occasionally tested after construction. 

6. Current Swapping 1 . — The cause for current swapping between 
railway tracks should be sought out and removed where possible, especially 
in cities or towns where underground mains are likely to be included as 
conductors to their detriment. In one case bonding of tracks of two 
companies together afforded relief. 

7. Insulated .Joint* in water mains have proven effective to stop cur- 
rent flow in some cases, but often at the expense of diverting it to other 
mains. 

8. No complete cure for electrolysis has been discovered where the 
grounded return is in use. 



TRANSMISSION OP POWER. 

Revised by F. A. C. Perrine. 

The term " Transmission of Power," as used by electrical engineers, has 
come to have a conventional meaning which differentiates it from what 
must be considered its full meaning. Any transmission of electric current, 
for whatever practical purpose, whether for lighting, heating, traction, or 
power-driving, must of course be a transmission of power ; but the conven- 
tional meaning of the term as now used by electrical engineers and others 
eliminates many of these objects, and is held to mean simply the trans- 
mission of electric current from a more or less distant point or station to a 
center from which the power is distributed, or to power motors at different 
points in a factory or other installation. While the distances over which 
electric current is transmitted for arc lighting in some large cities and in 
many small places far exceed the length of line of the ordinary or average 
power transmission, yet the former is never alluded to as transmission of 
power. The same condition obtains with traction, the transmission of cur- 
rent covering miles of territory, and yet it is only alluded to as power 
transmission when the current is transmitted from a central point to vari- 
ous sub-stations from which it is distributed. 

Many engineering features of transmission of power will be found treated 
under the separate heads in their respective chapters, and the following is 
a short resume of the subject matter. 

Building-. 

Structural conditions and material. 

Iflotive Power. 

Water power : Turbines, etc. 
Steam power : Boilers and appliances. 
Engines and appliances. 
Shafting and pulleys. 
Belting and rope drive. 

Generators. 

Dynamos : Direct current. 

Alternating current. 
Double current. 

Transmitting* Appliances. 

Switchboards. 

Transformers, step up. 

liotaries. 

Cables and pole lines. 

Conduits, etc. 

Distributing* Appliances. 

Sub-stations and terminal houses. 

Transformers, step down. 

Switchboards, high tension and secondary. 

Rotary converters. 

Direct current motors. 

Synchronous motors. 

Induction motors. 

Frequency changers. 

Distributing circuits. 

864 



DISTRIBUTING APPLIANCES. 



865 



Much has been written regarding the relative values of the different 
methods of transmitting power, and comparison is often made between the 
following types, i.e., 

a. Wire rope transmission. 

b. Hydraulic transmission, high pressure. 

c. Hydraulic transmission, low pressure. 

d. Compressed air transmission. 

e. Steam distribution for power. 
/. Gas transmission. 

g. Electrical transmission. 

All of the first six methods listed have so many limitations as to distance, 
efficiency, adaptability, elasticity, etc., that electricity is fast becoming the 
standard method. The matter of efficiency alone at long distances is one 
of the best arguments in its favor, and we take from Prof. Unwin's book, 
" Development and Transmission of Power," the following table of the effi- 
ciencies such as have been found in practice. 



i 



System. 


Per Cent Efficiency at 


Full Load 


Half Load 


Wire rope 


96.7* 

55 

50 

51 

75 

73 


93.4 * 


Hydraulic high pressure 

Hydraulic low pressure 

Pneumatic 

Pneumatic reheated virtual efficiency . . 
Electric 


45 
50 
44 
64 
65 







For short distances out of doors, transmission by wire rope is much used 
both in the United States and Europe, and where but few spans are neces- 
sary, say less than four, it is obvious that the efficiency is very high. 

Hydraulic transmission is in considerable use in England, but except for 
elevator (lift) service is in little use in the United States. 

Pneumatic transmission is in wide use in Paris, but not so for general 
distribution in the United States, although for shop transmissions for use 
on small cranes and special tools is making good progress, the principal 
usage being for the operation of mining drills, hoists and pumps. 

Electrical transmission is so elastic and so adaptable to varied uses, and 
has been pushed forward by so good talent, a not small factor, that its pro- 
gress and growth have been simply phenomenal. In one place alone, that 
of traveling cranes for machine shops, it has revolutionized the handling 
of material, and has cheapened the product by enabling more work to be 
done by the same help. Indeed the great increase in size of units which is 
such a distinguishing characteristic of modern engineering has been ren- 
dered possible by the capacity of the electric traveling crane for lifting 
great weights. 

Electric Power Transmission may be divided into two classes, i.e., long 
distance, for which high tension alternating current is exclusively used ; 
and local or short distance transmission, for which either direct current or 
polyphase alternating current are both adapted, with the use of the former 
largely predominating owing perhaps to two factors: a, the much earlier 
development of direct current machinery, and b, to the fact that a large 
number of manufacturers are engaged in the building of direct current 
machinery. Both types of current have their special advantages, and 
engineering opinion is, and will probably remain, divided as to which has 
the greater value. 

* Per span. 



866 TRANSMISSION OF POWER. 

Long distance transmission is now accomplished by both three-phase 
three-wire, and by the two-phase four-wire systems, with the former pre- 
dominating for the greatest distances, owing to economy of copper. 

Every case of electric transmission presents its own problem, and needs 
thorough engineering study to decide what system is best adapted for the 
particular case. 

Limitations of Voltage. — While 10,000 volts pressure was used with some 
distrust for a time previous to 1898, since that time voltages up to 70,000 
volts have been and are still in use with substantial satisfaction, and plants 
using voltages of 80,000 and 100,000 are under construction. 

Properly designed glass or porcelain insulators, made of the proper 
material and tested under high pressure conditions, cause little trouble 
from puncture or leakage. The latter is its own cure, for the reason that 
the leakage of current over the surface of the insulator dries up the mois- 
ture. Dry air, snow, and rain-water are fairly good insulators, and offer no 
difficulties for the ordinary high voltages. Dirt, carbon from locomotive 
smoke, dust from the earth, and such foreign material that may be lodged 
on the insulators, are sure to cause trouble. In the West and some sections 
of the East many insulators are broken by bullets fired by the omnipresent 
marksman. 

At the lower voltages glass makes a satisfactory insulator, as the eye can 
make all necessary tests ; but it is so fragile that porcelain is more com- 
monly used. It is not safe to accept a single porcelain insulator without a 
test with a pressure at least twice as great as that to be used. 

Mr. Ralph D. Mershon of the Westinghouse Electric & Manufacturing 
Company made a long series of tests at Telluride, Col., on the high-pressure 
lines in use there. With a No. 6 B. & S. copper wire he found that at 50,000 
volts there will be a brush discharge or leakage from one wire to the next 
that can be seen at night, and makes a hissing noise that can be heard a 
hundred feet or more. This brush discharge begins to show at about 20,000 
volts, on dark nights, and increases very rapidly, as does also the power 
loss at 50,000 volts and higher. This loss depends upon the distance apart 
of the conductors and their size. For these reasons, wires should be kept 
well apart and be of as large size as other properties will allow. 

The wave form of E.M.F. used also influences the brush discharge, being 
the least in effect for sine wave curves of E.M.F., and being much increased 
by the use of the sharp, high forms of curve. 

In regard to the frequency to be adopted for power transmission, one has 
to be governed by the case in hand, and the commercial frequencies avail- 
able at economical cost. 

SPECIAL FEATURES OF DESIGN »XJE TO TRAIS- 
IKISSION LOE REi|UIRE9[Ei\I§. 

While the general requirements for the design of a power plant and line 
for long distance power transmission are practically similar and theoreti- 
cally identical with those for other electrical installations, at the same time 
special features are important. These are due to the character of service 
required, the size of the plants, high voltage, and location of the plants. 
The general features of design have already been considered in this 
book, and a short resume is given on page 864. Below, attention is called 
to special requirements to be considered in power transmission instal- 
lations. 

Building^. — Transmission generation stations are commonly located 
in relatively inaccessible locations, and the size of unit is therefore limited, 
whereas the total capacity of the station may be great and the current is 
transmitted at high potential. 

Transportation and labor conditions must be carefully studied, as the 
neglect of this precaution may readily involve an underestimate of no less 
than 25%, and has often so resulted in estimates otherwise correct. This 
is especially true as regards the use of patented or special building con- 
struction, which might result in savings where competent workmen are to 
be had, but which actually result in excessive cost where the amount of 
work to be done is not sufficient to import men familiar with the type of 
construction. 



SPECIAL FEATURES OF DESIGN. 867 

Roofing*. — The buildings should be entirely fireproof, and whereas this 
Is easily taken care of by avoiding wood altogether in the interior construc- 
tion, supports and walls of the building, a mistake is often made in choos- 
ing a roofing which must be laid upon planks. Such construction has 
frequently resulted in disastrous fires at power plants otherwise inde- 
structible. 

Heating-. — Where temperatures do not fall to less than 10° F. the 
waste of energy from the machines is commonly sufficient for heating ; 
where lower temperatures are encountered, special provisions must be 
made for heating. Boilers for steam- or water-heating fired in cellars 
accessible from the outside of the building only are the best. 

Outlet* for Higrh-Tension Wires. — In buildings where the tem- 
perature falls below freezing, sewer pipes with large openings for high- 
tension wire outlets should not be used on account of the excessive draft 
through these openings. A number of systems for high-tension wire out- 
lets are described in Transactions of American Institute of Electrical 
Engineers, Vol. 22, p. 313 ; Vol. 23, p. 578 ; Vol. 25, p. 865. Special methods 
for carrying out some of these plans have been designed and are described 
in the catalogues of the porcelain insulator manufacturers. 

Eig-htning* Arrester Protection. — Arresters should be considered 
as belonging to the line and not to power house, and lightning] arresters 
should not be installed in the power house itself, but in a separate neigh- 
boring enclosure especially erected. Arresters are to be considered as a 
means for preventing line disturbances entering the power house in any 
manner. 

Separating* Generator and Transformer Rooms. — The only 
reason for attempting to separate generator and transformer rooms is on 
account of the oil contained in the transformers which may become the 
source of fire hazard. If, however, the oil transformer is properly enclosed, 
separate buildings are unnecessary. See Transactions of American Insti- 
tute of Electrical Engineers, Vol. 23, p. 171. 

Auxiliary Building's. — No estimate on an isolated transmission 
power house is complete which does not include houses for the married 
employees, a central mess house with reading room, assembly room and 
offices, and stables for the accommodation of horses. Unless these features 
are properly taken care of, it will be difficult to retain satisfactory em- 
ployees and to operate the plant economically and continuously. 

MOTIVE POWER. 

Water Power, — Load factor and total capacity are closely related 
in questions of design and revenue. 

The effect of yearly load factor on revenue is shown by the curves below. 

By reducing all yearly load rates to a K.W.H. basis we are enabled, 
through the use of these curves, to determine the total revenue to be 
derived when we know the total yearly K.W.H. that any variable water 
supply may sell when applied to the operation of any set of variable loads, 
and hence the value to the plant of an annual storage. 

In variable loads there is a variation in the daily load factor as well as in 
the annual load factor. 

STORAGE RESERVOIRS. 

Apart from Plant. — These reservoirs serve to aid in properly sup- 
plying variable annual load factor, but on account of plant distance, cannot 
take care of daily variation in load factor. 

Adjacent to Plant. — When a daily variation of load factor is to be 
met, revenue may be increased by reservoirs near the plant that may be 
called upon for conserving water flowing at low power periods and deliver- 
ing it at peaks, which cannot be done by distant storage. 

Auxiliary Power. — The value of any plant should be based, not 
upon the total maximum or minimum capacity, but upon the K.W.H. sala- 
ble, and in obtaining the maximum K.W.H. capacity it is often possible to 
increase this by auxiliary machinery to be used at the low water periods or 



868 



TRANSMISSION OF POWER. 



at periods of customer's peak. Neglecting the study of this factor often 
results in estimates of plant value unnecessarily low. 

Auxiliary power may be obtained from steam, water, or gas, as is obtain- 
able at the most satisfactory cost, not necessarily the lowest price. The 
most satisfactory cost is that which yields the greatest annual K.W.H. 
output from the total plant at the lowest cost. 





































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Fig. 1. Curve for reducing cost of power per maximum horse-power per 
annum in dollars to cost per kilowatt-hour in cents at various load factors. 



Ditches, Canals and other Conduits. — Construction of open 
ditches is generally the cheapest method where water is to be carried a long 
distance over ground fairly uniform and capable of being made tight. 
Ditches are distinguished from canals mainly by size ; the term "canal" 
being applied to large open water carriers, and is particularly applied where 
the sides and bottom are reinforced for reducing friction or maintaining the 



SPECIAL FEATURES OF DESIGN. 869 

structure. Where ground is of such character as induces leakage, or where 
surface evaporation is excessive, it is necessary to carry water through pipes 
or through enclosed conduits. In such case the conduit is run full and under 
pressure, which means that the top of the conduit must always lie below 
the hydraulic gradient. Economy in construction is obtained by running 
close to the hydraulic gradient and concentrating the fall near the power 
house. 

Pipe JLines or Penstocks. — Pipe lines near the power house, where 
a rapid fall greatly exceeding the slope of the hydraulic gradient is allowed 
for useful head, are generally called penstocks. Such lines are built at as 
rapid a fall as possible and constructed of various thicknesses or strengths 
to conform to the increased water pressure. 

JFish JLadders. — In all streams where there are any fisheries or where 
the government is introducing spawn or small fish, the law requires the use 
of fish ladders, which must be included in the estimate on any such plant. 
No standard type of ladder has ever been permanently adopted, and the 
construction must depend upon the character of fish they are intended to 
serve. Salmon will go up ladders requiring jumps of from two to four feet; 
but smaller fish, shad, trout, etc., must be provided with ladders with jumps 
not over one foot. These ladders consist of flume boxes rising from the 
river to the point above the dam, each box rising slightly above the preced- 
ing one from the river, and each allowing a relatively quiet flow near the 
dam into the next one. 

Cffect of Silt on Storag-e. — Most streams carry more or less silt, 
and have been known to carry as high as 13 tons of silt per second foot of 
water per day. Under such circumstances the capacity of the storage is 
often reduced, and where such conditions are encountered, only a small 
proportion of the total storage area can be relied upon, unless special means 
are provided for removing the silt. Dams will fill less rapidly with silt if 
the surplus water during floods is carried off through the bottom of the 
dam rather than over the crest. 

Choice of Head. — It is an error to subdivide heads which are not 
more than 2,000 feet in height, since pipe can be readily obtained to handle 
2,000 feet head, and sub-division of the head not only increases the cost of 
installation, but also the cost of operation. This is true, not only for high 
heads, but for low, as the building of a high dam in place of two low ones 
more than doubles the available storage. Exception to this is when rela- 
tively constant load is to be operated, in which case the increase of storage 
does not increase the total yearly K.W.Hs., and the cost of the high dam, 
which is about double that for two low dams, is unwarranted. Here, as 
always, the construction of the plant should depend upon the total yearly 
K.W.Hs. salable, without especial reference to the total yearly K.W.Hs. 
available for sale, unless it may definitely be shown that the surplus yearly 
K.W.Hs. salable at the time of construction can be increased by reason of 
having a greater available quantity of energy. 

Estimate of Water. — Excepting at the head waters of streams or 
where an actual gauging is obtainable, it is unwise to estimate any stream 
in the United States at a minimum greater than .25 per second foot per 
square mile of drainage area. In the east and south this minimum is pro- 
duced by the summer drought, which is also true on the Pacific Coast. In 
the west and north this minimum is produced by the cold winter weather 
when the streams are frozen and flow diminished below that of any other 
period of the year. The best estimate of water flow can be obtained where 
accurate gaugings have been made by a careful and experienced govern- 
ment office. Even these must be modified by a study of the local conditions 
and of the rain fall. Where gaugings for a considerable period of time are 
not obtainable, an approximate estimate of the water flow can be obtained 
by a study of the rain fall and then compared with gaugings in a similar 
locality, though the extreme minimum cannot be obtained in this manner, 
and a minimum considerably below that indicated by the rain fall should 
be taken. 

Coal Power. — Coal power for transmission is only practical in one or 
two conditions: First, where waste coal is obtainable ; and secondly, where 
inaccessible coal can be marketed by transmission. Coal is primarily a 
domestic fuel and material for chemical reduction. Its continued use for 
power is only a question of relatively few years, excepting where coal can 
be obtained which is not adapted to other purposes, or where it cannot 



870 TRANSMISSION OF POWER. 

readily be made available by other means. As an auxiliary power material 
it is well adapted for supplementing the deficiencies of water power plants, 
or for handling the peaks of loads, thereby enabling a greater total yearly 
K.W.H. output from any given installation. 



Frequencies. — This subject is much confused at the present time. 
Twenty-five cycles has been a standard frequency for power work as it is 
well adapted to use of the present type of synchronous rotary converter. 
It has never been well adapted to lighting work or to the induction motor, 
and at the present time, with the strong development of single-phase rail- 
road working, it is a questionable frequency for that service. A frequency 
of 60 cycles is perfectly adapted to all lighting needs, motor generator 
sets for conversion to direct current, and for inductor motor converters, as 
well as the newer types of synchronous rotary converters. The effect of 
increasing the impedance of the line at 60 cycles has not given added 
trouble over that found when low frequencies are used, excepting in the 
case of lines delivering over 10,000 K.W. In any case of transmission the 
frequencies must be determined by the market to be served, both for the im- 
mediate future and the distant future, where power is available to con- 
template increased development. A choice of frequency different from 
60 cycles must be well warranted by the circumstances, or not adopted. 

Voltag*e. — Direct generation of high voltage should not be contem- 
plated, excepting where the present and future market can be reached at 
not over 500 volts per mile. When direct generation is not contemplated, 
standard 2300 volt generation is to be preferred, unless the plant to be in- 
stalled contains great capacity, in which case 6600 volt generation is pref- 
erable. 

Regulation. — Close regulation for inductive loads should at all times 
be preferred, but in large stations, where the load is relatively steady, it 
should be remembered that a change to 1,000 K.W. on a 10,000 K.W. machine 
represents only one-tenth the variation of what the same change in load 
means in a 1,000 K.W. machine. 

Speed. — High speed is always preferable in power houses for transmis- 
sion work. It should be remembered, however, that for impulse wheels the 
correct speed of the wheel buckets is about one-half spouting velocity of 
the water, and in consequence, all machinery should be installed to allow 
a speed practically equal to full spouting velocity of the water when the 
load goes off. 

For turbine wheels the speed is approximately 70%, the spouting velocity 
of the water, and for no load does not increase more than 50%. 

Size of Units. — While large sized units are preferable, units should 
not be chosen which are greatly underloaded for long periods of the day, 
nor should units be adopted which do not allow the installation of at least 
one spare at the maximum load. 

"Use of Direct Current. — In the United States direct current to-day 
is practically unused. In Europe it is somewhat used in Italy and Switzer- 
land. The success obtained by the use of direct current where it has been 
employed, and the recent developments in the design of direct current 
machines warrants its future employment, but as direct current is only used 
in constant current circuits the line loss is constant, and is only warranted 
where there is constantly flowing a surplusage of water which cannot be 
conserved. 

TRANSMITTING APPARATUS. 

Switchboards. — For transmission plants which run to very high line 
voltage, it is preferable, even in comparatively small stations, to install the 
high tension oil switches in such a manner as will not tend toward the 
destruction of the plant should they fail and burn. The lower tension gen- 
erator switches may be installed in the line of generator leads without 
attempting to bring the generator leads to one central point for re-distribu- 
tion of the current from that point. These provisions can be carried out by 



SPECIAL FEATURES OF DESIGN. 871 

means of the installation of centrally located distant control switches, 
while keys or switches are installed for operating the high and low tension 
switches, without bringing any current above 120 volts to the operating 
board. 

TRAHSJFORUCERS. 

Single or Multi-Phase. — In large installations multi-phase trans- 
formers reduce the number of units to be taken care of and the complexity 
of the wiring. In the smaller installations they involve a greater pro- 
portion of spare units. Accordingly multi-phase transformers are to be 
considered preferable to single phase, excepting where their size calls for 
too much added machinery in the spare units. 

Protection agrainst JTire. — A large majority of the transformers 
used in transmission plants to-day are oil filled. Experience seems to 
indicate that this does not increase the fire hazard, excepting in so far as 
this is due to the presence of a large quantity of oil. When oil can be kept 
cool and within the cases of the transformers it does not increase the 
fire risk. It may be kept cool by circulating water rapidly through the 
cooling coils in the transformers, though a separate enclosure of each trans- 
former within a space where water may be sprayed on the outside of the 
case, or the enclosure filled with water, is a surer means than that of 
relying on the circulating pipes, whenever any serious accident has occurred. 
Accordingly transformers should be enclosed where water can readily flow 
on them without damaging the remainder of the machinery. Transformers 
through which the oil is circulated and the oil cooled outside the trans- 
formers constitute a greater fire hazard than those in which the water 
circulating coils are immersed in the oil within the case. 

Another way is to provide a large tank into which the oil from the trans- 
formers may be drained in case of fire. 

POLE MXES. 

Rig-lit of Way. — For high tension work private rights of way are 
to be preferred and result in final economy in operation. Rights of way 
adjacent to steam railroads result in difficulty with the insulation on 
account of the coal smoke and are not to be sought. It is not generally 
practical to obtain a right of way so wide that in case the pcle or tower line 
fall it will fall entirely within the right of way. Width of from 50 to 100 
feet is entirely practical, provided the additional right is given to cut 
diseased trees within an additional 50 feet on either side of the right of way. 

Character of construction has already been described under the following 
headings: Wood poles, towers, cross-arms, pins, insulators, attachment oi 
insulators. 



STORAGE BATTERIES. 

Revised by Lamar Lyndon. 
Theory and General Characteristics. 

Elements. — The form of storage battery now in general use is that in 
which the electrodes are of sponge lead (Pb) and lead peroxide (PbC>2) 
which, when immersed in dilute sulphuric acid, form a voltaic couple. Its 
action differs in no wise from that of the ordinary primary battery, except 
that when it has given out all the energy that the chemicals present enable 
it to supply, instead of having to put in new chemicals, the cell can be 
regenerated or brought back to its original condition by passing current 
into it in a direction opposite to that in which the flow took place on dis- 
charge. Obviously, there are many combinations which can be used as 
storage batteries, but with the exception of the lead-sulphuric acid battery, 
none has proven commercially practical, unless it be possibly the Edison 
battery, which has lately appeared. This battery has for one of its elec- 
trodes, nickel oxide, and for the other, finely divided iron or iron sponge, 
these being immersed in a solution of sodium hydrate. Up to the present, 
however, these cells have not been used for power work, and therefore the 
discussion will be confined to the lead battery. 

The plate on which the lead peroxide is carried is termed the positive 
plate, and the lead sponge plate is termed the negative, the reason being 
that on discharge, current flows from the lead peroxide plate and returns 
to the battery via the lead sponge plate. The condition, however, is the 
opposite of this inside the cell, as the current flows from the lead sponge 
plate to the lead peroxide plate. Therefore, considered as a voltaic couple, 
the lead sponge plate is the positive; considered as a source of electric 
current, however, the lead peroxide plate is the positive, since it is from 
this electrode that^the current flows out. 

r JTneo2*ies. — The first and oldest theory is that on discharge hydrogen, 
which is released at the lead peroxide plate (Pb02), combines with some of 
the oxygen in the peroxide, forming water, and reducing the oxidization 
of the PbC>2 by one molecule of oxygen, bringing it to a state of lead oxide, 
or PbO. At the sponge lead plate, oxygen is released (these released gases 
coming, of course, trom the electrolytic decomposition of the water in the 
electrolyte), and this oxygen (O) combines with the sponge lead (Pb), and 
oxidizes it, causing it also to become lead oxide (PbO). Thus the two 
plates tend to approach the same chemical composition. If lead oxide 
(PbO) be immersed in sulphuric acid, it will be chemically attacked, inde- 
pendently of any current flow, and change into lead sulphate, the chemical 
reaction being 

PbO + HzSO* - PbS0 4 + H 2 0. 

Thus the active material on both the plates tends to approach the condi- 
tion of lead sulphate. 

On charge, the reverse condition takes place, the hydrogen being released 
at the negative plate and the oxygen being released at the positive, the 
hydrogen reducing the oxide in the negative plate and carrying it back to 
its original condition of sponge lead, and the oxygen at the positive increas- 
ing the oxidization of the positive plate and returning it to its condition of 
lead peroxide, PbOg. 

The later theory is that the plates do not pass through the intermediate 
stage of being changed to lead oxide, but, on discharge, change directly 
from their respective states to that of lead sulphate. This theory is doubt- 
less the correct one, for the reason that in the chemical change from lead 
oxide to lead sulphate, heat is released, which represents lost energy, and 
if this energy loss should take place it would be impossible to get from the 
storage battery a large proportion of the amount of energy which might 
have been put into it on charge. 

872 



THEORY AND GENERAL CHARACTERISTICS. 873 

The foregoing is set forth by the following reversible equation, which 
shows the action that takes place: 

charge 



(1) Pb02+H 2 S04 = PbS04 + H 2 + 

(2) Pb + H2SQ 4 = PbS0 4 +H 2 



(3) = (1) + (2) = Pb0 2 +Pb + 2H2S04 = 2PbS04-f-2H 2 0. 
discharge 

The first equation shows the reactions which take place at the positive 
plate; the second shows those which occur at the negative; and the sum 
of these two, the third, is the combined effect and is the fundamental equa- 
tion of the storage battery. Reading from left to right the reactions are 
those which take place on discharge, while read from right to left the 
reactions are those which take place on charge. 

Chi«ng*e in Electrolyte. — The reversible equation of the storage 
battery shows that some of the SO 3 in the sulphuric acid (which may be 
looked on as being made up of H 2 4- S0 3 ) goes into chemical combina- 
tion with the plates on discharge, and a definite amount of SO3 is abstracted 
from the electrolyte from each ampere hour of discharge, and therefore the 
concentration of the electrolyte decreases and is lower at the end of dis- 
charge than at the beginning. The amount of S0 3 abstracted per 100 
ampere hours is 298 grams, and therefore, with a given quantity of electro- 
lyte and acid density, the final density at the end of discharge after a cer- 
tain number of ampere hours has been taken out, can be computed. 

The formula for computing the quantity of electrolyte required, when 
the initial and terminal densities are given is 

„ _ 1290 - 10.53 d 

X = number of ounces avoirdupois of electrolyte per 100 ampere hours 

of discharge. 
D = percentage of H2SO4 in the electrolyte at the beginning of discharge. 
d = percentage of H 2 S04 in the electrolyte at the end of discharge. 

For discharge other than 100 ampere hours, multiply the computed 
value of X by the actual discharge and divide by 100. 

^ 1290 + d(X- 10.53) 
Also D = 



( 



and d = 



X 

1290 - XD 
10.53 - X ' 



Sulphate. — Lead sulphate, which is a white substance, has no con- 
ductivity whatever, and if too much sulphate be allowed to form on 
discharge, it is difficult to bring the battery plates back to their original 
condition because the regenerating current cannot be made to flow through 
the sulphated masses. If the plates are only partially sulphated, the high 
conductivity of the active material with which the sulphate is mixed will 
afford a path for the current which can easily reduce the sulphate back to 
sponge lead or lead peroxide. 

This is one of the reasons why discharge should never go beyond the 
point where the voltage per cell is 1.8 with normal outflowing current. 

Change in Volume. — Another reason for avoiding overdischarge 
lies in the increase in volume of the active material when converted into lead 
sulphate. If too much of the active material be converted into lead sulphate, 
the increase in volume sets up strains in the plates, tending to buckle them, 
and causes the active material to crack or shed and fall away from the sup- 
porting grid, thus reducing the amount of available active material, the 
capacity of the plates, and shortening their life. 



874 STORAGE BATTERIES. 

Voltage. — The voltage of lead peroxide against sponge lead in dilute 
sulphuric acid is about 2 volts, varying with the concentration of the acid. 
The actual voltage for any concentration may be computed by Streintz's 
formula: E = 1.850 4- 0.917 (S-s), in which 

E = E.M.F. of cell. 

S = Specific gravity of the electrolyte. 
s = Specific gravity of water at the temperature of observation. 

In practice it is generally assumed as 2.05 volts, this being the E.M.F. 
on open circuit when the battery is fully charged; that is, both electrodes 
being free from any lead sulphate. As the battery discharges, the voltage 
gradually decreases, so that when the battery is nearly discharged its voltage 
is less than at the beginning of discharge. The reasons for this will appear 
hereafter. 

Appearance of Plates. — The battery plates are distinguishable 
both by their appearance and hardness, the peroxide plate being of a reddish 
brown or chocolate color and hard like soapstone, and the sponge lead 
plate is a grayish color, and can readily be cut into with the thumb nail. 

Requirements. — Neither lead sponge nor lead peroxide possess any 
mechanical strength, and therefore in order to make them into suitable 
electrodes it is necessary that they be attached to a supporting plate or 
grid, and since lead is the only metal except the so-called "noble metals" 
which resists the action of sulphuric acid, the supporting grid is always 
made of it. 

In order that a storage battery should work satisfactorily the current 
must be distributed equally over the surface of the plate and pass through, 
practically, all the molecules of the active material both on charge and 
discharge, and it is essential that batteries be so designed as to attain this 
condition; otherwise portions of the plate will be overworked and will dis- 
integrate, while other portions may be left in good condition. 

Types of Mates. 

In the production of battery plates there are three general methods: 

One is known as the Plante process, which consists in chemically or 
electrochemically forming sponge lead or lead peroxide directly on the 
surface of a lead plate, this active material being produced from the lead of 
the plate itself. 

The second method consists in taking certain oxides of lead, principally 
litharge and red lead, and mechanically applying them to a previously 
prepared leaden grid — generally under pressure — and afterwards reduc- 
ing these oxides to sponge lead or lead peroxide. 

The third method, which is not much used now, is to prepare pellets of 
sponge lead or other lead compounds which may easily be reduced to 
sponge lead, placing them in a mould, and casting the supporting grid 
around them. 

In the Plante type of battery the layer of active material produced is 
comparatively thin, and in order to obtain a sufficiently large quantity to 
give each plate a reasonable capacity, it is necessary that the area exposed 
be made as large as possible. This is accomplished by some method 
which raises grooves or webs in the plate, or by making up the plate of 
narrow ribbons of lead, which are folded backwards and forwards until an 
electrode is finally produced, the thickness of which is equal to the width 
of the lead ribbon, the length and breadth of the plate being anything that 
may be desirable. 

The comparative value of these different types of batteries will be taken 
up after discussion of various characteristics of batteries in operation. 

Capacity. — The unit of storage battery capacity is the ampere hour, 
that is, the ability to discharge one ampere continuously for one hour. 

The capacity is dependent on the rate of discharge; the temperature; the 
quantity of active material present; the quantity of electrolyte in the cell, 
and the exposed surface of the plate. 

Theoretically, .135 oz. of active material per negative plate, with .156 
oz. per positive or .291 oz. for both electrodes will, in the presence of suffi- 
cient electrolyte, give a discharge of one ampere hour. In practice about 



TYPES OF PLATES. 



875 



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five times this much, or 1.45 oz. for both plates is required The reason 
of this is that the active material is not completely reduced, the discharge 
being stopped before the point of zero voltage is reached and the gradual 
formation of sulphate as discharge proceeds, tends to close up the pores 
and prevent access of the electrolyte to the mass of active material. 

The capacity increases with increase in temperature, being about 1 per 



876 



STORAGE BATTERIES. 



cent for each degree Fahrenheit increase in temperature. Theoretically, 
the ampere hour capacity of a battery should not vary with the current 
rate. If a battery discharge continuously 100 amperes for 8 hours, giving 
800 ampere hours at this rate, theoretically it should discharge 800 amperes 
for one hour. As a matter of fact, however, the ampere hour capacity of 
a battery decreases rapidly with increase of rate of current flow. The 
reason for this decrease in capacity is due to several causes, the most impor- 
tant one being that as discharge proceeds, the active material begins to 
turn into lead sulphate. The volume of the lead sulphate is very much 
greater than the volume of the active material from which it is formed, and 
since the action takes place most rapidly on the surface of the plates where 
they are in contact with the electrolyte, the formation of the sulphate also 
takes place most rapidly at the surface, and this mcrease of volume tends 
to fill up the pores of the plate and prevent access of the electrolyte to the 
active material which lies beyond this shielding layer. If the discharge 
rate be very rapid, the masking layer of sulphate is rapidly built up, and 
the shielding effect takes place more quickly. In a battery discharged at a 
low rate the formation of this sulphate layer is so slow that the electrolyte 
can reach the innermost portions of the porous active material, the chemi- 
cal action takes place more thoroughly, and a greater amount of current 
can therefore be taken out. 

Curve No. 1 shown in Fig. 1 gives the variations in capacity with varying 
rates of discharge in percentages of the eight-hour rate, and curve No. 2 
shows the increase in amperes output with increased discharge rates. 

Thus if a battery have a capacity of 400 ampere hours, it will discharge 
50 amperes continuously for eight hours. If the total capacity be taken 
out in one hour, the discharge rate will be 200 amperes, and the ampere 
hours will be 200, this being 50 per cent of the eight-hour rate as indicated 
by the curve. If the ampere hour capacity of the battery at the eight-hour 
rate be known, its capacity at any other rate can be determined from this 
curve, or if its capacity at any rate be known its capacity at the eight-hour 
rate can be also determined. The curve is an average, and applies approxi- 
mately to nearly any type of battery, although different characters of 
batteries will give different curves, but none of them will depart materially 
from that shown in the figure. 

Voltag-e Variation. 

As stated, the voltage depends on the character of the electrodes and 
the density of the electrolyte. The available potential at the battery ter- 
minals is further dependent on the internal resistance of the cell. These 
facts explain the drop in voltage as discharge proceeds, as indicated by the 
curves in Fig. 2. 



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Fig. 2. 



ELECTROLYTE. 877 

The electrodes gradually change from pure active material to a mixture 
of active material and sulphate; the formation of the sulphate increases the 
resistance from the surface of the electrodes to their conducting grid, 
thereby increasing the internal resistance, and the surface layer of sulphate 
prevents access of electrolyte to the interior pores of the active material, 
and the small amount of electrolyte imprisoned in these pores has its SO3 
rapidly abstracted from it, greatly reducing its concentration and there- 
fore the voltage of the cell. To this cause nearly all of the fall in voltage 
may be attributed. 

Electrolyte. 

The resistance of the electrolyte varies with the density of the acid, 
being a minimum when 30 to 35 per cent of the mixture is acid, and 
increasing if a greater or less percentage of acid be present. 

Parts of the plate surface may do more than their share of the work if 
the plates be very long and the containing tanks deep, this condition aris- 
ing from a difference in the density of the electrolyte at the top and bottom 
of such tanks. The containing cells should therefore never be deeper than 
20 inches, unless some artificial means of acid circulation be used, such as 
compressed air introduced into the bottom of the tank through small rubber 
tubes. With such circulation the electrolyte density is maintained con- 
stant in different portions of the tank, and the plates will then be worked 
at equal current densities over their entire surfaces. 

Conductivity also changes with the temperature, being greater for 
increase of temperature. The table on page 1229 under caption "Electro- 
chemistry" shows the changes in electrolyte resistance with variations in 
density and temperature. 

The density of electrolyte in storage batteries should never exceed 1.200 
when the batteries are fully charged, and there should be ten pounds or 
more of electrolyte per 100 ampere hours of battery capacity on a basis of 
the eight-hour rating. The final density at the end of discharge with this 
quantity of acid and 1.200 initial density, will be about 1.134. 

In motor car batteries about four pounds of electrolyte per 100 ampere 
hours is sufficient, and because of the small amount of acid present the 
initial density must be higher. If the initial density be 1.265 at beginning of 
discharge it will, with this amount of acid, fall to about 1.137 at the end of 
discharge. Since there is a definite change in density for a given amount 
of discharge taken from a cell, the density of the electrolyte is one of the 
best indications of the state of charge of a battery, provided, of course, 
that no internal discharge, due to local action, takes place. If, when the 
cell is charged, it shows a density of 1.200 and when discharged 1.130, the 
difference, .07, represents the total change. If at any time the density is 
1.165, just one half the amount of capacity has been taken from the cell. 
In order that these observations may be reliable, however, it is necessary 
to stir the electrolyte well, so that the density is the same all through the 
tank; also if the discharge has taken place at a high rate, the cell must 
stand for an hour or more before the electrolyte will completely diffuse so 
that the density readings are correct. 

The electrolyte must be made of either distilled or rain water, mixed 
with pure brimstone acid. Ordinary city or well water will, in all prob- 
ability, ruin the batteries, and pyrites acid will most certainly do so. 

The electrolyte should always be tested to discover if harmful impurities 
are present, which are platinum, iron, chlorine, nitrates, copper and acetic 
acid. 

The tests for these are as follows: 

Platinum. — A complete test for this substance can only be made by 
an experienced chemist with proper appliances. A good rough test for 
traces of platinum is to pour electrolyte into a cell and note if gassing takes 
place on open circuit. If it does, and continues for some time, it is an 
indication of the presence of platinum, and the suspected electrolyte should 
then be sent to a chemist for analysis. Never use chemically pure sul- 
phuric acid which has been refined in platinum stills. 

Iron. — Take a sample of the electrolyte and neutralize with ammonia. 
Boil a small portion with hydrogen peroxide, which process will change 
whatever iron may be present into the ferric state. Add ammonia or 



878 



STORAGE BATTERIES. 



caustic potash solution until the mixture becomes alkaline. Iron will be 
indicated by a brownish red precipitate which will then form. 

Chlorine. — Take a small sample of the electrolyte, add a few drops of 
nitrate of silver solution of concentration of twenty to one. A white pre- 
cipitate will indicate chlorine. This precipitate will be redissolved by 
addition of ammonia, and can be re-precipitated by the addition of nitric 
acid. 

Nitrates. — Place some of the electrolyte in a test tube, and add strong 
ferrous sulphate solution. Then carefully pour down the side of the tube 
a small amount of chemically pure concentrated sulphuric acid, so that it 
forms a layer on top of the liquid. If nitric acid be present it will be 
shown by a stratum of brown color, which will form between the electro- 
lyte and concentrated acid. 

Acetic Acid. — Add ammonia to a sample of electrolyte until it becomes 
neutral, then add ferric chloride (Fe2Cle). A red color will indicate the 
presence of acetic acid, which may be confirmed by the addition of hydro- 
chloric acid, which will bleach the mixture. 

Local Action. — Certain metallic impurities present in the electrolyte 
may be, on charge, carried over to the negative plate, and the hydrogen 
there evolved will turn these impurities into pure metal. The condition 
then exists of the sponge lead plate having a different metal attached to 
it, and in electrical connection therewith, and the two immersed in elec- 
trolyte. If the voltage of such a couple is sufficiently high to decompose 
the electrolyte, current will begin to flow, the whole acting as a short- 
circuited battery at the negative plate. This discharges the negative, 
either wholly or partially, according to the amount of metallic impurities 
which may be carried over, and it is then not in a proper condition to 
discharge in company with the positive plate when it is desired to take 
current from the cell. If this local action continues for some time the 
negative plate may be so far discharged that it will sulphate, and finally 
become worthless. 

Cadmium Test. 

The condition of the negative and positive plates can best be ascer- 
tained by measuring the voltage between the plate under examination 
and a small test electrode of cadmium. This cadmium should be covered 





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Fig. 3. 

with rubber, perforated so that the test piece cannot come in contact with 
any of the battery plates or connections, though the electrolyte may freely 
penetrate to it. 

When a cell is fully charged, showing a voltage of 2.5, the voltage 
between the negative plate and the cadmium should be from .16 to .2 volt. 
When discharge takes place, this voltage gradually reaches zero, after 
which a potential begins to rise in the opposite direction, gradually increas- 
ing with discharge. When the voltage, after passing through zero, reaches 
a value of .25 volt, the full amount of discharge has been taken from the 
negative plate, and the current should be cut off regardless of the potential 
of the cell. 

Figure 3 shows the way in which the potential between the negative 



EFFICIENCY. 879 

plate and the cadmium changes. The cadmium undergoing no discharge 
does not change, and its line of potential is therefore horizontal and 
unchanging, as indicated. The negative plate, however, is discharging, 
and its potential decreases so that, though it begins to discharge at a poten- 
tial of .18 volt above the cadmium, it soon reaches a point at which it is 
the same as the cadmium, the voltage between them then being zero. As 
the potential of the negative falls further, a potential begins again to 
appear between the two, but, as is obvious, it is in the reverse direction, 
as the potential of the negative plate is now lower than that of the positive. 

On charge, the voltage between the cadmium and the negative plate 
should be brought up to at least .17, even if continued overcharge after the 
cell has reached 2.5 volts is necessary to do it. 

Batteries are so designed that the negative plates work through their 
proper range of potential with normal change in the cell E.M.F., but over- 
sulphation, reduction in amount of active material, or, most of all, local 
action, will destroy this balance, and these cadmium tests are useful in 
keeping watch over the condition of batteries in service. 

Polarization. 

If the voltage of a battery on open circuit be a given amount, say 2 
volts, and charging current is sent into it, it would be natural to assume 
that the potential rise at the battery terminals would be equal to the drop 
due to the internal resistance of the battery. It is found, however, to be 
very much greater than this amount — the actual internal resistance of 
large cells being practically negligible. This increase in drop, when cur- 
rent passes through a cell, comes from a phenomenon known as polariza- 
tion, which is, in effect, the production of a counter E.M.F. which opposes 
the flow of current, and which always takes place whenever current passes 
from one electrode to another immersed in an electrolyte. This effect also 
opposes the flow of discharging current, and causes the voltage drop at the 
cell terminals, which is observable when current is taken from a battery. 
The principal polarizing agent is hydrogen, which may be considered as 
an electro-positive element. It always forms at the negative electrode 
and sets up an E.M.F. opposing current flow. 

In cells of the same type the drop at any given time rate of charge or 
discharge is the same for any size of cell. 

The Voltagre I>rop in cells of a given type is independent of the 
size of the cell, but varies with the state of battery charge and the rate 
of discharge. This drop is also fairly constant for various types of cells. 
The following table gives the fall or rise in voltage from the open circuit 
E.M.F. when discharge or charge takes place: 

8-hour rate 05 volt 

6 " " 065 

4 " " 09 

3 " " 11 

2 " " 14 

1 " M 2 

Efficiency. 

The efficiency of the storage battery, similarly to that of any other 
device, is the ratio of the watts output to the watts input. If current be 
taken out at a high rate, and a resulting small capacity be obtained, it 
does not follow that the efficiency has been lowered correspondingly, as 
it will be found that the amount of current required for succeeding charge 
will not be so great as if a lower rate of discharge had been used, and a 
greater amount of energy taken from the battery. In other words, there 
is a relation between the amount of energy derived on discharge and the 
amount of energy required on subsequent charge to bring the battery 
back to the condition at which the discharge began. The efficiency of 
batteries which discharge only a few moments and immediately after 
receive charge, that is, in which the charge and discharge fluctuate rapidly, 



880 STORAGE BATTERIES. 

and the net amount discharged from the battery in an interval of time is 
small, is about 90 to 92 per cent. Where used for power storage, a long 
continuous charge being sent into the battery and followed by a long con- 
tinuous discharge, the efficiency is from 75 to 80 per cent. 

The losses in a battery are made up of the I-R, and the gassing at the end 
of charge, in which the constituent gases which are released by the action 
of the electric current do no chemical work on the electrodes, but escape 
into the air, the energy required for this dissociation being lost. There is 
also the further loss due to the counter E.M.F. of polarization, as has been 
explained. 



Comparison of PI ante and Pasted 
Electrodes. 

Of the two types of cells mentioned, the Plante and the pasted, each has 
its particular place, and one is more suitable than the other for its partic- 
ular class of work. 

The pasted negative plate is, in general, the best type for nearly every 
class of work. Pasted positive plates are necessary in batteries where 
light weight is required, such as in automobile and train lighting batteries. 
They are also suitable for battery plants which receive long charge, store 
the energy and discharge over a considerable length of time, such as resi- 
dence and isolated plants, and central lighting stations. The Plante posi- 
tive is most suited to those conditions where the battery discharge takes 
place for short intervals at very high rates, such as regulation of railway 
and elevator loads, and also when prolonged overcharge is likely to occur 
frequently. 



Charging*. 

In charging, the voltage gradually rises, as shown by the upper curve in 
Fig. 2, until about 2.5 volts are reached, when, at both the positive and 
negative plates, gases are rapidly released. Charge should always be 
continued until both plates gas freely. Full charge will also be indicated 
by the electrolyte density rising to its proper value. 

The best way to charge is to send in current rapidly at the beginning 
and gradually decrease it until at the end of charge the current flow is very 
small. For instance, in charging a 1,000 ampere hour cell for eight hours, 
the average rate of flow is 125 amperes. The proper rates at which to 
charge this cell would be 

250 amperes for 1 hour 

200 " " 1 " 

150 " " 3 " 

75 " " 1 " 

25 " " 1 " 

For rapid charging, when a battery has to be charged in four hours, the 
current should vary as follows: 

40 per cent of total 1st hour 

25 " " " 2d 

20 " " " 3d 

15 " " " 4th " 

For quick charging in three hours the rates should be: 

50 per cent 1st hour 
33J " " 2d " 
163 " " 3d " 



BATTERY TROUBLES. 881 

Whatever the rapidity of charge, never send a heavy current into a battery 
toward the end of charge. The rapid rates can only be used during the 
early part of charge. 

In case of loss of electrolyte from the cells from evaporation or spraying, 
add only pure water to maintain its level, as the addition of normal elec- 
trolyte will gradually increase the density of that in the cells, because the 
added liquid merely takes the place of that which has been carried off as 
gas or lost from evaporation, which, in either case, is pure water only. High 
electrolyte densities tend to accentuate all the troubles that can befall a 
battery, and accelerate the formation of sulphate. The water should be 
introduced through a rubber hose or lead pipe extending nearly to the 
bottom of the cell, so that it will diffuse and mix with the electrolyte. If 
the water be poured in, it, being lighter than the electrolyte, will float and 
take a long time to diffuse with the liquid in the cell. 

Removal from Service. 

To take a battery out of commission it should first be fully charged, 
then given a good overcharge, and then discharged down to 1.7 volts per 
cell in the electrolyte, immediately after which the electrolyte should be 
drawn off, and either distilled or rain water put in the cells. The dis- 
charge should then be continued until the voltage comes down practically 
to zero. In most cases it is necessary to short-circuit the cells in order to 
get them down nearly to zero with pure water as the electrolyte. Dis- 
charging them in the water has no injurious effect, however, as no sulphate 
can form. Upon complete discharge the water should be poured out of 
the cells, and the plates thoroughly washed, generally by running water 
continuously through the cells. All water is then drawn off, and the plates 
may then stand for any length of time without injury. ^ When the bat- 
teries are again to be used, it is only necessary to pour in the electrolyte 
and give a long overcharge. 



Battery Troubles. 

The principal troubles which are encountered in battery operation are 
loss of capacity, buckling, shedding of active material, sulphation and 
loss of voltage. 

JLoss of Capacity usually comes from clogging of the pores in the plate 
with sulphate which is not visible to the eye because the surface of the 
plate is maintained in proper condition but the interior portions of the 
active material have not been thoroughly reduced. This condition can be 
remedied by prolonged overcharge at low current rates, say about one- 
fourth the normal eight-hour charging rate. 

JLoss of ActiVe Material will also reduce the capacity of a plate, 
and this takes place continuously, but slowly, in every storage battery, and 
may be considered as the normal depreciation. If the battery be over- 
worked, however, and especially if discharge be carried too far, the amount 
of sulphate formed will so expand the active material as to cause it to crack 
or shed off very rapidly. 

Buckling-. — Under the action of unequal expansion of the two sides 
of the plate, or certain portions of the plate, the strains may distort it and 
cause it to assume a buckled shape, that is, bent so one side is concave and 
the other convex. This is due, in every case, to over-discharge on either 
the whole or some portion of the plate, and consequent over-sulphation and 
over-expansion. In certain battery plates, which are designed to allow this 
expansion, buckling cannot take place, but in most of them the active 
material is on an unexpanding framework, and over-discharge is therefore 
to be avoided. 

Sulphation. — This is practically the cause of every storage battery 
trouble, and can only be avoided by stopping the discharge before the 
voltage of the cells has fallen too low, namely, at l.S volts per cell, with 
normal discharge current flowing, and by occasional boiling, that is, over- 
charge which should be given at intervals of about three or four weeks. 



882 STORAGE BATTERIES. ' 

In giving this overcharge the battery should be fully charged at normal 
rates until it shows about 2.6 volts per cell. The current should then be 
decreased to about one-half its normal eight-hour rate, and the charge 
continued until the cells show about 2.65 volts, and about twenty minutes 
after this potential is reached. This will effectually reduce any sulphate 
which may have accumulated in the pores of the active material. A bat- 
tery should never be allowed to stand idle or uncharged after discharge, 
as the plates will sulphate very rapidly. A charge should be started imme- 
diately after discharge, or as soon thereafter as possible. 

JLosa of Voltagre. — It will frequently be found that one or more of a 
number of cells will show a lower voltage than the others. This generally 
occurs because of loss in capacity, so that a cell having this lower capacity, 
and in series with the main battery, would discharge the same amount as 
the other cells having a higher capacity, and in this way its voltage would 
drop more rapidly and always be lower than that of the other cells on 
discharge. 

Testing*. 

There are two classes of storage battery tests. One is to determine 
whether a battery which has been installed meets the conditions of the 
specifications; the other is to determine all the constants of a battery as 
compared with others on the market, either for purposes of improving the 
product of the factory or determining its commercial value. 

The first class of tests will not be gone into here, as they will be indicated 
by the conditions of the contract and specifications. In the second class 
of tests the following are the points to be determined: 

1. Weight of complete cell. 

2. Weight of the separate component parts, namely, elements, electro- 
lyte, separators and containing cell. 

3. Dimensions of component parts of the cell. 

4. Rates of charge, maximum and normal. 

5. Rates of discharge, maximum and normal. 

6. Capacity at low, normal and rapid discharge rates. 

7. Voltage curves of charge and discharge. 

8. Internal virtual resistance. 

9. Variation in density of electrolyte. 

10. Loss on charge with time. 

These are all determined by test and observation, and from them are 
deduced: 

11. Charge and discharge rates per square foot of positive plate surface. 

12. Charge and discharge rates per pound. 

(a) of complete cell. 
(6) of element. 

13. Capacity per pound. 

(a) of complete cell. 
(6) of element. 

14. Efficiency at various charge and discharge rates. 



Weight of Complete Cell and Component Parts. 

The weight of complete cell is of course found by means of the scales, 
and in order to determine the weight of the component parts the elements 
should be partly discharged, then removed from the electrolyte and dried 
with blotting paper, after which they are weighed. Do not keep the nega- 
tive plates in the air any longer than necessary. The weight of the elec- 
trolyte is equal to the total weight, less that of the elements and jar. 



INTERNAL VIRTUAL RESISTANCE. 



883 



Dimensions* 



These are determined by usual 
are dismantled for weighing, and 




Fig. 4. 
and V is a low-reading voltmeter 



measurements at the time when the cells 
should include dimensions of separators, 
height of lower edge of plate above bottom 
of jar, clearances between adjacent plates 
and between interior of jar and plates. 
Also area of plate surfaces and of con- 
ducting lugs. This latter for the purpose 
of determining if current densities are 
within usual practice, namely, about 150 
amperes per square inch. The cell may 
then be reassembled, given a prolonged 
overcharge, and connected up for testing. 
Connections for Testing*. — Re- 
ferring to Fig. 4, R is an adjustable resist- 
ance by means of which the current to 
the battery may be kept constant. B is 
the cell under test; <Sa D.P.D.T. switch; 
R 2 a variable resistance through which 
discharge takes place and is maintained 
at a constant value; A is a two-way 
reading ampere meter which measures 
both inflowing and outflowing current 
across the cell terminals. 



Rates of Charge and Discharge. 

The charging rates are usually given by the manufacturers, but if with- 
out this data, six amperes per square foot of positive plate surface may be 
taken as a trial rate, and after a few charges and discharges may be deter- 
mined by the length of time required to fully charge or discharge the cell. 
The eight hour is the standard normal rate. The maximum charge and 
discharge rates are usually taken as the one hour rate, although the current 
flow should never be so rapid on charge as to heat the cell more than 25° F. 
above surrounding atmosphere, or cause excessive gassing. 

Capacity at Various Discharge Rates. 

These are determined on taking out a constant current on discharge at 
say, the eight hour, the four hour and the maximum rate, whatever the 
latter may be, and noting the length of time during which this discharge 
continues, the battery having been charged up to 2.5 volts before beginning 
discharge, and being cut off when a voltage of 1.8 is reached, except in the 
case of the maximum rate, when the voltage can be carried down to 1.70. 
Since the capacity will change with temperature, it is necessary to note 
the temperature, and keep it constant through any one determination. 

Voltage Cnrves. 

During charge and discharge — both of which should take place at the 
constant rate for testing — frequent observations should be made of the 
voltage across the cell terminals. From this the regular charge and dis- 
charge curves are plotted with voltages as ordinates and time as abscissae. 



Internal Virtual Resistance. 

There are many methods of determining the internal ohmic resistance of a 
cell, but this has no bearing whatever on practice. Furthermore, it is not 
constant, but changes with the state of charge and discharge. What an 
engineer requires to know, is the drop at various discharge rates due to 
whatever internal effects may take place. The net result of all the factors, 



884 STORAGE BATTERIES. 

oamely, internal ohmic resistance, polarization, increase in normal internal 
ohmic resistance, due to the passage of gases through the electrolyte, etc., 
are all included in the term, "Virtual Resistance." To determine this, 
note the voltage of the cell on open circuit. Then close the discharge 
switch quickly, allowing a heavy discharge current to flow. The volt- 
meter will immediately indicate a lower value than when the battery was 
open circuited. Read the voltmeter within four seconds after closing the 
discharge switch. The difference between the discharge voltage and the 
open-circuit voltage, divided by the amperes flowing on discharge, is equal 
to the virtual internal resistance. Several tests should be made at different 
rates of discharge, and also several tests in which charging current is sent 
into the battery; the rise in voltage above that on open circuit noted, and 
the difference between the open circuit and the observed charging voltage, 
divided by the inflowing current, will give the internal virtual resistance. 
Owing to the small changes it is difficult to get accurate results, and the 
average of a number of tests both on charge and discharge should be taken 
as the actual value. 

Variation in Density of Electrolyte. 

This should be noted as discharge proceeds, by reading the specific 
gravity on a regular flat bulb hydrometer immersed in the cell itself. At 
the end of charge the hydrometer should be allowed to stand in the acid 
for about four hours before taking the final specific gravity in order to 
allow the dilute acid in the interior pores to mingle with the main body of 
acid in the jar. If the gravity be taken without allowing this time to 
elapse it will be found higher than the actual gravity will be after complete 
diffusion. 

JLoss of Charge with Time. 

This is determined by subjecting a battery to several cycles of charge 
and discharge, until its capacity becomes constant at the given rate. 
Knowing this capacity, if the cell be fully charged and set aside for several 
days and then discharged at the normal rate, the difference between its 
capacity when immediately discharged, and that after the interval of 
time has elapsed, shows the loss which may occur from leakage or local 
action. The cells should be kept perfectly dry and well insulated to 
prevent any leakage whatever when set aside. 

Charge and Discharge Rates and Capacity. 

These are computed from a knowledge of the dimensions and the charg- 
ing rates, determined during the test. 

Efficiency at Various Charge and Discharge Rates. 

Efficiency is determined at the various charge and discharge rates by 
dividing the output on discharge by the input on charge. In all cases the 
discharge should precede the charge against which the ratio is to be taken, 
and in every case the cell should be brought back to its original condition 
on charge. In taking efficiency, if a charge be given and a discharge follow 
it, to compare these would give no reliable results, as it is the charge which 
succeeds a given discharge that bears the proper relation to it- 
Failure to recognize this fact has been the cause of the extraordinary 
results which certain tests have shown, in which the efficiency has been 
over 100 per cent, though in most cases the erroneous method of comparing 
a charge with its succeeding discharge will give a result below the actual 
efficiency of the battery. 

Erection of Batteries. 

Storage batteries should always be installed in a cool room, which is 
well ventilated. The floor should be of cement, tiles or bricks, and it 
should slope slightly to one or more drains, so that water or electrolyte 
which is spilled or leaks may easily run off and the floor be kept dry. 



ERECTION OF BATTERIES. 



885 



All exposed iron work should be covered with some good acid-proof 
paint, and all exposed copper should have a coating of lead or tin, to pre- 
vent the corrosive action of acid fumes. 

Provision should be made for easy and thorough inspection of the cells. 
They should therefore be accessible, and hand lamps connected to long, 
flexible conductors provided so that each cell may be inspected. 

In the installation of large station batteries consisting of a number of 
large plates in lead lined tanks, it is usual to set these on 4X6 inch stringers 
which run underneath a row of cells. Four or more porcelain insulators 
are placed between the stringers and the cells, and in many cases it is usual 
to doubly insulate the cells by putting under each one a wooden frame- 
work which is the size of the bottom of the cell, above the stringers, resting 
it on insulators which are supported on the stringers. The cell rests on a 
second' set of insulators which are in turn supported by the framework. 
The number of insulators depends on the size and weight of the cell to be 
supported. The positive plates in each cell are connected to the negative 

{>lates in the adjacent cell by burning each of the plates separately to the 
eaden bus bar, as shown in Fig. 5. In the smaller sizes of cells which 



.NEG. .PLATE LUG 



/.BUS BAR 

.P0S. PLATE, LUG 

— ^ BURNED JOINT 



NEG. PLATE LUG 




-vglass support plate- 
\lead lining lead lining^- 

^wood tank wood tank" 

Fig. 5. 



have lead lined tanks, they are generally set on a framework from twenty 
to twenty-four inches high and rest upon four insulators. The plates of 
each cell may be joined to those of the next succeeding cell either by burn- 
ing to a common bus bar, as above mentioned, or by bolting together lead 
straps which form the cell terminals, the bolts and nuts being, of course, 
lead covered. ^ If the containing vessels are glass jars, it is usual to set 
each of them in a shallow wooden box about 1§ inches deep and filled with 
fine, dry sand. The glass cell beds itself in this sand, giving an equal 
distribution of pressure over the bottom of the jar, and the sand also catches 
and absorbs such electrolyte as may be spilled or sprayed out with escap- 
ing gases. Each sand tray, as these are termed, rests upon four porcelain 
insulators, and the cells are placed on a framework in one or two tiers, as 
may be desired. Fig. 6 shows this method of installing. 

JLead Burning:. — The hydrogen flame has the special property of not 
oxidizing, or otherwise soiling the lead, and is therefore used for melting 
together two lead surfaces, notably that between cells and the sheet lead 
lining of the tanks. 

Hydrogen gas is generated in a vessel from sulphuric acid and zinc. The 
gas is collected and passed through a water bottle to a burner, where it is 
mixed with air that has been forced into the burner by a pump or bellows 
tne_ mixture being ignited for the welding. 



886 



STORAGE BATTERIES. 



+ 





PLATES 




PLATES 



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Fig. 6. 
Uses of Batteries. 

The principal uses are : 

(1) For propelling electrically driven motor cars. 

(2) For railway train lighting. 

(3) As a substitute for the ordinary primary battery in telephone and 
telegraph work. 

(4) To carry the load peak on a supply system. 

(5) To carry the entire load during the periods of light demand, the 
generating equipment being shut down. 

(6) To regulate the load on systems where the demand fluctuates 
widely. 

(7) To act as an equalizer on three-wire systems in which the gener- 
ators are connected across the outsides of the system and give a corre- 
sponding voltage. 

(8) To reduce the amount of copper required for systems supplying 
variable loads. 

(9) To insure continuous service. 

(10) As auxiliaries to exciter dynamos in large alternating current 
stations. 

(11) Combinations of any of above from (4) to (8). 

The first three applications involve no special engineering knowledge. 

(4) In case of a supply system on which the load rises greatly during 
certain hours of the day, as shown by the load curve A, B, C, D, E,F, G, H, 
in Fig. 7, it is often advisable to install a battery to receive charge during 
the period of light load, as shown by the shaded area in which the heavy 
curve is the demand on the station and the light curve, the load on the 
generating equipment, the difference going into the battery; and to dis- 
charge in parallel with the generators during the heavy output on peak 
d, E, e, as shown by the cross-hatched area. Such a battery assists to 



USES OP BATTERIES. 

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888 



STORAGE BATTERIES. 



maintain a reasonably constant load on the dynamos, reduces the cost of 
the generating equipment, and is always ready to take up any excess load 
on the system, such as may come from a suddenly overcast sky or storm, 
without the loss of time necessary to fire up additional boilers and start 
additional engines, as would be the case if the entire load were carried by 
generating machinery. 

(5) After the peak discharge is ended and the load on the system 
decreases below the generator capacity, the batteries may be fully charged 
by, say, midnight, and the entire plant shut down during the period of 
light load until, say, five or six a.m. This is also indicated in Fig. 7, where 
the shaded area e, f, g, h, F, represents charge put in after the peak dis- 
cbarge, while the cross-hatched area h, k, m, n, indicates battery discharge. 
If the battery is large enough to do this, the cost of the fuel and the depre- 
ciation, for the time of shut-down, are saved, and two shifts of station 
attendants only are required instead of three. 

(6) In case of a system on wmich the load fluctuates rapidly and 
between wide limits, such as an electric railway or elevator load, the form 
of load diagram will be as showD in Fig. 8. Here it will be seen that the 



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Fig. 8. 



load varies from 200 to 1,000 amperes, though the average load taken over 
in diagram shown is 533 amperes. 

If the system be without a battery the generating equipment, including 
steam plant generators and accessories, will have to be of sufficient capacity 
to carry the maximum load, and the moving macbinery will be subjected 
to excessive shocks and strains due to the sudden loads. The fuel con- 
sumption is also much more than it would be if the engines could work 
under steady load. If a regulating battery be used, the generating equip- 
ment need only be great enough to supply the average load, as the battery 
will absorb all fluctuations. When the current required to supply the 
external circuit is small, the additional amount, supplied by a generator 
working under constant load, will go into the battery and be stored there 
as charge. When the external load exceeds the average generator out- 
put, the excess is furnished by the battery discharge. 

Thus the battery maintains a constant load on the generating equipment 
regardless of the variations in the external load, and the attendant advan- 
tages of fuel economy, normal duty only on moving machinery, decreased 
depreciation and repairs, are realized. 

(7) In three-wire systems, if the generators give a voltage equal to that 
between the outside mains, some forms of equalizer are necessary to prevent 
the unbalancing which may take place. If a battery be connected across 
the outsides with a sufficient number of cells in series to give an E.M.F. 



METHODS OF CONTROLLING DISCHARGE. 889 

equal to that of the system, and the neutral be connected to the middle of 
the battery, any excess of current flow, on one side of the system, will be 
supplied by discharge from the half of the battery connected across that 
outside and the neutral, while the half of the battery on the other side 
will receive an equivalent amount of charge. This is a widely used 
arrangement, as all the other advantages of storage batteries are obtained 
in addition to the balancing effect. 

(8) In cases where current is transmitted over a considerable distance, 
and the load varies either at different periods of the day, such as a lighting 
load, or rapidly, as a railway load, a storage battery located far away 
from the station, near the point where the load comes on the system, may 
be made to maintain the voltage at periods of heavy load when the feeder 
drop would be excessive, and the useful potential too low for satisfactory 
service. This is accomplished by the discharge of the battery when the 
heavy load comes on, reducing the amount of current transmitted and 
therefore the drop. The battery is charged during the time of light load 
when sufficient current is transmitted to supply the load, and also charge 
the battery. In other words, the battery equalizes the load over the line, 
causing the continuous flow of average current, and reducing the cost of 
feed or copper. 

In certain classes of rapidly fluctuating loads this effect is automatic 
and produced by slight changes in line drop, with small changes in the 
load over the line. 

(9) To insure continuous operation of any electrical plant a storage 
battery is necessary. No matter what may happen to the generating 
part of an equipment, if a storage battery be connected to the system it 
will immediately take on the load and carry it a sufficient length of time to 
enable any quick repairs to be made and the machinery again started up. 

(10) In large central stations where alternating current is generated and 
distributed to substations, and a large territory is dependent on the station 
supply, the failure of an exciting dynamo would cause a shut-down of pos- 
sibly several minutes, which would be a serious mishap. To insure against 
this a storage battery is connected directly across the exciter bus bars. It 
does no work and is never % of any real service unless failure of an exciter 
takes place, in which case the alternator field excitation is taken up 
without a break or interval. The insurance against stoppage, even for a 
moment, by means of the storage battery, is so thoroughly demonstrated 
that nearly all the large alternating current stations have added this equip- 
ment to their exciter systems. 

(11) Combinations of (4) to (9) inclusive can be in part effected by a 
single battery, such as regulation of fluctuating load, discharging on peaks 
and carrying the night load alone, or equalizing on a three-wire system, 
carrying peaks on both sides of the system, and also carrying the light 
load alone. Many other combinations will suggest themselves to the 
engineer as the conditions to be met may reqinre. 



Methods of Controlling: Discharge. 

In Fig. 2 is shown the change in voltage of a cell when charging and 
discharging at the normal rate. In order to compensate for this variation, 
so that the E.M.F. supplied to the discharging circuit may be maintained 
constant or varied at will to meet external load conditions, the following 
methods of control are used: 

(1) The number of cells in series may be altered by means of suitable 
switching mechanism. 

(2) Counter cells, or cells connected in opposition to the main battery, 
may be included in the discharging circuit and the desired voltage obtained 
by varying the number of counter cells in this circuit. 

(3) A variable resistance may be interposed in the main circuit to regu- 
late the discharge. 

(4> A dynamo-electric machine, termed a " booster," having its arma- 
ture in series with the battery circuit, its field being variable at will as to 
either direction or magnitude, may be employed. 

If any of the first three methods be employed, the total number of cells 



890 



STORAGE BATTERIES. 



composing a battery must be such that at the end of discharge, with 
normal outflowing current, the sum of the voltages of all cells in series is 
equal to the voltage to be maintained on the supply circuit. 

When discharging at normal rate, it is usual to stop discharge when the 
E.M.F. per cell has dropped to 1.8 volts. 



End Cells and Switches. 




Fig. 9. 



As shown in Fig. 2 the E.M.F. at the beginning of discharge is 2.15 
volts, and at this point on the discharge curve only 51 cells would be 
required to give 110 volts; as discharge continues and the E.M.F. falls, the 

number of cells in series must 
be increased accordingly, and at 
the end of discharge, when the 
cell voltage is 1.8, 61 cells are 
required in series to supply a 
110-volt system, 10 of them 
being end or reserve cells. The 
whole 61 cells would be con- 
nected in a single series, a 
conductor being connected to 
each of the ten end cells and to 
suitable contacts on an end cell 
switch. 

The voltage across the dis- 
charging circuit will be depen- 
dent upon the number of cells 
included in the circuit. 
Figure 9 shows an arrangement of cells, all connected in series, a portion 
of these being end cells; the voltage when the moving arm M is in the posi- 
tion shown by the full lines will be that due to all the cells in the main bat- 
tery, plus the voltage of the two end cells included by the arm. If now 
the arm be moved to the position shown in the dotted lines, the voltage 
across the mains L will be increased by the addi- 
tion of the end cells 4 and 5. In switching from 
one end cell point to another the discharging 
circuit must not be opened, neither must the 
moving arm touch one contact before leaving 
the adjacent one, since the joining of two con- 
tacts will short-circuit the cells connected 
thereto. 

In general, the form of switch for this pur- 
pose is essentially that shown in Fig. 10, where 
the moving arm is provided with a small ad- 
vance arm, the two being insulated from each 
other but connected through the resistance X. 
The spacings of the two arms and contacts are 
such that when the main current carrying arm 
is squarely on an end cell contact, the advance 
or auxiliary arm touches no other contact, but 
in passing from one point to the next, the ad- 
vance brush reaches the contact towards which 
the arm is moving, before the main brush leaves its contact; the resistance 
X between the two points prevents short-circuiting, and the current to 
the main circuit is never broken. 

The conductors joining the end cells to the end cell switch contacts must 
be of the same sectional area as the conductors of the main circuit, for 
when any end cell is in use the conductor connecting it to the switch 
becomes a part of the main circuit. 1000 amperes per square inch, when the 
battery is discharging at the two-hour rate, is good practice. 

End cell switches of small capacity are made circular; the larger sizes 
are, however, made horizontal in form, and both types may be either manu- 
ally operated or motor driven. 

End cell switches of large capacity are generally located as near the 
battery room as possible, to avoid the cost of running the heavy con- 




FiG. 10. 



BOOSTERS. 



891 



ductors, and when such switches are motor driven, the usual practice is to 
control their operation from the main switchboard. 

Automatic end cell switches have been used more or less abroad, but 
have found little favor in this country. The controlling devices for such 
switches are so arranged as to make the switch automatically respond to 
changes in the discharging circuit. 



Counter E.M.JF. Cells. 



Counter cells or counter electromotive-force cells are merely lead plates 
in an electrolyte of dilute sulphuric acid; they have no capacity but set up 
an opposing E.M.F. of approximately 2 volts per cell if current be passed 
through them. 

In using these cells for controlling discharge, the total number of active 
cells in the battery will be the same as if the method of end cell control had 
been used. The counter cells represent an increase in equipment, the 
additional expense being 8 per cent or more. 

Figure 11 shows the method of counter cell control; these cells are con- 
nected in opposition to the main battery, and conductors are run from each 
of the counter cells to points on a switch similar to an end cell switch. At 
the beginning of discharge all the counter cells are in circuit, acting in oppo- 
sition to the main battery. As 
discharge proceeds and the battery 
voltage falls, the counter cells are 
gradually cut out of circuit. 

Controlling discharge by counter 
cells is now nearly obsolete prac- 
tice, and is scarcely ever to be 
recommended; the only advantage 
in this method of control is that 
the discharge throughout the bat- 
tery is uniform, but this fact alone 
does not warrant the use of such 
methods on account of the addi- 
tional expense involved, and the 
energy loss when discharging 
against counter cells is the same 



I M I I I I I i I 



9 o 9 



'discharge 



C. E. M. E. CELLS 



Fig. 11. 



as if resistance had been interposed in the discharging circuit. 



Resistance Control. 

The discharge may be controlled by a variable resistance included in the 

discharging circuit. This method 
is not used unless the battery is 
of small capacity and the cost of 
energy low. 

Figure 12 shows a diagram for 
resistance control. In small 
plants, where the available space 
for battery auxiliaries is limited — 
such conditions obtaining in bat- 
teries for yacht lighting and the 
FlG. 12. hk e — the resistance control has 

some merit. 



M i I I I I I I I I l 



III 



l—A/VW 

VARI 



NAM 

VARIABLE 

RESISTANCE 



Boosters. 

A booster consists of a dynamo electric machine, the armature of which 
is in the battery circuit, its E.M.F. being added to or subtracted from that 
of the battery to produce discharge or charge. This action of the booster, 
i.e., the direction and magnitude of its armature E.M.F., may be auto- 
matically or manually controlled. 



892 



STORAGE BATTERIES. 



The Shunt Booster. 



JUPPLY MAINS 



As shown by the battery curves in Fig. 2 the maximum voltage per cell 
at the end of charge is 2.6 volts. As 61 cells are required for a battery 
operating on a 110-volt circuit, the total charging voltage required is 
2.6 X 61 = 158.5 volts, or about 50 volts higher than the voltage of the 
supply circuit, and to fully charge the battery this additional voltage 
must be supplied by a booster or by an excess voltage in the charging 
generator. 

Figure 13 shows the diagram of a simple charging booster. Its armature 
should be wound for the normal charging current, and have a maximum 

voltage equal to the difference 
between that of the supply 
circuit and the maximum 
charging voltage. The field 
is separately excited, either 
from the bus bars or the bat- 
tery, and the voltage at the 
armature may be varied by 
the field rheostat. 

Instead of discharging 
through an end cell switch 
or resistance, the current 
through the booster field may 
be reversed and varied, so 
that the E. M.F. of its arma- 
ture may oppose that of the 
battery, this E.M.F. being 
reduced as the battery vol- 
tage falls, the algebraic sum 
of the booster and battery 
E.M.F.'s being always equal 
to that of the supply circuit. 
In this case, however, it is 
usual to put in fewer cells, the 
available voltage being taken 
as 2 volts per cell. On dis- 
charge when the voltage of 
all cells in series is greater than that of the supply circuit, the booster voltage 
is equal to the excess battery voltage over the supply circuit potential, 
and in opposition to the battery voltage: when the battery voltage becomes 
equal to that of the supply circuit the booster voltage is zero; when the 
battery voltage falls below that of the supply circuit, the booster voltage 
must then be~ in a direction to assist the battery, adding its voltage to 
that of the battery. 




Automatic Boosters. 

In batteries which are used for regulation on fluctuating loads, the 
changes from charge to discharge and vice versa are so rapid that the state 
of battery charge changes but little. The voltage of the battery, however, 
changes with these fluctuations, increasing with inflowing and decreasing 
with outflowing current. 

In this respect the storage battery has much the same characteristics as 
a shunt wound generator: with increasing output the battery voltage falls, 
due to the drop caused by internal resistance and polarization; with 
decreasing output the voltage rises for the same reasons. 

These voltage changes are approximately proportional to the rate of 
current flow causing them. The fluctuations coming with such rapidity 
and irregularity must be automatically compensated for by changes in 
booster voltage, which vary both in direction and magnitude with the 
direction and rate of current flow. 

There are two generic types of automatic boosters, viz., the non-reversible 
and the reversible. 



BOOSTERS. 



893 



Jfon-Iteversible Booster. 

In installations where it is desired to supply both an approximately 
constant and a fluctuating load, from the same generators — such condi- 
tions obtaining in an office building or hotel, where it is necessary to supply 
lights and elevators from the same source of supply ~ the fluctuations in 
the power circuits must not interfere with the lighting circuits, and to 
prevent this, two sets of bus bars are provided. The generators are con- 
nected in the usual manner to one set of bus bars, and the lighting circuits 
are connected across these. Across the other set of bars are connected 
the circuits supplying the fluctuating load, and the battery is also con- 
nected directly across these power bars. The power bars are supplied 
with current from the lighting bars, a non-reversible or so-called " constant 
current" booster being interposed between the two, as shown in Fig. 14. 
Since this permits only a constant current to pass from the lighting bus 
bars, the load on the generator does not vary, although the load on the 
power busses may vary widely. The connections and operation of this 
system are as follows: 



tLEYATOR 



LAMPS 



or 



u 






Fig. 14. 



The booster armature and field are in series between one side of the light- 
ing and power bus bars. A shunt field is also provided, which acts in 
opposition to the series field. This booster carries a practically unvarying 
current from the lighting to the power bus bars, regardless of the fluctua- 
tions of the external load, which current is equal to the average required 
by the fluctuating load. 

Except under abnormal conditions, the shunt field always predominates, 
giving a voltage which is added to that of the lighting bus bars, so that the 
voltage across the power busses is always higher than that across the 
lighting by an amount equal to the booster voltage. 

If an excessive load comes on the power circuits, the increased excita- 
tion of the series coil, due to a slight increase in current from the lighting 
to the power bus bars, lowers the booster voltage and consequently reduces 
the voltage across the power bus bars. The battery discharges, furnishing 
an amount of current equal to the difference between that required by the 
load and the constant current through the booster. 

u If the power load decreases below the normal value, the slight decrease 
m current in the booster series field increases the booster armature voltage, 
and the excess current goes into the battery. The booster therefore does 
not in reality give a constant current, but by proper design the variation 
may be kept within a few per cent. 



894 



STORAGE BATTERIES. 




Fig. 15. 



Reversible Booster. 

Figure 15 shows a diagram representing one form of booster for produc- 
ing charge and discharge in accordance with variations in load, in which S 
represents a series field winding, and f a shunt field winding. The gen- 
erator output passes through the series winding, and the current in the 
coil S is to remain practically constant. The shunt coil / produces a field 
which opposes the field produced by S, the resulting magnetization being, 
in direction and amount, the resultant of the two field strengths. 

The adjustments are so made that 
when the normal generator current is 
passing through the series coil S, the 
shunt field just neutralizes its effect, 
and the resultant magnetization is zero. 
Since the open-circuit voltage of the 
battery is equal to that of the system, 
neither charge nor discharge takes place. 
With increased demand on the line, the 
slight increase in generator current in 
the coil S overpowers the shunt field, and 
causes an E.M.F. in the booster armature 
in such a direction as to assist discharge. 
If the external load falls below the average demand, the current in the 
coil S decreases slightly so that the shunt field predominates, producing a 
booster armature E.M.F. in a direction to assist charge. Although the 
voltage of the battery falls while discharging by an amount proportional 
to the outflowing current, the increased excitation due to this current 
through S is also proportional to it, and the booster voltage rises as that 
of the battery falls, their sum being always equal to that of the system. 
In other words, the booster serves to compound the battery for constant 
potential. 

Externally Controlled Boosters. 

The types of boosters before described, depend for their action on the 
differential relation of shunt and series coils, and produce a constant volt- 
age change, to charge or discharge the battery, with a given change in 
generator current. This is not the desired relationship, as the voltage 
required to effect a given charge or discharge of a battery varies greatly 
with its state of charge and its condition. Also, such Boosters require 
large frames for a given kilowatt capacity in order to accommodate the 
windings. 

Recently, systems of external control have been devised, which make 
use of ordinary shunt-wound machines as boosters, the fields being regu- 
lated to produce the proper voltages for effecting charge or discharge, by 
an external device which is, in turn, controlled by small changes in gener- 
ator current. So successful have 



EXCITER SERIES COIL 



these later forms been, that they 
have superseded the differentially 
wound boosters for both reversible 
and non-reversible control. 

One form is that of Hubbard, in 
which the external controller is a 
small exciting dynamo. The gen- 
eral arrangement is diagram mati- 
cally shown in Fig. 16. 

The exciter is provided with a 
single series coil, through which the 
station output or a proportional 
part thereof, passes; the armature of 
the exciter is connected to the excit- 
ing coil on the booster, and thence 
across the mains, as shown. With 
the average current passing through 
the field coil or the exciter, its arma- 
ture generates an E.M.F. which is equal to that of the system, and in oppo- 




Fig. 16. 



BOOSTERS. 



895 




Fig. 17. 



sit ion to it. These two opposing E.M.F.'s balance, and no current flows in 
the booster field coils. m With an increase in external load above the average, 
the tendency is for an increase to take place through the exciter series coil, 
augmenting its field strength and consequently the exciter armature voltage. 
This latter now being higher than that of tne line, causes current to flow 
in the booster field coil, in such a direction as to cause an E.M.F. in the 
booster armature which assists the battery to discharge, and is of a magni- 
tude to compensate for the battery drop occasioned thereby.^ When the 
load decreases below the normal, the current in the exciter field is decreased, 
and its armature voltage falls below that of the system. Current will now 
flow in an opposite direction in the booster field coil, generating an E.M.F. 
in the booster armature to assist charge. Since the exciter always gener- 
ates a voltage in opposition to that of the line, this system is known in the 
trade as the Counter E.M.F. System. 

Another type of externally 
controlled booster is that of 
Entz. The arrangement and 
connections are shown in 
Fig. 17. 

Ri and R 2 are two resis- 
tances made up of piles of 
carbon plates. These resis- 
tances diminish greatly in 
value when subjected to pres- 
sure. L is a lever resting on 
the tops of the piles, Ri and 
R2, which is pulled downward 
to compress them, by the 
spring at one end and the electromagnet S at the other, as shown. 

The magnet winding is in series with the current from the generator, and 
with normal output to the load M.M., the pressures of the spring and the 
magnet are so related that the resistance of Ri equals that of R 2 . The 
booster field has one terminal connected to the middle point of the battery, 
and the other terminal is connected to a wire which joins the upper ends of 
the two carbon piles. 

The lower end of R) is connected to the positive side of the circuit, and 
the lower end of R 2 to the negative side. 

The drop through R t plus R 2t i.e., from the positive to the negative side, 
is equal to the potential of the system, and therefore, when R^ is equal to R 2 
the drop through either is equal to one-half the potential of the system; 
hence the potential of the terminal of the field coil /, connected to the 
upper ends of the resistances, is midway between the potentials of the 
positive and negative mains. 

Since the other terminal of coil / is connected to the middle point of 
the battery, its potential ^ is also midway between the potentials of the 
positive and negative mains, from which it follows that when Rx and R 2 
are equal there is no difference of potential between the field coil termi- 
nals, consequently no excitation, and the booster potential is zero. 

If the external load should increase, a small increase in generator current 
will cause a stronger magnet pull, decreasing the resistance of R 2 and 
increasing that of R t . The drop through R 2 becomes much less than half 
the potential across the mains, anc] consequently there is a potential across 
the field winding f to cause current flow from the middle point of the 
battery, through the winding, through the diminished resistance R 2 , to the 
negative main. This produces a booster E.M.F. in a direction to discharge 
the battery and cause it to assist the generator to supply the load demand. 

Conversely, if the external load M.M. should decrease, the diminished 
pull of the magnet due to the slight decrease in generator current allows the 
spring pull to predominate, and the resistance of Rt is decreased while that 
of R 2 is increased. The field / becomes excited by current flow from the 
positive main, through the diminished resistance R lf through field /, to 
the middle point of the battery. This sets up an E.M.F. in the booster 
armature to charge the battery, the difference between the normal gen- 
erator output and the load demand being thus absorbed. 

Owing to the comparatively small change in the pressures which the 
magnet S exerts, and the thereby limited size of the carbon piles, this sys- 
tem is only directly applicable to small boosters. Where large machines 



896 



STORAGE BATTERIES. 



are to be controlled, the booster has a small exciting dynamo, its field being 
controlled as above described. 

Another form of externally controlled booster is that of Bijur and is 
shown diagrammatically in Fig. 18. 

The booster field winding has one terminal connected to the middle 
point of the battery, the other terminal being connected to the wire join- 
ing the resistances Pi and P 2 . L is a lever carrying at either end a number 
of metallic contact points Pi and P2 which dip into troughs of mercury 
D t and D 2 when one end of the lever moves upward or downward. These 
points are connected to corresponding points on their respective resistances, 
and therefore all of the resistances connected to contact points which are 
immersed in the mercury are short-circuited. The points are of unequal 
length, being in a step formation, so that they gradually contact with the 
mercury as the lever is moved. 

If more of the points Pi than points P2 are immersed in the mercury the 
resistance P2 is less than Pi, more sections of it being short-circuited. 
Current will therefore flow from the middle point of the battery, through 
the booster field /and through resistance P 2 to the negative side of the 
system, exciting the booster field and producing a booster E.M.F. to charge 
the battery; while if more of the points Pi are immersed the resistance Pi 
becomes the smaller, and current then flows from the positive side of the 



p + 




system through resistance Pi, through booster field /, to the middle point of 
the battery, the field excitation and the booster E.M.F. produced being in a 
direction opposite to the first described, and tending to discharge the battery. 

When the resistances Pi and P2 are equal there is no potential to send 
current in either direction through the field coil /. 

When the load on the external circuit is normal, the lever L is in a hori- 
zontal position, resistance of Pi is equal to the resistance of P 2 , no current 
flows through the booster field, the booster E.M.F. is zero, and no current 
passes into or out of the battery. 

With increase of external load the pull of magnet S is strengthened by a 
small increase in generator current passing through the winding. This 
draws down the left end of lever L, overcoming the pull of the spring. The 
contacts Pi are immersed to a greater or less degree in the mercury, thereby 
short-circuiting portions of Pi and decreasing its resistance. This pro- 
duces a current flow in the booster field to cause an E.M.F. to discharge 
the battery and assist the generator to supply the load demand. 

A decrease in external load is attended by a slight diminution in gen- 
erator current; magnet S is weakened, the pull of the spring predominates, 
resulting in a movement of the lever to immerse points P2 in the mercury 
trough Do and thereby reduce the resistance of P 2 , causing excitation of 
the booster field to produce an E.M.F. to send charge into the battery. 

The essential difference between this form of regulator and other types 
is that the design provides for a condition of neutral equilibrium between 
the pull of the magnet and that of the spring for any position of the moving 
parts; that is, with a given current passing through S, the pull of the mag- 
net balances the pull of the spring in any position of the lever L, conse- 



INSTALLATIONS. 



897 



£uently, the change in the generator current with change in external load 
is not proportional to the load but is a fixed amount. This variation is 
just sufficient to cause such a change in the pull of the magnet that the 
resulting unbalanced force overcomes the friction of the parts. The lever 
will begin to move and will continue to move until the current through £ 
is restored to its normal value, which is accomplished by causing the bat- 
tery to absorb or discharge current equal to the difference between the 
normal generator current and that supplied to the external load. The 
change in the resistances, being made by the immersion of the small con- 
tact points in mercury, offers no appreciable opposition to the movement 
of the parts and thus allows a continuous condition of neutral equilibrium 
to be maintained throughout the travel of the moving parts. 

Obviously by providing externally controlled boosters with a single vari- 
able resistance, a non-reversible booster is produced, its action being in 
effect the same as that described under the heading "Non-Reversible 
Booster." 

Comparison of Boosters. 

Reversible boosters should be used where the average, total current to 
the fluctuating load is greater than the battery discharge current, and 
where the potential of the power bus bars must not fall off with increase in 
load. Electric railway and lighting plants having long feeders are examples 
of the systems to which reversible boosters are suited. Non-reversible 
boosters should be used where the average total load is less than the bat- 
tery discharge current, and where a drop in the potential of the power bus 
bars is of advantage. Examples of such plants are hotel or apartment 
houses where electric elevators are operated from the lighting dynamos. 

Boosters are usually driven by electric motors directly connected to 
them, though any form of driving power may be used. They are some- 
times operated by engines or turbines. 

Installations. 

Figure 19 shows diagram of connections and Fig. 20 the switchboard of 
a battery equipment for a residential lighting plant. In the diagram, the 
voltmeter and voltmeter connections have been omitted. The bus bars 
on the battery panel are connected directly to the bus bars on the gene- 
rator panel. In this installation the generators are run during the after- 




STARTING BOX 



l|l|l|l|l|l|l|l|l|l|l|l|l|l|l|l|(J 
Fig. 19. 



898 



STORAGE BATTERIES. 



+" 




DIFFERENTIAL- 
AMMETER 



1 



[I 



ft 





-4- 



VOLTMETER 
SWITCH 



C L2 



CHARGE AND DISCHARGE 
SWITCH 




BATTERY 
SWITCH 



J 




EI 



OJ 



BOOSTERFIELD 
SWITCH 



BOOSTERFIELD 
RHEOSTAT 



MOTOR STARTING BOX 



BATTERY 
CIRCUIT BREAKER 




MOTOR SWITCH 



END CELL SWITCH 




UNDERLOAD 
CIRCUIT BREAKER 





Fig. 20. 



noon, charging the battery and supplying the load. When the battery 
is fully charged the generators are shut down and the battery carries 
the load alone. In this manner the plant gives continuous service, while 
the generators are run only from five to nine hours per day. 

The bus bar voltage remains constant at all times, the battery voltage 



INSTALLATIONS. 



899 



on discharge being regulated by means of an end cell switch. On charge, 
the E.M.F. above that of the bus bars, required to bring all cells up to full 
charge, is supplied by means of a motor driven charging booster, the voltage 
at the armature being suitably varied by changing the field excitation. 

Figure 21 shows diagram of connections arranged for charging the bat- 
tery in two parallel groups and discharging in series, the charge and dis- 
charge being controlled by variable resistances. In yacht lighting the 
limited space generally prohibits the use of a charging booster, and in such 
instances this method of charge and discharge control is the usual practice. 

In case the generator from which the battery is charged has sufficient 
range in voltage to charge all cells in series, a charging booster is not 



AMMEXEfl SHUNT 



AMMETER SHUNT 



VARIABLE J RESISTANCE 




6 6 

n 



Fig. 21. 



required, nor is it necessary to connect groups of cells in parallel, as the 
generator voltage may be varied as charge proceeds. 

The diagram shown in Fig. 22 permits of charging the battery at one 
voltage and supplying lights at a different voltage. As may be seen, two 
end cell switches are required for this plant. The voltage of the supply 
circuit is adjusted by the number of cells in series on switch S 2 , while 83 is 
moved to cut out cells as they become fully charged. In this instance the 
end cells included between the contact arms of the two end cell switches 
must be of sufficient size to receive the charging current, plus the current 
to the supply circuit. , 

If the battery can be charged at times when the generator is supplying 
no other load, only one end cell switch is required. 

Figure 23 shows a diagram of connections for a constant current booster 
system, in which the same generators supply a lighting and a power load, 
the battery being connected directly across the power bus bars. The 
diagram further provides for the battery to supply lights at such times as 
the generators may be shut down. 



Three-Wire Systems. 

In three-wire systems it is usual to put in two equipments, one on each 
side of the system. Figs. 24 and 25 show the general schemes of two 
different three- wire systems; the one shown in Fig. 24 consists of a com- 

flete battery equipment and charging booster on each side of the system, 
n this diagram the generators are connected to the outsides of the line, 
the neutral being taken from the battery. This makes a good arrange- 
ment. One side of the battery system will discharge a sufficient current 
to take up any unbalanced load. 



900 



STORAGE BATTERIES. 



Figure 25 is a battery three-wire system in which only one booster is 
used. The main battery is charged from the outsides of the system, and the 
booster forms a local circuit of the end cells and gives them the proper 
charge; the voltage of the system being high enough to charge the cells is 
the main battery. In the boosters shown in these diagrams the arma- 
tures only have been indicated, as in nearly every instance boosters on 
three-wire systems are merely charging machines, the fields being sepa- 
rately excited from the bus bars or from the battery. , 

Figures 26 and 27 show clearly the switchboard connections of a central 
station battery working on three-wire systems. It is obvious that the 
systems would work just as satisfactorily if the generators were of a poten- 



- C B - 






^1! Ill I III I III I III I 



CIRCUIT BREAKER 



.-•«3 




6 o-~ o o 

i — ZJ 



oooooooo 0S3 



066666666 



END CELL 
SWITCH 

s 2 



Fig. 22. 



tial equal to that of the outsides, and connected directly across the system, 
as any unbalancing would be taken up by the batteries. 



Battery Capacity. 

In computing the capacity of a battery to give a certain discharge, it is 
necessary to take into account the fact that the capacity of a battery 
varies greatly with the rate of discharge. This variation in capacity can 
be computed from the curves, Fig. 1. Taking the eight-hour rating as a 
basis, it is seen that only 50 per cent of the ampere hour capacity is avail- 
able at the one-hour rate of discharge. Therefore if 200 ampere hours be 
required at the one-hour rate, the normal ampere hour capacity must be 

_ _ = 400 ampere hours. In a like manner the normal capacity required 

for any other rate may be obtained. In the case of a load curve such as 



BATTERY CAPACITY. 



901 




Fig. 23. 



902 



STORAGE BATTERIES. 



that shown in Fig. 7, when the peak dEe is to be carried by the battery, 
it will be seen that the rate of battery discharge changes continually. 
If the area of the peak be taken above the line of generation supply. 




<L 6 



Fig. 24. 




Fig. 25. 



" de" it will be found equal to 550 ampere hours, and the time of discharge 
is 2.1 hours. 

On a basis of the two-hour discharge rate, the size of battery required 
550 
= £Tc7 — ^60 ampere hours. This, however, is the average rate of dis- 
cbarge and on a basis of 860 ampere hours battery capacity. When the 



BATTERY CAPACITY. 



903 



discharge takes place along the high portion of the peak at E the ampereg 
supplied by the battery are 400, which is nearly the one-hour rate. To 
determine the actual capacity required to take care of the load indicated, 
assume a capacity greater than that necessary for the average rate of 



+ Auxiliary Bus 


Jl 


_l_ Charging Bui 










lts\ 


3 


b 


rt=H 



C_MA C MA CMA f Switches 




_ Charging Bub 



I i e> i h Sbtl 



_ Switches C M A C M A C MA 

End Cell H jV 
Switch N'o. l T Amnieterel 



__ Battery 



Fig. 26. 



± Dynamo Bus' 




Fig. 27. 



discharge. The portion of the load peak to be carried by the battery is 
divided into vertical divisions, as indicated by the dotted lines. The 
ampere hours of each strip, divided by the rate of discharge factor (from 
curves, Fig. 1), gives the ampere hours capacity, on a basis of the normal 
rate, required for that particular strip. The sum of all these capacities 



904 



STORAGE BATTERIES. 



must be the capacity of the proper battery. If the assumed figure be toe 
small or too large, a second computation must be made, based on a capa 
city again assumed, which is greater or less than that just taken according 
as the result of the first computation is too small or too large For instance, 
if peak E be divided vertically into areas V, W, X, Y, and a 900 ampere 
hour battery assumed as the proper size, the normal rate of discharge will 
be 112.5 amperes. The ampere hours of area V are 75, and the average 
discharge rate is 210 amperes. Dividing 210 by the amperes of normal 
discharge, the result is 1.86. Locating 1.86 on the right-hand scale of 
curve, Fig. 1, and moving horizontally to curve No. 2, and then downwards 
to the lower scale, it is seen that this corresponds to the 3-i— hour rate. The 
percentage of the normal capacity at the eight-hour rate, when the dis- 
charge takes place at the 31 -hour rate, is shown by curve, Fig. 1, to be 76 

75 
per cent. The capacity required to cover strip V then is -=— = 99 ampere 

hours. Similarly the ampere hours of strip W are 193, the rate of dis- 

340 
charge 340 amperes, the factor = 110 K = 3.02 corresponding to the 1£- 



112.5 
Percentage of eight-hour capacity, 



.58, and ampere hours = 



hour rate. 

In a like manner, the capacity required for area X is 269 ampere hours, 
and for Y is 237 ampere hours, the sum being 938 ampere hours. The 
assumed capacity is therefore nearly correct, and a 950 ampere battery 
will be the proper size in this case. 

If the battery is also to be used for supplying the light load from 11 p.m. 
to 5 a.m., the capacity must be computed from the area h, k, m, n, which is 
990 ampere hours. The rate of discharge is fairly constant, and extends 
over six hours. The percentage of normal capacity available at the six- 
hour rate of discharge is 94 per cent. 

990 

-q2 = 1050 = ampere hour capacity of battery required to carry the 

load given from 11 p.m. to 5 a.m. 



Strength of Dilute Sulphuric Acid of Different 
Densities at 15° C. (59° JF.) 

(Otto.) 



Per Cent 
of H 2 S0 4 . 


Specific 
Gravity. 


Per Cent 
of SO s . 


Per Cent 
of H 2 S0 4 . 


Specific 
Gravity. 


Per Cent 
of S0 3 . 


100 


1.842 


81.63 


23 


1.167 


18.77 


40 


1.306 


32.65 


22 


1.159 


17.95 


31 


1.231 


25.30 


21 


1.151 


17.40 


30 


1.223 


24.49 


20 


1.144 


16.32 


29 


1.215 


23.67 


19 


1.136 


15.51 


28 


1.206 


22.85 


18 


1.129 


14.69 


27 


1.198 


22.03 


17 


1.121 


13.87 


26 


1.190 


21.22 


16 


1.116 


13.06 


25 


1.182 


20.40 


15 


1.106 


12.24 


24 


1.174 


19.58 


14 


1.098 


11.42 



Ordinarily in Accumulators the densities of the Dilute Acid vary between 
1.150 and 1.230. 



CONDUCTING POWER OF ACID. 



905 



Conducting: Power of Dilute Sulphuric Acid 
of Various Strengths. 

{Matthiessen.) 





Sulphuric 




Relative 


Specific 


Acid in 


Temperature. 


Resistances. 


Gravity. 


100 parts 


C.° 


Ohms per 




by Weight. 




cubic centimeters. 


1.003 


. 0.5 


16.1 


16.01 


1.018 


2.2 


15.2 


5.47 


1.053 


7.9 


13.7 


1.884 


1.080 


12.0 


12.8 


1.368 


1 . 147 


20.8 


13.6 


.960 


1.190 


26.4 


13.0 


.871 


1.215 


29.6 


12.3 


.830 


1.225 


30.9 


13.6 


.802 


1.252 


34.3 


13.5 


.874 


1.277 


37.3 


. . . 


.930. 


1.348 


45.4 


17.9 


.973 


1.393 


50.5 


14.5 


1.086 


1.492 


60.6 


13.8 


1.549 


1.638 


73.7 


14.3 


2.786 


1:726 


81.2 


16.3 


4.337 


1.827 


92.7 


14.3 


5.320 


1.838 


100.0 


• • • 


. . . 



Conducting- Power of Acid and Saline Solutions. 

Copper (Metallic) at 66° F 100,000,000. 

Sulphuric Acid 1 Measure \ 

Water 11 Measures ( QC n annY . n ^ r : rn „*. , 

(Equal to 14.32 parts by weight of Acid in 100 ( y *' U approximate. 

parts of the mixture), at 66° F / 

Sulphate of Copper, saturated solution at 66° F. 6.1 
Chloride of Sodium, saturated solution at 66° F. 35.0 
Sulphate of Zinc, saturated solution at 66° F. . 6.4 



SWITCHBOARDS. 

Revised by H. W. Young, B. P. Rowe and E. M. Hewlett. 

The object of a switchboard is to collect the electrical energy in an installa- 
tion, for the purposes of control, measurement and distribution. 

In small stations this is accomplished by concentrating the energy at a 
single place. In the large modern stations this is often impractical, and it 
is, therefore, customary to concentrate only the control and measuring 
apparatus. 

There are two general types of switchboards: 

(1) IMrect-Control Panel Switchboards, in which the switching 
and measuring apparatus is mounted directly on the switchboards. 

(2) Remote-Control Switchboards, in which the main current 
carrying parts are at some distance from the contro^ng and measuring 
apparatus. This type may again be divided into two ivisions, viz.: hand- 
operated remote-control, and power-operated remote-contro! apparatus. The 
best modern power-operated apparatus is electrically operated, although 
there are a few installations which have employed compressed air. 

The above general types may both be sub-divided into Direct-Current 
and Alternating-Current Switchboards, and there are numerous and distinct 
classes in each subdivision. 

It is customary to mount apparatus and switching devices for low-tension 
service up to and including 750 volts directly on the face of the switchboard 
panels unless provided with suitable insulating covers or is out of reach of the 
operator. 

If the plant is of small capacity, the switching devices and conductors may 
be provided for on the rear of the panels. Heavy capacity plants from 2200 
to 6600 volts, however, are invariably remote control, and nearly always 
electrically operated. 

In all high-tension plants from 6600 to 33,000 volts the switchboard is in- 
variably remote control, and if of heavy capacity it is invariably electrically 
operated. In large stations, for pressures above 33,000 volts, switchboards 
are invariably electrically operated remote control. In small capacity 
installations where the high-pressure service consists of only one or two 
incoming lines, which will not warrant expensive remote control switches, 
a set of simple fused circuit breakers or expulsion fuses are often installed 
and a switchboard dispensed with. Cut out switches are used, however, 
in addition, for disconnecting the lines. 

Design of Direct-Control Panel Switchboards. — In de- 
signing buildings for control stations or isolated plants, the switchboard 
should be located in an accessible place, with plenty of room in front and 
rear. If care is taken in locating the various panels with respect to the 
machines and feeders to be controlled, much unnecessary expense and com- 
plication may be avoided. 

If extensions to switchboards are expected, which is usually the case, 
panels controlling generators should be together at one end of the switch- 
board, and those controlling feeders at the other end. When total output 
panels are used, they are placed between the generator and feeder sections. 
It is advisable, however, in some special cases, in order to save copper in 
the busses and simplify the station wiring, to intermingle the generator and 
feeder switches although even in this case it is desirable to group the gen- 
erator indicating devices together and likewise those of the feeders. 

Unnecessary complications and extra flexibility being at the expense of 
simplicity are always to be avoided. For instance, in a majority of cases 
it would seem unnecessary to provide more than one set of bus bars. 

Plainness, neatness, and symmetry in design should be aimed at, and 
nothing placed on the switchboard which has no other function than orna- 
mentation. 

Sufficient indicating and recording instruments should be used to deter- 

906 



SWITCHBOARDS. 907 



mine if the machines are working efficiently, to obtain a record of the output 
of the feeders, to detect external or internal troubles, and to check with 
records obtained from outside sources. The degree of accuracy required in 
the switchboard instruments depends entirely upon the conditions involved, 
greater accuracy being required where power is bought or sold. Instru- 
ments which are accurate to within 2 per cent of the full scale deflection will 
generally fulfill all requirements. 

Switchboards are now standardized, covering a large range of requirements, 
and standard panels are advisable for general use, although special conditions 
may usually be met with small modifications of the standards. 

For ordinary direct-current switchboards, 4 feet is little enough behind 
the panels. In any case there should be a clear space between the connec- 
tions on the panels and the wall of 2\ to 3 feet. For heavy direct-current 
work and most alternating-current work it is often necessary to have 6 to 
8 feet behind the panels. 

Hand-control panel switchboards may not be advisable in direct-current 
stations where capacities are large, and in such cases remote-control installa- 
tions should be considered. It is likewise inadvisable to design switchboards 
of this class for heavy capacity alternating-current circuits of 2200 volts or 
upward, as the conductors for such service should be specially isolated. 

It should be noted especially that heavy capacity conductors arid switch- 
ing devices for circuits of 4000 alternations and above should be avoided, 
on account of excessive heating" to be met with due to eddy currents in the 
conductors. It is doubtful if satisfactory switching devices can be easily 
procured, which will carry currents of more than 3000 amperes at 7200 
alternations or the equivalent, and such devices require special design and 
expense. 

In locating switching apparatus it is usually assumed that dynamo leads 
come up from below, and feeder wires go out overhead except that under- 
ground feeders naturally. go out below. 

In order to avoid a very unsightly complication of wiring and apparatus 
on the rear of switchboards, it is best to locate series and voltage trans- 
formers apart from the switchboard on the incoming and outgoing cables, 
if at all possible, and to make all large rheostats operate with sprocket and 
chain, thus locating the rheostats separate also. Any extensive system of 
fuses to be supplied on the rear should preferably be provided for on a sepa- 
rate framework. 

The material from which panels should be made varies with the service. 
Plain slate can be used for any panels where the potentials are not above 
1200 volts. This slate may be either plain, or oil filled, or it may be given a 
black finish. The black enamelled slate is very satisfactory for use where 
oil is prevalent, but it shows scratches easily, and is not easily repaired if 
chipped. The most popular finish is the natural black oil finish slate, which 
may be made oil proof, and is a durable dead black. It is easily replaced when 
damaged. 

For switch bases and panels not requiring finish, soapstone is often used 
as it is a better insulator than slate, the latter being liable to contain con- 
ducting veins. Such slate should be rejected. 

Marble is largely used for switchboard panels because of its good insulating 
qualities. Many varieties are available, the most common being the white 
Italian, pink or grey Tennessee, and several varieties of blue Vermont marble. 
The colored marbles do not show oil stains as readily as the white varieties, 
and present a more pleasing appearance. The blue Vermont marbles are more 
uniform in coloring, and therefore easier to match; but if absolute uniformity 
in this respect is desirable, it is advisable that all panels be given a black marine 
finish, as it is often difficult to get new panels with exactly the same shades and 
markings as those it is desired to match, marble being a natural product. 

Standard Central Station switchboard panels are commonly made 90 inches 
high, and composed of two or three slabs. The upper slab of a two-piece 
panel is usually from 60 to 65 inches high, the lower one being from 25 to 30 
inches high. The General Electric Company's three-section panels are upper 
and middle sections 31 inches each and the lower section is 28 inches, the corre- 
sponding Westinghouse standard being 65 and 25 inches. The Westinghouse 
three-piece panel has an upper slab 20 inches high, middle slab 45 inches 
high and lower slab 25 inches, the 20-inch slab being provided primarily to 
permit circuit breakers to be directly mounted thereon, and allow of easy 
removal in case of substitution or repairs. 



( 



908 



SWITCHBOARDS. 



The General Electric Company also makes panels of any sizes up to 48 inches 
high and I5 inches thick for isolated plants. Panels 48 inches high are mounted 
on 76-inch pipe supports, the Westinghouse standard for similar service being 
48 inches high and 1£ or 1£ inches thick as required. 

Each panel is beveled I to \ inch all around the front edges, the dimen- 
sions being measured from the edges of the panel, and not across the face of 
the level. 

Switchboard frames for very heavy panels are often made of channel iron 
tees or I-beams. The Central Station Switchboard frames are made of steel 





Fig. 2. Method of Joining Ad- 
jacent Panels. 




Fig. 1. 



Fig . 3 . Channel Foot for Switch- 
board Frame. 



angle bars varying from 2J X U X i inches to 3 X 2 X i inches or lj-inch 
gas pipe. The angle bars are supported in an upright position on a level strip 
which rests on the floor. This may be of slate, an inverted channel iron, or a 
hardwood plank. 

The panels are bolted to the narrow web of the angle bars and the adjacent 
angles bolted together through their wide webs. (See Fig. 2.) 

Another method used with panels which carry a moderate weight of appa- 
ratus is to make a frame of iron piping, secured to the panels by means of 
suitable iron supporting clamps. 



SWITCHBOARDS. 



909 



The framework of all switchboards should be insulated from ground when 
used on systems of 600 volts or less. In high-tension alternating-current 
systems, it is necessary to ground all framework to carry off static dis- 
charges, and to insure safety to the operator, should he touch the frame- 
work. For securing the frame in a vertical position, rods are used with or 
without turnbuckles, or else angle iron braces. 

As a general thing, alternating and direct-current panels should never be 
intermingled, especially when this involves the mingling of conductors on 
the rear. 

It is recommended that illuminating lamps be omitted from the front of 
switchboards, and that the instruments be illuminated by lamps in front of 
the same. 

The copper bars and connections on the rear of switchboards should be 




^Gasppe . 
i A T A £* c/ter oas °° r supports 



-^p Supports for * rnoQstab 

pvnen moan teat on 
tQpo/ia/. 



■+-lJfGcrspJpG 



Fig. 4. Showing Method 
of Bracing Switchboard 
Panel to Wall. 



>. Showing Gaspipe 
Framework. 



carefully laid out in order that the current may be carried economically and 
without overheating, and especially to prevent undue crowding and insure 
a neat and workmanlike appearance. The best practice requires that bus 
bars be not placed near the floor. Switches, circuit breakers and other 
apparatus are connected up with bare copper strap or insulated wire as 
occasion requires, bent in suitable forms. Where bus bars are not rigidly 
supported, it is not recommended, as a rule, to have long studs on the appa- 
ratus, projecting out far enough to connect to the busses, as the strain on 
the apparatus due to the weight of the busses may affect the adjustment 
of electrical contacts. Except for small switchboards the bus bars are 
usually supplied with insulated supports. 

Bare flat or round copper bars are now used almost universally for con- 
ductors on low-potential switchboards, the flat bar being usually preferred 
on account of ease in making connections and the facility with which addi- 
tional capacity may be provided for. The prevailing thicknesses vary from 
& to \ inches with widths proportioned to suit the capacity. The size of 
copper conductor is usually figured out on the basis of 800 to 1000 amperes 
per square inch of cross section. By properly laminating the bars, even verv 



910 



SWITCHBOARDS. 



heavy currents may be provided for on this basis. Contact surfaces should 
be figured on a basis of 100 to 200 amperes per square inch according to the 
method of clamping, bolting, or soldering. Steel bolts are used in clamping. 
Care must be taken, however, with alternating-current circuits to see that 
iron clamping plates and bolts do not form complete magnetic circuits and 
cause undue heating, due to eddy currents set up in the iron. 

Connections and apparatus for carrying current should be guaranteed to 
carry their normal current at a temperature rise not exceeding 30° C, above 
the surrounding air. Rolled copper should be used for conductors to secure 
the best conductivity, but it is often necessary to use copper or brass castings. 
As their conductivity is usually low, such materials should be avoided as 
much as possible. Where it is necessary to use castings they should be of 
new metal only and care should be taken to insist on a standard of conduc- 
tivity for each piece where such a condition counts. The ordinary mixtures 
vary from 12 to 18 per cent according to mixture. A conductivity of 50 per 
cent may be considered high and sufficient, but it is not obtainable in a 
regular brass casting. 

The following table from "Modern Switchboards," by A. B. Herrick, gives 
percentages of mixtures with resulting conductivity as compared with 100 
per cent copper: 



% 


% 


Conduc- 


% 


% 


Conduc- 


Copper. 


Zinc. 


tivity. 


Copper. 


Tin. 


tivity. 


98.44 


1.56 


46.88 


98.59 


1.41 


62.46 


94.49 


5.51 


33.32 


93.98 


6.02 


19.68 


88.89 


11.11 


25.50 


90.30 


9.70 


12.19 


86.67 


13.33 


30.90 


89.70 


10.30 


10.21 


82.54 


17.50 


29.20 


88.39 


11.61 


12.10 


75.00 


25.00 


22.08 


87.65 


12.35 


10.15 


73.30 


36.70 


22.27 


85.09 


14.91 


8.82 


67.74 


32.26 


25.40 


16.40 


83.60 


12.76 




100.00 


27.39 




100.00 


11.45 



All minor connections to bus bars such as switch leads, feeder terminals, 
or any attachments whatsoever, whether clamped, bolted or soldered, should 
have ample contact surface contact rated at 100 amperes per square inch, 
and all round conductors should be cup-soldered to flat lugs leaving proper 
amounts of contact surface. 

Cup-soldered connections should enter the sockets from two to three 
diameters. All permanent joints of this nature should be soldered, as 
required by the National Board of Fire Underwriters. Where it is essential 
to leave a joint that may be easily disconnected, the old style sleeve or 
socket with binding screws can be used, but the connections should enter 
from four to ten diameters to make a secure connection. 

An exceedingly clever device to take the place of the connection referred 
to or to use in place of cup-soldering is the Dossert joint which is quickly 
and easily applied to the end of a wire or cable, and is so designed as to 
insure the full conductivity of the conductor to which it is applied. 

The tables given below furnish the electrical constants of copper and 
aluminum bars which are most likely to be of use to the switchboard designer. 
The current which any given section may carry is calculated upon the basis 
of a load factor of 50 per cent, and the densities given are those which for 
average conditions of radiation would result in a temperature rise of about 
10 degrees Centigrade. Where the load factor is to be 100 per cent, and it 
is desired to keep the heating within the above limits, the current densities 
must be halved. 

The data given show in an interesting manner the relative values of copper 
and aluminum in switchboard construction. 



COPPER BAR DATA. 



911 



Copper Bar Data. 

The Cutter Company. 



Size. 


Amps. 


Amps. 

per 
Square 
Inch. 


Circular 
Mils. 


Square 
Mils. 


Ohms 
per Foot. 


Weight 

per 

Foot. 


1 X i in. ... 


433 


1732 


318,310 


250,000 


.0000336 


.97 


H X i in. . 




530 


1696 


397,290 


312,000 


.0000269 


1.21 


UXi in. . 




626 


1669 


477,465 


375,000 


.0000223 


1.45 


HXi in. . 




725 


1657 


556,400 


437,000 


.0000192 


1.70 


H X t in. . 




676 


1442 


596,830 


468,750 


.0000179 


1.82 


HXi in. . 




798 


1418 


716,200 


562,500 


.0000149 


2.18 


If X f in. . 




916 


1395 


835,600 


656,250 


.0000128 


2.54 


2 X 1 in. . 




1035 


1380 


954,930 


750,000 


.0000112 


2.92 


2i X f in. . 




1154 


1367 


1,074,300 


843,750 


.00000995 


3.27 


24 X 4 in. . 




1500 


1200 


1,591,550 


1,250,000 


.00000672 


4.86 


2J X f in. . 




1715 


1097 


1,989,440 


1,562,500 


.00000537 


6.07 


2 X 4 in. . 




1222 


1222 


1,273,240 


1,000,000 


.00000840 


3.89 


No. 0000 B. & 1 


:J. 


267 


1606 


211,600 


166,190 


. 0000505 


.64 


4 in. round . 




305 


1552 


250,000 


176,350 


. 0000428 


.76 


| in. round . . 




426 


1388 


390,625 


305,796 


. 0000273 


1.18 


f in. round . . 




560 


1267 


562,500 


441,787 


.0000190 


1.71 


1 in. round . . 




861 


1096 


1,000,000 


785,400 


.0000107 


3.05 



Aluminum Bar Data. 

The Cutter Company. 



Size. 


Amps. 


Amps. 

per 
Square 
Inch. 


Circular 
Mils. 


Square 
Mils. 


Ohms 
per Foot. 


Weight 

per 
Foot. 


1 X i in. ... 


347 


1388 


318,310 


250,000 


.0000534 


.291 ] 


HXi in. . 




424 


1360 


397,290 


312,000 


.0000428 


.362 


HXi in. . 




500 


1334 


477,465 


375,000 


.0000356 


.435 


If X i in. . 




580 


1327 


556,400 


437,000 


.0000305 


.507 


H X f in. . 




530 


1131 


596,830 


468,750 


. 0000285 


.544 


14 XI in. . 




638 


1130 


716,200 


562,500 


. 0000237 


.653 


If X f in. . 

2 X I in. . 




733 


1117 


835,600 


656,250 


. 0000203 


.762 




830 


1107 


954,930 


750,000 


.0000178 


.871 


2i X f in. . 




925 


1096 


1,074,300 


843,750 


.0000158 


.980 


24 X 4 in. . 




1200 


960 


1,591,550 


1,250,000 


.0000107 


1.45 


24 X f in. . 




1400 


897 


1,989,440 


1,562,500 


.00000855 


1.81 


2 X 4 in. . 




980 


980 


1,273,240 


1,000,000 


.0000134 


1.16 


No. 0000 B. & 


3. 


211 


1266 


211,600 


166,190 


.0000803 


.193 


4 in. round . 




244 


1260 


250,000 


176,350 


.0000680 


.228 


f in. round . , 




340 


1108 


390,625 


305,796 


.0000436 


.355 


f in. round . , 




448 


1013 


562,500 


441,787 


.0000302 


.513 


1 in. round . . . 


690 


880 


1,000,000 


785,400 


.000017 


.911 



912 SWITCHBOARDS. 



Circuit breakers, if required to open circuits carrying heavy loads, should 
be mounted at the top of the panels to give the arc plenty of room to rise 
without scorching the instruments or the panel, and to keep it above the 
attendant's head. Instruments should be mounted below the circuit break- 
ers, while the lower portion of the panel should be utilized for switching 
devices. 

Switches, circuit breakers and fuses are usually rated at their maximum 
continuous ampere capacity and for this reason care should be taken in 
selecting these devices. Take into account the one hour, two hour and 
three hour overload guarantee on the machines. Indicating instruments 
should have scales calibrated to read in excess of the overload guarantee of 
the machines to which they are to be connected. It is usually good practice 
to have the needle about in the middle of the scale at normal load, but a 
good reading should be obtained as low as one quarter load. Meters affected 
by stray fields should be kept away from the influence of connections carrying 
heavy currents. 

Panel switchboards for small capacity stations for alternating-current 
circuits from 480 to 3300 volts are usually supplied with oil switches, 
mounted on the back of the panels, with handles for manual operation on 
the front. In large stations, however, these are usually replaced by remote- 
control switches. 

Insulation Distances. — In high voltage switchboard work where 
there are bare conductors, safe distances must be maintained between the 
conductors and from the conductors to the switchboard structure. The 
striking distance through air may be somewhat less than the distance over 
surfaces. The air distance should not be less than two and one half times 
the striking distance of the given voltage as taken from the curve on page 
462, and the surface distance should not be less than three times the air 
distance allowed for the given voltage. It is obvious that the greater the 
distance the greater the factor of safety ; and in large capacity stations this 
greater factor of safety is usually advisable on account of the greater insur- 
ance given by the use of greater distances. 

The creepage distance to be maintained in the switchboard depends upon 
many conditions some of which are: The material of the surface; the con- 
tour of the surface; the liability to collect dust and the properties of the dust; 
and the amount of moisture in the atmosphere. 

aheh^itogcirheit switchboard 

The instruments, switches, etc., required for the various types of panels 
are listed below, for assistance to the engineer when designing a switch- 
board. Each type of panel will be described individually. 

Equipment of 3-Phaie Generator Panels. 

3 Ammeters (one is sufficient for practically balanced loads or may 
be connected by means of plugs or ammeter transfer switches, so as 
to read the current in either of the 3 phases) . 

1 Voltmeter. 

1 Polyphase indicating wattmeter. 

1 Field ammeter. 

1 Polyphase integrating wattmeter (optional). 

1 Wattless component indicator or power-factor indicator (optional). 
The first instrument indicates the useless watts and the rheostat 
should be adjusted to reduce them to a minimum. The power- 
factor indicator is used for the same purpose, but does not give a 
direct indication of the idle currents at all loads. 

1 Voltmeter switch for reading voltage on either of the 3 phases 
(on balanced systems this is usually omitted and voltmeter per- 
manently connected to one phase). 

1 Synchronizing switch (one synchronism indicator can be used for 
all generators). ...-. „ ,. 

1 Field rheostat with chain operating mechanism (small machines 
may have the rheostat mounted at the back of the panel). If 
electrically operated rheostats are used the handwheel would be 
replaced by a controlling switch. 



ALTERNATING-CURRENT SWITCHBOARD PANELS. 913 



1 Field switch with discharge clips. 

1 Discharge resistance for field circuit. 

1 Non-automatic main switch (controlling switch required if oil switch 

electrically operated is used). 

2 Current transformers (3 transformers are necessary if neutral oi 

generator is grounded). 
Potential transformers (3 potential transformers are desirable if 
neutral of generator is grounded, but one is required if used only 
for synchronizing). Both may be omitted on circuits of 600 volts 
and less, if all meters have their coils wound for operating at 
generator voltage. 
1 Engine governor control switch if governor is electrically controlled . 

If each alternator has its own exciter the exciter may also be controlled 
from the alternator panel, by the addition of an exciter field rheostat. 




< -VOLTMETER 



AMMETER 

INDICATING WATTMETER 

IELD AMMETER 

-RHEOSTAT HAND WHEEL 

/CIELD DISCHARGE SWITCH 

VOLTMETER PLUG RECEPTACLE 



Fio. 6. 440- and 600- Volt Three-phase Generator Panel. 



Two-phase generator panels have a similar equipment to the three-phase 
accept that but two main ammeters, two current transformers and two 
potential transformers are required. 



914 



SWITCHBOARDS. 









&%% 






gKg — ftgi 




o3 






o 



T3 

C 









ALTERNATING-CURRENT SWITCHBOARD PANELS. 915 




Ammeters 
f~ie/a//rr, meter- 

Vo/tmeter 

V%>ter>tia/ 

Y*ecejotac/e 

VfheosCot 

KO/oc rating 

\/Wecr>anisrr> 

ne/cf S*vrtc* 
Sync/ironiz T'ng 
\Kece0tocte- 

4Af Oi/SwitcH 




Connections fbr&ig/ne 
Governor Contra/ 
Motor ana" Switch 
when supp/fecf 



Generator 

BazA Z/ewofGanet 



Fig. 8. Two-Phase 2300- Volt Generator Panel. 




'« -/tm meters-' 

■ Vr~/e/cf /7mmet<3r 
Vo/tmeter 
\Potentfot 
\ftecejotac/e 

\Pheostat fieceptock 

Operating 
{Mechanism 

eic/ Switch 
^Synchronizing 
Wece/otac/e 




^ eent ' a A~fps£T_ 



T. Pi Oi/ Switch 




SwitchX 

Ammeter fir 

filternating\ 
Current \ 
Generator J _ 

&7CA V/eyvbffibnef 



J Starting 

\®' 

Synchronizing 

, Plugs ' 

Running 



Synchronizing Buses 



Ground Bus 



Connections forchpine 
GovernorControf ■ 
Motor ana 'Switch 
when supplied 



Fig. 9. Three-Phase 2300- Volt Generator Panela. 



916 



SWITCHBOARDS. 



Equipment of Single-Phase feeder Panel. 

1 Main ammeter. 

1 Compensating voltmeter (optional). As single-phase panels are 
invariably used for lighting it is necessary to maintain a constant 
potential at the point of distribution, and as each feeder circuit 
is likely to have a different load characteristic, potential regula- 
tors are frequently installed. The compensating voltmeter com- 
pensates for the ohmic drop or for both the ohmic and inductive 
drop in the line at all conditions of load and gives a direct indi- 
cation of the voltage at the center of distribution. 

1 Potential regulator and operating mechanism (optional). 

1 Main switch with automatic overload trip or automatic circuit 
breaker. 

1 Current transformer. 

1 Potential transformer if voltmeter is used. 

1 Time limit overload relay (optional). 

1 Single-phase integrating wattmeter (optional). 



Ammttert 



[Regulator 
Operotiryff 

\^tec^ar>>3rrt 



O0&3***** 



CeseJT 

I ToBusBars 

7r/joCo/£^~Zl\ Xfiutomat/c 
Currerit\ \\\o/l Switch 
Tronsfo rr 

\/?mmeter 




QrouncfBos 



L Iff htntno Arresters. 

Notfurn.isheaw/t/i 

Pane/ 

Back y/ew^f Pons/ 



Fio. 10. 2500- Volt Single-Phase Feeder Panels with Primary Ammeters 
and with Series Trip Oil Switches. 



ALTERNATINO-CURRENT SWITCHBOARD PANELS. 917 



Equipment of Three-Phase feeder Panels. 



Main ammeters for transmission lines used to detect any unbalancing 
due to leakage to ground. A single ammeter may be used if 
desired, with suitable plugs, to indicate the current in either of the 
three phases. (One ammeter is sufficient on feeders for induction 
motors and rotary converters, or on incoming lines in a sub-station.) 

Polyphase indicating wattmeter (optional). For power circuits in 
mills and mines. This wattmeter gives a sufficient indication of 
the output without the ammeters. 

Polyphase integrating wattmeter (optional). 

Oil break switch with overload trip, or automatic circuit breaker. 

Current transformers (three transformers are necessary if neutral of 
three-phase system is grounded). 

Potential transformers for wattmeters. 

Time limit overload relay (optional). The number of potential 
transformers can be reduced for a switchboard containing a num- 
ber of feeder panels by connecting two potential transformers to 
the busses and feeding all the wattmeters. 



r 


Q 




it 


6Z 








1. 




i 
1 
| 






LaT-J 




TfiO// Switches 



,-_ac*_«» L-24'STSwt- _J 




L/^htninp/ffresters. 
Not furnished w/tr) 
Pane/ 

BacA V/'ewof&we/ 



Fig. 11. 



2500- Volt Three-Phase Feeder Panels with Primary Ammeters 
and Series Trip Oil Switches. 



918 



SWITCHBOARDS. 



Equipment of Two-Phase feeder Panels. 

2 Main ammeters. 

1 Polyphase indicating wattmeter (optional). 

1 Polyphase integrating wattmeter (optional). 

1 Oil break switch with overload trip, or automatic circuit breaker. 

2 Current transformers. 

2 Potential transformers for wattmeters. 

1 Time limit overload relay (optional). The number of potential 
transformers can be reduced for a switchboard containing a 
number of feeder panels by connecting two potential transformers 
to the busses and feeding all the wattmeters. 

Equipment of Induction Motor Panels. 

1 Ammeter. 

1 Oil break switch with overload trip, or automatic circuit breaker. 

2 Current transformers. 

1 Time limit overload relay (optional). 

The various methods of starting induction motors are as follows: 

1. By Connecting* them Birectly to the Line. — This is sel- 
dom done except on motors under 10 horse-power capacity, because it pro- 
duces variation in the bus voltage unless the busses have considerable 
energy back of them. 

2. By Inserting' an Internal Resistance in the circuit of the 
motor by means of a switch on the motor shaft. 

3. By Introducing* an External Resistance in the rotor cir- 
cuit through collector rings. This resistance is cut in or out by a controller. 

4. By first Connecting* the Motor to Eow-Voltag-e Taps. 

— If the motor is fed from step-down transformers, it may first be con- 
nected to low- voltage taps on the transformer and then to the full- voltage 
connections. 

5. By Employing* a Starting* Compensator. — Many compensa- 
tors have an internal switch for starting; otherwise the panel should be pro- 
vided with switches to connect and disconnect the compensator. 





J LP»wL 



fndkjct/on MoCa* 



Fig. 12. 



2080- Volt Induction-Motor Panel for Controlling Motors having 
an Internal Resistance. 



ALTERNATING-CURRENT SWITCHBOARD PANELS. 919 



Equipment of Three-Puase Synchronous Motor Panels. 

1 Ammeter. 

1 Three-phase indicating wattmeter. 

1 Field rheostat with operating mechanism. 

1 Synchronizing switch. (The synchronism indicator will answer for 

any number of motors or the generator synchronism indicator 

may be used.) 
1 Main oil switch with automatic overload trip. 

1 Field switch with discharge resistance. 

2 Current transformers. 
2 Potential transformers. 

1 Time limit overload relay (optional). 

A synchronous motor driving a direct-current generator can usually be 
started from the direct-current side, in which case the synchronizing switch 
is necessary. If always started as an induction motor the synchronizing 
switch is unnecessary. 

The equipment of a two-phase motor panel is the same as for a three- 
phase, except that two ammeters should be used. 



Equipment of a Xnree-Phase Rotary Converter Panel. 

For rotary converters connected in the high-tension side of step-down 
transformers, the panel for the alternating-current side is the same for three- 
phase or six-phase machines. 

1 Three-phase integrating wattmeter (optional). 

1 Ammeter. 

1 Power factor meter. 

1 Main oil circuit breaker with automatic overload trip. 

1 Synchronizing switch (not necessary if rotary is started from the 

alternating-current side) . 
1 Starting motor switch (only used where rotary is started by a starting 

motor) . 

1 Switch for synchronizing resistance (only used where rotary is 

started by a starting motor). 

2 Current transformers. 

1 Potential transformer (if rotary is started from the direct-current 

side or by a starting motor). 
1 Time limit overload relay (optional). 

One method of starting a rotary converter is by connecting the alternating- 
current side first to fractional voltage taps on the transformers, and then to 
full-voltage connections. This is accomplished by means of a double-pole, 
double-throw switch on a separate panel for a three-phase converter, and two 
triple-pole, double-throw switches on a separate panel for a six-phase conver- 
ter, Fig. 13. Another method is by the use of a motor on the rotary shaft, 
as shown on diagram, Fig. 14. 

The rotary may also be started from the direct-current side. In either of 
the latter cases it is necessary to synchronize. 

In case several rotary converters must operate from the same bank of 
transformers, it is best to have a separate set of secondaries for each rotary. 
But in case of rotaries which must be parallel on the alternating-current 
side under such a condition, it is essential that reactances be provided in 
the circuits to prevent interchange of current between machines, and that 
switches be provided in the alternating-current leads. These are used as 
main switches in synchronizing and are usually mounted on the alternating- 
current panel. For the condition just described, the panel would contain 
the same list of apparatus mentioned above, except that these switches 



920 



SWITCHBOARDS. 



cruses 
^LPotent/a/ 
' \7ransfbrmer 



\\b/tmeter\ 
x \/lmmeter j 



~J Main 
_^— Buses 



Cou/2//r?& 



Potentio/ Transformer BuS. 






t 



^Resistance j 



fleceptac/e »J 4 



\Transformer 



-Lv 



^Grounded 
•Switch 



Current Transformer 



Synchronizing Buses 

Synchronizing 
Mug 



*iH* * *AA\. I WW 



SA> I 




fteact/ve Co// 

Two TP. P.F Switches 



Synchronizing Connections {Shown Dotted) 
forrfotaries Starting /corn D.C. £nd 



i0 5 >* 

1 To/Vext Transformer 

fuses 

To B/ower Motor * 
f?otary Converter* 

iflGh 13. Diagram of Connections. Three-Phase Rotary Converter 
started directly from Alternating-Current Side. 



ALTERNATING-CURRENT SWITCHBOARD PANELS. 921 



would be substituted for the automatic overload main switch and relay, 
and either automatic protection provided in connection with the switches 
or else a fuse in each lead. 

When a rotary converter must run inverted (i.e., to convert direct current 



FROM TRANFORMER3 
III 

OB 

2 FUCE 



6 PT.6YN. 

RECEP. 



• F.M.J ( VM. J 




Fio. 14. Diagram of Connections. Three-Phase Rotary Converter 
with Starting Motor. 



into alternating current), provision must always be made for starting the 
rotary from the direct-current side. 

Two-Phase Itotarr Converter Panels are essentially the same, 
but require two ammeters instead of one, and four-pole alternating-current 
switches. 



922 



SWITCHBOARDS. 



Equipment of Constant- Current Transformer Panels, for 
Series Arc or Incandescent liig-hting*. 

The primaries of these transformers may be controlled by an oil switch, 
with automatic overload trip, or by plug switches and fuses. 

The secondaries, being of small capacity, are usually controlled by 
plug switches. An ammeter should be connected in the secondary side to 
indicate the current and to detect grounds or open circuits. 

An integrating wattmeter on the primary side is a valuable adjunct to 
record the total power consumed. The diagram shown is that of a single- 
circuit transformer. Various modifications result from using multi-circuit 
transformers and introducing transfer systems in either the primary or 
secondary side. 




Open Circuiting 
Plug Jtritcnes^ 



Primory Aug Suvitcnes 
Tube Expulsion fuses 




Lightning Arrester 



Open Circ ult ing 
f/ug Quitches 
Constant. Current 
Transformer 



ffi Primary Plug S-kthii \ 




Current 
Transformer" 
when AHecCJSOryj 



Seconoory 
£Z- union Couplings 
AotenUof . 
Transformer 



Primary 



Fig. 15. Constant-Current Transformer Panel for Single Circuit. 



ARC SWITCHBOARDS. 



This line of switchboards represents an entirely different construction 
from that of ordinary switchboards. 

Extra flexibility makes it desirable, and small currents make it possible, 
to use plug connections instead of the ordinary type of switches. 

The function of arc switchboards is to enable the transfer of one or more 
arc light circuits to and from any of a number of generators. This trans- 
ferring is sometimes accomplished by means of a pair of plugs connected 
with insulated flexible cable; sometimes by plugs without cables, which 
bridge two contacts back of the board, or by a combination of cable plugs 
and plugs without cables. The type using plugs without cables is preferable 
because danger is eliminated, which would otherwise be possible to attendant, 
due to contact with exposed or abraded cables carrying high-potential 
current. 

The accompanying illustration shows an arc switchboard of the General 
Electric panel type, arranged for three machines and three circuits. The 
vertical rows of sockets are lettered and the horizontal numbered. The 
ends of the vertical bars are connected to the machines and circuits. Each 
of the bars is broken in three places, and the machine may be connected 
to its circuit by plugging across these breaks, thus making the bar con- 
tinuous; by removing any pair of plugs the machine may be disconnected. 

Cll, Ell and Gil are ammeter jacks, and are used in connection with 
two plugs connected with a twin cable, for placing an ammeter in the circuit. 
The six horizontal bars are for the purpose of transferring a machine or a 
feeder to some circuit other than its own. Each horizontal bar is provided, 
at one side of the panel, with a socket (A3, A4, A5, A7, A8, and A9) by 
means of which it can be connected with the horizontal bar on the adjoining 
panel. All ordinary combinations can be made by means of the bars and 



ARC SWITCHBOARDS. 



923 



plugs; but cable plugs are provided with each panel, so that when necessary, 
machines and feeders can be transferred without the use of the bar. These 
plugs and cables are intended for use only in case of an emergency. 

To run machine No. 1 on feeder No. 1, insert plugs in BIO, CIO, B6, C6, 




Fig. 16. 



B2, and C2. To shut down machine No. 2, and run feeders Nos. 1 and 2 in 
series on machine No. 1, insert a plug at C5, D5, C7, and D7, and remove 
plugs at C6 and D6; this leaves two circuits and two machines in series. 
Short circuit machine No. 2 by inserting the plug at E7. Cut out machine 
No. 2 by removing the plug at D10 and E10. Take out plug at D7. 



924 



SWITCHBOARDS. 



DIRECT-CrRRE^T SWITCHBOARD PAIEIS, 
Equipment of I».C. Generator Panels. 

1 Overload circuit breaker. 

1 Ammeter. 

1 Voltmeter switch. (One voltmeter will answer for all generators.) 

1 Field switch with discharge resistance (optional). 

1 Positive main switch. 

1 Negative main switch. (For railway service where the generator 
series coils are on the negative side, and the negative side is 
grounded, this switch should be replaced by a circuit breaker 
mounted near the generator, and connected in the armature lead.) 

1 Equalizer switch. (Mounted near the generator. For small capacity 
generators all three switches may be combined into a triple-pole 
switch mounted on the panel.) 

1 Field rheostat. 

1 Recording wattmeter (optional). 
For small machines, fuses may be substituted for the circuit breakers. 



^—POWER FACTOR METER 



SYNCHRONIZER LAMP 
SYNCHRONIZER PLUG RECEPTACLE 
AMMETER PLUG RECEPTACLES 

RHEOSTAT (IF NOT MOUNTED, 
"ON D.C. PANEL) 

SWITCH FOR SYNCHRONIZING, 
RESISTANCE 

SWITCH FOR STARTING MOTOR 



Equipment of A.C. and D.C Rotary Converter Panels. 

The equipment of a direct-current converter panel may be the same as 

i direct-current generator panel, but a field switch with discharge resistance 

is unnecessary and the cir- 
^ammet cu jt breaker in the nega- 

tive on grounded return 
system should be omitted 
as the necessary protection 
is secured on the alternat- 
ing-current side. The main 
switches, however, should 
all be single pole. 

Rotary converters 
started from the alternat- 
ing-current side may build 
up with reversed polarity, 
which will be indicated on 
the voltmeter. To change 
the polarity back to nor- 
mal, a double throw field 
switch is provided (usually 
mounted on the converter 
frame) for the purpose of 
momentarily reversing the 
field to "Slip a pole." To 
reduce the destructive in- 
ductive discharge of the 
field a multi-pole switch is 
used, each pole of switch 
breaking only two or three 
field spools. 

Rotary converters oper- 
ating on grounded return 
systems may have the neg- 
ative side connected direct- 
ly to ground without the 
interposition of a switch. 

Rotary converters start- 
ing from the direct-current 
side require a field-transfer 
switch, as well as a starting 

Fig. 17. Three Phase Alternating Current switch, which are usually 
Rotary Converter Panel for use with provided with the direct- 
Rotary and Starting Motor. current panel. A double- 
reading ammeter is usually 

provided, or else other provision to prevent damage to the meter by reversal 

of current. 




DIRECT-CUKRENT SWITCHBOARD PANELS. 



925 




TYPE C 

CIRCUIT BREAKER 



RHEOSTAT 

iANDWHEEL 



NEGATIVE 

MAIN SWITCH 

POTENTIAL RECCPTACLE 
POSITIVE 

MAIN SWITCH 



RECORDING 

WATTMETER 



Fig. 18. 



Westinghouse Panel for D.C. Generator or Rotary Started b> 
Starting Motor. 



62' 




t*. -/•>'!-. «£ 



Type C Form /< 
C/rca/t Breaker 



Ma/nBus Bar * 



TID rlmmetef* 
Potent/'o/BusW/rc Support i 
P/?eoJtat r/a/?c/tv/?ee/ 



■Potent/a/Peceptac/e 
• Card r/o/der 
Prteastat C/>a/n \ _ 

Opcrat/'rg Mechan/sm] " 
-L/$f>t/n$ Smv/'£c/> 
' type Q& Porm/4 Stv/tcS) 



■Pccord/n$ Wattmeter 
Wattmeter Pes /-stance - 




Fig. 19. 



Direct-Current Rotary Converter Panels. General Electric Panel 
Rotary Started Direct from A.C. Side. 



926 



SWITCHBOARDS. 



Bock view 

Positive Bus 



law Vo/toge 
ffe/eose. — 



eovott 
Lamps 



/Pes/ stance - ■ +►§ 
— £^J voltmeter 
Fuse h \ 

Z-urszzzzz." 



fuses 



L ig?~> t mg Sw/'t en j\ 

To Center stud „1 j 

of Lighting 5w/ Left j i 
on adjacent Pone/ j 

% I i 
Fuse (J ! 

Station Lights 




Rheostat 




II 

IX- ) To Aiorm Belt 

Low voltage Release Bus 

) Potential 

louses 



£ ^>eedUmtL 

Oev/CQ" 



^//egat/ve Bu$ Qroyndeaf 



Fig. 20. Connections of a Direct-Current Rotary Converter Panel. 



Equipment of a Three-Wire (Generator Panel. 

The Westinghouse three-wire generator combines in its system of con- 
nections all of the circuits which were required for the usual generating sets 
of an Edison three-wire system, and a double equipment of apparatus is 
required, as follows: 

2 Ammeters (operating from shunts located in armature leads of 

generator) . 
2 Circuit breakers, each either two pole or supplied with equalizer 

contacts, to open a main and equalized lead (with operating coil 

in the main lead) to trip together. 
2 Double-pole main switches. 
1 Double-pole two-way voltmeter plug receptacle. 

1 Field rheostat. 

2 Double-pole balancing coil switches. 



(If the unbalanced load is to be measured, a double-reading direct-current 
ammeter should be placed in the neutral return.) 

The connections for such a system are shown in diagram, Fig. 21. 



DIRECT-CURRENT SWITCHBOARD PANELS. 



927 




928 SWITCHBOARDS. 



Equipment of D.C. Feeder Panel. 

Direct-current feeder circuits should be protected from overloads by cir- 
cuit breakers or fuses. Circuit breakers should be used if overloads occur 
frequently, such as on railway and most power circuits. They should also 
be used for all large ampere capacity circuits — say above 600 amperes. 
Small feeder circuits may be controlled solely by a double-pole circuit breaker, 
but on large circuits a switch in series with a circuit breaker is necessary. 
The equipment should then consist of: 

1 Single-pole circuit breaker. 

2 Single-pole switches. (On grounded return systems the second 

switch will be unnecessary.) 
Ammeters and integrating wattmeters are optional devices. 

Equipment of D.C. IfEotor Panel. 

1 Double-pole automatic circuit breaker. 
1 Starting switch and resistance, 
or 

1 Single-pole automatic circuit breaker. 

2 Single-pole switches or one double-pole switch. 
1 Starting switch and resistance. 

or 

1 Double-pole switch. 

2 Inclosed fuses. 

1 Starting switch and resistance. 

Ammeters are optional, but are recommended for motors of large sizes. 

Either the circuit breaker or the starting switch should have a low- voltage 
release' attachment. The starting switch and resistance should be so con- 
nected that the field, when the switch or circuit breaker is opened, will 
discharge through the armature. 

Starting switches for motors starting under heavy torque should have at 
least eight steps. Motor- genera tor sets may properly be started with but 
three or four steps. 

As the starting resistances are invariably designed for intermittent service, 
starting switches, except in power stations where an electrical attendant is 
in charge, should be provided with a spring or other means to prevent the 
switch arm from remaining on an intermediate starting point. 

Hand-Operated Remote-Control (Switchboards. — Wher- 
ever it is desirable to install a plant of moderate size and obviate the 
necessity of having any high potential conductors on the rear of the switch- 
board, a hand-operated remote- control switchboard may be installed. The 
panels will have the same appearance on the front as any other hand-operated 
alternating-current switchboard, but the rear of the panels may be made 
safe and accessible with a neat arrangement of small wiring, inasmuch as 
all heavy conductors, meter transformers and accessories are mounted apart 
from the panels. A common method of providing for the switches and 
transformers mentioned is to mount them on a separate framework in some 
distant place and control the switches from the switchboard by means of 
bell cranks, levers and connecting rods. These latter are usually made of 
gas pipe. The framework used to support the switches is usually utilized 
to support the bus bars also. As the connections between the panel board 
and the switching structure are made by small secondary wiring for meters 
and instruments, and the bell -crank attachments permit of an infinite variety 
of combinations, the location of the switching devices may be selected to 
best suit the station wiring so long as the cranks and levers can be arranged 
to operate suitably ; the total length of any set of bell cranks and levers should 
not, as a rule, be greater than 12 feet, although longer runs than this will 
operate successfully under favorable conditions. 

Central Station Electrically Operated Switchboards. — 
The concentration of energy in large central stations requires that the measur- 
ing and controlling devices shall be concentrated also, in order to be under the 
hand of a single operator and enable him to have absolute control of the whole 
installation. This end is best attained by the use of electrically operated 
switchboard apparatus. 

Electrically operated switchboards may be divided into two classes, namely, 
alternating-current and direct-current equipment. As large • central stations 
almost invariably generate alternating current for distribution, the electrically 
operated switchboard is usually of the latter class. 



ELECTRICALLY OPERATED SWITCHBOARDS. 929 



Circumstances whicn Indicate the Wccesnity of Installing- 
Electrically Operated Switchboard Apparatus. 

First, switches used to control the circuits may be so heavy that they 
cannot be easily operated by hand. 

Second, the location of these switching devices can be made most conven- 
ient to the circuits to be controlled and apart from portions of the equipment 
which are liable to cause trouble, such as steam pipes, etc. 

Third, in case of accident to any of the apparatus, the operator may be 
located well away from the seat of trouble and is therefore not so liable to 
be frightened or lose his head in an emergency. 

Fourth, the entire absence of dangerous potentials at the center of control 
provides absolute safety for the operator. 

Fifth, the number of circuits and amount of power may be such that the 
control cannot be concentrated within a space of reasonable size unless 
electrically operated. 

Sixth, it may be necessary that the operator be located a long distance 
from the apparatus which he controls. 

Reliability of Service. — When the choice of an electrically 
operated switchboard is made, the next consideration is as to how much 
apparatus to install to insure reliability of service. It is possible to carry 
this idea to an unnecessary refinement in some cases, where the chances of 
a shut down are small and the consequences of it are not very disastrous. 
On the other hand there are some plants where no expense must be spared 
to provide against the contingency of a shut down even of a very short 
duration. The latter case requires much duplication of apparatus and great 
flexibility. 

Where a large number of feeders are used a circuit breaker is sometimes 
provided to connect between certain groups of feeders on the bus-bars, and 
is known as a group circuit breaker. Each feeder circuit of the group has 
its own individual circuit breaker to open automatically and relieve the 
group on the overload, but in an emergency the whole group can be switched 
on or off the circuit by means of the group circuit breaker. 

The value of this group circuit breaker for a single-throw system is doubt- 
ful except in cases where transfers of load must be very rapid and a large 
number of feeders are installed. It is more valuable in such a case on a 
double-throw system, because it enables the transfers from one set of bus- 
bars to the other to be made very rapidly and with a minimum number of 
switches, as one pair of circuit breakers will transfer an entire group of 
feeders instead of having two circuit breakers for each feeder circuit. There 
are four systems of connections for bus-bars commonly used. The first is 
the single-throw system, the second is the relay system, the third is the ring 
system, and the fourth is the double-throw system. Each of these may be 
made more flexible by dividing the bus-bars into sections by means of 
sectionalizing switches. 

Except in special cases it will be found that where any system is required 
to provide flexibility, the double-throw system will be most satisfactory. 

It is considered the best practice to provide disconnecting switches 
between all bus-bars and oil circuit breakers in order to permit a disabled 
switch to be isolated and repaired without shutting down the system. 

As the bus-bars form really the vital part of the system, it is necessary 
that care be taken to insulate them so that short circuits shall be impossible 
and that trouble on one set shall not communicate to another. 

Where absolute certainty must be insured against ^interruption of service, 
all conductors should be isolated from each other and all adjacent material 
made as fireproof as possible. In large stations this is attained by means of 
masonry structures and barriers and flame proof cables, with absence of 
inflammable material for supporting the cables, using cells for all fuses and 
apparatus liable to arc and all oil-insulated transformers that are so con- 
structed that danger from burning oil exists. This includes voltage trans- 
formers which are oil-insulated. 

The greater the energy involved the greater is the necessity for isolation, 
especially in plants of pressures under 45,000 volts. The isolation is most 
needed in heavy capacity stations of 2,200 to 13,000 volts and in some cases 
it is advisable up to 45,000 volts, if the use of compartments makes a more 
consistent layout. Isolation is, however, rarely advisable in stations above 



930 



SWITCHBOARDS. 



45,000 volts, as small isolated conductors well supported in air will in such cases 
prove quite satisfactory, while barriers or adjacent walls usually serve a3 so 
many grounds to insulate from. Whenever modern practice reaches such 
a point that extremely high voltage circuits carry heavy current capacities, 
however, barriers may be advisable, but this condition is not liable to be met 
with. 




Fio. 22. 



60,000-Volt Hydro-Electric Generating Station 
Sectional Elevation. 



932 



SWITCHBOARDS. 




BUS-BAR AND BUS-BAR STRUCTURES. 



933 



BO-BAR A1¥B BUS-BAR STRUCTURES. 

The bus-bars of a high-tension central station make up the backbone of the 
installation. As the entire distribution depends upon them, the design of 
the station as a whole should be executed with this fact in view. The bars 
should be entirely isolated from all danger from arcs, short circuits or flashes. 
All large stations should be laid out with a suitable arrangement of bus-bars, 
to guard against interruption of service from unforeseen causes and to pro- 
vide a means whereby circuits can be installed and connected with facility. 

The modern bus-bar structure for 2,200 to 33,000 volts is of brick or con- 
crete with each bus-bar of opposite potential in its own separate com- 
partment, well supported on porcelain insulators. 

The shelves or barriers in such a structure are usually of soapstone or con- 
crete. Some of these structures are enclosed entirely, one side having 
removable doors, while others are made with the entire side open for inspec- 
tion and facility in making connections and alterations. The bus-bars, 
being well protected and insulated, are usually composed of bare copper. 

For higher voltages than above mentioned a different form of bus-bar sup- 
port is generally used, and the connections to the bus-bars are made with 
wire or cable well supported on suitable insulators. Diagrams of a few 
typical arrangements of bus-bars and oil switches follow: 



Operae/s?pAfecfo/>/'s/f 



•Socpseone orStote 









*{4)+/4U4f+/4*iSpi/4i^4~ 



•e 






:=TJJT 


— p 










iA 






3E - 1 

H ° 




^ 






i If 


E B 




'WMMMMMXa 



TYPICAL ARRANGEMENTS OP WMJD VOLT BUS-BARS, ELECTRICALLY OPERATED OIL SWITCHES, AND 
DISCONNECTING SWITCHES IN THREE-PHASE STATIONS 

Fig. 25. 



934 



SWITCHBOARDS. 




fi 






« 



3 



2 



BUS-BAR STRUCTURES. 



935 



General Arrangement of Switching- Devices. — In addition 
to the masonry required for the bus-bars, there must be provided struc- 
tures for the oil circuit breakers. The elements are contained in struc- 
tural work of brick or concrete. On account of this construction and the 
desirability of making connections between the apparatus in the most safe 
and direct manner, it is generally necessary to build structures in galleries 




Fig. 27. Double-Deck Oil Circuit Breaker and Bus-Bar Structure. Two 
Sets of Main Bus-Bars and Two Sets of Auxiliary Bus-Bars. 



one above the other, or if galleries are not to be considered, then a basement 
must be provided to take a portion of the gear. The simplest switchboards 
are usually double decked, while others require three or four galleries. For 
a given amount of apparatus, a double-decked arrangement requires the 
longest galleries and more material for bus-bars. It is the simplest, however, 
and often the most economical when the switchboard apparatus is located 
near the generators and transformers, and saves long and expensive lines of 
connecting cables. On the other hand, where the galleries must be small, a 
three-deck arrangement is more satisfactory. 



936 



SWITCHBOARDS. 



In each particular case the conditions of space, accessibility, etc., must 
determine the most suitable place for the structure and the best relative 
arrangement of the circuit breakers and bus-bars. 

The series and voltage transformers for the operation of the oil circuit 
breakers, meters, etc., in almost every care are placed in the structure, the 
best arrangement depending upon local conditions. 




Fig. 28. 



Double-Deck Oil Circuit Breaker and Bus-Bar Structure. 
Sets of Three-Phase Bus-Bars. 



Two 



Isolation of Conductors. — When barriers are used each conductor 
is confined to its own compartment and in case of accidental ground or 
short-circuit the flashing or combustion is confined to the conductor involved 
and prevented from destroying neighboring conductors. 

Barriers, while fire-proof, are not necessarily made of insulating material, 
although, were it not for the expense, they might well be made of such 
material. They are frequently made of brick, masonry, concrete, or tile, 
while in places where insulated barriers are desired, soapstone is the most 
favored material. It absorbs less moisture than marble, but the insulating 



BUS-BAR STRUCTURES. 



937 



properties cannot be depended upon. The cost is a little less. Soapstone 
is readily obtained in any reasonable size or shape, and is easily drilled and 
nut when fitting is necessary at the place of erection. 

When the barriers and compartments of the switchboard structure are 
made from any of the above-mentioned materials, they should be treated as 




Fig. 29. Three-Deck Oil Circuit Breaker and Bus-Bar Structure. Two Sets 

of Bus-Bars. 



grounds with reference to high-tension circuits. It is true that vitrified 
brick and concrete, when very dry, are more in the nature of insulators than 
conductors, but the tendency of all such materials, and even soapstone, is 
to absorb more or less moisture, preventing any absolute dependence bein* 

f)laced upon them as insulators, and all conductors must, therefore, be msu- 
ated from them. 



938 



SWITCHBOARDS. 



Each bus-bar is in a separate fire-proof structure, and each pole of the oil 
circuit breaker isan independent fire-proof compartment. Masonry barriers 
separate the leads from the oil circuit breakers to the bus-bars, and to the 
outgoing lines. Wherever it is desirable to use disconnecting switches 
between the circuit breakers and the bus-bars or circuit breakers and the 



/ \ Oz/C/nzc'/f' 




Fig. 30. Three-Deck Oil Circuit Breaker and Bus-Bar Structure. 
Sets of Main Bus-Bars and Two Sets of Auxiliary Bus-Bars. 



Two 



outgoing lines on circuits not exceeding 13,000 volts, these disconnecting 
switches can be mounted as shown in Fig. 30, which also illustrates one 
of the many ways of arranging circuit breakers and bus-bars in two galleries. 
Cells for Voltag-e Transformers and fuses. — In installa- 
tions of this nature the voltage transformers are connected to large sources 
of power, and it becomes necessary to avoid possible damage to the sys- 
tem by one of them burning out; it is therefore customary to protect 



BUS-BAR STRUCTURES. 



939 



them with enclosed fuses, the fuse and transformer being isolated in their 
own individual cell in keeping with the practice of isolation which has been 
described. 

When the fuses are installed as described it is often desirable to close the 
cells with doors. 

Hig-h-Tension Conductors. — Manufacturers supply rubber-insu- 
lated cables for use up to a certain voltage, which can be relied upon for a 
long time in regard to insulation; but it is a well-known fact that rubber 
deteriorates with age and the higher the voltage the faster the deterioration, 
when conditions are favorable; so it is the best practice in all high-tension 
installations not to depend upon the rubber insu- 
lation, but to support the conducting cables on 
porcelain insulators and keep them away from 
all grounds and other conductors. The insulation 
on the cable serves, under such conditions, only 
as a possible preventive of troubles due to acci- 
dental contact therewith. This does not mean 
that the insulation is useless, as it might at times 
prevent loss of life or serious troubles due to 
accidental contact. 

Isolated cables laid against the grounded 
structure or covered with lead are subjected to 
strains, which might sooner or later break the 
insulation down. 

Lead-covered, paper-insulated cables are seldom 
used in high-tension switchboard structures. 
Some of the best cables obtainable are insulated 
with rubber. As the rubber, however, is com- 
bustible and easily takes fire from flash, manu- 
facturers supply cables, when required, covered 
with fire-proof braid of asbestos, or with the outer 
braid saturated with a fire-proof paint to prevent 
accidental burning of the rubber cover. For 
very high voltages, cables insulated with wrap- 
pings of impregnated cambric may be obtained, 
with or without a flame-proof covering. 

The terminals of cables used in the construc- 
tion of high-tension switchboards can be insulated 
with any good material such as oiled linen coated 
with shellac, but this should not be relied upon to 
prevent {accidental contact with live terminals, 
and no attempt should be made to insulate for 
safe handling, as the only time to safely handle a 
high-tension cable is when it is absolutely dead. 

Flame-Proof Covering's. — In order to prevent the flame from an 
arc setting fire to the insulation of a cable and being thereby communicated 
to other cables or setting fire to the building, flame-proof coverings are often 
used. These coverings are always supplied by the cable companies, being 
purchased under specifications which require that they shall meet the 
requirements of the National Board of Fire Underwriters. 

When installing such cables they must in every case be supported on 
insulators, and not carried in ducts, as the flame-proofing is a poor insulator 
and when saturated with moisture will serve as a conductor. For the same 
reason the covering must be stripped away from all live terminals a suitable 
distance for insulation purposes. 

Auxiliary IMrect-Current Circuits. — The direct current for 
operating the oil switches and other apparatus may be obtained as follows: 

From auxiliary storage batteries. 

From motor-generator sets. 

From direct-current exciter systems or other direct-current bus-bars. 

It must be especially noted that where the exciter system is controlled by 
a Tirrill regulator, the voltage fluctuation is likely to be so great that it cannot 
be relied upon for standard electrically operated apparatus. In this case 
either a small storage battery or a motor-generator set must be relied upon 
to supply the energy. In cases where a storage battery must be employed, 
owing to such considerations, and no charging current is available, a mercury 
rectifier may be relied upon to charge the battery. 




Fig . 3 1 . Three-Deck Oil 
Circuit Breaker and 
Bus-Bar Structure. 
Two Sets of Bus-Bars. 



940 



SWITCHBOARDS. 



fT\ xtCN /TX 



In cases where it is absolutely necessary to operate oil circuit breakers 
from direct-current exciter systems which are connected up to Tirrill regu- 
lators, the coils can generally be specially wound so as to operate at a low 
voltage, and the magnetic circuit be designed to saturate at high voltage so 
as to prevent the switch closing with too much force. 

Controlling* and Instrument Switchboard. — Under this head 
will be considered the installation of controlling switches and accessories 
that control electrically operated oil switches. 

In this connection it is essential to make sure that direct current is available 
at a suitable voltage to operate the electrically operated devices. The 
standard controlling devices are designed to operate from 125, 250 or 500- 
volt circuits, but when the potential is liable to drop below 80 volts, operating 
coils must be specially provided for the low voltage. The controlling appa- 
ratus can be mounted on the face of the switchboard panel together with 
the instruments where the system is simple and an inexpensive arrangement 
is desired. Nearly all large stations have the generator-control apparatus 
mounted on control desks or pedestals. A feature of some control outfits 
is the use of miniature bus-bars with lamps and indicators in the circuits. By 
means of these bus-bars the entire main station connections are embodied 
in miniature on the controlling desk, and, if the indicators or lamps are 
placed in the miniature circuits, the switching operations can be seen to take 
place when the operator moves his controller exactly the same as they occur 
in the main circuit. When the desk type switchboard is used, it is usually 
placed directly in front of the instrument switchboard and the operator has 
his control apparatus arranged as nearly as possible opposite the respective 
instrument panels. 

Nearly every large installation starts with a few generating units and 
increases as the demand for power increases. For this reason it is desirable 
that the structure used for carrying the control apparatus be so designed to 
admit of extension to meet future demands, or be 
made in the form of pedestals carrying the various in- 
struments. Such controlling table or pedestal should 
generally contain controllers, indicators and lamps for 
the oil circuit breakers, synchronizing plugs and 
lamps, voltmeter plug, electrically operated rheostat 
controller, a controller for the engine governor to 
change the speed in synchronizing the generators, 
and a controlling device to open and close the electri- 
cally operated alternating-current generator field 
switch. 

The usual method of controlling feeder circuits is 
to place the controllers on the switchboard directly 
beneath their respective feeder instruments. 

Generator-Control Pedestals. — For aux- 
iliary controlled switchboard apparatus, mountings 
must always be provided for the control apparatus of 
each generator. The pedestal shown in the illustra- 
tion is designed for this purpose, and is used in com- 
bination with an instrument post or panel located 
immediately in front of it. 

The pedestal as shown in Fig. 32 is designed to 
take the following apparatus: 
Signal lamps. 

Six oil circuit-breaker indicating lamps. 
Three oil circuit-breaker controllers. 
One voltmeter plug and receptacle. 
Two synchronizing plugs and receptacles. 
One controller for engine governor motor. 
One controller for electrically operated field rheo- 
stat. 

One control switch for electrically operated field 
discharge switch. 

One control switch for engine signal. 
The controlling devices are not included but must 
be specified separately, and may be selected to suit the requirements of the 
installation. 




Fig. 32. Control- 
ling Pedestal. 



CONTROL DESK. 



941 



Controlling* Desks. — Wherever great concentration of controlling 
apparatus is necessary, a desk or bench-board is often used. This is usually 
built of marble or steel, and special conditions sometimes require special 
designs. 

This type of controlling desk as shown in Fig. 33, has an iron frame enclosed 
by paneled steel sides and a marble top. 

The construction is such that each top panel with its corresponding paneled 
sides forms a section, and the desk may be extended in either direction by 
installing additional sections, the end panels and end moulding being remov- 
able in one piece to provide for inserting the necessary additions. 

Instrument I*©sts. — The instrument posts used with desks or 
control pedestals are divided into two general classes, viz.: swivel type and 
stationary type. 




Fig. 33. Sectional Controlling Desk. 



These again may be designed with suitable bases to mount jacks, or recep- 
tacles, to enable one to calibrate or check up the meters, by comparison with 
standards whose terminals have plugs to fit the receptacles. 

A post supplied with receptacles for calibrating meters as described above 
is shown in Fig. 34. 

Calibrating- Jacks. — In many installations it is desirable to have 
jacks or receptacles provided in the series and shunt transformer circuits to 
enable standard meters with suitable plugs attached to be connected in 
these circuits for comparing the readings of the switchboard meters. 

There are two kinds of these receptacles used, one for establishing a loop 
in a series transformer circuit and used for an ammeter jack or an ammeter 
plug receptacle, the other being a double-pole receptacle or voltmeter jack 
for use on shunt transformer circuits. 



942 



SWITCHBOARDS. 



Field Rheostats and Field Switchboards. — If the gener- 
ator control apparatus is located on a panel, the field rheostat can be 
conveniently operated by means of a hand- 
wheel geared directly to a face plate on the 
rheostat by gearing or chain and sprocket. If 
the rheostats are electrically controlled from a 
distance through face plates, they should have 
a small motor geared to the contact arm, the 
motor being controlled from the operating 
platform and the field switches electrically 
operated. 

Direct- Current Exciter Switch- 
board. —The switchboard for control of the 
exciters is sometimes placed in the operating 
gallery when this is not too remote from the 
machines. In other cases it is placed on the 
station floor, as near as convenient to the 
exciters. It is usually a typical direct-current 
board, and, while the most serviceable ones 
have entire panels finished in black marine, a 
large number of stations are using blue Vermont 
marble. The circuit breakers used are non- 
automatic, being used only to trip by hand 
when the circuit is to be interrupted, to pre- 
vent the arc from burning the switch. Some 
station managers prefer reverse-current circuit 
breakers in the exciter circuits, but the usual 
practice is to omit protective devices. 

Station Apparatus. — In addition to 
providing for station voltmeters, synchroscopes 
and wattmeters, either on panels or on an 
instrument post, it is often necessary to install 
static ground detectors. These are always 
operated through condensers so located that 
the wiring is short and the conductors properly 
separated and far enough from neighboring 
metal so as not to interfere with the operation 
of the instruments. This is best accomplished 
by installing the ground detectors on the 
station wall or on suitable supports near the 
condensers if it is difficult to properly run the 
leads to the operating gallery. 

Sub-Station Switchboard Equip- 
ments. — Sub-stations are more commonly 
used for railway service. The usual equipment 
of switchboard apparatus for a sub-station is 
laid out on the same lines as for a generating station, but the arrangement 
and selection of the equipment is changed to agree with the requirements 
of the case. As lighting and power sub-stations are more or less special it 
is impossible to give a description which will be generally applicable. 

Railway sub-stations, however, fulfill practically the same purpose and 
in general differ only in number and capacity of the units. The conductors 
in such a station are usually very heavy and care should be taken to make 
the runs as short and direct as possible. 

A number of modifications may be made in the apparatus supplied. 
For instance, electrically operated direct-current apparatus may be used 
to save cable and permit of greater concentration, or for small stations the 
alternating-current switchboard may have hand-operated circuit breakers 
mounted directly on the panels. 

For single-phase alternating-current railway systems, the sub-stations 
are essentially transformer houses and are very simple. Figs. 35 and 36 
show a typical sub-station of this character. This apparatus for such a 
sub-station will vary with the requirements of service. 




nine 



Fig. 34. Post with 

instruments. The three 
ammeters at the bottom 
are for a bank of trans- 
formers. The six instru- 
ments above are for one 
generator. The plug 
switches in the base per- 
mit testing the calibra- 
tion of the instruments 
without removal. 



SUB-STATION SWITCHBOARD EQUIPMENTS. 



943 




v/mm a 



Fig. 35. Single-Phase Alternating-Current Sub-Station or Transformer 
House — End View. 



944 



SWITCHBOARDS. 




Fig. 36. Single-Phase Alternating-Current Sub-Station or Transformer 
House — Side View. 



SWITCHBOARD INSTRUMENTS AND METERS. 



945 



SWITCHBOARD I]¥STIlCnHCE]¥T AID METERS. 

The following is a list of the various instruments and meters used for 
switchboard work: 



Direct Current 



Alternating Current 

Indicating ammeter, 

Graphic ammeter, 

Indicating voltmeter, 

Graphic voltmeter, 

Single-phase indicating wattmeter, 

Single-phase integrating wattmeter, 

Single-phase graphic wattmeter, 

Polyphase indicating wattmeter, 

Polyphase integrating wattmeter. 

Polyphase graphic wattmeter. 

Graphic frequency meter, 

Graphic power factor meter, 

Differential voltmeter, 

Power factor indicator, 

Wattless component indicator, 

Frequency indicator, 

Synchroscope, 

Indicating compensating voltmeter, 

Electrostatic ground detector, 

Electrostatic voltmeter, 

Automatic synchronizer. 

Indicating ammeter, 
Graphic ammeter, 
Indicating voltmeter, 
Graphic drawing voltmeter. 
Integrating wattmeter, 
Graphic wattmeter. 

The names of the instruments in most cases describe their use. Inte- 
grating meters record by means of a dial the watthour output. Graphic 
meters record on a chart by a line the fluctuation of the voltage, cur- 
rent or watts of the circuit. Indicating wattmeters indicate the actual 
watts of the circuit which is equivalent to the volts as shown by the volt- 
meter multiplied by the current as shown by the ammeter multiplied by 
the power factor of the circuit, for single-phase circuits. 

Electrostatic Voltmeters are used only for high-potential circuits, 
such as 20,000 to 100,000 volts. They are connected directly to the cir- 
cuit without the interception of potential transformers and do not carry 
any current. Condensers are sometimes interposed. 

Alternating'- Car rent Instruments for high-tension circuits are 
not connected directly to the circuit, but are used in connection with cur- 
rent and potential transformers. Current transformers are connected in 
series with the main circuit, but are wound for different ratios of trans- 
formation so that approximately five amperes is obtained in the secondary, 
and therefore the instruments may all have five-ampere windings. The 
use of the current transformer makes it unnecessary to insulate the instru- 
ment for high voltages and furthermore does not necessitate running the 
high-tension leads to the switchboard. Ammeters are sometimes connected 
in series with circuits as high as 2500 volts. 

Potential transformers are usually wound to obtain from 100-125 volts 
on the secondary and are used on circuits of above 600 volts for voltmeters 
and other instruments having potential windings. 



946 SWITCHBOARDS. 



method of JTigruringr Instrument Scales. 

SINGLE-PHASE GENERATORS: 

Minimum ammeter scale 

_ K.W. X 1000 X (1 + per cent overload guarantee) 
voltage 
Wattmeter scale = ammeter scale obtained from above X voltage. 
THREE-PHASE GENERATORS: 
Minimum ammeter scale 

_ K.W. X 1000 X (1 4- per cent overload guarantee) 
voltage X 1 . 73 
Polyphase wattmeter scale = ammeter scale obtained from the above 
X voltage X 1.73. 
TWO-PHASE GENERATORS: 
Minimum ammeter scale 

K.W. X 1000 X (1 4- per cent overload guarantee) 
voltage X 2 
Polyphase wattmeter scale = ammeter scale obtained from the above 
X voltage X 2. 
DIRECT-CURRENT GENERATORS: 
Minimum ammeter scale 

_ K.W. X 1000 X (1 + per cent overload guarantee) 
voltage 
THREE-PHASE MOTORS: 
Minimum ammeter scale 

Horse-power X 746 • ( 

voltage X per cent Eff. X per cent P.F. X 1 . 73 X U + Per U ' ^' } ' 
TWO-PHASE MOTORS: 
Minimum ammeter scale 
Horse-power X 746 



X (1 +per cent O.G.). 



voltage X per cent Eff. X per cent P.F. X 2 

DIRECT-CURRENT MOTORS: 

ii/r- • i Horse-power X 746 w ,, , . _ _, . 

Minimum ammeter scale = — j- -^ ^ _ „ X (1 4- per cent O. G.) 

voltage X per cent Eft. 

THREE-PHASE ROTARY CONVERTER: 
Minimum ammeter scale 

= K.W. X 1000 v n -l *f\c'\ 

voltage X per cent Eff. X 1 . 73 X per cent P.F. X U + P ercent U ' «■'. 
Wattmeter scale = ammeter scale obtained from the above X voltage X 1 . 73. 

TWO-PHASE ROTARY CONVERTER: 
Minimum ammeter scale 

' K.W. X 1000 trim 

voltage X per cent Eff. X per cent P.F. X2 X1 +per Cent u -^ ) ' 
By per cent overload guarantee is meant the £, 1 or 2-hour overload guar" 
antee on the generator and not the momentary guarantee, although some 
prefer to have scales calibrated to read momentary fluctuations. 

The per cent efficiency and per cent power factor should be taken at full 
load or overload. 

The wattmeter scales should theoretically be multiplied by the power 
factor, but practically the scales work out better as given. Integrating watt- 
meters have no scales and therefore need only have sufficient current carrying 
capacity. 

When the minimum scale is determined from the formula the next larger 
standard scale, depending on the manufacture, should be selected. 
P.F. = Power Factor. 
O.G. = Overload Guarantee, 



GUIDE FOR SWITCHBOARD SPECIFICATIONS. 947 



4 BRIEF GUIDE FOR WRITING IUITCHBOARB 
SPECiriCAlIONi. 

The initial and ultimate number of each type of generator, motor and 
feeder circuit with their voltage, kilowatt and frequency rating should be 
given. The overload guarantees of the machines and duration of same 
should also be specified. Other characteristics of the machine, such as "Y" 
connected three-phase generators with grounded or ungrounded neutral, 
two-phase generators with inter-connected phases, direct-current generators 
with grounded or ungrounded negative, should be clearly stated. 

Plans of the building, or of that section of the building occupied by the 
switchboard should, if available, accompany the specifications. It is essen- 
tial to know the construction of the floor supporting the switchboard, and 
if there is a basement below the floor, when oil switches, rheostats and other 
similar devices are not to be mounted on the panels. 

Specifications should be specific as to just what the switchboard contract 
is to cover. Switchboards as furnished by the manufacturers usually do not 
include the following, which should, therefore, be furnished by the purchaser 
unless otherwise specified. 

Complete flooring, sills for supporting switchboard and other pieces set 
in the floor or wall for supporting cable racks, oil switch operating 
mechanism, etc. All false flooring, if any is required. 

All masonry work for oil switch cells and bus-bar compartments. 

All openings in walls or floors, with suitable bushings. 

All clay ducts, iron conduit and other similar material to be laid in the 
concrete floors. 

Doors for bus-bar compartments, lightning arrester or static discharge 
compartments. 

All cable between switchboard and machines and between switchboard 
and feeder circuits. 

All bus-bars not connected directly with the switchboard, such as equal- 
izer or negative bus-bars near the machines. 

If the purchaser desires to include any of the above material in the switch- 
board contract, such material should be clearly specified. 

A connection diagram showing the proposed main connections, providing 
they are unusual or complicated, should accompany the specifications. 

The height and width of the panels should preferably be left to the discre- 
tion of the manufacturer. The thickness of the panels depends on the size 
of the panel, the material of the panel and the devices mounted thereon. 

The design of the supporting framework need not be specified. In general, 
statements in specifications can be made as follows: 

1. "The material of the panels shall be such as to afford the proper insula- 
tion between live metal parts mounted directly on the panel, for the voltage 
on which they are used. It shall have a (natural oil), (black enameled) or 
(polished) finish, and the panels shall harmonize in color and markings and 
fit together in a neat and workmanlike manner. The panels shall be properly 
supported on iron framework. Connection bars, bus-bars and wires shall be 
properly supported and insulated." 

2. "All instruments shall be dead beat and protected from stray fields 
produced by adjacent connections or bus-bars." 

3. "Circuit breakers shall be of sufficient capacity to carry the overload 
ampere capacity of the generator or motor, without overheating. They 
shall be capable of opening under short circuited conditions without dan- 
gerously burning the contacts and shall be of such a design as to be positive 
in action." 

4. "Oil switches shall have a kilowatt rupturing capacity based on the 
ultimate installation of generators as heretofore stated in these specifications. 
The switches shall withstand for one minute a potential test between con- 
tacts and frame, of at least twice the rated voltage of the circuit." 

5. "All switches shall be of such capacities as to carry the one or two 
hours overload rating of the circuits to which they are connected without 
undue temperature rise, and shall be properly designed for the service for 
which thej' are intended and without defects of workmanship." 



948 SWITCHBOARDS. 



6. "Connection bars and wires shall be of sufficient cross section so that 
with maximum load the temperature rise at no point will exceed 40° C. rise 
above the surrounding air, which may be based on 20° C. Bus-bars shall 
be of sufficient cross section to carry continuously the total normal load of 
all the generators feeding in parallel through the busses at various points. 

The design of the busses shall, as far as possible, permit additions and 
extensions without materially interfering with the operation at a later date, 
or changing the existing supports. 

"Insulated main connection wires or cables should have flame-proof 
covering, and the insulation should not be wholly relied upon but should be 
supported by suitable insulators." 

It is not advisable to specify the contact area, cross section or rating of 
switches, circuit breakers or connection bars, as this often necessitates special 
devices, whereas standard devices could have been used if only the temper- 
ature guarantees were given. 

If purchaser has determined as to what instruments and switches are 
necessary, a complete list, giving the equipment of each panel, should be 
ncluded. Otherwise this equipment should be specified in detail in the 
manufacturers' proposal and inserted in the specifications forming part of 
contract. 

SWITCHING DEVICES. 

Switching devices in connection with switchboards can be divided gen- 
erally into the following-named classes, viz.: 

Switches for low voltage and small current are of the same general form, 
though differing in details. In the main they consist of a blade of copper, 
hinged at one end between two parallel clips, the other end of blade sliding 
into and out of two parallel clips. The clips are joined to copper or brass 
blocks to which the circuit is connected. 

There seems to be little uniformity among manufacturers regarding the 
cross section of metal and surface of contact to be used. Perhaps a cross 
section of metal of one square inch per 1000 amperes of current capacity is 
as near to the common practice as any, and a contact surface for bolted con- 
tacts of at least one inch per 100 amperes or ten times the cross section of 
metal is also common practice, but will depend somewhat on the pressure 
between surfaces. For sliding contacts the density per square inch should 
not exceed 75 amperes. 

Auxiliary breaks are demanded by the National Code for currents ex- 
ceeding 100 amperes at 300 volts, and "quick-break" switches are now 
quite common for pressure as low as 110 volts. 

The rules on switch design issued by the National Code cover the require- 
ments well, and they must be followed in order to obtain or retain low 
insurance rates; all switches must meet the requirements. 

Blades, jaws, and contacts should be so constructed as to give an even 
and uniform pressure all over the surface, and no part of the surfaces in 
contact should cut, grind, or bind when the blade is moved. The workman- 
ship should be such that the blade can be moved with a perfectly uniform 
motion and pressure, and the clips and jaws should be retained so perfectly 
in line that the blades will enter without the slightest stoppage. 

Sparking; at Switches. — In a paper read before the British Institu- 
tion of Electrical Engineers, A. Russell and C. Paterson discuss the subject 
of sparking at switches. In the diagram are given lengths of sparks at 
various constant voltages. Following are the conclusions arrived at: (1) 
The spark at break ought to be taken as a guide to the rating of a switch 
for use on direct-current circuits. (2) The shape of the terminals does not 
make much difference in the length of the spark. (3) The effect of increas- 
ing the speed of break above that ordinarily employed is small. (4) The 
effect of a double break is to make the lengths of the spark the same as the 
length of a spark with the same current at half the voltage. (5) The dif- 
ference in the length of the spark when copper, steel, or zinc is used is not 
great. (6) For small double-break switches for use on circuits of 200 volts 
and upwards, when the trailing spark just fails to bridge the air-gap, the air- 
gap should be double the distance at which a permanent arc can bejobtained. 
(7) For double-break switches for large currents under the same circum- 
stances the air-gap should be more than double the arcing distance. 



SWITCHING DEVICES. 



949 











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Ampere*. 
SPARKING AT SWITCHES* 

Fig. 37. 



Switching devices used in connection with switchboards can be divided 
into several classes as follows, viz.: 

Circuit breakers, automatic. 

Relays. 

Lever switches (knife switches). 

Quick-break switches. 

Plug switches. 

Disconnecting switches. 

Controlling switches. 

Oil-break switches (oil circuit breakers). 

Fuses. 



Circuit Breakers. 

A circuit breaker is a device which automatically opens the circuit in event 
of abnormal electrical conditions in the circuit. Automatic circuit breakers 
are designed for alternating and direct-current circuits. Alternating-current 
circuit breakers are usually made to operate on overload or low voltage. 
The usual conditions under which circuit breakers operate are: 

Overload. 

Underload. 

Reverse current. 

Overvoltage. 

Undervoltage. 

Electrically tripped from a distance (shunt trip). 



950 



SWITCH HOARDS. 



If no conditions are specified it is always understood that the overload 
circuit breaker is desired, as reverse current, low-voltage features, etc., are 
usually in the form of attachments to the standard overload circuit breaker. 

The Overload Circuit Breaker is used to protect the system 
against excessive overloads. The overload feature consists of a coil con- 
nected in series with the main circuit, which operates the circuit breaker 
tripping trigger by means of its armature. 

Since this power is obtained from a solenoid connected in series with the 
circuit breaker it is obvious that the number of turns of wire or bar on the 
magnet depends on the ampere capacity of the circuit breaker. Circuit 
breakers of 800 amperes and above may be designed so as to require but 
one turn which is obtained by encircling one of the studs of the circuit 
breaker with an iron horseshoe to which is pivoted the armature. In order 
to provide for a wide variation in capacities without introducing too many 
sizes, each circuit breaker is designed to cover a large range of current, 
between the limits of which it may be set to trip at practically any point. 
The limits of calibration usually range from 50 to 150 per cent of the con- 
tinuous current carrying capacity. 

The "Underload Circuit Breaker is similar to that for overloads, 
except that it acts in event of an underload instead of an overload. This 




Fig. 38. Type " C," Form " K2," 2000-Ampere, 650- Volt, Automatic Circuit 
Breaker, as manufactured by the General Electric Company. 

type of breaker is applied to storage battery circuits to cut off the battery 
when the current falls to an amount which would indicate that the battery 
was fully charged. It may also act as a reverse current circuit breaker, 
because during the reversal the current must fall to zero value. The under- 
load breaker also acts as a low-voltage breaker, inasmuch as if the source of 
power is cut off the flow of current will cease. However, it is not always 
desirable to use an underload breaker for such purposes as it would operate 
in many cases on small loads when not intended to. 

The Direct Current Reverse Current Circuit Breaker is 
essentially an overload breaker, having a potential winding operating 
magnetically in conjunction with the overload feature so that, the circuit 
breaker will open in event of a reversal of the direction of the flow of current. 
Under some conditions the circuit breaker would be required to operate on 
an overload and a reversal of current. In other cases it may be required to 
operate only on a reversal of current. Both kinds of circuit breakers are 
manufactured, but the most reliable method is to apply a reverse current 



SWITCHING DEVICES. 



951 



relay as described on page 961 to a standard overload breaker, having a shunt 
trip or low- voltage attachment. In this case the overload feature may be 
adjusted independently of the reverse-current attachment, or may be blocked 
to make it inoperative. 

The principal uses of the reverse-current circuit breaker are briefly de- 
scribed under the subject relays on page 961. 

The low-voltage feature is usually an attachment to a standard overload 
breaker, and is used chiefly on motor circuits to cut off a motor from the 
source of power in event of an interruption of current, in order that the 
motor may be properly started by the attendant, with the aid of a starting 




Fig. 39. Westinghouse Type C Circuit Breaker Showing Adjusting 
Mechanism and Terminals for Rear Connections. 

rheostat or compensator, when the source of power is restored. The low- 
voltage coil may also "be advantageously used to trip the circuit breaker from 
a remote place by shunting the coil. Low voltage breakers are operated 
by opening the circuit of the coil. Shunting the coil short circuits the line. 
The Application of Reverse Current Circuit Breakers to 
the Protection of Transmission Line in Multiple. — Where 
power is delivered to a single receiving point by more than one system of 
feeders, it will be seen that in the absence of suitable protective devices prop- 
erly disposed, a short-circuit upon one set of feeders will be fed not only 
through the portion of the feeder located between the short-circuit and the 
source of supply, but also by means of the portion of the damaged feeder 
beyond the short-circuit, with current flowing in the reverse sense from the 
receiving station. " Overload " circuit breakers at both generating and receiv- 
ing ends of the cables form a means of isolating the damaged lines. Their use 
alone, however, is liable to cause momentary interruption of service in the 
uninjured cables, which will be repeated until the damaged line is finally 
located and put out of service. Circuit breakers heaving reverse current 
operation located at the receiving end of the transmission lines will automat- 
ically sever the damaged cables at this end and prevent the receiving station 
from feeding back into the short-circuit; this being attained without inter- 
ruption of the service. In case of a receiving station having a number 
of feeders of approximately the same capacity, ordinary overload circuit 
breakers will generally afford ample protection because a short-circuit on 
one feeder will be fed through its own circuit breaker from all the other 
receiving station circuit breakers in parallel. This will tend to open the 
breaker on the short-circuited feeder line first, and relieve the system. If 
the station has only two incoming feeders, however, this condition obviously 
does not obtain and reverse circuit breakers are very essential. 



952 SWITCHBOARDS. 



The Application of Circuit Breakers to the Protection of 
Storagre Battery Boosters. — Boosters of the compound or series type, 
if left connected with the system when the circuit of the driving motor is inter- 
rupted, will act as series motors rotating in the reverse direction, and, if not 
promptly disconnected, will attain a destructive" speed. Similar conditions 
occur should the booster circuit be closed before the motor has been started, 
or should the motor for any reason lose its field. Proper protection under 
these conditions is secured only by having an overload and no voltage circuit 
breaker in the motor circuit inter-connected with the circuit breaker in the 
battery circuit in such a manner that the motor circuit breaker must be closed, 
before the booster circuit breaker can be made to latch, while the opening 
of the first-named instrument instantly causes the opening of the second. 

The Application of Circuit Breakers to the Protection of 
Boosters Supplying" feeders. — Boosters employed to compensate 
voltage losses in feeders, incident upon transmission over considerable dis- 
tances, are either series or compound wound; if, therefore, when for any rea- 
son the driving motor is not receiving current, the booster should be left in 
connection with the system, it will run reversely as a motor, and in view 
of its series field-winding will attain destructive speed. This condition 
may be adequately dealt with by the employment of circuit breakers similar 
to those prescribed for the previous section. 

The low- voltage trip coil consists of a shunt winding connected across the 
circuit in series with a resistance, or may be connected in series with the 
shunt field of a motor if used on direct current. So long as the voltage 
remains constant the coil holds up a plunger, but if the voltage drops below a 
certain limit the plunger is released and the force of the blow trips the breaker. 

The shunt trip coil is normally open-circuited, and when energized, by 
means of a controlling switch or auxiliary switch or such device, it actuates 
the circuit breaker. 

CIHCriT BREAKER BESIGJi T. — Birect-Current Cir- 
cuit Breakers are made single, double and triple pole and four pole. 
The double-pole circuit breakers usually have the overload feature on one 
pole only, which is sufficient protection, except in case of the three-wire 
systems where a triple-pole breaker having two or three coils should be 
provided. Some types of double-pole breakers have a coil to a pole. 

Alternating-Current Circuit Breakers are made single, double, 
triple and four pole. The single-pole circuit breaker has one coil ; the double- 
pole circuit breaker has one coil; the triple-pole circuit breaker may have but 
one coil if used on a motor circuit, as there is practically no chance of a short 
circuit between but two of the leads, otherwise it should have two coils, and 
in cases where the three-phase system has a grounded neutral it should have 
three coils; the four-pole circuit breaker should have two coils, unless the 
phases of a two-phase system are interconnected, in which case it should have 
three coils. 

The carbon-break circuit breaker has been generally adopted for station 
work on account of the fact that it requires minimum attention, and will 
operate many times on short circuits without requiring cleaning or repair of 
the contacts. 

The sequence of operation of the various contacts of the carbon-break 
circuit breaker, is as follows: First, the main contact opens, which shunts 
the current through the intermediate and carbon contacts, then the inter- 
mediate contacts separate; this leaves the circuit through the carbon con- 
tacts, where the circuit is finally broken. The object of the intermediate 
contact is to prevent an arc forming on the main contact. 

Where it is desired to definitely direct the arc from the circuit breaker, 
or the amount of space for the arc is limited, such as would be the case in 
oar work, magnetic blowout breakers are preferable. 

Circuit breakers of the carbon break type which are in most common use, 
are preferably mounted at the top of the switchboard panels, as the arc 
formed in opening is invariably blown violently upward, and is liable to 
damage any apparatus mounted directly above it, or blacken and burn the 
panel. This tendency is not pronounced on small capacity circuit breakers 
on circuits of 250 volts or less, and this precaution is unnecessary. 

CIRCUIT BREAKERS.— For Alternating-Current Ser- 
vice. — The class of circuit breakers required for polyphase circuits largely 
depends upon individual conditions; the few cases considered here will suffice 
to indicate the principles which should influence the selection. 



CIRCUIT BREAKERS. 



953 



In the consideration of polyphase systems, it must not be forgotten that 
a large proportion of the generators and motors are made with interlinked 
windings, and for this reason circuit breakers for the protection of two-phase, 
four-wire generators and circuits should, regardless of voltage, provide for 
the severance of all four leads, as a single break in each phase still leaves 
the two remaining leads subject to a potential difference of not less than 
seven tenths of the voltage in either phase. 

This point is made clear by reference to the accompanying cut A, which 
shows two pieces of two-phase apparatus, as, for instance, generator and 
motor connected to the same circuit. On account of the windings being 
interlinked, it will be seen that the passage of current from one to the other 
is still possible, unless at least three of the four wires are severed.- 

Where, as is frequently the case, the entire output of the two-phase 
generator is supplied to single-phase transformers having independent 
primary windings, then it is true that in the absence of grounds or crosses 







B C 

Circuits Connecting Polyphase Apparatus. 

the generator will be fully relieved of its load by the opening of both phases, 
each at one point only. Preference to cut B shows, however, that the possi- 
bility of grounds or crosses is a contingency which in this case needs to be 
carefully reckoned with, as in the event of either of these conditions involving 
both of the unsevered mains, the opening of the circuit at one point in each 
phase does not relieve the generator. 

Circuits Connecting- JPol jphase Apparatus. — In the event of 
a short circuit on the mains supplying a synchronous motor this piece of 
apparatus, kept in motion by its own momentum, acts for the time being 
as a generator, thus, much increasing the severity of the short circuit. 
Again upon the opening of the circuit breaker the coincident slowing down 
of the motor results in its E.M.F. dropping out of phase with that of the 
generator, thereby very greatly increasing the total electromotive force of 
the circuit and producing abnormal strains upon opening devices and insu- 
lation. . . 

Therefore, the circuit breaker chosen should be such that when it is open, 
not more than one main of the circuit shall remain in connection with the 
source of the supply. Motors operating on three-wire circuits of moderate 
voltage may be adequately protected by double-pole circuit breakers. Those 



954 



SWITCHBOARDS. 



on four-wire systems fed from transformers whose secondaries are not in 
electrical connection may also be protected in the same manner. Four-wire 
transmission circuits require circuit breakers of not less than three poles, 
etc., but preferably the circuit breakers chosen for the protection of poly- 
phase generators and feeders should be capable of severing every main of 
the circuit, thus securing complete interruption of the current regardless of 
possible grounds and crosses. The higher the voltage of the circuit the more 
important this consideration becomes. 

The protection of polyphase motors is a subject deserving of special con- 
sideration. The staunch build of this class of apparatus and its known 
ability to withstand heavy overloads often lead to its being carelessly started 



Co/t.r£cT/o/r$ or Auto -^TAffTtff Art? CftCo/r QnEAXtn 
ffenot/t/fiG Circuit 3/tfAkt/t OP£#ATive 0/tj.r. 
DuRtriG, FturtritrtG ConPrtton* 




Fig. 40. 

and otherwise unduly abused. While this may not result in immediate 
injury to the motor, it causes excessive disturbances in the voltage of the 
circuit, and undue waste of energy. 

The heavy starting current required by many types of polyphase motors 
has in the past constituted a serious objection to the use of overload circuit 
breakers for their protection. This difficulty is overcome by making the 
connections between the auto-starter and circuit breaker such that the latter 
will be included in the circuit of the motor only when the switch of the auto- 
starter is in the running position. Reference to Fig. 40 shows how this may 
be effected. When the circuit breaker is connected in the manner there 
shown it will not be acted upon by the currents passing in the starting posi- 
tion of the switch, but should the switch be thrown into the running position 
at once or before the motor has come up to speed, the circuit breaker will 
open upon the resulting overload, as will also be the case should the motor 
be unduly loaded. 

Perhaps the most potent source of damage to polyphase motors is the 
accidental severance of but one phase of the circuit, due in most cases to 
the blowing of a fuse, either at the motor or somewhere in the circuit supply- 
ing it. Where this occurs when the motor is running the latter will, unless 
very lightly loaded, come to a standstill, and if not promptly disconnected 
will be seriously injured. 



CIKCUIT BREAKERS AND RELAYS. 



955 



Capacity of Circuit Breaker Required for B.C. 

Generators. 

The size of a circuit breaker is ordinarily determined by its normal current 
carrying capacity, and for any generator the capacity of the circuit breaker 
should be the same as the normal rated capacity of the generator, and the 
breaker should be calibrated for such a range of overload as is required by 
the service conditions. 



Capacity of Circuit Breaker Best Adapted for Motor 
of ©riven Size. 

The Cutter Company. 

The following table indicates the sizes of circuit breakers best adapted 
for the protection of various sizes of motors of from \ horse-power to 100 
horse-power at voltages of 125, 250, or 500. 

The figures given in the left hand column indicate the horse-power of the 
motor at full load; the remaining columns show the normal capacity of the 
circuit breakers required for each of the voltages given. 



Horse-Power 
of Motor at 
Rated Load. 


For 125 Volts Nor- 
mal Capacity of Cir- 
cuit Breaker. 


For 250 Volts 

Normal Capacity 

of Circuit 

Breaker. 


For 500 Volts 

Normal Capacity 

of Circuit 

Breaker. 


\ 


4 amperes 






1 


8 amperes 


4 amperes 




2 


16 or 20 amperes 


4 amperes 


4 amperes 


3 


24 or 30 amperes 


12 amperes 


8 amperes 


5 


45 amperes 


20 amperes 


10 amperes 


n 


60 amperes 


30 amperes 


20 amperes 


10 


80 amperes 


40 amperes 


20 amperes 


15 


150 amperes 


60 amperes 


30 amperes 


20 


200 amperes 


80 amperes 


45 amperes 


25 


200 amperes 


100 amperes 


60 amperes 


30 


300 amperes 


150 amperes 


60 amperes 


40 


300 amperes 


150 amperes 


80 amperes 


50 
75 


400 amperes 
600 amperes 


200 amperes 
300 amperes 


100 amperes 
150 amperes 


100 


800 amperes 


400 amperes 


200 amperes 



BELAYI, 

Definition. — A relay is a device which opens or closes a local circuit 
under pre-determined electrical conditions in the main circuit. 

Classification. — There are three general classes of relays as follows: 

1. Signalling. 

2. Regulating. 

3. Protective. 



Signalling- Relays. 

Function. — The signalling relay acts to transmit signals from a main 
to a secondary circuit. 

Application. — They are mainly used in telegraph and telephone 
work, being known by the terms telegraph or telephone relays, and ao not 
need further description here. 



956 SWITCHBOARDS. 



Regulating 1 Relays. 

Function. — The regulating relay acts to control the condition of a 
main circuit through control devices actuated by a secondary circuit. This 
control may involve the maintenance of either the voltage, current, fre- 
quency or power factor of a circuit at a constant value. 

Application. — The regulating relay finds application in generator 
and feeder circuit regulators, such as the Tirrill Regulator, etc., in which it 
forms the main device, all other apparatus being subsidiary and actuated 
thereby. 

It differs from the usual protective relay in having its contacts differ- 
entially arranged, that is, so that contact is made on a movement of the 
relay to either side of a central or normal position. 

The regulating relay is usually considered a component part of its par- 
ticular regulator and for this reason it will not be further considered here. 

Protective Relays. 

Function, — Distributing systems requiring more selective and flexible 
protection than that afforded by the inherent control features of automatic 
circuit breakers are equipped with protective relays. 

Protective Relays. — Protective relays are used entirely for the 
protection of circuits from abnormal and dangerous conditions such as over- 
loads, short circuits, reversal of current, etc. They act in conjunction with 
automatic circuit breakers, operating when their predetermined setting has 
been reached, energizing the trip coils of the breakers and opening the circuit. 

Auxiliary Relays. — Sometimes a main relay, due to inherent 
limitations, is not able to fulfill all of the necessary requirements. An 
"auxiliary" relay is then used in conjunction with the "main" relay and 
supplies the missing functions. Such missing functions may be for example: 

1. Lack of time element feature in the main relay. 

2. Insufficient carrying capacity of the main relay contacts. 
Classification. — Protective relays are sub-divided according to their 

particular function into the following classes: 

Over-voltage, overload, overload and reverse current, reverse current, 
underload, low-voltage and reverse phase. These designations indicate 
the circuit conditions under which the various classes operate. For example, 
the over- voltage relay operates when the voltage rises above a predetermined 
amount; the reverse current relay operates upon reversal of current, etc. 

Time Element JPeature. — Continuity of service is an essential 
consideration in all installations, and interruption of the service cannot be 
tolerated unless the protection of the apparatus demands it. There are, 
however, certain abnormal conditions of current flow which may exist for 
a short time on a circuit without causing serious damage, such as swinging 
grounds, intermittent short circuits, synchronizing cross currents, etc. The 
simple instantaneous relay would in such cases act instantly and interrupt 
the service unnecessarily. There has, therefore, arisen the necessity for 
relays having a retarded or time element action. 

Refinite Time JLimit Relay. — For certain service it is sufficient 
that this retarded action have a definite predetermined value independent of 
the load condition. Such a relay is termed a "definite time" limit relay. 

Inverse Time JLimit Relay. — For other service it is necessary 
that this time element vary inversely with the load, that is, with greater 
load the time element should be less, and vice versa. Such a relay is termed 
an "inverse time" limit relay. 

Application of the Instantaneous Relay. — Instantaneous 
relays are used where it is desired to give protection only at the limiting 
carrying capacity of the apparatus. 

Application of Refinite Time .Limit Relay. — Definite time 
limit relays are used where it is necessary to maintain service on a given 
circuit at all hazards for a predetermined time. This allows temporary 
grounds and short circuits to clear by burning themselves out, and prevents 
synchronizing cross currents from opening the breakers. Most desirable of 
all, however, it enables instantaneous and inverse time-element relays on 



CIRCUIT BREAKERS. 



957 



contiguous circuits of less importance to operate and cut off under dis- 
turbances without opening the important circuit, even though the latter is 
temporarily heavily overloaded during the disturbance. 

Characteristics of the Inverse Time Element Relay. — 

— Inverse time element relays possess two valuable characteristics as 
follows: 

1. Their operation is inversely proportional to the strain on the system ; 
the greater the strain, the quicker the relay will operate. 

2. By virtue of 1, they act "selectively," those nearer a point of dis- 
turbance in a system, and which, therefore, receive the greatest load, oper- 
ating first, cutting out the affected portion and clearing the system while 
confining the disturbance to a minimum area. As an example, consider a 
system of three feeders (1, 2, and 3, Fig. 41) connecting a set of power station 
bus-bars, A, with a set of sub-station bus-bars B, and protected with auto- 
matic circuit breakers controlled by overload inverse time element relays 
at D, E, F, and reverse current inverse time element relays at P, Q, R. The 
overload relays will each be adjusted for operation at the same current; like- 
wise the reverse current relays will each be adjusted for operation at the 
same current. 

Assume now that a short circuit develops in 1 at point X. All three 
feeders will at once commence to supply current to the short circuit from A . 

A 8 






1 


X 


P 


E 


Z 




Q 










r 

w _ 


3 




K 











Fig. 41. Illustration of Selective Action of Inverse Time Element Relay. 



If B is a rotary converter sub-station, the rotaries, by virtue of their enormous 
fly wheel effect, may tend to supply current also, but as this has no par- 
ticular bearing on the point to be brought out it will not be further consid- 
ered. D being nearest the fault X, and therefore in the circuit of least line 
drop, will receive more current than E and F. By virtue of the inverse 
time law it therefore operates first or "selectively," cutting off the feeder 1, 
from A before E and F have time to act. Simultaneously P has been receiv- 
ing current in the reverse direction through bus-bars B, from feeders 2 and 3, 
and has cut off feeder 1 from B. Q and R will not operate as they receive 
current only in the normal direction, and E and F will not operate as the 
fault has been isolated and they have been relieved of their overload before 
they have had time to act. In actual practice on alternating-current circuit 
relays P, Q, R will operate on both overload and reversal of current, and 
are so designed that the operation on reversal of current is at a much lower 
value than on overload (about ^ to £ in representative types). If overload 
and reverse current relays were used at P, Q, R, the relay at P would operate 
before Q and R, for the reverse fault current flowing through P is the sum of 
the normal fault currents through Q and R. 

Where only two feeders exist as, say 1 and 2, P and Q would each receive 
the same amount of fault current, and the selective action is not so great, 
but is still amply sufficient to allow P to operate before Q, on account of the 
difference between their reverse and overload tripping values. 



958 SWITCHBOARDS. 

Similarly to the definite time element relay, the inverse time element relay 
will allow temporary grounds or short circuits to clear themselves and will 
prevent synchronizing cross currents from opening breakers. This action 
is somewhat more limited in the latter on account of the inverse feature, 
but is quite sufficient for all ordinary conditions. 

Jleclia ni am of the ^Protective He lav. — Protective relays in 
their simplest form consist of three elements: 

1. The actuating mechanism energized by the line source to be pro- 

tected. 

2. A set of contacts operated thereby. 

3. The time element feature (where present). 

Actuating* Mechanism. — The actuating mechanism assumes the 
form which will give operation under the desired conditions. It usually 
involves a motive device consisting of a solenoid and core, a rotating motor 
or some form of instrument movement. 

Tripping* Mechanism. — This usually consists of a set of moving 
platinum, silver or carbon-tipped contacts engaging a corresponding set of 
stationary contacts. Some relays have single contacts for closing a single 
tripping circuit; others are provided with multiple contacts for closing two 
or more tripping circuits, as in the operation of double throw systems where 
a relay in the main circuit has to operate circuit breakers in each of the 
duplicate feeder bus-bars. 

Time Element Mechanism. — In this instantaneous relay all 
retarding mechanism is eliminated, the relay acting practically instantane- 
ously with the application of an excessive current. In the definite time limit 
relay it is the usual practice to employ an air dashpot, such as used in arc 
lamps, to the piston of which the contact mechanism is attached. Upon 
the operation of the actuating mechanism the contact mechanism is released 
and allowed to descend by gravity against the action of the dashpot, thereby 
making contact a definite interval of time after the disturbance and inde- 
pendent of the magnitude of the disturbance. 

In the inverse time limit relay the actuating and contact mechanism is 
attached directly to an air bellows and upon operating tends to compress 
the bellows against the action of a specially constructed escape valve in the 
latter. 

The amount of the retardation varies inversely with the pressure on the 
bellows and, therefore, inversely with the magnitude of the disturbance. 
An alternative arrangement replaces the bellows with a conducting disk 
cutting a magnetic field, in which the retardation due to the eddy current 
reaction, induced on moving the disk through the field, varies inversely with 
the magnitude of the force with which the disk is urged through the field 
and hence inversely with the disturbance. 

Shunt Trip Contacts. — The usual arrangement of relay contacts 
provides for their closure upon the operation of the relay, in which case the 
relay is spoken of as being provided with "shunt trip contacts." The con- 
tacts are connected in series with the tripping circuit of the breaker and 
an independent source of current, and upon closing energize the tripping 
circuit and open the breaker. 

The tripping coils are wound for shunt operation from the independent 
source which is usually a direct-current exciter circuit or a storage battery, 
and the circuit breaker is spoken of as being equipped with shunt trip coils. 

The operation of shunt tripping coils from the circuit being protected is 
inadvisable, owing to the liability of the trip coil failing to operate on the 
low voltage existing under short circuit and overload conditions. 

Series Trip Contacts. — Where an independent source of current 
is not available the circuit breakers are provided with series tripping coils, 
wound for operation from series transformers in the main circuit. Overload 
relays are also provided with series trip contacts which differ from the shunt 
trip contacts in being normally closed instead of open, and opening upon 
operation of the relay. They are connected in shunt with the series trip 
coils short circuiting the same. Upon operation of the relay they open, 
allowing the transformer secondary current to flow through the trip coils 
and trip the breaker. As there is always sufficient current flowing under 
overload and short circuit conditions to operate the trip coils, this arrange- 
ment is as satisfactory as shunt tripping. 



CIRCUIT BREAKERS. 



959 



Protection of Alternatingr-Current Systems. — The applica- 
tion of relays to any given system depends almost entirely upon the local 
conditions of operation, varying somewhat with each installation. 

Generator Circuit Protection. — Representative practice rec- 
ommends the placing on generator circuits of either a reverse current 
relay, with a time element feature, or else the entire elimination of automatic 
protection. 

feeder Circuit Protection. — For feeders at the power station 
end, overload inverse time element relays are desirable. For feeders at the 
sub-station end, overload and reverse current inverse time element relays 
are desirable. 

Botary Converter Circuit Protection. — With rotary convert- 
ers, an overload inverse time limit relay in the high tension side of the 
power transformers will give protection for the alternating-current side. 
For the direct current side a reverse current inverse time limit relay operating 
the direct current breakers will be required. 

Protecting* JF our- Wire Three-Phase System. — An example 
of the relaying required in a typical four-wire three-phase system is illus- 



Automatlc Oil Circuit Breaker 

with relays. \ \ Power 
Bus// \ Bus * Tr s ans Pis. 



3 Phase 
Generator 



7/ 



Generator \ -H- 
Neutral , % 



-*& 



us\ 



SW9. 



A.C. 

Distribution 



fea 




* l\ cQ^^ 



Hf-^O^ 



Distri. 
bution 



* if o f 

Botary -Con verier # 
Catbort breaker with relaj; 
Fig. 42. Relaying of a Four- Wire Three-Phase System. 

trated in Fig. 42. Three generators operating with their neutral points 
grounded through a resistance, feed a common bus system, four sets of 
feeders, power transformers, rotaries, etc., for alternating-current and direct- 
current distribution of power. Automatic circuit breakers are inserted 
operated by relays as follows: 

At A, A.C. = Overload and reverse current inverse time element relays. 

At B, A.C. = Overload inverse time element relays. 

At C, A.C. = Overload and reverse current inverse time element relays 

At D, A.C. = Overload inverse time element relays. 

At E, D.C. = Reverse current inverse time element relays. 

The relays at A are intended for reverse protection only and so have their 
overload adjustment set at the maximum value. 



960 



SWITCHBOARDS. 



Relays Commonly Employed. 

most commonly employed are: 



The types of protective relays 



D.C. Over-voltage relays. 

D.C. Reverse current relays. 

D.C. Low- voltage relays. 

D.C. Underload relays. 

A.C. Overload relays. 

A.C. Overload and reverse current relays. 

A.C. Low-voltage relays. 

A.C. Reverse phase relays. 




Fig. 43. 



Westinghouse Direct-Current Time Limit Relay Definite Time 
Limit Action Shunt Trip Contacts. 



Application. 

Direct-Current' Over- Voltagre Relay. — The direct-current over- 
voltage relay is used chiefly on battery charging panels, but is also used 
to protect any direct-current apparatus which would be liable to dam- 
age from excess voltage. In storage battery work the relay may be used 
to disconnect the battery from the circuit when it is fully charged, as under 
certain well-defined conditions the voltage of the battery is a measure of 
its charge. The voltage of a battery is dependent, however, not only on 
its inherent characteristics, but also upon its charge and discharge history. 
Abnormal charging and discharging conditions operate to temporarily or 



BELAYS. 



961 



permanently change the law of a battery's voltage curve, and an over- voltage 
relay set for a given full charge condition may actually operate when the 
battery is not at full charge. The proper setting of a relay on such a circuit 
is, therefore, a matter entirely to be determined by the operating conditions 
and with full consideration being given to the effect upon the full charge 
voltage of the charge and discharge factors. 

Direct- Current Reverse Current Relay. — The direct-current 
reverse current relay is chiefly used for the protection of storage battery 
installations and rotary converters. When applied to rotary converters 
operating in parallel the relay serves to protect against short circuits occur- 
ring on the alternating-current side of the rotary, on the direct-current side 
between the rotary and relay, or in the rotary itself. 





Fig. 44. General Electric Alternating- Fig. 45. General Electric Alternating* 
Current Overload Relay Instantan- Current Overload Relay Instantan- 
eous Action Shunt Trip Contacts. eous Action Series Trip Contacts. - 

Short circuits occurring on the direct-current side beyond the relay are 
taken care of by the circuit breaker overload coils. When applied* to 
storage battery installations the relay prevents the battery from discharg- 
ing back into its charging source. 

Time Element feature. — When synchronizing machines to a 
system operating a rotary converter, momentary and harmless corrective 
currents are liable to flow toward the rotary on the direct-current side. In 
order to prevent interruption of the circuit by such flow, where reverse 
current relays are present, it is necessary that the latter have a time element. 
This time element must be of the inverse order to give quick interruption 
on overloads and short circuits and to give a selective action so as to cut off 
affected circuits. 

Overspeeding- of notaries. — Reverse current relays are not a 
complete protection against the overspeeding and running away of rotary 
converters such as would result from the opening of the rotary 's field. They 
should be supplemented by mechanical overspeed devices attached directly 
to the shaft of the rotary and arranged to close the trip circuit upon opera- 
tion. Such additional precaution is necessary as very low reverse currents 
exist under such conditions, only sufficient to supply the losses in the rotary 
and less than the minimum setting of the ordinary reverse current relay, 
which will therefore fail to operate and protect the machine. 

Direct-Current Xow-Voltagre Relay. — This relay is generally 
used in connection with direct-current motors and operates when the vol- 
tage of the circuit falls below a predetermined value. 



962 



SWITCHBOARDS. 



Direct-Current TTnderload Relay. — This relay is mainly used 
in the charging of storage batteries to disconnect the batteries when charged. 

Alternatingr-Current Overload Relay. — This relay is used 
very extensively, mainly for the protection of feeders, rotary converters, 
motors and transformers. All three forms exist, viz.: the instantaneous, 
definite time limit and inverse time limit, each finding its special application 
as outlined in the preceding pages. Either series or shunt trip contacts are 
provided depending on the tripping source. 

Alternating--! lurrent Overload and Reverse-Current Re- 
lay* — This relay is an important one, very extensively used for generator 
and feeder protection. It exists only in the inverse time limit form. When 
used for generator protection the overload adjustment is set at the maxi- 
mum value to give overload protection only at the maximum carrying 





Fig. 46. Westinghouse Direct- 
Current Over- Voltage Relay In- 
stantaneous Action Shunt Trip 
Contacts. 



hotts^^t 



Fig. 47. Westinghouse Alternating- 
Current Overload Relay (Cover Re- 
moved) Inverse Time Limit Action 
Shunt Trip Contacts. 



capacity of the generator and a sensitive reverse protection to prevent 
a return of energy from the line. 

The selective action of this relay has been covered in the preceding pages. 

Alternatingr-Current I^ow- Voltage Relay. — This type of relay 
is used for the protection of induction motors against a fall in the line 
voltage. 

Alternatingr-Current Reverse-Phase Relay. — This relay is 
used to protect synchronous apparatus against a reversal of direction of 
rotation or phase progression of the alternating-current source. 

Remote-Control Switches for Equalizer Circuits. — In large 
power houses of the modern type, considerations of economy as well as 
of convenience, dictate the placing of equalizer switches close to the genera- 
tors, for the reason that the cost of cable to connect the generator to the 
equalizer, if carried from the machine to the switchboard and back again, 
would be excessive. 



DISTANT CONTROL SWITCHES. 



963 



Figure 48 herewith is an illustration of a pair of switches, made by the 
Cutter Company for a large New York power house, that meet these condi- 
tions: The right-hand switch has a capacity of 2,000 amperes, and the left, 
3,000. The upper terminal of each of these switches connects with the 
equalizer main, which takes the place of the equalizer bus otherwise required 
at the switchboard. The lower terminal of each is connected with the 
appropriate terminal of the series winding of the corresponding generator. 
The closing of each switch, therefore, completes the equalizer circuit of 




Fig. 48. Remote- Control Switch for Equalizer Circuits. 



the generator with which it is connected. These switches are designed 
for control from a switchboard located at a distance, such control being 
effected by the movement of a small double-throw switch, bringing into 
circuit upon one movement the opening coil, and upon the opposite move- 
ment, the closing coil. Each switch is also provided with a nand-closing 
mechanism, so that it can be operated at the machine. 

Lever Switches. — Lever switches are plain knife blade switches 
and are for use on direct-current circuits up to 250 volts and on alternating- 
current circuits up to 500 volts. The design of these switches is thoroughly 
covered by the "Fire Underwriters Code." The accompanying diagram 
represents typical lever switches. It should be noted that for switches of 



964 



SWITCHBOARDS. 



this class, a capacity of 4500 amperes in a single switch is about as high 
as is practical, as heavier capacity switches are liable to be too hard for the 
ordinary attendant to operate manually. 





Fig. 49. S.P., S.T., 250- Volt 
200- Ampere Lever Switch. 



Fig. 50. 6000 Ampere, S.P., S.T. 



Quick lit calt Switches. — The quick break switch is essentially 
a lever switch provided with spring-driven follower blade which remains in 
the clips after the main blade leaves and is opened quickly by means of a 




Fig. 51. 



TO <C7" 

1000- Ampere 600- Volt Quick Break Switcb 



PLUG TUBE SWITCHES. 



965 



spring; the object being to break the circuit quickly and thereby lessen 
the burning of the contacts, also to have the follower take the burning 
instead of the main blade. A lever switch may also be opened quickly 
but a quick break switch cannot be opened slowly. 

The design of a quick break switch is covered by the "Fire Under- 
writers Code." A typical switch is illustrated in the accompanying 
diagram. 

Mug* Tube Switches. — The plug switch has many forms depend- 
ing on the use and the company manufacturing it. The principle of a 




==<|^^ 



Fig. 52. 10,000- Volt 10-Ampere Plug Tube Switch. 

plug tube switch is to rupture the circuit in a tube which is enclosed at one 
end, thereby confining the arc and limiting the supply of air. Plug 
switches are also used for transferring live circuits and for voltmeter and 
synchronizing circuits where there is no energy. 

Plug tube switches may be used on high voltage circuits providing the 
current capacity is low. They are being used extensively on 10,000 to 
20,000 volt series arc circuits, the current ranging from 4 to 7.5 amperes. 
One of these switches is shown in the accompanying diagram. 

Plug tube switches are also used on 100 ampere 2500 volt circuits. 

Disconnecting 1 Switches. — This type of switch is connected in 
series with oil break switches and other devices so as to be able to dis- 




Fig. 53. 15,000- Volt 300- Ampere Front Connected Disconnecting Switch. 

connect the oil switches, transformers or cable, as the case may be, from 
the live circuit or bus-bars in order to make alterations, repairs or adjust- 
ments. 



966 



SWITCHBOARDS. 



The form of switch is similar to the low- voltage lever switch except that 
it is mounted on insulators. It is not intended to open any load, with a 
possible exception of the magnetizing current of a transformer, and should 
not be used for such purpose. However, it should be thoroughly insulated 
for the voltage of the circuit to which it is connected and should be capable 
of carrying the maximum current of the circuit. Disconnecting switches 
for high voltage circuits, such as 60,000 volts, are designed with a view to 
rigidity rather than current-carrying capacity as the switch becomes very 
large and the current correspondingly small. 





Fig. 54. Rear Connected 300- Ampere 33,000- Volt Disconnecting Switch. 




Fig. 55. Front Connected 300-Ampere 33,000- Volt Disconnecting Switch. 
Disconnecting switches have the following voltage rating: 



Voltage 



f6,600-15,000 
! 22,000 
< 33,000 
45,000 
I 66,000 



These switches are made single pole only and are operated by means of 
a long wooden handle provided with a hook. This handle acts as insula- 
tion between the attendant and the switch. 



CIRCUIT BREAKERS. 967 



Switches for Higrh Potentials. 

Types. On American high-tension transmission lines there are four 
general types of switches now in use: 

(1) Switches designed to break the circuit in the open air. 

(2) Switches designed to break the circuit in an enclosed air space. 

(3) Switches designed to break the circuit with the aid of an enclosed 
metal fuse. 

(4) Switches designed to break the circuit under oil. 

Type No. 1. The large amount of space required by this switch, in order 
to be certain that the arc will be broken, makes its use limited and it can 
be used only with safety when the line potential is comparatively low for 
the reason that a circuit containing inductance and capacity may have 
very high-voltage oscillations set up in it by an open air arc unless the 
current is broken at zero value, resulting in highly increased voltage. 

Type No. 2. This switch occupies less space than type No. 1, but its 
effect on circuits containing inductance and capacity is very little different, 
so that there will be the same oscillatory rises of potential on opening the 
circuit. In addition, the explosion on opening heavy currents with this 
switch is at times so heavy as to endanger not only the switch itself but 
all delicate instruments in the immediate neighborhood. 

Type No. 3. Two forms of this switch have been more or less used. 
In the first form the fuse is connected in parallel, and in the second in 
series with the current-carrying parts of the switch. The first form is 
limited to low-voltage circuits, because of the unreliability of the enclosed 
fuse on comparatively high potentials when the circuit is fed from large 
central stations. The second form operates through the severing of a 
metal fuse within an enclosing tube filled with powdered carbonate of 
lime or some other non-conducting powder. The end of the fuse is drawn 
through the tube by the moving arm of the switch and the circuit is opened 
without serious commotion, if the switch has been well designed and care 
has been taken to properly fill the tube. This switch will open safely 
almost any circuit at almost any potential, but like the open air switch is 
limited by the amount of space required, and the powder set flying by the 
explosion of the arc is a decided objection if there is any moving machinery 
in the same room. 

Type No. 4. This type of switch is almost universally recognized as the 
only switch suitable for use upon high-tension circuits. 

It has been shown by numbers of experiments that the opening of a 
circuit by an oil switch is not a quick break; the oscillograph shows that 
the effect of the oil is to allow the arc to continue for several periods and 
then to break the current, as a rule, at the zero point of the wave. The 
result of the breaking at this point is that the opening of any circuit with 
oil switches is rarely accompanied by destructive rises of potential. An 
oil switch creates less fuss in the oil if it is opened slowly, but it is also true 
that an oil switch for 40,000 or 50,000 volts must have a depth of oil over 
the terminals of at least four or five inches. If less depth of oil is used, 
the oil is likely to be thrown out of the oil pots, on the opening of the 
circuit, although the arc will be broken. 

On the assumption that the oil switch is to be used for high-tension 
work, the following points of construction will bear consideration after the 
particular form of oil switch has been selected: 

(1) Rating. The performance of the switch under abnormal conditions 
of a low resistance short circuit should be considered as well as the capac- 
ity of the switch under normal operating conditions. 

(2) Oil. Any good paraffine oil will answer, but it should have about 
the following characteristics: flashing point not less than 180° C; fire-test not 
less than 200° C; specific gravity, .865; acid, none; alkali, none; evaporation, 
negligible. 

(3) Insulation. The insulator and insulating bushings should be either 
glass or porcelain. The switch should stand a break-down test between 
the live parts and the metal case and frame work of at least twice the 
working voltage applied for one minute. The external terminals should be 
far enough apart, or sufficiently well insulated, so that there can be no possi- 
bility of the current striking across through the air from terminal to terminal. 



968 



SWITCHBOARDS. 



(4) Location. Oil switches for use on circuits of above 6000 volts should 
be placed at a distance from the switchboard and away from the generat- 
ing and transforming apparatus. Each pole should be placed in a separate 
fire-proof cell, so that by no possibility could an arc or explosion in one cell 
be communicated to another cell, or to the neighboring machinery. 

(5) Method of operation. All switches should be either magnetically 
or electrically controlled from a central switchboard, and all the poles of a 
switch should be operated simultaneously. When equipped with relay 
for opening automatically this switch become:; one of the best forms of 
circuit breakers, and is so designated by the vVestinghouse Company. It 
is also desirable to equip each switch, especially if it is automatic, with a 
time element attachment, so that the circuit cannot be opened for at least 
a second after the operating mechanism is set in motion. 

Following are cuts of oil switches for different purposes and potentials 
as at present developed. 

In selecting the type of oil switch for any particular installation it is 
necessary to first determine the ultimate capacity of the installation and 
the total power which may be supplied to the switch from all sources. 
Care should then be taken to select the type of switch whose ultimate 
breaking capacity is not less than the ultimate capacity which may be 
supplied to it. 

It sometimes happens, however, when several stations are tied together 
by long transmission lines that it is impossible to concentrate all of the 




Fiq. 56. Type C Oil Circuit Breaker, Showing Oil Tank and Contacts. 



CIRCUIT BREAKERS. 



969 



power at certain stations on account of the drop in the line. Also, some 
sub-stations are well protected by having adequate switches installed on 
the outgoing feeders supplying this station from, the main generating 
station. In such cases it is sometimes possible to supply switches which 
have an ultimate breaking capacity that is less than the ultimate capacity 
of the sources of power connected to them, and such cases are exceptions to 
the rule. 

Westing-house Type € Oil Circuit Breakers. (Fig's. 56, 57.) 

This circuit breaker will open circuits carrying the heaviest currents 
encountered in modern practice. 

It is designed for operation on circuits up to and including 35,000 volts. 




Fig. 57. Type C Circuit Breaker, Side View. 



and will carry the normal current at 25 cycles, with a maximum rise not 
exceeding 25° C. 

Each pole is enclosed in a separate compartment. The mechanism is 
closed by means of a solenoid and opened by gravity. 

Terminals are brought out at the rear of the breaker, and the leads may 
be carried upward or downward in suitable runways, leaving no high- 
tension wiring exposed. 



970 



SWITCHBOARDS. 



Mounted on each circuit breaker is a small, double-pole double-throw 
knife switch. Provision is made for a second switch when required. The 
switch is operated by the motion of the levers of the oil switch and is used 
for the indicating and tripping circuits, also for use in electrically inter- 
locking the circuits when required. 



/?//JG/J/)M OrCOA/MCCTiONS 




forn?er<s. 



/fee? ?a/??p 



&ROrs»,K 




^^^^Uzfcl-a 



Note.— When Cir. Bkr. closes, red lamp is 
lit and green lamp dark. When Cir. Bkr. is 
opened by hand the green lamp is lit and red 
lamp dark. When Cir. Bkr. opens automati- 
cally the green and white lamps are lit and the 
red lamp is dark. When controller handle is 
raised to a horizontal position all lamps are 
dark, indicating that switch is out of service. 

Fig, 58. 

H. T. Lines. 



Series Trans. 




Coils connected of 
shown forl2Sie 
\z50Vo/ts. 

OL Connections 
H \forSOOvolt 
operation an? 
\ indicated t>y 
jotted tines, 

i 
J 

-Lint 



Fig. 59. 



Diagram of Connections. 3-Pole Electrically Operated Type C 
Oil Circuit Breaker. 



CIRCUIT BREAKERS. 



971 



tii 

= — ^ — & — s — s — » 

ft* 



fiecf/omp. 



■•4- 



7rlp 



Indicating 
Lamps 
' ^are enLonyx 



aearswi-kh 




COitS connected 
as shown for I2S» 

tsovotta. 

Connections for 
— —i SOOVO/vnttlori 
\oreir>ctfecrted 
\t>yavffod/Snesi 



7ow}gCe//f. 



-line 



Fig. 60. 



Diagram of Connections. 3-Pole Electrically Operated Non- 
Automatic, C Oil Circuit Breaker. 



Westing-house Type B Oil Circuit Breaker for Potential 
3500 to 32,000 Volts. 

The type B circuit breakers are made in the electrically operated form for 
potentials of 3500 to 22,000 volts, and in capacities up to 600 amperes. 

A simple system of toggles and levers is mounted on the top of the 
breaker, and a powerful electromagnet is arranged with its movable core 




Fig. 61. Hand-Operated , Automatic, 600- Ampere, 3-Pole, Type B, Oil Circuit- 
Breaker Mounted on Panel. Tank Removed, Open Position, not Over 
22,000 Volts. 

attached to the lever system, so that when it is drawn into the coil, the 
circuit breaker will be closed. A tripping-coil is also mounted with the 
operating mechanism. A small single-pole, double-throw switch is mounted 
on the breaker, and is operated by the motion of the levers in opening and 



972 



SWITCHBOARDS. 



closing the circuit; it controls the tell-tale indicator and lamp which ara 
mounted in view of the operator. These circuit breakers are operated by 
125, 250 or 500- volt direct current, and are calibrated for 25 cycles. 

The electrically operated type E oil circuit breakers are made both non- 
automatic and automatic, the latter being operated by means of overload 
relays. 

The breaker is made in single-pole units, each being mounted in a brick 
or concrete compartment. Two, three and four-pole combinations are 
made by placing these units side by side. The tanks are of a design similar 
to those of the type C circuit breakers. 

Oil Switch Structures. — The structural work for types C or E oil 
switches may be brick or concrete. 

When the structure is of brick, it is necessary that the anchor bolts pass 



/XT tmea 



7#rf79ffer 




Fig. 62. Diagram of Connections. 3-Pole Electrically Operated Type E 
Oil Circuit Breaker. 



outside of the brickwork. When the switch has a concrete base, however, 
the bolts are usually anchored in the concrete. The only soaps tone sup- 
plied with the type C oil circuit breakers is the top slab, the blocks to hold 
the terminal insulators in the rear, and the soapstone barriers between 
these terminals. 



Westing-house Type GA Electrically Operated Oil 
Circuit Breaker. 



Westinghouse type GA oil circuit breakers are designed for use on cirouits 
carrying large amounts of power. 

The distinctive features of the type G A circuit breakers are: Liberal 
insulation and breaking distances; open position maintained by gravity; all 
metal tanks and tank tops; accessibility of parts; long break in clean oil; 
low first cost. 

Construction. — Type GA circuit breakers consist of one or more poles 
self-contained in heavy steel oil tanks with treated linings and provided with 



CIRCUIT BREAKERS. 



973 



heavy cast-iron covers to which all of the mechanism for operating each pole 
is secured. Each pole is entirely separate and distinct from the others, the 
operating rod being the only connection between them. 




Fig. 63. 



Type GA Oil Circuit Breaker, without Closing Mechanism, for Po- 
tentials of 44,000 to 110,000 Volts. 



Current-carrying- Capacity. — Type GA circuit breakers are de- 
signed to carry 300 amperes per pole with a maximum temperature rise of 
20° C. They can be built with a larger current-carrying capacity if desired. 

Voltagres. — These circuit breakers are built for use on circuits of 44,000, 
66,000, 88,000 and 110,000 volts. 

Breaking 1 Capacity. — Type GA circuit-breakers are guaranteed to 
open any short circuit which may develop on transmission systems of the 
following capacities: 

60,000 kilowatts at 44,000 volts; 

80,000 kilowatts at 66,000 volts; 

100,000 kilowatts at 88,000 volts; 

120,000 kilowatts at 110,000 volts. 

Tlie breaking* distances, or distances between contacts when the 
circuit breaker is open, are large and there are two breaks on each pole. The 
breaking distances of different capacity circuit breakers are given in the follow- 
ing table: 



974 



SWITCHBOARDS. 



Breaking* Distances. 



Amperes. 


Voltage. 


Minimum Dis- 
tance of Terminal 
to Case or 
Ground. 


Breaking Dis- 
tance per Break, 
Inches. 


Breaking Dis- 
tance per Pole, 
Inches. 


300 
300 
300 
300 


44,000 
66,000 
88,000 
110,000 


16 
22 
30 
32 


11.5 

16.5 

20 

23.5 


23 
33 
40 
47 




Fig. 64. Westinghouse High-Potential Fuse-Type Circuit Breaker — Open 
Position for Potentials not Exceeding 66,000 Volts. 

High-Potential fused Circuit Breaker, Westingrhouse. — 

This fuse-type circuit breaker consists of a long hardwood pole on which is 
mounted a movable arm consisting of a reinforced fuse tube. At the bottom of 
the fuse tube is a brass expulsion chamber which is connected to the lower ter- 
minal of the breaker by a flexible copper shunt. Attached to the top of the 
pole and forming the upper circuit-breaker terminal there is a brass bracket, 
with a groove along its top, which supports the fuse, and a wing nut to hold the 
end of the fuse when the breaker is closed. The fuse passes from the wing nut 
over the bracket and down through the fuse tube to the expulsion chamber when 
it is attached to the screw-plug terminal shown in the end of the expulsion 
chamber. The pole of the circuit breaker is provided with spring jaws or clips 
so that it may be quickly and easily attached to or detached from the line 
terminals at the base. 

Adjustment. — First: Remove the mechanism from its base, taking hold 
of the long pole. 

Second: Remove the screw-plug terminal from the lower end of the expulsion 
chamber and attach the fuse to the terminal . 

Third: After passing the fuse through the fuse tube replace the screw plug 
and attach the other end of the fuse to the wing nut on the bracket at the upper 
end of the long pole, passing a turn or two around the lug, at the same time 
drawing the moving arm into its proper position against the end of the bracket. 

Fourth: Replace the mechanism on the base and the breaker is ready for use. 

Operation. — When the load on the line exceeds the capacity of the fuse 
the latter blows and the arm of the breaker swings by its own weight away from 
the upper line terminals, thus giving a positive indication that the fuse has blown. 



CIRCUIT BREAKERS. 



976 



Oil Circuit-Breaker Controller. — This controlling switch is 
of the drum type with a hinged handle, which, when thrown to the open 
position, may be locked by swinging the handle outward so that it is in 
line with the drum shaft. It cannot be locked in the closed position. 
When the handle is raised as described it indicates to the operator that the 
switch is out of service. The act of raising the handle cuts the current off 
from the controller and thus extinguishes the lamps. The switch is 
arranged for switchboard mounting, the dial and handle being on the face 
of the panel. It may also be provided with an indicator to show the 
last operation performed. 




Fig. 65. Controlling Switch, Cover Removed 



Lamp Indicator for Oil Circuit Breaker. — The indicator 
consists essentially of a hollow tube with a lamp socket mounted on a 
porcelain base in one end, held in position by suitable clips. The socket 
can be easily removed and is intended to hold a 5 c.p. candle-shaped in- 
candescent lamp which extends into the tube. Suitable holes are pro- 
vided for ventilation. 

A colored lens is secured to the front end of the tube. A special feature 
of the lens is a V-shaped projection which extends across its face, enabling 
the operator to see the light from any angle within an arc of 180°. 

Control and Instrument JLeads. — The control wires for the 
electrically operated circuit breakers are run in conduits, or in some other 
suitable manner, to the place where the operating switchboard is located. 
The small size of the controlling and conducting devices permits a large 
number to be grouped in a comparatively small space where they are easily 
accessible to the operator. 

The sizes of conductors usually required where lengths do not exceed 
200 feet, are as follows: 

For series tranformer circuits, each lead equivalent to No. 7 B. <fe S. 
conductor. 

For voltage transformer circuits, each lead equivalent to No. 10 or 12 
No. B. & S. conductor. 

For static ground detectors, each lead equivalent to No. 10 B. & S. con- 
ductor. 

For oil circuit breaker, 1 closing coil lead equivalent to No. 7 conductor, 
B. & S.; 1 tripping coil lead equivalent to No. 12 conductor, B. & S.; 2 
indicator leads equivalent to No. 12 conductor, B. & S. 



976 



SWITCHBOARDS. 




Fig. 66. 13,000- Volt, 500-Ampere T. P. Motor Operated Oil Break 
Switch as Manufactured by the General Electric Company. 



CIRCUIT BREAKERS. 



977 




Fig. 67. 3 Single-Pole, 45, 000- Volt, 300- Ampere Solenoid Operated Type " F," 
Form "K21," Oil Switch as manufactured by the General Electric 
Company. 






€ 



THREE-PHASE 





r- 


— r^ 




111 

r-»T] 


i\ 


lo o 
1? ? 

!! 


m 


+ 



THREE-PHASE 




THREE-PHASE 
(GROUNDED NEUTRAL) 



CONNECTIONS OF ELECTRICALLY OPERATED OILSWITCHES OPERATED 
BY DIRECT*CURRENT BY MEANS OF CIRCUIT' CLOSING RELAYS 



978 



SWITCHBOARDS. 



CONNECTIONS OF HAND OPERATED ELECTRICALLY 

TRIPPED OIL SWITCHES WITH TRIP COILS OPERATING 

ON D.C. CIRCUIT USING CIRCUIT CLOSING RELAYS 




8INGLE-PHA6E THREE-PHASE 



THREE-PHASE 



,M 



t^J 




THREE-PHA8E 
(GROUNDED NEUTRAL) 






-OIL SWITCH 
TRIP COIL 



AUXILIARY 8WITCH 
ON OIL 8WITCH 



'/K l '/[\* iff 



GROUND - 
CURRENT TRANSFORMER* 



GENERATOR 



TWO - PHASE 
CPHA8E8 INTERCONNECTED) 



Fig. 68. 



CIRCUIT BKEAKEBS. 



979 



A 
i 



CONNECTIONS OF HAND OPERATED ELECTRICALLY TRIPPED 

OIL SWITCHES WITH TRIP COILS OPERATING FROM CURRENT 

TRANSFORMERS THROUGH CIRCUIT OPENING RELAYS 



V& 




NGLE-PHASE THREE-PHASE i THREE-PHASE TWO-PHASE 

Fig. 69. 




Fig. 70. General Electric Company Type F, Form K 3 - 
100 Amperes, 2500 Volts T.P.S.T. Oil Switch. 



LIGHTNING ARRESTERS. 

Revised by Townsend Wolcott. 
LIGHTAOG PROTECTION 

(From Bulletins of W. E. & M. Co. and G. E. Co.) 

Electrical apparatus may receive injuries of two sorts from lightning, 
namely, grounds and short circuits. (1) A ground or connection between 
the circuit and the earth is caused by the potential of the insulated portions 
of the apparatus rising abnormally above that of the earth and thereby 
rupturing the insulation. But as any properly designed piece of apparatus 
has sufficient insulation strength to withstand a potential considerably 
higher than that normally impressed upon it, a lightning discharge to 
produce a ground must cause a very considerable rise in the potential of the 
circuit. (2) Short circuits are caused by the abruptness of the static 
disturbances produced by lightning. The abruptness of the static wave 
which is the form of disturbance produced in the line by the lightning dis- 
charge, may strike a coil a blow, so to speak, that under some circumstances 
causes a short circuit. Electric apparatus requires, therefore, lightning 
protection of two sorts. First, protection against grounds; second, against 
short circuits. Protection from grounds is secured by means of lightning 
arresters; protection against short circuits, by choke coils or static inter- 
rupters. In very high tension circuits all sudden changes of static potential, 
such as may be produced by switching, accidental grounds, or short circuits, 
cause the same abrupt static disturbances as lightning. 

The Function of a Ttig-ntning* Arrester. — The proper function 
of a lightning arrester is to prevent, in an insulated circuit, an abnormal rise 
of potential above the earth. This result is best attained by placing one or 
more carefully adjusted air gaps between the insulated circuit, commonly 
called the "line," and the earth connection, or "ground." Except during 
times of discharge, these gaps resist any flow or current arising from the 
normal voltage of the line; but, whenever the line potential rises abnor- 
mally, they break down, allowing* a free discharge of electricity. By care- 
ful adjustment of the gaps, an arrester can be made to discharge when the 
voltage of the line has risen to any predetermined value. 

On account of the extreme suddenness of the surges caused in the line 
by lightning discharges and other static disturbances, the gaps and ground 
connection must be able to discharge electricity very freely or a dangerous 
rise of potential of the line will not be prevented — in other words, the light- 
ning arrester as a whole must be able to discharge electricity faster than 
it appears on the line. 

It is found that there is a very strong tendency, especially with generators 
of large output and high voltage, for an arc to form in the gaps when once 
their resistance is broken down by a lightning discharge. This arc, which 
can occur only when one line is grounded, or when two legs of the same 
circuit discharge at once, is maintained by the generators, and if not pre- 
vented or extinguished will cause a shut-down of the plant. Consequently 
the lightning arrester, in addition to preventing an abnormal rise of line 
potential, must also suppress any arc which tends to form in the arrester 
gaps. 

Switching-. 

On high potential circuits of considerable capacity, an arc produced by 
switching, circuit breakers, fuses, or short circuits, causes an electrical 
oscillation of extremely high value. Voltages of double normal potential 
are often produced when connecting a circuit of considerable capacity to 
the generating system at no load. These high potentials subject the appa- 
ratus momentarily to enormous strains, and it is well to have some low 
breakdown path in which the dynamic arc will be immediately ruptured, 
so that these high potentials will equalize themselves from line to line with- 
out damage to the apparatus. 

980 



LIGHTNING PROTECTION. 981 



Cables. 

In laying out circuits, it is frequently necessary and desirable to dip 
underground when passing through cities, or under rivers, etc., and in these 
cases some form of metal covered cable is generally used. It has been 
noticed from numerous installations that high potentials invariably occur 
where these underground cables are used, due to resonance effects, and 
these high potentials are often of sufficient value to break down the cables 
themselves, or the insulation of apparatus installed on the lines. The 
strains very often produce pinhole punctures in the insulation of under- 
ground cables and thus relieve themselves temporarily; they may there- 
fore remain unnoticed for a number of months until the insulation becomes 
very much impaired, ultimately resulting in a complete breakdown. 

Whenever lines contain both inductance and capacity in noticeable 
quantities, high voltages, which endanger the insulation of the whole 
system and which it is impossible to detect on ordinary switchboard instru- 
ments, may exist. We therefore frequently find such abnormal voltages 
in circuits containing a combination of underground and overhead cir- 
cuits, and in long-distance transmission lines. 

JEng*ine or Water Wheel Governor Troubles. 

A great many cases have been noted where engines and water wheels 
have raced, caused by the governors becoming inoperative, and high poten- 
tials have resulted, which have caused serious breakdowns in insulation. 
This has generally occurred when a considerable load has been switched off 
from a circuit. 

Difference in Elevation Between Different Portions of 
the Circuits. 

Particular mention was made at the recent meeting of the A. I. E. E. at 
Niagara Falls, of the abnormal high potential strains which have been 
noted on long transmission lines running through mountainous countries 
where considerable differences of elevation occur between different portions 
of the circuits. These differences in potentials are, without a doubt, due 
to difference in magnitude of the atmospheric electrical potential at differ- 
ent altitudes, and in some cases the condenser effects of the line produce 
potentials considerably in excess of the line voltages. 

Protection Against Abnormally Hig-li Potentials on 
A. C. Circuits. 

In planning protection against the disturbances previously mentioned, 
it is necessary to provide discharge paths from line to line of the different 
phases, and discharge paths from lines to ground with suitable ground 
connections, except when the circuits are entirely underground, when the 
ground connections may be omitted. 

In view of the fact that it is necessary to take care of considerable quan- 
tities of current from line to earth when lightning discharges take place, it 
is advisable to have an arrester of as large current carrying capacity as 
possible, and with this in view, it is often advisable to install a number of 
arresters in multiple where the conditions are particularly severe. 

Potentials between lines, which are more of a static nature, can gen- 
erally be equalized with small flow of current. 

In discharging a line to ground, the simplest form of discharger would be 
one single gap, or a series of small gaps with a breakdown point just above 
the voltage of the circuity Although it has been found that a single gap 
will discharge a line effectively, the single gap, of course, will not rupture 
the dynamic arc when it is once started by a high potential discharge. 

With a sufficient number of short gaps, it has been found that under 
certain conditions, the dynamic current is ruptured by cooling the arc down 
between the numerous conductors; also due to the fact that in some of the 
gaps the value of the alternating wave is zero, and, therefore, after a high 



982 LIGHTNING ARRESTERS. 

potential discharge has passed, the dynamic arc does not start again. This 
arrangement of a large number of small gaps in series is, however, out of 
the question as far as practical use is concerned, as enormously high break- 
down voltage is necessary to overcome the gaps, resulting in injurious 
strains on the insulation of the apparatus, under certain conditions of 
inductance, capacity, etc., a discharger of this construction will not inter- 
rupt the dynamic arc. 

Having selected a length of spark gap as a standard, the point above 
the line voltage at which it is decided that the arrester shall discharge 
should be decided upon. A definite number of these standard gaps will be 
necessary to prevent the arrester from discharging below this point, and 
this number of gaps will interrupt the dynamic arc, provided the current 
is limited to a proper value. With this in view, it is necessary to place a 
determinate resistance in series with the gaps, in order to limit the current 
to this point. 

High potentials between lines or phases occur much more frequently than 
is the case with lightning, and it is advisable to increase the non-inductive 
resistance in series with the gaps to a considerable extent, as this renders 
the possibility of short circuits less liable and, as stated above, these high 
potentials between phases can be equalized through high resistances as well 
as through low resistances. A further reason for placing a considerable 
amount of resistance in series with the gaps when placed between lines is that 
in case of discharge from phase to phase, if the resistances are low, the 
circuit breakers or other automatic devices on the line open, causing a 
temporary shut-down, and this, of course, is inadvisable as well as annoying. 

Use of Reactive Coils. 

Although considerable doubt has existed as to the advisability of in- 
stalling reactive coils in connection with lightning discharges, it is believed 
by many prominent engineers that reactive coils are of considerable value, 
in connection with the proper protection of apparatus. 

Without a doubt, the frequency of lightning disturbances varies greatly 
in different cases, although, asa whole, it is probably high. Inasmuch 
as the action of the reactive coils is not dependent on the voltage or fre- 
quency of the line, it is inadvisable to design a large number of coils having 
different reactances, and it is evident that a coil can be designed with ample 
current carrying capacity, which may be used on a number of voltages, 

frovided it has sufficient insulation for the highest voltage determined upon, 
n this connection, air insulation is to be inferred between turns and layers, 
as other forms, due to minute discharges, gradually deteriorate and change, 
becoming partial conductors. 

Use of a Protective Wire. 

Protective wires have been used in a great many cases by different trans- 
mission companies with varying success, although the experience gained, 
as a whole, has been in favor of this form of protection. A great many of the 
troubles encountered through the use of this wire have been due to the 
selection of improper materials in making the insulation. Barbed wire has 
been used in a great many cases, and the commercial barbed wire purchased 
in the open market is of very poor quality and has a tendency to hold water 
in the joints and interstices. 

In one place, in particular, different forms of protective wire have been 
used, placed in various positions with regard to the circuit wires, and it 
has been found that plain iron wire installed directly below the transmission 
wires, furnishes practically as good protection as barbed wire installed over 
the transmission. 

As a matter of fact, there are few reasons why this should not be the case, 
provided the iron wire is properly grounded at every third or fourth pole, 
as the disturbances which this form of protection is supposed to take care 
of are generally at considerable distances from the transmission wires. 

While this form of protection may help out in the case of a direct stroke 
of lightning, it is not to be presumed that it will prove entirely efficient under 
this condition of affairs. 



LIGHTNING ARRESTERS. 983 



While the experience of the above mentioned plant has been that a wire 
placed below the transmission is as satisfactory as if placed in any other 
position, it is as well to string it above the transmission lines at an angle of 
approximately 45° to the outside transmission wires, as this locality will aid 
in taking care of direct strokes of lightning. 

With the improved lightning protective devices on the market, the 
grounded protective wire need only be resorted to where the most severe 
conditions exist, and then it should be put up in the most thorough manner 
with regard to the size and quality of the material used and with regard to 
grounds. 

Ground Connections. 

In the installation of lightning arresters it is very undesirable to endeavor 
to effect a saving by cutting down the expenses connected with making 
proper ground connections, as fully 75% of lightning arrester troubles can 
be traced directly to this source. 

The connections from the line to the arrester and from the arrester to the 
ground should be as free from angles and bends as possible, and where turns 
are absolutely necessary, the wire should never be bent at an angle, but in a 
curve of long radius. Care should be taken that no inductive loops are 
formed by the complete arrester and its connections. 

When the use of an iron pipe at the foot of a pole is considered advisable 
for the protection of the ground wire, a plug should be put in the top of 
the iron pipe and the wire soldered to it ; otherwise the reactance of the 
ground wire surrounded by the iron pipe will impede the discharge. 

Copper sheets should be used for the ground, thick enough to prevent 
wasting away and having at least 4 square feet surface. The ground wire, 
which should not be less than f inch diameter in cross section, and prefer- 
ably in flexible strip form, must be carefully soldered and riveted to this 
plate, the joint covered with asphaltum, and the plate then buried in 
powdered coke in soil which is always damp. 

Dry, sandy soil should be kept wet by artificial means if this is the only 
soil available for the ground connection, and it is advisable to dig several 
trenches radiating out 50 feet from the main ground wire, in which ground 
wires are buried, so as to get a large surface for the dissipation of the dis- 
charges. Where plates are buried in streams of running water or dead 
water, they should be buried in the mud along the bank in preference to 
merely laying them in the streams, and streams with rocky bottoms are 
to be avoided unless as a last resort. Where there are metal flumes, pipes or 
rails, it is advisable to rivet and solder the ground wires to them in addition 
to the connections to the copper plates, and when rails are utilized they should 
be thoroughly grounded. 

XjigTitning* Arresters. 

Practically all plants with outdoor circuits require lightning protection. 
With reference to the type of lightning protection required, electric plants 
may be divided into two general classes — those plants in which the ap- 
paratus is widely distributed, and those in which the apparatus is concen- 
trated at a comparatively few points. 

JPlants Having- Apparatus Distributed. — To obtain abso- 
lute protection, arresters must be placed at all points where apparatus is 
located, but experience has shown that in certain cases such a large number 
of arresters is unnecessary. 

In circuits not exceeding 2500 volts, it will usually be sufficient to place 
arresters at various intervals where good grounds are available. These 
arresters should be so placed as to leave no considerable length of circuit 
(electrically speaking) unprotected, and should be more numerous in neigh- 
borhoods where the circuits are exposed. These are more likely to be the 
outiying districts where the lines are not protected by buildings and trees. 
The exact number to be used in any given case depends upon circumstances. 
Under average conditions satisfactory protection will be secured if no point 
of the circuit be more than 1000 feet from an arrester. 

For voltages exceeding 2500 volts, arresters should be placed as nearly as 
possible at or near apparatus on exposed lines. However, circuits of this 
type with voltages exceeding 2500 are rare. 



984 LIGHTNING ARRESTERS. 

Plants Having- Apparatus Concentrated at a Few 
Points. — In plants of this class, which comprise practically all high ten- 
sion work, one arrester should be used for each line wire, at or near each point 
at which apparatus is connected to the circuit. 

In all cases of circuits with ungrounded neutrals, arresters rated at the 
voltages between line wires should be chosen; that is, for the maximum 
working voltage and not for the voltage between line and ground. This 
method insures that the arrester will be non-arcing when one leg of the cir- 
cuit is accidentally grounded. 

If the circuit has a Grounded Neutral, arresters, to secure ample margin 
for protection, should be chosen for a voltage 20 per cent greater than the 
maximum voltage between line and ground. For example, for a circuit 
with grounded neutral having 16,500 volts between line and ground (ap- 
proximately 28,000 volts between lines) arresters for 20,000 volts should be 
chosen. If, however, the transformers are connected in star in both high 
tension and low tension windings, arresters should be chosen as though 
the neutral were not grounded. 

The arrester should always be placed on the line side of all apparatus. 
The arrester (if of low equivalent alternating current type) is chosen solely 
with reference to the voltage of the line upon which it is placed, and is inde- 
pendent of current. 

Insulation. — A lightning arrester is naturally exposed to severe potential 
strains, and therefore all active parts must be well insulated. To obtain 
sufficient insulation on circuits exceeding 6000 volts, the panels should be 
mounted on shellacked wooden supports, well seasoned and very dry. On 
arresters exceeding 12,500 volts, the panels should receive additional 
insulation in the form of porcelain or glass insulators. It should be assumed 
in installing an arrester that all parts of the resistance except the ground 
terminal of the series resistance may be momentarily at line potential during 
the discharge. Two high tension arresters attached to different line wires 
should not be placed side by side without either a barrier or a considerable 
insulation space between them. The resistance, which during the dis- 
charge may reach full line potential, must be spaced or insulated (except the 
ground end of the series resistance) as well as the line. 

Inspection. — As the effectiveness of the arrester is of great importance 
it should be inspected from time to time and the resistances and earth 
connection tested for open circuit. 

Choke coils should be so mounted as to have free access of air for cooling 
purposes, and should be so spaced from one another and removed from other 
objects that sufficient insulation space will be obtained for the most severe 
conditions, viz.: during lightning discharges. 

IieHTIII« ARRE§TER§ TOR DIRECT CURRENT. 

A non-arcing D. C. arrester has been devised by Mr. A. J. Wurts based 
upon the following facts: — 

First. A discharge will pass over a non-conducting surface, such as glass 
or wood, more readily than through an equal air-gap. 

Second. The discharge will take place still more readily if a pencil or 
carbon mark be drawn over the non-conducting surface. 

Third. In order to maintain a dynamo arc, fumes or vapors of the elec- 
trodes must be present; consequently, if means are provided to prevent the 
formation of these vapors there will be no arc. 

The Type " K " Arrester. — The illustration, Fig. 1, shows the 
type "K" arrester for station use on D. C. circuits up to 700 volts. The 
instrument is single pole, and consists of two metal electrodes mounted 
upon a lignum-vitae block, flush with its surface. Charred or carbonized 
grooves provide a ready path for the discharge. A second lignum-vitae 
block fits closely upon the first block, completely covering the grooves and 
electrodes. Disruptive discharges will pass readily between the electrodes 
over the charred grooves, which act simply as an electrical crack through 
the air, providing an easy path. 

The resistance between the electrodes is more than 50,000 ohms, so that 
there is, of course, no current leakage, but it should not be understood that 
the lightning discharge passes through this high resistance — it leaps over 



ARRESTERS FOR DIRECT CURRENT. 



985 







<S> 





•e 




f 




> 


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o 




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o 


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J 


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<s> 




Fig. 1. Non-Arcing Railway Lightning Arrester, Type "K." 
(For Station Use.) 

the surface of the charred grooves from one electrode to the other exactly 
as it would if there were but a simple air-gap. The presence of the charred 
grooves simply makes the path easier. , 

There being no room for vapor between the two tightly fitting blocks, no 
arc can be formed, hence the arrester is non-arcing. 

Some years ago Prof. Elihu Thomson devised a lightning arrester based 
on the principle that an electric arc may be repelled by a magnetic field. 



© \\ 


/( 


\Pj! 


r 

© 


^g--— ^ 










, g> ,1 


m 














^|t||i|: 




willlllb' 


(o\ 


^- — - — - — 







Fig. 2. Type "A" Arc Station Arrester. 



In this device, the air-gap, across which the lightning discharges to reach 
the ground, is placed in the field of a strong electro-magnet. When the 
generator current attempts to follow the high potential discharge, it is 
instantly repelled to a position on the diverging contacts where it cannot be 
maintained by the generator. 



986 



LIGHTNING ARRESTEES. 



The magnetic blow-out principle has been employed in the construction 
of a complete line of lightning arresters for all direct current installations, 
and in more than ten years of service magnetic blow-out arresters have 
always been effective in affording protection to electrical apparatus. 

In designing lightning arresters for the protection of high-voltage alter- 
nating current circuits, however, different conditions have to be met, since 
high-voltage arcs are not readily extinguished by a magnetic blow-out. In 
a recently designed lightning arrester for alternating current circuits, 
metallic cylinders with large radiating surfaces are found so to lower the 
temperature of the arc that volatilization of the metal ceases and the arc is 
extinguished. 

The variety hi these lightning arresters provides for the protection of all 
forms of electrical apparatus and circuits. 

The Type * 4 A" Arrester is manufactured for the protection of arc lighting 
circuits. Its construction includes a pair of diverging terminals mounted 
on a slate base with an electro-magnet connected in series with the line. 
The magnet windings are of low resistance, and therefore consume an in- 
appreciable amount of energy with the small current used for arc lighting, 
although they are always in circuit. 

The single Type "A" Arrester is suitable for circuits of any number of 
series arc lamps not exceeding seventy-five. For circuits of higher voltage, 
a double arrester known as the type "AA" is made by mounting two 
arresters on one base and connecting them in series. One arrester should 
be installed on each side of the circuit, as shown in the Diagram of Con- 
nections. 

For use in places exposed to weather, the Type "A" Arrester is furnished 
enclosed in an iron case, and designated Type "A," Form *'C." 




© 

ij.i 

© 
® jj 


U' 


fi J 

fi 

ii m 





, 3. Connections for Type 
"A" Arresters. 



Fig. 4. Type "B" Incandescent 
Station Arrester 300 Volts or Less. 



The construction of the Type "B" Arrester is similar to that of the Type 
" A, " but its magnet windings are excited only when a discharge takes place 
across the air-gap. A supplementary gap is provided in the Type "B" 
Arrester, in shunt with the magnets, thus providing a relief for the coils 
from excessive static charge without affecting their action upon the main 
gap. The magnet coils, carrying current only momentarily, allow the same 
arrester to be used on circuits of large and small ampere capacity. The 
Type *'B" can also be furnished with weatherproof case similar to that 
used with Type "A." 

The Type "MD" Lightning Arrester has been designed for use on direct 
current circuits up to 850 volts. While similar to Type "M," Form "C, " 
Arrester, it is considerably smaller, and is enclosed in a compact porcelain 
box measuring 7£ inches x 5 inches x 4£ inches. For street car and line use, 
the arrester is furnished in an additional baK of iron or wood. 



LIGHTNING ARRESTERS FOR ALTERNATING CURRENT. 987 

The arrester has been adopted as standard for railway and all direct 
current 500-volt circuits. It has a short spark gap, a magnetic blow-out 
and a non-inductive resistance. 



CONNECTIONS OF 

MAGNETIC BLOW-OUT LIGHTNING ARRESTERS TYPE MD. 

FOR DIRECT CURRENT CIRCUITS OP TO 850 VOLT8. 



CONNECTIONS FOR LIGHTING OR POWER CIRCUITS. 
(METALIC CIRCBIT8) 



REACTANCE COIL 




CONNECTIONS FOR RAILWAY 
CiROUIT 
(ONE StDS GfiOUMDEO) 

REAOTAKCe COtLJB COMPOSED OF 

25 FT. OF CONDUCTOR WOUND ffl A 

COIL OF TWO OR MORE TURKS 

AS CONVENIENT. 




Fig. 5. Connections of Magnetic Blow-out Lightning Arresters, 
Type "MD," for Direct Current Circuits up to 850 Volts. 



IIGHTXOG ARRESTERS FOR AJLTERXATXIVO 
CCRREHT. 

•The G. E. Alternating Current Arresters have been designed to operate 
properly with very small gap spaces. The arrester for 1000-volt circuits has 
two metal cylinders 2 inches in diameter and 2 inches long, separated by a 
spark gap of about ■£% inch. One cylinder is connected to the overhead 
line and the other cylinder to the ground, and a low non-inductive graphite 
resistance is placed in circuit. The large radiating surface of the metal 
cylinders combined with the effect of the non-inductive resistance prevents 
heating at the time the lightning discharge passes across the gap, and the 
formation of vapor which enables the current to maintain an arc is thus 
avoided. 

The arrester under normal action shows a small arc about as large as a 
pin-head between the cylinders. 

The arrester for 2000-volt circuits is designed with two gaps of approxi- 
mately 3*5 inch each and a low non-inductive resistance. 

The G. E. Arresters are now furnished by the General Electric Company 
for use on all alternating current circuits at practically any potential. For 
circuits above 2000 volts, the standard 2000-volt double-pole arrester hae 
been adopted as a unit, and several of these are connected in series to give 
the necessary number of spark gaps. 



988 



LIGHTNING ARRESTERS. 




REACTANCE COIL 



Fig. 6. G. E. Alternating Current 
Three-Phase Multiplex Lightning 
Arresters, 




10000 V. ARRESTER CONSISTS CF FOUR 2000 
V.D.P. ARRESTERS CONNECTED IN SERIES. 




[L^j i^jj 



20 




2000 V.D.P. ARRESTERS CONNECTEO AS 
8000 V.S.P. ARRESTERS. 



Figs. 7, 8, 9. Connections of G.E. Alternating Current Lightning Arresters 
2000, 3000, 10,000 Volts. 



LIGHTNING ARRESTERS FOR ALTERNATING CURRENT. 989 

1000 V0LT3 



9000 VOLTS 




LINE 
ARRE8TCR 



DYNAMO 

—rfl Ck-Q- 



imr jrilfr ME 

J GROUND 




Fig. 10. Diagram Showing Electrical Connections for A. C. Lightning 
Arresters. 




Fig. 11. 



Double-Pole Non-Arcing Metal Lightning Arrester, Type "A.' 
(For Station Use.) 



The J¥on -Arcing* .ffotal JLig*htning* Arrester. — The non- 
arcing metal lightning arrester made by the Westinghouse Co. for alternat- 
ing current circuits is based upon the discovery made by Mr. A. J. Wurts 
that an alternating current arc cannot be maintained over a short air-gap 
when the electrodes consist of certain metals and alloys thereof. Types *' A " 
and "C" arresters, described below, are of the non-arcing metal type. 

The Type k4 A" Arrester. — The construction of this arrester can 
be best understood by reference to Fig. 11. 

It will be noted that there are seven independent cylinders of non-arcing 
metal placed side by side and separated by air-gaps. The cylinders, which 
are mounted on a marble base, are knurled, thus presenting hundreds of 
confronting points for the discharge. The dynamo terminals are connected 
to the end cylinders, and the middle cylinder is connected to the ground. 
The arrester is, therefore, double pole, that is, one arrester protects both 
sides of the circuit. When the lines become statically charged the dis- 
charge spark passes across between the cylinders from the line terminals to 
the ground. The non-arcing metal will not sustain an arc or become fused 
by it; hence with an arrester constructed of this material all possibility of 
vicious arcing and short circuits is avoided. 



990 



LIGHTNING ARRESTERS. 



The Type u C " Arrester. — This is similar to type "A," but instead 
of being mounted on marble it is enclosed in a weather-proof iron case for 
line use. The cylinders are placed in porcelain holders, as shown in Fig. 12. 





Fig. 12. Unit Lightning Arrester, Type"C," Showing Cylinders in Place. 



Tlie Garton Arrester. — In Fig. 13 a cross- 
section view is shown of the Garton Arrester. 

The discharge enters the Arrester by the bind- 
ing post A, thence across non-inductive resistance 
B, which is in multiple with the coil F, through 
conductors imbedded in the base of the Arrester, 
to flexible cord C, to guide rod D and armature 
E, which is normally in contact with and rest- 
ing upon carbon H, thence across the air-gap to 
lower carbon J, which is held in position by 
bracket K. This bracket also forms the ground 
connection through which the discharge reaches 
the earth. 

We have noted that the discharge took its 
path through the non-inductive resistance in 
multiple with the coil. This path is, however, 
of high ohmic resistance, and the normal cur- 
rent is shunted through the coil F, which is 
thereby energized, drawing the iron armature 
E upward instantly. This forms an arc between 
the lower end of the armature and the upper 
carbon H. As this arc is formed inside the 
tube G, which is practically air-tight, the oxygen 
is consumed, the current ceases, and the coil 
loses its power, allowing the armature to drop 
of its own weight to its normal position on 
the upper carbon. The arrester is again ready for another discharge. 

The S. K. C JLigrhtning- Arrester Equipment, manufactured by 
the Stanley Electric Mfg. Company of Pittsneld, Mass., consists of three 
essential parts. The Lightning Arrester proper is two nests of concentric 
cylinders, with diverging ends held in relative position by porcelain caps, as 
shown in cross section, Fig. 14. To the innermost cylinder the line is con- 
nected ; to the outer, the earth. The porcelain caps are provided with 




Fig. 13. 



THE GARTON ARRESTER. 



991 



grooves so placed as to make all spark gaps one-sixteenth, inch wide. Be- 
tween these grooves are sufficient perforations to allow the free circulation 
of air between the cylinders. If, on the occasion of lightning, the dynamo 
current follows the lightning, a current of air is at once established through 
the perforations between the cylinders, blowing the arc between the flar- 
ing ends where it is instantly ruptured. 

Between the line terminal and the ground connection there are three 
spark gaps, each one-sixteenth inch in width, making a total of three-six- 




VERTICAL-SECTION OF 
UGHTNINft ARRESTER 



Fig. 14. 




Fig. 15. 



teenth inch air-gap between either line-wire and the ground. At ordinary 
frequencies five thousand volts or over are required to jump the gaps of the 
arrester ; but at the frequency of a lightning discharge the sparking poten- 
tial is reduced to less than one-half of this. This phenomenon shows that 
the relative value of spark gaps cannot be expressed by "short" and 
" long," and their effectiveness as lightning protection cannot be measured 
by inches. 

The spark gaps of the arrester described are about double the widths 
ordinarily used, yet the sparking potential at lightning frequencies is less. 
The concentric cylinders provide large discharge surface, enabling the 
arrester to take care of all the heavy discharges, relieving the line completely. 

The second essential feature of the S. K. C. Lightning Arrester Equipment 
is a Choke Coil, so wound (Fig. 15) as to possess great opposition to the 
passage of lightning, yet practically no self-induction with currents of ordi- 
nary frequency. This coil is to be placed in 
the circuit between the lightning arrester and 
the apparatus to be protected. Introducing 
such a coil between the lightning arrester 
and the machine will offer practically no dis- 
turbing effect, either as to magnitude of the 
output or regulation of the system, and at the 
same time interposes enormous opposition to 
the passage of lightning discharges towards 
the machine to be protected. 

To remove even the slightest static discharge 
from the line, an instrument similar to the 
one illustrated in Fig. 16, called a "Line 
Discharger," when used with the apparatus 
above described, discharges the line com- 
pletely. The S. K. C. Line Discharger is a 
minute air-gap in series with a tube or tubes, 
filled with oxidized metallic particles, thus 
offering practically an infinite resistance to dynamic currents, yet allowing 
static discharges of extremely low potential to pass readily to earth. The 
Line Discharger is connected to the line as shown in Fig. 17. The number 




Fig. 16. 



992 



LIGHTNING ARRESTERS. 



of tubes required is determined by the voltage. As the Line Discharger will 
remove even the small static charge, it prevents the accumulation of such 
charges on the line which might prove dangerous. 




LilUUriJgt. 25-239 



GROUND 



GROUND 

LIGHTNING PROTECTION 

FOR 

6000 VOLT TRANSMISSION* LINE 

USING 

6.k.c. arresters, choke coils and 
line discharges 

Fig. 17. 



Static Dischargers. 

Where circuits are entirely underground and ground connections are un- 
necessary, static dischargers are recommended. These consist of a number 
of gaps in series with very high resistances and are connected directly be- 
tween phases and adjusted to break down at slight increases over the line 
potentials. 




Fig. 18. Connections of Static Dischargers. 



AHRESTERS FOR HIGH POTENTIAL CIRCUITS. 993 



ARRESTERS lOK IB I C. II POlEXTI.il. CIRCUITS. 

(Abstract of paper by Percy H. Thomas in Franklin Inst. Journ.) 

A lightning discharge is of an oscillatory character and possesses the 
property of self-induction; it consequently passes with difficulty through 
coils of wire. Moreover, the frequency of oscillation of a lightning dis- 
charge being much greater than that of commercial alternating currents, a 
coil can readily be constructed which will offer a relatively high resistance 
to the passage of lightning and at the same time allow free passage to all 
ordinary electric currents. 

A more complete method, a method of prevention rather than resistance, 
which is available for higher voltages, is the use of the static interrupter, 
which is substantially a magnified choke coil. Its function is so to delay 
the static wave in its entry into the transformer coil that a considerable por- 
tion of the latter will become charged before the terminal will have reached 
full potential. 

If a very heavily insulated powerful choke coil be placed in the lead of 
the transformer, when a static wave approaches electricity will begin to 
pass in small quantity and will pass in gradually increasing quantity at 
later instants of time, so that the 
coil will be, comparatively speak- , 
ing, gradually brought t*> full po- 
tential; meanwhile the volume of 
the static wave is being reflected 
and choked back and perhaps being 
discharged to the ground if there 
be a lightning arrester near. It 
is evident that this choke coil, to 
be effective, must be so propor- 
tioned as to delay the incoming 
wave enough so that the portion 
of the winding which has become 



choke coil . 




CHOKE COIL 



Fig. 19. 



Static Interrupter Protecting 
Transformer. 

charged when full potential is reached at the terminal shall be sufficient to 
withstand the strain of the full voltage of the wave. It is evident that such 
adjustment does not depend directly on the frequency or abruptness of the 
static wave, since both the transformer and the choke coil are similarly 
affected by the frequency. 

But a choke coil sufficiently powerful to accomplish this result satisfac- 
torily is found to be impracticable on very high potential circuits on account 
of the size, cost and interference with the operation of the system. How- 
ever, if the arrangement of the static interrupter be used, that is, if a con- 
denser be connected between line 
C H0K . E . C 0IL line anc * ground behind the choke coil 

-'wnnnp 1 nearer the apparatus to be pro- 

1 LT ARR tected, this choke coil will absorb 
a considerable portion of the cur- 
rent actually passed by the choke 
coil, and the time required to pass 
sufficient electricity to charge the 
terminal will be much increased. 
With this arrangement a compara- 
tively small choke coil may be 
used. The condenser has a very 
small electro-static capacity, and 
has no appreciable effect upon 
normal operation, and yet has a 
very powerful effect on the static wave on account of its extremely high 
frequency. As in the case of the choke coil, the static interrupter must be 
roughly proportioned to the transformer winding to be protected. The 
condenser must also be suitable for the voltage between line and ground. 

If static interrupters be placed in each lead of high tension apparatus 
which may be injured by local concentration of potential, its windings will 
be amply protected against danger of short circuits from static wave either 
positive or negative. Such an arrangement is shown diagrammatically in 
connection with a transformer and a high tension generator in Figs. 3 and 4. 




CHOKE COIL umt 

Fig. 20. Static Interrupter Protect- 
ing High-tension Generator. 



994 



LIGHTNING ARRESTERS. 



Static Interrupters and Low Equivalent Lightning* Ar- 
resters. — A short description of the salient features of some actual 
lightning arresters and static interrupters will be given. 

The Low equivalent A. C Lightning* Arrester consists of a 
number of & inch air gaps between non-arcing 
metal cylinders in series with non-inductive resis- 
tance. A portion of the resistance, called shunt 
resistance, is shunted by a second set of air gaps 
called shunted gaps. The object of this arrange- 
ment is to reduce the amount of the series resis- 
tance through which the discharge must pass to 
ground. This arrester is diagrammatically illus- 
trated in Fig. 22. 

The series gaps withhold the line voltage and 
are chosen so as to break down at something 
between 50 per cent and 100 per cent rise of 
voltage above that of the earth. A portion of 
the series resistance is shunted by gaps so that 
the static discharge can pass around this portion, 
thus avoiding its resistance. It evidently is then 
necessary to suppress the arc from the generator 
which tends to follow through the shunted gaps. 
It is found that with a number of shunted gaps 
equal to the series gaps*the arc will be withdrawn 
from the shunted gaps by the shunt resistance 
when the shunt resistance does not exceed a 
proper value, which is a considerable portion of the 
total resistance in the arrester. _ A very marked 
gain in the reduction of the resistance offered to 
the discharge is therefore made by means of the 
use of shunted gaps and shunt resistance. It must 
be noted as well that no more voltage is required 
to cause a rise of potential to jump over all the 
series gaps and shunt than would be required to 
jump the series gaps alone, since on account of the shunt resistance the 
series and shunted gaps are broken down separately one after the other. 

A Static Interrupter consists of a choke coil in series with the line 
and a condenser connected between line and ground on the apparatus side 
of the choke coil. 

Cables. — The high tension electric cable is in principle no different from 
the electric air line, but has a different insulating material, paper or rubber 




Fig. 21. Choke Coil 
with Support, for Use 
with Low Equivalent 
Lightning Arrester. 



-SHUNTED GAPS- 



o o o o o o o o — o o o o o o o o \Z\AAHl' 



SHUNT RESISTANCE 

Fig. 22. Diagram of Low Equivalent Lightning Arrester. 



m place of air. This has the double effect of increasing its electrostatic 
capacity and changing the velocity at which waves progress. Ine in- 
creased electrostatic capacity tends to decrease the -peed, but as tne 
inductance of the cable is small this partially compensates tor the in- 
creased capacity. The differences from the air line are differences in degree 
only, and do not affect the passage of waves, reflection, resonance, etc. 
Consequently, no phenomena different from the air lines may be expectea 
as a result of static disturbances. 

Since the cable contains no coils of wire, no local concentration ot poten- 
tial will be found like that in transformer coils, and there is no oooasion tor 
the use of a static interrupter. 



ARRESTERS FOR HIGH POTENTIAL CIRCUITS. 995 

In a general way it must be expected that the surging about of the energy 
which is stored whenever a line is charged will cause increased potential at 
certain points. This should be provided for by placing suitable lightning 
arresters at all points where important and vulnerable apparatus is located. 
There will also be local concentration of potential in windings connected to 
the circuits as the result of all static disturbances. Such transformer or 
other coils should always be either sufficiently insulated or protected by 
choke coils or static interrupters or by some other suitable method. 

Horn Tvpe. — This arrester was invented by Oelschlaeger for the 
Siemens & Halske, A. G., and like the Thomson arc-circuit arrester, its 
operation is based on the fact that a short circuit once started at the base, 
the heat of the arc will cause it to travel upward until it ruptures by attenu- 
ation. On circuits of high voltage this rupture sometimes takes a second or 
two, but seems to act with but little disturbance of the line. It has been used 
little in this country until lately when it has been installed on a few of the 
high voltage lines on the Pacific coast, and the results are so far highly 
commendable. 

The following figures, Nos. 23 and 24, show the application, one as applied 
to the line, and the other in diagram. 

The knee-shaped horns are of No. 0000 copper wire, one connected directly 
to the line, the other through a water resistance and choke coil to the ground. 
The horns are mounted on the regular line insulators, and for 40,000 volts 
the distance between the knees varies from 2\ to 3 or 3| inches. The water 
receptacle should have a capacity of at least 15 gallons, and users differ as to 
whether the water should have salt added. The water should, however, 
be covered by a layer of oil about one-eighth inch deep in order to prevent 
evaporation. The choke coil can be made of about eighteen turns of iron 
wire wound on a 6-inch cylinder. 




Fig. 23. Construction of the Horn Type Arrester as used by the American 
River Electric Company. 



996 



LIGHTNING ARRESTERS. 



Care should be taken that the knee is not too sharp, or the arc is liable to 
reform after being once broken: again, the horns should not lie too flat, or 
the arc will strike down as shown in Fig. 24. The curve of the knee is not 
alike for all parts of the line, but depends on the line constants, and will 
have to be fitted to each case. 




TO MAIN LINE 



^6 INCHES 
GROUNDED ON 
PIPE LINE 



COPPER STRIP 
ONE INCH WIDE 



fc^r XZ 



6 TOO SMALL 
ARC HOLDS ON 



KNEE 

TOO SHARP 

ARC STRIKES 

BACK 



Fig. 24. Arrangement of the Parts of a Horn Type Lightning 
Arrester, the Two Small Diagrams to the Right Showing Faulty 
Construction of the Horns. — N. A. Eckert. 



ELECTRICITY METERS. 

Revised by H. W. Young. 

Meters for measuring the amount of electrical energy furnished to con- 
sumers are known as recording or integrating watt-hour meters and are 
made in several different forms to meet the varying conditions. The regis- 
tration of an integrating meter must be very accurate to meet commercial 
requirements owing to the fact that any errors which may be present are 
cumulative and even a small percentage error will, after a lapse of time, 
become relatively important from a pecuniary standpoint. The accuracy 
must be especially high at the lower end of the curve owing to the fact that 
for the larger part of the time the actual load is but a small percentage of 
the meter's capacity, and a meter which shows inaccuracy at this point 
cannot be a profitable investment for the central station for the reason that 
the tendency is to under register rather than over register. 

Action of Integrating* Meters. — The action and operation of an 
integrating meter may be likened to that of a small direct-connected motor 
generator set in which the current and potential coils are considered as the 
motor element and the disk and the permanent magnets as a magneto- 
generator with a short-circuited disk armature. The work expended by the 
motor is absorbed in driving the short-circuited generator and overcoming 
friction in the bearings and registering mechanism. In a perfect meter (or 
motor generator) all the work would be expended in driving the disk or 
generator — friction being absent — in which case a direct ratio would 
exist between the speed and the energy passing through the motor system, 
thus giving a meter absolutely accurate throughout its entire range. 

It is, however, impossible to entirely eliminate friction, but it will be seen 
that the more perfect the meter is, the greater will be the ratio between the 
work expended usefully in driving the disk or armature of the generator 
and that expended in overcoming friction; or, in other words, the "Ratio of 
Torque to Friction" in the meter will be high. Meter manufacturers, 
recognizing this essential feature, endeavor to make this ratio of torque to 
friction very high by efficient design of the measuring elements and reduc- 
tion of friction in the bearings and registering mechanism. 

Direct- Current Commutator Type Meters. 

The best known of the direct- current meters is the commutator type con- 
sisting of a small motor driving a registering mechanism. There are usually 
two series coils wound with comparatively few turns of heavy wire and prac- 
tically surrounding a pivoted armature containing several coils of fine wire 
suitably connected to a commutator on which bear small brushes. In 
series with the armature is a comparatively high resistance and a light load 
or friction compensating coil. The stationary series coils are connected in 
series with the load and the shunt circuit consisting of the armature and its 
resistance is connected across the line. 

The construction employed gives a driving torque proportional to the 
energy flowing in the circuit, and to secure correct registration it is necessary 
for a retarding torque to be provided which will be proportional to the 
driving torque. A controlling force varying directly with the speed is 
obtained by causing an aluminum or copper disk to pass between the poles 
of permanent magnets whose fields induce "Foucault" or eddy currents in 
the disk. The interaction between the fields of these eddy currents and the 
field of the permanent magnets produces a retarding torque varying directly 
with the disk speed. With such an arrangement of driving and retarding 
torques a rotation is produced which is always proportional in speed to the 
driving torque and, therefore, to the energy passing through the measuring 
coils. As tne measuring elements do not employ iron and are practically 
non-inductive, the meters can be used on either A. C. or D. C. circuits. 

997 



998 



ELECTRICITY METERS. 



Thomson Recording: Wattmeters. 

(General Electric Company.) 

These meters (Fig. 1) are of the commutator type previously described, 
and the salient features claimed are as follows: High torque, direct-reading 
registers, dust proof construction, small size commutator, gravity brushes, 

adjustable shunt field coil, inter- 
changeable on D. C. and A. C, 
high accuracy, heavy overload 
capacity, jewel bearings. 

Bearing's. — The top bear- 
ing consists of a simple brass 
plug having a hole of sufficient 
size to allow free rotation of the 
armature shaft. 

The lower bearing consists of 
a hardened steel pivot made of 
piano wire and resting on a 
spring supported sapphire or 
diamond jewel. This insures 
a bearing having a low friction 
value and long life. During 
shipment the jewels are pro- 
tected by a special armature 
locking device which, when the 
jewel is backed away from the 
pivot, automatically locks the 
moving element. 

Westing-house 1>. C 
Integrating: JVEeters. 

These meters (Fig. 2) are of 
the same general type as the 
Thomson, but differ in me- 
chanical construction. The sa- 
lient features claimed are prac- 
tically identical with those of 
the Thomson meter. 

The lower bearing is. how- 
ever, of an entirely different 
type, consisting of a small, 
highly polished steel ball rest- 
ing between two sapphire jew- 
els, one of which is secured in a removable jewel screw. The idea of this 
form of bearing is to present constantly changing contacts between the ball 
and its jewels owing to the attendant rolling action, thus securing a long 
useful jewel life and increased accuracy. During shipment the disk is 
locked Lin position by a suitable locking device operated from the top 
bearing. 




Fig. 1. Thomson Recording Wattmeter 
(Cover Removed). 



Duncan Uleters. 

This meter (Fig. 3) in common with the Thomson and Westinghouse 
forms, is of the commutator type and practically the same claims are made 
as for the other forms. 

It differs in the method in the friction or light load compensation in that 
the auxiliary field coil is provided with taps brought out to a multi-point 
switch. This arrangement enables the auxiliary torque to be varied by 
cutting in or out one or more coil sections. 

The lower bearing is of the "visual" type designed to permit inspection 
of the jewel and pivot while the meter is in operation. The pivot is of 
hardened steel piano wire and is securely held in position. ( During trans- 
portation the jewel post is lowered, thus locking the disk in position. 



WESTINGHOUSE D. C. INTEGRATING WATTMETER. 999 



Induction Type Alternating* Current Integrating* 
Wattmeters. 

Principle of Operation. — The single-phase induction wattmeter is 
in principle and operation analogous to a single-phase induction motor having 
a stationary shunt and series winding so related and located as to produce a 
rotating field acting upon a closed rotable secondary. In the induction meter 
the secondary consists of a light aluminum disk. The shunt winding, con- 
sisting of a large number of turns of fine wire wound on a laminated iron 
core, is highly inductive and its current lags approximately 90 degrees 
behind the impressed or line voltage. The series winding consisting of but 




Fig. 2. 



Westinghouse D. C. Integrating Wattmeter 
(Cover Removed). 



a few turns of comparatively heavy wire, has low self induction, and on non- 
inductive load (such as incandescent lamps alone) the current producing the 
series magnetic field will be in phase with the impressed or line voltage. 
Thus the magnetic field produced by the shunt winding will lag approxi- 
mately 90 degrees behind that of the series winding on a non-inductive 
load. 

With this relation of the two fields at the instant of time when the current 
in the series coil is greatest the current in the shunt coil is the least. (If it 
were not for the iron loss and small resistance or copper loss in the shunt 
circuit, the angle would be exactly 90 degrees.) During a portion of each 
alternation of the circuit the series coil helps the flux of one pole of the shunt 
field, opposing the other, and during another portion of the alternation it 
haa the opposite effect; these reactions being combined in such a way as to 



1000 



ELECTRICITY METERS. 



give a general shifting of the lines of force in one direction — that is, pro- 
ducing a rotating field. 

Rotating* field. — That the shunt and series fields combine to form a 
rotating field may be more clearly understood by tracing the action or 
relation of these two fields for a complete cycle by one-quarter periods of 
the same. 

Referring to Fig. 4 and noting that the two poles of the shunt coil magnet 
are designated by the letters A — Ai and C, and the poles of the series coil 
magnet by B — D, a clear statement of the relation of the fields by one- 
quarter periods is given in the table shown in Fig. 5. 

The signs given in this table represent the instantaneous magnetic values 

of the poles indicated, and it 
will be observed that both 
the positive and negative 
signs move constantly to the 
left indicating a shifting of 
the field in this direction, the 
process being repeated during 
each cycle. 

Driving* Xorque. — This 
continuous motion of the 
field induces eddy currents 
in the aluminum disk which 
react to produce rotation in 
the same manner as in the 
rotor of an induction motor. 
The rotary field being a 
combination of the series and 
shunt fields, the torque on 
the moving element or disk 
will be directly proportional 
to the energy flowing in the 
circuit. 

Retarding* Torque. — 
With a driving torque propor- 
tional to the energy flowing in 
the circuit it is necessary, in 
order to obtain steady rota- 
tion, for a retarding torque to 
be provided which will be 
proportional to the driving 
torque. A controlling force 
varying directly with the 
speed is obtained by causing 
the aluminum disk to pass be- 
tween the poles of two perma- 
nent magnets whose fields 
induce "Foucault" or eddy 
currents in the disk. The interaction between the fields of these eddy 
currents and the fields of the permanent magnets produces a retarding torque 
varying directly with the speed of the disk. With such an arrangement of 
driving and retarding torque a rotation is produced which is always pro- 
portional in speed to the driving torque and therefore to the energy passing 
through the operating coils. 

Wattmeters on Inductive Circuits. — Assuming that the current 
producing the shunt field lags exactly 90 degrees behind the line voltage and 
neglecting for the moment the iron loss and resistance loss in the circuit, it 
will be seen that when the load is non-inductive (such as offered by incan- 
descent lamps) the current of the series coil will be in phase with the line 
voltage and the shunt and series fields will differ in phase by exactly 90 
degrees. From the table (Fig. 5) it will be seen that this gives a maximum 
pull on the disk. 

If, however, the load is purely inductive having zero power factor, the 
current in the series coil will lag 90 degrees behind the line voltage and will 
be in phase with the current in the shunt coil. Under these conditions the 
relation between the fields for each one-quarter period of a complete cycle 
is shown in the table on page 1002. 




Fig. 3. Duncan D. C. Recording Watt- 
meter (Cover Removed). 



INTEGRATING WATTMETERS. 



1001 



Scries Element 



O „ C 



L® 



^B 



O 

/ 

/ 

i 



O^- 







-"'O x 



Shunt Element 
Fig. 4. 



— -'O 



Start 


A 

+ 


B 



c 


D 



>i Period 





- 







!4 Period 


- 










^ Period 










- 


Full Period 







- 







5 


I 


I 


I 




Fig. 5. Table Giving Relation of Fields by One-quarter Periods. 



1002 



ELECTRICITY METERS. 



At start . . 
At i period . 
At h period . 
At I period . 
At full period 



When A is 



+ 






+ 



B is 



4- 






+ 



Cis 


Dis 








+ 


+ 













A x is 



+ 




As no progression or shifting of the field occurs, there is no rotation of the 
disk and thus the meter will not record when the current in both the series 
and shunt coils is 90 degrees out of phase with the impressed voltage; hence, 
the meter will record true power whether the load be inductive or non-inductive. 
Power Factor Compensation. In the preceding diagrams it was 
demonstrated that for correct registration on any power factor, exactly 90 per 
cent phase relation between the shunt and series fields must be obtained. 
Consequently, compensation must be made for the small decrease of this 
angle caused by the copper and iron losses in the shunt circuit. 

This compensation is usually obtained by placing one or more short cir- 
cuited turns (or secondary) of conducting material around the projecting 
pole C of the shunt electromagnet, producing an induced magnetic field 
which, acting with the shunt magnetic field, produces a resultant field 
lagging behind the field of the series coil. By varying the position or resist- 
ance of this short-circuited turn (or secondary) the compensation necessary 
to obtain the exact 90 degrees phase relation may be obtained. This method 
of securing the resultant field can be better under- 
stood by referring to Fig. 6 in which: 

OA represents the voltage of shunt coils. 
OY represents current passing through shunt 
coils. 

YOA represents angle less than 90 degrees due 
to iron and copper losses in shunt coils. 

OS represents induced voltage of short-circuited 
turn K and exactly opposite in phase relation to 
that of OA, but very small in value; the current 
passing through the short-circuited turn K being 
in phase equal and approximate to OC. 

This current OC and main current OY have 
a combined magnetizing effect on the iron core, 
which effect is found by forming the parallelo- 
gram OC — XY when OX is the resultant effect 
now practically at right angles to the impressed E.M.F. of the circuit. By 
raising or lowering, thus changing the position of the short-circuited turn, 
the magnetism of the shunt field can be shifted back to the proper angle, 
giving the 90 degree phase relation and adjusting the meter so as to read 
correctly under all conditions of power factor. 

Note. — This power factor compensation holds true only for approxi- 
mately the frequency for which the meter is adjusted and if highest accuracy 
is expected, wattmeters should not be used on inductive loads having a 
frequency variation from normal of more than 10 per cent plus or minus. 

minimizing* Effect of Voltagre Variations. — It is desirable that 
induction meters be capable of operating over a wide voltage variation without 
impairment of accuracy, and freedom from error due to voltage variations 
is accomplished by the design of the shunt magnetic circuit. By referring 
to Fig. 4 it will be seen that the shunt magnetic circuit is so arranged that 
the greater portion of the magnetic lines generated by the shunt winding 
are shunted across the narrow air gaps FF and do not pass through the disk, 
thus cutting or damping its action and thereby impairing the accuracy. 
While the exact leakage across the gaps cannot be accurately determined, 
it is a large proportion of the total flux generated so that a comparatively 
wide variation from the normal voltage has practically no effect on the 
meter's registration owing to the small percentage of damping flux which 
is produced. 




Fig. 6. Diagram of Re- 
sultant Field. 



"WESTINGHOUSE INDUCTION WATTMETERS. 



1003 



Figure 7 illustrates a typical voltage curve of an induction wattmeter. 
It will be noted that a voltage range from 50 per cent to 125 per cent of 
normal voltage does not materially impair the accuracy. 

Westing-house Single-Phase Induction Wattmeters. 

These meters (Fig. 8) are of the rotating field type previously described 
and the salient features claimed are as follows: High ratio of torque to 











































































1 




































































K 




































































DC 

I7 


00 




















vc 


LT/ 


G£ 


CO 


^VE 


AT 


CONSTANT LOAD AND 


FREQU 


ENCY 
















3 




































































en 










































































20 






40 






60 






80 






100 






120 






140 






























1 






voLts 



























Fig. 7. 

friction; high ratio of torque to weight; improved lower rolling ball 
bearing; improved self oiling top bearing; light load adjustment located in 
leakage gap of shunt coil and unaffected by flux of series coil; mechanical 
power factor and frequency adjustment; accurate on non-inductive or 
inductive loads; freedom from effect of stray fields; permanent magnets 
magnetically shielded; light rotating element (15 grammes); unaffected 
by voltage variation from 50 per cent to 125 per cent of normal; unaffected 
by wide variations in wave form and frequency; freedom from rattling or 




Fig. 8. Type "C," Westinghouse Single-Phase Induction Meter 



humming; dust proof; light running, gold plated, non-corrosive registering 
mechanism; meters shipped ready for installation without preliminary 
adjustment. 

Westing-house Polyphase Induction Wattmeters. 

These meters consist of two single-phase elements which are mounted in 
ft single case and actuate a common registering mechanism. 



1004 



ELECTRICITY METERS. 



Figure 9 illustrates a House Service Polyphase Meter and Figure 10 the 
Polyphase Switchboard Service Meter. 




POLYPHASE 
INTEGRATING WATTMETER. 

WESTINGHOUSE 

ELECTRIC 8c MFG. CO. 
PITTSBURG, PA., U S.A. 




Fig. 9. Westinghouse Polyphase Induction Meter (House Service). 




Fig. 10. Westinghouse Polyphase Induction Meter 
(Switchboard Service). 



SINGLE-PHASE INDUCTION WATTMETERS. 



1005 



Thomson High Torque, ft ingle -Phase Induction 
Wattmeters. 

(General Electric Co.) 

These meters (Fig. 11) are of the 
same general type as the Westing- 
house, but differ in mechanical con- 
struction. The salient features claimed 
are practically identical with those of 
the Westinghouse meters. 

The bearings, however, are of a 
different type, being of the same con- 
struction as employed in the Thomson 
D. C. meter. The torque is of high 
value, thus giving a high ratio of 
torque to weight. During shipment 
the armature is locked in position in 
a manner similar to that of the Thom- 
son D. C. meter. 



Thomson Polyphase Induc- 
tion Wattmeters. ((Q) 




These meters (Fig. 12) in common 
with the Westinghouse form, consist 
of two single-phase elements in a sin- 
gle case. 



Fig. 11. Thomson High Torque 
Single-Phase Induction Meter 
(Cover Removed). 




Fig. 12. Thomson Polyphase Meter, Glass Cover. 

Type " K " Single-Phase Induction Wattmeters. 

(Fort Wayne Electric Co.) 

These meters (Fig. 13) are also of the rotating field type, but employ a 
drum-shaped rotor instead of a disk. The light load adjustment is affected 



1006 



ELECTRICITY METERS. 



by an adjustable starting coil which 
can be shifted to give the necessary 
compensation for friction effect at light 
loads. The salient features claimed are 
practically identical with those of the 
Westinghouse and Thomson meters. 

The upper and lower bearings are simi- 
lar to those employed in the Thomson 
meter. 

Type "K" Polyphase Induc- 
tion Wattmeter*. 

These meters (Fig. 14) consist of 
two single-phase measuring elements 
mounted in a single case and acting upon 
a single drum-shaped rotor. 

Hang'amo I>. C Integrating* 
Meter. 

This meter (Fig. 15) is a mercury con- 
tact motor meter of a type that has 
been used to a greater extent abroad 
than in this country. 

In common with all motor type inte- 
grating meters the Sangamo contains the 
three necessary elements, namely, a mo- 
tor producing a driving torque; a gen- 
erator providing a load or drag varying 
with the speed, and a registering mech- 
anism arranged to integrate the instantaneous values of the electrical 
energy passing through the measuring coils. 




Fig. 13. Type " K " Meter 

(Cover Removed). Fort 

Wayne Elec. Co. 




Fie. 14. Type "K" Form MAB Wattmeter — Half Front View, Case off. 
Fort Wayne Elec. Co. • 



SANGAMO D. C. INTEGRATING METER. 



1007 



Principle of Operation. — The principle of operation maybe under- 
stood by referring to Fig. 16, and the following description: A — A are 
the poles of an electromagnet energized by the potential coil which, through 
a resistance, is connected directly across 
the line, thus forming the voltage element 
of the meter. E is a soft iron bar located 
just above A — A and forming the air gaps 
in which the copper disk D is located. 
This copper disk is connected in series with 
the line and forms the current element of 
the meter. In capacities exceeding 10 am- 
peres the disk only carries a certain por- 
tion of the main current which is obtained 
by inserting a shunt in series with the 
line and allowing but a small portion to 
pass through the mercury and disk. These & 
voltage and current elements form the 
driving motor element of the meter. 

B is an aluminum disk so arranged that 
its edges pass between the poles of two per- 
manent magnets, F — F thus forming the 
generator or load element of the meter. 
D and B are mounted on a common shaft 
which is suitably pivoted or suspended. 

The third element of the meter, namely, 
the registering mechanism, is not shown, 
but, in common with other forms of motor 
meters, is driven by a suitable gearing 
actuated by the rotable shaft. 




Fig. 15. Sangamo Direct-Cur- 
rent Meter, Case off. 



0* 







Fig. 16. 



Elementary Diagram of Sang-amo I>. C. meter. 

From the arrows on A — A it will be seen that the field generated by the 
potential coil threads the two air gaps and in doing so cuts or passes through 
the copper disk D. The disk D being in series with the load is, therefore, 
carrying a current which, due to the position of the leading in contacts, 
passes across the magnetic fields produced by the magnet poles A — A and 



1008 



ELECTRICITY METERS. 



is at right angles to this field. As is well known, a conductor free to move 
and carrying a current whose direction of flow is at right angles to a fixed 
field will tend to move out of the fixed field. 

As the disk moves from its initial position the current enters at a new 
point on the periphery of the disk which is again impelled forward, and this 
constant change in point of current entrance to the disk produces a con- 
tinuous rotation. It will thus be seen that the meter, in common with the 
Westinghouse D. C. meters, operates as a simple motor driving a magneto- 
generator having a short circuited armature. 

The Sangamo meter differs, however, in its construction from that em- 
ployed in the commutator D. C. meters in that the voltage element is station- 
ary rather than rotable; the current element being rotable rather than 
stationary and instead of employing a commutator and brushes to lead 
current in and out of the rotable element, or armature, it is submerged in 
mercury contained in an insulating chamber having contact pieces at each 
edge to which the circuit connections are made. 

Figure 15 illustrates a meter as actually constructed. The mercury is 
contained in a dome-shaped chamber and not only serves to conduct the 
current to and from the armature, but also tends to buoy up the disk and 
relieve the pressure on the lower bearing. 

The full load adjustments are accomplished by varying the strength of 
the magnetic field through which the disk passes, and the adjustment at 
light load is accomplished by a compounding coil so located as to assist the 
field generated by the potential coil. 

Sang-amo A. C Meter. 

This meter has the same general appearance and operates upon the same 
principle as the D. C. meter, but differs somewhat in the arrangement of the 
measuring elements. In the A. C. meter the main current energizes the 
stationary electromagnet and the shunted or potential current passes through 
the copper disk. Compensation is provided for light load and inductive load. 

WRIGHT DISCOUNT MIIXKH. 

This instrument is for use in connection with a watt hour meter for de- 
terming the maximum use of current during any given period ; or may be 
used without the watt-hour meter in connection with any electrical device 
for which it is desired to know the maximum use of current, either direct or 
alternating. 

It is slow acting so as to take no account of momentary spurts, such as 
starting an elevator or street car, and is rated to record as follows : 

If the maximum load lasts 5 minutes, 80 % will register ; 
If the maximum load lasts 10 minutes, 95 % will register ; 
If the maximum load lasts 30 minutes, 100 % will register. 



The following figure shows the working parts in theory, which, being of 
glass and liquid, are placed in a cast-iron case, with a glass front to permit 
reading. As shown, one leg of the circuit passes around a glass bulb which 
is hermetically sealed, and connected to a glass tube holding a suitable 
liquid. 



rr hw 



T, Terminals. 
h w, House wires. 
r w, Resistance wire. 
H B, Heated bulb. 



CW) ff>* A B > Air BulT) * 

HB j^\ \ it, Indicating 



tube. 



L, Liquid. 

> Direction. 



Wright Discount Meter. 



METEK BEAMNGS. 



100S 



The heat due to the current passing in the circuit expands the air in the 
bulb, which forces the liquid down in the left column and up in the right. 
Should the quantity of heat be such as to force some of the liquid high enough, 
it will fall over into the central tube, where it must stay until the instru- 
ment is readjusted. The scale back of the central tube is calibrated in am- 
peres on the left and in watts on the right. After reading and recording 
the indication for any period of time, the liquid is returned to the outer 
tubes by simply tipping up the tubes, etc., which are hinged at the top 
connections for the purpose. 

The readings of the demand meter or discount meter, either of which names 
are used, together with those of the watt-hour recording meter, furnish a 
basis for a more rational system of charging for electricity than has been 
customary. This, subject is being taken up by many of the larger electricity 
supply companies. 

The instrument is handy to use in circuit with a transformer to show how 
the maximum demand compares with the transformer capacity ; also on 
feeders and mains to show how heavily they may be loaded. 




Fig. 17. Visual Pivot Type 
Bearing. 



Fig. 18. Pivot Type Bearing. 



WEETER BEARI]¥G§. II EG LITERS A \ I> COIHE- 
MUlAIOR§, 



Two forms of lower bearings are in general use in both direct and alter- 
nating-current meters. Figs. 17 and 18 represent the pivot forms consisting 
of a hardened and highly polished steel pivot resting on a cupped sapphire, 
or on a rings tone end-stone or cupped diamond jewel. 

Figure 19 is a rolling type ball bearing formed by a small hardened and 
polished steel ball resting between two jewels, one of which is attached to 



1010 



ELECTRICITY METERS. 



DISCS OF BILLIARD CLOTH 
SOAKED IN JEWELER8 OIL 



the armature shaft and the other to a 
fixed support. By this construction a 
rolling action is secured as contrasted 
to the rubbing action of the pivot 
bearing. 

Both types of bearings are exten- 
sively employed by meter manufactur- 
ers and each has strong advocates. 
The pivot form of bearing is invariably 
supported by a spring suspension, while 
with the ball bearing the spring is only 
resorted to in the direct-current meter? 
having comparatively heavy moving 
elements. 

The registering mechanisms of the 
various types of meters are quite simi- 
lar in appearance, differing principally 
in the method of construction. Fig. 
20 illustrates a typical form of register- 
ing mechanism employed in both D. C. 
and A. C. meters. 

- To reduce the variable nature of the 
contact surfaces of the commutator 
and brushes it is customary to em- 
ploy non-oxidizing metal in the con- 
struction of these elements, thus reduc- 
ing to a minimum changes at this point. Fig. 21 illustrates the damping 
disk, armature and commutator mounted on the rotable shaft. 



JEWEL SCREW 




.CLAMPING NUT 



Fig. 19. Rolling Type Ball Bearing. 



Hie Prepayment 
Wattmeter. 

The prepayment idea for 
the purchase of practically all 
forms of commodities is rap- 
idly growing, for the vending 
of practically all forms of com- 
modities, and is now receiving 
recognition in the electrical 
field. Like the installment 
plan of payments, the prepay- 
ment meter appeals to a class 
of people who are accus- 




Registering Mechanism. 



tomed to receive and spend their money in small quan- 
tities. The success of gas companies has been greatly 
aided and furthered by the prepayment meter, and its 
use in the electrical field should prove as great a suc- 
cess as it has proven in this field. 

Prepayment meters are especially applicable in sup- 
plying energy to customers whose total consumption is 
relatively small and the collection of whose bills is a 
very considerable proportion of the total revenue de- 
rived. Their use reduces the amount of bookkeeping 
and unavoidable monetary loss due to poor accounts, 
for the service is such that before securing light it is 
necessary that payment be made. This system, there- 
fore, automatically collects its own bills, registers the 
actual consumption, and when the energy prepaid for 
is consumed, automatically disconnects the service. 
In installations such as flats, dormitories, barber shops, 
cafe's, saloons, boot-blacking establishments, cigar 
stands, rented nouses, or in any other installations where 
Fig. 21. Rotating the volume of energy consumed is necessarily small, 
Element of D. C. the prepayment meter will be found extremely useful. 
Commutating Type Central stations supplying towns having a large "float- 
Meter, ing" population, such as seashore resorts or college 




THE PREPAYMENT WATTMETER. 



1011 



towns, where the rapid shifting of population renders difficult the following 
of accounts, will find the prepayment meters extremely useful. 

Another use for the prepayment meter is in the collection of old accounts. 
Central stations frequently have a considerable number of customers who 
are usually backward in payments, although they ultimately pay their 
bills. One method of forcing such customers to pay back bills is to threaten 
discontinuance of service, but this method is only resorted to as an extreme 
measure, owing to the resulting unpleasantness and very possible loss of a 
customer. On the other hand, a central station cannot afford to have its 
legitimate revenue tied up even with customers who will ultimately pay. 

An effective way to collect these old bills, and at the same time continue 
the service, might be to install a prepayment meter adjusted for a "higher 
rate per kw.-hour than the regular rate. For instance, assuming the normal 
rate to be 10 cents per kw.-hour, the meter may be set at 15 cents per kw.- 
hour, so that the customer not only pays for the energy being consumed, 
but also gradually pays up the old bill on the installment plan. The 
majority of customers would undoubtedly prefer this method of paying up 





Fig. 



22. General Electric Prepay- 
ment Wattmeter. 



Fig. 23. General Electric Prepay- 
ment Wattmeter (Internal View). 



old bills to being forced by threats of discontinuance of service. After the 
account has been settled, the meter can be reset for the normal rate per 
kw.-hour. 

At the present time many central stations are unable to connect a con- 
siderable number of relatively small consumers, owing to the fact that the 
amount of energy used by each customer would be so small as to hardly 
justify the collection and accounting expense, which would be a very con- 
siderable percentage of the total receipts. For example, many station 
managers would hesitate to connect up consumers whose bills would prob- 
ably not average over $1 per month, and, furthermore, these consumers do 
not understand and will not agree to a fixed minimum charge. However, 
assuming that the total revenue from such a consumer would average $12 
per year, and assuming the cost of generation and distribution is one-half 
the gross receipts, it would leave a remainder or profit of $6, less the interest, 
collection and maintenance cost. While the gross profit would not be very 
large, yet the percentage is very satisfactory, and there is the additional 
advantage that a large majority of these new customers would gradually 
use larger amounts of energy and in time come within the class of desirable 
customers. 

The use of electricity increases with the knowledge of its advantages, and 



1012 



ELECTRICITY METERS. 



there is no better way of introducing its use especially with the smaller 
customers, than with the prepayment meter. 

With the prepayment meter, differential rates can easily be made, owing 
to the fact that the rate per kw.-hour is not 
shown on the meter bills and the central station 
may, therefore, place meters adjusted for dif- 
ferent rates to meet the various conditions 
which arise; for instance, a long-hour consu- 
mer could be supplied through a meter adjusted 
at a lower rate than the short-hour consumer. 
This method of differential rates, though not 
in general use, is feasible for the reason that 
with a prepayment meter consumers feel they 
are purchasing light and not kw. -hours. 

Another use for the prepayment meter is in 
connection with electric cooking and heating 
appliances, which frequently are supplied with 
energy from a separate circuit at a different rate 
than is charged for lighting. These appliances 
may be supplied through a prepayment meter, 
and this system has the additional advantage 
of permitting the consumer to determine ac- 
curately just what the electric cooking or heat- 
ing outfit is costing for the results obtained. 

By prepaying the meter for a definite amount 
it can be used as a time switch to automatically 
turn off arc lamps, electric signs and store win- 
dow lighting. 

The construction of several forms of commer- 
Fig. 24. Prepayment At- cial prepayment meters is shown in the ac- 
taehment for General companying illustrations. Essentially the pre- 
Electric and Fort Wayne payment meter consists of a measuring element 
Wattmeters. used in conjunction with a special register, au- 

tomatic switching device and coin chute. Fig. 
24 illustrates a separate attachment which can be used in conjunction 
with a specially arranged standard meter and located apart from the meter 
itself. 






Fio. 25. Fort Wayne Prepay- 
ment Wattmeter. 



Fig. 26. Westinghouse Prepay- 
ment Wattmeter. 



INTEGRATING WATTMETER TESTING. 



1013 



INTEGRATING WATTMETER TESTING. 

It is quite generally recognized that integrating wattmeters can only 
be maintained in an accurate and efficient condition by comparing them at 
certain intervals with known standards, and it is obvious that the standards 
for this purpose should be highly accurate. To avoid a multiplicity of 
instruments they should have a wide operating range 
which may be obtained primarily by a long scale, 
and where possible the range should be further in- 
creased by combining several current and potential 
capacities in one meter. To combine laboratory 
accuracy with the speed necessary in commercial 
work, two sets of standards should be provided 
which may be designated as "primary" standards 
for extreme accuracy and "secondary" or working 
standards for use directly with the service meters. 

Checking* of Secondary Standards. — All 
secondary standards should be frequently checked 
with the primary standards, the frequency of such 
checking varying largely with local conditions. As a 
rule, however, it is advisable to check the secondary 
standards at least once a month, especially when 
such standards consist of indicating meters, owing 
to the fact that all portable indicating meters are 
more or less delicate and the rough usage attendant 
on commercial testing is liable to materially change 
the calibration. 

To compare the calibration of a secondary stan- 
dard indicating wattmeter with the primary stan- 
dard, it should be connected into the circuit as 
shown in Fig. 28, having the current coils of the 
meters in series and the shunt coils in multiple 
with each other. Care should be taken to have the 
shunt coil of each meter connected to the same 
point or source of potential to avoid the possibility 
of one meter measuring the shunt loss of the other. 

Testing* Load. — The load for the test can readily be obtained by a 
bank of incandescent lamps so arranged that any value from zero to full -load 
current may be easily and quickly obtained. The load should be taken 
from a source of supply having as little voltage variation as possible on 
account of the effect of rapid fluctuations on the reading of indicating 




Fig. 27. Westing- 
house Prepayment 
Wattmeter t (Inter- 
nal View). 



LOAD 




PRIMARY 'SECONDARY 

STANDARD STANDARD 



RESISTANCE 
OOOOO 



Ooo=ooO 




LINE 



Fig. 28. Connections for Comparing Secondary with Primary Standard. 



1014 



ELECTRICITY METERS. 



meters, it being somewhat difficult to secure accurate readings on a circuit 
having a badly fluctuating voltage. A convenient arrangement of load 
is shown in Fig. 29, and consists of a bank of lamps of different candle- 
power ranging from 4 to 50 C.P., these lamps being arranged in connection 
with single-pole, single-throw switches so that the smaller sizes may be 
thrown in circuit individually and the larger sizes in groups. The arrange- 
ment shown may, of course, be varied to suit local conditions. 

In circuit with a portion of the lamp bank is placed an adjustable re- 
sistance or rheostat for use in obtaining exact current values and also to 
assist in maintaining a constant load. The water rheostat is very con- 
venient for this class of work as the load can be varied quickly and with 
perfect uniformity. The resistance of the water rheostat can be readily 
changed to almost any value by changing the strength of the solution. 
Having made connections as above, it is now only necessary to take the 
readings on the portable meter at convenient points and to compare these 



LAMP BANK 




SINGLE POLEV //•///// 
SWITCHES -^ l I I 1 I I I I- 



ADJUSTABLE 
RESISTANCE^ 



*— i PRIMARY SECOND- 

STANDARD STANDARD 





RESISTANCE 



OQOOQ 




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Fig, 



29. Lamp Bank and Connections for Comparing 
Secondary with Primary Standards. 



readings with the true values as given on the primary standard. It is 
considered good practice to check the portable meter at each of the marked 
points on the scale, simply estimating the error of the intermediate points, 
thus showing the error very closely at all points of the scale. 

Checking* Calibration of Portable Standard Integrating 
Wattmeter. — If the portable rotating standard meter is used as a second- 
ary standard, it should be checked with a primary standard wattmeter from 
time to time and for this purpose should be connected in the same manner 
as the indicating standard shown in Fig. 28. To make a comparison of 
the rotating standard with the primary standard it should be properly 
connected and placed in series with a primary standard of approximately 
the same ampere capacity. 

liig-ht Load Test. — The load should now be maintained constant at 
approximately 4 per cent of full load and the pointer revolutions of the 
rotating standard timed by a stop watch. Having obtained the time con- 



INTEGRATING WATTMETER TESTING. 1015 

»umed in making a certain number of pointer revolutions, the watts should 
be computed by the formula applying to the particular meter under test. 

Ifull-JLoart Test. — The meter may be tested on other loads ranging 
from the light load to full load, but as the calibration curve of the rotating 
standard from light load to full load is practically a straight line, it is unnec- 
essary to take readings at other points than light and full load unless 
extreme accuracy is required. If this is desired, readings may be taken at 
several intermediate points, from which readings a curve may be plotted 
giving the exact calibration of the meter at all points. 

Selection of ^Primary Standard meter Capacity. — In com- 
paring secondary with primary standards, care should be taken to select the 
windings of the primary meter having a capacity nearest that of the meter 
under test, in order that it may be used at the highest possible part of the scale. 
This rule also applies to the comparison of service meters with secondary 
standards. 

Testing; Service Ifleters. — For the testing of service meters, either 
the "portable indicating" meters may be employed in conjunction with a stop 
watch and the reading computed by the use of a calibrating formula, or the 
meter may be compared with a portable standard integrating wattmeter. 
To use either of these methods the standard should be connected in circuit 
with the service meter as shown in the diagrams usually accompanying 
each meter. 

Where meters operating from series and voltage transformers are to be 
tested, it will usually be found advisable to test them as 5-ampere, 100- 
volt meters without using the transformers. If such meters are to be 
tested under the running load, the standard may be connected in the 
secondary transformer circuit of the meter under test, using the 5-ampere, 
100-volt coils of the standard. 

Testing* Service HEeters with Standard Indicating* Meters.— 
To conduct a test with the indicating meter it will be necessary to hold the 
load as constant as possible and while noting the reading of the standard, 
count the revolutions of the disk of the meter under test, taking the time 
by means of a stop watch. To eliminate personal errors several readings 
of at least one minute each should be taken and averaged. To compare the 
reading of the meter with the standard, it is necessary to use a formula 
pertaining to the particular meter under test. 

"Use of Stop Watch. — When employing the indicating wattmeter 
method it should be remembered that the stop watch is not infallible and 
should be frequently checked by comparing it with the second hand of a 
good clock. For this purpose a clock in which the pendulum beats seconds 
or half seconds should be used, starting the watch with a certain beat of 
the pendulum and having allowed the watch to run several minutes to elim- 
inate personal errors, it should be stopped on the same beat of the pendulum 
on which It was sorted. A little practice will enable the operator to check 
the watch within .1 of a second without difficulty. 

Testing- Service Meters with Portable Standard Inte- 
grating' Wattmeters. — If the integrating standard is used for testing 
single-phase service meters, the operation is much simplified, as the use of the 
formula and stop watch can be eliminated. To conduct a test by this 
metnod, the standard should be connected as shown in Fig. 30, and the 
connections so arranged, if possible, that the capacity of the standard will 
be the same as that of the meter under test. The proper connections 
having been made, the load should be adjusted to the desired value and a 
direct comparison made of the number of revolutions of the meter under 
test with the number of revolutions shown on the counter of the standard. 
In common with the indicating standard method, readings should be taken 
for at least one minute to eliminate personal errors. The percentage of error 
in the meter under test may be found directly by dividing the number of 
revolutions of the service meter by the number of revolutions made by the 
standard meter ; that Is, if the meter under test makes 10 revolutions while 
the standard meter shows 10.4 revolutions, the ratio would show the meter 
under test to be approximately 4 per cent slow. The above applies only 
when the meter under test has the same ful'-ioad speed as the standard. 

In order that the standard meter may be conveniently employed in 
testing meters in which the full-load speed is other than twenty-five revo- 
lutions per minute, the following table has been prepared as applying to 
Westinghouse, General Electric and Fort Wayne meters. By the use of 



1016 



ELECTRICITY METERS. 









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INTEGRATING WATTMETER TESTING. 



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9 B 



1018 



ELECTRICITY METERS. 



this table any one of the three makes can easily be tested with the one 
standard. 

In explanation of the use of this table the following examples are given: 

(1) If it is desired to test a Westinghouse service meter by using the 
rotating standard, the two meters should be connected in series and loaded 
so as to give one revolution of the disk in approximately one minute's time 
for a light-load test, and for full load, twenty-five revolutions of the disk in 
the same time. The number of revolutions made for these two loads by 
the standard — if the service meter is correct — would be one and twenty- 
five respectively. If the number of revolutions made by the standard is 
25.77 the service meter is three per cent slow at full load.^ If the number 
of revolutions of the standard is 24.27, the service meter is three per cent 
fast at full load. From this example it will be seen that the accuracy can 
be determined for any speed within six per cent fast or slow, reading same 
directly from the table without any calculation whatever. 

(2) If it is desired to test a five-ampere General Electric meter the load 
can be adjusted to give say — two revolutions at light load and thirty 
revolutions of the disk at heavy load in approximately one minute's time. 
If the meter is correct the standard will show 1 .8 and 27 revolutions respec- 
tively. If the standard shows 1 .85, the service meter is three per cent slow 



LOAD 



PORTABLE 
STANDARD 
INTEGRATING 
WATTMETER 



LINE 




Fig. 30. Connections for Checking Service Meter with Portable 
Standard Integrating Wattmeter. 

at light load. If the standard shows 1.75 the service meter is three per 
cent fast at light load. 

(3) It it is desired to test a five-ampere Fort Wayne meter the load can 
be adjusted to the same value as with the General Electric meter. If the 
meter is correct the standard will show 1.5 and 22.5 revolutions respectively. 
If the standard shows 1.54 the service meter is three per cent slow at light 
load. If the standard shows 1.45, the service meter is three per cent fast at 
light load. 

If it is desired to test three-wire meters, the standard should be con- 
nected into the circuit with one side of the meter under test, the other side 
of the circuit being left open. When the test is conducted in this manner 
the pointer of the standard will revolve at a rate twice as fast as the disk 
of the meter under test, which has but one-half of its current winding in use 
during the test. To effect a direct comparison, the number of revolutions 
made by the meter bing testeed should be multiplied by two. 

Testing: Meters for Accuracy on Inductive load*. — When 
it is desired to test meters for inductive load accuracy the necessary load 
may be obtained in one of several ways as outlined below: 

For obtaining the inductive load from a single-phase circuit a set of two 
or more five^ampere reactance coils, such as are used in the multiple A. C. 
arc lamp, will be found convenient. The coils can be arranged to give 
almost any current value, when used on a 110-volt circuit, up to 25 am- 
peres by means of series parallel connections. The taps which are brought 



INTEGRATING WATTMETER TESTING. 



1019 



cut at numerous points are useful in obtaining close adjustments of current 
value. Fig. 31 illustrates a method of connection for use in testing meters 
on inductive loads, the power factor of which can be directly determined by 
a power-factor meter or by the use of an ammeter, voltmeter and watt- 
meter connected in circuit as indicated. 

Method of Vesting: Service Meter for Inductive Load 
Accuracy. — To conduct this test, the service meter should be loaded to its 
full current capacity as indicated by the ammeter. The lamp load and 
inductive load should be so adjusted as to give a reading on the wattmeter 
equal to one-half of the volt-ampere reading as shown by the reading of 
the ammeter multiplied by the voltage of the circuit. If a standard indi- 
cating wattmeter is used, the watt value is at once apparent. If the rotating 
standard integrating meter is used, however, the approximate watt value may 
be obtained by noting the speed of the pointer which should rotate one-half 
as fast as it would if the same volt-amperes were applied at unity power 
factor. The full-load speed of the rotating standard operating at the cur- 



LAMP BANK 



(k (4 (h(k(k 




Fig. 31. Obtaining Inductive Load from Single-Phase Circuit. 

rent and voltage marked upon the dial is 12 J R.P.M., at a power factor of 
50 per cent. With this method of testing on inductive load at a power 
factor of 50 per cent, it is necessary to take comparative readings the same 
as in the ordinary test of meters. 

Obtaining* Inductive I^oad from Two-Phaie Circuits. —An 
integrating meter can readily be checked for inductive load accuracy if a 
two-phase circuit is available by connecting the current coils of the meter in 
one phase and taking the potential from the other phase as shown in Fig. 32. 
The meter should be given normal full-load current and potential and as 
the current and potential in this case are 90 degrees apart or in quadrature, 
it is obvious that the meter disk should not move. A standard indicating 
or integrating meter should be in circuit during this test as a check upon the 
two-phase current being exactly in quadrature. 

If the standard shows any load the current should be further lagged by 
Inserting a sufficient number of lamps in the phase B circuit, or, if desired, an 
inductance can be inserted in the series circuit of the wattmeter. In order 
to secure the proper phase relation it may in some instances be necessary 
to reverse the primary or secondary connection of the transformer in phase 



1020 



ELECTRICITY METERS. 



B. When the phase displacement is exactly 90 degrees the standard 
should not show any load. 

Obtaining' Inductive JLo.irt from Three-Phase Circuits. — 

The above condition of zero power factor or quadrature may also be ob- 
tained from a balanced three-phase circuit by connecting the meter as shown 
in Fig. 33 with the current coils in phase A, taking the potential across 
phases B and C, the load being placed between phases AB and AC. This 
load must be the same (balanced) on each phase to obtain the desired result. 

Another method of obtaining this condition from a three-phase circuit is 
to transform from three-phase to two-phase and connect the meter into the 
two-phase circuit as shown in Fig. 34. This method necessitates the use of 
special transformers having the "Scott" three-phase to two-phase con- 
nections, but in some cases this method may be more convenient than the 
method shown in Fig. 33, as it eliminates the necessity of maintaining the 
balanced load on the three-phase circuit, it being only necessary to have 
one lamp bank on one phase of the two-phase circuit for a load. Having 
obtained a current in quadrature with the potential, the test should be 
conducted as outlined in the preceding paragraph describing the two- 
phase method. 

Testing* D. C Meters. — For testing D. C. meters a testing arrange- 
ment similar to that shown in Fig. 31 may be employed and the meters tested 




LAMPS 



LAMPS 





PORTABLE 
STANDARD 
INTEGRATING 
WATTMETER 



INTEGRATING 1 
WATTMETER 



Fig. 32. Obtaining Inductive Load from Two-Phase Circuit and 
Using Integrating Wattmeter as Standard. 

by the voltmeter-ammeter method or by the indicating wattmeter method. 
The reactance coils would not be employed, but in general the method of 
test is the same as for A. C. meters previously described. Owing to the 
rate of heating being different for the shunt circuit and the disk, it is neces- 
sary that the meter be run long enough before test to allow it to reach its 
normal operating condition, which is approximately 15 minutes. 

Testing* Polyphase Service Jfleters. — As the polyphase meter is 
really two single-phase meters having a common shaft and registering 
mechanism, the general instructions for the single-phase meters will apply 
to the polyphase meters. The calibration and checking of these meters, 
however, is necessarily more complicated and the following general in- 
structions will be of assistance in the testing of this type of meter. 

Standards for Testing* T*olrphase Meters. — As yet a rotating 
standard of the polyphase type is not (December, 1907) on the market, and 



INTEGRATING WATTMETER TESTING. 



1021 



it is eustomary to use the indicating meter and stop watch method for 
testing this class of meter, although a single-phase portable integrating 
standard wattmeter may be used if the method is properly applied. 



A- 
B- 



Current Coil y M ETE R 



Pot Colt 



V- 



LAMPS 



y 



00 




Fig. 33. Obtaining Inductive Load from Three-Phase Circuit. 

To test a polyphase meter it is customary to employ an artificial load 
and test each side as a single-phase element. To test a self-contained 
meter using neither series or voltage transformers the connections should 
be made as shown in Fig. 35, and for testing a meter using transformers 

CURRENT COIL METER 

Por.coiL 



THREE 
PHASE 




TWO 
PHASE 



Fig. 34. Obtaining Inductive Load from Three- 
Phase Circuit by Use of " Scott " Three-Phase- 
Two-Phase Connection. 



connect as shown in Fig. 36. A three-point switch is provided to cut either 
series element of the service meter in circuit with the standard. As but 
one series side of the meter is in service at a time it is either necessary to 




Fig. 35. 



Connections for Testing Self -Contained Polyphase Meter Using 
Single-Phase Standard. 



1022 



ELECTRICITY METERS. 



multiply the disk revolutions by two or divide the calibrating constant 
by two. The test should be conducted in the same manner as when test- 
ing single-phase meters previously described. It will be noted that both 
potential elements of the service meter are energized, this being essential 
in polyphase testing. 



LINE 




Fig. 36. Connections for Testing Polyphase Meter Employing 
Transformers and Using Single-Phase Standard. 



S£#/£S Trans. 




POLYPHASE 
INDICATING WATTMETER 



Fig. 37. Connections for Testing Polyphase Meter Employing Trans- 
formers. Testing on Running Load and Using Polyphase Standard. 



INTEGRATING WATTMETER TESTING. 



1028 



To test a polyphase meter on the running load, connections should be 
made as shown in Figs. 37-38 and the test conducted in the same manner 
as for single-phase testing. Care should be exercised to connect the poten- 
tial element to the same point to avoid danger of one meter measuring the 
watt loss of the other. 

When desired, the single-phase portable standard integrating watt- 
meter may be used for checking polyphase meters instead of the indicating 
wattmeter. For this purpose the polyphase meter should be connected 
as shown in Figs. 35-36 and the standard integrating meter substituted 
for the indicating meter. When so connected the disk revolutions of the 
polyphase meter should be multiplied by two and directly compared with 
the rotating standard, in which case instructions for single-phase testing 
will apply. If desired the current elements of the polyphase meter may 




jftfraJ POLYPHASE 

INDICATING WATTMETER 



Fig. 38. Connections for Testing Self-Contained Polyphase 
Meter on Running Load and Using Polyphase Standard. 



be connected in series, in which case the service and test meter disks v ,-h 
revolve at the same speed. 

Note: — In all tests of polyphase meters both potential coils must be 
connected in circuit and energized. Polyphase meters should be given 
the same tests at light and full loads as the single-phase meters and the 
same adjustments apply. 

Service Connections of Polyphase meters. — Great care should 
be exercised in the installation of polyphase meters to insure the connections 
being made exactly in accordance with the proper diagrams. This is 
extremely important, as it is possible to make incorrect connections pro- 
ducing excessive errors on inductive loads and still have the meter rotate 
in the proper direction. It is not a safe plan to try out polyphase meter 
connections by alternately opening the sides of the measuring elements 
and noting that the disk rotates in the forward direction in each case, unless 
the power facter is definitely known. If the meter should be connected to 



1024 



ELECTRICITY METERS. 



a three-phase circuit operating at a power factor of less than 50 per cent, 
one element should cause the disk to rotate backwards, and if the above test 
alone is depended upon when installing the meter, it is very probable 
that the average man installing the meter under these conditions would 
reverse the side rotating backwards, thus introducing an enormous error as 
the power factor of the circuit changed. It is also possible to so connect a 
polyphase meter that it will run in either the forward or reverse direction 
on both elements regardless of the power factor, the meter either running 
faster or slower than it would on unity power factor, depending upon the 
phase relation of the particular connection used. 

The action of two single-phase meters, or the two single-phase elements 
of a polyphase meter operating upon a three-phase circuit, may be explained 
by the following vector diagrams. 

Figure 39 shows the phase relations between the current and potential of 
each single-phase element when operating on a three-phase circuit at unity 
power factor, one meter element having its series coil in A and its poten- 
tial coil across AC and the other element having its series coil in B and its 
potential coil across BC. From this diagram it will be seen that the cur- 
rent in phase A is displaced 30 degrees from its respective potential AC and 
the current in phase B is also displaced 30 degrees from its potential BC, 




Fig. 39. 



Fig. 40. 



but in the opposite direction from that in phase A, thus giving the effect of 
a lagging current in phase B and a leading current in phase A, the resultant 
being zero displacement, or unity power factor, on the three-phase circuit. 
From this it will be seen that at unity power factor on the three-phase cir- 
cuit each single-phase element of the polyphase meter will operate at the 
same speed, each element operating at a single-phase power factor of about 
88 per cent, or the cosine of 30 degrees. 

Figure 40 shows the condition existing when the current in the three- 
phase circuit lags 30 degrees or is operating at a power factor of 86 per cent. 
From this diagram it will be seen that the current in phase B lags behind 
its respective potential BC 30 -I- 30 degrees or 60 degrees, while the cur- 
rent in A has been brought exactly in phase with its respective potential 
AC. This gives a condition where one single-phase element is operating at 
a power factor of 50 per cent (or cosine of 60 degrees), while the other ele- 
ment is operating at unity power factor, its current and potential being 
exactly in phase. Under this condition one element will run twice as fast 
as the other. Ox, Oy and Oz show positions of three-phase current with 
30 degrees lag. To show phase relation of each current with its respective 
voltage, Ore is rotated about center A instead of O and falls in phase with 
its voltage AC. Current Oy is rotated about center B and falls 60 degrees 
behind its voltage BC. 

Figure 41 shows the condition met with when the current in the three- 
phase circuit lags 60 degrees or is operating at a power factor of 50 per cent. 
From this diagram it will be seen that the current in phase B lags its re- 



INTEGRATING WATTMETER TESTING, 



1025 



spective potential BC 60 4- 30 degrees or 90 degrees, while the current in 
pnase A lags its potential AC 60 — 30 degrees or 30 degrees. This gives a 
condition where one single-phase element is operating at zero power factor 
or cosine of 90 degrees, while the other element is operating at 86 per cent 
or cosine of 30 degrees. Under this condition one element has stopped, 
the other element doing all the work. For clearness in showing phase 
relations the centers of rotation of the currents are changed as in Fig. 40. 

Figure 42 shows the condition met with when the current in the three- 
phase circuit lags 90 degrees or is operating at a power factor of zero. From 
this diagram it will be seen that the current in phase B lags its respective 
potential BC 90 4- 30 degrees or 120 degrees, while the current in phase A 
lags its^ respective potential AC 90 — 30 degrees or 60 degrees. As the 
angle of lag in phase B now exceeds 90 degrees, the cosine of the angle is 
the same as the sine of the difference between the angle and 90 degrees, in 
this case minus 30 degrees, giving a power factor of minus 50 per cent in 
phase B and a power factor of plus 50 per cent in phase A. From this it 
will be. seen that at zero power factor of the three-phase circuit, one single- 
phase element of the meter will try to operate at half speed in one direction 




Fig. 42. 



while the other element is trying to operate at half speed in the opposite 
direction, the resultant of these two equal forces acting in opposite directions 
being zero; hence, the meter as a whole will not move. 

From the preceding explanation of the phase relations of single-phase 
meters used on a three-phase circuit, it will be apparent that the energy of 
a three-phase circuit cannot be measured by the use of one standard single- 
phase meter. It also shows why it is extremely important to have the 
polyphase meter connected into the circuit in accordance with the proper 
diagrams as, owing to the fact that one element of the polyphase meter 
should tend to reverse its direction of rotation on a power factor of less than 
50 per cent, it is not safe to depend upon the direction of rotation of each 
element separately to determine whether or not a meter is connected into 
the circuit properly unless the power factor is known. 

The general scheme of connections for correctly connecting a polyphase 
meter to measure the energy of a three-phase circuit is shown in Fig. 43, 
the current coil of one element being connected in line A and its poten- 
tial across A and B, the current coils of the other element being connected 
in line C and its potential coils across B and C. 

If a meter should be connected, as shown in Fig. 44, with the current coil 
of one element in line A and its potential across A and C and the current 
of the other element in line C with its potential coil across B and C, both 
elements of the meter will run in either the forward or reverse direction at 



1026 



ELECTRICITY METERS. 



all values of power factor at equal speeds, and will be either fast or slow on 
all power factors other than unity, depending on the phase relations of the 
particular connection used. This erroneous connection should be care- 
fully guarded against, and it will be readily seen that this condition cannot 
be detected by the common method used of opening one side of the meter 
at a time to determine that the meter runs in the forward direction on each 
element alone. 

The effect of the connections shown in Fig. 44 can be seen by referring to 
Fig. 45. If one series element of the polyphase meter is connected in at A 
and its potential element connected across AC, and the other series element 

CurrentCof/ 

VSAAA— - 



> Potential Co) I 



LOAD 



LINE 



Potential Coil 



WW 

Current Coif 

Fig. 43. 

connected in at B with its potential element connected across BA, when 
operating under 30 degrees lag the currents Ox and Oy will be shifted so 
that botn will be in phase with their voltage and the meter will run in a 
forward direction faster than it will at unity power factor of the three- 
phase circuit. With one series element of the meter connected in at A and 
its potential element connected across AB and the other series element 
connected in at B and its potential element connected across BC, the cur- 



Current Coil 
— V\A/V 



A 



Potential Coil 



LOAD 



B 



LINE 



Potential Coil 



Current Coil 

Fig. 44. 

rents will be shifted so that both Ox and Oy lag behind their respective 
voltages and the meter will consequently run slower than it will at unity 
power factor of the three-phase circuit. 

Practical Methods of Checking" Connections of Poly- 
phase Meters. — In cases where it is not positively known that the power 
factor is above 50 per cent, the following method may be used, which is 
based on the fact that the sum of the two readings should be positive, so 
long as the power is in the positive direction. When the currents in the 
voltage and series coils, as indicated by the clock diagram, are in the same 
direction, or within 90 degrees of being in the same direction, the meter will 
read forward. When the current in the series coil is more than 90 degrees 
out of phase with the voltage, the meter will reverse. 

First. By proper testing with an incandescent lamp or a voltmeter, 
obtain three voltage leads, A, B, C, having equal voltages between them. 



INTEGRATING WATTMETEK TESTING. 



1027 



Second. Connect these leads to the voltage circuits of the wattmeters 

as per Fig. 43. 

Third. Connect the series transformer at A to meter whose potential 

is connected to AC, and series trans- 
former at B to meter whose potential 
is connected to BC. See clock dia- 
gram (Fig. 46) giving the phase rela- 
tions. In this diagram, AC repre- 
sents the voltage on meter connected 
at A, BC the voltage on meter 
connected at B, OA the current in 
meter connected at A, and OB the 
current in meter connected at B. 

Fourth. Change voltage connec- 
tion from AC to AB on meter con- 
nected at A. If power factor is 100, 
the readings will be alike with both 
connections. If the power factor is 
less than 100 and greater than 50, 
the readings will differ, but be in the 
same direction (either both positive or 
both negative). If equal to 50, one 
of the readings will be zero. If less 
than 50, the readings with connec- 
tions AC and AB will be reversed in 
direction, with respect to each other. 
Fifth. The same test may be performed on meter connected at B, by 

changing the voltage connections from BC to BA. If the power factor 




Fig. 45. 







' I \ 

A 60 i A 40 
A 50 



Fig. 46. 



OA current in meter at A 100 per cent P.F. 
OA 60 current in meter at A 60 per cent P.F. 
OA 50 current in meter at A 50 per cent P.F. 
OA 40 current in meter at A 40 per cent P.F. 
OB current in meter at A 100 per cent P.F. 
OB 60 current in meter at A 60 per cent P.F. 
OB 50 current in meter at A 50 per cent P.F. 
OB 40 current in meter at A 40 per cent P.F, 



1028 



ELECTRICITY METERS. 



is 100, the readings will be alike. If less than 100 and more than 50. 
the readings will differ, but be in the same direction. If equal to 50, one of 
the readings will be zero. If less than 50, the readings with connections 
BC and BA will be reversed in direction with respect to each other. 

Sixth. If it is found from the above tests that the power factor is greater 
than 50, connect the series coil of the meters so that both read forward. 
If the power factor is less than 50, connect the series coil of the slower 
meter so that meter reads backward, and the series coil of the faster meter 
so that it reads forward. 

The above description indicates the use of two single-phase meters, but 
holds equally true for a polyphase meter consisting of two single-phase 
meter elements driving the same shaft. 

nETEH TE8TMG FOJU^Il I,JE. 

Below will be found the formulae and testing constants to be used in col- 
junction with the testing methods described on pages 1013 to 1023. 

Formula for Vesting* the Shallenberg*er Ampere-bout 
Meter. 

To Tell the Exact Current Flowing at any Time. 

Note the number of revolutions made by the small "tell-tale" index of 
the register dial, in a number of seconds equal to the constant of the meter. 
The number of revolutions noted will correspond to the number of amperes 
passing through the meter. For example: the 20-ampere meter constant is 
63.3; if the index makes 10 revolutions in 63.3 seconds, 10 amperes are 
passing through the meter. In order to avoid errors in readings, it is cus- 
tomary to take the number of revolutions in a longer time, say 120 seconds, 
using the following formula: 

No. of Rev. X Meter Constant ~ 

rr t-5 = Current. 

No. of Sec. 

If, therefore, the index of a 20-ampere meter makes 19 revolutions in 120 
seconds the current passing is 

19 X 63.3 tn 

— ^r — = 10 amperes. 

The cover should be left on the meter while these readings are taken. 
The constants of the different capacity meters are given below: 



Meter Capacity. 
Amperes. 


Calibrating 
Constant. 


Meter Capacity. 
Amperes. 


Calibrating 
Constant. 


5 
10 
20 
40 


22.5 

33.8 

63.3 

126.6 


80 
120 
160 


253.1 

386 

506 



Testing* Formula for Shallenlterg-er and Westing*house 
Integrating* Wattmeter*. 

The standard formula for testing all types and capacities, when using 

indicating standards and stop watches, is Watts = ™ K in which: 

R = Number of complete revolutions in time T. 
T = Time in seconds required for revolutions R. 
K = Jonstant. 

The constant " K " varies with different types and capacities as outlined 
on the following page. 



METER TESTING FORMULA. 1029 

Rating's. — In all cases the volt and ampere values used with the 
formula are those marked on the meter. The full-load speed of Types 
"B" and "C* meters is 25 R.P.M. 

lulMoad Speed's. — The full-load speed of Shallenberger, Westing- 
house, Round Pattern and Type "A" Single and Polyphase Wattmeters is 
50 R.P.M. The full-load speed of Type "B" single phase and Type "C" 
single or polyphase wattmeters is 25 R.P.M. 

For Shallenberger, Westinghouse Round Pattern Back Connected and 
Type "A" Meters the constant "K" has the following values: 

2-Wire Meters {Single Phase). 

For self-contained meters K = volts X amps. X 1.2. 

For meter used with series transformer only (but checked without) K = 
volts (as marked on dial) X 6. 

For meter used with series and voltage transformers (but checked with- 
out) K = 600. 

For meter used with transformers of either or both forms (and checked 
with) K = volts X amps. X 1.2. 

3-Wire Meters (Single Phase) . 

For self-contained meters K = volts X amps. X 2.4. 

For meters used with series transformers only (but checked without) 
K = volts X 6. 

Type "A" Polyphase Wattmeters. 

For self-contained meters K = volts X amps. X 2.4. 

For meters used with series transformers only (but checked without) 
K = 5 X volts X 2.4. 

For meters used with series and voltage transformers (but checked with- 
out) K = 1200. 

For meters used with transformers of either or both forms (and checked 
with) K = volts X amps. X 2.4. 

The Testing: Constant " I£ " of Westing-house Types " JB " 
and " C " Meters is as follow*: 

2-Wire Meters (Single Phase). 

For self-contained meters K = volts X amps. X 2.4. 

For meters used with series transformers only (but checked without) 
K = volts X 5 X 2.4. 

For meters used with series and voltage transformers (but checked with- 
out) K = 5 X 100 X 2.4. 

For meters used with transformers of either or both forms (and checked 
with) K = volts X amps. X 2.4. 

3-Wire Meters (Single Phase) . 

For self-contained meters K = volts X amps. X 4.8. 

For meters used with series transformers (but checked without) K = 
volts (as marked on meter) X 12. 

Note. — When the voltage marking of Westinghouse three-wire meters 
covers both the voltage between neutral and outer and the voltage between 
outers such as 100-200 volts, K = volts (between outside wires) X am- 
peres as marked on meter X 2.4. 

Type "C" Polyphase Wattmeters. 

For self-contained meters K = volts X amps. X 4.8. 

For meters used with series transformers only (but checked without) 
K = 5 X volts X 4.8. 

For meters used with series and voltage transformers (but checked with- 
out) K - 2400. 

For meters used with transformers of either or both forms (and 
checked with) K = volts X amps. X 4.8. 



1030 



ELECTRICITY METERS. 



WESTUVGHOUSE DIRECT-CURRENT METERS. 
For all capacity meters K = volts X amps. X 2.4. 

Formula for Testing- General Electric Recording: 
Wattmeters. 

The standard formula for testing all types and capacities when using 



indicating standards and stop watches is Watts = 



3600 XK X R 



in which: 



R = number of revolutions. 

S = number of seconds in which revolutions is made. 
K = calibrating constant marked on dial face of "non-direct" reading 
meters and on disk of "direct" reading meters. 

Table of General Electric D. C. Type "C6" Testing* Con- 
stants ** li " and Watts per 11 evolution per Minute. 



Capacity 
of 
Meters 
in Am- 
peres. 



3 

5 

10 

15 

25 

50 

75 

100 

150 

300 

600 



100-120 Volts. 



Testing 
Constant. 



.125 

.2 

.4 



1. 
2. 
3. 

4. 

6. 
12.5 
25. 



Watts Per 
Revolu- 
tion per 
Minute. 



7.5 
12. 

24. 

36. 

60. 
120. 
180. 
240. 
360. 
750. 
1500. 



200-240 Volts. 



Testing 
Constant . 



.25 
.4 
.75 
1.25 
2. 
4. 
6. 
7.5 
12.5 
25. 
50. 



Watts Per 
Revolu- 
tion Per 
Minute. 



15 
24 
45 
75 

120 
240 
360 
450 
750 
1500 
3000 



500-600 Volts. 



Testing 
Constant 



.6 



1. 

2. 

3. 

5. 
10. 
15. 
20. 
30. 
60. 
125. 



Watts Per 
Revolu- 
tion Per 
Minute. 



36 

60 

120 

180 

300 

600 

900 

1200 

1800 

3600 

7500 



Table of General Electric A. C. Type "* " Testing- Con- 
stants " K " and Watt* per Revolution per .Tlinute. 



Capacity 
of 


100-130 Volts. 


200-260 Volts. 


500-600 Volts. 














Meters 




Watts Per 




Watts Per 




Watts Per 


in Am- 


Testing 


Revolu- 


Testing 


Revolu- 


Testing 


Revolu- 


peres. 


Constant . 


tion Per 
Minute. 


Constant. 


tion Per 
Minute. 


Constant. 


tion Per 
Minute. 


3 


.2 


12 


.4 


24 


1. 


60 


5 


.3 


18 


.6 


36 


1.5 


75 


10 


.6 


36 


1.25 


75 


3. 


180 


15 


1. 


60 


2. 


120 


5. 


300 


25 


1.5 


90 


3. 


180 


7.5 


450 


50 


3. 


180 


6. 


360 


15. 


900 


75 


5. 


300 


10. 


600 


25. 


1500 


100 


6. 


360 


12.5 


750 


30. 


1800 


150 


10. 


600 


20. 


1200 


50. 


3000 


200 


12.5 


750 


25. 


1500 


60. 


3600 


300 


20. 


1200 


40. 


2400 


100 


6000 



DUNCAN METERS. 



1031 







" » 3 " Polyphase 


UEeters. 






100-120 Volts. 


200-260 Volts. 


500-650 Volts. 




25 Cycles 


60 Cycles 


25 Cycles 


60 Cycles 


25 Cycles 


60 Cycles 


Amps. 


Testing 


Testing 


Testing 


Testing 


Testing 


Testing 




Constant. 


Constant. 


Constant. 


Constant. 


Constant. 


Constant. 


3 


1. 


.4 


• 2 


.75 


5. 


2 


5 


1.5 


.6 


3 


1.25 


7.5 


3 


10 


3. 


1.25 


6 


2.5 


15. 


6 


15 


5. 


2. 


10 


4. 


25. 


10 


25 


7.5 


3. 


15 


6. 


40. 


15 


50 


15. 


6. 


30 


12.5 


75. 


30 


75 


20. 


7.5 


40 


15. 


100. 


40 


100 


30. 


12.5 


60 


25. 


150. 


60 


150 


40. 


15. 


75 


30. 


200. 


75 



Note : — Testing constant is actual watt-hours per revolution of disk. 



formula for Testing- Dnncan Recording* Wattmeter*. 

The standard formula for testing all types and capacities when using 

• j. .- j j j . u • w ** Rev. X 3600 X K . 
indicating standards and stop watches is Watts = ~ — , in 

which: 

R = Number of complete revolutions. 
Sec.= Time in seconds required for revolutions R. 
K = Testing constant marked on meter disk. 

Table of Duncan Testing* Constants " K " and Watts per 
Revolution per Minute. 



Capacity 
of 


100-125 Volts. 


200-250 Volts. 


450-550 Volts. 


Meters 


Testing 


Watts per 


Testing 


Watts per 


Testing 


Watts per 


m 


Con- 


Revolution 


Con- 


Revolution 


Con- 


Revolution 


Amperes. 


stant. 


per Minute. 


stant. 


per Minute. 


stant. 


per Minute. 


2i 


i 


15 


$ 


30 


1 


60 


5 


A 


15 


1 


30 


1 


60 


7* 


£ 


30 


1 


60 


2 


120 


10 


^ 


30 


1 


60 


2 


120 


15 


1 


60 


2 


120 


5 


300 


25 


1 


60 


2 


120 


5 


300 


50 


2 


120 


4 


240 


10 


600 


75 


3 


180 


6 


360 


16 


960 


100 


4 


240 


8 


480 


20 


1,200 


150 


6 


360 


12 


720 


30 


1,800 


200 


8 


480 


16 


960 


40 


2,400 


300 


12 


720 


25 


1,500 


60 


3,600 


450 


20 


1,200 


30 


1,800 


80 


4,800 


600 


25 


1,500 


50 


3,000 


100 


6,000 


800 


30 


1,800 


60 


3,600 


160 


9,600 


1,000 


40 


2,400 


80 


4,800 


200 


12,000 


1,200 


50 


3,000 


100 


6,000 


250 


15,000 


1,500 


60 


3,600 


120 


7,200 


300 


18,000 


2,000 


80 


4,800 


160 


9,600 


400 


24,000 


2,500 


100 


6,000 


200 


12,000 


500 


30,000 


3.000 


120 


7,200 


250 


15,000 


600 


36,000 


4,000 


160 


9,600 


300 


18,000 


800 


48,000 


5,000 


200 


12.000 


400 


24,000 


1,000 


60.000 


6,000 


250 


15,000 


500 


30,000 


1,200 


72,000 


8,000 


300 


18,000 


600 


36,000 


1,600 


96,000 


10,000 


400 


24,000 


800 


48,000 


2,000 


120,000 



1032 



ELECTRICITY METERS. 



The table given below will be found convenient in showing the per cent 
fast or slow which a meter is running when employed in conjunction with 



the following formula : 



Watts Constituting Load 
Testing Constant X 60 



= Rev. Per Min. 



Per Cent Error Table for Fifth* of it Second. 



Time 


Per Cent 


Time 


Per Cent 


Time 


Per Cent 


Time 


Per Cent 


in 

Seconds 


Fast 


in 
Seconds 


Fast 


in 
Seconds 


Slow 


in 

Seconds 


Slow 


40.20 


49.25 


50.20 


19.52 


60.20 


0.33 


70.20 


14.52 


.40 


58.51 


.40 


19.05 


.40 


0.67 


.40 


14.77 


.60 


47.78 


.60 


18.58 


.60 


0.99 


.60 


15.01 


.80 


47.06 


.80 


18.11 


.80 


1.31 


.80 


15.25 


41.00 


46.34 


51.00 


17.65 


61.00 


1.63 


71.00 


15.50 


.20 


45.63 


.20 


17.19 


.20 


1.96 


.20 


15.73 


.40 


44.93 


.40 


16.73 


.40 


2.27 


.40 


15.96 


.60 


44.23 


.60 


16.28 


.60 


2.59 


.60 


16.20 


.80 


43.54 


.80 


15.83 


.80 


2.91 


.80 


16.43 


42.00 


42.86 


52.00 


15-38 


62.00 


3.22 


72.00 


16.66 


.20 


42.18 


.20 


14.94 


.20 


3.53 


.20 


16.89 


.40 


41.51 


.40 


14.50 


.40 


3.84 


.40 


17.12 


.60 


40.85 


.60 


14.07 


.60 


4.15 


.60 


17.35 


.80 


40.19 


.80 


13.64 


.80 


4.45 


.80 


17.58 


43.00 


39.53 


53.00 


13.21 


63.00 


4.76 


73.00 


17.81 


.20 


38.89 


.20 


12.78 


.20 


5.06 


.20 


18.03 


.40 


38.25 


.40 


12.36 


.40 


5.36 


.40 


18.25 


.60 


37.61 


.60 


11.94 


.60 


5.66 


.60 


18.47 


.80 


36.98 


.80 


11.52 


.80 


5.95 


.80 


18.70 


44.00 


36.36 


54.00 


11.11 


64.00 


6.25 


74.00 


18.92 ' 


.20 


35.75 


.20 


10.70 


.20 


6.54 


.20 


19.14 


.40 


35.14 


.40 


10.29 


.40 


6.83 


.40 


19.35 


.60 


34.53 


.60 


9.89 


.60 


- 7.12 


.60 


19.57 


.80 


33.93 


.80 


9.49 


.80 


7.40 


.80 


19.79 


45.00 


33.33 


55.00 


9.09 


65.00 


7.69 


75.00 


20.00 


.20 


32.74 


.20 


8.69 


.20 


7.97 


.20 


20.21 


.40 


32.16 


.40 


8.30 


.40 


8.25 


.40 


20.42 


.60 


31.58 


.60 


7.91 


.60 


8.53 


.60 


20.63 


.80 


31.00 


.80 


7.53 


.80 


8.81 


.80 


20.84 


46.00 


30.43 


56.00 


7.14 


66.00 


9.09 


76.00 


21.05 


.20 


29.87 


.20 


6.76 


.20 


9.36 


.20 


21.26 


.40 


29.31 


.40 


6.38 


.40 


9.63 


.40 


21.47 


.60 


28.76 


.60 


6.01 


.60 


9.92 


.60 


21.68 


.80 


28.21 


.80 


5.63 


.80 


10.17 


.80 


21.88 


47.00 


27.66 


57.00 


5.26 


67.00 


10.44 


77.00 


22.07 


.20 


27.12 


.20 


4.89 


.20 


10.71 


.20 


22.27 


.40 


26.58 


.40 


4.53 


.40 


10.97 


.40 


22.38 


.60 


26.05 


.60 


4.17 


.60 


11.24 


.60 


22.68 


.80 


25.52 


.80 


3.81 


.80 


11.50 


.80 


22.88 


48.00 


25.00 


58.00 


3.45 


68.00 


11.76 


78.00 


23.08 


.20 


24.40 


.20 


3.09 


.20 


12.02 


.20 


23.28 


.40 


23.96 


.40 


2.74 


.40 


12.28 


.40 


23.47 


.60 


23.45 


.60 


2.39 


.60 


12.53 


.60 


23.66 


.80 


23.15 


.80 


2.04 


.80 


12.79 


.80 


23.86 


49.00 


22.45 


59.00 


1.69 


69.00 


13.04 


79.00 


24.05 


.20 


21.95 


.20 


1.35 


.20 


13.29 


.20 


24.24 


.40 


21.46 


.40 


1.01 


.40 


13.54 


.40 


24.43 


.60 


20.97 


.60 


0.67 


.60 


13.79 


.60 


24.63 


.80 


20.48 


.80 


0.33 


.80 


14.04 


.80 


24.82 


50.00 


20.00 


60.00 


0.00 


70.00 


14.28 


80.00 


25.00 



FOKT WAYNE SINGLE-PHASE METERS. 



1033 



Example. — If the revolutions to be made in one minute are completed 
in exactly 60 seconds the speed is correct and the per cent error is zero, but if 
the revolutions were made in 57 seconds then the meter is running 5.26 per 
cent fast; if completed in 58.4 seconds it is 2.74 per cent fast. When the 
time exceeds 60 seconds, the meter is slow. If it requires 63 seconds it is 
4.76 per cent slow; if 64.6 seconds it is 7.12 per cent slow. The per cent 
error will be found in the column after the time in seconds. The seconds 
columns are divided into fifths of a second so as to conform to most stop 
watches whose seconds are split to fifths. 



Formula for Testing- Fort Wayne Type "K" Wattmeter. 

The standard formula for testing all types and capacities when using 
indicating standards and stop watch is Watts = '■ ~ • 

Tables of Values of Constant <k It " for Different Capac- 
ities, Type ki It " Fort Wayne Sing*le-l*liase meters. 

(For meters whose serial number is 344,999 or less.) 



Am- 


2- Wire 


2-Wire 


2-Wire 


3-Wire 


2-Wire 


2-Wire 


2-Wire 


50 V. 


110 V. 


220 V. 


220 V. 


550 V. 


1100 V. 


2200 V. 


peres . 


41 K." 


"K." 


"K." 


"K." 


"K." 


"K." 


"K." 


3 




9 


18 


18 


45 


90 


90 


5 


"9 


9 


18 


18 


45 


90 


180 


7h 








27 








10 


"9 


18 


"36 


36 


"90 


' 'l80 


' *360 


15 


18 


36 


54 


54 


180 


360 


540 


20 


18 


36 


72 


72 


180 


360 


720 


25 


18 


36 


72 


72 


180 


360 


900 


30 


36 


72 


90 


90 


360 


720 


1,080 


40 


36 


72 


108 


108 


360 


720 


1,440 


50 


36 


72 


144 


144 


360 


720 


1,800 


60 


54 


108 


180 


180 


540 


1,080 


2,160 


75 


54 


108 


216 


216 


540 


1,080 


2,700 


100 


72 


144 


288 


288 


720 


1,440 


3,600 


125 


90 


180 


360 


360 


900 


1,800 


4,500 


150 


1-08 


216 


432 


576 


1,080 


2,160 


5,400 


200 


144 


288 


576 


1,440 


2,880 


7,200 


250 


180 


360 


720 


720 


1,800 


3,600 


9,000 


300 


270 


540 


1,080 


1,080 


2,700 


5,400 


10,800 


400 


360 


720 


1,440 


1,440 


3,600 


7,200 


14,400 


500 


450 


900 


1,800 


1,800 


4,500 


9,000 


18,000 


600 


540 


1,080 


2,160 


2,160 


5,400 


10,800 


21,600 


800 


720 


1,440 


2,880 


2,880 


7,200 


14,400 


28,800 


1,000 


900 


1,800 


3,600 


3,600 


9,000 


18,000 


36,000 



Use these Constants for High Torque Meters. 



15 
30 



13| 
27 



27 
54 



54 
90 



54 
90 



135 
270 



270 
540 



540 
1,080 



1034 



ELECTRICITY METERS. 



Table of Values of Constant " K " for Different Capac- 
ities, Type * k JbL " fort Wayne Single-Phase Meters. 

(For meters whose serial number is 345,000 or above.) 



Am- 


2-Wire 


2-Wire 


3-Wire 


2-Wire 


2-Wire 


2-Wire 


110 V. 


220 V. 


220 V. 


440 V. 


550 V. 


1100 V. 


peres. 


" K." 


" K." 


" K." 


" K." 


"K". 


" K." 


5 


9 


18 


18 


36 


45 


90 


10 


18 


36 


36 


72 


90 


180 


15 


27 


54 


54 


108 


135 


270 


20 


36 


72 


72 


144 


180 


360 


25 


45 


90 


90 


180 


225 


450 


40 


72 


144 


144 


288 


360 


720 


50 


90 


180 


180 


360 


450 


900 


75 


135 


270 


270 


540 


675 


1,350 


100 


180 


360 


360 


720 


900 


1,800 


125 


225 


450 


450 


900 


1,125 


2,250 


150 


270 


540 


540 


1,080 


1,350 


2,700 


200 


360 


720 


720 


1,440 


1,800 


3,600 


300 


540 


1,080 


1,080 


2,160 


2,700 


5,400 


400 


720 


1,440 


1,440 


2,880 


3,600 


7,200 


600 


1,080 


2,160 


2,160 


4,320 


5,400 


10,800 


800 


1,440 


2,880 


2,880 


5,760 


7,200 


14,400 



2-Wire 
2200 V. 



• 180 

360 

540 

720 

900 

1,440 

1,800 

2,700 

3,600 

4,500 

5,400 

7,200 

10,800 

14,400 

21,600 

28,800 



Table of Values of Constant *• M " for Different Capacities, 
Type " K " Fort Wayne Polyphase Wattmeters. 

(For meters whose serial number is 344,999 or less.) 









Volts. 






Amperes 
Capacity. 














110 


220 


440 


550 


1100 


2200 




"K." 


"K." 


"K." 


"K." 


"K." 


"K." 


3 


18 


36 


72 


90 


180 


360 


5 


36 


72 


144 


180 


360 


720 


10 


72 


144 


288 


360 


720 


1,440 


15 


108 


216 


432 


540 


1,080 


2,160 


20 


144 


288 


576 


720 


1,440 


2,880 


25 


144 


288 


576 


720 


1,800 


3,600 


30 


216 


360 


720 


1,080 


2,160 


4,320 


40 


288 


576 


1,152 


1,440 


2,880 


5,760 


50 


288 


576 


1,152 


1,440 


3,600 


7,200 


60 


432 


864 


1,728 


2,160 


4,320 


8,640 


75 


432 


864 


1,728 


2,160 


5,400 


10,800 


100 


576 


1,152 


2,304 


2,880 


7,200 


14,400 


125 


720 


1,440 


2,880 


3,600 


9,000 


18,000 


150 


864 


1,800 


3,600 


4,320 


10,800 


21,600 


200 


1,440 


2,880 


5,760 


7,200 


14,400 


28,800 


250 


1,800 


3,600 


7,200 


9,000 


18,000 


36,000 


300 


2,160 


4,320 


8,640 


10,800 


21,600 


43,200 


400 


2,880 


5,760 


11,520 


14,400 


28,800 


57,600 


500 


3,600 


7,200 


14,400 


18,000 


36,000 


72,000 


600 


4,320 


8,640 


17,280 


21,600 


43,200 


86,400 


800 


5,760 


11,520 


23,040 


28,800 


57,600 


115,200 


1.000 


7,200 


14,400 


28,800 


36,000 


72,000 


144,000 



SANGAMO METERS. 



1035 



Table of Values of Constant "XL" for Different Capacities, 
Type U K" JTort Wayne Polyphase Wattmeters. 

(For meters whose serial number is 345,000 or above.) 









Volts. 






Amperes 














Capacity. 


110 


220 


440 


550 


1100 


2200 




"K." 


"K." 


"K." 


"K." 


"K." 


"K." 


5 


36 


- 72 


144 


180 


360 


720 


10 


72 


144 


288 


360 


720 


1,440 


15 


108 


216 


432 


540 


1,080 


2,160 


25 


180 


360 


720 


900 


1,800 


3,600 


50 


360 


720 


1,440 


1,800 


3,600 


7,200 


75 


540 


1,080 


2,160 


2,700 


5,400 


10,800 


100 


720 


1,440 


2,880 


3,600 


7,200 


14,400 


150 


1,080 


2,160 


4,320 


5,400 


10,800 


21,600 


200 


1,440 


2,8.80 


5,760 


7,200 


14,400 


28,800 


300 


2,160 


4,320 


8,640 


10,800 


21,600 


43,200 


400 


2,880 


5,760 


11,520 


14,400 


28,800 


57,600 


600 


4,320 


8,640 


17,280 


21,600 


43,200 


86,400 


800 


5,760 


11,520 


23,040 


28,800 


57,600 


115,200 



( 



Formula for Testing: $ang*amo Wattmeters. 

"K" equals watt-seconds per revolution of armature, 3600 watt-seconds 
being one watt-hour. The method of using these values of "K," the for- 
mula for obtaining correct speed at any load is simple. Thus if W equals 
observed watts of load, S equals correct time in seconds for one revolution; 
then S equals " K" divided by W. If S' is the observed time in seconds for 
one revolution, the percentage of error equals S' minus S, divided by S'. 
If this quantity is negative, the meter is fast, if the quantity is positive, the 
meter is slow. 

Note. — The value of " K" as given below will also apply in all cases to 
the new alternating-current meter, type "F," except for the 5-ampere, 
110-volt type, which will have "K" equals 1800, and for the 5-ampere 220- 
volt type, it will have "K" equals 3600. 



Table of Testing* Constants " M . " for Sangramo meters. 
Type " » " ». C. and Type " K " A. C. 



Amperes. 


100-125 Volts 


200-250 Volts 


500-600 Volts 


5 


2,400 


4,800 


12,000 


10 


2,400 


4,800 


12,000 


20 


4,800 


9,600 


24,000 


30 


7,200 


14,400 


36,000 


40 


9,600 


19,200 


48,000 


60 


14,400 


28,800 


72,000 


80 


19,200 


38,400 


96,000 


100 


24,000 


48,000 


120,000 


150 


36,000 


72,000 


180,000 


200 


48,000 


96,000 


240,000 



1036 



ELECTRICITY METERS. 



GRAPHIC RECORDING METEHS. 

As the necessity of obtaining more 
accurate records of plant operation 
becomes more apparent, means of ob- 
taining these records automatically 
are demanded. Several different forms 
have been developed by various manu- 
facturers and those described herein 
are representative of American prac- 
tice. 

Bristol Recording' Meters. 

Figure 47 illustrates the Bristol Am- 
meter which has the same general 
appearance as the voltmeters and watt- 
meters. A is a stationary coil or 
solenoid through which passes the cur- 
rent to be measured; B is a thin disk 
armature of soft iron secured to a non- 
magnetic shaft which extends through 
the center of the solenoid A and is 
supported at its opposite ends on steel 
knife edged spring supports C and D. 
The recording pen E is attached di- 
rectly to the spring support D and the 
point is arranged to lightly drag on a 
revolving chart, driven by clock-work, 
shown in illustration. 

Operation. — As current passes 
through the coil A the magnetic field 
generated attracts the iron armature B drawing it directly toward the left 
hand end of coil A (when facing meter). This movement of B is, through 




Fig. 47. Bristol Ammeter. 




Fig. 48. General Electric Curve Drawing Meter. 



WESTINGHOUSE GRAPHIC RECORDING METERS. 1037 



its supporting structure, transmitted to the recording pen E, the point of 
which moves across the chart. 

Voltmeter Construction. — The voltmeter construction is similar 
to that of the ammeter, with the exception that the iron armature B is 
replaced by a wire-wound armature which is connected in series with the 
stationary coil and through a resistance to line. Of course it should be 
understood that the stationary coils of ammeters are wound with com- 
paratively heavy wire and the voltmeter coils with comparatively fine wire. 

Single-Phase Wattmeters. — The wattmeter construction is similar 
to that of the voltmeter, except that the stationary coil is wound with wire of 
sufficient capacity to carry the current to be measured. The moving coil 
is, through a resistance, connected directly across the line, or, in high- 
capacity alternating-current circuits is operated from the secondary of a 
voltage transformer. 



General Electric Graphic Recording- Meters. 

Figure 48 illustrates the G. E. "Curve Drawing Instruments." The 
meters are made as ammeters, voltmeters, single-phase and polyphase 
wattmeters, all having the same general appearance. 

Principle of Operation. — The voltmeters and wattmeters work 
upon the well-known "Siemens Dynamometer" principle, employing fixed 
and moving coils. The ammeters are of the "Magnetic vane Type," em- 
ploying an iron armature suspended within two fixed coils which carry the 
current to be measured. 

Construction. — Fig. 49 illustrates the measuring elements of an am- 
meter in which — 

AA = Fixed coils connected 
in series. 

B = Iron armature suspended 
between coils AA. 

C = Guide bearing for lower 
end of shaft D. 

D = Suspended shaft carry- 
ing armature B, control spring 
E and pen supporting arms. 

E = Control or restraining 
springs. 

F = Suspension wire carry- 
ing moving element. 

G = Supporting frame car- 
rying pivoted pen arm H. 

H ==■ Spring controlled pen 
arm pivoted at I and carrying 
glass pen K. 

I = Pivoted support for pen 
arm H. 

J = Control spring holding 
pen against the record chart L. 



i 




Fig. 49. 



K = Recording glass pen bearing on chart L. 

L = Record chart driven by clock mechanism (not shown). 

Action of Ifleter. — The armature B is so located in relation to the 
fixed coils AA that when current flows through them it is attracted by the 
magnetic field and tends to rotate the suspended element. This movement 
causes the recording pen K to move across the chart L, against the restrain- 
ing action of the control springs E, which tend to return the pen to zero 
position. The turning or actuating force of the armature is thus balanced 
against the coercive force of the control springs and their point of balance 
is a measure of the current flowing through the coils- 



Westing-house Graphic Recording* meters. 

Figure 50 illustrates the Westinghouse " Relay Type " Graphic Recording 
Meters. The meters are made as voltmeters, ammeters, single-phase and 
polyphase wattmeters, power factor and frequency meters. 



1038 



ELECTRICITY METERS. 



Construction. — The construction of a voltmeter is diagrammatically 
shown in Fig* 51 in which the various elements of the meter are designated 
as follows: 




Fig. 50. Westinghouse Graphic Recording Voltmeter With Indi- 
cating Dial. 




n ^TsfT 



Fio. 51. Diagrammatic Sketch of Westinghouse Graphic Voltmeter. 



WESTINGHOUSE GRAPHIC RECORDING METERS. 1039 



A— B — C— D = Fixed coils. 

E — F = Movable coils mounted on supporting structure pivoted 

at G. 
G = Pivoted support of E — F. 
H = Upper adjustable relay contact. 
I = Lower adjustable relay contact. 
J = Movable relay contact attached to movable element E— 

F. 
K = Pen actuating electromagnet (left hand). 
K' = Iron core of K. 

L = Pen actuating electromagnet (right hand). 
1/ = Iron core of L. 
M = Arm supporting iron cores pivoted at N and connecting 

O by pin bearing P. 
N = Pivoted bearing for M. 
O = Pen arm connected to M by pin bearing P and provided 

with guide slot at upper end which bears on stationary 

guide pin R. 
P = Pin bearing connecting M and O. 
R = Stationary guide pin for O. 

S = Recording pen arranged to pass across a suitable mov- 
ing record paper T. 
U = Helical spring connecting movable coil system and 

movable pivoted supporting arm M. 

Action of IJIeters. — The system of fixed and measuring coils is so 
arranged that when current flows through them the left-hand coil E is re- 
pelled by A and attracted by B, the right-hand coil F being repelled by D 
and attracted by C. Assuming the recording pen to be at zero position on 
the chart and connection made to relay and measuring circuits through 
binding posts Nos. 1, 2, 3 and 4, it will be seen that the movable system 
will take up a position which will force contact J against contact I. A circuit 
will thus be completed through the right-hand solenoid L and the electro- 
magnetic attraction will cause the core L' to move downward, which move- 
ment will turn M about its axis and through its connection with O cause the 
pen to move across the chart toward full scale position. This movement 
of M places tension on the spring U and continues increasing this tension 
until the core has travelled a sufficient distance to place such a tension on 
U that it balances the torque of the movable measuring system E — F and 
draws the contact J away from I. 

The entire moving system, including solenoids, pen arm and measuring 
coils remains in the position last assumed when the " relay " circuit was 
broken and the pen continues to draw a line which represents the voltage 
current or wattage values as the case may be. 



< 



CroVERNfilElirT i 

5H OFFICIAL 1 



Revised by Charles Thom! 

In this chapter only the instruments used in telegraphy will be noticed ; 
and these, with their connections, in theoretical diagrams only. For the 
various details, whose presentation would defeat the purpose of clearness 
in this compilation, readers are referred to various works on telegraphy. 
Lines, batteries, etc., are each treated in other chapters. 

AMERICAN, or CLOSED CII1CUIT METHOD, 

The following diagram shows the connections of the Morse system oi 
single telegraphy, as used in the United States. The terminal stations only 
are shown, and in one case the local circuit is omitted. Several interme- 




LINE TO TERMINAL 



LOCAL BATTERY 



— Wvv^~ -n 



± 



LINE TO EARTH OR 
TO RETURN WIRE 



Fig. l. 

diate stations (in practice 25 is not unusual) may be cut in on one circuit ; 
all the instruments working in unison, in response to one key only. 

In Fig. 1 at either end is a key which, when open, allows the now un- 
attracted armatures to be withdrawn by the retractile spring, S. Closing 
the key restores the current to the relays, attracts the armatures to the 
front stop ; the local circuit through the relay points is closed, and the 
signal is heard on the sounder. The attracting force of spring, S, is less than 
that of the relay cores as energized by the current from the battery used 
for a given circuit. It can, by "pulling up " on the spring, be made greater ; 
in which case the given current is ineffective to close the relays, and if the 
tension of spring, S, is maintained, battery must be added to close the relays. 
It is possible, therefore, by means of spring, S, to make a comparatively 
weak current ineffective to close the relay points. The significance of this 
will appear later in connection with the quadruplex. 



Ein<>PEi\, or OPE\ CIRCUIT MFTlf 4»1>. 

The following diagram shows the connections of one terminal station with 
the line connecting to the next. The ground plates may be dispensed with 
if a return wire from the next station is used, thus forming a metallic cir- 
cuit. 

This method of connecting Morse apparatus is used mostly in Europe, and 
has two advantages over the American method . 

a. The battery is not in circuit except when signals are being sent. 

b. When the key is closed and the current admitted to line, the coils of 
the relay are cut out of the circuit, thus lessening the hindrance to the flow 
of current. 

1040 



TELEGRAPHS 



1041 




LINE TO NEXT 8TATION KEY 



rT 



MAFN 
BATTERY 



LINE TO GROUND OR 
TO RETURN WIRE 



ISf 



Fig. 2. 



REPEATERS. 

In practical telegraphy, the high resistance of the line wire between the 
terminal stations, and imperfect insulation permitting leakage in damp 
weather, make it inexpedient to attempt to transmit signals over circuits 
whose lengths have not well-defined limits. But a circuit may be extended, 
and messages exchanged over longer distances by making the receiving 
instrument at the distant terminal of one circuit do the work of a transmit- 
ting key in the next. The apparatus used for this purpose is called a re- 
peater, and is usually automatic, in a sense which will appear later on. 

From among the scores of repeaters, selection must be made of repre 
sentative types, — the three in most general use 

Milliken Repeater. 

The following diagram illustrates the theory of the Milliken repeater, 
which is in general use in the United States and Canada. The essential 
feature of every form of automatic repeater is some device by which the 
circuit into which the sender is repeating not only opens when he opens, but 
closes when he closes. 



i 







1042 



TELEGRAPHY. 



In the diagram is represented the apparatus of a repeating station in 
which appear the instruments and three distinct circuits in duplicate, viz.: 
the east and west main line; east and west local (dotted); east and west 
extra local (dash and dot). Starting with both "east" and "west" keys 
closed and the line at rest, battery b', whose circuit (dash and dot) is com- 
plete through transmitter, T\ energizes extra magnet, E', attracts the pen- 
dent armature, P', leaving the upright armature free, the pendent armature, 
P, being similarly held by battery, b. In operation, the distant east opens 
his key, relay, E, opens, then transmitter, T, through whose tongue and post 
passes the west line, which opens, and would open relay, W, and therefore 
transmitter, T'\ but at the moment transmitter, T, opens, the extra local 
circuit (dash and dot) opens, releasing pendent armature, P, which is drawn 
by its spring against the upright armature holding closed the points of relay, 
W, and transmitter, T", and therefore the east line, which passes through 
its tongue and post. When the distant west breaks and sends, the action 
begins with the west relay instead of east, and follows the same course. 

Olieg-an Repeater. 

In repeaters for lines worked single, the characteristic is a device in the 
repeater which holds closed the main line on which the sending is being done, 



L& \ V AtLi > 




Fig. 4. 



while the distant relay on the second main line records that sending; the 
parts arranged to effect this result should act quickly on the "break" and 
a little slowly on the "make" of the main line current — " break " and 
"make" being the technical terms respectively for the opening and closing 
of the circuit. A form of repeater intended to effect in a high degree this 
result, called from its inventor the Ghegan, is shown in theory in the dia- 
gram, Fig. 4. The characteristic instrument is a transmitter having a 
second armature-bearing lever placed above the first one in such a position 
that one electromagnet serves to work both; the upper armature forms a 
back contact simultaneously with the opening of the transmitter, and it 
inclines to preserve the contact at U' until the regular local circuit (dotted) 
has been closed at the local points in relay E; the action is therefore quick 
or slow as occasion requires. As in the Milliken and Weiny-Phillips, there 
are three pairs of circuits; the main lines (solid black); the local circuits 
(dotted); and the shunt circuits (dot and dash). When relay W open it 



REPEATERS. 



1043 



releases the armature of transmitter T'\ through its tongue and post passes 
the west wire which opens, releasing the armature of relay E, and opening 
its local points. At the same time upper armature U' flies against its back 
contact and completes a shunt circuit by which battery b holds transmitter 
T closed; and the wire passing through its tongue and post is kept intact. 
Reverting to the position of the instruments in the diagram, the distant east 
is supposed to have opened his key. This opens relay W, which opens 
transmitter T' (both armatures); the drop in the lower armature opens 
the west main line, which opens relay E and its local points; but, as just 
explained, the circuit of battery b is now complete through the dot and 
dash lines, so that transmitter T is held closed and the east line is kept 
intact by its tongue against the stop. When the distant west breaks, the 
armature of relay E remains on its back stop, and, on the first downward 
stroke of the upper armature of transmitter T', the local circuit of trans- 
mitter T is broken, and at its tongue and post the east line opens. The 
east sender, thus warned, closes his key; the sender at the distant west takes 
the circuit, and action similar to that just described begins with relay E, and 
follows a like course. 

Weiny-Phillips Repeater. 

A theoretical diagram of the Weiny-Phillips repeater is given herewith. 
It is in general use by one of the principal telegraph companies, and is 



.!!,. 







Fig. 5. 



introduced here because it involves the principle of differentiation in mag- 
net coils, which plays so important a part in duplex telegraphy. As in the 
Milliken, there are three distinct circuits in duplicate; and in the diagrams 
the parts performing like functions in the two types of repeaters are simi- 
larly lettered. The connections and functions of the main line (solid black) 
circuits and of local (dotted) circuits are identical with those of the Milli- 
ken. But instead of the extra magnets and pendent armature of the latter, 
we have a tubular iron shell enclosing a straight iron core and its windings, 
the combination of shell and straight core performing the same functions 
as the usual horse-shoe core. The turns of wire around the core of the 
extra magnetare equally divided, and the current traverses the two halves 
in opposite directions. Such a core is said to be differentially wound, be- 
cause the core is energized by the difference in strength of the currents in 
the coilsj but when the coils are equal in resistance, the equal currents, 
passing in opposite directions around the core, neutralize each other. If 
one of the coils is opened, the core at once becomes a magnet capable of 
holding the armature at the moment when, the repeater in operation, the 
*'east" station opens his key, opening relay E\ then transmitter T; then 



1044 



TELEGRAPHY. 



opening the "west" wire, which would open relay W, transmitter T r , and 
therefore the east wire; but the opening of transmitter T' is prevented by 
the energizing at the critical moment of core ~W\ one coil of which is opened 
when transmitter T opens. When the distant west breaks and sends, the 
action begins with the west relay instead of the east, and follows the same 
course. 

Duplex Telegraphy. 

That method of telegraphy by which messages can be sent and received 
over one wire at the same time is called duplex; and the system in general 
use, known as the polar duplex, is illustrated in the accompanying diagram. 
In single telegraphy all the relays in the circuit, including the home one, 
respond to the movements of the key; the duplex system implies a home 
relay and sounder unresponsive, but a distant relay responsive to the move- 
ments of the home key; and this result is effected by a differential arrange- 
ment of magnet coils, of which the extra magnet coils in the Weiny-Phillips 
repeater furnished an example. A current dividing between two coils and 
their connecting wires of equal resistance will divide equally, and passing 
round the cores, will produce no magnetic effect in them. This condition 
is established when the resistance of the wire marked -*r> «■— in the diagram 



WEST 




EAS- 



THEORETICAL DIAGRAM OF POLAR DUPLEX 

BALANCING SWITCH OMITTED 

Fig. 6. 

is balanced by the resistance of a set of adjustable coils in a rheostat marked 
R. This is called the ohmic balance (from ohm, the unit of resistance); and 
the static balance is effected by neutralizing the static discharge on long 
lines by means of an adjustable condenser C, and retardation coil r, shunt- 
ing the rheostat as shown. In the single line relay the movement of the 
armature is effected by the help of a retractile spring in combination with 
alternating conditions of current and no current on the line. In the polar 
relay the spring is dispensed with, and the backward movement of the arm- 
ature is effected, not by a spring, but by means of a current in a direction 
opposite to that which determined the forward movement. This reversal 
of the direction of the current is effected by means of a pole-changer, PC, 
whose lever, T, connected with the main and artificial lines, makes contact, 
by means of a local circuit and key, K. with the zinc ( — ) and copper ( -+• ) 
terminal of a battery alternately. The usage in practice is zinc to the line 
when the key is closed; copper, when open. The law for the production of 
magnetic poles by a current is this: When a core is looked at "end on," 






EEPEATERS. 1045 

A current passing round it in the direction of the hands of a clock produces 
south-seeking magnetism, S; in the opposite direction, north-seeking mag- 
netism, marked N. A springless armature, permanently magnetized and 
pivoted, as shown in the drawing, will, if its free end is placed between S and 
N magnetic poles, be moved in obedience to the well-known law that like 
poles repel, while unlike poles attract each other. The "east" and "west" 
terminal is each a duplicate of the other m every respect; and a description 
of the operation at one terminal will answer for both. 

Under the conditions shown, the keys are open; and the batteries, which 
have the same E.M.F., oppose their copper ( + ) poles to each other, so that 
no current flows in the main line. But in the artificial line the current 
flows round the core in such direction as, according to the rule just given, 
to produce N and S polarities as marked, opening the sounder circuits at 
both terminals. If, by means of key, K', the pole-changer, PC, of "east" 
station is closed, the connections of battery, B', are changed; it is said to 
be reversed; and it now adds its E.M.F. to that of battery B, the current 
flowing in a direction from "west" to "east"; i.e., from copper to zinc. 
But the current in the main line is to that in the artificial as 2 to 1; and if 
the relative strength of the resultant magnetic poles is represented by small 
type for that produced by the current in the artificial line, and by large type 
for the main, the magnetic conditions can be graphically shown, as they are 
produced on each side of the permanently magnetized armatures marked 
(N) and (N'). In relay, PR', it is Sn (N') sN, causing it to remain open; in 
relay PR it has changed to Ns (N) nS — just the reverse of that shown in 
the diagram — the relay therefore closes, and the sounder also. If key, K, 
of the west station is closed at the same time, the batteries are again placed 
in opposition, but with zinc ( — ) poles to the line, instead of, as in the first 
instance, copper ( + ) poles. The result is no current on the main line; but 
the current in the artificial lines, flowing in the direction from the ground 
(whose potential is 0) to the zinc ( — ) of the batteries, the magnetic condi- 
tion at "east" station is represented by n (N') s, which closes relay, PR'; 
and at "west" station by n (N) s, which closes relay PR. The conditions 
necessary to duplex work, viz., that the movement of key, K', should have 
no effect on relay, PR', but should operate the distant relay, PR, are thus 
fulfilled, and the transmssion of messages in opposite directions at the same 
time is made practicable. In the case of the Wheatstone Automatic duplex 
this exchange goes on at high rate of speed, the maximum rate being 250 
words a minute. 

There have already been traced out the magnetic poles formed in the 
inside ends of the relay cores as the result of three possible combinations of 
current: (1) copper to line at each end; (2) zinc at east, copper at west end; 
(3) zinc to line at each end. 

One other possible combination remains to be traced out with reference 
to the poles formed; it is shown in Fig. 7, where the duplex is represented 
in a form more nearly approaching that which obtains in practice. At the 
west, or Pittsburg end, zinc is to the line; at the east, or New Yprk end, it is 
copper; the effect on the distant relay in each case is indicated in the draw- 
ing. For the sake of clearness the local systems are omitted ; at each terminal 
the artificial circuit is represented by a dotted line; the main line by solid 
black; the relays with their windings are shown in a manner fitted for tracing 
the magnetic effects. Representing the polarity of the armatures by (N) 
and OS), and the magnetic condition of the cores in the manner adopted 
in the preceding paragraph, it must be understood that the point of view 
is midway between the cores. The direction of the current on the main 
line in this diagram is from New York to Pittsburg. At the New York end 
the direction of the current in the artificial line is from the battery to the 
ground; at the Pittsburg end the current sets in from the ground to the zinc 
pole of the dynamo. In the Pittsburg relay the magnetic conditions, begin- 
ning with the lowest core, are Ns (N) nS; the large letters are the poles 
produced by the main line current; the small are those resulting from the 
current in the artificial line whose direction is from ground to dynamo; the 
armature is drawn upward and the relay opens, as shown. In the New 
York relay, the magnetic conditions (lower core first) are Ns (S) nS; the 
armature is drawn down and the local points closed. 

Otner details of the duplex are apparent on examination of the diagram. 
The two boxes with disks on the top are rheostats; each contains a number 
of co ; ls in series for making the resistance of the artificial line equal to that 



1046 



TELEGRAPHY. 



of the main. Under the rheostats are the condensers for eliminating the 
effects on the relay of the static discharge of the line. At the New York 
end is a chemical battery with the old style of pole changer; when open, as 
shown, it sends copper to the line, and puts zinc to the ground; when closed 
it puts zinc to line and copper to ground. At the Pittsburg end is shown 
an entirely different arrangement; it is the one now almost universally in 
use. Two dynamos furnish the current; the positive pole of one is grounded; 




Fig. 7. 



the other pole is led through a safety lamp to a cut-off switch, thence to the 
pole changer which sends zinc to the line when closed. Of the other dynamo 
the negative pole is grounded; the copper current goes to the right-hand 
post of the pole changer, which is very much simpler in form than the old 
style. The balancing switches, omitted from Fig. 6, are shown marked A 
and F; by means of these when the lever, say F, is thrown to the right, the 
main line wire i r detached from the pole changer and passes through a 
compensating resistance to the ground. 



REPEATERS. 



1047 



Duplex XiOop System. 

For many years after the introduction of the duplex and quadruplex 
the number of lines operated by those systems was small; but with im- 
provements in the material for wires and in line construction the number 
gradually increased until now nearly one half the wires of the two leading 
companies are utilized for one system or the other; and of the wires thus 
operated the working sets, to the extent of nearly one half, are assembled in 
main offices, and the wires themselves are worked, by what are called loops, 
from branch offices located mostly in the different exchanges. The appara- 
tus and connections by which the service of the duplex is extended to a 
branch are therefore an essential part of multiplex telegraphy. Fig. 8 is a 
diagram of the duplex loop system; the places of polar relay, pole changer 
and rheostat are indicated ; the main line connections shown in Figs. 6 and 7 
are omitted; and the local connections which are entirely omitted from 




DUPLEX LOOP 



Fig. 8. 



Fig. 7 are here inserted; so that Figs. 7 and 8 combined give a representa- 
tion of the working duplex. The polar relay controls the local circuit, 
passing through its points; the thumbscrews mark the joining of the office 
wires with those of the instrument; the electromagnet of the pole changer is 
controlled by means of two keys whose connecting wires join those of the 
electromagnet at the thumbscrews. A sounder, a six-point switch, a three- 
point switch, two lamps, and a 23 -volt dynamo complete the outfit for the 
main office. The current is led first to the three-point switch where it 
divides; one circuit, called the receiving side, may be traced (dotted line) 
through the points of the relay, through the sounder, to a lever in the six- 
point switch which, if turned to the right, conducts the current through a 
lamp to the ground. The other circuit, called the sending side, may be 
traced (solid line) through the magnet of the pole changer, through two 
keys, thence to a lever in the six-point switch which, turned to the right, 
similarly conducts the current through a lamp to the ground. There are 
therefore two grounded circuits, with connections as described, the current 
for which and for many like circuits is supplied by one dynamo. In the 
six-point switch are shown other two points; to one, marked M, is con- 
nected a wire extending to a distant branch office, through a sounder there- 
in, thence to the ground; to the other point, marked N, is connected a wire 
similarly extended through a sounder and key, thence to the ground. 
These connections completed, the levers of the six-point switch may be 
turned from right to left; the use of the duplex is then extended to the 
branch office; the polar relay works the sounders in both main and branch 



1048 



TELEGRAPHY. 



office; the key in the branch controls the electromagnet of the pole changer 
in the main office. The lamps A and B are in the main office local circuits, 
and compensate severally for the resistance of the two extensions when the 
loop is cut out. 

Half-Atkinson Repeater. 

The description of the duplex local (office and branch) system prepares 
the way for an interesting form of repeater by means of which the offices on 
a single wire of considerable length may repeat into, i.e., alternately send 
and receive on, a duplex wire or one side of a quadruplex. This apparatus 




Fio. 9. 



REPEATERS. 1049 

is named by prefixing the word "half" to whatever form of single line re- 
peater is used; e.g., half-Milliken, or half-Ghegan. To present as many 
different forms of repeaters as possible within the limits of this article, the 
diagram (Fig. 9) shows a half -Atkinson. In the upper right-hand corner is 
represented in skeleton form the duplex local system just described, to- 
gether with the jack in the loop switch for the placing of the repeater wedge. 
The apparatus of the repeater is seen to be a transmitter in the lower left 
corner, a common relay of 150 ohms resistance, two sounders, two keys, 
lamps, and a small dynamo. In the lower right corner is a jack to which 
on one side is connected the single line to distant points; on the other side 
is the main battery. With the wedge, as indicated, inserted in the jack, the 
main line circuit can be traced from the battery MB through the post and 
tongue of the transmitter, through the key and magnet coils of the relay, 
thence back to the jack and main line "out." 

In addition to the main line circuit there are four others; two of them are 
extensions of the 23-volt system of the duplex; of these one has in circuit a 
pole changer, lamp, sounder, and the local points of the common relay, and 
terminates in a ground; this arrangement places the pole changer in the 
control of the common relay. The other circuit has within it the local points 
of the polar relay, lamp, the electromagnet of the transmitter, and termi- 
nates in a ground; this arrangement places the transmitter (and the single 
line which passes through its post and tongue) in the control of the local 
points of the polar relay. Of the local circuits of the repeater proper, one 
(marked dot and dash) extends from one pole of a 7-volt dynamo through 
the lower post and lever of the transmitter, through the coils of a repeat- 
ing sounder RS; thence back to the other pole of the dynamo; another 
circuit (dotted) runs through the lever and back stop of RS, making con- 
nection, as shown, with the local points of the common relay. On the base 
of the relay the connecting posts on the right join the coils of the relay with 
the main line wires; the posts on the left connect with the local points of the 
relay. When the transmitter is open the sounder RS is open; the lever 
makes contact on the back stop, and completes a circuit in which is the 
electromagnet of the pole changer. 

Suppose all the circuits closed and ready for work. When a distant 
office on the* single line writes, he operates the relay through whose local 
points passes the pole changer circuit; he controls the pole changer and, 
therefore, the relay at the distant end of the duplex. When the distant 
office on the duplex writes, he operates the polar relay whose local points 
control the electromagnet of transmitter T, through whose tongue and post 
passes the single line. He thus controls every relay on the single line cir- 
cuit; the response of the pole changer to his own sending (which it is the 
purpose of the repeater to avoid) is prevented by the bridging of the local 
points of the common relay through the lever and back stop of RS. The 
distant station on the duplex may thus communicate with any office on the 
single line, and conversely. 

The action of this repeater can be utilized to repeat from one single line 
into another; when so arranged it is known as the Atkinson repeater, and 
it is the standard of one of the leading companies. 

Duplex Repeater. 

In wires worked in the duplex or quadruplex system, the static capacity 
of the wire, which plays little if any part in the operation of circuits by the 
single method, places a limit on the length of the continuous circuit. But 
the distance between working stations can be greatly extended by the use 
of repeaters in which, by an arrangement perfectly simple, the pole changer 
of a second circuit is controlled by the relay points of the first. The long- 
est regular circuit in the United States is that worked between New York 
and San Francisco, with six repeaters. 

The work of the repeater in this and many other duplex circuits has been 
facilitated by the recent introduction of the J. C. Barclay pole-changing 
relay. It consists of a polar relay so constructed that two armatures, in- 
sulated one from the other, move on a common arbor; one armature con- 
trols the local circuits; to the other is attached the main line which makes 
contact on front and back stop with the poles of the battery; it is thus a 
polar relay and pole changer combined. 



1050 



TELEGRAPHY. 



The Stearns Duplex. 

The operation of differential relays like M in the diagram of the quadru- 
plex, by alternations of "no battery" and "battery," is the principle of 
the Stearns duplex, which, as the first condenser-using, and therefore static- 
eliminating duplex in the world, has a certain historic interest. In Febru- 
ary, 1868, there were in use by the Franklin Telegraph Company a duplex 
set New York to Philadelphia, and another to Boston; and in August, 1871, 
by the Western Union Telegraph Company, a duplex, New York to Albany 
— all without condensers. In March, 1872, the Stearns duplex, with con- 
denser, went into operation between New York and Chicago, but it has been 
superseded by the polar system. 

Reverting to the diagram, the pole changer with its adjuncts, and the 
polar relay of the quadruplex, are omitted; one pole of the battery is 



m 



s |_^VWA 



WEST 






d^H'ltm'I'b^ ^^ 




STEARNS DUPLEX 

(ONE TERMINAL) 



Fig. 10. 



grounded, and the lever of transmitter, T, is grounded through a resistance 
equal to that of battery, B. This grounds the line through tongue, t, and 
leaves the battery open at the post, P. The "east " station (not shown) is a 
duplicate of the "west," and the control of relay, D, by the distant trans- 
mitter, T' t may be traced as follows. Suppose distant transmitter, T', sends 
copper to the line when closed, the current dividing equally between the 
main and artificial lines in distant relay, D', has no effect upon it; but at the 
west station there is no current in the artificial line in relay, D, so that 
the current in the main line closes it. Open the key, K', and the line is 
grounded through the lever of transmitter, T'\ battery B' is open, and there 
being no current on the wire, relay, D, is open in response to the opening of 
distant key, K'. Let transmitter, T, now be closed, and trace the control of 
relay, D, by the distant key, K*. The current, which now flows from the 
ground through the lever of open transmitter, T' ', to the zinc pole of battery, 
B, is neutralized in relay, D, by an equal current flowing from the ground 
through its artificial line in the opposite direction around its cores, so 
that relay, D, remains open. Now close distant transmitter, T', and the 
current in the artificial line (i.e., through the rheostat, R) of relay D is over- 
powered as to its effects by a current on the main line of twice its strength, 
and relay D is closed. It is thus shown to be controlled by the distant key, 
K\ irrespective of the position of home key, K, and the conditions necessary 
to duplex telegraphy are met. 



QUADRUPLEX. 



1051 



The quadruplex system of telegraphy allows of two messages being sent 
in either direction, over the same wire, and at the same time. In theory it 
is an arrangement of two duplexes, so different in principle as to permit 
of their combination for the pin-pose designated. If the accompanying 
diagram of the quadruplex is examined, there will be noticed in it the 




( 



pole changer, polar relay, and all the apparatus of the polar duplex. The 
polar relay, K, at the "east" station will respond to signals sent by the 
pole changer, at the "west" in the manner described in the paragraph on 
the Polar Duplex, so long as the working minimum of current is main- 
tained. This working minimum can be doubled, trebled, or quadrupled 
without appreciable difference to the polar relays. In the paragraph on 
Single Telegraphy, the operation of the single relay, fitted with a retractile 



1052 TELEGRAPHY. 



spring, was effected by opening and closing the key; or, in other words, by 
alternating periods of "no current" and "current" on the wire. It was 
further stated, in anticipation of its introduction at this point, that the 
spring could be so adjusted that a weak current, though flowing all the time 
through the coils, would not close it. To effect the closing an increase 
of battery, and therefore of current strength, is necessary, so that the relay, 
instead of, as in the first instance, responding to alternating periods of "no 
current" and "current" could be operated by alternating periods of "weak 
current" and "strong." 

The diagram, Fig. 11, illustrating the theory of the quadruplex, will be 
seen on examination to be a combination of the polar and Stearns duplexes, 
each of which has already been described. The operation of the Stearns 
duplex in combination differs from that described in connection with Fig. 10, 
only in that there is always on the wire a minimum of current sufficient to 
operate the polar side of the quadruplex ; the neutral relays M and M f , 
identical with that marked D in Fig. 10, are operated by alternating periods 
of "weak" current and "strong," after the manner of the Stearns. In 
practice the weak current is technically called the "short end"; the strong, 
the "long end"; and the diagram shows how, with different methods of 
current production, viz., the chemical battery and the dynamo, the pro- 
portioning of the current in the ratio usually of 1 to 3 is effected. The 
clock-face pole changer operates, as already described, to send when open 
(see diagram) copper to line and zinc to the ground; when closed, zinc to 
the line and copper to the ground. If the connections of transmitter T 
are traced it will be seen to admit to the pole changer one third of the battery 
when open, and the entire battery when closed; in other words, the move- 
ments of the transmitter determine a "short" or "long" end to line. At 
the left-hand terminal transmitter D effects a like result but by different 
means. In connection with the transmitter are two sets of resistance coils, 
so proportioned that when transmitter D is closed all the current from the 
dynamo goes to line; when open, one third of it goes to the line and two 
thirds is "leaked " off to the ground. One pole of each dynamo is grounded; 
the other is connected through a lamp to the pole changer in such a way 
that the rule "zinc to the line when closed, copper when open" holds good. 
The main line is shown in solid black; the artificial in dotted lines; the rheo- 
stats and condensers with their retardation coils marked RC are identical in 
principle with those shown in the polar duplex. In the diagram transmit- 
ter D with its companion pole changer is closed; transmitter T with its 
pole changer is open; the effect of these conditions is respectively to close 
relays M' and K, and to open relays M and F; the reasons for these results 
have already been set forth in detail in connection with the polar and 
Stearns duplexes, so that it is not necessary to repeat them here. In short, 
there is in the quadruplex a pair of polar relays which respond to changes 
in the direction, not in the strength of the current; and a pair of neutral 
relays, which respond to changes in the strength^ not in the direction of the 
current. The diagram shows the apparatus in its simplest form; there are 
a number of details in connection with its operation, the complete connec- 
tions for which are rather too complicated for this book. On page 199 of 
Mavers's American Telegraphy will be found a diagram embodying the full 
scheme of connections; and Thorn and Jones' Telegraphic Connections con- 
tains diagrams and detailed descriptions of the systems in general use. 



TELEGRAPH (ODES. 

IVIorse, used in the United States and Canada. 
Continental, used in Europe and elsewhere. 
Phillips, used in the United States for "press" work. 

Dash = 2 dots. 

Long dash =■= 4 dots. 

Space between elements of a letter = 1 dot. 

Space between letters of a word = 2 dots. 

Interval in spaced letters «= 2 dots. 

Space between words = 3 dots. 



TELEGRAPH CODES. 



1053 



A 

B 

e 

D 

E 
F 
G 
H 

I 

J 

K 

L 

M 

N 

O 

P 

a 

s 

T 
U 
V 

w 

X 

Y 
Z 
& 



betters. 

Morse, 



Continental, 



Humeral*. 

Morse. 



Continental. 



Punctuation, etc. 

Morse. Continental. 



. Period 

: Colon 

: — Colon dash 

; Semicolon 

, Comma 

? Interrogation 

! Exclamation 

Fraction line 

— Dash 

- Hyphen 
Apostrophe 

£ Pound Sterling 
/ Shilling mark 
$ Dollar mark 
d Pence 



1054 TELEGRAPHY. 

Morse, Continental 

Capitalized letter 
Colon followed ) 
by quotation:" ) 
c cents 
. Decimal point 

If Paragraph 

Italics or underline - 

[] Brackets ) m _ _ 

" " Quotation I 

marks. 
Quotation within ) 

a quotation J 



Phillips. 



Period 

Colon 

— Colon dash 

Semicolon 
, Comma 
? Interrogation 
! Exclamation 
Fraction line 

— Dash 

- Hyphen 

' Apostrophe 

£ Pound Sterling 

/ Shilling mark 

$ Dollar mark 

d Pence 

Capitalized letter 

Colon followed by quo- 
tation: M 

c cents 

. Decimal point 

If Paragraph 

Italics or underline 

() Parentheses 

[] Brackets 
" Quotation marks 

Quotation within a ) 
quotation "' ; " ) 



Abbreviations in Common "Use. 

Min. Minute. Bn. Been. 

Msgr. Messenger. Bat. Battery. 

Msk. Mistake. Bbl. Barrel. 

No. Number. Col. Collect. 

Ntg. Nothing. Ck. Check. 

N.M. No more. Co. Company. 

O.K. All right. D.H. Free. 

Ofs. Office. Ex. Express. 

Opr. Operator. Frt. Freight. 

Sig. Signature. Fr. From. 

Pd. Paid. G.A. Go ahead. 

Qk. Quick. P.O. Post Office. 

G.B.A. Give better address. R.R. Repeat. 



WIRELESS TELEGRAPHY.* 

Revised by Frederick K. Vreeland. 

In consequence of the rapid changes which the art of wireless telegraphy 
is undergoing, it is impracticable to give here more than an outline of the 
principles involved, with descriptions of a few typical forms of apparatus. 
For further details the reader is referred to the more complete works on the 
subject. 

Wireless Telegraphy, as it is practiced to-day, is based upon the 
fact that an electrical oscillating system, when suitably proportioned, may 
become the source of electromagnetic waves, which radiate through space 
like light waves, and which have the power of exciting oscillations in a 
conductor on which they impinge. 

Electrical Oscillations. — The essential elements of an oscillating 
system are a capacity and an inductance, and means for charging the capacity 

and allowing it to discharge through the in- 
ductance. Fig. 1 represents such a system, 
in which the capacity C may be a Leyden 
jar, and the inductance L a coil of few turns 
of coarse wire. A is a pair of knobs sepa- 
rated by an air gap, and /an induction coil. 
When the coil I is set in operation the jar C 
is charged until its potential is sufficient to 
break down the air gap G. When a spark 
occurs, the air gap becomes a good conduc- 
tor, and the jar discharges through the 
inductance L. 

If the ohmic resistance is not too high 
the discharge is oscillatory, and the current 
surges through the circuit with a frequency 




( 



N 



2rr V LC 4 



?1 



or, if R is small, 



Fig. 1. Closed Oscillating Circuit 
Operated by an Induction 
Coil. 

where 



1 



2n VLC 



N = Frequency in cycles per second. 
L = Inductance in henrys. 
C = Capacity in farads. 
R = Resistance in ohms. 

*■' R ^ ^ \/ 7, t AT becomes imaginary, and the discharge is undirectional. 

The frequency is usually very high; for example, if C = .005 microfarad 
and L = .02 millihenry, — figures which roughly represent the case cited, — 
N will be 500,000 cycles per second. 

Xlectromag-iietic Waves. — Such a closed circuit oscillator may 
produce very powerful inductive effects, but it gives off little energy in 
radiation. It may be converted into a good radiator by separating the con- 
ductors of the capacity, so that the electrostatic field which lies between 



* Many of the illustrations for this chapter are taken from Maxwell's 
Theory and Wireless Telegraphy, by L. Poincare' and Frederick K. Vreeland, 
through the courtesy of the McGraw Publishing Company. 

1055 



1056 



WIRELESS TELEGRAPHY, 



them may spread out into space instead of being concentrated in the glass of 
the jar. 

Figure 2 shows an open circuit oscillator as used by Hertz in the discovery of 
electromagnetic waves in space. Here the capacity between the spheres Si 
and S2, and the inductance of the short rod joining them, are both small, and 
the frequency is correspondingly high, say 50,000,000 cycles per second. 




Fig. 2. Open Circuit " Dumb-bell " Oscillator, showing Electrostatic 
Lines at the Moment Before the Air-gap Breaks Down. 

The high frequency combined with the open character of the circuit makes 
this oscillator a good radiator. The dotted lines (Fig. 2) represent the 
electrostatic field just before the air gap breaks down. When the spark 
occurs and the oscillations commence, these electrostatic lines shrink back 

Fig. 3. Field surrounding a dumb-bell 
oscillator when in operation. At the 
moment illustrated the spheres are 
discharging and the lines within the 
large circle show the beginning of a half 
wave about to be detached. Outside 
the circle the preceding half wave is 
started on its journey through space. 
The oscillator is shown, greatly re- 
duced, within the small circle. (After 
Hertz.) 

into the oscillator; but the shrinking is so sudden that portions of them are 
snapped off, as it were, forming closed loops (Fig. 3), which go off into space 
with the velocity of light (300,000 kilometers per second) expanding verti- 
cally as they go, and carrying energy with them. This is repeated in each 
hali oscillation, until all the energy is radiated or wasted in internal losses. 




INTRODUCTION. 



1057 



The rapidly moving electrostatic lines carry with them a magnetic field, 
whose lines of force form coaxial circles with centers in the axis of the oscil- 
lator, expanding continuously as ripples expand about a pebble thrown into 
the water. Their relation to the electrostatic lines is shown in Fig. 4. 

This combination of electrostatic and magnetic fields, traveling outward 
with the velocity of light, constitutes an electromagnetic wave. When 
such a wave encounters a 
nonconducting obstacle it 
passes through it without 
interference, but if the ob- 
stacle be a conductor.the mag- 
netic lines cutting it induce 
currents which absorb energy 
from the wave. If the ob- 
stacle be large, such as a sheet 
of metal, the wave is com- 
pletely cut off and reflected 
as from a mirror; if the ob- 
stacle be a wire parallel to the 
axis of the oscillator, it be- 
comes the seat of secondary 
oscillations, like those in the 
oscillator, but weaker. Any 
instrument capable of detect- 
ing these oscillations may be 
used as the receiver of a 
wireless telegraph system, of 
which the oscillator is the 
transmitter. 

The Antenna. — The 
Hertzian oscillator shown in 
Fig. 2 is operative only over 
short distances. The energy of the waves is limited by the small capacity 
of the oscillator, and waves of such high frequency are readily absorbed 
by obstacles. In actual practice the oscillator takes the form of a 
vertical wire or antenna, supported by a mast, and grounded at the lower 
end through a spark gap (Fig. 5). 




Fig. 4. A Portion of the Spherical Wave- 
front proceeding from an Oscillator. The 
Full Lines Indicate the Magnetic Force, 
the Broken Lines the Electric Force. The 
Direction of Propagation is Perpendicular 
to Both of these, and is therefore Radial. 



i 




Fig. 5. Transmitter with 
Simple Antenna. 



Fig. 6. Receiver with Simple 
Antenna and Coherer. 



This is equivalent to half of a Hertzian oscillator, the lower half being 
removed and replaced by the earth. The capacity and inductance are dis- 
tributed along the whole length of the wire, and the law of their distribution 
is such that the wave-length is four times the height of the antenna. Thus 



1058 



WIRELESS TELEGRAPHY. 



with a wire 50 meters high the wave-length would be 200 meters, and the 



300000^000 
200 



= 1,500,000 



frequency = velocity + wave-length, would be 

cycles per second. 

A free Hertzian oscillator emits free Hertzian waves, which travel through 

space like light. A grounded oscillator gives off grounded waves (Fig. 7). 

They are half waves, whose electrostatic lines, instead of being self-closed, 

terminate in the earth, to which they 
are inseparably bound. Instead of 
traveling always in straight lines, they 
must follow the contour of the con- 
ducting surface over which they slide, 
and so they may cross mountains or 
travel about the earth. 

In gliding over the conducting sur- 
face of the earth they are accompanied 
by alternating currents in the surface. 
These currents waste energy in over- 
coming the ohmic resistance of the 
surface, with the result of diminishing 
the intensity of the waves. For this 
reason the propagation is much better 
over water or moist ground than over 
dry or frozen ground whose resistance 
is high. 




#55 



Fig. 7. Propagation of Grounded 
Waves from an Antenna over a 
Curved Surface. 



A further cause of attenuation of the waves exists in the space through 
which they travel. When the sun is shining the air becomes ionized, in 
which state it is partially opaque to the waves and they are more or 
less absorbed. Where the distance of signaling is great the difference be- 
tween the strength of signals in the day and their strength at night is some- 
times very marked . 

With a grounded transmitter, a grounded receiver is used (Fig. 6). This 
is another vertical antenna A , with a detector C, connected in series near 
the ground. B is a battery and R a relay or telephonic receiver. 

The Coherer, — ODe of the best known detectors of electrical oscil- 
lations is the coherer. A typical form is shown in Fig. 8. T is a glass 
tube in which are two tightly fitting silver plugs, E and E', attached to 
leading-in wires. The ends of the plugs are about .5 millimeter apart, 




Fig. 8. Coherer — Longitudinal Cross Section. 



and the space between them contains a mixture of silver and nickel 
filings, with sometimes a trace of mercury. The tube is then exhausted 
and sealed. 

Normally, the filings lie loosely together, and present a high resistance. 
The coherer is practically open circuited, but under the influence of the 
electrical oscillations the filings cohere, and the resistance falls at once to a 
few hundred ohms. If the coherer be connected in circuit with a battery 
and a sensitive relay (Fig. 9), this drop in resistance will operate the relay 
and give a signal. 

The filings continue to cohere after the cessation of the impulse that 
affected them, but they may be separated by a mechanical shock. Or- 
dinarily an automatic tapper is arranged to strike the tube whenever the 
relay gives a signal, and so restore it to its sensitive condition, ready for the 
next impulse. 



SYNTONIC SIGNALING, 



1059 




Fig. 9. 



Arrangement of Coherer C with Battery B and Relay R 
Recording Instrument, and T an Automatic Tapper. 



/ is a 



A simple grounded antenna has a definite natural period of vibration, 
but its tendency to adhere to this period is weak, and it may execute forced 
vibrations over a wide range of frequencies. Thus a given receiving an- 
tenna will respond to the radiations of various sending antennae, with only 
a slight preference for radiations whose period is the same as its own. Such 
an antenna constitutes a simple "responsive" system, which is adapted to 
use on shipboard or between ships and shore, where it is desirable that 
any station may communicate with any other station in the vicinity. 

When a number of stations are so close together as to interfere with 
each other, a responsive system is not suitable, but the apparatus must be 
made selective, so that any given pair of stations may intercommunicate 
without interference from the others. The most usual way of securing 
selectivity is by applying the principle of Electrical Resonance or Syntony. 

An electrical oscillating circuit may be so constructed as to make it a 
stiff vibrator, i.e., the positiveness of its vibration period may be greatly 
increased, so that it will respond readily to vibrations having its own nat- 
ural period but will be little affected by impulses of a different period: just 
as a stretched string will respond to a sound to which it is tuned, but not to 
sounds of different pitch. 

Damping*. — The criterion of sharp resonance is a persistent oscillation in 
both transmitter and receiver. In the transmitter there is a certain initial 
supply of energy stored in the antenna or other charged condenser, and this 
energy is gradually expended in radiation or in resistance of the conductors 
and spark gap and other internal losses. The rate at which the stored 
energy is expended determines the "damping" or rate of decay of the 
oscillation. In the receiver, energy is received by the antenna and consumed 
in doing useful work in the detector, or wasted in ohmic and other losses. 
To secure a large resonant accumulation of energy, all these losses should 
be reduced to a minimum. In other words, the damping of both trans- 
mitter and receiver must be small. A simple antenna is a poor oscillator 
because its energy is radiated rapidly, and the amplitude of its oscillations 
decreased at a corresponding rate. The curve (Fig. 10) represents the 
strongly damped oscillation of a dumb-bell oscillator (Fig. 2) as determined 
byBjerknes. The amplitude falls to yo of its initial value after nine oscil- 
lations. The oscillation of a simple grounded antenna may decay even 
more rapidly still, and this is why sharp resonance is impossible between 
two such simple oscillating systems. 



1060 



WIRELESS TELEGRAPHY. 



A closed oscillating circuit (Fig. 1) may be made quite a persistent vi- 
brator, as little energy is lost in radiation, and the damping of the oscilla- 



Time-Hundred- 




.millionths of a second 



Fio. 10. Discharge Curve of Dumb-bell Oscillator. 



tions is due mainly to the ohmic resistance of the circuit, 
such a system is represented by the equation 



The oscillation of 



Q ■ 



Q p ^ y e 



■fit 



cos (yt + «). 



where 



t = time, 

Q = initial charge of condenser, when t = o, 
q = charge after time t t 



= 



R_ 
2L 



A /j_ _ JP 
y " \ LC 4L*' 



a = tan — - » 

y 

R being the resistance in ohms (or in absolute units). 
L being the inductance in henrys (or in absolute units). 
C being the capacity in farads (or in absolute units). 
The expression cos (yt ■+■ a ) determines the frequency of the oscillation, 

AT = ~- and is represented by a simple harmonic curve, while the ex- 

ponential factor, r 

e -iz' 

determines the damping, and is represented by the logarithmic curve shown 
in dotted lines in Fig. 10. 

For t = T, a complete period, the exponential term becomes 



which is the ratio of any two consecutive maxima. The exponent -r-j- T is 

the natural logarithm of this ratio, and is called the "logarithmic decre- 
ment." (According to the convention of some writers, the logarithmic 



SYNTONIC SIGNALING. 



1061 



decrement is defined as the logarithm of the ratio of two consecutive turn- 
ing points, and hence has half the above value.) 

/3 
In a persistent vibrator of high frequency the ratio — is small, and the 

equation may be written, 

~Pt cos yt. 



q = Qe' 



or 



■■ Q€ cos 



▼ LC 4L* u 



This form is more convenient than the complete equation, and is 
sufficiently accurate for practical purposes. 

Skin Cffect. — The value of R as here used is quite different from 
the resistance as measured by ordinary methods, owing to the fact that 
such rapidly oscillating currents are confined to a thin superficial layer on 
the outside of the conductor. The thickness in centimeters of the skin 

measured to the point where the current density is — of its value at the 

surface, is, 



'-Vb 



where <r = specific resistance of conductor, 
/a = permeability of conductor, 
N = frequency of oscillation, 
and the effective resistance of the skin is equivalent to the resistance for 
a continuous current of a shell whose thickness is, 



^-Vi 



V2 



&v*nN 



For copper <t = 1600 C. G. S. units, and fx = 1. If the frequency be 
3,000,000 ^ per second the effective thickness S' of the equivalent shell will 
be .0026 cm. or about .001 inch. 



r 



I 



CQ3 



y. 







Fig. 11. Antenna with 
Closed Oscillating Circuit 
Directly Connected. 



J»* cGP 



Fig. 12. Closed Oscillating 
Circuit Coupled to Antenna 
Through a Transformer. 



1062 



WIRELESS TELEGRAPHY. 



Syntonic Apparatus. — Two closed circuit oscillators may exhibit 
very sharp resonance — a slight variation in the capacity or the inductance 
of either circuit will throw them out of tune — but they cannot affect each 
other at any great distance owing to their poor radiating and absorbing 
powers. To make them available for signaling, they are coupled, each to 
an antenna. The coupling may be effected by a direct electrical connection 
across an inductance coil or auto-transformer as in Fig. 11, or through an 
air-core transformer PS (Fig. 12). Such a compound oscillating system 
combines the virtues of its two component parts. The closed oscillating 
circuit stores energy in its large-capacity condenser to maintain the oscilla- 
tion, and this energy is fed out slowly 
to the antenna, which radiates it into 
space. In the receiver, the process is 
reversed: the antenna absorbs energy 
from the passing wave train and com- 
municates it to the closed resonant 
circuit, which is tuned to respond to 
impulses of the desired frequency. 

To obtain the best results in both 
transmitter and receiver, the closed cir- 
cuits should be tuned to the same 
natural frequency as their respective 
antenna circuits. For this purpose a 
variable inductance L (Fig. 13) is often 
placed in the antenna circuit, and thus 
a given receiver or transmitter may be 
Fig. 13. Inductively Coupled tune + d . ^ , a T ar L et . y ^ f frequencies, irre- 
Transmitter with Tuning Coil in spective of the height of the antenna. 
Antenna Circuit. 




TJaAXSroLETTEMS. 

The simple antenna system of Figs. 5 and 6 has been almost entirely 
superseded by the compound oscillating system, even where selectivity is 
not important, because of the far greater intensity of radiation that may 
be obtained with the compound oscillator. With the simple antenna the 
energy of a wave train, such as that illustrated in Fig. 10, consists entirely 
of the energy which is stored up in the antenna at the moment the spark 
occurs. This energy depends upon the capacity of the antenna and the 
potential to which it is charged. As the voltage + hat may be successively 
used is limited and the capacity of an antenna is comparatively small, 
the energy of the wave train is not sufficient to carry it over a long dis- 
tance. Where a compound oscillator is used, however, the condensers may 
have a capacity many times as great as that of the antenna, and the power 
of the apparatus is greatly increased. 

A typical form of transmitter with compound oscillating circuit is shown 
in Fig. 13, when / is an induction coil controlled by a sending key and dis- 
charging across a spark-gap B. CPB is a closed oscillating circuit com- 
prising a battery of Leyden jars C and the primary P of an air-core 
transformer, whose secondary S is 
connected to the antenna A and to 
ground. Both primary and second- 
ary of this transformer consist of a 
few turns of stout copper wire^ or 
cable, and the whole is immersed in a 
vessel of oil. L is an additional in- 
ductance coil, whose number of turns 
may be varied, inserted in the 
antenna circuit to facilitate tuning. 
By varying this inductance and the 
capacity of the condenser C the two 
circuits may be tuned in unison with 

each other and with the receiving Fig. 14. Transmitter with A. O. bupply. 
apparatus. . . 

Transmitters with A. C. ftupply. — A more powerful form of 
transmitter is shown in Fig. 14. Here the power is derived from an A. C. 




TRANSMITTERS. 



1063 



generator D which feeds an ordinary A. C. transformer T wound for a second- 
ary voltage of about 20,000 volts and immersed in oil. This takes the place 
of the induction coil of Fig. 13 for feeding the oscillating circuit GCOC . The 
oscillating circuit is coupled to the antenna through a single coil L having 
adjustable terminals, which performs the double function of auto-trans- 
former and tuning coil. It thus serves the same purpose as the transformer 
PS and the inductance L of Fig. 13. 

If the alternator were directly coupled to the transformer shunted by a 
spark-gap the apparatus would not operate satisfactorily owing to its tend- 
ency to form a hot, low-frequency arc across the gap. As long as this arc 
continued it would be impossible to charge the condensers to a sufficient 
voltage to excite oscillations. To prevent this arcing a large adjustable 
self-induction L, is inserted in the primary circuit of the transformer. This 
chokes down any sudden rush of current when the air-gap breaks down 




W///V/ 



FlO. 15. High-power Transmitter. 



i 



and allows the arc to extinguish itself so that the condensers may be 
charged anew. When the apparatus is suitably adjusted it is possible to 
obtain several sparks to each alternation of the supply current. 

High-power Transmitters. — Where very intense radiation is 
required, as in transatlantic work, still more powerful apparatus is used, 
such as that shown in Fig. 15. The source of power does not directly 
excite the active oscillating circuit, but is used to set up low-frequency 
oscillations in a primary oscillating circuit, which acts as a secondary source 
of power at high voltage to supply the active circuit. D is an A. C. 
generator whose voltage is stepped up to, say, 20,000 volts by the trans- 
former To, R is a rotating arm geared to the shaft of the generator, and 
passing within sparking distance of two metallic sectors, Bo, B±. When 
the arm comes opposite the first sector, Bo, a spark leaps across and charges 
a large condenser, C t . When the arm reaches the second sector, B lt this 
condenser is discharged through the primary, P lf of an air-core transformer, 
T t . Oscillations are set up in the primary oscillating circuit CxBxPx, but 
they are of comparatively low frequency, owing to the large capacity and 
inductance of the circuit. They are stepped up to a very high voltage by 
the transformer, T t , and serve to charge ^the smaller condenser, C 2 , of the 
active oscillating circuit, C 2 GP 2 . This condenser discharges across the 
spark-gap G, and sets up a new series of oscillations, of the same high fre- 
quency as that of the antenna circuit, AS 2 , to which the circuit C 2 GP% 
is coupled by a second air-core transformer, T 2 . The large condenser, CV. is 
thus charged at a moderate voltage, and its energy is radiated at a suitable 
working frequency, which would be impracticable if the condenser were 
simply included in the working circuit in the usual way. 

Ungrounded Transmitters. — The distinctive feature of this system 



1064 



WIRELESS TELEGRAPHY. 



is the fact that the antenna is not grounded (Fig. 16), but is connected to a 
capacity area K, This is made in the form of a metal cylinder with rounded 




Fio. 16. Transmitter with Artificial Ground. 

ends, made in two parts which telescope one over'the other, so that its capac- 
ity may be varied. It forms with the earth a condenser, which serves the 
purpose of a ground connection. 



RECEIVERS. 

The principles which govern the design of a syntonic receiver are similar 
to those which obtain in the case of the transmitter, but their practical 
application is somewhat different. In the transmitter a considerable sup- 
ply of energy is stored in a charged condenser, and this energy takes the 
form of powerful oscillating currents in the transmitter circuits. These 
currents are surprisingly heavy — an induction coil fed by a few cells 
of storage battery may generate currents of several hundred amperes, 
representing an activity of many horse-power. To carry such currents 
efficiently heavy conductors are required, and circuits of large capacity and 
small inductance are desirable in order that the requisite energy may be 
handled at practicable voltages. In the receiver, however, the amount of 
energy received from the incoming waves is exceedingly small, and the 
currents induced are correspondingly feeble. Where a coherer — a 
potential-operated ^ device — is used for detecting the oscillations, the 
voltage applied at its terminals should be made as large as possible. Hence 
the oscillating circuits are made with small capacity and large inductance, 
and their ohmic resistance may be quite large without seriously increasing 
the damping of the oscillations. (See Fig. 17.) 

But where the sharpest selectivity is required it is of the utmost import- 
ance to make the resistance as small as possible so as to diminish the 
damping, for a strongly damped receiver circuit is not only incapable of 
sharp resonance, but it requires a close coupling to the antenna circuit to 
secure the necessary strength of signals. The sharpest resonance is secured 
with a loosely coupled system, for there the oscillating circuit is compara- 
tively free from the disturbing influence of the strongly damped antenna 
circuit; but loose coupling diminishes the intensity of the secondary 
oscillations, and requires a strongly resonant oscillating circuit to give 
readatle signals. Usually a compromise is required, and the closeness of 
coupling is made adjustable by varying the distance between the primary 
and secondary coils, so that loose coupling may be used when the sharpest 
selectivity is required, or stronger signals may be secured by bringing the 
coils in closer inductive relation. 

Coherer Receiver with Jigger. — This receiver (Fig. 17) is 
designed to give a high voltage at the coherer terminals. A is the receiving 
antenna, which is grounded through an inductance L and the primary J% t 
of a transformer of special construction, which is called a M jigger. " J 2 is 



RECEIVERS. 



1065 



the secondary of this transformer, to whose outer terminals the coherer T 
is connected. The secondary coil J 2 is broken in the middle and the inner 
terminals thus formed are connected to a condenser C, and also to the 
relay and recording apparatus. 

The peculiar construction of the jigger is shown in Fig. 17, which repre- 
sents half of the coil in longitudinal cross section, j is a glass tube on which 
is wound a single layer j t of primary winding. j 2 72 are the two halves of 
the secondary winding, which is represented diagrammatically, each of the 
zigzag lines on the diagram representing a layer of winding. The inner 
layer has the greatest number of turns, and the number of turns decreases in 
the successive layers to the last, which has only two or three turns, jz is 
the condenser, from which wires lead out to the relay and auxiliary appara- 




L g r — 'TOftRT* — 'w. 




Fig. 17. Coherer Receiver 
with Jigger. 



Fig. 18. 



Method of Winding 
Jigger. 



tus. The secondary winding has a large number of turns of fine wire, sind 
its distributed capacity and inductance are such that it has a natural period 
of vibration, when connected to the coherer, equal to that of the antenna 
circuit and of the incoming waves. It is thus, to a certain extent, syntonic 
in its action, and it has the further advantage of stepping-up the voltage 
of the receiver oscillations and thus increasing their effect on the coherer. 
As the capacity of a coherer is a rather uncertain and variable quantity, a 
condenser d is sometimes shunted across its terminals to make the appara' 
tus more definitely selective. 

.Receiver with J^ow-resistaitce Detector. — The peculiar ar' 
rangement of the last-described receiver is due to the practically open-cir- 
cuit character of the coherer. When low-resistance detectors are used the} 
may be inserted in series in a simple resonant circuit as shown in Fig. 19. 
Mis an air-core transformer whose primary coil is connected in series with 
the antenna, A. The secondary is connected in a closed oscillating circuit 
including the condenser C, which is preferably adjustable for purposes of 
tuning, the detector D and sometimes an additional inductance coil L. 
The transformer M is preferably a loosely coupled one, 
as the low-resistance character of the oscillating cir- 
cuit permits comparatively strong resonant currents 
to be induced by a feeble electromotive force. The 
coils are usually mounted so that the distance between 
them may be varied, to adjust the coefficient of coup- 
ling. 

Receiver with Shunted Detector.— Another 
arrangement, which permits a high degree of selectiv- 
ity while not requiring a detector of especially low 
resistance, is shown in Fig. 20. Here the oscillating 
circuit SC is closed upon itself and the detector D 
is shunted across the condenser. This arrangement 
may be adapted to detectors of widely varying charac- 
teristics; thus, if the detector is one which requires 
a high voltage to operate it, the condenser C is made 
of small capacity and the inductance is made corre- 
spondingly large. If, on the other hand, the detector has comparatively 
low resistance, the oscillating circuit is made of large capacity and low 




Fig. 19. Receiver 
circuits with De- 
tector in series. 



1066 



WIRELESS TELEGRAPHY. 



CI 



resistance, so that it may be robbed of considerable current without 
greatly increasing the damping. The particular detector shown in the 
rigure is the electrolytic (" polariphone ") cell described below. B is a local 
battery and F is a potentiometer for adjusting the voltage applied to the 
cell. C is a large condenser which permits the flow of the oscillators to 
the detector while preventing the short-circuiting of the battery through 
the coil S. 

DXTXCIOS9. 

Anti- and Auto-Coherer§. — Besides the typical filings coherer 
above described, many other forms of coherer have been devised. Some owe 
their distinctive characteristics to the material of which they are made. 
For instance, if carbon grains be used instead of metallic filings the operation 
of the coherer is reversed, i.e., the apparatus is normally a fairly good conduc- 
tor, but on the receipt of a signal 
its conductivity is destroyed. De- 
tectors of this type are called anti- 
coherers. The De Forest "Respon- 
der " acts in a similar manner. Two 
electrodes of tin or other suitable 
metal are immersed, close together, 
in a poorly conducting liquid, such 
as glycerine containing a trace of 
water, in which are suspended 
minute particles of metal. Under 
the influence of a local battery 
these particles form conducting 
bridges or " trees " reaching across 
between the two electrodes, and 
completing the circuit through the battery and a telephone. When oscilla- 
tions are passed through the apparatus the bridges are disrupted, the con- 
ductivity is destroyed, and a sound is produced in the telephone. 

Other modifications have for their object the abolition of the tapper, 
and give rise to the class of auto-coherers, whose action is entirely automatic. 
A globule of mercury in light contact with electrodes of iron or carbon con- 
stitutes an effective form of this device. 

Various miueral substances also have been found to be more or less 
effective as detectors of high-frequency oscillations. For example, if a 
crystal or fragment of carborundum magnetite or metallic silicon be 
clamped between a pair of metallic terminals its resistance is altered 
when the oscillations are caused to pass through it. When properly con- 
structed such detectors are quite sensitive. 

An improved form of mercury auto-coherer is shown in Fig. 21. A disk 
of steel a rotates in light contact with a globule of mercury b contained in a 




Fig. 



20. Receiver Circuits 
Shunted Detector. 



-=^B 



with 



iMTTni'ifi 






^W 


e 





.M 






Fm. 21. 



PLAN 
Mercury Auto-Coherer. 



^up d, which constitutes one terminal of the apparatus. The spring c, 
bearing on the shaft /' which carries the disk a, constitutes the other ter- 
minal. The disk a is normally separated from the mercury by a thin film 



DETECTORS. 



1067 



of oil, but under the influence of oscillations the insulation is broken down 
and the circuit is completed through a telephone or a siphon recorder. The 
steel disk is rotated by clockwork so as to present a continuously fresh 
surface to the mercury, and to break the contact as soon as the signal 
ceases. The edge of the disk is kept clean by a wiper k. 

JfEagTiietic [Detectors. — A very sensitive detector has been pro- 
duced by utilizing the changes in the magnetic state of iron which are 




Fig. 22. Magnetic Detector. 

caused by rapidly oscillating currents. If a core of iron wires be placed in 
a slowly varying magnetic field, the magnetization will lag _ behind the 
magnetizing force on account of the hysteresis, or "magnetic friction," 
of the metal. But if a rapidly oscillating current be passed through a 
coil surrounding the iron, the hysteresis is reduced and a sudden change in 
the magnetization occurs. This change in magnetization 
may be caused to induce an E.M.F. in a second coil sur- 
rounding the core, and thus operate a telephone receiver in 
series with this coil. 

Fig. 22 shows one form of the apparatus. W is a stranded 
belt of fine iron wires passing over the pulleys PP\ which 
are driven by clockwork. MM' are permanent magnets 
which supply the field to induce a continuously varying 
magnetization in the moving core W. A is a coil of copper 
wire through which the oscillations are passed, encircling 
the core W, and B is a second coil in which currents are 
induced to operate the telephone T. 

Electrolytic Detectors. — Another detector, which 
is extremely sensitive, depends for its operation on the 
changes in polarization of a specially constructed electrolytic 
cell which are caused by oscillations passing through it. 
The cell (patented by Andrew Plecher) consists of a minute 
anode of insoluble material such as platinum, and a larger 
cathode, immersed in a suitable electrolyte. When such a cell is 
connected across a source of E.M.F. greater than the decompo- 
sition E.M.F. of the cell, a current will flow and the cell will 
become polarized, opposing a counter E.M.F. to the passage of 
the current. If the E.M.F. across the cell be so adjusted that 
the cell is polarized to the proper critical point, it becomes re- 
markably sensitive to external impulses. The oscillations from 
an antenna passing through it have the effect of partially or 
completely depolarizing the minute anode, and a large momen- Fig. 23. 
tary increase in the local current occurs, with the effect of re- Electrolytic 
polarizing the cell to its sensitive point, ready for the next im- Detector — 
pulse. These changes in the local current are used to operate Cross Section, 
a telephone or other receiver. 

A convenient form of the cell is shown in Fig. 23, and the connections of 
its battery, etc., are shown in Fig. 20. T is a glass tube containing th« 




1068 WIRELESS TELEGRAPHY. 

electrolyte, C is the cathode of stout platinum wire, and A is the minute 
anode, both sealed by fusion into the glass. The anode is a fine platinum 
wire, .001 inch diameter or even less, sealed into the capillary tip of a small 
glass tube and then ground down flush with the surface of the glass, leaving 
only the end exposed. The area of anode surface is thus of the order of a 
millionth of a square inch. In the connection diagram (Fig. 20) D is the 
detector proper, F an adjustable inductive resistance or potentiometer, to 
regulate the voltage, and T a telephone. 

Hot-filament Detectors. — Another type of detector owes its 
existence to the peculiar properties of an incandescent body when placed 
in a rarified gas. Under such conditions the incandescent body emits nega- 
tively charged corpuscles or electrons, which are free to move about in the 
rarified gas, thus rendering it a more or less good conductor. If, for ex- 
ample, an incandescent lamp filament be mounted in its exhausted bulb in 
close proximity to a plate of metal connected to a third terminal, and a 
battery be connected between this terminal and one of the terminals of the 

filament, a current will flow from the 
battery through the gas. If now 
electrical oscillations be caused to pass 
through the tube between the filament 
and insulated plate, the conductivity 
of the tube is altered and variations 
of the current from the battery occur 
corresponding to the presence or ab- 
sence of the oscillations. Fig. 24 
shows a hot-filament detector J), con- 
nected across the condenser C of a 
closed oscillating circuit SCC, which 
in turn is coupled to the antenna A 
through a transformer PS. The fila- 

Frr 24 Hot-Filampnt ^Ptpotor ment of the detector is heated by a 
*ig. J4. not-iniament Detector. battery ^ and the local receiver circuit, 

including a second battery B' and a telephone receiver T, is connected 
between the insulated plate W and the positive terminal of the filament. 

Undamped Oscillations. 

It has been pointed out above that a prime requisite of a selective sig- 
naling system is a transmitter whoso oscillations are not strongly damped. 
An ideal transmitter for this purpose is one in which the oscillations are 
absolutely undamped ; that is, they are high-frequency alternating currents 
of constant intensity. Such a transmitter, besides making possible the 
highest degree of selectivity, possesses other advantages: for example, the 
continuous character of the oscillations enables a given amount of energy 
to be transmitted at a very much less intensity than is required with a 
strongly damped oscillator, which emits very intense radiations for a brief 
space of time, with long intervals of inactivity when no energy is radiated 
at all. Furthermore, the radiation from an undamped oscillator, being 
continuous, may be stored up cumulatively in the receiver, so that a 
signal of very feeble intensity maintained for a comparatively long time 
will have a relatively powerful effect on the receiver. 

All these and other considerations point to the undamped oscillator as 
an important factor in the future of wireless telegraphy. Already such 
oscillators have been produced and applied to practical work, but it is 
impracticable in this section to discuss them in detail. 




~T- sh 
—I n€ 



B 



TELEPHONY. 



Revised by J. Lloyd Wayne, 3d. 

The electric speaking telephone was invented by Alexander Graham Bell 
(then of Boston) in 1876. While exciting great interest in scientific as well 
as popular circles, it bade fair to be little more than a scientific toy until the 
intercommunicating or exchange idea was brought forward. It is in this 
connection that the telephone is of primary importance to-day, the number 
in use running well into the millions. 

Scope of* "!"For«l Telephone, — At first a single instrument of 
Bell's type at each end of the line served all purposes. Now commercial 
telephony has rendered it necessary to universally associate with these 
primary instruments several other pieces of apparatus, and the scope of the 
word telephone has been broadened to include all this allied apparatus of 
the telephone or subscriber's set. 

Requirements for Operation. — The fundamental problem 
of the telephone is really more one of acoustics than of electricity, and be- 
cause of this all attempts to solve the problem failed until it was approached 
from a purely acoustic standpoint. In order to understand the require- 
ments of operation it is necessary to understand the nature of sound and 
speech. 

Sound is propagated by means of vibrations of a purely physical nature, 
the vibrations of the various particles of the sounding body being so timed 



( 



Fig. 1. Phonogram of the Word " Hello. 1 



that there results a progressive wave motion. It is such a wave motion 
impinging upon the ear-drum and forcing it into a sympathetic vibration 
that is recognized as sound. Sound has three fundamental properties, — 
loudness, pitch, and timbre or quality. Loudness depends upon the energy 
of the vibrations, pitch depends upon the rate of vibration — thus, the 
vibrations per second — while quality depends upon the kind of vibration 
the individual particles are performing. 

If the character of the vibrations is such that the wave follows a simple 
sine law, a fine tone is produced. Every other kind of sound is produced 
by a wave more complicated than that of a pure tone. Each source of 
sound produces a wave form characteristic of that sound. Sounds vary in 
quality from the pure tone to the most discordant noises, but there is no 
generally recognized point of transition from one to the other. 

Speech consists of a proper combination of many sorts of sounds varying 
from pure tones to mere noises and hisses, intermingled in a proper order, 
and each given a proper relative pitch. 

The requirements for operation of the telephone are that any series of 
sounds spoken at one end of a line shall be transmitted to the other end 
and there given out correct in relative pitch and in quality. The term 
relative pitch is used, as a corresponding change in the pitch of all sounds 
has no distorting effect more than the difference between a low-pitched 

1069 



1070 



TELEPHONY. 



and high-pitched voice. Loudness is also of little moment, so long as sound 
leaves the receiver in sufficient volume to be heard. 

JfEeans of Transmission. — With the electric telephone, transmis- 
sion is accomplished by means of electric current waves sent out along a 
conducting line from the station at one end to that at the other end. For 
perfect transmission such electric waves are exact equivalents, except in 
energy, of the sound waves producing them, the strength of the electric 
current having at each instant direct relation to the sound vibrations. The 
periodicity of the current waves must at each instant correspond to the 
pitch of the sound, while the succeeding instantaneous magnitudes of the 
current must be such that the quality factor of the sound waves is virtually 
pictured electrically. From this it will be evident that the telephone cur- 
rent is a vibratory or alternating current of extremely complex character. 
This must be continually borne in mind as one of the most essential fac- 
tors to be contended with in telephone transmission. All the properties of 
alternating currents, of power magnitudes, and frequencies bear directly 
upon the subject of telephone transmission in greater or lesser degree. 

£L£HEXT» Of TELEPHONE SET. 

The telephone set, in addition to the various enclosing boxes, the mount- 
ing backboards and wiring, usually includes the following elements: 

1. Receiver or telephone proper. 

2. Transmitter and current supply. 

3. Induction coil. 

4. Hook or automatic switch, or a hand switch. 

5. Call receiving apparatus. 

6. Call sending apparatus. 

The design and function of these elements differ materially for different 
systems. In some cases it is even practicable to dispense with one or even 
two of them. 

Tlie Receiver. — The Bell receiver is universally used, it being 
thus far the only really practicable type. It consists of a permanent mag- 






Fig. 2. Single 
Pole Receiver. 



Fig. 2a. Magnet 
of Single Pole 
Receiver. 



Fig. 3. Double 
Pole Receiver. 



Fig. 4. Watch 
Receiver. 



net of bar steel, either straight or U-shaped, so mounted as to exert a polar- 
izing influence upon an electromagnet, before the poles of which latter 
an iron diaphragm is mounted. For convenience these elements are assem- 
bled within a casing of one of the well-known forms, such as shown in Figs. 
2, 3, and 4. 



ELEMENTS OF TELEPHONE SET. 1071 

In all commercial forms, the electromagnets are made quite short and are 
mounted directly upon the permanent magnet. The cores are of soft iron 
and are almost completely covered by the coil. In single-pole receivers (see 
Fig. 2), but one end of the bar magnet is used, one coil and extension 
pole sufficing. For such the permanent magnet is usually compound, and 
the coil and pole circular in section. In double-pole receivers (see Fig. 3) 
both poles of the permanent magnet carry soft iron extensions, both cores 
and coils being of oblong section. 

The soft iron diaphragm of circular shape about ^ of one inch in thick- 
ness and 2 to 2\ inches in diameter is secured by its edges in a manner to 
clear the soft iron extension cores from ^ to g^ of an inch. The magnet 
thus exerts a continual pull upon the diaphragm, tending to distort it, con- 
cave inwards. When the alternating telephone currents are admitted to the 
receiver coil, part of each wave assists the permanent magnet by its electro- 
magnetic influence, increasing the attraction and causing the diaphragm 
to further approach the magnet. That portion of the current of opposite 
sign detracts from the magnetic pull and allows the diaphragm to recede 
from the magnet. The diaphragm thus takes up a vibratory motion cor- 
responding to the electrical waves supplied to the coil, and it imparts 
motion to the surrounding air, which results in sound waves. 

Receiver casings are of various shapes, the shape being determined by 
the size of the parts and the dictates of convenience. The most usual 
form is the hand type shown in Figs. 2 and 3. The second common type 
is the ''watch-case receiver" shown in Fig. 4 and used where a small instru- 
ment is required. Lastly, there is the head telephone, in shape much 
like the watch-case receiver, but provided with a spring head band to hold 
it to the ear, leaving the hands free. The shape of the air space between 
the diaphragm and the aperture in the ear-piece of a telephone is of prime 
importance. This air space is now universally made shallow, from -£? inch 
to ^s inch in depth, and of an area nearly equalling that of the diaphragm. 
A relatively small hole connects the air space to the outside air. 

Many kinds of receiver are now manufactured and are upon the market. 
Detailed descriptions of these may be found in the trade catalogues, the 
later works on the telephone, and in a series of articles by A. V. Abbott 
in the Electrical World and Engineer, Vol. XLII. 

Magneto Transmitters. — The ordinary receiver will also oper- 
ate as a transmitter, and it was thus originally used by Bell. It is so mis- 
erably inefficient in this role, however, as to have been almost immediately 
superseded by the battery transmitter. There are, however, some house- 
telephone systems and private lines which employ two Bell instruments in 
series, as receiver and transmitter respectively. When so used the dia- 
phragm of the transmitting instrument should be much heavier and larger 
than for receivers if the best results are to be produced. At times the 
operation of the receiver as a transmitter is of material advantage, as one 
may so use it by talking sufficiently loud, when the regular transmitter is 
out of order and unusable. In this case it is, of course, necessary to shift 
the receiver from ear to mouth and vice versa, as the case demands. 

Battery Transmitter. — The battery transmitter depends for its 
operation upon what is known as the microphonic action of a loosely formed 
electrical contact. It is found that if a source of steady or constant electric 
potential, such as a battery, be applied to a loose contact, within limits the 
current which will flow will be in exact proportion to the pressure between 
the contact points. If, therefore, one contact point be held stationary and 
the second be clamped lightly between it and a diaphragm vibrating under 
the influence of a sound, the pressure between the contact points will vary 
with the motions of the diaphragm to produce current fluctuations exactly 
corresponding to the sound vibrations. It was at once found that under 
no circumstance must an actual rupture of the circuit be allowed to occur 
at the loose contact. It was also found that carbon of all conductors could 
be subjected to the greatest extremes of pressure within the range of true 
microphonic action, and because of this property it is largely used for trans- 
mitter electrodes. 

Single-Contact Transmitter. — Of the early successful transmit- 
ters, the Blake is by far the most important, obtaining at one time almost 
universal use, although it is now almost obsolete. In this transmitter 
the microphonic action took place at a single contact point between 
a globule of platinum, driven by the diaphragm, and a button of carbon. 



1072 



TELEPHONY. 




Both, electrodes were spring-mounted, tending to bear against each other 
normally, this tendency being augmented by the 
pressure of the diaphragm. While excellent for clear- 
ness, the Blake transmitter could be used for but 
comparatively short lines, because of the fact that its 
contact is only suitable for comparatively weak 
currents. A good idea of the arrangement of the 
parts of this transmitter may be obtained from 
Fig. 5. 

multi-Contact Transmitters. — The multi- 
ple contact transmitter of the Rev. Mr. Hunnings 
was the successor of the Blake transmitter. This 
transmitter having undergone numerous modifications 
and improvements culminated in the "Solid-Back' ' 
type, developed by Anthony White. 

In all transmitters of the Hunnings type the micro- 
phonic button consists of two electrodes, between or 
Fig. 5. Section of surrounding which is a mass of granulated carbon 
Blake Transmitter, approaching gunpowder in appearance. The electric 
D, diaphragm ; S, circuit is from one to the other electrode through the 
carbon spring ; S', granular mass. As long as the granular carbon is 
platinum spring; L, kept in a condition of looseness or "lightness," such 
iron bracket; jP, ad- a transmitter with its multitude of microphonic 
justing screw. contact points, some in series and some in parallel 

connection, is ideal. The resistance of such a trans- 
mitter is capable of a change, many times that of a single contact, 
it being practically impossible to actually break the electric circuit. Un- 
fortunately it has proved to be almost impossible to keep the mass of gran- 
ular carbon in a loose condition, there being a tendency to a "packing" 
which rapidly reduces the efficiency. The solid-back transmitter largely 
owes its success to its ability to withstand this packing tendency. 

Description of " Solid Back" Transmitter. — The casing of the 
transmitter is usually the only part in view, the operating parts being within 
it. The transmitter front is supported by the gong-shaped back, and carries 
all the parts. This front is very stiff, and the mouthpiece of hard rubber 
screws into it. The aluminum diaphragm lies in a receptacle cut for it in 
the rear of the front. This diaphragm has a rubber band snapped over its 
periphery, an anulus of rubber being thus formed upon each face of it. 
This provides an insulated cushion seat for the diaphragm. Damping 
springs with soft rubber cushions at their tips, serve to hold the diaphragm 
securely and at the same time prevent its assuming any but forced 
vibrations. 

In Fig. 7 is shown the various parts of the microphone button. The 
electrode chamber is formed out in a single piece, an insulating lining of 
varnished paper covering its cylindrical side walls. The back electrode is 
composed of a carbon disk soldered to brass mounting piece, the finished 
piece being secured in the bottom of the chamber by its screw stud. The 
front electrode is also a disk of carbon soldered to a brass mounting, and an 
auxiliary diaphragm of mica is provided to carry it and at the same time 
seal the chamber. The mica diaphragm m is perforated and slips over the 
shoulder p, being clamped by the nut u, which screws down upon the 
shoulder. 

The chamber is now charged with granules, the front electrode is placed in 
position and the edge of the auxiliary mica diaphragm clamped tightly by 
the clamp ring c, which screws down upon the chamber. The granules of 
carbon are insulated from the side walls of the chamber and the front elec- 
trode is insulated by the mica mounting, so that an electric circuit may be 
led through the button from electrode to electrode. 

The completed button is now secured between the main diaphragm and 
a heaving bridge piece which spans the receptacle in the rear of the front 
piece. The stud W (Fig. 6) has a seat in the bridge, while the front elec- 
trode is secured to the center of the diaphragm by the stud and nuts shown 
in Fig. 6. When everything is adjusted, a set nut clamps the stud W in 
place. A small flexible insulated wire extends from the front electrode to 
an insulated terminal upon the bridge piece, the metallic body serving as a 
terminal for the rear electrode. 

The vibrations of the diaphragm are communicated to the front electrode 



ELEMENTS OF TELEPHONE SET. 



1073 




by the pin, which forms a rigid connection between them. The electrode, 

having a certain freedom of movement within the little chamber, varies the 

pressure on the layer of carbon granules between it and the back electrode 

thereby setting up the usual variation of resistance required in a carbon trans- 
mitter. The design of the instrument is very 

good. The two electrodes, being of carbon, 

highly polished, make excellent contact with 

the carbon granules, thus affording the best 

opportunity for wide variation of resistance 

under vibration, while the carbon electrodes, 

being soldered to brass disks, have good 

metallic contact obtained with the two sides 

of the primary circuit. The ''packing" 

difficulty is nearly obviated in this form of 

transmitter. The space in the chamber 

but partially filled with carbon, and the 

space^ around the edges of the electrodes 

contains a certain quantity of it, which is not 

directly in the circuit, and does not become 

heated by the current. Any expansion of 

the granules immediately between the elect- 
rodes through heating causes a displacement 

of part of the heated carbon into the cooler. 

When the transmitter is out of circuit and 

cools off, the granules tend to resettle into their original position. 

The chamber < containing the working- 
parts of the instrument is extremely 
small. By unfastening the screws which 
hold the cover, the entire transmitter can be 
withdrawn, the connecting cord joined to the 
insulated binding-post having first been dis- 
connected. On account of the smallness 
and delicacy of the parts, great care is 
required in handling the transmitter when 
assembling or taking apart. When properly 
set up, it needs no adjustment ; and indeed 
there is nothing that can be adjusted unless 
some radical defect exists. Figs. 6 and 7 
show the details of construction by means 
of a section of the transmitter mounted, 
and a section of the various parts of the 
chamber, and a front view of the chamber. 
The following dimensions give an idea of 
the sizes of the parts of the carbon button 
of the solid-back transmitter. 



Fig. 6. Section of Solid-Back 
Transmitter. M, mouthpiece; 
D, diaphragm; E, front elec- 
trode; B, back electrode; W f 
electrode chamber; P, metal 
bridge piece; d, set screw; m, 
mica washer; p, threaded pin 
on front electrode; e, rubber 
band; /, damper; C, case; F, 
cover. 




Fig. 7. Details of Solid-Back 
Transmitter. W, electrode 
chamber; i, insulating lining; 
B, back electrode; o, brass 
backing; E, front electrode ; 
b, brass backing; p, thread 
for nut U; m, mica washer; u, 
nut for clamping m in place ; 
p' thread for t and t'\ c, cover 
of "FT; TT, nuts for clamping 
front electrode to diaphragm. 



Separation of electrodes 05 inch. 

Eiameter of front electrode 66 inch, 
iameter of back electrode 69 inch. 

Diameter of chamber . . . 75 inch. 

Thickness of paper lining 005 inch. 

Thickness of mica diaphragm 010 inch. 



Weight of carbon granules used — Approx. 400 mgms. 

Diaphragm of aluminum, 2\" dia., .02" thick, varnished on one side. 



The solid-back transmitter is most efficient when the diaphragm is in a 
vertical plane, but the efficiency is not much changed so long as the dis- 
placement from the vertical is not great. As the diaphragm approaches 
the horizontal position the transmitter not only loses its efficiency, but 
there will be much confusion and distortion of the sound, and at times 
the transmitter may be wholly disabled, the cause of this being that the 
chamber is but partially filled with granules, and the carbon may fall almost 
or entirely away from the upper electrode. 



1074 TFLEPHONY. 

Commercial " Solid-Back " Transmitter.— The solid-back 

transmitter manufactured by some companies for the open market is prac- 
tically a duplicate of the above, except as to unessential details. One 
notable exception is the inverted J ype :>f solid back devised by Mr. W. W. 
Dean. In this transmitter, the carbon retaining chamber is formed in 
the diaphragm, and, therefore, there is introduced by the vibration of the 
latter an additional x endency to shake up the carbon granules. In detail 
design and size of parts this transmitter adheres closely to the Bell "Solid- 
back" model. 

" Corn IMaster " Type. — Another type of granular transmitter con- 
siderably used but not so good as the preceding, is that employing a felt 
washer as the containing chamber for the granular carbon. . Such a trans- 
mitter depends upon the elasticity of the felt to permit of the relative motions 
of the electrodes which close the chamber at the front and rear 
resDectivelv. 

*• Packing* and "Unpacking*." — A packed transmitter maybe recog- 
nized by the dullness of the transmitted tone, the life being so far taken 
out of the tone at times as to render the words indistinguishable. To 
unpack a transmitter a slight jarring will at times suffice, this being best 
accomplished by striking the casing sharp, light blows with a hard object. 



gratings in the front and air ducts at the base. 

How to Use a OrannlarButton Transmitter. — The electrodes 
of the transmitter should always be in a nearly vertical plane. The lips should 
be placed close to the transmitter and the voice directed into the mouth- 
piece. As the weight of the parts to be moved is considerable, a large pro- 
portion of the energy of the voice must be expended upon the diaphragm. 
When used properly, a tone of voice, such as used in ordinary conversation, 
should be amply sufficient, and of this scarcely any need escape to the sur- 
rounding air. 

Induction Coil. — When the battery transmitter was first introduced 
it was planned to connect it directly in the line in series with the battery 
and receiver. In this connection the total allowable resistance change in 
the transmitter is very small in comparison with the total line resistance, 
and therefore the corresponding current changes in the receivers are small 
and of little effect. Furthermore, the longer the line, the less proportional 
part of the total resistance is the changeable part of the transmitter resist- 
ance, and thus the longer the line, the less the possible transmitting 
effect. 

To obviate this difficulty Edison introduced the induction coil connecting 
the transmitter and battery in circuit with the low-resistance primary and 
connecting the secondary in series with the telephone and line. With this 
arrangement not only is the variable transmitter resistance made a large 
proportion of that of its circuit and this proportion made invariable with 
the length of the line, but also, by making the number of turns in the 
secondary winding large in comparison with those of the primary, the 
generated secondary voltage is made quite high, and thus suitable for long 
lines. There is yet another effect* viz. : the variable current of the trans- 
mitter circuit becomes transformed into a true alternating current. 

Construction of Induction Coil. — The induction coil is almost 
invariably of the open magnetic circuit type. The core is composed of a 
bundle of annealed iron wire, upon which is wound the primary, usually of 
comparatively heavy, insulated copper wire, while the secondary of fine 
wire surrounds this. 

Desig*n of tne Induction Coil. — Thus far no general method 
of computing induction coils has been developed, the best design for any 
work being found by a "cut and try" method. Usually each manufacturer 
has determined by a series of experiments, more or less elaborate, that a 
certain induction coil will give good results when coupled with his trans- 
mitter and receiver. He will then use this coil until something better is 
happened upon. Very few comparative tests of induction coils are upon 
record, and such as are, give no clew to any relation whatever between good 
transmission and the physical dimensions and electrical constants of the 
coil. 



CALLING APPARATUS. 1075 



HOOK SWITCH. 

After attempting in vain to use as a means of calling greatly magnified 
currents of the telephone type, produced by over-exciting the transmitter, 
there remained but two alternatives. Of these, one was to parallel the 
telephone line with a calling line, each line to carry currents of its own type; 
while the second was to use the telephone line in a double function, switching 
upon the ends either calling or talking apparatus as desired. 

This latter method was used, hand switches being adopted until the 
forgetfulness of users proved that such were most unreliable, a talking and 
a calling apparatus being frequently inadvertently left connected together 
in a manner to defeat the whole system. The hook or automatic switch 
proved a fairly satisfactory means of overcoming this difficulty, being to-day 
in almost universal use. In the first place the switch lever is pronged to 
form a support for the receiver, and it should furthermore be about the 
only visible means of support for the receiver. When the weight of the 
receiver is upon the prongs, the lever is depressed so that the calling appa- 
ratus alone is connected to the circuits. On the other hand, when the hook 
rises in response to a spring, the receiver being removed, the switch operates 
to connect in the talking circuits. 

Design of Hook Swi telle*. — Hook switches are of many designs, 
each manufacturer producing his preferred idea. Many are of equal effi- 
ciency. The main points to be considered, are: first, to have the switch 
springs perform exactly the functions desired; second, to be sure that they 
perform no accidental and detrimental functions; third, to have the motion 
of the springs limited by positive stops; fourth, to be sure that the weight 
of the receiver is ample to actuate the switch; fifth, to have a sliding motion 
at the points of contact which should preferably be platinum tipped; and, 
sixth, to have the hook prongs so shaped as not to injure the receiver. In 
explanation of these points, it may be said that in usual systems, the switch 
lever on rising must connect two contact points to a third in common, as 
will be seen from later circuit sketches. In the depressed position some- 
times it is merely necessary to break this connection, and sometimes in 
addition necessary to make a third connection. As to positive stops it 
may be said that when switch springs are allowed to come to a position of 
rest due to their own set, they are quite sure in time to have the position 
of normal set sufficiently disturbed to disarrange the apparatus. A sliding 
motion of the contacts over each other is desirable, as the contacts thus 
become largely self-cleaning. As to the hook prongs, it has probably been 
noted that nearly all are now provided with ring ends which cannot be 
forced against the receiver diaphragm. 



CAIIOG APPARATUS, 

Calling apparatus has been worked out upon several complete systems. 
The most obvious one, employing direct current from a battery with push 
buttons and vibrating bells, while still holding its own for the very short 
lines of some house systems and for toy lines, has proved unsuited for com- 
mercial telephony. This system will therefore be ignored here, but it will 
be mentioned in the sections on House or Interior systems. 

For general commercial working the polarized bell, sensitive to alternating 
currents, has proved to be the best. To produce the alternating currents 
for actuating it, a magneto generator, i. e„ a dynamo having permanent 
magnets for fields, was long ago adopted, and this fact has given the name 
to this system, viz., the " Magneto " system. Recently a calling system, a 
combination of battery and magneto calling has been extensively adopted. 
With this system, calls for the stations are made by means of the polarized 
bell with alternating current, while calls towards the central or interconnect- 
ing station are made by direct battery current operating an annunciator. 
The sending of the calling signal is effected by merely removing the receiver 
from the hook. This is the calling system employed with the now prevalent 
common battery" system. 



1076 



TELEPHONY. 



SERIES AUTD BRIDGING SYSTEMS DEFINED. 

There are two methods of connecting calling apparatus into telephone 
circuits. The first of these is termed "series," and is that shown in Fig. 8, 
where it will be seen that the generator and bell are wired in series, and if 
there be an extension bell as in Fig. 9, this is connected in series also. In 
the " bridging" system, on the other hand, the generator and bell are 



pEIP- 



-^fflp 



HH5H..r- 



, ^h M j- 




Fig. 9. Diagram showing Proper 
Connections of Extension Bell. 



Fig. 8. Diagram of Connections 
of Series Magneto Bell and 
Telephone Set. 

connected across'the line in parallel, or, in other words, they are "bridged" 
across the line. In case there is but one wire used for the line, the earth 
serving for a return circuit, the bridges are made from the line to earth. 
Diagrams of bridging sets are shown in Figs. 10, 27, 28, and 68. 



/-K /-K 







Fig. 10. 

As the requirements for operation of the calling apparatus are very 
different in the series and bridging systems, it will be necessary, from now 
on, to point out the differences in the apparatus designed for them. 



THE POIARIZED BE11. 

The working parts of a polarized bell always include an electromagnet, 
a permanent magnet, a pivoted armature carrying a bell clapper, and two 
gongs. These may be disposed with reference to each other in a variety 
of ways, but always with the same result. It will, therefore, be necessary 
to consider the most general type only, a diagrammatical view of which type 
of bell is shown in Fig. 11, and a side view in Fig. 12. 

The armature is pivoted to vibrate in front of the poles of the electro- 
magnet, the pivot lying in a plane parallel to the pole faces, being midway 
between the two poles and so placed with reference to them that the arma- 
ture cannot touch both poles at the same time. The permanent or polar- 
izing magnet, usually a very broad U, has one of its poles secured to the 
middle of the yoke of the electromagnet, while the other extends to a point 
just beyond and over the middle of, but out of contact with, the armature. 
The coils of the electromagnets are connected directly together and to the 
wiring, without movable contacts of any kind. 

When there is no current flowing in the coils, the electromagnet cores 
act merely as extensions of the permanent magnet, both poles of it becoming 
magnetized alike and of opposite polarity to that of the free end of the per- 



THE POLARIZED BELL. 



1077 



manent magnet. The armature also becomes magnetized, but by induction, 
with two free and one consequent pole, the free poles being such that there 
is an attraction for each by the opposed core of the electromagnet. t These 
attractions are not equal, except when the armature is exactly in its mid, 
an unstable, position. In any other position the attraction is greater for 
the nearer end of the armature than for the other. Thus the armature 
naturally comes to rest against one or the other pole, as the case may be. 
When alternating current is put on the line, the first impulse may do one of 
two things: it may be of direction such as to strengthen electro magnetically 
the pull of the pole upon which the armature is resting, by adding the effect 
of the current to that of the permanent magnet, while at the same time 
decreasing the effect of the other pole by a similar but sub tractive effect; 
or the current being in the opposite direction may weaken the pull of the 
poles in proximity and strengthen that of those separated. It is this 
latter kind of impulse which starts the bell, for the armature will rapidly 
tilt in response to the changed attractions, only to be tilted back immedi- 
ately by the succeeding current impulse of opposite sign. This action is 



.±v^ 





Fio. 11. Magneto-Generator and 
Bell 



Fig. 12. Polarized Bell with Long 
Core for Ringer of Bridging Bell. 



repeated for each reversal of the current, the armature and bell clapper 
making a double vibration for each cycle of the current. 

For bridging working it will be seen that the bells are shunted directly 
across the talking instruments, and they must therefore be designed with 
reference to this effect. It has been found that with a resistaxice of winding 
of 1000 ohms, using No. 33 copper wire and cores about three inches long, 
the shunting effect is negligible even when a considerable number of bells 
are placed across the line. It is essential, of course, that the resistance be all 
or almost all wound upon the cores Of the bell, as the telephone current 
being alternating the virtual resistance due to the inductive winding is far 
greater in effect than the ohmic resistance, and again, as the efficiency 
of the bells demands the greatest possible number of turns where effective 
in operating the armature. 

For series systems the very opposite condition obtains, for not only is 
the bell always removed from influence upon the talking circuit, but econ- 
omy demands that the resistance be kept low, especially where several 
pieces of apparatus are in series. Eighty ohms is the usual resistance for 
series bells, and the cores are made much shorter than for bridging bells. 

Recently a type of bell known as "biased" bells has come into use for 
certain party line systems. Such bells have in addition to the features 
above mentioned, an adjustable spring which serves to give the armature a 
bias in one direction so that it will always come to rest against the 
same pole piece. 



1078 



TELEPHONY. 



COarSTRUCTIOlV OF ^agmio generator. 

As previously noted, the magneto generator is provided with a field by 
permanent magnets. From two to six U magnets are used, three being 
the most frequent number. These magnets are usually cold bent from bar 
steel approximately \" X 1" in section, and after quenching in cold running 
water from a red heat, are magnetized by stroking. These magnets span a 
pole frame within which the armature turns. The armature is of the H. 
Siemens type, usually of cast iron, and wound full with fine wire. The 
number of turns of wire and the size of wire vary considerably with the 
use for which the apparatus is designed. The armature is driven by hand 
through a gear train arranged so that one will ordinarily drive the arma- 
ture about 1000 revolutions per minute. At this speed the proper potential 
for operating the bells should be delivered. This latter ranges from forty 
volts up, series system machines usually generating a higher voltage and 
less current than those for bridging systems. One terminal of the arma- 
ture is usually brought out through an insulated shaft pin to a brush, while 
the frame serves as the other terminal. 




Fie. 13. 



There are many points of design upon which considerable thought has 
been expended. Such is the interposition of a flexible spring coupling 
between the driving gear and the armature shaft to render the generator 
noiseless. Another is the proper proportioning of the span of the armature 
poles and the gap between the pole tips of the field to obtain the most 
effective wave form. It is generally conceded that these dimensions should 
be equal for best results. The automatic switch is still another feature. 
This is a switch so arranged that the generator is cut from circuit except 
when actually in use. For a series system cutting from circuit of course 
involves short-circuiting the generator, while for bridging systems the 
generator bridge must be opened. In some of the older telephone sets a 
push button serves in lieu of the automatic switch, and in still others the 
driving handle must be depressed to connect in the generator. In modern 
sets, some centrifugal or spring device integral with the driving mechanism 
automatically controls it. A prevalent type of automatic switch is shown 
in Fig. 13. Here the driving pin rides the sloping gear hub to move the 
shaft longitudinally to the lef|>. 

For the Common Battery system, as before mentioned, no generator 
is required. The bell, however, is exactly that already described. This 
system will be referred to more fully later, when its operation and circuits 
are described. 



FACTORS AFFECTING TELEPHONE TRANSMISSION. 1079 



FACTORS AFFECTING TELEPHONE TRA1¥§MI§. 
SIOUT: ODIJCTA^CE, CAPACITY, »~ESi:STA]¥CE. 

As mentioned earlier, the telephone current is an alternating current, 
and is therefore subject to all the influences of inductance and capacity. 
These are, moreover, exceedingly potent in their effects, because of the 
very high frequency of the telephone current, and because this current is 
made up of superimposed waves of many frequencies. 

Inductance always tends to choke off alternating currents passing through 
it. While all lines have inductance, that with which we are most concerned 
is due to coils of wire about a core of iron. Such coils are variously called 
in telephony, choke coils, retardation coils, inductance coils, and, although 
not entirely properly, impedance coils. The inductance of a coil such as 
in a receiver or a bell magnet has a reducing effect equal to a long length 
of line; and a few small coils in series in a line, or one large one, will have 
the practical effect of so lengthening it, as to put the transmitting station 
beyond the reach of the receiving station. It is this choking effect of 





Fig. 14. Complete Magneto-Bell 
Post Pattern. 



Fig. 15. The Bridging Bell. 



inductance which renders the bridging bell practicable. Inductance has 
another effect, viz., it distorts and confuses transmission; the reason 
being that inductance chokes the higher frequency waves, i.e., the high 
tones, far more than the lower. Even when present in small degree, it 
gives the transmitted tone a "drummy" sound. 

The effect of capacity or condensers is also twofold. Capacity placed or 
bridged across a line conducts the telephone current, but affords a freer 
path for the higher frequencies. It thus reduces the volume of the whole 
transmission and distorts by shunting out the high pitches. In series 
with a line the distorting effect of capacity is just the opposite of this. It 
obstructs the low frequency and permits the passage of a disproportionate 
quantity of high frequency current. 

Capacity exists in its shunting relation, in all lines, because every pair 
of conductors forms a condenser. When capacity exists in series with a 
line it is in the form of a condenser of thin plates. It is used in this rela- 
tion to the line whenever it is desirable to permit the flow of alternating 
current and to stop the flow of direct current. Similarly it must be under- 
stood that inductance coils can be used to permit the flow of direct cur- 
rents and arrest the flow of alternating currents. Capacity and inductance 
are also used in conjunction, each to partially neutralize the effect of the 
other. An example of such a use is the shunting by a condenser of a relay 



1080 



TELEPHONY. 



the coil of which is necessarily included in series in a talking circuit for sig- 
naling purposes. 

Resistance acts just as would be expected, to attenuate the telephone 
current. As all component periodicities are reduced equally, however, 
there is no distortion. Leaving out of consideration the conduction of 
direct currents, the only case in which resistance is of much importance 
is when it is combined with distributed capacity. For a long time Lord 
Kelvin attempted to apply his KR (capacity resistance) law to telephone 
lines, but this law has been found to not fit the case. The best light upon 
the subject seems to show that the combined effect of distributed capacity 
and resistance is nearer proportional to the square root of their product, thus, 
a ^KR, rather than the product itself. 

Besides these three most important factors, there are several other, 
though less important, effects. Among these there are losses due to Fou- 
cault or eddy currents, hysteresis losses, and reflection losses. These last 



Sjiturns for # 8 B.W.G. 
3 turns for 12 N^EL&jGU. 




Fig. 16. Regular and Pole Transpositions. 



occur when there is any abrupt and considerable change in the transmit- 
ting medium. Thus, for instance, where a line of almost no inductance 
is connected directly to a line of very high inductance, such as is used in 
the Pupin system of transmission. These reflections are analogous to the 
reflections of light and sound. In most telephone work little consideration 
ia given to these last mentioned losses. 



EARTH CURRENTS. 



1081 



EARTH CIRREXT§, INDUCTION, CROSS-TALK. 

When the telephone was first adopted, all lines were worked as "grounded n 
circuits. That is, but one wire was used in connection with an earth re- 
turn. As long as the lines were fairly short, and there was an inconsider- 
able use of the earth for a return for other systems, trouble was experienced 
due to disturbing earth currents only in times of general magnetic storms. 
Slight disturbances occurred, however, at all times. 

It has been found that the earth is subject to continual potential fluctua- 
tions, usually minute, but changing with great rapidity. These cause 
disturbing currents to flow over grounded telephone lines. When neigh- 
boring trolley lines also use the earth as a return, grounded circuits be- 
come unbearable not only from the earth potential disturbances, but also 
from induction. This latter effect is due to a mutual inductive action 
between the telephone and neighboring wires. Induction may be due to 
electromagnetic or electrostatic effect. The former occurs when the 
varying field of force about a wire carrying a disturbing current, cuts and 
sets up a corresponding field about a parallel telephone wire. Electro- 
static induction is caused by a series of rapid redistributions of the natural 




B C JBABC B A B C B A B C BAB 



Lower Cross Arm 

I 

Fig. 17. Transpositions on Twenty-Wire Lines. 



charges in the telephone line in the attempt to maintain a constant electro- 
static balance in the neighborhood of the disturbing wire. That it is this 
latter effect to which most line induction may be traced was proved by 
J. J. Carty in a series of most interesting experiments, reported in 1889 to 
the New York Electric Club, and in 1891 to the American Institute of 
Electrical Engineers. 

Cross-talk is the name given to induction or leakage from one telephone 
line to another. It is distinguished by the faint sound of voices. 

metallic Circuits. — With metallic circuits it is possible, though 
not always practicable, to do away entirely with disturbances. It is, 
however, almost always practicable to reduce disturbances to a point where 
they will not interfere materially with conversation. By metallic circuit 
is meant not merely a two-wire circuit without qualification, but it means 
an all-metallic line, both of whose limbs have the same and similarly dis- 
tributed resistance, the same capacity, and the same insulation resistance. 
Moreover, both limbs should be equally exposed to all disturbing influ- 




1082 TELEPHONY. 



ences. With insulated wires this last condition is easily obtained by twist- 
ing the two wires about each other to form what is called a " twisted pair.'" 
With bare wires "transposition" must be resorted to. 

Open IFire Circuits. — Open wire circuits are carried upon poles, 
or in cities, sometimes upon house-top fixtures, although this latter type 
of construction is rapidly disappearing. The principles underlying the 
construction of telephone pole lines are exactly similar to those for other 
lines. The factor allowed for wind-pressure and for weight of ice from 
sleet storms must, however, be proportionally greater than for most other 
kinds of lines, because of the large exposed surface of conductor. 

Cross-arms for telephone lines are usually 10 or 6 pin, the wires adjacent 
to the pole being 16 inches apart and others 12 inches apart. Cross-arms 
are mounted two feet apart. Poles are usually set to give an average span 
of 130 feet, i.e., 40 poles to the mile. 

The requirements for metallic circuits dictate that both wires of a pair 

shall be of the same diameter and material, and that they shall be placed 

in adjacent positions on the same cross-arm. Furthermore, at intervals the 

two wires must change places, in a manner such that both shall have the 

same average distance from all disturbing influences. This interchange 

of wires is termed "transposition." In case of extreme exposure, such as 

where telephone signal-wires are run upon the same poles as high-tension 

transmission lines, continuous transposition may be resorted to. Under 

ordinary conditions of telephone practice, it 

is found satisfactory, however, to transpose the 

wires upon a system which treats each two 

cross-arms as a pair, i.e., 20 circuits as a group, 

and which provides for the transposition of each 

with reference to its mate and to disturbing 

untransposed wires, at least once each mile. 

This brings "transposition poles" one quarter 

mile, or approximately 10 poles apart. A dia- 

FiG. 18. English Method gram of this transposition scheme is shown in 

of Transposing Metallic Fig. 16. 

Circuit. Fig. 17 shows a diagram of this transmission 

system, a study of which will show that only 
those wires furthest apart in the group, transpose upon the same pole. For 
very long lines a further refinement must be introduced treating four cross- 
arms as a transposition group, for it has been found that cross-talk will occur 
between alternate arms of the two-arm system. Fig. 18 shows a method 
of continuous transposition. 

Recently > much of the transposition has been of a type known as single 
pin. This is much cheaper than that shown in Fig. 16. By this method a 
cross over of two wires is distributed over two spans of the line, the actual 
cross taking place at one pin of the middle pole. This pin is provided with 
a double groove transposition insulator, while its mate carries none. In 
the first span, one wire passes from its own pin position to the base of the 
glass in its mate's position. It then continues in this position while the 
mate wire passes over to the position in the second span vacated by the 
first wire. If both wires be tied to the same side of the insulator at the 
middle pole there is no danger of a short circuit. 

The properties of conductors need not be discussed here. Suffice it to 
say that for open-wire circuits, iron, steel, aluminum, bronze, and copper 
have been used. Hard drawn copper is undoubtedly standard. Iron and 
steel are less satisfactory not only because of high resistance, but be- 
cause of the difficulty of making good permanent joints, of deterioration, 
and of their highly magnetic properties with attending inductance. 



CABLES. 

Conductors laid up into cables were first brought into use to relieve 
congested or overcrowded pole lines. At first they were of small copper 
wire insulated with rubber or similar compounds. With the introduction 
of metallic circuits came the introduction of twisted pair cables. Such 
cables are of course relatively free from cross-talk so annoying with 



SAMPLE SPECIFICATIONS. 1083 

straight away cables. Because of the very high specific inductive capacity 
of rubber, and the proximity of the wires of a pair, so high a mutual 
electrostatic capacity was introduced as to greatly reduce transmission. 
For aerial lines, rubber cables are yet used in some localities, especially for 
emergency and temporary work. General practice has, however, substi- 
tuted the cheaper and far better paper insulated cable for all uses. 

Properties of Paper Insulated Cables. — - Present day telephone 
cables are what are known as dry core cables, as the insulation is untreated 
paper, thoroughly dried. Strips of paper are loosely spiraled about the cable 
wire, and this is then twisted together in pairs with a lay approximating 
3 inches. The pairs are then layed up in reversed layers to form a cylin- 
drical core which is served with paper or cotton yarn or both. The core is 
then thoroughly dried by baking, and it is run' directly from the kiln to the 
lead press which surrounds it with a moisture proof sheathing of either 
pure lead, or an alloy of lead with 3 per cent of tin, this alloy being tougher 
than pure lead. 

The paper used is very porous, and being loosely wrapped the insulation 
about each wire is largely dry air, and it is this fact to which the low 
electrostatic capacity and the high insulation of such cable is due. The 
slightest moisture will greatly impair and may ruin paper cables and the 
core is so dry that sufficient moisture may be absorbed from the air to 
injure them. To prevent this, the ends of each length of cable are usually 
"filled" with paraffin for a few feet, and whenever a cable is cut at an 
unfilled spot, it is immediately "boiled out" by pouring over it hot paraffin- 
wax. 

Probably the greatest number of cables now in use are of No. 19 B. and S. 
gauge wire, while of those being manufactured the greatest number are 
of No. 22 gauge wire. For long-distance lines cables have been used of 
Nos. 18, 16, 13, and 10 gauge. 

Cables are known, according to their use, as aerial, distributing, under- 
ground, and submarine. Aerial cables are made as light weight as is con- 
sistent with durability. The usual sizes are from 15 to 100 pairs. 

Distributing cables have a thicker sheath than aerial, but are made in 
about the same sizes. Underground cables are used in conduit beneath 
the streets. The usual sizes are from 100 to 300 pairs if the size of wire 
be No. 19, and 150 to 400 pairs if the wire be No. 22. Underground cables 
have been made up to 600 pairs, but such cables are not practicable at 
present for general use, as the allowable diameter of cable is limited, on the 
one hand, by the size of the conduit duct, usually 3 in. in diameter, and it 
is limited on the other by the electrostatic capacity. The smaller the cable 
of a given number of pairs the higher the capacity per pair. 

Until recently submarine cables were all rubber covered and of not over 
10 pairs. Now paper submarine cables of far better insulation, less electro- 
static capacity, and a greater number of pairs of wires have been success- 
fully developed. These cables are of from 30 to 150 pairs size. The lead 
sheath is usually thicker than for underground cables, and after being 
served with jute is covered with an armor of steel wires. 

The following sample cable contract written by A. V. Abbott sets forth 
in tabular form the details of several types of cable. 



SA.UPIS SPECIFICATION EOH lELEPHONE 
CABLES, 

(A. V. Abbott.) 

Gentlemen: — Under the conditions hereinafter specified, please deliver 
the following enumerated telephone cables free on board cars at freight 

depot in reel, marked , containing feet of 

No. B. and S. gauge, pair, aerial (or underground) paper 

cable, capacity to m.f. per mile, inch plain lead (or 

with per cent tin) at quoted price of cents per foot 

reel, marked , containing, etc. 

Conductors. — Each conductor shall fully and throughout its entire 
length have the diameter corresponding to the gauge stated above, and 



not more than . 


. . 25 . . . 


not more than . 


. . 31 . . . 


not more than . 


. . 38 . . . 


not more than . 


. . 47 . . . 


not more than . 


..59... 


not more than . 


. . 95 . . . 



1084 TELEPHONY. 

shall be cylindrical and free from imperfections. The material of the con- 
ductors shall be soft-drawn copper. 

Insulation. — Each conductor shall be insulated with one (or two 
reversed) wrapping of dry paper; the insulation of one conductor in each 
pair shall be colored blue and that of the other conductor red. 

lumber of Pairs. — Each cable shall have the number of pairs 
called for above, plus at least one extra or additional pair for each one 
hundred (100) or fractional part of one hundred (100) pairs of conductors 
called for. 

Twisting:. — The two wires of each pair shall be twisted together with 
a uniform lay, not to exceed approximately three inches for No. 19 B. and 
S. gauge and smaller wires, and approximately six inches for larger wires 
in a complete twist, so as to effectively prevent cross-talk. 

Cabling-. — The twisted pairs shall be laid up into a cylindrical core, 
arranged in reversed layers, so that the length of each complete turn shall 
not exceed thirty inches. 

Sheath. — The core shall be incased in a cylindrical sheath of plain 

lead (or an alloy of lead and per cent tin) of the thickness specified 

above. The sheath shall be free from holes or other imperfections and 
shall be of uniform thickness and composition. 

Conductor Resistance. — Each conductor shall have a resistance 
equivalent to 

ohms per mile of No. 16 B. and S. gauge cable; 

ohms per mile of No. 17 B. and S. gauge cable; 

ohms per mile of No. 18 B. and S. gauge cable; 

ohms per mile of No. 19 B. and S. gauge cable; 

ohms per mile of No. 20 B. and S. gauge cable; 

ohms per mile of No. 22 B. and S. gauge cable. 

All measurements to be made at 60 deg. F. 

The conductivity of any wire shall be equal to at least 98 per cent of 
that of pure copper. 

Insulation Resistance. — Each wire shall have an insulation re- 
sistance of not less than three thousand (3000) megohms per mile at 60 
deg. F., when tested at the factory in the usual manner, and shall have an 
insulation resistance of not less than five hundred (500) megohms per mile 
at 60 deg. F., when installed, spliced, and connected to office terminals; 
each wire being measured against all the rest and the sheath grounded. 

electrostatic Capacity. — The electrostatic capacity of the wires 
shall remain inside the limits specified above (see p. 889) . These limits to apply 
to measurements of each wire against all the rest and the sheath grounded 
and at a temperature of 60 deg. F. 

Packing* and Shipping-. — The cable shall be delivered on reels in 
lengths specified above. At least eighteen inches of the inside end of the 
cable shall be brought out through the side of the reel so as to be accessible 
for testing. This end shall be securely boxed to protect it from mechanical 
injury. The outside layer of cable on each reel shall be properly wrapped, 
and each reel shall be incased in stout lagging. Each reel to carry in plain 
sight the company's name, the above specified identification mark, length 
and size of the cable. 

Relive rv. — Reel marked , shall be delivered at 

on or shortly before 190 — . Pteel marked at 

on or shortty before , etc. 

measurements and Tests. — The company reserves the right to 
send an inspector to the factory to be present during the process of manu- 
facturing and to test the qualities of the materials used and the electrical 
properties of the cable before shipping. He shall have the power to reject 
any material or cable found defective. Such inspection, however, shall 
not relieve the manufacturer from furnishing perfect material and satis- 
factory work. Final measurements and tests are to be made after the 
cable is installed, spliced, and connected to office terminals. In case the 
cable falls so far short of the above specified requirements that the company 
is not willing to accept it, the manufacturer will be called upon to examine 
the work done by the company, and, if able, by remaking splices or repair- 
ing injuries to the cable received in handling and laying, to bring the cable 



SPECIFICATION TABLES. 



1085 



up to the requirements; the cost of the work shall be borne by the com- 
pany. If such work, however, does not bring the cable up to the require- 
ments, and the cable is shown to be defective in material or work done by 
the manufacturer, then the manufacturer shall make the cable good by 
replacing as many lengths as may be necessary, and shall not be entitled 
to pay for work done in examining and remaking splices. The company 
will, if the manufacturer fails to do so, perform all the work of testing and 
remaking splices, and charge the cost of such work to the manufacturer in 
case the defect is found to be due to poor material or workmanship on the 
part of the manufacturer. The manufacturer shall be notified as soon as 
the company's inspector reports any defects, and he may have a represen- 
tative present during such tests and work done by the company to detect 
or repair defects. The company reserves the right to have a representa- 
tive present whenever the cable is tested or work is done by the manu- 
facturer in repairing defects. 

Guarantee. — The electrostatic capacity shall not increase, nor shall 
the insulation resistance decrease, beyond the specified limits due to defec- 
tive material, manufacture of workmanship, for a period of years 

after the cable has been installed. 

Payments. — Payments for the cable shall be made within thirty (30) 
days from the receipt of a consignment, except that fifteen (15) per cent 
of the price of each consignment shall be held thirty (30) days after each 
separate consignment is installed and accepted by the inspector of this 
company, who shall make a written report accepting or rejecting the cable 
within twenty days after installation; in case of rejection a written notice 
and statement of the defects shall be sent immediately to the manufacturer, 
and if the manufacturer fails inside of ten days to remedy such defects 
they will be remedied by the company and the cost deducted from the 
final payments, or if the percentage is not sufficient to pay for such repairs 
the manufacturer must refund the difference. 



(Signed) 



Telephone Company. 



SPECiriCATIO]¥S FOR TELEPHONE CABLES. 
Table ¥. — Capacity of Aerial Telephone Cables. 

Revised by John A. Roebling's Sons Co. 















Approxi- 






Thick- 




Approxi- 


Approxi- 


mate Cost 


Num- 


B.&S. 

Gauge. 


ness of 


Capacity per 


mate 


mate 


per Foot, 


ber of 


Lead, 


Mile, 


External 


Weight 


f.o.b. Fac- 


Pairs. 


Inch 


Manufactured. 


Diameter 


per Foot 


tory, 






Meas. 




in Mils. 


in Pounds. 


in Cents 
(May, 1907). 


10 


19 


fc 


.08 to .085 


.800 


.985 


14.0 


10 


20 


A 


.085 to .09 


.760. 


.9 


12.3 


25 


19 


& 


.08 to .085 


1.07 


1.7 


25.5 


25 


20 


& 


.085 to .09 


.97 


1.30 


20. 


25 


22 


& 


.10 to .11 


.76 


.96 


14.5 


50 


19 


& 


.08 to .085 


1.41 


2.7 


42.5 


50 


20 


& 


.085 to .09 


1.28 


2.15 


33.8 


50 


22 


& 


.10 to .11 


.99 


1.6 


25. 


75 


19 


& 


.08 to .085 


1.70 


3.45 


56.5 


75 


20 


7 


.085 to .09 


1.56 


3.08 


48.7 


75 


22 




.10 to .11 


1.19 


2.2 


35.0 


100 


22 


.10 to .11 


1.35 


2.68 


43. 



1086 



TELEPHONY. 



Table n. — Capacity of Underground Telephone Cables. 

Revised by John A. Roebling's Sons Co. 















Approxi- 






Thick- 




Approxi- 


Approxi- 


mate Cost 


Num- 


B.&S. 

Gauge. 


ness of 


Capacity per 


mate 


mate 


per Foot, 


ber of 


Lead, 


Mile, 


External 


Weight 


f.o.b. Fac- 


Pairs. 


Inch 


Manufactured. 


Diameter 


per Foot, 


tory, 






Meas. 




in Mils. 


in Pounds. 


in Cents 
(May ,1907) 


25 


19 


& 


.08 to .085 


1.07 


1.7 


25.5 


25 


20 


& 


.085 to .09 


1. 


1.54 


22.5 


25 


22 


A 


.10 to .11 


.790 


1.15 


16. 


50 


19 


& 


.08 to .085 


1.41 


2.7 


42.5 


50 


20 


& 


.085 to .09 


1.31 


2.45 


37. 


50 


22 


& 


.10 to .11 


1.02 


1.86 


27.5 


100 


19 


\ 


.08 to .085 


1.96 


4.6 


74.7 


100 


20 


.085 to .09 


1.81 


4.1 


64.5 


100 


22 


| 


.10 to .11 


1.39 


3. 


46.5 ■ 


150 


19 


I 


.08 to .085 


2.33 


5.8 


99.9 


150 


20 


.085 to .09 


2.16 


5.2 


86.3 


150 


22 




.10 to .11 


1.64 


3.77 


61.2 


200 


19 


1 


.10 to .11 


2.24 


6.1 


116. 


200 


20 


| 


.10 to .11 


2.1 


5.47 


99. 


200 


22 


1 


.11 to .12 


1.84 


4.45 


75.1 


250 


22 


1 


.11 to .12 


2.03 


5.09 


89.0 


300 


22 


1 


.11 to .12 


2.21 


5.7 


102. 


350 


22 . 


\ 


.11 to .12 


2.3 


6.3 


115. 


400 


22 


* 


,11 to .12 


2.5 


6.8 


122. 



SIZES OF CABLE!. 

Conduits as now built readily take a 2^-inch diameter cable, and possibly 
one 2f-inch; so by existing construction, cables are now limited to these 
sizes, and design must accommodate itself thereto. It appears desir- 
able to have about seven varieties of cable for subscribers' lines, and three 
varieties of toll and trunk-line service. An appropriate set of cables is 
the following: 



Purpose. 


No. 
Pairs. 


Size of 
Wire. 


Capacity 
per Mile. 


Subscribers' lines, distributing cable .... 
Subscribers' lines, distributing cable .... 
Subscribers' lines, distributing cable .... 
Subscribers' lines, main and distributing cable 

Subscribers' lines, main cable 

Subscribers' lines, main cable 

Subscribers' lines, main cable 

Subscribers' lines, main cable 

Trunk line cable 


10 

30 

50 

100 

200 

300 

400 

600 

75 

50 

10 


19 
19 
19 
19 
20 
20 
22 
24 
17 
14 
10 


.085 
.085 
.085 
.085 
.110 
.115 
.120 
.140 
.065 


Toll line cable 

Toll line cable 


.050 
.035 







ANNUAL EXPENSES. 1087 



AHHTTAJL EXPENSES OF TELEPHONE CABLES. 

The following has been published as a basis for computation of the annual 
charges to be made against cables. 

' ' Even with the utmost care, and in spite of the apparent protection 
offered by conduit and sheath, underground cables gradually fail. In some 
cases life is very long, but from one cause and another, owing to extension, 
necessary rearrangement of plant, etc., a thousand and one causes operate to 
injure the cable insulation and deterioration is inevitable and must be pro- 
vided for, in the depreciation account. 

11 For underground main cable from 5 per cent to 7 per cent is a fair 
annual charge, while for laterals from 8 per cent to 10 per cent is essential. 
Aerial cable is much more exposed to injury than underground lines, for 
it is a constant prey to all sorts of additional destructive forces — sleet and 
wind storms, lightning, crosses with high-potential wires of all kinds; the 
small boy with a shot-gun or rifle, and hundreds of. other influences con- 
stantly attack it. Moreover, aerial lines have a shorter life than under- 
ground ones, as being chiefly erected in districts which are growing rapidly 
they are soon superseded by conduit work. For these reasons an allowance 
of 10 to 12 per cent for depreciation for aerial cables is none too great. 

" The maintenance to which cable wire is subjected will depend very largely 
upon the rate of growth in the exchange. Where this is rapid there is a 
constant necessity for rearranging and remodeling cable plant. Under 
such circumstances maintenance charges will vary from 2 per cent to 5 
per cent on the cost of installation. For where growth is slow, and there 
is but little change in districts, maintenance may fall as low as from H per 
cent to 3 per cent. With aerial cables 5 per cent for maintenance is the 
least charge which should be considered. Combining the charges for both 
depreciation and maintenance the annual expense for underground wire 
plant should be taken at from 5 to 10 per cent for main cables, from 10 to 
15 per cent for laterals, and from 12 to 16 per cent for aerial cables." 

JLiu-litiiiiisf Arresters. — Many telephone lines are exposed to light- 
ning discharges and to accidental contact with wires carrying currents which 
would be destructive to the telephone apparatus and liable to cause fire. 
All of some lines are exposed while only short portions of others are. In 
both cases protection is needed although the best practice distributes it 
differently in the two cases. It is generally conceded that telephone cables 
run underground in subways wholly given up to telephone purposes are 
safe, per se. 

It has been found that three different elements are necessary for com- 
plete protection. These are : first, an open space cut-out for grounding 
momentary high-potential discharges; second, a fuse of such caliber as 
to amply protect the line against abnormal currents; and third, a sneak 
current protector or thermal cut-out, which operates with a time factor, 
and protects the telephone apparatus from small currents, which by a 
gradual heading effect might destroy it. 

For lines exposed throughout their length, complete protection demands 
all three types of safety devices on each wire, and at both ends of the line. 
For lines beginning in cable and with the outer end exposed, the central 
office end fuses are usually transferred to the outer end of the cable. It 
is found economical to terminate cables upon frames or strips designed to 
hold the various protective apparatus. At subscribers' premises the lines 
terminate upon a protector built up on a porcelain block, and arranged 
with binding posts for incoming and outgoing lines and for a ground wire. 

Open space cut-outs almost always consist of two carbon blocks, the 
one grounded and the other connected to line. These are held tightly 
against either side of a small sheet of mica. This mica is perforated to 
permit of sparking between the carbons, and it is of gauge thickness such 
that 350 volts difference of pressure will strike across between the carbons. 

Fuses are of various construction and capacity. Best practice pre- 
scribes a fuse between 3 and 6 amperes rating. Some prefer a fuse mounted 
upon a strip of mica which is provided with terminal pieces of copper, and 
some prefer tubular fuses. The tubular fuse has the advantage of quite 
effectually blowing out arcs, but it has the incidental disadvantage of at 
times blowing itself all to pieces upon a violent disruption. 



1088 



TELEPHONY. 



The kinds of sneak current protector are now almost legion. All depend 
upon the gradual heating of some substance sensitive to heat, which gives 
way under some mechanical strain and opens or grounds the line. The 
early sneak current protectors were often called heat coils, as all contained 
a coil of fine wire, interposed in the circuit, which became heated upon the 
passage of current. Later blocks of carbon served as the heat generating 
member. In practically all cases certain of the parts are held in proper 
relation by fusible metal or fusible cement, and the mounting springs tend 
to disturb this relation. When the solder softens, the springs overcome 
the adhesion and thereby move the parts to open or ground the circuits. 
An old form is that shown in Figs. 19 and 20, wherein the softening of the 
solder permits the pin to slide within the coil under the pressure of spring B, 
which in following grounds the circuit. Many modern heat coils, while 




Fig. 19. Combination Protector. A, 
line-post ; F, instrument post ; B, 
German-silver spring ; CC, carbon 
blocks ; M, mica sheet ; SC, sneak 
coil; P, releasing-pin ; G, ground- 
ing-strip ; D, ground wire. 



Fig. 20. 



Plan of Combination Pro- 
tector. 



different in detail, operate similarly. A disadvantage of this type lies in 
the necessity of reheating it for repairs. Recently several types of self- 
repairing protectors have been produced. One such has a star-shaped 
latch which, in releasing the grounding spring, resets itself while still warm. 
Another depends upon shearing a heat softened washer, which latter may 
be replaced by a new one at any time. 



CLASSIFICATION OF TELEPHONE LOE§. 



Every telephone line may be included in one of three classes, according 
to the extent to which it may be interconnected with other lines. 

Under the head "Private Lines" is included all lines which have no 
facility for interconnection. They may be direct, with but two stations, 
one at each end; or they may be provided with a considerable, number of 
instruments located in different places. Private lines are largely used in 
cities by brokers, railways, etc., and in the country upon the premises of 
individuals or from farm to farm. 

House or Hotel Systems include lines which are capable of intercon- 
nection, but which serve a very limited area, usually all within the premises 
of a single proprietor. Such systems have either one central switchboard, 
presided over by an attendant or of an automatic nature, or else have a 
switchboard at every station so that each user may perform his own switch- 
ing. With this latter arrangement the system is termed "intercommuni- 
cating." 

The third class includes the great bulk of telephone lines, namely those 
connected to an Exchange and capable of interconnection to not only all 
other lines of the system, but also through toll lines, to other exchange 
systems. Every exchange district has one or more central offices, where 
the switching operations necessary for interconnecting lines are performed. 
In each exchange system the lines are treated in groups according to the 
geographical location of their stations. The territory fed by each group 
is called a district. These vary in area according to the so-called telephone 
density. 



REQUIREMENTS FOR OPERATION. 



1089 



THE (ITIKIL OJb Jb ICJK. 

Every telephone district has its central office, from which all cables and 
lines in the district radiate, and where there are provided a switchboard 
for rapidly interconnecting lines for conversation and interconnecting 
frames where lines may be interchanged, or those which cross the district 
may be connected together from the approaching to the receding wire- 
route. The equipment of a central office is the result of gradual experi- 
ence, one feature after another having been added as the demand for it 
arose. 

For a small number of lines a switchboard of the utmost simplicity will 
suffice for interconnecting them. As soon, however, as the number becomes 
so large that it requires several operators to attend to their demands, there 
is difficulty in connecting together two lines appearing in front of two dif- 
ferent operators and special provision must be made to handle such calls. 
Three general systems have been developed, the multiple, the transfer, 
and the automatic. These will all be briefly considered. First, however, 
it seems best to review the general requirements of operation and the 
method of handling calls upon small single operator switchboards. 



fKEQUntEHtEEUTTS FOR SAXISrACTOHY OPERA- 
TION OF MVITCHBOIRD. 

A telephone switchboard system must be so designed that: 

1. Every subscriber may signal the switchboard and give directions as 
to his wants. 

2. Any line may be connected to any other line. 

3. Any line may be signaled from the switchboard. 

4. Every subscriber may signal for disconnection. 

The rapidity, ease, and accuracy with which these operations may be 
carried on largely determines the value of the system, the only qualifica- 
tion being that the outlay to obtain speed shall be commensurate with 
the' saving of operators' salaries and the advantage to the subscribers. 

Small Switchboard*. — The approved form for telephone switch- 
boards is not far different at first sight from that of an upright piano. We 
have running along the front at mid-height a narrow keyboard, beneath 
which extends the supporting frame and above which extends the appa- 
ratus space. A view of a small switchboard for not over 100 lines is shown 
in Fig. 21. 

In all manually "operated" switchboards the lines 
of the subscribers terminate in signals and in switch 
sockets, and there are provided flexible connecting 
conductors having terminals which register properly 
with the contacts of the socket switches. These 
socket switches are called "spring jacks," or, for 
short, "jacks," and they consist of a guiding thimble 
behind which are arranged contact springs of sheet 
metal. The flexible conductors are usually made 
in two lengths coupled together to form a pair of 
connecting cords, and there is associated with each 
such pair some switch by means of which the op- i 
erator may connect her telephone set to them at 
will, and also means for applying ringing current 
to the conducting strands of the cords. 

Thus far the description holds for all manually 
operated switchboards, but from this point a differ- 
entiation must be made between the various systems. 
For the present the magneto system only will be 
considered. For this system the switchboard signal 
for calling the attention of the operator is a "drop," 
a type of annunciator whose latch releases a falling 
shutter: hence the name. 

When a subscriber desires connection, he drives 
his magneto and throws the drop. Thereupon the Fig. 21. 




1090 



TELEPHONY. 



operator answers by selecting one of an idle pair of coils, and inserting it in 
the jack corresponding to the signal, and then connecting her telephone 
to that pair of cords. On ascertaining the number of the line desired, she 
takes the second cord of the pair, inserts it in the jack of the desired line, 
and pushes the ringing key to call the subscriber. She then disconnects 
herself from the cords and is ready to proceed with other connections. In 
all early switchboards, the operator was required to also restore the drop 
shutter by hand and she must still so do with many. There are, however, 
a number of admirable combined drops and jacks in use, where the act of 
answering a call by inserting a plug automatically restores the drop. 

There is one more piece of apparatus which has not been mentioned. 
This is the "clearing-out" drop, which serves as a signal for disconnection 
when a conversation is finished. It is to throw this signal that one turns 
the magneto-crank before leaving the telephone. In operation the " clear- 
ing-out" drop is exactly like the calling or "line drop," and indeed, the 
line drop may serve as a clearing-out drop. As, however, a user may not 
always desire disconnection when he rings up central during a connection 
but may desire the further attention of the operator, whenever the drop 
falls, instead of disconnecting immediately, the operator must first inquire 
"Through?" or "Waiting?" Because of this, and because the listening 
key through which she must respond is associated with the cords, it has 
been found best to associate the clearing-out signal with the cords. Just 





Fig. 22. Arrangement of Ringing Keys. 



as with bells, drops may be made with high-inductance and connected 
directly across the line, or they may be made of low-inductance and become 
cut out during conversation. For clearing-out drops the former method 
is always used, while line drops are made both ways. 

Arrangement of Hinging; Keys. — It was stated above that 
in calling a subscriber an operator connects alternating-current to the 
connecting cords. This statement must, however, for accuracy be qualified, 
as were the current applied to both cords of the pair simultaneously, the 
fact that the receiver is off the hook at one of the connected stations would 
not only cause the disagreeable sensation to the listening subscriber of 
being "rung in the ear," but in addition the call would like as not fail, 
the bell of the called line being shunted by the low-resistance receiver. 
Because of these effects, ringing keys are made not only to connect ringing- 
current to the cord toward the called line, but also to separate the strands 
of this cord from those of its mate and the listening apparatus of the oper- 
ator. The exact manner of accomplishing this result will be apparent 
from the circuit drawings. 

multiple Switchboard. — As soon as the number of subscribers 
is so large that the lines are spread out before several operators, if all of 
these operators are to make connection to any line, then either must two 
or more operators assist each other on some connections, or every operator 
must be given access to all lines. Both methods have been tried, and 
each has proved successful for a certain class of service. It is generally 
agreed, however, that the multiple switchboard, that in which every opera- 
tor has access to all lines, is the more efficient. Switchboards of this type 
are made up of a number of sections or independent frameworks set side 



THE BUSY TEST. 



1091 



by side as though one continuous frame. Each such section accommodates 
two or three operators, and the keyboard is provided with a corresponding 
number of equipments. Above the keyboard there are arranged sets of 
jacks and signals, one set for each operator. These are connected to the 
group of lines which the corresponding operator must answer. Beside 
these, there is in each section another group of jacks called the multiple. 
This group contains as many jacks as there are lines entering the switch- 
board and each line is connected in every section to that jack having a 
position in the group corresponding to the number of the line. That every 
operator may have access to every line, a full group of multiple must be 
within her reach, and this fact limits the practical height and length of the 
group, and incidentally the maximum number of lines that can be accom- 
modated upon a multiple switchboard. 

As may be inferred, the connecting cords previously described serve as 
the means of making connection. As before the operator answers in re- 
sponse to a signal using the jack in her small or "answering jack" group 



Line 1 




Line 2 



Line 3 



BEpu 




Fig. 23. 



which corresponds to that signal. In calling the desired line she uses the 
nearest multiple jack bearing the number of that line. This may or may 
not be in the section before which she sits, for as the sections are placed 
side by side, the multiple is continuous from end to end of the switchboard, 
and it is often more convenient to reach into an adjacent section. 

Tlie Busy Test. — With a small switchboard it is at all times evi- 
dent to the operator just which lines are busy. On the other hand with 
the multiple switchboard, each line being accessible to many operators, 
some sort of signal must be provided to indicate when a line is busy, as it 
is impractical to attempt to find out by direct inquiry. The well-nigh 
universally adopted "busy test" is an audible one, a click being sounded 
in the operator's telephone if she attempts to connect one of her cords to 
a busy line. The guide thimbles of the jacks are expanded to expose a 
considerable surface upon the face of the switchboard, and all thimbles of 
corresponding number throughout the switchboard are wired together. A 
test battery becomes connected to this conductor whenever a plug is in 
position in any of the jacks, this being the condition with the line busy. 
Now if a circuit containing a telephone be connected to one of the jack 



1092 



TELEPHONY. 



thimbles in a manner to complete the test battery circuit a click will be 
heard in the telephone. To simplify the movements of the operators the 
tips of the connecting plugs usually serve as the test connection. Thus 
it a line is called for, the operator selects her plug and touches it against 
the thimble of the nearest jack of the desired line. If the line be busy 
the click at once announces this fact positively. If no click is heard the 
line is free and the connection is completed by inserting the plug. 

It is always a matter of perplexity to telephone users as to how operators 
may discover so quickly as to whether or not a line is busy, but from the 
above description it will be seen that the work of testing a line for busy is 
practically incidental to any attempt at making a connection with it, and 
well accounts for the quickness of the busy report. 

Series-Multiple Switchboard. — The series-multiple switchboard 
was the first developed. The fundamental circuits of this system are shown 
in Fig. 23. The jack thimbles serve for the terminals of one wire of 
the lines, while a spring in each jack serves for the other. With this 
system a low-resistance drop is used and it must be cut off during con- 



1 <r r + 



^ H JQD^ 




Fig. 24. Cord Circuits of Series-Multiple Switchboard. The Induction 
Coil and Receiver are each wound in Two Equal Sections that the 
Ground Connection may be made at an Inductively Neutral Point. 



versation. This cutting-off is accomplished by the insertion of the plug, 
as it will be noted that one side of the circuit passes through a series of con- 
tacts. As a plug is pushed home, the contact spring a rides up, upon the 
point or tip of the plug becoming clear of the point c. 

The busy-test battery with one pole grounded is shown at B. This 
must be connected to the thimble circuit which is already in use for talk- 
ing-currents. The high inductance coil / is therefore inserted, to prevent 
the alternating talking-current from being earthed through the battery. 
It is evident how a contact between the tip of a plug and the thimble of 
a busy-jack completes the battery circuit. 

This system has been extensively used and is not yet wholly superseded, 
yet it has never been entirely satisfactory. This type of board is espe- 
cially susceptible to dust, because of the numerous contacts. Dirt in any 
one of these will reduce greatly the volume of sound transmitted. The 
busy test may become over-powered by extraneous currents due to acci- 
dental conditions of the line, either to make the test continuous and " false" 
or to countermand it. With this switchboard both effects are equally 
annoying, as in one case a desired connection cannot be completed, while 



BRANCH TERMINAL OR BRIDGING SYSTEM. 1093 

in the other an existing one may be severed by a " cut-off" upon the inser- 
tion of a trespassing plug. 

Branch Terminal or Bridging* System. — The bridging 
or branch terminal switchboard overcomes these difficulties, but as origi- 
nally designed the expense was greater than the betterment of service 
warranted. Bridging switchboards did not, therefore, come into general 
use until combined with the common battery and relay signaling. A few 
words as to the magneto bridging board will not be out of place. For 
this system, the jack thimbles are divided into two parts, the front one 
having the larger bore and being used solely for the busy test. The rear 
one serves as the line connection. The second line connection and two 
auxiliary connections are made through springs. Fig. 25 shows a part 
of a jack with a plug inserted. The plug has three parts: a tip, a collar, 
and a sleeve. The cord strands are connected to the tip and sleeve only. 
The collar serves merely as a short-circuiting piece between the auxiliary 
springs, and thereby connects the test battery which is wired to one of 
them to the test ring which is wired to the other. This may all be traced 



.K .Line!. 




Fio. 25. 



Fig. 26. 



from the circuit diagram wherein one of the jacks is lettered to correspond 
to the drawing of the plug and jack. The jacks have no cut-off feature, 
and thus the drops must be wound to high resistance and inductance. 
Furthermore, as the drops are connected to the talking-circuit and as those 
of different lines are mounted close together, they might be subject to 
mutual inductive effects to cause cross-talk, unless magnetically shielded. 
Because of this, the drop coils are encased in tubes of iron, which become 
entirely closed by the armature of the drop, and hence dispose of all stray 
field. 

The omission of a cut-pff feature also renders it necessary to lock the 
drop shutters during connection. Otherwise any slight current impulse, 
or any ringing-current sent upon the line, would throw not only the clear- 
mg-out drop but also the line drops. This would signal the answering 
operator of the called line, who has had nothing to do with the connec- 
tion, and who in answering disturbs the call without the ability to assist 
in any way. The locking of drops is accomplished by an auxiliary coil 
which acts upon the drop shutter directly, to restore it and to hold it up. 
The current for this locking-coil is furnished by the busy-test battery, 
the circuit being closed by the plug collar just as for the busy test. 



1094 TELEPHONY. 



Transfer & y*tem*. — Those systems in which each subscriber's 
line has but a single terminal jack, and two or more operators assist each 
other in completing connections, are called "transfer" systems. Prob- 
ably the oldest is one in which each section of the switchboard accom- 
modates 100 subscribers' lines, and there extends a series of transfer lines 
from each operator to every other. Upon ascertaining the number of a 
desired subscriber, out of reach, an operator selects a non-busy transfer 
line extending to the position at which the line of this number appears, 
and connects the calling subscriber thereto. By means of an order circuit 
with which she may connect herself at pleasure, and which connects di- 
rectly with the head telephone of the operator at the desired section, she 
gives an order for the connection of the wanted line and the proper transfer 
line. 

In another system the pairs of connecting cords of one position are con- 
nected to branch lines having single cords at each of several other sections, 
the transfers being made by means of these. In other systems the transfer 
lines have jacks at one end which multiple throughout the switchboard, 
while at the other end they have a single cord and plug at one position 
only. 

The so-called "Express" system is a kind of transfer system where three 
operators assist in each connection. One responds to the signal by extend- 
ing the calling line to a second operator who answers, ascertains the desired 
number, and orders a third operator to extend the line to her position. She 
then connects the two extended lines and is responsible for the call. 



Relative Value of Multiple and Transfer Systems. 

There is no transfer system where there is not some^ delay caused by 
the necessary co-operation of two persons, and although this delay may 
be slight where there are many connections to be handled, it may readily 
amount to the entire time of an extra operator. Furthermore, in times 
of excessive traffic due to a sudden emergency, this delay may result in 
the complete break-down of the system. The success of the transfer sys- 
tem is in direct relation to the efficiency of its auxiliary signals, which 
signals indicate at a glance the complete condition of the transfer lines, 
e.g., as to whether either or both ends are connected to subscribers, signals 
for connection, for disconnection, to indicate mistakes, etc. The advan- 
tage of the transfer system in comparison with the multiple system is its 
cheapness. The cost of apparatus with this latter goes up almost as the 
square of the number of subscribers and for a large switchboard is enor- 
mous. A 1000-line multiple switchboard having 200 answering jacks in a 
section, will require 5 sections of multiple plus an extension for each end 
operator of £ of a multiple. This amounts to 5700 multiple jacks. Add 
to this 1000 answering jacks, gives a total of 6700. Contrast this with a 
5000-line board, which, by the same reasoning, has 25 sections and 133,300 
jacks. Consider that these jacks must all be cabled together and some idea of 
the vast cost may be obtained. This cost must be offset by the efficiency 
of operation, and that it is so offset is best testified to by fact that practi- 
cally all the large manual switchboards thus far installed are of the mul- 
tiple type. 



OYE CEHTXRAI OIIKE vs. IEVERAI, 

Most of the larger cities now have several central offices each with its 
own switchboard, yet the lines of all must be interconnected almost as 
often as those of the same office. Connections between two different offices 
must be handled by some transfer method involving two operators, with 
the consequent delay, and it would, therefore, seem at first sight advis- 
able to concentrate all lines in one switchboard. That for a small com- 
munity this is the case can hardly be questioned, but as the territory reached 
grows the cost of the wire plant for the lines increases so fast that the 
division of territory becomes imperative. 



TRUNKING. 1095 

It may not be apparent as to why the establishment of additional central 
offices effects a saving, as lines must be provided between these. How- 
ever, it must be understood that there is never more than a small per- 
centage of the lines of .a system in use at once, and it is only necessary to 
provide sufficient tie lines, trunk lines as they are called, to continuously 
take care of this percentage. The usual maximum number of connec- 
tions provided for in designing a switchboard is about 20 per cent of the 
total number of lines. Where there is more than one central, it is usually 
assumed that the number of calls local to each switchboard will be a slightly 
greater proportion of the whole number of calls than the ratio of the num- 
ber of its subscribers to the total number in the system. 

Leaving out of consideration the question of economy there is another 
ample reason for several offices in some cities. This is that there is no type 
of switchboard which can accommodate satisfactorily a sufficient number 
of lines. Switchboards designed for an ultimate of 10,600 lines are now 
in use, but this seems to be about the practical limit, although in a number 
of cities the number of lines is far greater than this. 



Those calls which involve two central offices are termed "trunk calls," 
and the ratio of the total number of these to the total number of calls 
expressed as per cent of the whole is called the "trunking percentage." 
This of course varies from zero, where there is but one switchboard, to 
well up to 90 in the largest cities. When the trunking percentage is over 
50 this kind of traffic becomes the more important, and every effort must 
be made to handle it quickly and positively, and without too great ex- 
pense either for lines or operators. 

The most efficient method thus far devised is that known as the calling- 
circuit method. By this method each central has two kinds of trunk 
lines, termed respectively outgoing and incoming trunk lines, and each 
is used exclusively for calls in the direction its name indicates. Of course 
the incoming lines at one central are but one end of lines outgoing from 
some other central. The switchboard at each central is divided, one part 
being termed the subscribers' switchboard and the other the incoming 
trunk switchboard. The outgoing trunks terminate in jacks and multiple 
throughout the subscribers' sections, forming a group usually placed be- 
neath the multiple line jacks, but above the answering jacks and signals. 
These outgoing lines do not appear at all on the incoming sections which 
have the subscribers' line multiple only. At these latter sections the 
incoming trunks terminate at the keyboard in single plugs and cords. 
Besides the trunk lines there are wires called calling-circuits which extend 
between each two offices, from the subscribers' board at one to the incom- 
ing trunk board at the other. At the subscribers' switchboard the calling- 
circuits are available to every operator, and she may connect her telephone 
set to any one of them at will, by merely depressing one of a group of call- 
ing-circuit keys. The other ends of the calling-circuits connect directly 
with the telephone sets of the operators who manipulate the incoming 
trunk switchboard; each calling-circuit terminating at that position where 
the corresponding group of incoming trunk lines terminates. 



Method of Operating: Circuit Trunks. 

When a subscribers' operator at one central receives a call for a line of 
another central, she depresses the proper calling circuit key, and speak- 
ing directly to that trunk operator facing trunks from her own office, 
gives the number desired. The distant operator can tell at a glance which 
trunks are not in use, because the plugs of such are at the keyboard. She 
selects one and assigns it by giving its designating number. Upon hear- 
ing this assignment the subscribers' operator proceeds to connect the call- 
ing subscriber to the nearest jack of the outgoing trunk, which bears the 
same designation. 



1096 TELEPHONY. 

In the meantime the trunk assigning operator has with the plug of the 
incoming trunk tested the line of the asked-for subscriber of her district, 
and either connected the trunk thereto, and rung the subscriber, or he 
being busy has connected a hum or other busy signal to the trunk to sig- 
nify this fact. 

It must be understood that the incoming trunk operator can never talk 
to any of the subscribers, i.e., she cannot talk upon any of the lines but 
merely upon her calling circuit. 



Auxiliary Trunk Sig*nals. 

A circuit trunk system will only work satisfactorily when equipped with 
certain auxiliary signals. One of these has already been mentioned. This 
is the busy signal. Sometimes this is an audible signal and sometimes 
a visual signal such as the flashing of a lamp. Such signals are introduced 
upon the trunk by the insertion of the trunk plug in a jack to which the 
signal currents are wired. • . 

Sometimes a phonograph is used. This repeats, " The line is busy; 
please call again, " or some similar phrases. Such an arrangement in- 
cludes a telephone set, the transmitter of which is agitated by the phono- 
graph reproducer. 

The disconnect signal is an almost indispensable auxiliary. It usually 
takes the form of a small incandescent light in front of the trunk operator. 
This glows when a trunk is to be disconnected from a line. As the trunk 
operator cannot listen on a trunk, she has no means of discovering just 
when a conversation is completed. The subscribers' operator can, how- 
ever, listen, and she has in addition, her regular clearing-out signals. Upon 
discovering or being notified that a conversation is completed, she clears 
the cords from the jacks without reference to the trunk operator. The 
disconnect signal lamp near the plug socket at the incoming end of the 
trunk glows at once, indicating to the trunk operator which connections 
she must take down. 



Ring; Down or Common Trunks. 

Such an elaborate trunking system as that just described is, of course, 
economical only when the number of calls between two offices is consider- 
able. This is evident when it is understood that two lines, viz., the calling- 
circuits, are required solely for carrying out the system. When the traffic 
is small, but one group of trunks is used. These trunks end in jacks and 
signals at both ends. When a call must be passed over such a trunk, the 
operator tests through the group until she finds a trunk not busy, and 
then rings upon it. This throws the distant signal. When the distant 
operator answers, the call is passed to her and handled by her as though 
direct from a subscriber. Such a call, involving two pairs of connecting 
cords, has, of course, two clearing-out drops as disconnection signals. This 
system is much slower than the circuit system. 



COMlflO]* BATTERY SYSTEM. 

As mentioned in the description of telephone instruments, in some 
systems the individual transmitter batteries are replaced by a storage 
battery, located at the central office, which serves for the entire system. 
Such systems are variously called Centra! Energy, Central Battery, or 
Common Battery Systems. There have been suggested a number of dif- 
ferent ways of applying the current from the common battery to the uses 
of the transmitter, but the only one of practical importance thus far is 
that in which the current is applied to the. transmitter directly, the circuits 
being variously arranged to permit of this. 



CIRCUITS OF COMMON BATTERY SYSTEMS. 



1097 



One of the primary features of all common battery systems is the use 
of direct current or battery signaling from the subscriber to the central 

office. This permits of the omission -rt 

of the hand generator, as all sig- i pCZlT 

nals to the central office whether 
for connection or disconnection 
are made by the mere closing or 
opening of the line circuit. 



Rudimentary Common 
Battery Circuits. 

In the two circuit diagrams here- 
with given are shown the rudi- 
ments of two common battery sys- 
tems. In the first (Fig. 27) are 
shown two lines connected together 
and supplied from a common bat- 
tery. In this system the trans- 
mitter and receiver at the substa- 
tion are shown in series. This is 
a practical method of connection, 
but has been largely superseded by 
others giving more powerful re- 
sults. The ringing keys at the cen- 
tral are omitted from the circuit to 
simplify the diagram, but they are 
wired exactly as earlier described. 
The battery is connected to 
the line through the retardation 
coil. The left-hand receiver is 
shown off the hook and the bat- 
tery circuit is complete, flowing 
out through the signal. This signal 
being energized raises its target 
above the shield. The right-hand 
instrument has not yet responded 
and its circuit is open at the hook 
switch. No current flows through 
the bell circuit because of the con- 
denser. The right-hand signal tar- 
get is behind the shield. 

Suppose the response of the 
right-hand station to be made, 
".urrent will then flow steadily to 
both stations. This steady current 
will magnetize the core of the re- 
tardation coil. Now when any 
sudden change in the resistance of 
one line is made, due to the agita- 
tion of the transmitter, there will 
be a simultaneous change in the 
current to the other. The reason 
for this is twofold; first, there is 
a reapportionment of currents be- 
tween the lines due to the resist- 
ance change ; and secondly, the 
rapid change of current affects the 
magnetization of the coil, causing 
either inductive discharges to the 

line, or absorption of the current p IG# 27. 

as the case may be. Additional ' , . 

pairs of lines may be wired off the battery from additional coils, as indicated, 
up to the current capacity of the battery. 




1098 



TELEPHONY. 



In the second circuit (Fig. 28) it will be seen that the arrangement of 
the subscribers' instruments is considerably changed, an induction coil being 
used. Another difference lies in the substitution of a sort of quadruple 
wound transformer, called a repeating coil, for the retardation coil. It is 
mere chance that the retardation coil and series connected instruments 
should be associated, as these instruments will work equally well when 
wired to a repeating coil, provided the parts be properly proportioned. 

The operation of the repeating coil is almost self-explanatory, the current 
changes in one pair of coils being inductively repeated by the other through 
electromagnetic induction. The distinction between an induction coil 
and a repeating coil lies in the fact that the latter has a ratio of transform- 
ation of unity, i.e., all its coils have the same number of turns. 



SUSCRIBER j 




Fig. 28. 

With this repeating coil system as with the other, many lines may be 
simultaneously supplied by the same battery, each pair of lines, however, 
having an individual repeating coil. The battery must be of extremely 
low internal resistance, for otherwise the varying currents supplied to 
one line might cause a corresponding potential fluctuation at the battery 
terminals; and thus cause minute current fluctuations on all lines con- 
nected thereto. The result of this is battery cross-talk, or battery noise. 
A storage battery of large current capacity has proved best, this usually 
consisting of from 11 to 25 cells according to the circuit system used, the 
corresponding mean voltages ranging from 24 to 52. 

r.utip Signals. 

The magnetic signals shown thus far are likely to be replaced by incan- 
descent lamps controlled by relays. These latter are similar to telegraph 
relays in function, although usually of far more compact design. The 
contacts of the relays control circuits local to the central office, which in- 
clude miniature incandescent lamps, the glowing of which gives the signals. 

Sockets of the general appearance of jacks are used as receptacles for 
the lamps, which are generally of tubular form. The lamps carry terminals 
which register with terminal springs in the sockets. As a cover for the 
lamp socket, a bull's-eye of opalescent glass is mounted with the convex 
side outwards. This, by internal reflection, glows throughout, and renders 
the light visible from a considerable angle. 



Circuits of Common Rattery Switchboards. 

Common battery switchboard systems are now of many types, and new 
schemes are continually appearing. All, however, may be referred back 
to one of the two fundamental schemes. The first switchboards to meet 
general adoption had jacks wired on the bridging system, each of which 
has two spring and one thimble contact. Three wires run throughout the 
board for each line, and this has led to the name "three-wire" system, 
this name having been given in distinction to a later "two- wire" system. 



CIRCUITS OF COMMON BATTERY SYSTEMS. 1099 

Each system has many modifications and developments to fit different 
conditions and the different ideas of various inventors. It is possible, how- 
ever, to consider here but one system of each kind, and these with 
regard to fundamentals only. 

Three-Wire System. 

The subscriber's line circuit is bridged to the multiple and answering 
jacks and in addition is carried to two contacts of a relay, called a "cut-off " 
relay. The armature of this relay is arranged to cause the opening of two 
independent circuits when the relay is energized. From the cut-off relay 
contacts the branch circuit leads on one side directly to the battery, 
while on the other it is carried to the coil of a single contact relay and 
thence to battery. This latter relay is called the "line" relay, and it is 
evident that it will be energized whenever the telephone is removed from 
its hook if the contacts at the cut-off relay be closed. 

Associated with the answering jack of the line is a lamp signal whose 
circuit is controlled by the line relay. 

The cord circuits for interconnecting lines are used as with the switch- 
boards already described. There is, however, a most admirable feature 
added. This is what are called the supervisory signals, by means of which 
an operator may know the instant that a conversation is completed. 

These supervisory circuits are controlled jointly by the third-wire cir- 
cuit, in which they are wired, and by relays wired directly in the talking- 
circuit. Referring to the circuit diagram, the battery circuit may be 
traced through the repeating coil and supervisory relay to the plug, jack, 
and subscriber's instrument. It is also evident that the rapidly alternating 
current will be greatly attenuated in passing through the inductive winding 
of the relay unless some shunt circuit is provided about it. This is usually 
done, the relay winding being the combination of a non-inductive and an 
inductive winding in parallel. A condenser will serve as a shunt, and 
many consider this the more desirable arrangement. 

The supervisory lamps are designed to operate upon 12 volts, one half 
the battery potential. There must be placed in series with them a resist- 
ance equal to that of the lamp, approximately, 120 ohms. This is made 
up as follows : 83 ohms of resistance coil, and 30 ohms in the cut-off relay 
winding, with an allowance for 7 ohms in the wiring. Under these cir- 
cumstances, the lamp glows. If now the supervisory relay close the shunt 
circuit about the lamp, the combined resistance of shunt (40 ohms) and 
lamp is but 30 ohms. The total resistance is then 150 ohms, correspond- 
ing to a pressure at the lamp of but T %% or £ of the battery voltage, too 
little to affect the lamp. 

The progress of a call may now be traced. The receiver being removed 
from the hook at the calling station, the line lamp lights, calling attention. 
The operator responds with a plug and cord. The corresponding super- 
visory light fails, for as soon as its circuit is closed the shunt becomes 
operative, as the receiver is off the hook and current flows through the 
supervisory relay. 

At the instant of inserting the plug, the cut-off relay is energized and 
breaks the circuit of the line relay, cutting it off the line. The line lamp 
of course goes out. Incidentally the busy test battery is put upon the 
jack thimbles, as these are at a potential corresponding to the drop of 
potential in the cut-off relay, viz., 4 volts. 

The operator, using her listening key, ascertains the desired number and 
connects to that line and rings. As long as the station, fails to answer, the 
corresponding supervisory lamp remains aglow, as the shunt circuit is 
open. When the receiver is removed from the hook, the shunt closes. 
It must be noted that the cut-off relay of the called line operates upon 
the insertion of the calling plug in its jack, and thus there is no possibility 
of affecting the line lamp of this line. 

Trunking is accomplished by exactly the same methods as with magneto 
svstems. The circuits used are so various that it is useless to attempt to 
choose one as standard. One of the most interesting features largely 
adopted with circuit system trunks is that of through supervision. By 
this is meant that the subscriber's operator, at whose position the call is 



1100 



TELEPHONY. 




1 40 U Coil 

-hrV^rVr-' ___ 24v 



Fig. 29. Circuits of Three-wire System. Batteries 5, 5, B, are one 
and the Same Battery. 



CIRCUITS OF COMMON BATTERY SYSTEMS. 1101 



first received, has in her lamps a direct indication of the position of the 
hook switch of a subscriber of another central office connected through a 
trunk line. 

Two-Wire Systems. 

There are so many different schemes for two-wire systems and this 
system is of such recent introduction that it is difficult to select any one 
which might be considered standard. One of the earlier types is shown, 



Line 
Circuit 



Relay 



tfoT CQJ 



< C pQ Line Lamp 

Cord Circuit ' ^ 



supervisory 
Lamp 



Relay ^T 



tm 



ca 



^ 



C3a " ion 



Fig. 30 Circuit of Two-wire System. Relays A, A, serve as 
Retardation Coils. 




Fig. 31. Recent Common Battery Subscriber Set Circuit. 

however, in Fig. 30. The cut on relay severs the connection between the 
line relay circuit and the line, and at the same time connects this latter to 
the jack circuits. The supervisory circuit is self-evident. It might seem 
that the contact with the jack thimble, in testing for busy, might interfere 
with a conversation by shunting off part of the current. This is avoided 
by reducing the shunted current to the smallest amount and making this 
effective in a very sensitive relay. This relay in turn closes a circuit which 
clicks the receiver. This test apparatus and the ringing and listening keys 
are not shown in the diagram. 



1102 TELEPHONY. 

Common Battery Instrument Circuits. 

The circuits of instruments are also of many sorts. One kind largely 
used is shown in connection with Fig. 28. In this the induction coil primary 
and secondary have a ratio of turns of 1 to 2, and of resistance of 2 to 1. 
The transmitter affects the repeating coil directly, and in addition through 
the induction coil causes a more intense current to be sent out on the line. 

Another type of circuit is shown in Fig. 31. Here the coil shunted 
about the receiver serves as a low-resistance path for the transmitter current, 
while the voice currents find a path through the receiver. 



party :m]¥:es. 

Demand for party lines has existed since the early days of telephony. 
Nothing really successful was accomplished in this direction until the 
advent of the Carty bridging-bell. With series bells good party-line 
service with a two-wire line is out of the question, as all voice currents must 
necessarily traverse the bell-magnets of all idle stations. The bridging- 
bell, previously described, connected across the line-circuit and of so high 
impedance as not to appreciably shunt the voice-currents, can be used 
for a number of parties up to twenty or more so far as electrical considera- 
tions go. Practically the number of stations is limited, for with the unmodi- 
fied bridging-bell a code of signals must be resorted to, to distinguish 
between stations. As all bells respond to all signals, confusion and annoy- 
ance to subscribers limits the number of parties. 

With the magneto system the signal, one ring, is reserved for calling 
central. The stations must then have signals from two up; and when 
their number is large, a differentiation is made between long and short 
rings. With the common-battery system all signals may be assigned to 
stations. 

Selective Systems. 

Before the bridging-bell was introduced, attempts were made to solve 
the party-line problem by some sort of selective device, which, by respond- 
ing to a code of signals, would succeed in ringing the desired party to the 
exclusion of others. At first all systems were what are now known under 
the generic name — " step-by-step systems." Each station has a point 
switch, the arm of which is driven by a motor. The motor is controlled 
from central, and drives its mechanism in a series of steps. 

All motors run synchronously and they are arranged to connect the 
bells one after the other in operative relation to the line. 

Another and later type of selective system has been developed, in which 
the bells work entirely independently of each other and of any motor 
device, the selection of any particular bell being dependent upon the com- 
bination of currents sent out upon the line. 

Step-by -Step Systems 

Probably hundreds of step-by-step mechanisms have been invented, 
but it can scarcely be said that any are in general use. Both spring and 
electrical motive power have been tried, but the fact that this system places 
all the more complicated apparatus at the subscriber's station, where it 
is most troublesome to all concerned to get at it for repairs and adjust- 
ment, weighs too heavily against all step-by-step systems. 

Two-Party Selective Systems. 

The simplest selective system is the two-party system, largely used by 
the Bell companies. In this system one bell is wired to ground from each 
side of the line, bridging-bells being used. In ringing a party the ringing 
current is connected to ground on the one hand and the proper side of the 
line on the other. 



PARTY LINES. 



1103 



JFour-JParty Systems. 

Four-party systems seem to be the most popular, and there have now 
been many schemes for accomplishing selection. The so-called Newburgh 
system uses what are termed "biased" bells. These are polarized bridging- 
bells with the armatures biased to always come to rest in the same position. 
The biasing means is usually an adjustable spring acting upon one end of 
the armature. Two such bells are wired to ground from each side of the 
line. The currents used are impulse currents of one sign only, being 
comprised of a series of half waves of alternating current separated by an 
equal period of no current. Two of the bells, one on each side of the line, 
are connected to respond to positive impulses only and to fail on negative 
impulses, these latter merely assisting the spring to hold the armature 
stationary. 

After an armature has been moved by a current impulse of the proper 
sign, the spring returns the armature during the period of no current. 
The other two bells are similarly arranged, but are connected to respond 
to negative currents. 

For the common-battery system the Newburgh system becomes mod- 
ified as it will not do to have permanent grounds upon the line, and the 
insertion of a condenser will not help matters as it converts the impulse 
currents to alternating currents to which all bells are responsive. The 




Alt. Cu 
Relay 




mL 



Fig. 



32. Four-Party Newburgh System Arranged for Common Battery, 
Two Stations wired from Line A, and Two from B. 



arrangement usually adopted is indicated in Fig. 32. The relays at all 
stations are in series with condensers and all operate irrespective of the 
kind of current impulses. These relays connect the bells to line and that 
responsive to the impressed current rings. 

There are other four-party systems in which the bells respond to changes 
of frequency of the current, the bells being wired with such combinations 
of inductance and capacity as to make the response and failure positive. 
Other systems use combinations of direct with alternating currents, while 
at least one, the "B.W.C.," which at one time bid fair to be very popular 
but which has now largely gone out of use, depends entirely upon various 
combinations of direct currents. 



method of Obtaining* Impulse Currents. 

t The impulse currents for the Newburgh system are obtained from the 
ringing generator by the use of an auxiliary two-part commutator one 
.segment of which is connected to one of the usual alternating-current ter- 
minals and the other of which is either left blank or connected to the 
other alternating-current terminal, if this latter be grounded. Two brushes 
diametrically opposite each other bear upon the commutator, and these 
are adjusted with reference to the field so that the passage from one seg- 



1104 



TELEPHONY. 




Fig. 33. Arrangement of Generator for Obtaining Impulse Currents. 

ment of the commutator to the other occurs just at the zero or point of 
reversal of the alternating wave. 

Between either commutator torush and a collecting ring an impulse 
current can be obtained. 



CE.\XHAL OJFFICE APPARATUS AUXILIARY. 



Besides the switchboard there is in every central office considerable 
auxiliary apparatus. The size of the office generally determines the kind 
required. Of such apparatus, in every office of any size, the main distrib- 
uting frame is of prime importance. As it is imperative that all stations 
be given as near continuous service as possible, and as it is always dis- 
tasteful to subscribers to have a change of number, it is found necessary 
to have some flexible link in the wiring between the line cables and the 
switchboard. The main distributing frame provides the facility for this 
connection. A steel framework carries strips of terminals, to some of 
which the switchboard cables are connected and to others the line or out- 
going cables are connected, each pair of wires being assigned and connected 
to one pair of terminals according to some carefully planned scheme. A 
flexible or temporary connection, usually termed a "cross connection " is 
run from any one pair of terminals to any other, as the service may require. 
Main distributing frames are usually arranged with two accessible sides. 
The terminals upon one side are vertical and are supported from a set of 
uprights so as to form a series of vertical runways between the terminal 
strips. On the other side the terminals and framework are usually ar- 
ranged in horizontal planes that horizontal runways may be formed. With 
such construction, wire may be run with the greatest ease between any 
two terminals. 

Of late years it has been considered good practice to use the main frame 
as a support for the central office thermal cut-outs and carbon plate arresters, 
the vertical side of the frame having arrester mountings substituted for 
the simple terminals. ^ The strips of arresters are often called arrester bars. 

The intermediate distributing frame has only come into universal use 
lately. It is similar in construction to the main frame, but its purpose is to 
provide a flexible link between the multiple and answering jacks. It is 
clearly impracticable to have the multiple jacks arranged in any order save 
that indicated by the line numbers. The wiring of these jacks is therefore 
made permanent once for all. On the other hand it frequently becomes 
necessary to change the position from which any line is answered, in order 
to properly distribute the work between the different operators. For 
example, Nos. 1 to 50 may call frequently enough to require two operators 
to properly care for them; while Nos. 50 to 150 may require but one operator. 
It would clearly be impossible to distribute answering jacks and signals to 
meet^ such conditions while designing a switchboard. The question of 
distribution must be met by the intermediate frame. The multiple jack 
wiring connects to one side, and that for the answering jacks and signals 
to the othfT, and the cross connection serves to connect any answering jack 



AUTOMATIC EXCHANGE SYSTEMS. 1105 

to any multiple jack. It is of no moment that answering jacks be placed 
in an order having no relation to the line number, for they are never sought 
for by number, but only in response to an associated signal. 

Of the other apparatus the most important is the power plant. In mag- 
neto offices this comprises a small four-volt storage battery, sufficient to 
energize the operators' transmitters and to operate miscellaneous signal 
lamps and magnetic signals. A power-driven generator for charging the 
battery and power-driven ringing machines are also required. 

For common battery offices the battery is usually of from 16 to 52 volts 
and of large capacity. The charging generators must be correspondingly 
large, having sometimes as great as 20 kw. output, which at low voltage 
means a big and heavy machine. 

It might seem at first thought that the battery could be omitted as 
generators must be provided to charge them, the generators being used 
directly. Unfortunately the difficulty of making a generator which will 
produce a current sufficiently smooth to permit of any service whatever 
without a battery is so great that the use of the battery is a necessity. 
The battery smooths out the irregularities caused by the commutation of 
the generator, which irregularities, of no moment at all in any other service, 
are entirely disastrous to telephony because of the noise introduced. 



AUTOMATIC EXCHANGE SYSTEMS. 

There are in operation quite a number of automatic exchange 
systems. These range in size from accommodations for a few lines, to a 
capacity approaching 10,000 lines. The subscriber's instrument for all 
automatic systems is provided with a numbered dial and a movable indi- 
cator. This latter is set in some manner to indicate the number of the line 
desired. When released it returns automatically to zero and in so doing, 
through the agency of auxiliary contacts, it causes a selecting apparatus 
at the central office to make connection between its line and the desired 
line. 

Almost all automatics depend upon the multiple principle. Each line is 
assigned a switching mechanism before the moving switch arms, of which are 
arrayed contact points for all other lines in the district. There is thus one 
multiple for each line. The multiple line contacts are arranged in consec- 
utive order. For small systems they are often placed as radii of a circle 
over which the contact arms move. In such systems the motor for the 
switch arm requires but one motion, that of revolution. In other small 
systems the contacts of the multiple are arranged in a single row. The 
switch motion then becomes a simple longitudinal one. As the capacity 
grows, the multiple contact points assume the form of a superimposed series 
of rows, the contact of each line occupying a position which can be located 
by its co-ordinates. The tens of the number usually correspond to the 
vertical and the units to the horizontal co-ordinate. For such systems the 
moving switch arms require two motions. If the points be arranged upon a 
plane surface, these motions are an elevation and a transverse motion. If 
the contacts be arranged upon the inside of a cylinder the motions are 
elevation and rotation. 

# Suppose with such a system Number 79 is desired. Seven elevating 
impulses will be sent so that the switch arm will traverse the vertical co- 
ordinate. Then nine transverse or rotating impulses will cause the arm 
to traverse the horizontal or units ordinate and rest upon the point 7-9. 

A second system, more akin to a manual switchboard, has been invented. 
In this system the lines have each but one set of terminals, but there is 
provided a system of circuits corresponding exactly to the cord circuits of 
manual switchboards. The starting of a call causes one of these circuits 
to first become connected to the calling line and then to the called line 
which is automatically rung up. 

When automatic systems are used for a great number of lines the method 
of completing calls, while becoming little more complicated for the user, 
becomes excessively more so at the switchboard. It is not possible to 
attempt to explain here the scheme of operation, nor is it possible to con* 
Bider the details of any of the smaller systems. 



1106 



TELEPHONY. 



SIMULTANEOUS USE OF MHJES. 

Efforts have been made to use telephone lines for two distinct purposes, 
simultaneously, in two ways. The first has been but partially successful 
and contemplates sending more than one telephone message at a time. 
The second, very successful, and in everyday use permits of the simulta- 
neous transmission of telegraph and telephone messages. 

Duplex and multiplex telephony depends upon the arrangement of the 
various instruments with regard to the conductors so that each telephone 




Fig. 34. Duplex Telephony. 

connects equipotential points of the system with respect to all other instru- 
ments save its mate. Thus in Fig. 34, if the resistance and capacity upon 
the upper branch of the parallel line equal exactly that of the lower line, 
both in value and distribution, the terminals of both T 3 arid T 4 will connect 
equipotential points with respect to instruments" T x and T 2 . Similarly will 




Fig. 35. Multiplex Telephony. 

T t and T 2 connect equipotential points with respect to T 3 and T 4 . So also 
in the multiplex circuit it will be found that equipotential points are used. 
Retardation coils serve better than resistances, in such systems, as these 
may be connected to form an inductive path for currents, the passage of 
which should be resisted to prevent loss of volume and to form a non-induc- 
*vve path for those currents which should be conducted. 

The difficulty with such systems has lain in the inability to make the two 
rfides of the various lines exactly alike, with the result that the supposed 




Fig. 36. 



LIMITS OF TELEPHONIC TRANSMISSION. 1107 

equipotential points were not such. Under this condition the two circuits 
overlap and cross-talk. 

The method employed for rendering telegraph signals of no effect upon 
telephone lines has involved the rounding of the telegraph current impulses 
to such an extent that there is no change abrupt enough to affect the tele- 
phone. The first system was invented by Van Rysselberghe and after 
modification is used to-day. Such a system is indicated in Fig. 36, taken 
from Maver's American Telegraphy. It will be seen that one pair of wires 
provides simultaneously for one telephone and two telegraph messages. 

Another system in use sometimes called "Simplex, " provides for but one 
message of each kind for each two wires. Simultaneous telegraphy and 
telephony is used extensively on long distance lines, and the application of 
this system is called "compositing," while the coils, condensers, etc., are 
called a "composite set." 



UUIITS OF TEJLEJPIIOJTIC T« iX^I§SIOi\. 

The limiting distance through which commercial telephony is practi- 
cable is as yet an unknown quantity. Every few years the idea becomes 
general that the working limit has been reached, when some new invention 
or construction permits of a further ext ension. The limit for the magneto 
transmitter was extended by the Blake transmitter, and then by the solid 
back type. The bipolar receiver has replaced the single pole. Dry and 
LeClanche batteries were superseded by the more powerful and steadier 
Fuller cell and this in turn by the storage battery of practically constant 
strength. In the direction of the line the grounded circuit gave way to 
the metallic and the iron and steel wire to hard copper. This latter has 
been used in constantly increasing sizes until the commercial limit seemed 
to be reached at number six B. & S. 

< The most obvious way of increasing volume is improvement in the sen- 
sitiveness of the transmitter and receiver. Improvements in this direction 
have been at a standstill for some years. Nothing has been found to better 
the solid back, except increase of current, and the effect of this is tem- 
porary only, resulting disastrously very soon. Improvements in the 
receiver, on the other hand, prove a disadvantage at once, as with a sensi- 
tive receiver the effect of line disturbances grows at a rate entirely incom- 
mensurate with the increase in volume of transmission. 

Another method of extending the limit for speech transmission attempted 
almost since the beginning of telephony is the use of a repeater, in a manner 
exactly similar to that which has worked so successfully in telegraphy. 
Up to this time, however, no success has been met with along this line. 
No repeater has as yet been developed which does not do at least as much 
harm as good. 

Within the l as t few years an entirely new means of improving the effi- 
ciency of transmission has appeared. This, briefly, consists in the change 
of the electrical^ characteristics of the line by means of auxiliary induc- 
tances or capacities or auxiliary conductors in a manner such that the 
telephone currents are transmitted with better efficiency. 

The first method to be developed was that invented by Dr. M. I. Pupin 
and termed "loading." Dr. Pupin showed how coils of certain known 
inductance can be spaced along a line and thereby improve its efficiency. 
The adaptation of such a system of course requires much study and experi- 
ment. i Coils must be designed which are ncn-interfering and the energy 
absorbing propertiesof which are sufficiently reduced so that there is a 
net gain in transmission. Lines are now in use equipped with this system, 
put it can scarcely be said to have passed the experimental stage. The 
improvement in transmission thus far is, as far as can be learned, about 
as 2^ to 1, when all conditions are normal. When, however, the insulation 
of a line is reduced irregularly as by moisture, the effect upon a loaded cir- 
cuit is at times very disastrous. 

Two later systems have be^n invented. One of these involves putting 
condensers in series with the line and inductances across the line, at regular 
intervals. This system has as yet been placed upon no practical basis. 

The second of these systems has been developed in theory to the most 
encouraging state. It may be termed the method of "distributed shunts." 



1108 TELEPHONY. 

The theoretical condition to be fulfilled is that of equal velocity of trans- 
mission for waves of all frequency; thus the condition for no distortion of 
the wave forms. The inventor has found that to fulfil this condition he 
must increase the inductance of the copper line by plating it with magnetic 
material such as nickel or an alloy of iron and nickel and that it must be 
shunted at stated intervals. The shunts consist of graphite or other non- 
inductive resistances of many thousand ohms resistance each; spaced at 
equal intervals of from one to several miles. 

MOTES OUT COST OF IEIEPHOHE PLAIT. 

That the cost of telephone switchboards for large central offices increases 
faster than the number of lines is of course evident from what has been 
said concerning switchboards. It must be pointed out, however, that even 
when the plant is considered as a whole, the cost for large plants is greater 
per station than for small. The following by H. S. Kerr in the American 
Electrician may throw some light on this subject. 

" The cost of a telephone plant can be estimated approximately on the 
basis of the number of instruments installed. An exchange of 500 tele- 
phones installed within a radius of H miles without any conduit or cable 
work, but with up-to-date pole-line construction, will cost about $65 per 
instrument; this will come so near to the actual cost that a company may 
base its calculations on it with a degree of certainty. As the number of 
telephones increases, that radius or distance from the exchange will also 
increase, and, therefore, the cost per instrument. In estimating on a 
plant of 1000 telephones some aerial cable and more substantial construc- 
tion must be taken into consideration as well asmore costly equipment; con- 
sequently, there will be a material increase in the cost per instrument; 
without conduit work a safe approximate figure would be $85 per instru- 
ment within an ordinary radius. 

"When an exchange has more than 1000 subscribers, and quick, strictly 
modern service is required, necessarily it must be equipped with central 
energy and multiple switchboards, and in towns where electric light and 
railways are used many additional appliances are required to neutralize 
the interference from the heavy circuits. Where it is necessary to con- 
struct conduits it is not safe to allow less than $100 per instrument for 
the installation. In large cities where 5000 to 10,000 subscribers are 
connected up, the cost would approximate from $150 to $200 per instrument." 

Besides the interest on the investment, maintenance and depreciation 
are of vital importance. Something has already been said with regard 
to the maintenance and depreciation of cable, but further opinion may be 
of value. In 1899 the Michigan Board of State Tax Commission arrived 
at the following schedule of depreciation for various telephone equipment. 

"Poles and cross-arms, accepting about twelve years as the average life 
of a pole, a depreciation was allowed of eight per cent per annum; under- 
ground conduits, two per cent; underground and aerial cables, lead-covered 
and rubber, ten per cent; subscriber's station equipment, ten per cent; 
switchboards, ten per cent. For copper wire in use one year or less, its 
full value will be taken; for two years and less than three years, two and 
one-half per cent; for three years and less than five years, five per cent; 
for five years and less than ten years, ten per cent; for ten years and over, 
twenty per cent. This makes an annual average of about eight per cent." 

PRIVATE EIlfES, IITERCOMMniCATEfO, AXD 

HOUSE IYSTEMI. 

(Condensed from articles by W. S. Henry in Amer. Elec, 1900). 

Thus far only the central office system has been considered. For 
Private Lines, Intercommunicating, and House Systems, very different 
apparatus and circuits are used. Such systems have been well described 
in the technical press and it therefore seems sufficient to review briefly 
a series of articles treating of such systems. m , 

Private telephone systems may be divided into series party lines, bridging 



PRIVATE LINES. 



1109 



party lines, intercommunicating systems, and small central switchboard 
systems. As the last system differs practically only in size from the regular 
central station system no description of it will be undertaken here. In 
these systems either magneto or microphone transmitters may be used, and 
the signaling apparatus may be either magneto bells and generators or the 
common vibrating bell and battery. 

Where microphone transmitters or vibrating bells are employed, the 
batteries may be distributed among the various stations or, in some cases, all 
concentrated at one place. It is generally desirable although not really 
necessary, so to arrange the circuits that the bell at the calling station, or 
the home bell as it is called, should ring when calling up another station. 
This assures the person signaling that his own circuit and probably the 




Fio. 37. Series System with Magneto Transmitters and Signaling Batteries. 

whole system is in working order, and that his call is being transmitted to 
the desired station. 

One of the simplest telephone systems comprises magneto instruments 
connected in series in one line. Fig. 37 shows an arrangement of this kind 
requiring at each station two magneto instruments; T is the transmitter 
and R is the receiver. An ordinary vibrating battery bell, V, a battery, B, 
of two or more cells, and a hook switch, H, complete the equipment. When 
the receiver, R, is hanging on the hook, the line is connected to the lower 
contact; when the receiver is removed, a spring pulls the lever up against 




Fio. 38. Series System with Magneto Transmitters and Generators. 

the contact, b. The smaller auxiliary switch, I, is arranged to normally 
rest on the contact, c. It may be pressed down upon d, but when released 
it should be returned to c by a stiff spring. 

In Fig. 38 a very similar arrangement is shown, the only difference being 
the use of magneto generators, G, in the place of the signaling batteries, 
B, of Fig. 37, and the substitution of magneto bells for the simple bells used 
in the first system. The signaling key, K, has only the upper contact, to 
normally short-circuit the generator, G, as indicated in the sketch. Some 
automatic arrangement may of course be used. 

The above described systems are known as series party lines, meaning 
that all of the stations connected up are in series with each other. When 
this arrangement is used, even for a small number of stations, the bell mag- 
nets should have as low resistance and as few turns of wire on them as 
possible, in order to reduce the impedance of the circuit; and the %*T±***A.e*~* 
should be wound with rather fine wire, because the current generatea 
■"■rassft pass through all of the bells in series. 

«= orG&T to avoid forcing the talking current through the magnets of the 
signaling bells, the latter may be "bridged" directly across the circuit, as 



1110 



TELEPHONY. 



shown in Fig. 39, in which case the bells may be wound for high resistance 
and impedance so that the talking currents will pass them. 






Fig. 39. Bridging System with Magneto Transmitters and Generators. 

In Fig. 39, three different methods of bridging are shown. At Station 1 
the bell is removed entirely from the circuit when the receiver hook is up; 
at Station 2 the bell remains constantly across the circuit in series with the 
transmitter and receiver, but when the hook is up it is short-circuited by 
the hook and its upper contact through the wire, a; at Station 3 the bell 
remains permanently connected across the circuit, and when the receiver 
hook is up the transmitter and receiver are connected in parallel with it. 




Fig. 40. Series Systems with Microphones and Batteries. 

Fig. 40 shows the simplest method of using microphone transmitters. 
The instruments are a transmitter, T; an ordinary receiver, R; a vibrating 
bell, V, and one or two separate batteries at each station. The battery, B, 
is used only for ringing the bells; the battery M.B., only for operating the 
microphone transmitters, and the battery D, for both purposes. In this 




Fig. 41. Series System with Microphones and Magnetos. 



arrangement, as well as in the one shown by Fig. 41, the microphones, 
receivers, and microphone batteries are directly m series with the line, 
no induction coils being used. ..... , 

Instead of vibrating bells and batteries for ringing, we may use a polar- 
ized bell, C, and a generator, G, as shown in Fig. 41. „_._.., .. 

A better arrangement is to use high-impedance bells bridged across the 
two-line wires, as shown in Fig. 42. The generator, as is the case in t lg. 
39, is normally on open circuit. 



PRIVATE LINES. 



1111 



Three bridging methods are shown. At Station 1 some of the current 
from the battery, M.B., can flow through the bell when the receiver is off 
the hook, but this will do no harm; in fact, it may be beneficial, for it 
allows a larger direct steady current to flow through the microphone. The 
fluctuations in the current produced by the microphone cannot pass 
through the bell-magnet coils, but will pass through the line circuit on 
account of the lower impedance of the latter. At Station 3 the bell is cut 
out when the hook switch is raised, and at Station 2 both the generator and 
bell circuits are cut off by raising the hook. An extra contact, d, is re- 
quired at these two stations, but on the other hand there are two bells 



-fi 





Fig. 42. Bridging System with Microphones and Magnetos. 

less across the circuit to form shunts or leaks for the current when two 
parties are conversing. On the whole, the arrangement at Station 3 is the 
best of the three. 

Fig. 43 represents a series party system (corresponding with that which 
was shown at Station 1 in Fig. 40) in which a battery, B, and vibrating bell, 
V, are used for signaling, and an induction coil, J, is added to the speaking 
apparatus. The primary of the induction coil is in series with the micro- 
phone transmitter, T, and its battery, M.B., and the secondary is in series 
with the telephone receiver and the line. 

The connections at Stations 1 and 2 are identical; when the receiver 
hook, H, is down the talking instruments are entirely cut out, and when it 





± 




Fig. 43. Series Party System, with Induction Coils and Signaling Batteries. 



is up the signaling key, battery, and bell are thrown out of circuit and the 
main circuit passes through only the telephone receiver and the secondary 
of the induction coil. At Station 3 the connections are different; when the 
receiver hook is down the telephone receiver and secondary of the induc- 
tion coil are merely short-circuited, while the transmitter, its battery, and 
the primary of the induction coil are open-circuited. When the hook is up, 
the talking instruments are connected up for service and the signaling part 
of the apparatus is short-circuited. Fig. 42 corresponds with Fig. 43, except 
that magneto-generators, G, and magneto-bells, C, have been substituted in 
the place of the signaling battery and vibrating bells shown in Fig. 43. The 
station connections correspond also, the receiver hook, H f at Stations 1 
and 2 being arranged to throw in and out of circuit the talking apparatus 
and the signaling apparatus, while the hook at Station 3 merely short- 
circuits the signaling apparatus or the receiver circuit, according to its 



1112 



TELEPHONY. 



position. This arrangement is the preferable one of the two, for the reason 
that faulty switch contacts at the receiver hook will not open the circuit 
so that there will always be a continuous line through which one may 
signal. 

A simple system installed where there was considerable noise, dirt, and 
vibration, is represented diagrammatically by Fig. 45. Here, there are three 
line wires, a, b, and c, the line c forming a common return for both the 




Fig. 44. Series Party System Using Induction Coils and Signaling Magnetos. 

signaling and the talking circuits, a and b, on which the apparatus is ar- 
ranged in series. In this system the talking line is never open-circuited, the 
telephone hook, H, serving to merely short-circuit the receiver and the 
secondary of the induction coil when down, and to remove the short-circuit 
and close the local circuit of the transmitter and induction coil primary 
when up. It is obvious that the middle line wire, c, gives a free path to the 
talking current, instead of its being forced through the signaling bells. Such 
an arrangement facilitates the separation of the signaling and talking ap- 
Daratus, so that the call bells can be located where they can be easily heard 
while the transmitter and receiver may be put in a sound-proof closet. The 




Fig. 45. Three-Wire Series Party System. 



disagreeable noises due to induction from lighting or power circuits may be 
overcome by using a twisted three-conductor cable between stations. Such 
an installation is greatly superior to the series system shown by Figs. 43 
and 44. 

Fig. 46 shows a series system in which one battery is used both for signal- 
ing and for talking. In this system the connections are alike at all stations; 
when the receiver hook, H, is down and the signaling key, I, is up, there are 
included in the line circuit only the vibrating bells. Depressing the signal- 
ing key, Z, puts the battery in the line and causes all the bells to ring. It is 
preferable to have the batteries so connected up that if two or more signal- 
ing keys should be depressed at once the batteries will agree in polarity. 
When the receiver hook is up the battery is connected in series with the 



PRIVATE LINES. 



1113 



transmitter and the primary of the induction coil, while the signaling key 
and bells are thrown out of circuit and the telephone receiver and secondary 
winding of the induction coil are included in the line, as shown at Station 3. 
In this, as in previous series systems, with the exception of Fig. 45, the 
talking current must flow through the signaling bells at idle stations. The 
advantage of the system is obviously that it eliminates half the batteries, 
only the one battery being used at each station for both signaling and talk- 




Fio. 46. Series Party System Using One Battery at each Station for both 
Talking and Signaling. 



ing. As in all series systems where vibrating bells are used, the vibrators 
should be short-circuited on all bells except one. 

The best method for connecting a large number of telephones on a single 
system where only two line wires may be used is to bridge them, as shown 
in Fig. 47. The dots A and A', represent the binding-posts of each complete 
outfit. The bells are permanently bridged between the two line wires at 
Stations 1, 2, and 4, irrespective of the position of the receiver hooks. The 








FlQ. 47. Bridging Party- Line System; Three Arrangements of Station 
Instruments. 



magneto-generator is also bridged across the two line wires in an independ- 
ent circuit, which is normally kept open either by a push-button, k, or 
by an automatic device on the magneto spindle. 

At Station 3 the magneto-generator is bridged permanently across the 
line as in Stations 1, 2, and 3, but the bell is connected across only when the 
receiver hook is down, being thrown out when the hook is up. At Station 5 
the bell and generator are bridged across the line wires when the receiver 
hook is down, and are cut out entirely when it is up. At all of the stations 
a third bridging circuit includes the receiver and the secondary winding 
of the induction coil in series, this circuit being open when the receiver 
hook is down and closed when it is up. The hook also closes the local 
transmitter circuit in the usual way when it is up and opens it when it is 
down. The connections shown at Stations 3 and 5 possess the advantage of 
cutting out their signaling bells entirely when the receiver hooks are up, 
instead of leaving the bells shunted across the line continuously, as is the 
case at Stations 1, 2, and 3. 



1114 



TELEPHONY. 



COI?I]?I©]¥ It FT I II. V I]VTFItCOMIfIlJ]¥ICATII¥« 

SYSTEMS. 

An intercommunicating system may be denned as a system having three 
or more telephones connected to the same system of wiring in such a manner 
that one may from any station call up and converse with any other station, 
without requiring any central-station switchboard whatever. Intercom- 
municating systems require one wire from each station to every other station 
and at least one more wire running through all the stations. Where vibrat- 
ing bells and one common ringing battery are employed, at least two more 
wires than there are stations are necessary. At each station there must be 
a switch of some kind whereby the telephone at each station may be con- 
nected to any one of the wires belonging to the other stations. Intercom- 
municating systems are very practical and satisfactory up to fifteen or even 
twenty stations ; beyond that, the large number of wires running through 
all stations makes the cost of the system increase rapidly, especially when 
the stations are some distance apart. For a large number of stations well 
scattered, a simple central-station switchboard system is preferable. 

Fig. 48 shows a very common but not a good method of interconnecting a 
number of telephones, where each station is equipped with ordinary series 
bells and magneto generators. Theoretically any number of telephones may 
be connected on such a system, but practical consideration would place the 
limit at about twenty. In this figure there are four stations ; at Nos. 1, 2, 
and 4 the telephone connections are drawn in full, while at No. 3 is shown 
the telephone outfit as it usually appears. There are four individual line 
wires, numbered 1, 2, 3, and 4, and a common return wire. Thus there is 
one more wire than there are stations, and all these wires run through all 
the stations, each wire being tapped at each station and not cut. At each 
station there is one ordinary telephone instrument consisting of the usual 
talking apparatus, magneto-generators and polarized bells. Below each 
telephone there is an intercommunicating switch, the buttons of which are 
connected to the respective line wires, and the common return wire. When 
not in use the switch at each station should remain on the home button. 




Fig. 48. Intercommunicating System, with Magneto Signaling Gener- 
ators and Polarized Bells. 



With all the levers in this position, a person at any station can call up 
any other station by moving the switch lever to the button connected with 
the individual line of the station desired, and turning the generator 
handle ; only the bells at the home station and at the station called up w r ill 
ring. The ringing and talking currents pass through only the instruments 
at the stations in communication. After finishing the conversation, the 
switch lever at the home station must be returned to its home position, 
otherwise the system will be crippled. 



INTERCOMMUNICATING SYSTEMS. 



1115 



In Fig. 49 is shown a method of wiring the intercommunicating switch 
that avoids the principal objection mentioned in connection with Fig. 46, 
that is. the failure to return the switch to the home position does not leave 
the station so that it cannot be called up. Only four stations are shown, 
but the system can be extended to include as large a number as may be 
desirable. The usual telephone sets, consisting of a microphone trans- 
mitter, induction coil, receiver, hook switch, two cells of battery, a series 
magneto-generator and polarized bell, are included in the outfits indicated 
by T lf T 2 , etc. The inside connections of these telephones are the same as 
shown in the preceding figure. 



ir»un fie/urn Wi'r*. 







iStotiont. £ tat/on 2. <$f0ti'on<9. Station*. 

Fig. 49. 

In Fig. 49 one binding-post of each telephone is connected to the common 
return wire, and the other binding-post is connected to both the lever arm, 
s, and the individual line wire belonging to that particular station. 

The home button in this last system is the first on the left and is not con- 
nected to anything ; it is really a dummy button, but it should be there by 
all means, for the lever, s, of the switch should always be returned to it 
when the original calling party leaves the telephone. If all switch arms, s, 
are on the home buttons it will be found that the circuits of all instru- 
ments are open and no bell will ring, no matter what generator is turned. 
If Station 2 desires to call Station 1 it will be necessary to first move the 
switch arm, s, at Station 2 to button 1. 

Fig. 50 is a system similar to that shown in Fig. 49, but arranged for vi- 
brating bells and one common calling battery, CB, in place of magneto* 



Common Return Wirg 



sCB 




mf- 



•4-K 



Fir 



A. 



-g- 



Fig. 50. Common Signaling-Battery System. 



1116 



TELEPHONY. 



generators and polarized bells. A battery is used at each station for oper- 
ating the transmitter. This is probably the best arrangement of batteries 
for such a system where vibrating bells are used. This system requires one 
more wire than that shown in Figs. 48 and 49 where magneto-calling ap- 
paratus is employed; thus there are two more wires throughout than there 
are stations. The calling battery, CB, must be connected to the two wires 
shown, but it may be located at any convenient place. In this arrangement 
only the bell at the station called will ring, the bell at the calling station 
remaining silent. If the bells are not arranged in this manner, the vibra- 
tors on the two bells that happens to be connected in series when making a 
call might interfere more or less with good ringing. Furthermore, it would 
not do to short-circuit any of the vibrators, because there is no telling which 
two stations may be connected together in making a call. 




ESEqTVS 

Cotnaoa Return Wirt 





Fig. 51. Common Signaling-Battery System. 

Trouble is experienced with intercommunicating systems similar to that 
of Fig. 50 by reason of the user carelessly leaving the selective switch S, off 
the home button after using the telephone. Fig. 51 shows a method of wir- 
ing such a system which obviates to a considerable extent this trouble. 
Here, the vibrating bell is permanently connected to the home button, and 
the pivot of the switch, S, is connected to the arm of the push-switch, K. 
Any station can still be called up, no matter on what button its switch, S, 
may be left. 



Ceonoa lUtara Wirt 






Fig. 52. 



The same system of wiring employed in Fig. 48 is applied to the system 
shown in Fig. 52, in which magneto-generators, G, and polarized bells, C, 
are used in place of the battery and vibrating bells. There is no need of 
having a push button or automatic shunt on the generator, although it will 
do no harm. The generator is normally on open circuit because one of its 
terminals is connected to the under contact of the push switch, K. In ordei 
to call up a station, the switch, S, is placed on the button belonging to the 
station desired, the push switch, K, depressed, and the generator handle 
turned. Since no common battery is employed for ringing, this system 
requires one less wire through all the stations than the preceding arrange- 
ment. 



INTERCOMMUNICATING SYSTEMS. 



1117 



In Fig. 53 is shown an arrangement in which one conveniently located 
common battery, C B, supplies current for ringing and also for all trans- 
mitters. No matter where the lever of the selective switch is left, the bell 
can still be rung, but conversation cannot be carried on until the switch at 
the station called is returned to the home button. This system includes a 
piece of apparatus at each station that has not been required in any of the 
systems previously described, to-wit : the impedance coil E. Where a 
common battery supplies all the local microphone circuits with current in 
systems of this kind, there is very apt to be cross talk between two pairs of 
telephones that may be in use at the same time, in which case the battery 
will be supplying current to four microphones. 



BATTERY WIRE 





^irjf^t" 




Fig. 63. Common Battery System with Impedance Coils. 



The cross talk is due to the variation in the fall of potential along the 
oattery and common return wires. 

The cross talk may be greatly reduced by using batteries of very low in- 
ternal resistance, such as storage cells, and making the common return 
and battery wires extra large, that is, small in resistance, so that the vari- 
able fall of potential through the battery and in these two wires may be 
small. However, it is impractical to make the resistance of these two 
wires low enough, especially where they are of considerable length, to 
eliminate all cross talk. 

Another way to reduce the trouble from cross talk is to insert an impe- 
dance coil in each microphone circuit, as shown in Fig. fi3. This makes 
the impedance of each microphone circuit large compared to that of the 
two lines and battery, and in order to get the same current as before in 
each microphone the e. m. f . of the battery must be increased. These im- 
pedance coils reduce the efficiency of the system, but the reduction in 
cross talk compensates for this loss to a great extent. 



T 




T^ 




C«ll Wire No. i 






J 



Fig. 54. Radial System ; Selective at One Station Only. 



1118 



TELEPHONY. 



It sometimes occurs that a system is required to be so arranged that one 
station can call up any one of the others, but the others can call up and 
converse with the iirst station only. Fig. 54 is a diagram of such a system; 
Station No. 1 or No. 2 can call up station C by merely depressing the push 
switch Kl or K2, but they cannot call up or converse with each other. 
Station C by means of the switch, S, and push, K, can call up either 
Station No. 1 or No. 2. There are only two wires that must run through all 
the stations. There is one wire, however, from Station C to each one of 
the other stations. These wires, Call Wire No 1 and Call Wire No. 2, are 
used only when .Station C calls up one of the other stations. One wire 
could be made to answer if there was no objection to having all but the 
home bell ring when Station C makes a call. In this case a certain num- 
ber of rings would be necessary for each station except C, and the one 
common call wire would be connected to the signaling key at a, Station C, 
and there would be no need of the switch, S. 

As arranged in the diagram, the push switch, K, is normally open. When 
Station C desires to call Station No. 2, for instance, the switch, S, must be 
turned to button 2 and the push switch, K, depressed. The one common 
battery, B, furnishes current for all ringing and talking. At each station 
there is an ordinary receiver, microphone transmitter, and vibrating bell. 
There is only one bell in circuit when a call is made so that each bell must 
have a vibrator. It makes no difference upon what button the switch, S, 
is left. 

In the systems so far described there is nothing to prevent the intercom- 
municating switch from being left off the home button when the conversa- 
tion is finished and the receivers hung up. 




Fig. 55. Ness Automatic Switch. 



An example of a device obviating this trouble is the Ness automatic 
switch, illustrated by Fig. 55, arranged so that the replacing of the re- 
ceiver upon the hook causes the switch to fly back to its home position. 
In the engraving S is the lever of the selective switch, adapted to be ro- 
tated over the various contact buttons, 1, 2,3, etc. It is mounted upon a 
shaft, A, passing through the front board of the box and carrying a ratchet- 
wheel, E, inside the box. This ratchet-wheel is held in any position to 
which it may be rotated by a pawl, F, and thus prevents the lever S, from 
turning backward. Upon the short arm of the hook lever, H, is pivoted a 
dog, G, adapted, when the receiver is removed from the hook, to engage a 
notch in the pawl, F; when the receiver is replaced, the dog, G, is pulled 
upwards and lifts the pawl out of the engagement with the ratchet-wheel, 
allowing a spiral spring around the shaft, A, to return the switch lever, S, to 
the home button. After raising the pawl out of the notch on the ratchet- 
wheel the dog slips out of the notch on the pawl, thus allowing the latter to 
return into contact with the ratchet-wheel in order to be ready for the next 
use of the telephone. In order, however, that the pawl may not engage the 
ratchet-wheel before the lever, S, has fully returned to its normal position, 



INTERCOMMUNICATING SYSTEMS. 



1119 



a second dog, J, is provided which is pressed by a spring so as to occupy a 
position under the pin,p, carried on the pawl, F, thus holding it out of 
engagement with the ratchet-wheel until the rotation of the lever is com- 
pleted. At this point a pin on the farther side of the ratchet-wheel pushes 
the dog, J, out of engagement with the pin,^?, and allows, the pawl, F, to 
drop into contact with the ratchet-wheel. 




Fig. 56. Common Signaling Battery System ; Individual Talking 
Batteries. 

In Fig. 56 are shown the circuits of a four-station system using one com- 
mon battery, CB, for ringing up the various stations, each station having 
an ordinary vibrating bell, C. The circuits of Stations 1 and 4 are shown in 
full, while those of the intermediate stations, being exactly the same, are 
partially omitted. It will be noticed that the switch lever, S, at each 
station is connected with the line wire bearing the same number as that 
station, by means of the wire, d. Each line wire is also connected at each 
of the stations not bearing its own number with a button on the switch of 




Fig. 57. System having Common Talking and Signaling Battery. 



1120 TELEPHONY. 



that station which does bear the same number in the manner pre- 
viously described, by means of the wire, e. In this common-battery call 
system two additional wires are run, one being termed the " call wire " and 
the other the " common talking wire." The call wire and the talking wire 
are connected through the calling battery CB, as shown. It is evident that 
the number of wires passing through all the stations will be two more than 
the number of stations, irrespective of that number. 

If Station 4 desires to call up Station 1, for example, No. 4 will turn his 
switch lever until it rests upon button 1, then a slight pressure upon the 
switch knob causes the switch lever, S, to touch the contact strip, I), com- 
pleting a circuit from the battery, CB, to contact strip, T>, lever, S, and 
button, 1, at Station 4; line wire, 1, wire, d, switch, H, and bell, C, at 
Station 1, and back to the battery through the common talking wire. 
When both subscribers remove their receivers from the hooks, the circuits 
are completed over line wire 1 with the common talking wire as a return. 
At the close of the conversation the receiver is simply hung upon the hook, 
and the automatic mechanical device returns the lever to the home po- 
sition. 

Fig. 57 shows the application of the Ness automatic switch to an inter- 
communicating system, using one common and centrally located battery for 
supplying both the ringing and talking current. The section, TB, of the 
battery supplies all the microphone transmitter circuits, and the whole 
battery, KB, supplies the current for ringing the ordinary vibrating bells 
that are used in this system. In this arrangement it is evident that the 
number of wires passing through all the stations will in any size of system 
be three in excess of the number of stations. 

TWO- WIRE IHrTEItCOlfllflUTflCATI^O TEIEPHOIE 

SYSTEMS. 

By H. S. Webb. 

\*y a two-wire intercommunicating telephone system is meant one that 
has two wires for each telephone station in addition to the two wires used in 
common by all the stations in some systems for signaling purposes only. 
The object of using two independent wires for each telephone station is to 
eliminate cross-talk. 

In a single wire system if one wire in use by one pair of telephones over- 
laps the wire in use by another pair of telephones, there is very apt to be 
more Dr less cross-talk. 

Thiy can be avoided by using for each conversation two independent 
wires; that is, by using what is here termed a two-wire system. If the 
wires for an intercommunicating system are run in cables, each pair must 
be twisted together, as in telephone cables used in complete metallic ex- 
change systems. If not in cable then the different pairs must be fairly well 
separated, and if two pairs run parallel to each other for any distance the 
wires should be properly transposed in order to eliminate cross-talk. 

A two-wire system is shown diagrammatically in Fig. 58. A contact 
piece, e, is fastened to, but insulated from, the hook switch, in such a man- 
ner as to close th.3 circuit between d and / when the telephone receiver rests 
on the hook. A double switch, S, is also required. The latter maybe made 
in a variety of ways, but is here shown in a simple form in order that the 
connections may be clearly seen. The two levers to, and n, are mechanically 
fastened together so that moving one handle will move both levers ; but 
the two levers must be insulated from each other; P is a simple push- 
button switch. One common and centrally located battery, RB, is used 
for ringing the bell at any station. 

To call up a station the switch, S, is turned until the straps, to and n, rest 
on the buttons of the number of the station desired and the push-button 
pressed. It makes no difference whether the receiver at the station where 
the call originates is on or off the hook, nor is it necessary for the switch at 
the station called to be at the first, or home, position. However, the levers, 
to and n, at the station called, must rest on their home positions before any 
conversation can be carried on. When ringing, only one wire of a pair is 
used, the wire, F, serving as a common return; but when conversing, both 
wires of one pair are in use, and neither wire, W ', nor V, is used; thus there 



INTERCOMMUNICATING SYSTEMS. 



121 



can be no cross-talk due to induction. The ringing current may cause 
slight trouble from induction, as it traverses but one wire of a pair. By 
means of a double contact push-button switch even the ringing current can 
be made to flow through both wires of one pair and all danger of induction 
troubles be eliminated. 




PairS 



Fig. 58. Two-wire Telephone System. 



Such an arrangement is shown in Fig. 59. The wiring at Station 1 is so 
arranged that the station can be called up from any station, no matter in 
what position the intercommunicating switch Si may have been left. 




Fig. 59. Two-wire System with Automatic Switch. 

However, the wiring at this station has been purposely so arranged that 
the switch must be returned to the home position before anything can be 
heard in the receiver. 



1122 



TELEPHONY. 



When automatic switches are used the switch is automatically restored 
to the home position when the receiver is hung up. At Station 2 in Fig. 59 
the connections are also suitable for use with an automatic switch. 

If magneto bells and generators are included in each telephone set instead 
of an ordinary vibrating bell, then the ringing battery and the two battery 
wires will not be required, and the connections would be as shown in Fig. 




3=*4 



P4 



Pair 2 



^ Pair 3 
Fig. 60. 



Automatic Telephone System with Magneto Bells. 



60. This arrangement requires only one pair of wires for each telephone. 
At Station 1 the wiring is so arranged that only a simple push-button, P, 
is required for ringing purposes, while the wiring at Station 2 requires a 
double contact push, P K The wiring at this latter station may give a ' 
more evenly balanced system, but does not seem to possess much superiority 
over that at Station 1, which is the simpler. At Station 2 an insulated 
contact piece on the under side of the hook switch is required. 



USES OF ELECTRICITY IN THE UNITED 
STATES ARMY. 

Revised by Graham H. Powell. 

The use of electricity is prevalent in nearly every branch of the military 
art, being employed in the operation of searchlights, manipulation of coast 
defense guns, ammunition hoists; in range and position finders; for field 
and fortress telephones and telegraphs ; for firing guns, submarine and sub- 
terranean mines, and the control of dirigible torpedoes; while electrically 
operated chronographs are utilized in the solution of ballistic problems. 

In March, 1906, the President submitted to Congress the report of the 
National Coast Defense Board, appointed in the previous year "to recom- 
mend the armament, fixed and floating, mobile torpedoes, submarine mines, 
and all other appliances that may be necessary to complete the harbor de- 
fense" of the United States and its insular possessions. That board made 
the statement in its report that " Electricity has become of vital importance 
to an efficient system of gun defense." 

The following were the general recommendations of that board so far as 
electrical appliances are concerned: 

1. That the electrical power for fortification and defense purposes be fur- 
nished by an adequate steam-driven, direct-current producing central power 
plant, all machinery to conform in type to approved commercial standards. 

2. That each battery or group of batteries, depending upon local con- 
ditions, be equipped with direct- current generators, gas or oil engine driven, 
installed as a reserve to the central plant. 

3. That searchlights, except such as are in close proximity to the central 
plant, be provided with and operated by self-contained units. 

4. That the torpedo casemates be equipped as heretofore with independent 
power for submarine-mine purposes, as an integral part of the submarine- 
mine defense. 

5. That when alternating currents are essential, they should be obtained, 
if practicable, from direct current by means of a suitable converter; or, if 
more economical, by a separate alternating unit. 

6. That the current from the fortification central plants, when not needed 
for fortification service, may be used for garrison purposes when such distri- 
bution does not require too large an increase in the size and number of units. 

7. That if garrison service requires alternating current, this should be 
supplied by the central plant, either through a suitable converter or from 
alternating current units specially installed for the purpose in the central 
station; such increase, however, and all additional cost due to post lighting 
being a charge against the proper appropriation. 

8. That uniformity of types and accessories is desirable. 

9. That all electrical power plants for the use of fortifications shall be 
operated by the Artillery. 

SEARCHLIGHTS. 

Searchlights are used both as offensive and defensive auxiliaries; defen- 
sive when used by shore fortifications to light channels or by a vessel to 
discover the approach of torpedo boats; offensive when used as " blinding- 
lights" to smother the light of an approaching vessel and confuse her pilot. 

The accompanying illustrations show the searchlight manufactured by 
Schuckert & Co. of Nurnberg, Germany. 

The lamp is placed on top of the two lowest longitudinal rods of the cas- 
ing, and is held in place by four lugs, two on each side. The carbon holders 
reach upward through a slit in the casing, and there is a small wheel in rear 
for moving the light parallel to the axis of the reflector for the purpose of 
focusing it. The trunnions of the casing are fastened to two longitudinal 
rods on each side, parallel to the axis of the cylinder, and can be moved for- 
ward or back so that the casing and what is carried with it will have no pre- 

1123 



1124 USES OF ELECTRICITY IN UNITED STATES ARMY. 




Fig. 1. Schuckert Searchlight. 



SEABCHLIGHTS. 1125 

ponderance. The trunnions are supported in trunnion beds in the ends of 
supports which project upwards from the racer. 

The elevating arc is attached to another longitudinal rod beneath the 
cylindrical casing and is capable of adjustment on this rod. Engaging in 
this arc is a small gear attached to a horizontal shaft passing through the 
right trunnion support and carrying a small hand wheel. This small hand 
wheel is for the purpose of elevating or depressing the light rapidly. 

The light may be elevated or depressed slowly by means of a small hand 
wheel attached to another horizontal shaft in front of theonejust described. 
This shaft near its center carries a worm, engaging in a worm wheel on a 
vertical shaft, to which is also attached a bevel gear. This gear engages in 
another, which is attached to the quick-motion shaft, but is free to turn 
about it until it is connected with the elevating gear wheel by means of a 
friction clamp. The relation between the worm and worm wheel is such 
that a slow motion is obtained. 

The racer rests upon live rollers and is joined by a pintle to the base ring. 

Attached to the base ring is a toothed circular rack, into which on the 
outside a gear wheel attached to a vertical shaft engages. This vertical 
shaft projects upward through the racer and carries a worm wheel, which 
engages in a worm carried on a horizontal shaft having a hand wheel. The 
worm wheel is entirely independent of its vertical shaft, except when con- 
nected with it by means of a friction clamp. When so connected, by turn- 
ing the hand wheel the light is traversed by a slow motion. To traverse 
the light rapidly, the friction clamp is released and the light turned by 
hand, taking hold of the trunnion supports. One of the ends of the slow 
motion elevating and traversing shafts is connected with a small electric- 
motor, which is encased in a box on top of the racer. By means of these 
motors the motion of the searchlight can be controlled from a distant point. 
A switch is provided with contacts so arranged that the current can be 
passed into the armatures of the motors in either direction, so as to obtain 
any movement the operator may desire. The current needed for the move- 
ment is obtained from the lines supplying the current used in the light 
itself. The current is brought to the motors by means of contact points, 
bearing on circular contact pieces attached to the racer. 

The reflector is a parabolic mirror embedded in asbestos in a cast-iron 
frame, and is held in place by a number of brass springs. The frame of the 
reflector is fastened to the overhanging rear ring of the casing with studs 
and nuts, the overhanging part of the ring protecting the reflector from 
moisture. In order to enable the operator to observe the position of the 
carbons and the form of the crater while the apparatus is in use, small 
optical projectors are arranged at the side and on top of the casing, which 
enables images of the arc as seen from above and from the side to be 
observed. When the light is properly focused the positive carbon reaches 
a line on the glass on top of the casing. 

There are two screws on the positive carbon holder which enable the end 
of this carbon to be moved vertically or horizontally to bring it to a proper 
adjustment. 

In consequence of the ascending heat the carbons have a tendency to be 
consumed on top ; and to avoid this there is placed just back of the arc and 
concentric with the positive carbon a centering segment of iron, attached to 
the casing, which, becoming magnetic, so attracts the current as to equalize 
the upward burning of the carbons. In taking the light out of the casing 
this centering segment must be unfastened, and swung to the side on its 
hinge. 

An example of the method of calculating the intensity of the lignt sent out 
by the mirror follows : 

Diameter of parabolic mirror, 59.05 inches. 

Diameter of positive carbon, 1.5 inches. 

Diameter of negative carbon, 1 inch. 

Power consumed, 150 amperes X 59 volts. 

Maximum intensity of rays impinging upon the mirror, 57,000 candle- 
power. 

Average intensity of rays impinging upon mirror, 45,600 candle-power. 

Diameter of crater, 0.905 inch. 

Intensifying power of the mirror — = .. ' . =4,253. 

a 1 (0.y05.r 



1126 USES OF ELECTRICITY IN UNITED STATES ARMY. 




s=s 



GENERATOR 
SAFETY FUSE 

Fig. 2. Diagram showing Searchlight Connections. 



DATA RELATIVE TO SEARCHLIGHTS. 



1127 



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1128 USES OF ELECTRICITY IN UNITED STATES ARMY. 



Total intensity of light- sent out by mirror, 45,600 X4,253 = 194,000,000 

candle-power. 

The focal distance of the mirror is 25.5 
inches. 

The dispersion angle of the concen- 
trated beam is 2° 2'. 

The diameter of the illuminated area 
at a distance of 1,111 yards is 84 yards. 

The resistance Rm on the switchboard 
at the light is in series with the main 
current for the purpose of regulating 
the amperage at the lamp. The volt- 
meter at the lamp should indicate about 
60 volts. The connection of the dis- 
tance governor with the two motors for 
elevating and traversing is also shown. 

Until recently the largest searchlight 
built was the one that was on exhibition 
at the Paris Exposition of 1900 in the 
section "Navigation de Commerce et 
Armees de Terre et de Mer," which was 
6 feet 6 inches in diameter, and gives a 
beam of 316,000,000 candles. This was 
slightly exceeded by the 80-inch projec- 
tor of the General Electric Co. at the 
Louisiana Purchase Exposition. 

The table on preceding page gives 
data in regard to searchlights of various 
sizes. 

curo\oc;raph§. 

In the experimental work of testing 
guns, etc., it becomes necessary to ascer- 
tain the velocity of projectiles, both 
while passing through the bore of the 
gun and during flight. Chronographs of 
various sorts are used for this purpose. 

In order to ascertain the velocity of a 
projectile during flight, two screens or 
targets are set up in the course of the 
projectile, generally 100 feet apart. 
These screens ordinarily consist of a 
frame of wood carrying a number of 
small parallel copper wires. The break- 
ing of the wires in the successive frames 
by the projectile causes the interruption 
of the current through the instrument, 
and thus registers the time of flight 
between the screens. 

Probably the best-known instrument 
of this class is the one invented by Cap- 
tain Le Boulenge' of the Belgian artil- 
lery, which was afterwards modified by 
Captain Breger. 

Bouleng-e Chronograph. 

This instrument depends for its accu- 
racy upon the law of falling bodies Or the 
acceleration due to gravity, namely, 32 
feet per second. 

It consists of a vertical column (Fig. 3) 
to which are affixed two electromagnets; 
Fig. 3. the right-hand one, A , is actuated by the 

current of the first frame and supports an armature C lt called the chrono- 
meter; the left-hand magnet, B, is actuated by the current of the second 
frame, and supports an armature D, called the registrar. 




CHRONOGRAPHS. 



1129 



The chronometer C is a long, cylindrical brass tube terminating at its 
upper extremity in a piece of soft iron, and bearing at its lower extremity a 
steel bob. It is surrounded by a zinc or copper cylinder called the recorder. 
The rupture of the first target causes the demagnetization of the magnet A , 
releasing the rod C. The registrar D is of the same weight as the chronome- 
ter, and is a tube with soft iron and bob. The cores of the electromagnets 
and the soft iron of the armatures terminate in cones slightly rounded at 
their vertices in order that the armatures when suspended can take a verti- 
cal position. 

When the registrar is set free by the rupture of the second target it 
strikes a horizontal plate (a), which turns upon its axis (c) and releases the 
spring (d). The spring is furnished with a square knife (e), which strikes 
the recorder and leaves an indentation upon it. 

If the two currents be ruptured simultaneously the indentation is found 
upon the recorder at a height h, indicating that_since the chronometer 

commenced to fall the time t has elapsed, t = i/— . 

It is evident that t is the time required for the apparatus to operate; it 
is a systematic retardation inherent in the instrument. 

A special device, called the disjunctor, permits the simultaneous rupture 
of the circuits to be produced, so that the time t is always known. 

A very simple device is resorted to in order to render it constant. If the 
current of the registrar is not ruptured until after that of the chronometer, 
and if an interval T has elapsed between these ruptures, the time during 
which the chronometer will fall before receiving the indentation of the 
knife will simply be augmented by t, and calling H the height of the inden- 
tation, we will have i—-= 
t + T= 4/—. 

Thus the determination of an interval T always comprises two opera- 
tions: the measurement of the time (t) required for the instrument to 
operate, and that of the time t -f- T. The difference of these two measure- 
ments gives the time sought. This indirect method of ascertaining the 
result is the characteristic feature of the instrument and explains its accu- 
racy. When the rupture of the currents is produced by the projectile the 
portion (D) of the trajectory between the targets is regarded as rectilinear 
and the mean velocity V is D 

V 



v/f<*-») 



With the time known that the projectile takes to pass between the two 
screens, the velocity in feet per second, the usual mode of indicating, is 
readily obtained. 

The arrangement of the circuit must vary according to circumstances, 
and no particular system can be prescribed. The general arrangement, 
however, is shown in the sketch, 




Fig. 4. Connections of Boulenge* Chronograph. 



1130 USES OF ELECTRICITY IN UNITED STATES ARMY. 



Schultz Chronoscope. 

The Boulenge* chronograph measures velocity at one point only, but it is 
frequently necessary to measure the velocity of the same projectile at 
different points, as in determining the laws of the resistance of the air to its 
motion, or in ascertaining the velocity of a projectile at different points in 
the bore of the gun. 




Fig. 5. Schultz Chronoscope. 

For such purposes an instrument must be used which will give a scale of 
time of such length that all the phenomena may be registered upon it. 

There are several instruments of this class, of which the best known is the 
Schultz chronoscope. In this instrument a drum (a), one meter in circum- 
ference, and covered with a coating of lamp-black, is driven by the means 
of a clock movement and weight, so as to revolve once per second and 
at the same time slowly advance longitudinally. In front of the drum, 
mounted on a support and actuated by two magnets, is a standard tuning- 
fork (c), vibrating 250 times a second; on one link of this fork is a quill (b) 
which traces a line on the blackened surface of the drum, and therefore 
will record 250 complete vibrations for every revolution of the drum. 

A microscope with micrometer (not shown in drawing) is also attached to 
the support fork; and each vibration of the fork, traced on the drum in form 
of a curve, can be subdivided in 1000 parts, thus allowing readings to be 
made to tsootsv of one second. On the support with the tuning-fork is a 
small pointer which traces a straight line on the drum. This pointer has an 
electrical connection with an accurate chronometer which at every half 
second closes the circuit and causes the pointer to make a succession of 
records on the revolving drum. These marks serve as starting-points to 
count the number of vibrations of the tuning-fork, and to check them up 
every half-second. 

In order to measure the velocity of projectiles, the gun must be fitted 
along its bore with special electrical circuit breakers, usually placed one 
foot apart. Each circuit breaker is so constructed that the current is 
interrupted as the projectile passes, but is made again before the projectile 
reaches the next breaker one foot further on. 

These breakers, with appropriate battery, are all in one circuit with the 
primary of an induction coil. One terminal of the secondary of the coil is 
grounded to the frame of the chronoscope, while the other terminal con- 
sists of a fine point near the blackened surface of the drum. Therefore, 



CHRONOGRAPHS. 



1131 



when the primary circuit is opened by the first circuit breaker along the 
bore of the gun, the spark induced in the secondary of the induction coil 
jumps from the points to the revolving drum, leaving a distinct mark on 
the blackened surface. As the next circuit breaker in the gun is passed 
the spark again passes to the drum, and this operation is repeated for every 
breaker along the gun bore. Thus on the drum, alongside of the indications 
made by the tuning-fork, will be recorded a succession of spots at certain 
distances from each other. The time elapsing between any two of these 
spots can be calculated directly from the record which the tuning-fork 
made, and thus the time (measured to the g^oou P art °^ a sec o n d) taken by 
the projectile in passing a known distance along the gun barrel calculated. 
— Electrical World and Engineer, June 23, 1900. 

Schmidt Chronograph. 

This is a portable instrument, and while probably not so accurate as the 
Boulenge instrument, is sufficiently so for the every-day work of the proving 
ground. 

The chronograph is composed of the following principal parts (see Figs. 
6 and 7): 




Fig. 6. Connections of Schmidt Chronograph. 

The balance-wheel A , with its spring and needle. 

The electromagnet B, which holds the balance-wheel at the starting- 
position and releases it the instant the first current is broken. 

The electromagnet C, with its mechanism, which stops the balance-wheel 
the instant the second current is broken. 

The dial D, graduated for velocity readings. 

A circular frame E, for setting the instrument at zero. 

The button F, reestablishing the current in the magnet C. 

The rheostats G and G', with their resistance coils for regulating the 
currents. 

The balance-wheel, made of nonmagnetic metal, is about 2\ inches in 
diameter and mounted on the axis o, which is held by two strongly made 
bridges fastened to the face plate of the instrument. The pivots of the 
axis are set in jeweled bearings. The spiral spring H is fastened to the 
bridge and axis as in ordinary chronometers. 

The needle / is composed of two parts, as shown in Fig. 8. One part, a, of 
bronze, is fastened rigidly to the axis; the other, b, a steel spring, is fas- 
tened at one end to a, the free end being limited in its motion by two small 
pins set into a. 



1132 



USES OF ELECTRICITY IN UNITED STATES ARMY. 



The electromagnet B, which holds the balance-wheel at the starting- 
point, is operated by the current passing through the first screen, and is 
mounted on the face plate so that the core is radial with reference to the 
balance-wheel. The core of the magnet projects beyond the coil and acts 
upon the small armature c, mounted on the rim of the balance-wheel. 

The electromagnet C, with its mechanism operated by the current pass- 
ing through the second screen, stops the balance-wheel the instant the 




Fiq. 7. Interior Schmidt Chronograph. 

4urrent is broken. This magnet is somewhat larger than the other, and is 
placed tangentially with reference to the balance-wheel. It acts upon the 
two armatures d, d', placed opposite the extremities of the core. These 
armatures are fastened to the ends of the two levers K, K', which are 




Fig. 8. Construction of Needle. 

mounted on the axis e, e', parallel to the axis of the balance-wheel and 
similarly supported. The other ends of the levers are joined by the coiled 
spring L, with its adjusting-screw. Set in the levers near this end are four 
pins, /, f, /', f , that ordinarily, due to the tension of the spring, bear against 
the rim of the balance-wheel, holding it fast. When the current 



CHRONOGRAPHS. 1133 

through this magnet, the armatures on the levers are attracted by the 
core, the spring is elongated, and the pressure of the pins upon the balance- 
wheel is released. When the current is broken the armatures are released, 
and the tension of the spring closes the pins upon the wheel. To insure 
effective action the pins are accurately set and the rim of the wheel is 
milled. 

The face of the chronograph is a graduated dial concentric with the 
balance-wheel axis. When the wheel is held at its starting-point the needle 
points at the zero of the graduation. The scale in black indicates the time 
in thousandths and two-ten-thousandths of a second. Another scale, in red, 
gives the velocity directly in meters per second when the screens are placed 
50 meters apart. 

The dial is covered with glass enclosed in the circular metal frame E. 
A pin g, fixed in the glass, is used to set the needle at zero by turning the 
frame, to which is also fastened the lens h, to facilitate reading. This lens 
is provided with two pointers so placed that the reading is always taken in 
the vertical plane. 

The button F is for the purpose of reestablishing the current through 
the magnet C after it has once been broken. Pressing the button closes 
the circuit; the magnet then attracts the armatures d, d', fixed to the ends 
of the levers K, K'. This motion of the levers brings the small spring I, 
mounted on K f , in contact with the projection k, thus forming a circuit, 
through which the current continues to flow after the pressure on F has 
been released. This contact is broken by the motion of the lever when the 
current is interrupted by the shot. This arrangement prevents the current 
from passing through the magnet and releasing the balance-wheel before 
the circuit is closed by pressing the button F, even though the broken screen 
is repaired, and gives the operator time to take the reading and prepare for 
the next shot. This is especially important when targets that close the 
circuit automatically are used. 

The rheostats for regulating the currents are placed above the dial, their 
resistance coils being inside the case. One binding-post of each rheostat is 
provided with a circuit closer for passing the currents through the resist- 
ance coils or directly into the rheostats. 

The Squire-Crehore Photo-dironograpli. 

This instrument was designed to overcome the minute errors inherent in 
other forms of chronographs, such as the inertia of the armature, the time 
required to magnetize iron, or in instruments employing a sparking de- 
vice, the fact that successive sparks do not proceed from the same point by 
identically the same path. 

The agents employed in this instrument are light and electricity. Briefly 
stated, a ray of light from an electric arc is reflected upon a revolving 
photographic plate. The interposition of the shadow of a tuning-fork 
gives on the plate a curve which is used as a scale of time. 

In the path of the beam of white light is placed a Nicol prism in order to 
obtain a beam of plane polarized light. This prism is made of two crystals 
of Iceland spar, which are cemented together by Canada balsam in such a 
way as to obtain only a single beam of polarized light. The crystal is a 
doubly refracting medium; that is, a light beam entering it is in general 
divided into two separate beams which are polarized and have different 
directions. One of these beams in the Nicol prism is disposed of by total 
reflection from the surface where the Canada balsam is located, and the 
other emerges a completely polarized beam ready for use. 

A second Nicol prism exactly like the first is now placed in the path of 
the polarized beam. This second prism is called the "analyzer," and is 
set so that its plane is just perpendicular to that of the first prism, called 
the "polarizer," so that all the light vibrations not sorted out by the one 
prism will be by the second. In this position, the planes being just perpen- 
dicular to each other, the prisms are said to be "crossed," and an observer 
looking through the analyzer finds the light totally extinguished as though 
a shutter interrupted the beam. 

By turning the analyzer ever so little from the crossed position, light 
passes through it, and its intensity increases until the planes of the prisms 
are parallel, when it again diminishes ; and if one of the prisms is rotated 
there will be darkness twice every revolution. In order to accomplish this 



1134 USES OF ELECTRICITY IN UNITED STATES ARMY. 

same end without actually rotating the analyzer, a transparent medium 
which can rotate the plane of polarization of the light subject to the con- 
trol of an electric current is placed between the two prisms. The medium 
used is carbon bisulphide, contained in a glass tube. To produce a mag- 
netic field in the carbon bisulphide, a coil of wire through which passes an 
electric current, is wound around the glass tube. When the current ceases 
the carbon bisulphide instantly loses its rotatory power, and the ray of 
light is free to pass through the prisms. 

Breaks in the current are made in the same way as in other ballistic 
chronographs. This instrument is not now in use, but the foregoing 
description is given as showing the development of such devices. For a 
complete description of this instrument, with an account of experiments, 
see The Polarizing Photo-Chronograph, John Wiley & Sons, New York. 

IttAMMHLAMOltf OF COAST-DEfEUSE CJUM8. 

Until recently the carriages for the larger caliber of guns were manipu- 
lated only by hand-power, but tests having demonstrated the utility of 
electric power for this purpose, such carriages are now equipped with 
motors for the purpose. 

In disappearing carriages of the type in use in the United States, the 
operations to be performed are those of elevating and depressing, traversing, 
and the retraction of the gun from the "in batterv" position to that assumed 
after firing. This recoil position is normally obtained by the discharge of 
the gun operating through recoil cylinders and a counterweight, the latter 
being principally for returning the gun to the firing position. However, 
it is frequently desirable, or necessary, to retract the gun without firing the 
piece, and for this purpose wire ropes are attached to hooks on the gun 
levers near the trunnions of the gun, the opposite ends winding on drums. 

The electrical equipment consists of the following apparatus: 

Traversing: motor. — A 4 horse-power, totally enclosed motor, 110 
volts, and having a speed of about 565 revolutions per minute. This 
motor has a pinion upon its shaft which engages directly with a gear upon 
the traversing crank shaft. 

Elevatingr-Depressing* and Retraction motor. — A single 
motor is used for all of these operations. It is rated at 4 horse-power, 
110 volts, and speed of 625 r.p.m. 

A lever carries an idler gear so that the motor shaft may be thrown into mesh 
with either the gear on the retracting or that on the elevating crank shaft. 

Both traversing and elevating motors are shunt wound, the fields being 
energized directly from the switchboard and the armatures being operated 
by individual controllers. 

The two controllers, one for the traversing and one for the elevating- 
retracting motor, are placed side by side on a frame bolted to the working 
platform in rear of the left standard of the carriage. Each controller shaft 
has a vertical extension reaching to a convenient height above the sighting 
platform from which the controllers may be operated if desired, though 
only one set of handles is provided, to avoid the possibility of attempts to 
maneuver the carriage from two different points. 

In the side and rear elevations (Figs. 9 and 9a) A is the elevating and 
depressing hand-wheel, B the retracting hand-wheel, with lever C carrying 
idler gear between them; D is the traversing crank shaft, E controllers, 
F controller extension shafts, G sighting platform, and H wire rope for 
retracting. 

The motors heretofore described are bolted to a bed plate inside the 
chassis and immediately in rear of the hand wheels. 

ELECTRIC FFIES. 

It is often necessary to fire at a distance from the gun, as in experiments, 
and for this purpose the electric fuse offers the safest, simplest, cheapest and 
most effective means of firing high explosives or large charges of powder, and 
the only means of igniting separate charges simultaneously for greater 
destructiveness, or a single charge from a distant point, or at a required 
moment, or under water. 



MANIPULATION OF COAST-DEFENSE GUNS. 



1135 




L_J 



The electric fuse consists of about J-inch length of f^^^P^X; 



1136 USES OF ELECTRICITY IN UNITED STATES ARMY. 




Fig. 9a. Rear. 



for detonating high explosives. The whole is fixed within a copper case. 
An electric current of specified strength reddens the bridge, ignites the 
gun cotton, and fires the fuse. 

The commercial fuse (Fig. 10) has a copper shell A with corrugation to 
hold more firmly the sulphur cement F which seals up the open end and 




FW. 10. 



holds firmly in place the fuse wires. B is the chamber containing 20 to 50 
grains of fulminate. A little gun cotton surrounds the bridge which is 
soldered to the bared ends of the fuse wires D. The wires, 4 to 40 feet long, 
have cotton covers soaked in asphalt for ordinary outdoor, work and gutta- 
percha covering for submarine work. 



DEFENSIVE MINES. 



1137 



The United States Navy electric fuse (Fig. 11) has the copper case in 
two parts which screw together, T 3 S inch. The up 
35 grains of the fulminate. The lower, open at 



upper or inside part holds 
both ends, is filled with 




Fig. 11. A, lower tube; B, upper tube; C, plug of sulphur and glass; 
D, bridge legs; E, bridge; F, gun cotton; (?, fulminate; //.fuse wires. 



6ulphur and glass, which holds fixed in place the wire ends and bridge. 
When the fulminate is dry, the spaces in both parts are filled with dry pul- 
verulent gun cotton and the parts are screwed together. 



A mine is a charge of explosive contained in a case which is moored be- 
neath the surface of the water or buried beneath the soil. The mines laid 
and operated in and around seacoast fortifications are for the most part 
defensive in their character, fixed in position, and hidden. 

A defensive mine is either self-acting, — a mine which, once placed, ceases 
to be under control, and is tired by means within itself, mechanical or elec- 
trical,— or controlled, a mine fitted with electrical apparatus, which ena- 
bles a distant operator to ascertain its condition, and to fire it at any time ; 
it may also be fired automatically. 

A controlled mine may be fired in four different ways : (a) by contact with 
the mine only ; (6) at will of the operator only ; (c) by contact and will, both 
of which are necessary ; (d) by observation from two stations. 

A controlled sea mine may be either a buoyant mine whose case floats 3 
or 4 feet beneath the surface, and contains both the charge and electrical 
apparatus, or a ground mine. The latter is in two parts: one a case contain- 
ing the charge and fuse, rests on the bottom ; the other, containing the elec- 
trical apparatus, floats 3 or 4 feet beneath the surface. 

Copper wires lead to two or three Sampson-Leclanche cells, which are 
put in circuit with the torpedo casemates of the fortification. 



*_\U.Hv..\\J/,^/^ 



^Jlk <L^MuM^k^dij^ 



SPRING BOARD 




LE CLANCHE 



Fig. 12. Electrical Land Mine. 



The sketch shows a self-acting electrical land mine, and is self-explana- 
tory. By using -three lead wires the mine may be fired by the enemy's con* 
tact with it, or by the operator at the station. 



1138 USES OF ELECTRICITY IN UNITED STATES ARMY. 



CIRCUIT CLOSER 
IN TORPEDO 




OPERATING BOX ON SHORE 

Fig. 13. Diagram of torpedo circuit closer and connections. 



DEFENSIVE MINES. 1139 

Circuit Closer in Torpedo. (See Fig. 13.) 

NS, circular permanent magnet with attached electromagnets N and S. 

A, armature whose adjusting spring near K holds it away from the mag- 
net, while a weak current flows in through the electromagnet coils in a 
direction to assist the permanent magnet. But if a stronger current flows, 
the armature is attracted, and sticks to the magnet, until a reverse current 
is sentMn. The spring then draws the armature away, and breaks the con- 
tact of the circuit closer K on W. 

B, a brass ball f inch diameter, held by spiral S. 

T, a silk thread running through the vertical axis of the ball from adjust- 
ing screw to the armature. When the vessel strikes the mine the brass ball 
being knocked sidewise pulls, by means of the string, the armature against 
the poles where it sticks. 

R, 1000-ohm resistance coil, which is cut out of the mine circuit by the 
contact of K on W. 

PC, priming-charge. 

F » fuse# Operating-Box on Shore. 

WB', watching-battery of gravity cells and brass bar. 

FB', tiring-battery of Sampson cells and brass bar. 

P', tiring-plug. 

M'M', ordinary electro-magnet, 100 ohms. (See Relay No. 7.) 

A', armature pivoted at the center. (See Relay No. 7.) 

S', spring holding armature back against a weak current. (Relay No. 7.) 

I/, shutter arm pivoted above its center of gravity. When set as in relay 
No. 1, shutter-arm 1/ makes electrical connection with the armature at N' ; 
when armature is attracted it releases L', whose lower end strikes a bell, and 
makes electrical contact with the tiring-bar at B'. 

b, terminal of mine circuit which may be plugged to WB 7 . 

a, terminal for testing-set. 

o, o, two reversing-keys. 

Xand Y are two stations, 1 to 3 miles apart, each having a key and an ob- 
server of the mine field. 

Operation. 

The torpedo having been planted and connected with its relay, whose 
shutter-arm 1/ is set as in relay No 1, a small steadv watching-current flows 
through G', WB', b, M'M', H, N', J', O', V, coil S, coil, N, W, R (1,000 ohms), 
G to G' again. The direction of the current is such as to preserve the mag- 
netism of the magnet. If the circuit closer is accidentally closed (indicated 
by a change of the resistance in the circuit) it can be opened by using the 
reversing-key from shore. 

The fuse F may be tired in four ways : — 

(a) By contact ivith the mine only. Insert firing-plug P'. When a vessel 
strikes a mine the brass ball B in the circuit-closer is thrown aside, closing 
K on W and thus short circuiting R. The watching-current, thus made 
stronger, flows from coil N through K, A, Z, fuse, G /7 to G'. Coming from 
gravity cells it cannot fire the fuse, but is strong enough to operate the relay 
and drop I/, which throws in the firing-battery. A strong current now flows 
through G", FB', P', B', J', O', V, coil S, coil N, W, K, A, Z, F, G„ to G" 
again, and fires the fuse. 

(b) At will of operator only, who may at any time drop the shutter arm L' 
by hand and insert the firing-plug. The firing-current is strong enough, 
even through R in the torpedo, to close K, short-circuiting R, and to fire 
the fuse. 

(c) By contact with the mine and at operator's will. Remove firing-plug 
P'. The watching-current flows as above in (a). When the vessel strikes 
the mine 1/ drops, striking the bell, when the operator inserts P', throwing 
in the firing-current which fires the mine. 

(d) By observation from two stations ; shutter arm 1/ set, and firing-plug 
P' in. When a hostile vessel appears over the mine from the position of X 
the observer closes his key. Y has like instructions. When both keys are 
closed the main part of the current from WB' flows through G', WB', b, 
M'M', H, Q', X, Y, G, to G' again, drops the shutter-arm and fires the mine. 

For obvious reasons the foregoing is not a description of the service cir- 
cuit closer, but the principle of construction and operation of the mines of 
all countries are much alike- 



1140 USES OF ELECTRICITY IN UNITED STATES ARMY. 



fortress Telephones and Telegraphs. 

Covering as it does a considerable area, the modern fortification must have 
its several units within instant communication, in order to insure that con- 
cert of action so necessary to a successful command. The fort commander 
must communicate his orders to the battery commanders, and they in turn 
transmit the necessary commands to the gun commanders; and while much 
time and ingenuity has been spent in devising means of communication 
through the medium of printing and dial telegraphs, the telephone is to-day 
practically the universal method of communication from one part of a fire 
command to another. As ordinary commercial telephones are employed, no 
special description of them need be given in this section. The telephone is 
however, at best, but an unsatisfactory method of communication, and will 
be rendered more so by the noise and confusion of battle. 



Field Telephones and Telegraphs. 

For communicating in the field operations of an army, where portability is 
of primary consideration, several forms of apparatus have been devised by 
the Signal Corps. 

Field Telegraphy. — This outfit is contained in an oak case 
13i X 7 X 8f inches, with a leather carrying strap, and weighs 18 pounds. 




Fig. 14. Wiring Diagram Field Induction Telegraph. 



It is operated by means of an induction coil, the ratio between the primary 
and secondary wiring being 100 to 1. The magnetic circuit is broken at one 
end to give increased speed. A polarized relay is used. Ihe line battery 
consists of three No. 5 dry cells, giving 4^ volts. This apparatus works 
successfully for 250 to 300 miles over No. 9 galvanized iron wire. lig. 14 
shows the circuit. . 

Field Telephone. — Outfit is contained in an oak carrying case, 
10 X 5f X 10 inches, and weighs 20 pounds; has a hand set receiver and 
transmitter, and magneto call. Two No. 6 dry cells are used for transmitting 
circuit. 

Field Buzzer. — This is a combined telephone and telegraph instru- 
ment, working on principle of self-induction. Interruption is very rapid, 
giving a high-pitched note. Telephone receiver is used for sounder when 
employed as a telegraph instrument. This is a very efficient instrument and 
will work over a line through which ordinary instruments cannot possibly 
operate. Has been operated over line of 30 miles of bare wire lying on 



TELAUTOGRAPH. 



1141 



ground and practically short-circuited all the way; also over 18 miles with 
breaks in line totaling 20 feet. The outfit is contained in a leather carrying 
case 1(H X 5i X 8i inches, and weighs 11 pounds. 

Telephone Switchboard. — The Signal Corps also # employs a 
portable telephone switchboard, mounted on a tripod and weighing about 75 
pounds. This has a capacity of 10 lines, cordless connection and magneto 
call. It can be set up in a few minutes. 

Wire. — Three different grades of wire are used. One form consists of 
2 strands of steel and 1 of copper, cotton covered, weighing about 12 pounds 
to the mile, carried on reels of one-half mile. Another grade consists of 11 
strands of steel and 1 of copper, rubber covered and braided. This is capable 
of standing very rough usage. A third type of wire, but little used on ac- 
count of its weight, consists of 19 strands of steel and one of copper. 

THE TEIAIIOGRAPH. 

In the transmission of ranges and azimuths from the observers, where 
great accuracy is required, the telautograph is largely employed. The fol- 
lowing description of this instrument is taken from "Handbook for the Use 
of Electricians," Government Printing Office, 1904. 

Description, Principles, and Operation. 

Transmitter. — By means of two light rods attached to the trans- 
mitting pencil near its point, the arbitrary motions of writing or drawing are 
resolved into simple rotative or oscillatory motions of two pivoted arms, 
located on either side of the writing platen. These arms are included in the 
line circuits and carry at their extremities small contact rollers which move 
to and fro upon two rheostats, or resistance coils, these being so connected 
through the arms to the line and to the source of energy as to act both as 
adjustable shunts and as rheostats in the line circuits. _ By this method the 
voltage supplied to the line is made to vary with the position of the pencil upon 
its writing platen, and definitely variable writing currents are transmitted. 

Receiver. — The receiver principle is equally simple. The variable line 
currents coming in over the line wires are led through two vertically mo vable 
coils, each suspended in a strong uniform magnetic field by a well-sweep 
arrangement, from which they derive the name of "buckets." 

Each coil is supplied with an adjustable retractile spring which tends to 
oppose the movement of the coil downward through the field. It is evident 
that for given values of the line currents each coil will have a definite position 
in its respective magnetic field, depending upon the tension of its retractile 
springs. The vertical motions of these receiver "buckets," due to the vary- 
ing line currents, are used to cause rotative motions in two pivoted arms, 
similar to those at the transmitter, which motions, through another system 
of light rods, compel the receiving pen to exactly reproduce the motions of 
the transmitting pencil. 

To accomplish the pen-lifting at the receiver an automatic device is used, 
consisting of an induction coil at the transmitter, haying two secondary 
windings and performing the double function # of pen-lifting and reducing 
friction. The primary circuit of this coil is entirely local at the transmitter, 
and includes an interrupter and a shunt circuit controlled by the platen. < 

The vibratory secondary currents m are superimposed upon the writing 
currents, and serve to # keep the receiving pen in continual though impercep- 
tible vibration, reducing friction in the moving parts to a minimum. The 
normal writing pressure of the pencil upon the transmitter platen opens the 
shunt circuit and causes an increase in the strength of the secondary vibra- 
tions. This operates a vibratory relay inserted in one of the line circuits at 
the receiver, opens a local circuit, and causes the armature of the pen-lifting 
magnet to be released and the pen is allowed to rest upon the paper. 

Lifting the transmitting pencil from the platen decreases the strength 
of the vibrations, closes the local receiver circuit, and the pen-lifting magnet 
attracts its armature and raises the pen clear of the paper. 

The shifting of the paper at the transmitter is done mechanically by 
means of the master switch. The same motion of the switch operates an 
electromagnetic device over one of the line wires, which automatically and 
positively shifts the paper at the receiver a corresponding amount. 



1142 USES OF ELECTRICITY IN UNITED STATES ARMY. 

The paper, 5 inches wide, is supplied in conveniently detachable rolls, 
which are mounted in brackets attached to the backboard of the instrument. 
For signaling, a push button at the transmitter operates a call bell at the 
receiver. 

The transmitting pencil is a simple adjustable lead pencil. The receiving 
pen is made on the principle of the ordinary right-line drawing pen, so 




Fig. 15. 



TELAUTOGRAPH. 1143 



modified as to make perfect lines regardless of the direction of motion, and 
capable of holding an ample supply of ink. 

The inking device consists of a bottle or supply well, with a hole and 
stopper for refilling, and also with a second small hole in the side of the well. 
This hole is below the surface of the ink, and the top of the well being corked 
and airtight, the ink is prevented from flowing out by the pressure of the 
external atmosphere. 

The small hole is located at the unison point, and whenever the paper is 
shifted the pen returns to this position and automatically dips its point into 
the ink which stands at the mouth of the hole. Capillary attraction is 
sufficient to completely fill the pen, and, resting in the hole as it does, the 
point does not clog up with dry ink when not in use, but is always ready to 
start writing with a full fresh supply. 

Explanation of Diagram, (fig*. 15.) 

1. Transmitter. — The motions of the transmitting pencil A are conveyed 
through the pencil arms BB', and pencil arm levers CC to contact arms 
DD', which carry contact rollers EE', these contact rollers bearing upon 
the periphery of rheostats FF', the terminals of these rheostats being con- 
nected through master switch G to the positive and negative poles of a 
suitable source of electrical energy, indicated by battery H. The con- 
tact arm D' is connected to the right line through one of the secondaries 
of the induction coil /, and through the right-line contacts G' of master 
switch, when the master switch is in the writing position as shown. The 
contact arm D is connected to the left line through the other secondary of 
the induction coil /, through the left line contacts G2 of master switch. The 
writing platen J is pivoted at KK', and when pencil is off the platen closes 
upper contacts LL', shunting resistance I around the primary winding of 
induction coil J. The vibrator M is in circuit with the primary of induc- 
tion coil i" and battery H, and rapidly vibrates, the current passing through 
the primary of the induction coil, thus causing a vibratory current to trav- 
erse the right and left line wires, the strength of this vibratory current 
depending upon the position of the platen J; when this platen is depressed 
by the pencil in the act of writing the shunt around the primary of induc- 
tion coil / is open, consequently the strength of the vibratory currents on 
line is increased; this increased strength of vibration actuates the pen-lifting 
relay m (in receiver). The paper at the transmitter is shifted by moving 
the handle N of lever 0, which is connected to shaft P, which carries the pawl 

g, engaging the ratchet wheel R, mounted on shaft of paper-shifter roller S. 
ach movement of this handle N to and fro causes the roller S to rotate, 
which moves the paper forward. The shaft P also carries master-switch 
contact plates G, Gl, G2, which open and close the line and battery circuits, 
according to the position of handle N; circuits being closed and instrument 
in sending position when handle N rests in position shown by arrow. The 
movement o* the handle N in the opposite direction cuts the instrument out 
of circuit. The handle is locked in either position by lever P, and cannot 
be released except by pressing point of pencil A on button T. A signal- 
switch push button is shown at U; this switch when operated throws current 
of positive polarity through right line, which rings receiver bell, u, as here- 
after described. 

2. Receiver. — The motions of receiver pen a are caused to duplicate 
the motions of transmitting pencil A through the pen arms bb', pen-arm levers 
cc', which are mounted on shafts carrying sectors dd' . Light metal bands 
ee' are attached to the peripheries of sectors dd' and carry at their lower ends 
coils (or "buckets") ff', and their upper ends are attached to springs gg'. 
The coils ff are movable in the annular spaces between the poles of the mag- 
nets h and i, and h' and i'. Coil / is in circuit with Morse relay j and the left 
line, and coil f is in circuit with pen-lifting relay m and the right fine. As 
the transmitting pencil is moved its motions are transmitted to contact 
rollers EE', the strength of current on line is varied, the currents becoming 
stronger as the rollers approach the positive ends of .the rheostats FF', these 
currents traversing line and passing through coils ff', causing them to take 
different positions in the magnetic fields, opposing the pulls of the springs 
go*, these springs being so adjusted that the position of the receiving pen in 
the writing field will always be the same as the position of the transmitting 
pencil on its writing platen. 



1144 USES OF ELECTRICITY IN UNITED STATES ARMY. 

3. The depression of platen J, causing a strong vibratory current to trav- 
erse line, causes the armature of pen-lifting relay m to vibrate and interrupt 
the circuit of pen-lifter m' ', thus releasing the armature of pen-lifter and 
lowering the pen-arm rest so as to allow the pen to come into contact with 
the paper. Upon raising the transmitting pencil from its platen the vibra* 




Fig. 16. Telautograph. 



tory current will be weakened, the armature of pen-lifting relay m ceases to 
vibrate, closes the circuit of pen-lifter ra', which attracts its armature and 
thus lifts the pen from the paper. 

4. The paper-shifter o' is an electromagnetic device and is controlled 
by the Morse relay j, the armature of this relay closing the circuit of the 
shifter through its forward contact when the relay j is energized by line cur- 
rent through the master switch by the movement of handle N in the position 
ehown by arrow. 



WIRELESS TELEGRAPHY. 1145 

5. The signal bell u, which is of low resistance, is thrown in parallel with 
the right-line coil, or "bucket" /', when no current is passing through the 
paper-shifter, consequently when signaling current passes over right line 
the bulk of the current passes through the bell, rather than through coil /'. 

6. The ink well (an ordinary glass bottle) is shown at p, the receiver pen a 
entering the opening p' and receiving a fresh supply of ink every time the 
paper is shifted, the pen resting in this opening and in contact with the ink 
when the instrument is not in use. 

Installing*. 

The instruments are furnished with a suitable backboard, the connections 
being made between the instruments and the circuits on the backboard by 
automatic contact pins, so that the instruments can be put on and taken 
off readily. The terminals on the backboard for connecting to line and 
battery are plainly marked so that the proper connections may be easily 
made. 

Operation. 

1. To write. — Depress button with pencil point and pull lever towards 
you a full stroke; release button with lever in this position, and write with 
firm pressure on paper. 

2. Xo shift paper. — Depress button, holding it down until you have 
moved lever back and forth its full stroke as many times as you wish to 
shift paper, then release button with lever in position towards you. 

3. Xo hang* up. — Depress button, allowing lever to rest in position 
away from you. Always, after writing, leave the lever in position from you. 

Care of Instruments. 

The care of the instruments consists mainly in keeping the ink bottles 
properly filled with the ink which is supplied for that purpose, the occasional 
cleaning of the pen points, and the insertion of fresh rolls of paper which is 
supplied for that purpose. 

WIHEIJESS XEIEGRAPHY. 

The wireless telegraph outfits used in the Army have been developed by 
the Signal Corps, and embody some of the best features of other systems. 
One of the most effective outfits is that designed to be carried on pack mules. 
For this purpose it is divided into three loads, each weighing approximately 
150 pounds, the transmitting and receiving apparatus, the batteries, and the 
poles for aerial wires. 

The transmitting and receiving apparatus is contained in a leatheroid trunk 
30 X 17 X 14 inches inside measurement. Fig. 17 shows the wiring arrange- 
ment. Current is furnished from storage batteries or by hand generator. 
The storage battery consists of 8 cells of about 50 amp .-hour capacity. The 
ratio of the induction coil is about 1 to 200. About 16 volts are required in 
the primary. The key is an ordinary open circuit key with extra large 
platinum contact points. A special double head telephone receiver is used. 
Two types of detectors are employed, electrolytic and silicon. The electro- 
lytic detector is similar to that used commercially, but differs in design. 
The silicon detector is that invented by G. W. Pickard in which the action 
is thermo-electric, and is in form of a brass contact resting on the silicon 
crystal, which is embedded in a brass cup. 

The aerial wires are supported on a jointed pole 60 feet in height. The 
pole is hollow and is made of spruce in 9 sections, 6 feet 8 inches long and 2i 
inches in diameter. The aerial consists of 6 umbrella wires, 85 feet long, and 
6 counterpoise wires, 75 feet long. The counterpoise is used in preference to 
ground. The aerial wires are formed of 42 strands of No. 33 phosphor 
bronze twisted around a hemp center. They have a tensile strength of 300 
pounds and weigh about 7 pounds per thousand feet. 

With a similar station receiving, this outfit has been successfully operated 
over a distance of 27 miles. 

Kites are sometimes used for supporting the aerial wires, and with the 
height thus obtainable messages have been received over 600 miles. 

Small wireless telegraph outfits have been made, weighing approximately 
40 pounds, capable of covering 3 or 4 miles. 



114t> USES OF ELECTRICITY IN UNITED STATES ARMY 



^ffirtHft- 




CONTROL SWITCH 

When Control Switch handle is turned toward 

plug socket (9), connectious are as follows :- 

1 with 2, 3 with-4, and 5 with 6. 

When in positioD shown 7 is connected ^groons P^" 

with 8, Point 6 on Control Switch should 

be connected to different ground from 

point marked G. 



Fig. 17. Field Wireless Set- Pack. Trunk Type, Wiring Diagram. 



ELECTRIC AMMUNITION HOIST. 



1147 



ELECTRIC AJIOKUltflTIOltf HOIST WITH AUTO- 
MATIC IAFETY STOP. 

As its name implies this apparatus is used for raising ammunition from 
the magazines to the gun positions. 

It is applied to two platforms, G G, Fig. 18, either of which is drawn 
upward, while the other descends, by a winch driven by a motor through 
worm or train gear. A 5-horse-power motor can raise 2,000 pounds counter- 
weighted by 600 pounds of the other platform at the rate of 1 foot per second. 
The design is simple, inexpensive, and the motor and hoist are fairly well 
protected. 

1. M is the motor with both series and shunt fields, the latter being 
excited when MS is closed. RS is a three-pole reversing switch shown in 
position for the right-hand platform to ascend. 

2. The controller has a starting rheostat, Rh; a hand lever, W ; a spring 
lever, V; an underload release, UL; and an overload release, OL. The 




Fig. 18. Ammunition Hoist. 



magnet UL depends for its excitation upon the voltage of the motor termi- 
nals and also upon the integrity of its circuit at any one of the four points 
OL, RS, E, or F. The main circuit from MS is through the electromag- 
netic brake EB, series fields OL, to the contact piece b, when the lever V 
is held down by UL magnet, the circuit is closed from b through d, V, W, 
Rh (or direct after the motor has attained full speed), to RS, M to MS. 

3. The main circuit is broken either when the lever V is released (e and 
/ taking the spark), or when W is moved to the left (k and I taking the 
spark). The lever V, when released by UL, is carried to the right by the 
spring at its axis until it strikes W. The rheostat may be designed for 
running the motor continuously at different speeds, or as a starting box 
not to be in the circuit longer than thirty seconds. 

4. S is a baby switch held open by a spring. Its object is to close, if 
desired, the UL magnet circuit when open at E or F. 

5. A and A are the devices for automatically breaking the circuit through 
UL, and thus the main circuit when the platform ascending strikes the lug 
g, which is adjustable on the bar sliding in guides h. On the lower end of 



1148 USES OF ELECTRICITY IN UNITED STATES ARMY. 

this bar an insulate copper wedge makes, when down, contact between two 
copper terminals at E or F, and breaks it when up, thus making or breaking 
the circuit through UL. E and F are alike and adjustable vertically 6 
inches. 

6. The right-hand platform is at its upper level, the left-hand is at its 
lower; the circuit through armature M has been broken and V is up against 
W. If now we try to start the motor without reversing RS, the circuit 
through M will still be open at E. But throw RS down and the circuit 
through UL will be closed at F, and the left-hand platform can be raised. 

7. To start the motor at all, TF must always be brought up to the left, 
pushing V before it until held by the underload magnet UL, then W may 
be moved to the right, closing the circuit first through Rh and at last with- 
out it. 

8. When the left-hand platform, on nearly reaching its upper level, 
engages g and opens F, the main circuit will be opened at b and the motor 
will stop. 

9. If it is necessary to move the platform farther up after the circuit 
has been broken at E or F, the switch S may be closed and the platform 
may then be moved by the motor. So long as S is closed V will not be 
released except for no voltage or overload. 

10. The motor may be slowed down or even stopped by moving W to 
the left, provided Rh is large enough to carry the current. 

11. The electromagnetic brake on the gear wheel next the motor arma- 
ture automatically clamps it whenever the main current ceases and the 
motor stops. It gives a quick stop for heavy or light loads. 

12. If the electric machinery is disabled the motor is quickly thrown out 
and the platform can still be raised by a crank handle and gearing. 



XIOHT SIGHTS. 

Electric night sights for rapid fire guns consist of a fitting and stem 
which can be inserted in the front sight bracket in place of the bead sight 
used in daylight. This fitting receives an encased white electric light 
which illuminates a glass cone set under a pierced cap, so that the point of 
the cone only is visible as a bead to be used in aiming. The light proper 
is shipped into a holder and down over two plug pins to the other end of 
which the cable wires are soldered (Fig. 19). The rear edge of the rear 



(WHITE GLASS 

^23 COPPER WIRES-.500 IN. DIA- 
-SOFT RUBBER INSULATION 




^BRAIDED COTTON 
LENGTH OF CABLE- 3.FEET S ° FT RUBBER - 

Fig. 19. Front Electric Light and Plug Connections. 



sight ring is grooved and the groove baked full of scarlet enamel, which is 
illuminated by an encased red electric light, fitted similarly to the front 
light. Power is obtained from a battery consisting of ten O.K. dry cells, 
No. 4, If by 2| by 5f inches high. Four cells are connected in series through 
a rheostat to each lamp, a fifth cell in each case being held in reserve to put 
into the circuit when the four cells fail to give proper light. 

For use at night, range finders are equipped with lights for illuminating 
the cross-wires of the instrument. The illuminating device consists of two 
small electric lamps in sockets attached to the rear, or eye-piece, end of the 
telescope, the beam of light from each lamp being reflected on the cross- 
wires by two small mica mirrors. The lamps are approximately $ c.p., 
and 4 volts. Power is obtained from the main lighting circuits through 
Bui table resistance. 



FIRING MECHANISM FOR RAPID FIRE GUNS. 



1149 



HROG MECHAHISm IOII RAPID IIRE «£TJ]¥S. 

The electrical power for firing rapid fire guns is obtained from two O.K. 
dry batteries, each consisting of eight cells in series. These batteries are 
not used simultaneously, but one is kept for use in case the other should 
fail. Each battery is stowed in a covered box, carried in brackets bolted 
to the side frames of the gun carriage. A third box is similarly carried for 
stowing the alternative firing cable. The battery carried on the left is 
ordinarily used to fire the piece through the pistol connection, while the 
one on the right is used with the alternative firing key. 

One terminal of each battery is attached by a short cable to the frame of 
the carriage as an earth connection. The other terminal of the battery on 




Fig. 20. 



the left side of the frame is connected by a cable 4 feet long with the front 
nipple under the pistol (Figs. 21 and 22). When the trigger is pulled the cir- 
cuit is completed to the rear nipple, from which a cable, 5 feet 5 inches long, 
passing under the cradle and through a twisted hook to the right side 
connects with the contact surface plug. This is bracketed to the cradle in 
such position that when the piece returns into "battery" from recoil, the 
contact pin, pressed out by a spring in the contact-pin plug, attached to 
and moving with the recoil band and piece, presses upon the contact sur- 
face of the plug before mentioned. The connection for the next shot is 
thus made. 

From the contact-pin plug the firing-pin cable extends through a locking 
pin at the hinge of the breech mechanism to the firing pin, the last 10 inches 
being armored for protection (Fig. 22). To enable the cannoneer who 
fires the piece to ascertain whether the breech block is entirely closed and 
the connections otherwise complete, a buzzer is incased with the pistol, 
(Fig. 20) so that when the button over the trigger is pressed by the thumb 
a circuit is completed through a resistance coil, which permits just enough 
current to pass to sound the buzzer, but not enough to explode the primer, 
if kept on for an instant only. The ear must be held close to the buzzer 



1150 USES OF ELECTRICITY IN UNITED STATES ARMY. 




lt- J 4^vMHf 



i ■ taH 




i^fefc 



fFitf 



W 



FIRING MECHANISM FOR RAPID FIRE GUNS. 



1151 



to detect the sound. When the trigger is pulled, a direct circuit is completed, 
permitting the full current from the battery to pass through the primer, thus 
firing the piece. 

In case the pistol or its connections become short circuited, or the insula- 
tion fails, the cable can be quickly disconnected from the battery and firing 




Fig. 22. 



pin and the pistol lifted out of its slot. The surface-contact plugs are then 
disconnected by withdrawing the locking pins which engage with bayonet 
studs in the contact-plug block, after which another pistol and cables may 
be applied or the alternative firing key and cables used. 

In the alternative battery, in the front box on the right side of the frame, 
the other terminal is directly connected with the firing pin through the 



TWISTED WIRE CABLE, 6. IN. LONG 




Fig. 23. Alternative Firing Key and Cables. 



alternative firing key and cables about 11.5 feet long. The length of these 
cables is such that the key may be taken under the piece to the left side 
and used by the cannoneer who is aiming. 

The alternative key (Fig. 23) consists of a tube into one end of which a 
cable end is coupled fast. The cable entering the other end is secured to a 
plunger which is held out by a coiled spring. When grasped in the hand 



1152 USES OF ELECTRICITY IN UNITED STATES ARMY. 



with the thumb on the plunger end, the cable ends may be pushed together, 
completing the circuit. To guard against a premature discharge of the 




CONTACT PIN PLUG 



CONTACT 
SURFACE PLUG 



Fig. 24. 



piece, a split key is wired to this firing key to prevent forward movement 
of the plunger, and this is kept pushed under the plunger head until the 
piece is about to be fired. Figs. 21 and 22 show the connections for both 
night sights and firing circuits, and Fig. 24 gives details of the contact plugs. 



ELECTRICITY IN THE UNITED STATES 
NAVY. 

Revised by J. J. Chain. 

At the present time (January, 1908) the standard practice on ships of the 
United States Navy is to use direct current, at 125 volts, distributed on 
the two-wire system. Previous to 1902 the standard was 80 volts, conse- 
quently many vessels have apparatus of that voltage. 

A ship's installation is conveniently divided into dynamo room, lighting 
system, power system, and interior communication system. The wiring of 
each system is kept entirely separate from the other. 

The dynamo room contains the generating sets, main switchboard, and 
sometimes condensers for the engines. 

The lighting system supplies all ship's lights, searchlights, and signal 
lights. These are installed in two separate systems called " Battle Service " 
and " Lighting Service." Battle service comprises all lights necessary dur- 
ing action, and these lights are arranged so as to be invisible to the enemy. 
Lighting service comprises the additional lights necessary for ordinary hab- 
itation. 

The power system supplies the various electric auxiliary machinery which 
at present consists of all ammunition hoists, turret turning gear, elevating 
and ramming gear for the larger guns, boat cranes, deck winches, ventilat- 
ing fans, water-tight doors, and motors for driving line shafting in laundry 
and engineer's workshop. Anchor handling gear and steering gear are at 
present always steam driven, but electric devices are being experimented 
with. The auxiliaries in the engine and boiler rooms, consisting of numer- 
ous pumps and the forced draft fans, are all steam driven, except in a few 
vessels not yet finished where electric forced draft fans are being installed. 

The interior communication system consists of various devices for trans- 
mitting signals and orders from one part of the ship to another. Most of 
these are electric, but in some cases they are paralleled by mechanical 
equivalents, as, for example, voice tubes paralleling telephones. 

DYNAMO ROOM. 

The generating plant is located in a compartment called the " Dynamo 
Room," which is under the protective deck and adjacent to the boiler 
rooms (when practicable), so as to secure a direct lead of steam pipes. 

OIYEHiTIYGSETS. 

The following are the principal requirements contained in the standard 
specifications for reciprocating generating-sets : 

General Requirements. 

Each set to consist of an electric generator direct-coupled to a steam 
engine, both mounted on a common bedplate. 

The sets as a whole shall be as compact and light as is consistent with a 
due regard to strength, durability, and efficiency. The standard nizes, with 
their corresponding maximum allowable speeds, weights, and over-all di- 
mensions are : 



Size in 


Revolutions 


Weight in 


Length in 


Width in 


Height in 


kilowatts. 


per minute. 


pounds. 


inches. 


inches. 


inches. 


2.5 


800 


560 


32 


20 


30 


5 


750 


1,300 


50 


28 


40 


8 


550 


2,500 


64 


34 


50 


16 


450 


5,600 


78 


40 


60 


24 


400 


7,300 


88 


48 


68 


32 


400 


10,000 


101 


52 


.78 


50 


400 


16,000 


110 


60 


85 


100 


350 


22,000 


125 


70 


95 



1153 



1154 ELECTRICITY IN THE UNITED STATES NAVY. 



The design shall provide for accessibility to all parts requiring inspection 
during operation, or adjustment when under repair. Sets are to he designed 
to operate right-handed, i.e., counter clockwise when facing the commutator 
end, or left-handed, as required. The design to be preferably such that the 
same parts may be used in each, in order to avoid increase in number. 

The sets must be capable of running without undue noise, excessive 
wear, or heating. Must be balanced and run true at all loads, up to 33£ per 
cent above rating ; must be capable of running for long periods under full 
load and without continued attention. 

Cast or wrought iron shall not be used for bearing surfaces, except in 
cases of cylinders, valve chests, and crosshead slides. Both upper and 
lower halves of main bearings to be removable without removal or displace- 
ment of shaft. 

The driving shaft must be fitted with thrust collars or other suitable de- 
vice which will prevent a movement of the shaft in the direction of its 
length, as might be caused by the rolling of the ship. 

The combination bedplate to be a substantial casting, and provided with 
accurately spaced drilled holes for securing to foundation. 

An oil groove of ample width and depth to be cast in the upper flange of 
bedplate, to be continuous around the engine, and to be provided with a 
stopcock for drainage. The lower side of the combination bedplate to be 
planed perpendicular to the line of stroke of engine. 

Seats for all bolt heads and nuts to be faced. All nuts to be case hardened, 
and to be U. S. standard sizes. Where liable to work loose from vibration, 
nuts are to be secured by use of jam nuts and spring cotters. All bolt ends 
to be neatly finished. 

The two halves of the main coupling to be either keyed to or forged solid 
with the engine crank and armature shaft. The coupling to be bolted^ to- 
gether by well-fitted bolts, driving to be done by a cross key set in 'the 
faces. 

Adjoining portions of the machinery shall be given corresponding marks 
whenever this may be desirable for insuring correct assembly. 

Interchangeability among the different sets and their sparse parte, of the 
same size and make, as furnished in any one contract, is required. This to 
be demonstrated as part of the final test for acceptance. 



Engines are to be of the automatic cut-off vertical enclosed type, designed 
to run condensing with maximum practical efficiency at all loads, but 
capable of satisfactory operation when running noncondensing, to be of 
sufficient indicated horse-power to drive the generator for an extended time 
at the rated speed, when said generator is carrying a one-third overload. 

Sizes 2| K. W., 5 K. W., and 8 K. W. to be simple engine, single or twin 
cylinder at the option of the contractor. Sizes of 16 K. W. and above to be 
cross-compound with cranks set at 180°. 

The normal steam pressure under which the engine, running condensing 
with 25-inch vacuum, for different size sets, is to operate, and the maximum 
allowable water consumption per K. W. hour output of the set are : 



K. W. 


Normal steam 
pressure. 


Water consumption 

per K. W. hour, 

full load. 


2.5 


100 


105 


5 


100 


90 


8 


100 


65 


16 


100 


44 


24 


100 


40 


32 


100 


37 


50 


100 


35.5 


50 


150 


33.5 


100 


150 


31 



ENGINE. 1155 

In testing, corrections shall be made by calorimeter for entrained mois- 
ture. Superheating shall not be used in the test. 

Engines must run smoothly and furnish the required power for full load 
at any steam pressure within 20 per cent (above or below) of those given in 
the above table, and exhausting to condenser at 25 inches vacuum ; to fur- 
nish power for 90 per cent of full load at steam pressure 20 per cent below 
normal, and for full load at any steam pressure between normal and 20 per 
cent above normal, when exhausting with the atmosphere. Must be able to 
bear without injury the sudden throwing on or on* of one and one-third 
times the rated full load of the generator, by making and breaking the 
generator's external circuit. 

To be so designed that the work done by each cylinder, as shown by indi- 
cator cards, will be as nearly equal as practicable under all conditions of 
load. Indicator motions must be provided which will accurately reproduce 
the motion of the pistons at all points of the stroke. This will require, for 
cross-compound engines, the operation of the reducing motion for each 
cylinder from the crosshead or other moving part belonging to that cylinder. 

Indicator piping to be installed in a manner to secure accuracy of indi- 
cator cards. Connections to be made at each end of each cylinder, and 
piped to a three-way cock in order that one indicator may be used for both 
head and crank ends of cylinder. Connections are to fit the standard indi- 
cators of the Bureau of Equipment. 

The length of stroke of the engine to be not less than the diameter of the 
bore of the high-pressure cylinder. 

The cylinders to be made of hard, close-grained charcoal iron, bored and 
planed true, of sufficient thickness for operation after reboring once, steam 
and exhaust ports to be short, of ample area and free from fins, scales, 
sand, etc. Cylinders to be fitted with the usual drain cocks, all drains to 
end in one outlet. In addition to these drains, relief valves are to be fitted 
to each end of each cylinder, and both high-pressure and low-pressure valves 
are to be free to lift from their seats to relieve the cylinder of water. 

The low-pressure cylinder must be fitted with a flat, balanced slide valve ; 
a piston valve on the low-pressure cylinder will not be accepted. 

The pistons to be of cast iron or steel, strongly ribbed, light and rigid, 
and fitted with self-adjusting rings, each piston to have two or more rings. 
Rings to override counterbore of cylinders, to prevent wear to a shoulder. 

Piston rods to be of forged steel securely fastened to pistons and cross- 
heads. Crossheads to be of steel with adjustable shoes. Connecting rods 
to be of steel with removable babbitt-lined boxes for crank pins and bronze 
boxes for crosshead pins. 

The crank shaft to be forged in one piece ; counterweights for balancing 
reciprocating parts to be forged with it or securely fastened thereto. Valve 
rods, eccentric rods, and rocker shafts, as well as all finished bolts, nuts, 
etc., to be of best forged steel. 

Lagging shall be fitted as extensively as practicable to cylinders, receiv- 
ers, and steam chests. This shall be done after a preliminary run of the 
engine in order that any defects in castings or joints may be readily found. 
The arrangement for securing the lagging in place shall admit of its ready 
removal, repair, or replacement. 

The steam and exhaust outlets shall be so placed as to admit of piping 
from either side with equal facility. Blank flanges shall be furnished com- 
plete when required to cover alternative outlets. 

Throttle and exhaust valves to be 90-degree-angle valve, looking up, un- 
less otherwise specified. Handwheels to be marked, indicating direction of 
turning for opening and closing. When so directed, larger sizes shall be 
furnished with by-pass valves for warming up cylinders. 

The governor to be of the weight and spring type, arranged to operate the 
high-pressure valve by a shifting eccentric, thus automatically varying the 
valve travel and point of cut-off. No dashpots or friction washers shall be 
used in its construction. 

The speed variation must not exceed 1\ per cent when load is varied 
between full load and 20 per cent of full load, gradually or in one step, engine 
running with normal steam pressure and vacuum. A variation of not more 
than 3$ per cent will be allowed when full load is suddenly thrown on or off 
the generator, with constant steam pressure either normal, or 20 per cent 
above normal; a variation of not more than Z\ per cent will be allowed 
when 90 per cent of full load is suddenly thrown on or off the generator, with 



1156 ELECTRICITY IX THE UNITED STATES NAVY. 

constant steam pressure 20 per cent below normal, exhaust in both cases to 
be either into condenser or atmosphere. No adjustment of the governor 
or throttle valve during the test shall be necessary to insure proper per- 
formance under any of the above conditions. 

The engine column to be designed to enclose all moving parts as far as 
practicable, or where weight may be saved, by using a wrought-steel frame 
with an enveloping enclosure of metal. Detachable hinged doors to be pro- 
vided for examining moving parts while in operation. The design to elim- 
inate all chance of oil or water leaking or being forced through. 

Stuffing boxes for piston rods to be slightly longer than length of stroke, 
in order that no part of the rod exposed to the oil in the enclosure will enter 
the cylinder. Stuffing boxes for piston rods and valve rods to be accessible 
from the outside of the enclosing case of the engine. 

A guard plate to be provided to prevent oil from being thrown against 
the lower cylinder heads and valve chests. 

Engines are required to operate satisfactorily without the use of lubri- 
cants in the steam spaces. The lubrication for all other working surfaces 
shall be of the most complete character. No part shall depend on squirt- 
can lubrication. 

Forced lubrication shall be used wherever practicable, which includes 
engine shaft, crank pins, crosshead bearings, eccentric, etc. The engine 
shall be capable of satisfactory operation with a low grade of lubricating 
oil, and the forced lubrication shall not be a necessary factor in its cool and 
satisfactory running. The intent of the forced lubrication is to 'reduce 
friction, noise, and attention required. 

The pressure for such forced lubrication shall be approximately 15 pounds 
per square inch, and shall be between 10 and 20 pounds under all service 
conditions. 

The bedplate is to contain a reservoir and cooling chamber of ample ca- 
pacity, to be provided with a strainer which may be removed without inter- 
rupting the oil supply. The pump to be direct driven by a crank or eccentric 
on the engine shaft, construction to be simple and durable, and to include 
a proper guide or support for the plunger rod. The pump to handle clean 
oil only, not drawing from the top or bottom of reservoir. 

To allow inspection while running, the engine crank is not to dip in oil in 
reservoir. 

Fly wheel to be turned on face and sides, inner edge to be flanged to 
retain any oil which may drip thereon. Hub to be split and clamped to 
shaft by through bolts. A steel starting bar or its equivalent to be fur- 
nished in sizes of 16 K. AY. and over, the fly-wheel surface to have not less 
than six holes for starting bar. 

Mandrels, with collars, complete, shall be furnished for renewing white 
metal of all bearings so fitted., 



GENERATOR, 

To be of the direct-current, multipolar type, compound-wound long- 
shunt connection, designed to run at constant speed and to furnish a 
pressure of 125 volts at the terminals, at rated speed with load varying 
between no load and one and one-third times rated load. 

The magnet yoke or frame to be circular in form, to have inwardly pro- 
jecting pole pieces, and to be divided in half horizontally, in all generators 
above 5 K. W. capacity, the two halves being secured with bolts, to allow 
the upper half with its pole pieces and coils to be lifted to provide for in- 
spection or removal of armature. Pole pieces to be bolted to frame, bolts 
to be accessible in assembled machine to enable removal of field coils with- 
out disturbing armature or frame. Magnet frame to be provided with two 
feet of ample size to insure a firm footing on the foundation. 

Facilities for vertical adjustment of frame to be provided in sizes of 
16 K. W. and above. 

Armature spider to be designed to avoid shrinkage strains. To be 
accurately fitted and keyed to shaft and to have ample bearing surface 
thereon. 

The disks or laminations to be accurately punched from the best quality 
thoroughly annealed electrical sheet steel, slots to be punched in periphery 



GENERATOR. 1157 



of laminations to receive armature windings. Disks to be magnetically 
insulated from one another, and securely keyed to spider or held in some 
other suitable manner to obviate all liability of displacement due to mag- 
netic drag, etc. Space blocks to be inserted between laminations at certain 
intervals to provide ventilating ducts for cooling the core and windings. 

Laminations to be set up under pressure and held securely by end flanges. 
Bolts holding these end flanges must not pass through laminations. 

The commutator bars or segments to be supported on a shell, which must 
be either part of or directly attached to the spider, to prevent any relative 
motion between the windings and these segments. Bars to be of hard 
drawn copper finished accurately to gauge. Insulation between bars to be 
of carefully selected mica and not less than 0.03 inch thick, and of uni- 
form thickness throughout. 

Bars to line with shaft and run true, to be securely clamped by means of 
bolts and clamping rings. Bolts to be accessible for tightening and remov- 
able for repair. 

Brushes to be of carbon. In sizes over 5 K. W. there shall be not less 
than two brushes per stud, each brush to be separately removable and 
adjustable without interfering with any of the others. The point of con- 
tact on the commutator shall not shift by the wearing away of the brush. 

Brush holders to be staggered in order to even the wear over entire 
surface of commutator ; the generator to be provided with some device for 
shifting all the holders simultaneously. All insulating washers and 
brushes to be damp proof and unaffected by temperature up to 100° C. " 

Finished armature to be true and balanced both electrically and mechan- 
ically, that it may run smoothly and without vibration. The shaft to be 
provided with suitable means to prevent oil from bearings working along 
to armature. 

All copper wire to have a conductivity of not less than 98 per cent. 

The shunt and series field coils to be separately wound and separately 
mounted on the pole pieces. The shunt and series coils, respectively, of 
any one set to be identical in construction and dimensions and to be 
readily removable from the pole pieces. The shunt coils as well as the 
series coils are to be connected in series. 

In sizes of 15 K. W. and above a headboard is to be mounted on the 
generator containing the necessary terminals for main switchboard and 
equalizer connections, shunt and series field connections, pilot lamp, and, if 
specified, an approved type of double-pole circuit breaker whose range of 
adjustment shall cover from 100 to 140 per cent of rated full-load current of 
the generator. Field current not to be broken by the circuit breaker. 

The field rheostat to be of fireproof construction suitable for mounting 
on back of switchboard, with handle or wheel projecting through to front, 
either directly connected or by sprocket chain, handle to be marked indicat- 
ing direction of rotation for raising and for lowering voltage of generator. 
The total range of adjustment to be from 10 per cent above to 20 per cent 
below rated voltage, the variation to be not more than one-half volt per 
step at both full load and half load. 

The compounding to be such that with engine working within specified 
limits, field rheostat and brushes in a fixed position, and starting with 
normal voltage at no load or at full load, if the current be varied step by 
step for no load to full load or from full load to no load, and back again, the 
variation from normal voltage shall at no point be in excess of 2 per cent. 

The dielectric strength or resistance to rupture shall be determined by a 
continued application of an alternating E.M.F. for one minute. 

The testing voltage for sets under 16 K. W. shall be 1,000 volts and for 
sets of 16 K. W. and above shall be 1,500 volts, and the source of the alter- 
nating E.M.F. shall be a transformer of at least 5 K. W. capacity for sets 
of 50 K. W. and under, and of at least 10 K. W. capacity for sets of greater 
output than 50 K. W. 

The test for dielectric strength shall be made with the completely as- 
sembled apparatus and not with its individual parts, and the voltage shall 
be applied between the electric circuits and surrounding conducting 
material. 

The tests shall be made with a sine wave of E.M.F., or where this is not 
available, at a voltage giving the same striking distance between needle 
points in air, as a sine wave of the specified E.M.F. As needles, new sew- 
ing needles shall be used. During the test the apparatus being tested shall 



1158 ELECTRICITY IN THE UNITED STATES NAVY. 



be shunted by a spark gap of needle points set for a voltage exceeding the 
required voltage by 10 per cent. 

With brushes in a fixed position there shall be no sparking when load is 
gradually increased or decreased between no load and full load ; no detri- 
mental sparking when load is varied up to one and one-third times rated load ; 
no flashing when one and one-third load is removed or applied in one stage. 

The jump in voltage must not exceed 15 per cent when full load is sud- 
denly thrown on and off. 

The temperature rise of the set after running continuously under full 
rated load for four hours must not exceed the following : 





Method of measure- 
ment. 


Maximum 

allowable rise 

in °C. 


Armature 


Electrical .... 
Thermometer . . . 
Electrical .... 
Electrical .... 
Thermometer . . . 


33$ 

40 

33$ 

75 

40 


Commutator 

Field coils . • 

Shunt rheostat 

Series shunt 







The rise of temperature to be referred to a standard room temperature of 
25° C, and normal conditions of ventilation. Room temperature to be 
measured by a thermometer placed 3 feet from commutator end of the gen- 
erator with its bulb in line with the center of the shaft. 

The generator to be capable of satisfactory operation for a period of two 
hours carrying one and one-third times its rated full load, and no part shall 
heat to such a degree as to injure the insulation. 

Generators of the same size and manufacture to be capable of operation 
in parallel, the division of the load to be within 20 per cent throughout the 
range. The magnetic leakage at full load shall be imperceptible at a hor- 
izontal distance of 15 feet, measurements to be taken with a horizontal 
force instrument. 

The minimum allowable efficiencies of the generators are as follows : 





Loads. 


K. W. 


11 


1 


i 


* 




Per cent. 


Per cent. 


Per cent. 


Per cent. 


2.5 


78 


78 


76 


73 


5 


80 


80 


78 


75 


8 


84 


84 


83 


80 


16 


87 


87 


86 


84 


24 


88 


88 


87 


85 


32 


88 


88 


87 


85 


50 


89 


89 


88 


86 


100 


90 


90 


89 


87 



SPECIFICATIONS FOR TURBO-GENERATING SETS. 1159 



Typical Results of Tests on Generating- Sets 
Supplied under Above Specifications. 



Size. 


100 
K.W. 


50 
K.W. 


32 
K.W. 


24 
K.W. 


Water consumption per K.W. hour ; 
Normal steam and vacuum lbs. 


29.8 


31.5 

29.7 

28.2 


35.0 
35.5 
35.6 


33.4 
34.0 
34.1 


Engine regulation % 
Full load to no load 
Normal steam and vacuum 


2.77 


1.35 

2.8 
2.66 


1.9 
2.9 
2. 


2.5 
2.9 
1.0 


Engine regulation % 
Full load to no load 
20% above normal steam with 
vacuum 




*2.65 


1.2 
1.96 

1.75 


2.4 
3.0 

2.65 


Engine regulation % 
Full load to no load 
20% below normal steam with 
vacuum 


' 2.8 


2.24 
3.17 

3.27 


2.5 
2.09 

2.67 


3.0 
3.6 

5.0 


Generator efficiency % 
Full load 


91.3 
91.7 


89.5 
89.1 
89.3 


88.8 
89.1 
88.8 


88.2 
88.6 
88.7 


Temperature rise in 
Armature coils 
By resistance, °C 


32.5 
33.3 


22. 

18. 
24.8 


20.8 

19. 

22. 


25.1 
20.1 
23.2 


Temperature rise in 
Field coils, shunt 
By resistance, °C 


29. 
31. 


24. 
24. 

30.7 


18.1 
26.7 

20.8 


19.2 
21.3 
19.0 


Temperature rise 

Commutator 

By thermometer, °C 


24. 

28. 


24.5 

23. 

19. 


13. 

14.5 

15. 


17. 
29. 
21. 



SPECIFICATIONS FOW TURBO-OE]¥ERATOG 

SETS. 

Each set to consist of an electric generator driven by a steam turbine, 
both mounted on a common bedplate. 

The set as a whole shall be as compact and light as is consistent with due 
regard to strength, durability, and efficiency. The maximum allowable 
normal speed, weight, and over-all dimensions are: 



Size in 
K.W. 


R.P.M. 


Weight 
in lbs. 


Length 
in inches. 


Max. width 

over pipe 

connections. 


Width in 
inches 
base. 


Height 

in 
inches. 


200 
300 


1700 
1500 


25,000 
29,000 


150 
165 


inches. 
100 
100 


75 
76 


87 
90 



The design shall provide for accessibility to all parts requiring inspec- 
tion during operation, or adjustment when under repair. Sets are to be 
designed to operate counter-clockwise when facing the steam inlet. The 
design to be preferably such that the same parts may be used in each, in 
order to avoid increase in number. 



1160 ELECTKICITY IN THE UNITED STATES NAVY. 



The sets must be capable of running without undue noise, excessive 
wear, or heating. Must be balanced and run true at all loads, up to 33$ 
per cent above rating; must be capable of running for long periods under 
full load. 

Cast or wrought-iron shall not be used for bearing surfaces. Both upper 
and lower halves of main bearings to be removable without removal or dis- 
placement of shaft. 

Suitable thrust bearings will be provided to prevent movement of the 
shaft in direction of its length as might be caused by rolling of the ship. 
Sets to be erected with shaft extending in a fore and aft direction. 

The combination bedplate to be a substantial casting, and provided with 
accurately spaced drilled holes for securing to foundation. Provision will 
be made to receive duct from the ship's ventilating system. 

Seats for all boltheads and nuts to be faced. All nuts to be case hardened 
and to be United States standard sizes. Where liable to work loose from 
vibration, nuts are to be secured by use of jam nuts and spring cotters. 
All bolt ends to be neatly finished. 

Adjoining portions of the machinery shall be given corresponding marks 
whenever this may be desirable for insuring correct assembling. 

Wrenches and lifting eyes to be furnished in sets as specified. 

Canvas covers to be furnished for each set, engine covers and generator 
covers to be separate. To be made of Navy standard G-ounce khaki cotton 
ravens (Specification 215) stitched together with a double seam. 

If required in advance of delivery of set, templates of the combination 
bedplate or of the shunt field rheostat shall be furnished by the contractor 
free of additional expense. These may be of paper, full size, with dimen- 
sions entered complete in order to obviate errors due to shrinkage or expan- 
sion. 

Interchangeability among the different sets and their spare parts of the 
same size and make as furnished in any one contract is required. This to 
be demonstrated as part of the final test for acceptance. 

Spare parts supplied to be boxed and protected in accordance with 
"Specification 3B2" issued by the Navy Department, September 12, 1906. 

The general appearance of the set resulting from design and workman- 
ship must be of the highest character. Any defect not caused by misuse 
or neglect, which may develop within the first six months of service, to be 
made good by and at the expense of the contractor. 

The works in which the construction of the contract is being carried on 
shall be open at all times during working hours to the inspection officer and 
his assistants. Every facility shall be liven such inspectors f ;r the proper 
execution of their work. 

Copies of the original shop drawings of the generating set shall be fur- 
nished as part of the contract as soon as possible after said contract is 
awarded. Before final acceptance of generating set a complete set of first- 
class detail and assembly drawings on tracing cloth shall be supplied. 

Turbine. 

The turbine will be of the horizontal multi-stage type. It will be de- 
signed to run condensing with maximum practical efficiency at all loads. 
It will be of sufficient power to drive the generator for an extended time at 
the rated speed when said generator is carrying 1£ *oad. 

The normal steam pressure under which the turbine will operate, and at 
this steam pressure the maximum steam consumption for various degrees 
of vacuum, is: 



Steam K.W 


. pressure, 


Water consumption per K.W. hour, full load. 




25 in. vac. 


26 in. vac. 


27 in. vac. 


28 in. vac. 


200 
300 


150 

200 




30£ 

28f 


28| 
26f 


27 
25* 



SPECIFICATIONS FOR TURBO-GENERATING SETS. 1161 



These rates should be interpreted as dry saturated steam, steam pres- 
sure being measured at throttle and vacuum in exhaust casing. Super- 
heating shall not be used in the test. 

The turbine to run smoothly and furnish the required power for full 
load at any steam pressure within 20 per cent (above or below) of those 
given in the table, and exhausting to condenser at 25 inches of vacuum; 
to furnish power for 90 per cent of full load at steam pressure 20 per cent 
below normal, and for full load at any steam pressure between normal and 
20 per cent above normal, when exhausting into the atmosphere. It will 
bear without injury the sudden throwing on or off of one and one-third 
times the rated load of the generator by making and breaking the gener- 
ator's external circuit. 

The steam outlets shall be so placed as to admit of piping from either 
side with equal facility. Blank flanges shall be furnished complete when 
required to cover alternative outlets, turbine to have exhaust outlet on 
right or left side as specified. All piping shall be firmly supported at; 
points close to the turbine, so that the weight of same shall not effect the 
alignment of the parts involved. 

Steam inlet valve shall be a combination throttle and emergency valve 
equipped with strainer intervening between valve and steam line. It will 
be connected to the emergency governor ia such a way that it will auto- 
matically close if the speed of the turbine rises more than 15 per cent above 
normal. Flange drilling to conform with specifications of the Bureau of 
Steam Engineering. 

The governor will be of the centrifugal type operating a series of valves. 

Lagging to be fitted as extensively as practicable to turbine. It shall be 
done after a preliminary run of the turbine in order that any defects in 
casting or joints may be readily found. The arrangement for securing the 
lagging in place shall admit of its ready removal, repair, and replacement. 

The speed variation will not exceed 2\ per cent when load is varied 
between full load to 20 per cent of full load gradually or in one step, turbine 
running with normal steam pressure and vacuum. A variation of not 
more than 3^ per cent will be allowed when full load is suddenly thrown 
on or off the generator with steam pressure constant between normal and 
20 per cent above normal, a variation of not more than Z\ per cent when 
90 per cent of full load is suddenly thrown on or off the generator with 
constant steam pressure at 20 per cent below normal, exhausting in both 
cases either into condenser or the atmosphere. No adjustment of the 
governor or throttle valve during the tests shall be necessary to insure 
proper performance under the above conditions. 

The turbines will operate without the use of lubricants in the steam 
spaces. Forced lubrication will be used on all bearings. The bedplate will 
contain an oil reservoir from which oil will be drawn by a pump operating 
directly from the main shaft, and forced through the system. To be pro- 
vided with a strainer which may be removed without interrupting the oil 
supply. The oil will be cooled by water which will pass through a coil 
around which the oil will circulate. 

Mandrels, with collars, complete, will be furnished for renewing the 
white metal of all bearings so fitted. 

The material and design of the turbine will be such as to safely withstand 
all strains induced by operation at the maximum steam pressure specified. 

Generator. 

To be of the direct current, multi-polar type, compound-wound long- 
shunt connection, designed to run at constant speed and to furnish a pres- 
sure of 125 volts at the terminals, at rated speed with load varying be- 
tween no load and one and one-third times rated load. 

The magnet frame will be circular in form; will have inwardly pro- 
jecting pole pieces and will be divided in half horizontally, the two halves 
being secured with bolts to allow the upper half with its pole pieces and 
coils to be lifted to provide for inspection or removal of armature. The 
pole pieces will be bolted to the frame. 

The magnet frame will be provided with two feet of ample size to insure 
a firm footing on the foundation. 

Facilities for vertical adjustment of the frame will be provided. 



1162 ELECTRICITY IN THE UNITED STATES NAVY. 



The laminations for the armature will be accurately punched from the 
best quality, thoroughly annealed, electrical sheet steel, slots to be punched 
in the periphery of laminations to receive armature windings. The lami- 
nations will be insulated from each other and will be assembled on the 
spider or shaft and securely keyed. Space blocks will be inserted between 
laminations at certain intervals to provide ventilating ducts for cooling the 
core and windings. 

Laminations will be set up under pressure and held securely by end 
flanges. 

The commutator bars will be supported on the shell which will be keyed 
directly on the shaft so that no relative motion can take place between the 
windings and bars. The bars will be of hard drawn copper finished accu- 
rately to gauge. The insulation between bars will be of carefully selected 
mica not less than .03 inch thick. The bars will line with the shaft 
and run true and will be securely held in place by means of clamping 
rings. 

The brushes will be of carbon. Each brush will be separately removable 
and adjustable without interfering with any of the others. The point of 
contact on the commutator will not shift by the wearing away of the brush. 

Brush holders to be staggered in order to even the wear over entire sur- 
face of commutator; the generator to be provided with some devices for 
shifting all the holders simultaneously. All insulating washers and bushings 
to be damp proof and unaffected by temperature up to 100 degrees C. 

Finished armature to be true and balanced both electrically and mechan- 
ically, that it may run smoothly and without vibration. The shaft to be 
provided with suitable means to prevent oil from bearings working along 
to armature. 

All copper wire to have a conductivity of not less than 98 per cent. 

For sets of 100 K.W. and less the shunt and series field coils to be sepa- 
rately wound and separately mounted on the pole pieces. The shunt and 
series coils, respectively, of any one set to be identical in construction and 
dimensions and to be readily removable from the pole pieces. The shunt 
coils as well as the series coils are to be connected in series. 

A headboard will be mounted on the generator containing the necessary 
terminals for main switchboard, equalizing connections, shunt and series 
field connections, and pilot lamp. 

The field rheostat to be of fire-proof construction suitable for mounting 
on back of switchboard, to be provided with handle or wheel projecting 
through to front, either directly connected or by sprocket chain, handle to 
be marked indicating direction of rotation for raising and for lowering volt- 
age of generator. The total range of adjustment, to be from 10 per cent 
above to 20 per cent below rated voltage, the variation to be not more than 
one-half volt per step at both full load and half load. 

Operation of Generator. 

The compounding to +>e such that with turbine working within specified 
limits, field rheostats and brushes in a fixed position, and starting with 
normal voltage at no load or at full load, if the current be varied step by 
step from no load to full load or from full load to no load, and back again, 
the difference between maximum observed voltage and minimum observed 
voltage shall not exceed 2£ volts. 

The compounding and heat run (full load and overload) of the generating 
sets must be made with identical brvrh positions. 

The dielectric strength for resistance to rupture shall be determined by 
a continued application of alternating E.M.F. of 1500 volts for one minute. 
Test for dielectric strength shall be made with the completely assembled 
apparatus and not with the individual parts, and the voltage shall be applied 
between the electric circuits and surrounding conducting material. 

With brushes in a fixed position there shall be no sparking when load is 
gradually increased or decreased between no load and full load; no detri- 
mental sparking when load is varied up to one and one-third times rated 
load, no flashing when one and one-third load is removed or applied in one 
stage. 

The iump in voltage must not exceed 15 per cent when full load is sud' 
clenly thrown on and off. 



SPECIFICATIONS FOR TURBO-GENERATING SETS. 1163 

The temperature rise of this set, after running continuously under full 
rated load with air of auxiliary ventilation at room temperature for four 
hours must not exceed the following: 

Degrees G. 

Armature, by thermometer 40 

Commutator, by thermometer 45 

Series field coils, thermometer 40 

Shunt field coils, resistance method 40 

Shunt rheostat, resistance method 75 

Series shunt, thermometer 40 

The rise in temperature to be referred to standard room temperature of 
25 degrees C. Room temperature to be measured by a thermometer placed 
three feet from commutator end of the generator with its bulb in line with 
the center of shaft. 

A system of air ducts for the ventilation of armature and commutator 
shall be provided. This system shall be connected to the ship's venti- 
lating system. The amount of air per minute required for the various 
sized sets will not exceed the following: 

Size K.W. Cubic feet air per minute. 

200 2000 

300 3000 

The generator to be capable of satisfactory operation for a period of two 
hours carrying one and one-third times its rated full load; also full load 
continuously in a room temperature of 30 degrees C, without auxiliary ven- 
tilating system, and no part shall heat to such a degree as to injure the 
insulation. 

Generators of the same size and manufacture to be capable of operation 
in parallel, the division of the load to be within 20 per cent throughout the 
range. The magnetic leakage at full load shall be imperceptible at a hori- 
zontal distance of 15 feet, measurements to be taken with a horizontal force 
instrument. 

The dynamo room is supplied by a special steam pipe which usually is so 
connected that it can take steam direct from any boiler or from the auxil- 
iary steam pipe, it passes into a steam separator from which branches lead 
to each of the genera ting-sets in the dynamo room. This separator is 
drained by a steam trap which sends the water back to the hot well in the 
main engine room. 

The exhaust pipe from each set joins a common exhaust which connects 
with the auxiliary exhaust service of the ship. If the sets are located 
below the level of the ship's auxiliary exhaust pipe, a separator is placed in 
the common exhaust pipe before it goes up and joins the ship's auxiliary 
exhaust. This separator is drained by a small steam pump, which is 
automatically started and stopped by means of a float in the body of the 
separator, which float starts the pump when the separator is full and stops 
it when empty. 

In the latest vessels a separate condenser is installed in the dynamo room 
for the generating sets. 

MVJTCHBOiHDS. 

Switchboards are divided into: 

(a) Generator boards. 
(6) Distribution boards. 

The generator boards are provided with two sets of bus-bars, one set for 
the lighting system, and the other set for the power system. The design is 
such that any of the generators can be operated singly or in parallel on 
either system. Fig. 1 shows diagrammatically the generator board used on 
the U. S. S. " Vermont." 

Current is supplied to the different appliances by means of distribution 
switchboards, wnich have two sets of bus-bars, one for lighting and one for 
power, and are connected directly to the corresponding bus-bars on the 
main generator board. Feeders run direct from these distribution boards, 



1164 ELECTRICITY IN THE UNITED STATES NAVY. 



each feeder being provided with a fused switch. Distribution boards are 
sometimes located at various parts of the ship and sometimes made con- 
tinuous with the main board. 

On several of the first vessels using electric turret turning gears on the 
Ward-Leonard system of control, a separate generator was used for each 
turret. This required an additional set of bus-bars on the generator switch- 



POWER FEEDERS 

" kotSTAIBtmOt 

^Bc/f/fo 



LIGHTJH6 FEEDERS 
TO 

vsTiuatnuA 

BOARD , 




- COffMW //EG. 



s EWUIER 



Generators 



NSA 



Fig. 1. Diagram of Vermont Generator Switchboard. 

board for each turret. Fig. 2 shows the design as used on the U. S. S. 
"Illinois," except there are four more generators connected on exactly like 
the four shown. Each generator has a headboard carrying a double-pole 
circuit breaker, and clips for a series field short circuiting shunt used for 
turret turning. The diagram shows generators Nos. 1 and 2 operating in 
parallel on the power system, No. 3 alone on the light system, and No. 4 
operating the after turret turning motors. It is to be noted that the three 
generators on the power and lighting systems have the right-hand blades of 
their triple pole field switches closed, giving self-excitation through the field 
rheostat, while the machine for turret turning has the middle blades closed, 

jving separate field excitation from the power bus-bars and through the 

>eld resistance attached to the controller in the turret. 



t 



SWITCHBOARDS. 



1165 




•siy Auvnixnv 



A 


r(I> 


1 S 

< »- H 

S uj CO 

Q tr > 
>. a: <o 

a = o 






W 


id 


<vffliD> 






3 




1166 ELECTRICITY IN THE UNITED STATES NAVY. 



DOIJBIE DYHrAlWEO UOOHS. 

Some of the latest ships have been designed with two complete generating 
plants each in a separate room, one forward and the other aft, so that any 




k0 J J L-o* 

I'ofd U Turret 



Fig. 3. Diagram of Double Dynamo Room Distribution. 

accident disabling one plant will not affect the fighting ability of the ship. 
Each plant is of sufficient capacity to carry the entire working load. 

The distribution is shown diagrammatically in Fig. 3. The generators in 
one room are controlled by the same board. The feeders to the various 



WIRING. 1167 



parts of the ship are supplied by the two distribution boards, one forward and 
one aft. Each of these distribution boards can take energy from either of 
the generator boards by means of transfer switches and interconnecting 
feeders. 

The circuits supplying the lights in the engine and fire rooms^ and the 
turret feeders are made double, one set running from each distribution 
board, and transfer switches provided at their ends; thus allowing these 
important parts to be supplied even if either dynamo room or either dis- 
tribution board is destroyed. 

1VIKOG. 
Specifications. 

The principal requirements of the Navy standard specifications for light 
and power conductors are : 

All conductors to be of soft-annealed pure copper wire, and, unless other- 
wise specified, each wire to be thoroughly and evenly tinned. 

All single strands must show a conductivity of not less than 98 per cent 
and the finished cable not less than 95 per cent of that of pure copper of 
the same number of circular mils. 

All layers of pure Para rubber must contain at least 98 per cent pure 
Para rubber; must be concentric, of uniform thickness, elastic, tough, and 
free from flaws and holes. 

All layers of vulcanized-rubber compound shall consist of the best grade 
of fine unrecovered Para rubber, mixed with sulphur and dry inorganic 
mineral matter only. The compound shall contain from 39 to 44 per cent, 
by weight, of fine Para rubber, and not more than 3 per cent, by weight, 
of sulphur. This sulphur shall be so combined with the Para rubber that 
not more than two-tenths of 1 per cent shall remain in the compound as 
free sulphur. The rubber shall be so compounded and vulcanized, that 
when test pieces taken from the wire (2 inches between jaws and £ inch 
wide when possible) are subjected to a tensile stress, they shall show a 
breaking strain of not less than 1,000 pounds per square inch, and shall 
stretch to at least three and one-half times their original length. The 
jaws will be separated at the rate of 3 inches per minute. 

When test pieces, as described above, are subjected to a stress of 900 
pounds per square inch for ten minutes, the compound shall be of such a 
character as to return to within 50 per cent in excess of its original length 
at the end of ten minutes after being released. 

All layers of vulcanized rubber must be concentric, continuous, and free 
from flaws or holes; must have a smooth surface and circular section; and 
must be made to a diameter in the finished conductor as tabulated. 

Measured dimensions "over vulcanized rubber " or "over tape" must 
come within 2\ per cent of tabulated values, the departure in no case to 
exceed ^ inch. 

All layers of cotton tape must be thoroughly filled with a rubber-insulating 
compound, the tape to be of a width best adapted to the diameter of that 
part of the conductor which it is intended to bind. The tape must lap 
about one-half its width; must be of such thickness as to make dimensions 
conform to tabulated values, and be so worked on as to insure a smooth 
surface and circular section of that part of the finished conductor which is 
beneath it. The tape must not adhere to the rubber. 

All exterior braid or braids must be closely woven, and all, except silk 
braid, must be thoroughly saturated with a black insulating waterproof 
compound which shall be neither injuriously affected by nor have injurious 
effect on the braid at a temperature of 95° C. (dry heat), or at any stage of 
the baking test, nor render the conductor less pliable. Wherever a di- 
ameter oyer outside braid is tabulated or specified, the outside surface must 
be sufficiently smooth to secure a neat working fit in a standard rubber 
gasket of that diameter for the purpose of making water-tight joints. 

Measured dimensions "over braid" must come within 5 per cent of 
tabulated values, the departure in no case to exceed ^ inch. 

All wire and cable shall be subjected to a test for continuity and for insu- 
lating properties, the latter by measurement of insulation resistance and by 
high potential test on the entire length of the cables, either or both, as per 
the following table: 



1168 ELECTRICITY IN THE UNITED STATES NAVY. 



t 


Insulation resistance. 


Test 
voltage, 
30 min- 
utes. 


Lighting wire. 

Up to and including: 

500,000 cm., single .... 

650,000 cm., single .... 

800,000 cm., single .... 

1,000,000 cm., single .... 
All twin wire: 

Between conductors .... 

From conductors to ground . 

Double conductor. 
Plain: 

Between conductors .... 

Each conductor to ground 
Diving: 

Between conductors .... 

Each conductor to ground 
Silk 


1,000 megohms per knot .... 
900 megohms per knot .... 
800 megohms per knot .... 
750 megohms per knot .... 

1,000 megohms per knot .... 
1,000 megohms per knot .... 

1,000 megohms per 1,000 feet . 
1,000 megohms per 1,000 feet . 

1,000 megohms per 1,000 feet . 
1,000 megohms per 1,000 feet . 
No test 


4,500 
4,500 
4,500 
4,500 

3,500 
3,500 

2,500 
3,500 

3,500 
3,500 
5,000 


Bell wire 


500 megohms per 1,000 feet . . 
No test 


1,500 


Bell cord 


5,000 


Cable. 

Interior-communication cable: 
Between conductors .... 
Each conductor to ground 

Night-signal cable; 

Conductor for 


1,000 megohms per 1,000 feet . 
1,000 megohms per 1,000 feet . 

1,000 megohms per 1,000 feet . 


1,500 
3,500 

3,500 


Completed cable: 

Between conductors .... 
Cable to ground 


1,000 megohms per 1,000 feet . 
50 megohms per length .... 


3,500 
3,500 



Tests for insulation resistance shall be made after immersion of wire 
(not less than three days after manufacture, the three days to be reckoned 
back from the end of the immersion period) in fresh water at a tempera- 
ture of 22° C. for a period of twenty-four hours, the test to be made by the 
direct-deflection method at a potential of 500 volts after five minutes 
electrification. 

High-potential tests shall then be made with the wire still immersed, the 
source of power supply to be a transformer of not less than 5 K.W. capacity. 
For double-conductor silk and bell cord the high-potential tests will be made 
with the dry wire freely suspended in the air. 

Six-inch samples of wire, with carefully paraffined ends, shall be sub- 
merged in fresh water of a temperature of 22° C. for a period of twenty- 
four hours. The weight of the wire before and after submersion, deduct- 
ing weight of copper and vulcanized rubber, will give the per cent of water 
absorbed by the braids. This shall not be more than 10 per cent. 

A sample of suitable length (1 foot long for small wires) shall be exposed 
for several hours at a time, alternately, to a temperature of 95° C. (dry 
heat) and the temperature of the atmosphere, over a period of three days. 
The braid and insulation must then stand sharp bending to a radius of seven 
times the diameter without breaking or cracking. For twin conductor the 
minimum diameter will be used. 

Unless otherwise called for, all wire supplies to be delivered in lengths of 
not less than 500 feet. To be delivered on reels of strong construction to 
admit of transportation to long distance, which reels on direct purchase? 
will remain the property of the Government. The flanges of the reels to be 



WIRING. 



1169 



at least 8 inches longer in diameter than the diameter through the coil. 
The loose end of the coil to be secured to prevent damage in transit. 

To insure maximum flexibility, the pitch of the "standing" or "spiral 
lay" of all conductors so formed shall not exceed values tabulated: 





Length of pitch, 
expressed in 


Number of wires 


forming strand. 


diameters of indi- 




vidual wires. 


7 


30 


19 


60 


37 


90 


61 


120 


91 


150 


127 


180 



When greater conducting area than that of 14 B. & S. G. is required, the 
conductor shall be stranded in a series of 7, 19, 37, 61, 91, 127, wires, or as 
may be specified, the strand consisting of one central wire, the remainder 
laid around it concentrically, each layer to be twisted in the opposite direc- 
tion from the preceding; and all single wires forming the strand must be 
of the diameter given in the American wire-gauge table as adopted by the 
American Institute of Electrical Engineers, October, 1893. 

Single Conductor. 

Table of Standard Dimensions: 





Actual 
C. M. 


^§ 
%™ 

S.S 
3 


N) • 

S3« 


Diameter, inches. 


Diameter in 32ds 
of an inch. 




Over 
copper. 


Over 

Para 

rubber. 




Approxi- 
mate C. M. 


Over 
vul- 
can- 
ized 
rub- 
ber. 


Over 
tape. 


Over 

braid. 


4,000 

9,000 

11,000 

15,000 

18,000 

20,000 

30,000 

40,000 

50,000 

60,000 

75,000 

100,000 

125,000 

150,000 

200,000 

250,000 

300,000 

375,000 

400,000 

500,000 

650,000 

800,000 

1,000,000 


4,107 

9,016 

11,368 

14,336 

18,081 

22,799 

30,856 

38,912 

49,077 

60,088 

75,776 

99,064 

124,928 

157,563 

198,677 

250,527 

296,387 

373,737 

413,639 

521,589 

657,606 

829,310 

1,045,718 


1 

7 

7 

7 

7 

7 

19 

19 

19 

37 

37 

61 

61 

61 

61 

61 

91 

91 

127 

127 

127 

127 

127 


14 
19 
18 
17 
16 
15 
18 
17 
16 
18 
17 
18 
17 
16 
15 
14 
15 
14 
15 
14 
13 
12 
11 


.06408 
. 10767 
.12090 
. 13578 
.15225 
.17121 
.20150 
.22630 
.25410 
.28210 
.31682 
.36270 
.40734 
.45738 
.51363 
.57672 
.62777 
.70488 
.74191 
.83304 
.93548 
1.05053 
1.17962 


.0953 
. 1389 
.1522 
.1670 
.1837 
.2025 
.2328 
.2576 
.2854 
.3134 
.3481 
.3940 
.4386 
.4885 
.5449 
.6080 
.6590 
.7361 
.7732 
.8643 
.9667 
1.0818 
1.2109 


7 
10 
10 
10 

11 

12 
12 
13 
14 
15 
16 
18 
19 
20 
22 
24 
26 
29 
30 
34 
38 
42 
46 


9 
12 
12 
12 
13 
14 
14 
15 
16 
17 
18 
20 
21 
22 
24 
26 
28 
31 
32 
36 
40 
44 
48 


11 
14 
14 
14 
15 
16 
16 
17 
18 
19 
20 
22 
23 
24 
26 
28 
30 
33 
34 
38 
42 
46 
50 



1170 ELECTRICITY IN THE UNITED STATES NAVY. 



All single- lighting conductors shall be insulated as follows: 

First. A layer of pure Para rubber, not less than 5 \ inch in thicknes*, 
rolled on. On the larger conductors this thickness must be increased, if 
necessary, to meet the requirements of paragraph 2 (m). 

Second. A layer of vulcanized rubber. 

Third. A layer of cotton tape. 

Fourth. A close braid to be made of No. 20 two-ply cotton thread, 
braided with three ends, for all conductors under 60,000 circular mils, and 
of No. 16 three-ply cotton thread, braided with four ends, for all conductors 
of and above 60,000 circular mils. The outside diameter over the braid 
to be in conformity with that tabulated. 



Twin Conductor. 

Table of Standard Dimensions: 





Actual 
CM. 


00 

o 

u 

O c3 


GO 

PQ 
.faO 


Diameter, 
inches. 


Diameter in 32ds of an inch. 


Ap- 




Over 


73 


Over tape. 


Over 1st 
braid. 


Over 2d 
braid. 


proxi- 












mate 
CM. 


Ob 


*o 


Over 
copper. 


Para 
rub- 
ber. 


> 3 


One 
con- 


Two 
con- 


One 
con- 


Two 
con- 


One 

con- 


Two 

con- 






3 
fc 


<0 




u * 


duc- 


duc- 


duc- 


duc- 


duc- 


duc- 






W 






> 

o 


tor. 
6 


tors. 
12 


tor. 
8 


tors. 
14 


tor. 
10 


tors. 


4,000 


4,107 


1 


14 


.06408 


.092 


5 


15 


9,000 


9,016 


7 


19 


. 10767 


.139 


7 


9 


18 


11 


20 


13 


21 


11,000 


11,368 


7 


18 


.12090 


.156 


8 


10 


20 


12 


22 


14 


23 


15,000 


14,336 


7 


17 


.13578 


.172 


8 


10 


20 


12 


22 


14 


23 


18,000 


18,081 


7 


16 


. 15225 


.190 


9 


11 


22 


13 


24 


15 


25 


20,000 


22,799 


7 


15 


.17121 


.209 


10 


12 


24 


14 


26 


16 


27 


30,000 


30,856 


19 


18 


.20150 


.243 


11 


13 


26 


15 


28 


17 


29 


40,000 


38,912 


19 


17 


.22630 


.268 


12 


14 


28 


16 


30 


18 


31 


50,000 


49,077 


19 


16 


.25410 


.298 


13 


15 


30 


17 


32 


19 


33 


60,000 


60,088 


37 


18 


.28210 


.327 


14 


16 


32 


18 


34 


20 


35 



All twin lighting conductors shall consist of two conductors, each one of 
which shall be insulated as follows: 

First. A layer of pure Para rubber, not less than ^ of an inch in thick- 
ness, rolled on. 

Second. A layer of vulcanized rubber. 

Third. A layer of cotton tape. 

Two such insulated conductors shall be laid together, the interstices being 
filled with jute, and covered with two layers of close braid. 

Each braid to be made of No. 20 two-ply cotton thread, braided with 
three ends. 

Methods of Installing* Conductors. 

Three methods of installing conductors are used. 

1. Conduit ; 2. Molding ; and 3. Porcelain supports. 

1. Conduit is the principal method, being used in almost all spaces below 
the protective deck, and wherever wiring is exposed to mechanical injury 
or the weather. Iron-armored conduit is used, except within 12 feet of the 
standard compass, where brass is used. 

Conduit passing through water-tight bulkheads is made water-tight by 
means of stuffing-boxes and hemp-packing. Water-tightness is provided 
at the ends of conduit by a stuffing-box and a soft-rubber gasket, through 
which the conductor passes. Long lines of conduit passing through several 



LIGHTING-SYSTEM. 1171 

water-tight compartments are provided with gland couplings at proper 
intervals, which divide the run into water-tight sections, thus preventing 
an injury in a flooded compartment from allowing the water to run through 
the conduit into another compartment. These gland couplings are also 
used where conduit passes vertically through decks. 

2. Wood molding is used in living spaces but has been abandoned on 
the latest vessels. It consists of a backing piece fastened to the iron work 
of the ship, to which the molding proper is secured by screws and covered 
with a wooden capping-piece. Where leads installed in molding pass 
through water-tight bulkheads, a bulkhead stuffing-box is provided for 
water-tightness. 

3. Porcelain supports are used in dynamo rooms and for the long feeders 
which are run in the wing passages where there is no danger of interference. 
Stuffing-tubes are used where the wires pass through bulkheads, the same 
as with molding. 

Junction Boxes. 

All conductors are branched by being run into standard junction boxes, 
which are usually provided with fuses. Where conduit is used these boxes 
are tapped, to have the conduit screwed into them ; where molding or 
porcelain is used the boxes are provided with stuffing-tubes. The box covers 
are made water-tight with rubber gaskets ; inside the fuses and connection 
strips are mounted on porcelain bases. 

IIGHTI^f;.§l§TE^, 

Wiring". 

The maximum drop allowed on any main is 3 per cent at the farthest 
lamp. Mains are required to be of the same size throughout, and to be of 
1,000 circular mils per ampere of normal load. 

fixtures. 

Most incandescent lamps are installed in air-tight glass globes of different 
shapes, depending upon position or location. Magazines are lighted by 
"Magazine Light Boxes," which are water-tight metal boxes set into the 
magazines through one of its walls, and provided with a water-tight door 
opening into the adjacent compartment, so that the interior of the box is 
accessible without entering the magazine. The sides of the boxes have 
glass windows, and each box is fitted with two incandescent lamps, each 
lamp having its own separate fused branch to the main, so that one lamp 
can be used as a spare. 

" Switch Receptacles " containing a snap switch and a plug socket are 
provided for attaching portable lamps. 

lamps, 

The principal requirements of the standard Navy specifications are : 

Unit of Candle-Power. — The unit of candle-power shall be the 
candle as determined by the Bureau of Standards at Washington, D. C. 

Photometric Measure. — The basis of comparison of all lamps shall 
be the same spherical candle-power. The normal candle-power referred to 
in these specifications shall be the mean horizontal candle-power of lamps 
having a mean spherical candle-power value of 82.5 per cent of the mean 
horizontal candle-power, which is the standard value for filaments of the 
oval anchored type. 

For lamps having filaments giving a different ratio of mean spherical to 
mean horizontal candle-power, the horizontal candle-power measurement 
will be corrected by a reduction factor determined by the Bureau of Stand- 
ards or other authority mutually agreed upon. 

Vest Quantity. — The test quantity shall consist of 10 per cent or 
more of any lot or package, and in no case be less than ten lamps. 



1172 ELECTRICITY IN THE UNITED STATES NAVY. 



From each package there will be selected at random, the test quantity for 
the purpose of determining the mechanical and physical characteristics of 
the lamps, the individual limits of candle-power and watts per lamp, and 
finally the life and candle-power maintenance. These lamps will be known 
as the test lamps. 

All lamps shall conform to the manufacturers' standard shapes and sizes 
of bulbs, and to the standard forms of filament, and the standard candle- 
power and watts per lamp. 

All bulbs shall be uniform in size and shape, clear, clean, and free from 
flaws and blemishes. 

All lamps, unless otherwise specified, shall be fitted with the standard 
Edison scre.7 base, fitted with glass buttons, forming the insulation between 
contacts, and rendered impervious to moisture. The shells of the bases 
shall be of good quality brass, firmly and accurately fitted to the bulb with 
moisture-proof cement, and in length to conform to the National Electric 
Code of Fire Underwriters. 

The lamp filament must be symmetrically disposed in the bulb and shall 
ixOi, droop excessively during the life of the lamp when the lamp is burned on 
test in the one horizontal position at a voltage corresponding to an initial 
specific consumption of 3.76 watts per mean spherical candle and without 
excessive vibration. 

All filaments must be uniform and free from all imperfections, spots, and 
discolorations. 

Leading in wires must be fused into the glass with the joints between cop- 
per and platinum wires bedded well within the glass; the wires to be straight, 
well separated, and securely soldered to the base and cap, without excess of 
solder and so threads of base are free from solder. 

All lamps must have first-class vacuum, showing the characteristic glow 
of good vacuum when tested on an induction coil. 

A printed label, showing manufacturer's name or trade-mark, voltage, 
and candle-power, must be placed on each lamp near base. 

The lamps must be well made and free from all defects and imperfections, 
so as to satisfactorily meet the conditions of the lighting service. 

If 10 per cent of the test quantity of lamps selected from any package 
show any physical defects incompatible with good workmanship, good ser- 
vice, or v.dth any clause of these specifications, the entire lot from which 
these lamps were selected may be rejected without further tests when tests 
are made at the lamp factory. When the tests are made elsewhere, if the 
first test quantity prove unacceptable, 20 per cent more lamps will be 
selected from the package or lot of lamps, and should 10 per cent of this 
second lot of sample lamps be found to have any of the physical defects 
above mentioned, the entire lot from which these lamps were selected may be 
rejected without further test. 

When tested at rated voltage the test lamps shall not exceed the limits 
,_ven in schedule. If 10 per cent of test lamps from any package is found to 
Jail beyond the limits stated, when tests are made at the lamp factory the 
entire lot from which these lamps were selected may be rejected without 
further test. When tests are made elsewhere, if the first test quantity 
prove unacceptable, 20 per cent more lamps will be selected from the package 
or lot of lamps, and should 10 per cent of these additional lamps be found 
to fall beyond the limits the entire package may be rejected without further 

Life tests shall be made as follows: From each accepted package of 
lamps two sample lamps shall be selected which approximate most closely 
to the average of the test quantity. One of the two lamps thus selected will 
be subjected to a life test and designated as the life test lamp, the second 
or duplicate lamp being reserved to replace this test lamp in case of acci- 
dental breakage or damage during the life test. The test lamps shall be 
operated for candle-power performance at constant potential, average 
variations of voltage not to exceed one-fourth of 1 per cent either side. 
The voltage for each lamp shall be that corresponding to an initial specific 
consumption of 3.76 watts per mean spherical candle, or if tested upon a diff- 
erent basis, the results shall be corrected to a basis of 3.76 watts per mean 
spherical candle. If desired, the life tests may be made at such other watts 
per candle as may be mutually agreed upon. ■ ; 

Readings for candle-power and wattage shall be taken dunng life at the 
marked voltage of the lamps at approximately fifty hours, and at least 



£ 



LIGHTING-SYSTEM. 1173 

every one hundred hours afterwards until the candle-power shall have fallen 
20 per cent below the initial candle-power, or until the lamp breaks, if within 
that period. The number of hours the lamp burns until the candle-power 
has decreased to 80 per cent of its initial value, or until the lamp breaks, is 
known as the useful or effective life. 

The average candle-power of lamps during life shall not be less than 91 
per cent of their initial candle-power. In computing the results of test of 
a lot of lamps the average candle-power during life shall be taken as the 
arithmetical mean of the values for the individual lamps of the lot tested. 

Lamps selected for the life test, which for any reason do not start on 
such test, shall be replaced by others. 

Lamps which are accidentally broken but are burned out on test shall not 
be counted to diminish the average performance. 

In case both test and duplicate lamps are broken or damaged before the 
life test is completed, the average performance of all lamps of the same class 
previously determined under the same contract shall be assigned to the 
package represented. 

On all tests for determining average candle-power and life each 
package which will be affected by the results of test shall have at least one 
lamp on such test. 

Accurate recording voltmeter records will be obtained during the test 
on lamps to show the average variation on the circuit. 

When so tested the lamps shall average at least the values for useful life 
given in the tables on pages 1176 to 1178. 

(a) Values for Oval Anchored Plain Standard l-ig-liting" 

Stamps. 

Lamps of this type of voltages 105 and below, at 110, 120, and above, and 
also at 220, may have double the limits of variation in the initial limits 
specified for their respective classes. 

Lamps and other types of filaments to give equivalent performances. 

For lamps between 120 and 125 volts, the useful life values shall be 95 
per cent of those given in the table, and for lamps between 126 and 130 volts 
the useful life values shall be 90 per cent of those given in the table. 

(b) Values for Round Bull*. Tubular, and other Irregular 
Types of Lamps. 

The individual limits for irregular types of lamps, such as round bulb 
and tubular lamps, shall be twice the individual limits given in the body 
of the preceding schedules for regular lamps of corresponding candle-power. 

The individual limits for metallized filament and round bulbs primo types 
of lamps shall be 15 per cent above and 15 per cent below the mean candle- 
power rating, and 15 per cent above and 15 per cent below the mean total 
watt rating. The candle-power ratings referred to are the mean horizontal 
candle-power ratings of clear lamps without reflectors. 

(c) Navy Special lamps. 

All lamps must conform in their general shape and form to drawing No. 
7219-C, see Figs. 4 and 4a, and overall dimensions must not be exceeded. 

Rejections and Penalties. 

The failure of the lamps in any package to conform to the specifications 
as to mechanical and physical characteristics, or to initial limits, may cause 
the rejection of the entire package. 

The failure of the lamps to give within 90 per cent of the values of useful 
life given in the tables may cause the cancellation of the contract. 

Lamps which have not been used and are rejected under the terms of these 
specifications will be returned to the manufacturer at his expense, and no 
payment will be made tharefor. 

Prompt notice will be served upon the contractor of the test results on 
lamps that are rejected, or that fail to meet the specified requirements. 



1174 ELECTRICITY IN THE UNITED STATES NAVT. 



t&LfjB. Diving LAMP Jf AM 3Z <;.* LAfifPf 




Fig. 4. Standard Incandescent Lamps as Covered by U. S. 
Navy Specifications. 



LIGHTING-SYSTEM. 



1175 






INSTRUMENT 




f^\ 



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11-3 



f 



J 



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•3Z 



y<o 



Torpedo 
lamp 



INSTRUMENT 
LAMP 




Fig. 4a. 



Standard Incandescent Lamps as Covered by U. S. 
Navy Specifications. 



1176 electricity in the united states navy. 



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1178 ELECTRICITY IN THE UNITED STATES NAVY. 



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LIGHTING-SYSTEM. 1179 



I>ivi ner- T.an tern*. 

Diving-lanterns consist of a glass cylinder closed at each end with a metal 
cap, having the joint between the glass and metal packed with a soft-rubber 
gasket. On the inside of one of the caps is provided a standard marine 
lamp-socket for 150 candle-power incandescent lamp, to which is connected 
100 feet of twin conductor cable, at the other end of which is connected a 
double pole plug for a standard marine receptacle. 

When first submerged a considerable amount of moisture is deposited in 
the inside, which is drawn out through a small hole made water-tight by a 
screw with a rubber gasket. 

Sea re hi is; lit*. 

The requirements of the standard Navy specifications are : 

It shall, in general, consist of a fixed pedestal or base, surmounted by a 
turntable carrying a drum. The base shall contain the turning mechanism 
and the electric connections, and be so arranged that it can be bolted 
securely to a deck or platform. 

The turntable to be so designed that it can be revolved in a horizontal 
plane freely and indefinitely in either direction. 

The drum to be trunnioned on two arms bolted to the turntable, so as to 
have a free movement in a vertical plane, and to contain the lamp and re- 
flecting mirror. The drum to be rotated on its trunnions. The axis of the 
drum to be capable of a movement of not less than 70° above and 30° below 
the horizontal. 

The drum to be thoroughly ventilated and well-balanced ; to be fitted with 
peep sights for observing the arc in two planes, and with hand holes to give 
access to the lamp. It must be so designed that a parabolic mirror can be 
used, and means for balancing it must be provided. 

The mirror to be made of glass of the best quality, free from flaws and 
holes, and having its surface ground to exact dimensions, perfectly smooth 
and highly polished. Its back to be silvered in the most durable manner ; 
the silvering to be unaffected by heat. To be mounted in a separate metal 
frame lined with a non-conducting material, in such a manner as to allow 
for expansion due to heat and to prevent injury to it from concussion. 

The lamp to be of the horizontal carbon type, and designed for both hand 
and automatic feed. The feeding of the carbons must be effected by a posi- 
tive mechanical action, and not by spring or gravitation. It must burn 
quietly and steadily on a 125-volt circuit in series with a regulating rheostat, 
and shall be capable of burning for about six hours without renewing the 
carbons. 

The front of the drum to be provided with a glass door composed of strips 
of clear plate glass. The door to be so arranged that it can be put in place 
on the drum easily and quickly. 

Electrically Controlled .Projector. 

To be in all respects similar to the hand controlled, with the addition of 
two shunt motors, each with a train of gears ; one motor for giving the ver- 
tical and the other the horizontal movement of the projector. The motors 
and gears to be contained in the fixed base, and to be well protected from 
moisture and mechanical injury. A means to be provided for quickly 
throwing out or in the motor gears, so that the projector can be operated 
either by hand or by motor, as desired. 

The motors to be operated by means of a compact, light, and water-tight 
controller, which^can be located in any desired position away from the pro- 
jector. The design of the controller to be such that the movement of a 
single handle or lever, in the direction it is wished to cause the beam of 
light to move, will cause the current to flow through the proper motor in the 
proper direction to produce such movement. The rapidity of movement of 
the projector to be governed by the extent of the throw of the handle or 
lever. A suitable device to be included whereby the movement of the pro- 
jector can be instantly arrested when so desired. 

All projectors to be finished in a dead-black color throughout, excepting 
the working-parts, which shall be bright. 



1180 ELECTRICITY IX THE UNITED STATES NAVY, 




SIGNAL LIGHTS. 1181 

The lamps to be designed to produce the best results when taking current 
as follows : 18-inch, 30 to 35 amperes ; 24-inch, 40 to 50 amperes ; 30-inch, 
70 to 80 amperes. 

The 18-inch projector shall project a beam of light of sufficient density to 
render plainly discernible, on a clear, dark night, a light-colored object 10 
by 20 feet in size, at a distance of not less than 4,000 yards ; the 24-inch pro- 
jector, at a distance of not less than 5,000 yards ; and the 30-inch projector, 
at a distance of not less than 6,000 yards. 

The connections for the electrically controlled projectors as manufactured 
by the General Electric Company are shown in the diagram, Fig. 5. The 
fields of the two training motors are in series with each other and connected 
across the 125-volt circuit. Both horizontal and vertical training can be 
simultaneously produced. The controller-handle when released, is brought 
to the otf position by springs and short circuits, both motor armatures thus 
stopping all movement. 

The horizontal training motor drives through a worm gear, and the verti- 
cal motor through a revolving nut on a vertical screw shaft : all gearing 
can be easily thrown out for quick hand control. 

The highest speeds are 360° in 30 seconds horizontally, and 100° in 60 
seconds vertically. The motors may also be operated at four lower speeds. 

The lamp has a striking magnet in series with the arc and feeding 
magnet in shunt with the arc. When the arc becomes too long, sufficient 
current is forced through the shunt feeding magnet to cause it to make its 
armature vibrate back and forth, and thus move the carbons together 
through a ratchet which turns the feed screws. The point at which the 
magnet will begin to feed is adjustable by means of a spring attached to 
armature. The feed screws are so proportioned that the positive and 
negative carbons are each fed together at the same rate that they are con- 
sumed, thus keeping the arc always in the focus of the mirror. Sight 
holes are provided through which the arc may be watched. A permanent 
magnet, fastened to the inside of the projector and surrounding the arc on 
all sides but the top, causes the arc to burn steadily near the upper edge 
of the carbons and in focus with the mirror. 

The rheostat is located near the switchboard, and after being once set 
for proper working does not need to be again changed. Double-pole circuit 
breakers are used at the switchboards for switches. 

§ia\AL IIOHT§. 
Ardois Sig-nals. 

The Ardois signals consist of four double lanterns, each containing a red 
and a white light, which are hung from the top of the mast, one under the 
other and several feet apart. By means of a special controller any number 
of lanterns may have either their red or white lamps lighted, thus produc- 
ing combinations by which any code can be signaled. The lamps used are 
clear, and the color is produced by having the upper lens which forms the 
body of the lantern colored red ; the lower lens is clear. 

The controller consists of eight semi-circular plates, with pieces of hard 
rubber set in the inner edges where needed, and a rotating center s£ud 
with eight plunger contacts rubbing on the edges of the plates. By suitably 
placing the pieces of hard rubber for any given position of the contacts, 
any desired combination of lights can be produced. 

The operation consists in moving the arm carrying the contacts to the 
position desired (as shown by a pointer on an indicating dial) and closing 
the operating switch, when the proper lamps will light. 

A later design is provided with a typewriter keyboard, the depression of 
any key making the proper contacts to light the lamps giving the combina- 
tion corresponding to the character on the key. 

Track lights. 

The truck lights are lanterns of construction similar to the Ardois 
lanterns," mounted, one on the top of both the fore and main masts. By 
means of a special controller the red or white light in either lantern can be 
lighted. 



1182 ELECTRICITY IN THE UNITED STATES NAVY. 




PILOT LAMP 

Fig. 6. Diagram of Ardois Signal Set. 



POWER SYSTEM. 1183 



POWER SYSTEM, 

Motors are kept entirely separate from lights by the use of different bus- 
bars on the generator switchboard and distribution boards. Each motor or 
group of motors is supplied by its own feeder running from the distribution 
board, where it has its own fused switch. A maximum drop of 5 per cent 
is allowed. 

Principal Requirements of Specifications for Motors. 

Motors to be wound for 120 volts, direct current, for both armature and 
field windings, unless otherwise specified, and to be either series, shunt or 
compound wound, according to work they are to perform. 

In sizes above 4 horse-power, motors to be multipolar; 4 horse-power or 
below may be bipolar. Motors to be as compact and light as possible, con- 
sistent with strength and efficiency. The method of running wires to 
motors to be in all cases by tapping conduit directly into the motor frames 
or into connection boxes attached to frames, as may be specified in each 
individual case; connection boxes for enclosed motors to be water-tight. 

Enclosed motors should be provided with openings of sufficient size and 
number to give easy access to brush rigging, commutator, and field coils; 
such openings to be provided with covers and fastenings of approved design. 
The contact surfaces between these covers and motor frame should be flat 
machined surfaces, provided with rubber gaskets. Rubber gaskets for all 
water-tight work to be in accordance with the Navy standard specifications 
for the same as issued by the Bureau of Supplies and Accounts. All en- 
closed motors to be provided with drain plugs or cocks which will thoroughly 
drain out any water that may enter the motor casing. 

The armature shaft to be of steel and strong enough to resist appreciable 
bending under any condition of overload, to have sufficient bearing surface 
and to be efficiently lubricated by grease or self-oiling bearings, or sight- 
feed oil cups, as occasion may require. Oil cups to be of size to afford 
lubrication for at least eight hours. A satisfactory arrangement to be made 
to prevent oil from running along the shaft or being spilled. Visual oil 
gauges to be provided for determining the amount of oil in pocket and 
drains for drawing oil prior to renewal. 

To prevent deterioration from rust and corrosion, bolts for end brackets, 
all bolts and pins one-half inch diameter or less not in the magnetic circuit 
and such nuts and other special fittings as the Bureau may direct, will be of 
noncorrosive metal, rolled bronze or its equivalent. 

All electrical connections to be designed with special reference to the pre- 
vention of their becoming loose from vibration or shock. All connections 
liable to become loose by vibration are to be provided with approved efficient 
locking devices. 

All connecting pieces and other current-carrying parts to be so propor- 
tioned that no undue heating will occur when they are worked under the 
severest possible conditions. 

All the field poles to be equally energized. In compound motors, series 
and shunt windings to be separate. The windings of armature and field to 
be well protected from mechanical injury, and to be painted with water- 
excluding material not soluble in oil or grease. No insulating substances 
to be used that can be injured by a temperature of 100 degrees C. 

The armature to be of the ironclad type, built up of thin laminated disks 
of soft iron or steel of the very best quality, having the spaces between the 
teeth punched out of each separate disk and not milled after assembly. 

The disks to be properly insulated from each other. The coils to be pref- 
erably of the removable type, and to be retained in slots of the armature 
body by maple wedges running full length of armature, or other approved 
method. No more than three band wires under poles will be accepted. 
Band wires must be of nonmagnetic material. The armature to be electri- 
cally and mechanically balanced. The winding at pulley end to be pro- 
tected from oil in an approved manner. The commutator segments to be 
of pure copper, hard-drawn or drop-forged and tempered. The segments to 
be of ample depth and insulated from each other and the shell by pure mica 
of such quality as to secure even wear with the copper. 



1184 ELECTRICITY IN THE UNITED STATES NAVY. 

Brushes to be of carbon; current density in brushes must always be 
given and should be in accordance with the best practice. Special atten- 
tion must be given to the selection of brushes, that their material may be 
homogeneous and the quality such as to give perfect commutation without 
cutting, scratching, or smearing the commutator. Brush holders to be 
readily accessible for adjustment and renewal of brushes and springs; to be 
entirely of noncorrosive metal and of the sliding shunt-socket type, in which 
the brush slides in the holder and is provided with a flexible connection 
between brush and holder. The springs are to be phosphor-bronze and 
shall not be depended on to carry current. Brush holders on all motors to 
be adjustable for tension, and on motors of five-horse-power and above to 
be adjustable for tension without tools, and so constructed as to permit of 
proper staggering of brushes. Brush holders for nonreversible motors of 
five-horse-power and above to be simultaneously adjustable for position, 
Proper position of rocker arm to be plainly marked. This position for 
reversible motors to give same speed in either direction. 



Tests. 

Contractors are required to afford facilities for inspection of apparatus 
during manufacture, if required. 

Individual motors or small lots will be tested at the point of delivery, but 
all large lots of materials to be shipped to distant points will be tested at the 
works of the manufacturer. The contractor will provide all facilities, and 
have all the required tests made in the presence of an authorized inspector. 

The contractor will present a certified record of such tests with the deliv- 
ery. The tests to cover the following points: 

(a) Adjustment and JFit of I*arts. — The inspector to see that the 
materials and workmanship of all parts of the machine are of the best 
quality and satisfactory in every respect. 

(6) Mechanical Strength. — The base, bearings, shaft armature, field 
magnets, and other main parts should not spring with any reasonable force 
that may be applied to them. The strength to resist strains due to cen- 
trifugal force to be tested by running armature without load for 30 minutes 
at double its rated speed for shunt motors and four times full load speed 
for series motors. 

(c) Balance, — The perfection of balance of the armature to be tested 
by running the motor at its normal speed, at which speed the motor must 
not show the slightest vibration. 

(d) l¥oise. — The motor to run at its full-rated speed and load without 
noise. 

(e) Sparking*. — Open motors to run without sparking from no load to 
full load without shifting the brushes and under all conditions of full and 
weak field when field regulation is used. Enclosed motors to 25 per cent 
overload. 

(/) Variation of Speed. — For shunt- wound motors the variation in 
speed from no load to full load shall not be more than 12 per cent in motors 
of less than five-horse-power and not more than 9 per cent in motors of five- 
horse-power and above. Series and compound wound motors to make at 
rated outputs their rated speeds. The motor should be designed to obtain 
its rated speed when hot, with atmospheric temperature of approximately 
25 degrees C, and the speed actually obtained on test at the end of the 
heat run must be within 4 per cent of the rated. The variation in speed 
due to heating shall not exceed 10 per cent- 
er) [Dielectric Strength. — The test for dielectric strength to be made 
with a pressure of 1,500 volts alternating E.M.F. for 60 seconds, tested with 
a generator or transformer of at least 5-kilowatt capacity. The insulation 
resistance between windings and frame to be at least one megohm measured 
with 500 volts direct current. 

(h) Heating*. — The rise of temperature of the field windings above the 
surrounding air is to be measured by the resistance method according to 
the rules and coefficients adopted by the American Institute of Electrical 
Engineers, appended. The rise of temperature of all other parts to be by 
thermometer. The temperature of the room is to be read from thermo- 
meters, conditions of ventilation being normal. 



POWER SYSTEM. 1185 

The following are the maximum temperature rises allowed: 

'■}.) Open-type motors designed for continuous work, eight hours' run 
with a rise of — 

Commutator, 40 degrees C. 
Field winding, 40 degrees C. 
All other parts, 35 degrees C. 
(ii) Enclosed motors designed for continuous work, eight hours' run 
with a rise of — 

Commutator, 50 degrees C. 
Field winding, 50 degrees C. 
All other parts, 45 degrees C. 
(iii) Intermittent-running motors will have heating limit and length of 
heat-run separately specified for each case. 

The temperature rise of bearings shall in no case exceed 35 degrees C. 

(i) Efficiency. — Motors must have the highest commercial efficiency 
for their size and speed. Each contractor must state weight and efficiency 
of motors at one-quarter, one-half, three-quarters, and full load. Prefer- 
ence will be given to lightest weight and best efficiency consistent with 
good design and the specific requirements. When thorough reliability and 
freedom from danger of breakdown are the prime requisites, as for turret- 
turning motors, boat-crane motors, etc., the maximum efficiency will not 
be insisted on. 

(k) JLul»i*icati©n. — The inspector will see that oil cups and wells of 
the specified capacity are provided and that all the necessary provisions 
are made for the supply and drainage of oil without injury to the electrical 
parts. 

Electric brakes, solenoids, etc., to stand the same heat and insulation 
test as the apparatus to which they are attached. All spare parts to be 
subjected to the same tests as originals. 

Most intermittent running motors, such as boat crane, deck winch, turret 
turning, etc., have the following heat tests: 

Each motor shall be tested at the works of the maker by running for a 
continuous period of one hour at 120 volts at its rated output and speed, 
without increasing the temperature of the series field windings more than 
70 degrees C, the shunt field windings 50 degrees C, the commutator 65 
degrees C, the armature or any other part 60 degrees C. above the sur- 
rounding air. 

Principal Requirements for Controlling- Panels. 

Controlling panels for installation in locations not exposed to the action 
of water outside of ammunition passages, handling rooms, etc., where 
powder is handled, may be of the nonflame-proof type, in accordance with 
the following specifications: 

The panel to consist of a suitable insulating slate base with black polish 
finish, carrying a double pole main-line knife switch with enclosed indicating 
fuses, a starting arm with automatic no-voltage release and overload cir- 
cuit breaker and the necessary resistances mounted at the back. A double 
pole circuit breaker with independently operating arms may be substi- 
tuted for the line switch if desired. On panels where speed control by 
field resistance is required, suitable rheostat connections are to be pro- 
vided, giving ample number of steps to secure smooth control and accurate 
adjustment, and* must be a separate multipoint switch so arranged that 
the motor cannot be started on weak field. On panels where speed con- 
trol by armature resistance is required, the starting arm must be so con- 
structed that it will stay only on the contacts designed for continuous 
running. 

For motors requiring more than 60 amperes of current, the starting arm 
must not be relied upon to carry the current in the running position. The 
starting resistance must not be left in series with the field on the running 
position ; connections to be such that there shall be no disruptive discharge 
of the field on opening the circuit, either by opening the main-line switch, 
or by forcing the starting arm to the off position, and provision to be made 
to prevent arcing on the initial starting contact. Panel to be so connected 
that it shall be impossible to have full voltage on the field with the starting 



1186 ELECTRICITY IN THE UNITED STATES NAVY. 

arm in the off position. Care should be taken in the design of the pinel 
to see that there is no interference between operating parts, such sa line 
switch, when opened, and starting arm. All magnet coils and all contact 
parts carrying currents must be renewable from the face of the panot with- 
out disturbing any of the rear connections. Panel to be mounted on a 
rigid box metal frame, with the top and bottom of solid sheet metal and 
the sides (if so desired) of perforated metal, which must extend the length 
and breadth of the slate and which must protect the connections and parts 
back of the panel; suitable lugs or extensions to be provided for support- 
ing the frame. Hinged doors with composition lock and duplicate keys 
shall be provided over the face of the panel. No part on the face of the 
panel is to project beyond the edge of the panel. 

The automatic no-voltage release must operate and either bring the 
starting arm to the off position or open the circuit breaker upon failure of 
voltage. The winding of the no-voltage release magnet must not be 
put in series with either the field winding or armature resistance. The 
automatic overload release must be of the nature of an ordinary spring 
operated circuit breaker, having the release mechanism operated by a posi- 
tive hammer blow, delivered by a core or armature moved against the 
action of gravity, and must have its own independent contacts for opening 
the armature circuit; and it should open the circuit in case of overload 
under any condition, i.e., during ordinary running, during the act of start- 
ing the motor, or if the starting arm should become struck on any starting 
point and the current then switched on from the outside. For motors 
having a rated full load current of 50 amperes or less, the overload release 
may be of the interlocking type, in which case it must be so interconnected 
with the starting arm that it cannot be closed with the starting arm in 
any but the off position. For motors requiring more than 50 amperes, a 
single or double pole circuit breaker entirely separate from the starting 
arm must be used. An overload device which operates by short-circuiting 
or opening the circuit of the retaining magnet of the no- voltage release will 
under no conditions be accepted. The overload device is to be provided 
with renewable arcing contacts of carbon, to be adjustable and provided 
with a scale graduated from normal current to 100 per cent overload to 
facilitate adjustment to the desired number of amperes, and to be able to 
carry a current of 50 per cent in excess of the rated full-load motor current 
continuously without undue heating. The tripping device must be able to 
withstand severe shock without opening. 

The insulating material used on the panel must be noncombustible, non- 
absorbent, and not damageable by moisture or by heating to a tempera- 
ture of 150 degrees C. The frame of the panel is to be insulated from the 
hull of the ship. All panels are to pass the same dielectric and insulation 
tests as the motors for which they are supplied. 

All windings of magnet coils are to be run through an insulating varnish 
and the outside or the coils to be well varnished and taped. When continu- 
ously in circuit, the temperature rise of these coils must not be more 
than 40 degrees C. above surrounding atmosphere, measured by ther- 
mometer placed on the coil. 

The main operating springs for the no-voltage release and the overload 
circuit breaker must be amply strong to prevent any sticking after the 
appliance has become worn or roughened. All flat springs are to be of 
phosphor-bronze and all helical springs of copper-plated steel. All con- 
tacts to be easily renewable from the face of the panel. The circuit is not 
to be opened on the rheostat contacts, and special arrangements to be 
made for opening the circuit and rupturing the arc independent of these 
contacts. All sliding brushes to be easily renewable and of the self-align- 
ing, self-adjusting type, and able to ride over any projections standing 
one-sixteenth of an inch above the contact segments. 

All operating parts to be strong and very substantial; thin sheet-metal 
stampings are not to be employed. All such operating parts which carry 
current to be copper or composition. Where the employment of oxidizable 
metal is necessary for magnetic purposes their surfaces shall be thoroughly 
protected against oxidation by copper-plating. Where used for other pur- 
poses to be very heavily coated with a nonvitreous enamel. The contact 
points to be of composition or copper, ample in size and well fitted on the 
Burface and easily renewable. Panels should be as small and light as pos- 
sible, consistent with other requirements. 



POWER SYSTEM. 1187 



All resistances and all insulation used on them and their connecting 
wires must be noncorabustible, and the connecting wires must be capable of 
carrying their full current under all conditions of test and operation without 
becoming dangerously hot. All resistances to be of the unit type, so con- 
structed and installed that they may be easily replaced and the whole 
rheostat readily removed from the casing. The method of mounting and 
insulating the resistances is to be such that the result of a burn-out 
would be practically the same as would occur with an entirely enclosed 
resistance, and no resistance is to be used until a sample has been submitted 
to the Bureau for test and approval. The capacity of all controlling panel 
resistances must be obtained without placing the coils in parallel with each 
other, unless each is capable of carrying full-line voltage. Starting resist- 
ances when cold must be capable of carrying 50 per cent overload in cur- 
rent for one minute, and 100 per cent overload for twenty seconds. Incan- 
descent lamps or carbon shall not be used as resistance. Resistances must 
be mounted at the back of the panel upon the supporting frame, and not 
directly on the panel, for motors having a rated full load current over 50 
amperes. For motors requiring 50 amperes or less, the resistance may be 
supported from the back of the panel by suitable brackets, if desired. 

Water-tight, flame-proof panels will be used as directed in locations 
greatly exposed to moisture and where powder is handled, as ammunition 
passages, handling rooms, etc. They will, in general, consist of a cast metal, 
water-tight, flame-proof case containing the necessary resistances, con- 
nections, and operating parts, which must be controlled from without by 
means of rods or levers passing through approved stuffing boxes. The 
panels must contain within the casing at least the following parts: Resist- 
ances, circuit breaker or overload release, no-voltage release, reversing 
switch (when required), starting arm and contacts, and the necessary field 
contacts when necessary for variable speed motors. They will conform to 
the requirements for nonflame-proof panels as regards connections, capacity 
of resistance, construction of overload and no-voltage release, springs, con- 
tacts, etc., but such deviations from these requirements as may be absolutely 
necessary to simplify the construction of the panel and reduce its size and 
weight to a minimum will be considered. 

The panel will be provided with suitable removable covers provided with 
clamping devices of approved construction, made water-tight by means of 
rubber gaskets, which will permit easy access to the interior. It must be 
strong and substantial in design, but of lightest weight and smallest dimen- 
sions consistent with other requirements. Suitable bosses for tapping 
conduit into casing to be supplied, the casing to be drilled and tapped after 
delivery. The casing is to be sufficiently water-tight to permit of immer- 
sion without leakage. Noncorrosive metal requirements will be strictly 
adhered to, and all operating levers passing through stuffing boxes will be 
of composition. 

Turret-Turning* Gear. 

The following are the requirements of turret control: 

First. Turrets to be able to be turned at a maximum rate of 100 degrees 
per minute, and at a minimum rate not exceeding one-fourth of a degree 
per minute, as large a number of speeds as possible (not less than 50) to be 
provided between the limits of one-fourth and 22 degrees per minute and a 
sufficient number of speeds between 22 and 100 degrees per minute to per- 
mit of smooth and easy acceleration. The total number of speeds to be 
not less than 70. 

Second. Turret to be capable of acceleration at such rate that it can 
be started from rest and brought to its full speed of 100 degrees per minute 
in ten seconds of time, and while turning at its full speed of 100 degrees per 
minute to be able to be stopped in five seconds of time. 

Third. At all speeds between and including one-fourth and 100 degrees 
the turret is to turn continuously throughout the arc of train on each con- 
troller position with practically no variation in speed due to increased load 
on the motors caused by allowable irregularities in track, gearing, etc. 

Fourth. Turret to be able to be started and stopped ten consecutive 
times without turning through a total arc of train greater than five 
minutes. 



1188 ELECTRICITY IN THB UNITED STATES NAVY. 



There are four different systems in use at present: 

1. "Ward-Leonard System. 

2. Rotary Compensator System. 

3. Differential Gear System. 

4. Mechanical Speed Gear. 

1. The "Ward-Leonard System was used on the first electrically operated 
turrets in the Navy. The actual connections and elementary diagram of 
the installation on the " Illinois " are shown in Fig. 2. 

The motors are shunt wound, and have the fields constantly separately 
excited from the bus-bars of the ship's power system. A separate generator 
is required which cannot be used for any other purpose when used with the 
turret. The generator is also separately excited from the power bus-bars, 
but a variable rheostat, located in the turret, is connected in the shunt- 
field circuit. The brushes of the motor are directly connected to the 
brushes of the generator, and the generator is kept running at constant 
speed by its driving-engine. It is now evident that by varying the rheostat 
in the turret, the field excitation, and consequently the voltage produced 
by the generator, will be varied; and any variation in the voltage of the 
generator will produce a corresponding variation in the speed of the motor, 
which has a constant field from separate excitation. The direction of rota- 
tion of the motor is reversed by reversing the leads to the armature. The 
actual connections for the application of the above principles are shown in 
the main part of the diagram. Generator No. 4 is shown connected for 
operating the after-turret. 

Closing the after-turret field switch and the center blades of the generator 
field switch separately excites the fields of the motors and generator from 
the power bus-bars. The regular field rheostat of the generator is entirely 
'disconnected, and a rheostat located in the turret and operated by the tur- 
ret-turning controller is used instead. 

Closing the positive and negative single-pole switches on the after-current 
bus-bars connects the generator armature to the motor armatures, through 
a circuit breaker, the reversing contacts of the controller, and separate 
armature switches for each of the two motors, which are operated in 
parallel. 

The controller has one shaft, at the top of which are located the con- 
nections for the generator field rheostat, so arranged that as the controller 
is turned either way from the off position the rheostat is gradually cut out; 
below are located the reversing contacts, which reverse the connections 
between the generator armature and the motor armatures; these contacts 
are so arranged that at the off position the motor armatures are entirely 
disconnected from the generator, and are short-circuited through a low 
resistance called the "Brake resistance." The effect of this brake resist- 
ance is to bring the turret to a quick stop when the controller is brought 
to the off position, as the motor armatures revolving in a separately excited 
field generate a large current, which passes through the braking resist- 
ance, and thus absorbs the kinetic energy of the turret, giving a quick and 
smooth stop. In parallel with each of the large main fingers of the re- 
versing contacts is a small auxiliary finger and an auxiliary resistance 
connected to it. This auxiliary finger makes contact a little before and 
breaks it a little after the main finger, and thus reduces the sparking. 
The controller is also provided with a magnetic blow-out for reducing 
sparking at contacts. 

When used on this system for operating a turret the generator has its 
series coil short-circuited by a very low resistance shunt, so that it has very 
little effect on the field excitation, but this resistance is so proportioned 
that enough of the total current generated by the generator will pass through 
the series coil to give a quick and positive start of the turret; because if 
the series coil is absolutely short-circuited, and only the separately excited 
shunt coil used, the time required for the field to build up is sufficient to 
make the starting of the turret very sluggish and irregular, and prevents 
very fine training from being obtained. 

It is seen that the above-described arrangement requires a separate gen- 
erator for each turret, and while operating a turret no power can be taken 
from the generator for any other purpose. The first ships to use electric 
turning gear had only two turrets, and two generators can easily be allowed 



POWER SYSTEM. 



1189 



for turret turning; but on the latest ships six turrets are used, and it is 
very undesirable to allow six generators for this purpose. To overcome 
this objection the Ward-Leonard method of control is obtained by means 
of a motor generator located at each turret, all of which take power directly 
from the main bus-bars of the dynamo room, thus materially reducing 
the required generator capacity. An elementary diagram of the arrange- 
ment is shown in Fig. 7. It will be noted by comparison with Fig. 2, that 
only two instead of five wires have to be run from the dynamo room to 
each turret. 

The Ward-Leonard system will not give the large range and low speeds 




Two wires between 
Dynamo Room and Tuitet 



Fig. 7. Diagram of Motor Generator on Turret-Turning System. 



now required by the Navy Department and therefore the other above- 
mentioned systems have been devised. 

2. The Rotary Compensator System is shown in Fig. 8. A and B are 
the armatures of a motor generator balance set, called a Rotary Compen- 
sator Set. L is a large shunt motor geared directly to the turret. S is a 
small shunt motor the shaft of which carries a worm, Wl, working in a 
worm wheel, W2, mounted on the shaft of L. This worm wheel is pro- 
vided with a magnetic clutch D so that it can turn freely on the shaft of L, 
or be held to it. C is a contact in the controller which opens one side of 
the armature circuit of L. R is a field rheostat for A and B and is operated 
by the controller. With the connections as drawn in the diagram, B has a 
weak field .and a low voltage, thus driving S at a low speed ; S is driving L 
through the magnetic clutch and worm gear and thus turning the turret 
at a very low speed; Cis open, so L turns freely, and does no work. As the 
controller is turned R is gradually inserted in the field of B, thus increasing 
the voltage and increasing the speed of S. When B has full field the mag- 
netic clutch is opened and C is closed, thus transferring the load from S to 
L and permitting S to run free. At this time A has weak field and supplies 
a low voltage to L, and further movement of the controller brings the arm of 
R back to the first position, thus increasing the voltage of A and the speed 
of L, until A has full field and the turret is turned at full speed. At the 
period of transition when the load is shifted from S to L it is necessary that 
the ratio of the speeds of S and L shall be the same as the ratio of the 
worm gearing by which S drives L, so that the transfer will be made smoothly 
and without shock or change in speed of turret. In shutting down the 
above actions occur in reverse order. Reversing is accomplished by rever- 
sing the armature loads of the two motors, and in the off position 
the armature of L is short-circuited to produce a braking effect; these results 
are accomplished by controller contacts similar to those for Ward-Leonard 
System as per Fig. 2. This system is made by the General Electric Company. 



1190 



ELECTRICITY IX THE UXITED STATES NAVY. 




Glaring 



Fig. S. Rotary Compensator Turret-Turning System. 

3. The Differential Gear System is shown in Fig. 9. L and S are respect- 
ively large and small shunt' motors running continuously on the supply 
main. They are both directly geared to a differential gear which is so pro- 
portioned that with L running at full speed and S at weak field the shaft 
A will stand still, but any change in their relative speeds will cause A to 




Fig. 9. Differential Gear Turret-Turning System. 



rotate at a speed proportioned to the relative change. This change in 
relative speed is produced by the field rheostats Rl and R2 which are 
operated by the controller, and first decrease the speed of S by strengthening 
its field, and then increase the speed of L by weakening its field, thus giving 
the full speed range of the turret. The shaft A is geared to the turret 
through the gears Gl and G2, each of which is provided with a magnetic 



AMMUNITION HOISTS. 1191 



•lutch CI and C2. G2 is geared direct, and Gl through a reverse gear, 
thus accomplishing the reversing of the turret motion. The magnetic 
clutches are operated by contacts on the controllers. This system is made 
by The Cutler-Hammer Manufacturing Company. 

4. The Mechanical Speed Gear System uses a continuously running, con- 
stant speed, shunt motor geared to the turret through the speed gear. The 
speed gear consists of a variable volume oil pump and an oil motor mounted 
in a common casing and provided with mechanical means for varying the 
volume of oil delivered by the pump per revolution and its direction of 
flow. The speed gear is made by the Waterbury Tool Company. 

In all the above systems two sets of motors are usually provided and 
arranged so that by means of switches either set may be cut out and the 
turret operated by one set. Turrets carrying two 12-inch guns usually 
have two 25-horse-power main motors, and 8-inch turrets two 15-horse- 
power motors. 

loading* and Training* Grear for Guns. 

Guns of 8-inch and over are elevated and rammed by power ; smaller guns 
have hand gear. 

Three kinds of elevating gears are in use: 

1. Plain rheostat control with series motor. 

2. Ward-Leonard control. 

3. Mechanical speed changing gear with constant speed, shunt motor. 
Rheostatic control with series motor as used in the first vessels does not 

give sufficiently close and even control. A 2^-horse-power, 300 r.p.m. 
motor with plain drum-reversing controller is used. 

Ward-Leonard control as used is similar to that used for turret turning 
as shown in Fig. 7. The control obtained is quite satisfactory, but the 
complication is objectionable and there is not suitable space available in 
the turrets for the motor generators. Ten horse-power elevating motors 
and eight K.W. motor generators are used. 

The latest vessels are using constant speed shunt motors and obtaining 
the control by means of mechanical speed gears as described above for 
turret turning. 

Rammers consist of a telescopic tube worked through spur and chain- 
gearing by a 5 H.P., 775 r.p.m. series motor. A friction slip clutch is 
inserted in the gearing to prevent damage when the shell seats itself in the 
breech. Ordinary rheostatic control is used. 

When ramming a shell but little power is required, as the shell slides 
along the breech, but as it is being forced to its seat at the end of the breech 
chamber a sudden rush of current of from two to three times the full-load 
current of the motor is produced. 

AMIttUXITIOM HOISTS. 

Power ammunition hoists are of two kinds: first, those in which a car 
or cage is hoisted up and down by a line wound on a drum on the motor 
counter-shaft; and second, those in which the motor runs an endless chain 
provided with toes or buckets on which the ammunition is placed and con- 
veyed up through a trunk. 

Hoist* for 12-inch and 13-inch Ammunition. 

These hoists are of the first kind. The motor frame is provided with 
bearings for a counter-shaft, geared by a spur-gear and pinion to the arma- 
ture shaft; on the counter-shaft is mounted a grooved drum for the hoist- 
ing-cable. 

On the armature shaft is mounted a solenoid band-brake. The cores of 
the solenoid are weighted and attached to the brake-setting lever so that 
when free their weight is sufficient to hold the loaded car from falling; 
when the solenoids are energized the cores are drawn up and the brake re- 
leased. 

The controller is constructed so that on the off position the solenoids are 
not energized and the brake is set; but at all other points, both hoisting and 
*<Dwering, the solenoids are energized and the brake released. 



1192 ELECTRICITY IN THE UNITED STATES NAVY. 



Shunt motors are used, and the control for hoisting is ordinary rheostatic; 
the resistance being put in series with the armature and gradually cut out, 
the field is always constantly excited as soon as the feeder-switch is closed. 
For lowering, the entire rheostat is thrown directly across the line, one 
armature lead connecting to one side of the line and the other lead gradu- 
ally moved (as the motor is brought to full speed) from the condition of a 
short-circuited armature at the off position to direct connection to the other 
side of the line at the full on position; in all intermediate positions the 
armature is in shunt with a part of the rheostat. The object of this is to 
cause the armature to take current from the line and run as a motor when 
lowering a light load which will not overhaul, but to run as a generator and 
send current through the rheostat if the load is very heavy and overhauls 
the motor and gearing. In either case the speed will depend upon the 
amount of the rheostat that is in shunt across the armature. The off posi- 
tion of the controller short-circuits the armature, and since the fields are 
always excited, this gives a quick stop and also holds the load. 

The 13-inch hoists of the U. S. S. "Kearsarge" and "Kentucky" use 20 
H.P. motors running at 350 r.p.m., with a gearing ratio of 6.43 from arma- 
ture to counter-shaft. 

The load was, empty car 1,846 pounds, and full charge 1,628 pounds, or a 
total of 3,474 pounds. 

The following average results were obtained when testing a hoisting full 
charge: 

Hoisting-speed, feet per minute 180 

Mechanical H.P. in load 18.96 

Input of motor, E.H.P 28.5 

Total efl&ciency . 66.6% 

Motors were designed to be suspended under the turret, were entirely 
enclosed, and weighed 3,000 pounds complete with brake. 

Hoists for 8-inch Ammunition. 

Hoists for smaller ammunition are made and controlled in a manner 
similar to the above. 

The 8-inch hoists used a 6 H.P., 375 r.p.m. shunt motor to hoist a total 
load of 910 pounds at 163 feet per minute. 

Tests gave average results of — 

Mechanical H.P. in load .... 4.5 

Input of motor, E.H.P 7.4 

Total efficiency 60.8% 

Endless Chain Ammunition Hoists. 

These hoists run continuously, the ammunition being fed in as desired. 
The motor is geared to the chain sprockets by spur gearing, is shunt wound 
and is started and stopped by a controlling panel, which is provided with 
no-voltage and overload release, and a reversing-switch. 

A solenoid brake is mounted on the armature shaft, and is set when the 
starting-arm is in the off position, but has its coils energized and is released 
when the arm makes the first contact in starting. At the full on position, 
part of the starting rheostat is in series with the brake, thus cutting down 
the current consumed by it. This does not affect the reliability of the 
brake, since the current required to hold up the cores is much less than 
that required to first start them, and at the start the full-line voltage is on 
the coils. 

To lower ammunition the reversing-switch is thrown down, which re- 
verses the connections to the motor armature, and puts in the armature 
circuit a safety switch. This safety switch is attached to the lever which 
operates the catch pawls in the hoist trunk. These pawls will allow ammu- 
nition to go up, but will catch and prevent it from going down, and are 
used to keep the ammunition from falling in case any part of the hoist 
should be shot away. When the pawl lever is thrown down it throws the 
pawls out of action, and allows ammunition to be lowered by reversing the 



AMMUNITION HOISTS. 



1193 



motor ; it also closes the safety switch which completes the armature cir- 
cuit for the lowering position of the reversing-s witch. 

This style of hoist is used for all kinds of ammunition up to and including 
7-inch. Packages are so made that they weigh about 100 pounds each. 
Motors from 2^ to 3 H.P. output and about 400 r.p.m. are used. Height of 




hoist varies from 10 to 40 feet, and about 12 packages per minute are hoisted. 
Mechanical efficiency from motor output to power in load varies from about 
50% to 80%. * 

Ammunition conveyers, very similar to these hoists, are used to carry 
ammunition from some magazines to the foot of the hoist. The endless 
chain is horizontal, and no brake or safety switch is used. 



1194 ELECTRICITY IN THE UNITED STATES NAVY. 



BOAT CRAVES. 

For handling steam cutters and other boats a revolving crane having the 
general shape of a davit is used ; it extends down to the protective deck, 
and has a steady bearing at each deck passed through, and the weight is 
carried by a roller thrust bearing. The operating machinery is carried on 
a circular platform fastened to the crane. 

The standard specifications require the following control to be obtained : 

The mechanical connections between the hoisting motor and its gearing 
and the electrical connections between motor and controller to be such that 
the following results are obtained : 

I. No possible combination of manipulation of operating lever, opening 
of circuit breaker, or failure of current to allow any load to fall. 



LOWER 




Fig. 11. Diagram of Connections for Boat Crane Motors. 



II. The load to always stop and be held still immediately when the con 8 
trolling or operating lever is brought to the off position during hoisting or 
lowering. The electric brake itself (in case of failure of mechanical brake) 
to be of sufficient power to stop and hold the maximum load at the off 
position or upon failure of current. 

III. Maximum load not to lower while the controller operating lever is in 
any hoist position. 

The control of the rotating motor must give the following results : 

IV. Smooth starting and stopping must be obtained under all conditions 
of load and speed. 

V. Crane must stop and be firmly held when the controller operating 
lever is brought to the off position. 

VI. Swinging of the suspended load or rolling of the ship must not pro- 
duce dangerous or excessive variations in the rotating speed. 



BOAT CRANES. 



1195 



Ordinarily two motions are provided, rotating and hoisting, and a sepa- 
rate motor is used for each ; but sometimes a trolley is used so that the load 
can be moved radially ; when used the trolley is operated from the hoisting 
motor, which is then provided with a change clutch in the gearing. 

Plain series motors are used. The hoisting motor is usually geared to the 
drum by one pair of spurs and a worm, the worm wheel being fastened to 
the drum, and the pinion being on the armature shaft. At some convenient 
point in the gearing an automatic mechanical brake is inserted, which will 
only allow the load to lower when the motor is run by electric power in the 
lowering direction, and which absorbs the energy of the lowering load in 
friction. The design which at present has given the best results is that 
using friction disks and a follow-up screw similar to the brake used in the 
Weston triplex pulley block. A solenoid brake is also mounted on the 
armature shaft, which sets at the off position of the controller. The rotat- 
ing motor is similar to the hoisting motor, but smaller. Cranes are required 
to rotate at the rate of one revolution per minute. 

The sizes of motors used on the usual capacities of cranes on the latest 
vessels are as follows : 



Capacity 

of 

Crane Pounds. 


H.P. 

of Hoisting 
Motor. 


H.P. 

of Rotating 

Motor. 


Hoisting Speed, 

Feet 

per Minute. 


33,000 
17,000 
10,000 
5,600 


50 
30 
30 
20 


30 
20 
20 
15 


25 
25 
40 
40 



Tests on typical cranes gave the following results : 



No. 


Load, 
Lbs. 


Speed, 
Ft. 
per 
Min. 


H.P. 

in 
Load. 


Motor 
Input, 
E.H.P. 


Efficiencies. 


•553 




Motor 


Total. 


Motor. 


Gear- 
ing. 


Input, 
E.H.P. 


1 
2 
3 


19,000 
18,000 
10,300 


29.7 
24.1 
31.0 


17.1 
13.1 
9.67 


29.7 
27.9 
19.3 


57.5 
47.0 
50.1 


86. 
82. 
82. 


66.8 
57.3 
61.1 


82,000 
72,000 
46,000 


1.46 

.89 

1.85 


15.4 
14.8 
9.9 



All of the above cranes hoisted the load by a two-part tackle, and the 
details of the gears were : 

No. 1. Pinion 22 teeth, gear 70 teeth, \\" pitch, 4" face. 

Worm triple threaded, 32" pitch, 9.6" lead, 12£" P.D. 
Worm wheel 42 teeth, drum dia. 29£". 
350 r.p.m. of motor = 30 ft. per min. hoist. 

No. 2. Pinion 19 teeth, gear 87 teeth, \\" pitch, 4" face. 
Worm triple threaded, 3" pitch, 9" lead, Yl\ P.D. 
Worm wheel 33 teeth, drum dia. 24". 
400 r.p.m. of motor = 25 ft. per min. hoist. 
This crane had also a pair of miter gears of 18 teeth, 1\" pitch, 
6" face. 

No. 3. Pinion 29 teeth, gear 63 teeth, \\" pitch, 4" face. 
Worm triple threaded, 2" pitch, 6" lead, 9" P.D. 
Worm wheel 57 teeth, drum dia. 26£". 
360 r.p.m. of motor = 30 ft. per min. hoist. 



1196 ELECTRICITY IN THE UNITED STATES NAVY. 



DECK WiXCHE*. 

The usual design of electric deck winch consists of a series motor geared 
by spur gearing to a shaft carrying a gypsy head, all being mounted on a 
suitable bed-plate. Part of the winches on a vessel usually have change 
gears giving two speeds, which are operated by clutches. The usual capa- 
city is 2,200 pounds' pull at a speed of 300 feet per minute, and on winches 
having change gears the low speed is 13,000 pounds at 50 feet per minute. 
A friction band brake operated by a foot lever is used. Rheostatic control 
is used, with a reversible controller. Motor and controller are both en- 
tirely water-tight, and will stand a stream of water from the fire hose. The 
rheostats are mounted in the bed-plate, or else in a water-tight iron box. 

The usual method of operation is to run the winch continuously at full 
speed in one direction, and then control the hoisting and lowering of the 
load by taking a suitable number of turns of the hoisting rope around the 
revolving winch head. Very good control of heavy loads can be obtained in 
this manner ; but if much lowering of heavy loads is done, difficulty will be 
had with the winch heads becoming hot. 

On single geared winches having but little friction in the gearing, the 
speed of a plain series motor at no load would be dangerously high, and to 
overcome this a small amount of shunt winding is added. On two-speed 
winches the initial friction is usually enough to prevent dangerous no-load 



30 H.P. motors are used on both of the designs. 

VEHTTILATIOlf JTAHTS. 

Nearly all compartments of a ship have artificial ventilation by electric- 
ally-driven fans, usually operating on the pressure system, but in some 
cases exhaust fans are used. All of the hull ventilation fans are electric, 
but the forced draft fans for the boiler rooms are steam driven in most 
cases, although a few of the later vessels have electric drive. 

Fans are driven by shunt motors, usually of the open type, but in some 
exposed locations entirely enclosed motors are used. Full speed of motors 
is that required to make the fan deliver air at 1^ ounces per square inch 
pressure, and speed variation down to the speed giving 1 ounce is required, 
which is a reduction of about 20 per cent. This speed variation is obtained 
by field resistance on motors above 1 H.P., and by armature resistance on 
smaller sizes. Controlling panels are used which have the necessary rheo- 
stats for the speed control, and also overload and no-voltage release. 

Principal Requirements for Ventilating: fans. 

The following may be considered as standard capacities for ventilating 
fans and will in general be specified: 

600 cubic feet. 5,000 cubic feet. 

1,000 cubic feet. 6,000 cubic feet. 

1,600 cubic feet. 8,000 cubic feet. 

2,500 cubic feet. 10,000 cubic feet. 

4,000 cubic feet. 12,000 cubic feet. 

All fans to be built up of steel plate with the exception of the 600, 1,000, 
and 1,600 cubic feet, which must be of cast shell construction. Fans to be 
practically noiseless and to be of the convertible type so constructed that 
they will be suitable for either right or left hand and for at least eight differ- 
ent angles of discharge. Cast shell fans to be so constructed that they 
may be installed on deck, on vertical bulkhead, or suspended from deck 
above. All fan wheels and the interior of steel-plate fan casings to be 
galvanized to prevent corrosion. Interior of casings of cast shell fans to 
be thoroughly coated with asphaltum. Fan wheels to be of steel, keyed on 
shaft with set screw in hub; hubs to be brass bushed; cast shell fans to be 
of heavy, soft, cast iron, free from all cracks, blowholes, or other defects, and 
suitably re-enforced at all points of strain. A hand hole to be provided i» 



VENTILATION FANS. 1197 



casing of all cast shell fans for access to set screw in hub of wheel; cover 
for this hole to be finished and made air-tight without the use of putty or 
similar substances. Scrolls of steel-plate fans to be in three removable 
sections. Each fan to be provided with a name plate giving the capacity 
in cubic feet per minute. Inlets and outlets of cast shell fans and inlets of 
steel-plate fans to be circular in shape, outlets of steel-plate fans to be 
rectangular. Area of fan inlets shall not exceed area of outlets, the inlet 
to be straight, and no temporary means shall be employed in any test to 
reduce the friction of the inlet. After installation on shipboard, the fans 
to be provided with suitable drip pans with cocks. 

Each fan with its motor and controlling panel to be assembled and tested 
at the works of the maker in the presence of a government inspector, suit- 
able means being provided for measuring all data. 

In making shop tests the set shall be erected with free inlet to the fan. 
There shall be attached to the fan outlet a pipe of the area of the outlet, 
whose length shall be not less than 20 diameters of the outlet for fans with 
round outlets, or twenty times the average of the breadth and depth for fans 
with rectangular outlets. A double Pitot tube designed to indicate the 
pressure produced by the impact of the moving air, and the actual pressure 
in the moving air shall be inserted in the center of this pipe at about one- 
half its length, with the axis or the tube in the center line of the pipe. The 
Pitot tube to conform to dimensions shown on drawing, which may be 
obtained on application to the Bureau of Construction and Repair. An 
adjustable throttling device shall be fitted to the end of the pipe and adjusted 
with tr*e fan running at its designed full speed, with motor fields hot, until 
head of water, in inches, shown by a manometer connected to the pressure 
side of the Pitot tube, is not less than 13.4 times the weight per cubic foot 
of the air in pounds. When this condition is obtained the head of water, in 
inches, shown by the manometer connected to the impact side of the Pitot 
tube, shall not be less than 17.4 times the weight of the air per cubic foot 
in pounds. The correct weight of the air in pounds per cubic foot shall be 
obtained from the tables of the Bureau of Construction and Repair, which 
are entered with the barometric pressure and wet and dry bulb temper- 
atures. The wet and dry bulb thermometer shall be placed near the fan 
inlet but not so close to it as to appreciably obstruct the current of approach- 
ing air. It is the object of this test to make sure that the fan under test, 
when running at full speed, shall be capable of discharging air through a 
pipe the full size of the outlet against a pressure of five pounds per square 
foot, with a velocity of not less than 2,200 feet per minute at the center of 
the discharge pipe. A hook-draft water gauge or approved manometer 
apparatus shall be used in connection with the Pitot tube. For apparatus 
to record pressure direct a pressure of 5.2 pounds per square foot shall be 
taken as equivalent to one inch of water. No specific requirement as to 
air delivery with free outlet is made. 

Note . — The above-mentioned tables of the weight of air under different 
atmospheric conditions will be furnished by the Bureau to fan manu- 
acturers upon application. 

Fans when tested under the above conditions must deliver their rated 
/olumes at the required pressures and a static pressure in inches greater 
;han 14.74 times the weight of air in pounds per cubic foot, or an impact 
pressure greater than 19.14 times the weight of air will not be allowed. 
The difference between the static and impact pressure must never be less 
than four times nor greater than 4.4 times the weight of the air. No means 
shall be employed to reduce the friction of the inlet during the tests. 

In calculating results of tests the following approximate formulas will 
be used: 



V w 



v = 997. 

" W 

This formula assumes that a velocity at the center of the pipe of 2,200 
feet per minute corresponds to an average velocity over the whole area of 
the pipe of 2,000 feet per minute. 

V = Av 
„ p _ 5.2hiAv _ hiAv 
~ 33000 ~ 6345 



1198 ELECTRICITY IN THE UNITED STATES NAVY. 



when V = volume in cubic feet per minute. 

v = velocity in feet per minute. 
h x = impact pressure in inches of water. 
h.2 = static pressure in inches of water. 
^8 = hx -h,2 — velocity head in inches of water. 
A = area of outlet in square feet. 
H.P. = horse-power delivered by the fan. 
W = weight of air in pounds per cubic foot. 

Note. — Instead of a single Pi tot tube a number of tubes, not less than 
nine or more than thirteen, distributed over the pipe section may be used if 
preferred, by the contractor. In this case the mean static pressure, in 
inches of water, must not be less than 13.4 times the weight per cubic foot 
of the air in pounds, and when this condition is obtained, the mean impact 
pressure in inches of water shall not be less than 16.72 times the weight of 
air in pounds per cubic foot. It is the object of this test to determine that 
the fan will deliver the required volume of air at a mean velocity of 2,000 
feet per minute over the whole area of the pipe. Similar variation in 
pressures to that specified above will also be allowed under these conditions. 

The heat run on each motor is to be of eight hours' duration, made when 
driving its fan with free outlet and inlet at the above required full speed, 
and under such conditions the temperature rises of all parts must not exceed 
those allowed for continuous-running motors. Also these temperature rises 
are not to be exceeded when the fan is run as above at full field strength of 
the motor. 

Each set is also to be given an endurance test by running for forty-eight 
hours continuously at full speed with free inlet and outlet of fan (forty 
hours in addition to the above test of eight hours at full speed, the fan to be 
started up immediately after taking temperatures at end of eight-hour run), 
and during this run absolutely no attention or adjustment is to be given 
to the motor. At the end of the run the motor must be in operation in a 
satisfactory manner and without sparking, blackening, burning, or rough- 
ening of the commutator, or the development of high mica, copper sticking 
to the brushes, or any other latent defects. Any set which fails to pass 
this endurance test on the first trial will be allowed a second trial, after 
overhauling and adjusting, but if it fails on the second trial it will be re- 
jected. 

Results Obtained from above Shop Tests. 





















a . 

2 »H 


< 




W a 


Rated 
Size. 


r.p.m. 


fc. 


hi. 


fcs. 


W. 


v. 


A. 


V. 


£ o 


.2 




\1 » 




















& 


c3 o> 


o « 




















.298 


H 


— — 

45.3 


s^ 


600 


2200 


1.350 


1.041 


.309 


.0715 


2072 


.306 


634 


.135 


61.1 


2500 


1140 


1.352 


1.036 


.316 


.0726 


2075 


1.25 


2595 


1.415 


.555 


39.2 


76.2 


2500 


1140 


1.383 


1.075 


.308 


.0734 


2037 


1.25 


2546 


1.25 


.555 


44.3 


74.4 


4000 


875 


1.318 


1.014 


.304 


.0721 


2052 


2.00 


4105 


2.08 


.854 


41. 


83.6 


5000 


810 


1 .377 


1.062 


.315 


.0722 


2084 


2.50 


5210 


2.97 


1.131 


38.1 


82.6 


10,000 


575 


1.268 


.971 


.297 


.0724 


2016 


5.00 


10,080 


5.00 


2.014 


40.3 


84.1 


12,000 


525 


1.275 


.970 


.305 


.0725 


2050 


6.00 


12,300 


6.28 


2.47 


39.4 


84.8 



H'ATElI-TlCiUT DOORS. 

Electrically-operated water-tight doors are now being installed on most 
large ships. The requirements of a successful system are that all doors 
can be simultaneously closed from the bridge, that during or after this 
closing any door can be opened by a person desiring to pass through from 
either side, and after such passage the door to automatically close itself. 

The design in most general use is that of the Long- Arm System Co., of 



WATER-TIGHT DOORS. 



1199 



Cleveland, O. The doors are moved by a 1 H.P. compound-wound motor 
geared to the door plate through spur gears and a worm and rack. Control 
at the door is obtained by a small hand-operated controller, having an oper- 
ating handle on each side of the bulkhead. Control from a distance is 
obtained by an " emergency station" located on the bridge which closes the 
doors by means of a secondary circuit and solenoids. An indicator is also 
installed at the emergency station to show when each door closes. 

The system is shown diagrammatically in Fig. 12. The controller connects 
the motor directly to the line, without the use of any starting resistance, 
and the motors are specially designed for this. When the door reaches 
either the top or bottom of its motion, it actuates the " upper limit 
switch," or the " lower limit switch," which opens the line circuit and 
stops the door. These limit switches are actuated through a series of 
cams, springs, and. levers, attached to the driving gearing, so that a limit 
switch is opened whenever the door plate encounters any great resistance. 
In fact the operation of the limit switch, when the door opens or closes, 
is caused by the resistance to further motion, and not by the position of 



HAND CONTROLLER 

-QE£ £7 

OPEN 




INDICATOR CONTACT 



Fig. 12. Diagram of Connections for Electric Control of Water-tight 
Sliding Doors. 



the door plate. This arrangement prevents any obstruction from burning 
out the motor, and at the same time, if the emergency station action is on, 
the door will continue its closing motion when the obstruction is re- 
moved. 

The emergency station consists of a series of contacts, one for each 
door, which, when closed, excite solenoids located in the hand controllers. 
The two contact plates of the hand controller, which are located at the 
right-hand side of the diagram, are free to rotate on the controller shaft ; 
and when the solenoid is excited it rotates them so that they make con- 
tact with their ringers, and thus produce the same result as moving the 
hand controller to the " close " position. The solenoid is so weak that it 
can be overpowered by the hand operation of the controller when it is 
moved to the "open" position, thus allowing a man at the door to make 
it open at any time when the emergency closing is in action. Upon releas- 



1200 ELECTRICITY IN THE UNITED STATES NAVY. 



ing the handle of the hand controller it comes back by a spring to the 
44 off " position, and if the emergency is still on, the door starts to close 
again. The mechanical construction of the emergency station is such that 
by moving a lever the contacts for the different doors are made one after 
the other with a slight interval of time between each, so that the sudden 
rush of starting current will not occur on all doors at the same instant. 

The indicator consists of a case containing a small incandescent lamp for 
each door. When the door closes it operates an indicator contact which 
lights the corresponding lamp. 

The door is powerful enough to cut through several inches of coal on the 
sill. In service the current required for operation of a vertical sliding door 
2 ft. by 4 ft. 9 in. is about as follows : 

Opening : 

Sudden throw, start 25 amp. 

Running up 8 to 10 amp. 

Sudden throw, stop 15 amp. 

Closing : 

Sudden throw, start 20 amp. 

Running down 6 to 9 amp. 

Sudden throw, stop 11 amp. 

Voltage is 125 volts. 

STEERING-GEAR. 

Electrical steering-gears are not at present used in the United States Navy, 
but are somewhat used in foreign navies. One method used is shown in 
the diagram of connections (Fig. 13), in which M is a shunt motor oper- 
ated from the ship's mains and running continuously at constant speed ; 
its shaft is directly coupled to G, a shunt generator, the two forming a 



HIPS MAINS 




Fig. 13. Diagram of Steering-Gear. 



motor generator set and located at any desired place, most conveniently in 
the dynamo room. P is a shunt motor geared by suitable gearing to the 
rudder post, and has its field constantly excited from the ship's mains, its 
brushes are directly connected to the brushes of the constantly running 
generator G. R and R' are two equal and symmetrical rheostats, the con- 
tact arm of R being attached to the rudder post or any part of its gearing 
which has a similar rotation, and the contact arm R' being attached by 
suitable gearing to the steering-wheel. The ends of the field of G are con- 
nected to these two contact arms, and the two rheostats are connected 
across the ship's mains. 

It is now seen that the two rheostats and the field of G form a Wheat- 
stone's bridge, the parts of the rheostat on each side of the contact arms 
being the four resistances, the field of G taking the place of the galvanom- 
eter and the line being the battery. This bridge is in balance, and no 



STEERING-GEAR. 



1201 



current will flow through the field of G whenever the two rheostant arms 
occupy similar positions on their respective rheostats ; but if they do not 
occupy similar positions, then the bridge will be out of balance and current 
will flow through the Held of G. 

The operation is as follows : Starting with everything central as shown 
in the diagram, if the steering-wheel is turned, moving the arm of B/ a 
certain distance, the balance will be disturbed and current will flow through 
the field of G, causing it to generate an E.M.F. and start the motor P, which 
will continue to run until the arm of R has been moved a distance equal to 
the original movement made by the arm of R', when the balance will be 
restored, no current will flow through the field of G, which will then 
develop no E.M.F. , and the motor P will consequently stop. The gearing; 
between P and the contact arm of K is so arranged that the movement of 
the arm will be in the proper direction to restore the balance. The direction 
of current flow in the field of G, and consequently the polarity of G and 
direction of rotation of P, will depend upon the direction of movement of 
the arm of R'« It is thus seen that the arm of R is given an exact copying 
motion of the arm of R', both for distance moved and direction of rotation. 

Instead of actually turning the rudder, the motor P can be made, if 
desired, to only operate the valve of a steam-steering engine ; when this is 
done the device is called a " Telemotor." 

Another method (which has only been applied for use as a telemotor) has 
the first movement of the steering-wheel connect the operating motor 
directly to the ship's mains, and the motion of the motor causes a step by 
step mechanism to disconnect it when it has moved the engine valve a 
distance proportional to the original movement of the steering-wheel. Both 
connection and disconnection of the operating motor are made by a switch 
at the steering-wheel, the interrupter of the step-by-step mechanism is at 
the operating motor and the mechanism itself at the steering-wheel. The 
mechanical arrangements are quite complicated. 

Several ships of the Russian Navy have been fitted with direct acting 
steering-gears by the Electro-Dynamic Company, of Philadelphia, Pa., 
and work on the above first described bridge principle, with the addition 
of a small exciter for the generator mounted on the generator shaft, and 
the field of this exciter is connected with the bridge rheostats, instead of 
the main generator field itself. The motor of the motor-generator is rated 
at 70 H.P., the generator at 500 amperes and 100 volts, and the rudder 
motor at 50 H.P. ; all being easily capable of standing 50% overloads for 
short periods of time. The motor-generator runs at 650 r.p.m. and weighs 
11,000 pounds ; the rudder motor runs at 400 r.p.m. and weighs 5,500 pounds ; 
the accessory appliances weigh 1,500 pounds, making a total weight of 
18,000 pounds. 

Tests made on the Russian Cruiser " Variag" took 150 H.P. to move the 
rudder from hard-a-port to hard-a-starboard in 20 seconds, while going at a 
speed of 23 knots an hour. For ordinary steering at about 19 knots, readings 
taken every time the rudder was moved gave the following results : — 



Amperes. 


Volts. 


K.W. 


250 


4 


1. 


250 


10 


2.5 


150 


14 


2.1 


180 


30 


5.4 


200 


40 


8. 


100 


50 


5. 


100 


55 


5.5 


50 


5 


.25 


50 


25 


1.25 


60 


40 


2. 


100 


22 


2.2 


100 


25 


2.5 


50 


15 


.75 


200 


26 


5.2 


100 


18 


1.8 


100 


20 


2. 



1202 ELECTRICITY IN THE UNITED STATES NAVY. 



Readings were taken for every movement occurring for a period of % hour, 
rudder was never moved more than 15 degrees. 

IXTEItIO.lt COMMUNICATION SYSTEM. 

The interior communication system of a ship consists of, as the name 
implies, the appliances for transmitting signals of all kinds from one part 
of the ship to another. 

Order and Position Indicators. 

Many devices have been tried for the electrical transmission of pre- 
arranged orders, or the position of a moving body, such as a rudder-head; 
but the most successful and the one generally installed consists at the re- 
ceiving end of a number of small incandescent lamps, each mounted in a 
small, separate, light tight cell with a glass front, and the whole enclosed in 
a suitable case. On the glass front of each light cell is marked an order or 
number, or whatever particular information the particular device is to in- 
dicate. This receiver is connected to the transmitter by a cable having a 
separate wire for each lamp, and one wire for a common return. The trans- 
mitter consists of a switching device, by means of which any lamp or lamps 
in the receiver may be lighted, the current being taken from the lighting 
mains. As many receivers as desired can be operated from one transmitter, 
the receivers being connected in parallel. 

Helm Angle Indicator. 

When the above-described device is used to indicate in different parts of 
the ship the angle that the helm is turned, the transmitter switch consists 
of an arm, as shown in diagram (Fig. 14) fastened to the rudder stock, and 
moving over a series of contact pieces arranged in an arc in the same manner 
as an ordinary field rheostat. Each of the contact pieces is connected 
through one wire of an interior communication cable to one side of one of 
the receiver lamps, which lamp has marked on its front the number of 
degrees that the given contact is situated from the center line of the ship; 
the other side of the lamp is connected to the common return wire, which 
goes to the source of current and then to the contact arm. As the rudder 
turns, the contact arm makes connection with the different contact pieces, 
and as it touches each piece the corresponding lamp in the receiver lights 
up and indicates its position within the limits shown; when it is just mid- 
way between any two pieces it will touch both and light both corresponding 
lamps, which doubles the closeness with which the position is indicated. 

As many receivers can be connected on as desired, all being operated in 
parallel. 

Engine Telegrraphs. 

When used for engine order telegraphs the contact arm is mounted in a 
metal case and operated by a hand lever of the same construction as the 
hand lever of an ordinary mechanical ship's engine telegraph, as shown in 
Fig. 15. The case contains indicator lamps in parallel with the lamps of 
the receiver at the engine room, so that the operator on the bridge has 
visual evidence of the order sent. A small magneto is geared to the trans- 
mitter handle, and rings a bell at the receiver whenever the handle is moved, 
thus calling attention to the change of order. 

Battle Order Indicators. 

The receiving indicators are of the same construction as above described 
for the Helm indicators, but the transmitter consists of single-pole snap 
switches, connected up exactly like the lamps of the indicator, so that by 
turning the proper switches any desired number of lamps can be lighted. 



INTERIOR COMMUNICATION SYSTEM. 



1203 




CONTACT ARM FASTENED TO RUDDER POST 



and of course any desired order can be marked in front of any lamp. Sev- 
eral indicators, located in different parts of the ship, are usually worked by 
each transmitter, all being connected in parallel. 

The case which contains the transmitter switches also contains an indica- 
tor, thus always showing what orders are being indicated on the system. 



1204 ELECTRICITY IN THE UNITED STATES NAVY. 



Engine Telegraph Indicator Section of Transmitter 



.Ball on Padestat-j-flQ 
Transmitter 



Indicator 




Fig. 15. Diagram of Engine Telegraph. 



Rangre Indicators. 

Range indicators are exactly like the battle order indicators, except that 
instead of having different orders marked before each lamp, a number rep- 
resenting the range in yards is marked. 

A range indicator and a battle order indicator are usually mounted to- 
gether at desired stations, thus showing what kind of firing is to be done 
and at what range. 

Revolution Indicators. 

To show on the bridge the direction and speed of rotation of the engines 
several appliances have been devised. The one most generally used is shown 
in Fig. 16, and consists at the transmitter of a small gear E, mounted eccen- 
trically upon the propeller shaft S, and meshing with a pinion P, which is 
carried on the lower end of an arm A. The arm A is slotted and mounted 
on a pivot as shown, and when S is rotating, A will be turned to one side or 
the other, depending upon the direction of rotation of S, until it bits on the 
stop B, and will then remain against the stop and reciprocate up and down 
from the eccentric action of E ; on each up movement it will make contact 
with clip C or C, depending upon which side it is turned. 



INTERIOR COMMUNICATION SYSTEM. 



1205 



The receiver consists of two pivoted pointers, connected as shown to two 
electromagnets and marked " Astern" and " Ahead." 

From the connections shown, it is seen that at each rotation of the pro- 
peller shaft the pointer corresponding to the direction of rotation will make 
a movement, and at the same time the magnet armature will make a plainly 
audible click, thus indicating both visually and audibly the rotation. The 




1206 ELECTRICITY IN THE UNITED STATES NAVY. 



other pointer corresponding to the direction in the opposite rotation will 
remain still. For twin screws a separate transmitter and receiver is in- 
stalled for each. 

A later design of the transmitter is shown in Fig. 17, which eliminates 
reciprocating motion and prevents wear. E is a large multiple worm 
mounted on the propeller shaft S. D is a worm wheel on the small shaft 
F, on which is mounted the insulating drum B. A is a metallic contact 
strip set into B and makes contact across two of the leads as shown. C 
is a cam which moves B along its shaft, and holds B in the position shown 
for astern motion, so that the contact A connects the center and left hand 
leads at each revolution of F. For ahead rotation C shifts B to the right 



n F 


B ,A C 


- 



















Fig. 17. Diagram of Connections of Transmitter for Revolution Indicator. 

so that contact is made between the center and right-hand leads. For 
turbine vessels with fast running propellor shafts the gearing ratio of E 
and D is proportioned so that only one indicator is given for 3 and 4 revo- 
lutions of the main shaft. 

Telephones. 

On the latest vessels a central station is provided to which each set is directly 
connected. Fig. 18 is a diagram of the system as furnished by the Western 
Electric Co. The central board is known as the cordless and plugless 
type. Its main feature consists in having the connection circuits arranged 
in a series of horizontal bus-bars which are crossed vertically by the talking 
wires of each station, so that by putting an ordinary spring lever key at 
each intersection any desired combination of connections can be made. 
Usually the board is arranged for fifty stations and five connection circuits, 
so that five separate conversations between any five pairs of telephones 
may be carried on at the same time; also for issuing general orders any 
desired number of telephones may be connected together. The diagram 
shows only two connection circuits and two stations, but it can be extended 
as desired in either way. 

The operation is as follows: 

Three wires run to each station, two for talking and one for ringing. 
When the receiver is taken off the hook, current from the talking battery 
flows through the talking line wires and displays the line signal. When 
the operator throws one of the connection keys of the calling set the line 
signal is cut out and the talking wires connected direct to the horizontal 
connection bus which is permanently connected to the talking current 
supply. Throwing the connection key of the party to be called, which is 
on the same horizontal bus as the calling party, puts the pair in communi- 
cation. 

Ringing is accomplished by a separate ringing key for each set, taking 
current from a separate ringing battery and operating through the common 
ringing wire and the left-hand talking wire as shown. 

Each horizontal connection bus has a clearing-out signal which is dis- 
played when current is flowing from the talking supply. When both 



INTERIOR COMMUNICATION SYSTEM. 



120? 



Qsignai ® 



Clearing-out 
Signal 



5Li§DE 



Line 
'Signal 



Connection 

< m — 



J fl M rfe 



Connection 
/Key 




Terminals at 
Sub-<$tetion 



+ I- -I «♦ 

Talking Ringing 

Circuit. Circuit 

44* 20 y 



WTSETNS/. HW.TS£tH*2 

Fig. 18. Diagram of Western Electric General Telephone System. 



1208 ELECTRICITY IN THE UNITED STATES NAVY. 



parties hang up the receivers the flow of the talking current ceases and the 
signal falls back. 

A night bell is provided which is operated by a relay when any line signal 
is displayed, also when any clearing-out signal falls back and the corre- 
sponding connection keys are not opened. 

Cross-talk is prevented by choke coils (not shown on diagram) inserted 



T£L.S£TJl/9l 



Tel.SctVZ 




y. TAIXW6 CUMENT 24 VOLTS 

Fig. 19. Diagram of Holtzer-Cabot General Telephone System 

in each side of the horizontal connection busses just after their connection 
to the talking current supply. Both talking and ringing currents are 
supplied either from batteries or motor generators taking power from the 
ship's generating plant, thus giving a reserve. 

Both water-tight and non-water-tight telephones are used. The non- 
water-tight are of the ordinary wood case wall pattern, while the water-tight 
sets have the mechanism enclosed in a brass box with the cover having a 
rubber gasket and heavy clamps. 

Figure 19 shows the design made by the Holtzer-Cabot Co. The general 
scheme of operation is the same as above described, the main difference 



INTERIOR COMMUNICATION SYSTEM. 



1209 



being that the operator's set is handled by a separate additional row of 
keys instead of being treated simply as a station. m 

Figure 20 shows the design made by Charles Corey & Son. It is gener- 
ally similar to the above systems, but uses a separate battery for each 
talking circuit instead of using talking current from a common bus sup- 
plied by dynamo current. Also each talking circuit consists of two sets of 




. .£ RUtGW* CURRENT 

Fig. 20. Diagram of Corey General Telephone System. 



horizontal busses, and the connection keys may be thrown either way to 
connect on the station, thus making it possible to reverse the direction of 
current flow through the contacts and instruments. Each set of connection 
keys is so grouped that one lever operates them all. 

In the above telephone diagrams the following notation is used: 



T. — Transmitter 
R. — Receiver. 
L. — Line signal. 



C. — Clearing out signal. 
I. — Choke coil. 
P. — Push button. 



1210 ELECTRICITY IN THE UNITED STATES NAVY, 



IWftftftftftftftftftffftftt 













t/VUti&UUUUdUU 

RESTORING SPRING 




Fig. 21. Diagram of Connections of Electric Whistle. 



ITire Alarms. 

The fire alarm system consists of thermostats, located in all parts of the 
ship, and connected to an annunciator in the captain's office. 

The thermostats consist of a helioal metal coil, made of two strips of steel 
and brass, having a high temperature coefficient of expansion, mounted with 
one end free so that the tortional effect produced by a rise of temperature 



MISCELLANEOUS. 1211 



causes a slight displacement of the free end, thus closing the circuit and 
operating the corresponding annunciator drop. The working parts are 
enclosed in a heavy brass case. 

Coal bunker and storeroom thermostats are set for 200 degrees Fahrenheit, 
and those in magazines at 100. 

Water- tig-lit Door Alarms. 

To give a general signal for the closing of all water-tight doors, a system 
of alarm whistles is used. The whistle consists of a solenoid which pulls 
its core down into an air chamber, and thus forces the air out through a 
small shrill whistle. The core is restored by spiral springs. All whistles 
are connected in parallel, and are operated by a make and break mechan- 
ism, which by the pulling of a lever will interrupt the circuit continuously 
for about 30 seconds, each interruption giving a blast from each whistle. 
Current from the lightning mains is used. 

The construction is shown in Fig. 21. The clockworks for operating the 
contact maker is constructed so that by rotating an operating lever it is 
wound up, and upon releasing the lever it vibrates the contact while running 
down, thus giving periodical signals. 

In the latest design the whistle is inverted and pulled up against gravity, 
thus dispensing with the restoring springs. 

Call Bells. 

An elaborate system of call bells, annunciators, electro-mechanical signal 
gongs, etc., is installed on all large ships. The main difference from ordi- 
nary commercial work is that all appliances are made water-tight. 

\ 

Rang-e -finder. 

The following is a brief outline of the principles employed in the instru- 
ment designed by Lieutenant Bradley Fiske of the United States Navy. 
In Fig. 22 let A represent the target and BC & known base. Then 

AC :BC : : sin ABC : sin BAC. 

sin ABC 



AC = BC X 



sin BAC 



The angle ABC can be readily measured. The angle BAC ■* DBE, the 
line BE being parallel to AC. 

The Fiske range-finder measures the angle DBE by the use of the Wheat- 
stone bridge, as follows: 

Suppose the two semi-circles in Fig. 22 replaced by two metallic arcs (Fig. 
23). At the center of each of these arcs is pivoted a telescope, the pivot of 
which is connected to a battery B. The telescopes are in electrical contact 
with the arcs. These metallic arcs are connected at their extremities with 
a galvanometer, c, the whole forming a Wheatstone bridge, whose arms are 
aa bb. 

When the telescopes are pointed at the object A, it is evident that the 
arms of the bridge are unequal, and hence do not balance; and this fact is 
indicated by the deflection of the needle of the galvanometer. The arc FD 
is noted. By swinging the telescope at F around till the needle of the 
galvanometer indicates zero, the bridge balances, the telescope being 
parallel to the one at C, and the arc or angle DF — FE is equal to the 
angle at A. From this the distance AC can be calculated, or read off 
directly on a properly constructed scale. 

Generally, in using the instrument, the telescopes are mounted at a 
distance from the battery, where the view is uninterrupted, while the gal- 
vanometer is at the gun. The observers keep the telescopes constantly 



1212 ELECTRICITY 1ST THE UNITED STATES NAVY. 

directed on the target, and the man at the gun balances the bridge by in- 
troducing a variable resistance into the circuit till the needle stands at 




Fig. 22. 



Fig. 23. 



zero. This variable resistance is graduated so as to indicate the range 
corresponding to the resistance introduced. This instrument is not now used. 

firing- Guns. 

Large guns are arranged to use both percussion and electric primers for 
firing. The electric primer is of the same external shape as the percussion 
primers, and is exploded by a fine platinum wire, heated by current from 
the cells of a dry battery mounted near the gun. A ground return is used 
and a safety switch is fastened to the breech plug, so that the circuit can- 
not be completed until the breech plug is closed. A push-button is used to 
complete the circuit and fire the gun. 

The same primer is also used for igniting the charge of powder to expel 
torpedoes from their directing tubes. Fig. 24 shows a section of the primer 
and diagram of connections for both torpedo and gun firing. In torpedo 
firing the opening of the sluice gate, which permits the torpedo to be dis- 
charged from the tube, closes the circuit and operates the signal lights at 
the tube and firing key. This also acts as a safety device by preventing 
the primer being fired before the gate is opened. 



Speed Recorder. 

An instrument called the "Weaver Speed Recorder" is somewhat used 
for measuring the speed of ships when run on the measured mile, and while 
being launched; also to measure the acceleration of turrets during test. 

It consists essentially of a clockworks, which drives a paper tape over a 
set of five pens operated by electromagnets, so that when any magnet is 
excited it pulls its pen against the moving paper tape, and makes a dot 
thereon. The connecting levers between the magnet and pen are arranged 
something like a piano finger action, so that no matter how long the magnet 
is kept excited, the pen will only make a quick, short dot. All pens are 
located side by side in the same line, so that if they were all operated at 
the same instant, the result would be a line of dots across the tape. 

When used for measuring mile runs, one pen is connected to a make and 
break chronometer, so that it makes a dot on the tape every second; an- 



MISCELLANEOUS. 



1213 



other pen is connected to a hand push-button, so that a dot can be made at 
the start and finish of the run, and at as many intermediate points as de- 
sired; the other three pens are connected to contact makers on the shafts 
of the main engines, so that a dot is made for every revolution of the en- 
gine. (If the ship has twin screws, of course only two of the remaining 
pens are used and if single screw, only one.) 

It is thus seen that by counting the number of second dots between the 
Btart and finish dots, the length of time to make the run is given, and by 




INSULATION 



SECTION OF PRIMER, 




SLUICE GATE 
CIRCUIT CLOSER 



A 



INDICATOR 
LAMP 



PILOT LAMP 
AT TUBE 



^T 



FIRING KEY 

RESISTANCE 
PRIMER 




CONNECTIONS FOR TORPEDO TUBE FIRING. 



j? 



FIRING KEY 



**, SAFETY 
SWITCH 



"^T BATTERY 



PRIMER 




Fig. 24. Connections for Torpedo and Gun Firing. 



1214 ELECTRICITY IN THE UNITED STATES NAVY. 



counting the number of revolution dots in any desired space, the speed of 
the engine is given. Fractional seconds or revolutions can easily be scaled. 

When used to obtain launching curves, a long steel wire wound on a drum 
has one end attached to the ship, and a contact maker is fastened to this 
drum. As the ship slides out the drum is revolved and dots made on the 
tape at each revolution; knowing the diameter of the drum, the speed at 
any instant is found by comparison of the revolution dots with the second 
dots. The hand-push is used to mark the start, finish, instant of pivoting, 
and any other desired matters. 

When used for acceleration runs on turrets, the same procedure as for 
launching curves is followed, except the contact maker is attached to some 
rotating part of the turret mechanism. 



RESONANCE. 

^Revised by Lamar Lyndon. 

If in an alternating current circuit, an inductance be inserted, the self- 
induced E.M.F. will combine with the impressed E.M.F. and the resultant 
of the two will be the active E.M.F. which causes current flow. The current 
will always be exactly in phase with and proportional to the resultant E.M.F. 

The inductive E.M.F. is 90 degrees, or one-fourth of a cycle, behind the 
current, and, therefore, behind the resultant E.M.F. which is in phase with the 
current. The algebraic sum of the instantaneous values of the resultant and 
inductive E.M.F.'s will give the corresponding values of the impressed E.M.F. 

Fig. 1 shows this summation. v,v,v,v, is the resultant EJM.F. re- 
quired to send current i,i,i,i, which is in phase therewith, through a given 
resistance. L,L,L,L, is the curve of E.M.F. necessary to overcome the 
counter E.M.F. of the inductance, the curve of the inductance E.M.F. being 
equal and opposite to the curve L,L,L,L. This curve of inductance E.M.F., 
which is indicated by the dotted curve 1,1,1,1, is one-quarter period or 90 
degrees behind the current and the resultant E.M.F. Combining the ordi- 
nates of v,v,v,v, and L,L,L,L, the curve e,e,e,e is produced. This represents 
in phase and magnitude the impressed E.M.F. required to send current i,i,ii, 
through the resistance and overcome the counter E.M.F. of the inductance* 




As may be seen, it is somewhat in advance of the resultant E.M.F. and, 
therefore, of the current. Also it is higher than the resultant E.M.F. by an 
amount which at each instant is equal to the counter E.M.E. of the in- 
ductance. 

If a condenser or capacity be included in a circuit, and an alternating 
current be sent into it, flow will take place in the condenser, the current 
entering and charging it. As the amount of electricity stored increases, 
the E.M.F. of the condenser increases also until the impressed and con- 
denser E.M.F.'s are equal. The condenser E.M.F. being a counter pressure, 
current flow ceases when the two E.M.F.'s balance. The current being 
aero at this point, and the condenser E.M.F. a maximum, it may be seen 
that the condenser E.M.F. is one-quarter period or 90 degrees in advance 
of the current, and, therefore, of the resultant E.M.F. 

In Fig. 2, F,7,F,7, is the resultant E.M.F. made up of the two E.M.F.'s 
acting on the circuit. i,i,hi, is the current, C,C,C,C, the condenser E .M.F., 

1215 



1216 



RESONANCE. 



which is 90 degrees ahead of i,i,i,i. c,c,c,c, is the curve of F.M.F. necessary 
to overcome the condenser E.M.F., being equal and opposite to the condenser 
E.M.F. Combining V, V, F, F, and c,c,c,c, the impressed E.M.F. curve e,e,e,e, 
is produced, which is somewhat behind the current and resultant E.M.F., and 
behind the condenser E.M.F. Also, the impressed E.M.Fo is greater than the 
resultant E.M.F. 

From the foregoing it is evident that if either a capacity or inductance 
be inserted in an alternating current circuit, the phase of the current with 




respect to the impressed E.M.F. will change, and the current flow be re- 
duced. Since the one sets up an E.M.F. 90 degrees in advance of the cur- 
rent flow and the other a pressure 90 degrees behind it, the two effects tend 
to neutralize each other when connected in series, and when they are just 
equal, no E.M.F. other than the impressed is left to act on the circuit, 
the resultant and impressed E.M.F .'s are identical, and there is no phase dis- 
placement. This condition is called resonance and is shown in Fig. 3. 




Fig. 3. 



The curves L,L,L,L, and c,c,c,c, are equal and opposite at every instant 
and neutralize, leaving the impressed E.M.F. as the only one acting on the 
circuit. 

The conditions for resonance then are, that with a given frequency and 
current the capacity and inductance be so related that the counter E.M.F. 's 
set up by them are equal, or it may be stated another way. If in an alter- 
nating current circuit an inductance and a capacity be connected in series, 
either of which, if inserted in the circuit alono, reduces the current flow the 
same amount, resonance occurs and the current flow is not changed by the 
presence of the two in series. 



RESONANCE. 1217 

The formula for alternating current flow in a circuit containing resistance, 
inductance and capacity is 

E 

(i) 



y/^ + (z w _J_y 



in whioh E = E.M.F.. (impressed volts), 

i= Current in amperes, 
jR — Resistance in ohms, 
L = Inductance in henrys, 
J= Capacity in farads, 
<o = 2 nf z= 6.23 x frequency in cycles per second. 

If the capacity and inductance effects neutralize, 

Leo = — T » and Zu> T = 0, (2) 

OiJ UiJ 

and formula (1) becomes 

/=-^L = -, (3) 

which is simply Ohm's law, showing that the current flow is opposed only 
by the resistance. 

The farad is too large a unit for practical work, capacities seldom being 
more than a few micro-farads (or one millionth of a farad). If / be taken 
in micro-farads and called Jm, then for resonance 

T _ 1,000,000 



.-,/! 



LJm 

also w = 2 tt/. 

Therefore, /= 1 /iWOOO, 

2 7T j LJm 



1,000,000 

(4) 



(5) 



which is the frequency at which resonance will occur for a capacity Jm 
and an inductance L. Since the opposing E.M.F. of the inductance in- 
creases with increase of frequency, and that of the condenser decreases, 
with a given inductance and capacity there is only one frequency at which 
they will neutralize and resonance result, and if this frequency be changed, 
the E.M.F. of one will increase while that of the other will decrease, thus 
destroying the balance between the two. 

As an example, assume a circuit having an inductance of 0.44 henry, 
and a capacity of 16 micro-farads. For resonance the frequency must be 

. 1 /l, 000,000 _ A . , 

/= 2^ V 0.44 x 16 = °y cles ' P er second - 

The opposing inductance and capacity E.M.F/s often set up local poten- 
tials very greatly in excess of the impressed. 

Since the voltage required at the terminals of an inductance to force a 

W 
given current through it =r B t t± wLI, and for resonance, 1=-^ the voltage 

at the inductance 

= tf,= ^. <«> 



1218 



RESONANCE. 



Also the voltage required to send a given em-rent through a condenser — 



-, or 



I X 1,000,000 _ E X 1,000,000 



u>J m ~~ RaJm 

Assume the circuit of 0.44 henry 16 micro-farads and 5 ohms. 
/ = 60 cycles, 
Impressed E. M. F. = 250 volts, 

the voltage at the terminals of the inductance, 
250 X 0.44 X 2tt X 60 



(7) 



* = - 5 

while the volts at the condenser terminals 
250 x 1,000,000 



= 8290 volts, 



-Ec — 



5x2ttx60x16" 



: 8290 volts, 



which is the same as the voltage at the terminals of the inductance. 

Fig. 4 shows the diagram of such a circuit and indicates the potentials 
between the different terminals. 



0.44 HENRV 




From the foregoing it is obvious that the smaller the resistance, the 
greater will be the local voltages set up by the capacity and inductance. 
For instance, if in the previous example the resistance were 2\ ohms 
instead of 5 ohms, the current flow would be 100 amperes and the poten- 
tial at the terminals of the inductance and of the condenser would be 
16,580 volts, the impressed E.M.F. being only 250 volts as before. 

In practice the capacities and inductances are seldom so related as to 
allow complete resonance to occur at commercial frequencies, though when- 
ever a capacity and inductance are in series the partial neutralization 
which takes place is liable to increase the E.M.F. locally to a higher value 
than that of the impressed. 

All the foregoing is based on an impressed E.M.F., which is a pure sine 
function. 

In practice, however, the E.M.F. wave differs more or less from this 
form, and may be considered as the resultant of several pure sine waves 
of varying amplitudes and frequencies. Those waves which have a higher 
frequency than the impressed E.M.F. wave, are termed higher or upper 
harmonics. Although the frequency of the impressed E.M.F. may not be 
sufficiently high to produce resonance, some one of the component waves 
or "upper harmonics" may have a frequency at which resonance will re- 
sult. From equations (6) and (7) it is clear that, with a given resistance 
in circuit, the rise in E.M.F. due to resonance is proportional to the im- 
pressed E.M.F., and since the voltage of the upper harmonics is usually 
small, the rise in E.M.F. cannot be great. 

When resonance occurs with one of the upper harmonics, the wave form 
of the current becomes greatly distorted, because while the other compo- 
nent waves must force the current against both the resistance and the 
reactance (i.e., inductance and capacity E.M.F.'s), this particular wave 



RESONANCE. 



1219 



has only to overoome the ohmio resistance and, therefore, sends a greater 
current through the circuit in proportion to its voltage than do the other 
E.M.F. waves. 

All these considerations apply only to circuits in which the inductance, 
resistance and capacity are in series. If the inductance and capacity be 
connected in parallel, as shown in Fig. 5, there can be no rise of voltage 
above the impressed even if the two be in resonance, but currents greater 
than those supplied by the source of impressed E.M.F. may surge back 
and forth through the local circuit, joining the condenser and the induct- 
ance, and, unless the resistance be high, the current sent through the main 




flip 



s 

6 



Fig. 5. 

circuit will be greatly reduced: indeed, if the resistance were zero, the alter- 
nator could not send any current whatever through the circuit, for at every 
value of the impressed E.M.F. there would be an equal and opposite E.M.F. 
either from the condenser or inductance, and the resultant or active E.M.F. 
becomes zero. This condition is represented in Fig. 6 in which the curve e 
represents the impressed E.M.F. c is the curve of condenser current, and 
L of current in the inductance. The condenser current is 90° in advance 
of the impressed E.M.F. while the inductance current is 90° behind it, 




Fig. 6. 



there being no resistance in the circuit. The sum of the two currents then 
is always equal to zero, as may be seen. 

The physical conception of this condition is that of current flowing into 
the condenser, charging it, while the previous stored energy in the induct- 
ance discharges. This discharge sets up an E.M.F. opposing the impressed 
E.M.F., and also furnishes the current supply to charge the condenser. 
On reversal of the impressed E.M.F. the condenser discharges into the 
inductance, at the same time setting up a counter E.M.F. to oppose the 
flow of current from the line. 



1220 RESONANCE. 

Thus, although there may be heavy currents flowing in the branch cir- 
cuits, none will flow through the main circuit. In practice there is always 
a certain amount of resistance present in both of the branches, which will 
displace the phase relations of the two currents so that some current will 
flow in the main circuit, but this will often be less in amount than if one 
only of the two reactances were present when the resistances are very 
small. 

As an actual case, consider the branch circuit shown in Fig. 5. Branch 
A has an inductance of .02 henry and 5 ohms resistance. Branch B has 
a capacity of 50 micro-farads, and a resistance of 8 ohms. Frequency = 100 
cycles per second, and impressed E.M.F. z=z 100 volts. 



Impedance of branch A = V(5) 2 + (6.28 X 100 x .02)2 — 13.5, 

Current through branch A = — — = 7.42 amperes. 
13.5 

Tan. angle of lag = ^ X 100 X .02 = 2.512, 
corresponding to an angle of 68° — 18'. 

Impedance of branch B= J®F.+ ( 6 J'^ X 5Q ) = 32.83. 

100 
Current through branch B = — — - — 3.05 amperes. 
oZ.oo 

1,000,000 

Tan. angle of lead = 628 ^ ^ = 3.98, 

o 

corresponding to an angle of 75°— 54'. 

Combining these two currents in their proper phase relation, the sum is 
the current through the main circuit. This can best be done graphi- 
cally after the usual manner of combining E.M.F. 's or 
currents vectorially. 

In Fig. 7 let the horizontal line OE represent the im- 
pressed E.M.F. and be the reference line. From O at an 
angle of 68° — 18" upwards lay off 7.42 amperes to any 
suitable scale. At an angle of 75° — 54" downward, 
lay off 3.05 amperes. Complete the parallelogram, as 
indicated by the dotted lines. The diagonal from Ogives 
the value of the resultant current through the main 
circuit as 5.24 amperes, and shows also that it is behind 
the impressed E.M.F. by 48° - 36". This, it will be 
seen, is less current than would flow through the circuit 
by branch A if the parallel branch B were entirely 
removed. 

If the reactance E.M.F.'s have the same value, the 
capacity being .00005 farad (=50 micro-farads), the 
inductance will be equal to .0506 henry. Assume that 
the resistance in branch B remains as before. If the 
resistance in branch A be 25 ohms the impedance will be = 

^(25)2 +(31.83) 2 = 40.47 and current = ~^ =2.48 

31 83 
amperes. Tan. of the angle of lag = — ~- = 1.271, 

corresponding to 51° — 49". Combining these values 
with the 3.05 amperes at an angle of lead of 75° — 54" in Fig. 8, the result- 




RESONANCE. 



1221 



ant current is 2.49 amperes, and has an angle of lead = 
current is less than that in branch B alone. 

For the currents in two parallel branches 
to balance each other, so that the resultant 
current through the main circuit is brought 
in phase with the impressed E.M.F., the 
following condition must exist. 

The amperes flow through one branch, 
multiplied by the sine of the angle of lead or 
lag of the current (referred to the impressed 
E.M.F.), must be equal to the amperes through 
the other branch multiplied by the sin of 
its angle of lag or lead. That is: 

I± x sin <f>=zl 2 x sin »//, in which I t and I 2 
are the currents through the two branches, 
<f> is angle of lag of I x and »// is angle of lead 
oil.. 

If in branch B of two parallel circuits the 



4° - 24". This 



and 



Impressed E.M.F. = E, 

Capacity =. <7, 

Resistance = E, 



the impedance z= 1/ B?-\- i — = j , 
w being 6.28 X frequency. 

The current =: - 




vM^r 



Fig. 8. 



Tan of the angle of lead = -=-, 

from which the angle and its sine are found. In branch A, either the resist- 
ance or reactance must be known. Calling I 2 the current and \p the angle 
of lead in branch B, l x the current in branch A, and <j> its angle of lag, 



I 2 sin \fj : 
Tan <f> : 



: I± sin <£, 
sin tf> 






\/l — sin2 ^ 

where i?i is the known or assumed resistance in branch A. 
RJ X sin2 </> — i2 w 2 (i _ s i n 2 </>), 



whence 



• ^ 1 / L2 « 



Z2u>2 



E 



I x sin <f> = 

Calling I 2 sin \jj = 0, and solving, 

Bui = 



ELm 



Rj + L2oj2 



= I 2 sin v//. 



20 : 



■V: 



Ei 



■ JV- 



(8) 



(9) 



(10) 



(11) 



~P"i 
When BJ is equal to or greater than — -£ the quantity under the radical 

becomes zero or negative, and there is no reactance which will compensate 
for the effect of that in the other branch, the resistance being too high. 



1222 RESONANCE. 

The sign before the radical being either plus or minus, there are two values 
of reactance with a given resistance which will compensate (if R x be not too 
great) . The lesser reactance will, of course, permit the greater current flow, 
both through branch A and the main circuit. 

As an example, assume a resistance of 8 ohms, a condenser capacity of 
50 micro-farads in branch B ; also a frequency of 100 cycles per second, im- 
pressed E.M.F. = 100 volts, and a resistance of 10 ohms in branch A. What 
inductance must be inserted in branch A to compensate for the reactance in 
branch B ? Amperes through branch B =z I 2 =z 3.05. Angle of lead = 75° 
54" = f. Sini// = .9"~ 



I 2 sin xjy = 3.05 X .96987 = 2.9581 = 9. 
Substituting in formula (11) 



iu = 10 ° +J < 100 > 2 (10P 

2 X 2.9581 I V4X (2.9581)2 v ' 

•La = 16.902 ± 13.614=; { ^ J^? • 
Tan* = f!. 

3 288 
Taking the first value, Tan <f> = -^— = . 3288, 

corresponding to an angle of 18° — 12", 

sin <f> = .31233. 

100 

Current through A = = 9.47 amperes. 

VtlO) 2 + (3.288)2 
J sin £ = 9.47 X .3123 = 2.9567, 

which (within the limits of tabulated values of functions of angles) checks 
with the value of / sin \\i. 




Fig. 9. 

The resultant current in the main circuit is found graphically — shown by 
full lines in Fig. 9 — to be 9.75 amperes, and in phase with the impressed 
E.M.F. 

If the greater value of Lia be taken, 

Tan ^ — SJ^l— 3 0516 — 71 o _ 50 ", 

sin (/> — 0.95015. 

100 
Current through branch A = , = 3.12 amperes. 

V(10) 2 + (30.516)2 

/, sin <f> = 3.12 X 0.95015 = 2.964, which checks with I 2 sin vj/ (within limits of 
tables of functions of angles). 



RESONANCE. 1223 

Resultant current is found graphically, as shown by dotted lines in Fig. 9, 
to be 1.72 amperes, and is in phase with the impressed E.M.F. 

From the foregoing equations it can be seen that if Lot be known and R x 
is the quantity to be determined, 

b 1 = sJl^I^-l^Y (12) 

If R. and L of branch A, and R^ of branch B are known, the capacity re- 
quired in branch B is found from the formula, 

1,000,000 
Jm = ! , (13) 

in which B st I x sin <£. 

If R x , L, and Jm be known, 

D /i,ooo,ooo 77? 1,000,000 \ 

If .7 be taken in farads, formula 14 becomes, 



THE ELECTRIC AUTOMOBILE. 

Revised by Alexander Churchward. 

The Electric Automobile has proved itself successful for delivery service 
in cities and locations where the roads are good and the distance traveled 
per day is from fifteen to fifty miles, the distance being decreased in pro- 
portion to the, loads carried. See Motor World, 1909. 

Where the ''distance traveled per day under ordinary road conditions is 
less than ten miles and the speed low, the service can be performed at a 
lower cost with horse drawn vehicles. 

Where the distance traveled per day is greater than fifty miles for the 
lighter vehicles and twenty-five for the heaviest type, the gasolene electric 
gives better results than those whose source of energy is a storage battery. 

The above statements should be taken as applying to general conditions. 
Where the conditions are in any way special or severe, cost of operation by 
each of the three systems should be carefully computed. 

Owing to the cost of a horse and wagon being less than a motor driven 
vehicle, a certain amount of work must be performed each day before the 
efficiency of the automobile becomes apparent. 

The actual cost of gasolene is generally found to be greater per vehicle 
mile than the cost of charging storage batteries of automobiles for equal 
loads over the equal distances within the limits above given. Certain 
limits to daily travel will therefore be found when each type of trans- 
portation is cheapest. 

(For a more detailed discussion, see Motor World on "Improvement of 
the Electric Vehicle," May 14, 1908. "Commercial Vehicle Problems," — 
Motor World, Oct. 1, 1908. "The Horsepower of the Horse," — Motor 
World, 1908. 

Resistance Hue to Gravity, and Power Required. 

W. Worby Beaumont. 

The horse-power required to overcome weight, speed, road resistance, 
gravity resistance, and efficiency of transmission between armature shaft 
and road wheel, may be found as follows: 

Let R = the resistance to traction of the vehicle on the road in pounds 
per ton. 
G = the resistance due to gravity in pounds per ton. 
W = total weight on the wheels in tons. 
V = speed in feet per minute. 
v = speed in miles per hour. 

E = mechanical efficiency of transmission from armature shaft to road. 
P = brake horse-power. 
e = efficiency of motor. 
p = watts supplied to motor. 

p {R + G)WV m _ PE 375 } 

P= 33,000 E ' (1) V -(R + G)W' (5) 

(R + G)Wv PE 375 

P - 375 E ' (2) W {R + G)v* W 

CB + ^-^trt' (3) v= 746 7* (7) 

(R + G)vW 
E ~ P375 ' (4) 

For a more detailed discussion of the mechanics of traction see Electric 
Traction. 

1224 



TIRES. 



1225 



Resistance to Traction on Common Roads. 

W. Worby Beaumont. 



Road Surface Material. 



Asphalt 

Wood, hard 

" soft 

Macadam, very hard and smooth .... 

good 

traffic rolled, wet 

steam rolled, new and muddy . 

new, flat spread 

Gravel 

Granite tramway "... 

Iron plate tramway 



Resistance in Lbs. per Ton. 



On 




On 


Iron-tired 


Solid Rubber 


Wheels. 


Tires. 


22 to 28 


35 


to 40 


22 ' 


4 26 


40 


44 45 


30 * 


* 38 






40 


* 45 


35 


44 40 


45 


4 52 






52 


4 58 






58 ' 


4 62 






95 ' 


4 105 






100 * 


4 140 






12.5 4 


4 15 






10 * 


4 12 







In most cases these resistances increase slowly at higher speeds, and it 
must also be noted that the resistance on bad, soft, and gravel roads will 
probably be greater with propelling wheels than with most hauled wheels. 
Most of the figures relate to road resistance at walking or slow trotting 
pace. 

Tires. 

Solid rubber tires have a higher resistance than steel tires on asphalt 
roads and have less resistance on macadam and other roads. The per- 
fectly smooth surface of the asphalt produces a drag on the rubber tires, 
thus increasing their resistance. Pneumatic tires are best adapted to 
roads with slight inequalities, and for pleasure cars run at high speeds. 
For both solid and pneumatic tires, the draw-bar pull required to over- 
come the rolling resistance depends on the speed. This subject has been 
investigated by Mr. Alex Churchward, and the results of his tests* are 
reprinted below: 



Material of Road. 



Asphalt 

Macadam . . . . 
Macadam . . . . 
Belgium block . . 

Asphalt 

Macadam . . . . 
Asphalt and brick 
Asphalt 



Grade. 



Level 
1.1% 

Level 

9.5% 

4.7% 

3.75% 

3.125% 

2.25% 



Draw-Bar 


Miles 


Type of 


Pull in Lbs. 


per Hour. 


Tire. 


24 


12 


Solid 


37 


12 


Pneumatic 


48 


11 


Solid 


66 


10.6 


Pneumatic 


29 


12 


Solid 


44 


12 


Pneumatic 


250 


5 


Solid 


270 


5 


Pneumatic 


132 


7 


Solid 


150 


7 


Pneumatic 


114 


8 


Solid 


128 


8 


Pneumatic 


95 


8.5 


Solid 


119 


8.5 


Pneumatic 


85 


8.8 


Solid 


103 


8.8 


Pneumatic 



* See The Commercial Vehicle, April, 1906. 



1226 



THE ELECTRIC AUTOMOBILE. 



The above figures are averages of reading^ taken for a great many vehicles. 

The difference in the consumption of power when running on wet and dry 
pavements was discovered to be so small that the additional tractive effort 
required when the pavements are wet may be neglected. 

The temperature of the asphalt greatly affects the consumption of energy. 
In one case a difference of 40 per cent was found in the power required for 
operating a car on cold and on warm asphalt. 

Tractive efforts of 119 pounds per ton for two inches of sand and 138 
pounds per ton for muddy roads were obtained. 

I 



Vo | — ■ — I II 1 ' ' 1 






: : z 




/ 




— r 


70 


- Zt -j. 




- z _/ 




Z/ Jl 




Z- -t 


__ 


-/ -/ 




z z 




/ 4 




-/ -T 




-/ z 




Z JL 




A J 




-f z 




-f / 




Z jl 




A -X 




S 7 




-/ -/ 




: z _/ 




4ST J ZZZZZZZ 


50 


I£? y I 




J& JL Z 




-J& z 




Z&C J&z 




: J^Jk. 




f<y /F^ 




/& /■$ 




\ ffi 


/ 




r 








40 2 - 




A 




/ 




/ / 


4_ _ _ 


u <- z z: 




5* I j - 




^ -t J - 




\ J z I 




^ z jl : 




io s ^ Z J . 




3U I>£-2- z 




i : 




t 




"\ Z 




25 V Z 




^c- -/ 




s y 




\? 








20 ' ' 1 1 1 1, 1 1 , 1 1 11 1 1 1 — LI — L 





10 12 11 16 18 20 22 24 26 28 30 32,34 36 38 AQ 42 44 

Speed in Miles per. Hour 
Fig. 1. 



Results of tests for the tractive effort at several speeds are shown by the 
curves in Fig. 1. It will be noticed that the draw-bar pull diminishes as 
the speed is reduced, to a minimum, and increases as the speed is still further 
reduced. The speed in miles per hour at which the minimum point occurs 
varies with different weights of vehicles, diameter of wheels and types of tires 
used. 



BATTERIES. 



1227 



Motors. 

The present general practice is to install one series-wound motor on all 
except the very largest trucks. However, under certain conditions of road 
bed and the type of tires used, it may be advantageous to use even a four- 
motor four-wheel drive. Usually, however, under fair road conditions, one 
large motor has proved more efficient than a number of smaller ones. 

A normal voltage has been adopted at 80-85 volts to correspond with the 
minimum discharge voltage of batteries adapted to 110-115 volt charging 
circuit. Some of the motors are designed for operation at increased speeds 
by shunting the fields with a resistance, especially on the higher speed pleas- 
ure vehicles. This practice is considered preferable to commutating the 
batteries. 
Controllers. 

In the past few years, the number of speed points has been almost doubled, 
combining this with the latest type of control by the continuous torque 
system; the handling of a vehicle is now smooth and more efficient. There 
is no perceptible jar or shock when going from one speed point to another 
and the result is that the maintenance of the entire vehicle has been con- 
siderably reduced. 
Batteries. 

The standard equipment for the wagons and trucks is 44 cells of the lead 
type of storage battery or 60 cells of the Edison type and of a suitable 
ampere capacity. These numbers permit of charging from the lighting 
companies' feeders at 110-115 volts with a minimum loss in the charging 
rheostat. Runabouts and other very small vehicles are equipped with 
24 or 30 cells of moderate ampere capacity, as a saving in weight is thereby 
obtained over 44 cells of smaller ampere capacity that more than offsets the 
loss in the charging resistance. A battery can be supplied to meet almost 
any requirement of travel in miles per day, but it is generally found that the 
weight of battery required for distances above 50 miles per day for light 
commercial vehicles and 25 miles per day for the heaviest so reduces the 
efficiency of the automobile as a whole that the gain over other methods of 
transportation is not so marked as it is with the battery of standard size. 

The following lists of batteries may be used as a guide in selecting those 
for any equipment: 

The Electric Storage Battery Company, 



Type MV "Exide." 


Type PV 
"Exide." 


Number of plates . . . 


7 


9 


11 


13 


15 
49 


17 
56 


19 
63 


21 
70 


5 
12 


7 
18 


9 
24 


11 


Discharge in amperes for 4 
hours 


21 


28 


35 


42 


30 


Size of plates: 

Width 

Height 


If 


5| 

8| 


51 

8| 


51 

81 


51 

8f 


5i 

8f 


5i 

8t 


51 

8f 


411 

81 


411 

81 


411 

81 


m 

8f 


Outside measurements of 
rubber jars, in inches: 

Length 

Width 

Height 


21 
12| 


3* 

12| 


41 
6i 

12f 


5 

61 
12f 


5f 

6i 
12f 


el 
12| 


71 

6i 

12| 


8 

6£ 
12f 


2 
5& 

m 


2f 

fft 


3* 
5& 
11* 


41 

fft 



Allow f inch above the top of jars for straps. 



Weight in pounds: 
Element . . 
Electrolyte 
Complete cell 



18* 
2* 
22 



23* 
31 

281 



281 

31 

35i 



34 

4* 
41 



39 

5 

461 



44 
53* 



491 

61 

601 



541 

7 



10 

1 

141 



14 

2 

191 



18 
3* 



22 
5 



241 291 



1228 



THE ELECTRIC AUTOMOBILE. 



(Would Storag-e Battery Company. 





Type EP. 


Type TP. 


Type NP. 
Plates 




Plates 


Plates 




51 X 8i 


5f X 81 


4f X 81. 


Number of plates . . 


11 


13 


15 


17 


19 


7 


9 


11 


13 


5 


7 


9 


11 


Discharge in amperes 




























at four-hour rate . 


42 


49* 


57 


64* 


72 


21 


28 


35 


42 


12 


18 


24 


30 


Capacity at four-hour 




























rate of discharge 


168 


198 


228 


258 


288 


84 


112 


140 


168 


48 


72 


96 


120 


Outside dimensions 




























of rubber jar in 




























inches: 




























Length .... 


5 


51 


6* 


71 


8 


21 


3* 


41 


5 


2 


21 


3* 


41 


Width 


6* 


6* 


6* 


6* 


6* 


6* 


6* 


6i 


6i 


5& 


5A 


5^ 


5 T 6 * 


Height .... 


12 


12 


12 


12 


12 


12 


12 


12 


12 


12 


12 


12 


12 


Weight of cell complete: 




























Pounds .... 


45 


53 


61 


69 


77 


24* 


31* 


38* 


45* 


14i 


191 


241 


291 



To height of jar add * inch for straps, and 1 inch for bottom of tray. 



Rules for the Proper Care of Batteries. 

A battery must always be charged with direct current and in the right 
direction. 

Be careful to charge at the proper rates and to give the right amount of 
charge; do not undercharge or overcharge to an excessive degree. 

Do not bring a naked flame near the battery while charging or immediately 
afterwards. 

Do not overdischarge. 

Do not allow the battery to stand completely discharged. 

Voltage readings should be taken only when the battery is charging or 
discharging; if taken when the battery is standing idle they are of little or 
no value. 

Do not allow the battery temperature to exceed 100° F. 

Keep the electrolyte at the proper height above the top of the plates and 
at the proper specific gravity. Use only pure water to replace evaporation. 
Never add acid except under conditions as explained in the instructions. 

Keep the cells free from dirt and all foreign substances, both solid and 
liquid. 

Keep the battery and all connections clean; keep all bolted connections 
tight. . 

If there is lack of capacity in a battery, due to low cells, do not delay in 
locating and bringing them back to condition. 

Do not allow sediment to accumulate to the level of the plates. 



ELECTROCHEMISTRY. - ELECTRO- 
METALLURGY. 

Revised by Professors F. B. Crocker and M. Arendt, 
of Columbia University. 

jsiJECTitociiEnisriti:. 

Electrolysis : The separation of a chemical compound into its constit* 
uents by mean3 of an electric current. Faraday gave the nomenclature 
relating to electrolysis. He called the compound to be decomposed the 
Electrolyte, and the process Electrolysis. The plates or poles of the battery 
he called Electrodes. The plate where the greatest potential exists he called 
the Anode, and the other pole the Cathode. The products of decomposition 
he called Ions. 

Lord Rayleigh found that a current of one ampere will deposit 0.017253 
grain, or 0.001118 gramme, of silver per second on one of the plates of a sil- 
ver voltameter, the liquid employed being a solution of silver nitrate con- 
taining from 15 per cent to 20 per cent of the salt. 

The weight of hydrogen similarly set free by a current of one ampere is 
.00001044 gramme per second. 

Knowing the amount of hydrogen thus set free, and the chemical equiva- 
lents of the constituents of other substances, we can calculate what weight 
of their elements will be set free or deposited in a given time by a given 
current. 

Thus the current that liberates 1 gramme of hydrogen will liberate 7.94 
grammes of oxygen, or 107.11 grammes of silver, these numbers being the 
chemical equivalents for oxygen and silver respectively; the chemical 
equivalent being the atomic weight divided by the effective valency. 

To find the weight of metal deposited by a given current in a given time, 
find the weight of hydrogen liberated by the given current in the given 
time, and multiply by the chemical equivalent of the metal. 

Thus: Weight of silver deposited in 10 seconds by a current of 10 amperes 
= weight of hydrogen liberated per second X number seconds X current 
strength x 107.11 = .00001044 x 10 X 10 X 107.11 = .1118 gramme. 

Weight of copper deposited in 1 hour by a current of 10 amperes = 
.00001044 x 3600 X 10 X 31.55 = 11.86 grammes. 

Since 1 ampere per second liberates .00001044 gramme of hydrogen, 
strength of current in amperes 

_ weight in grammes of H. liberated per second 
"" .00001044 

weight of element liberated per second 

"" .00001044 x chemical equivalent of element 

Resistances of Dilute Sulphuric Acid. 

(Jamin and Bouty.) 



< 





Ohms per c.c. at 


Ohms per 


Cu. In. 


at 


Density. 


u 
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1.1 


1.37 


1.04 


.845 


.737 


.540 


.409 


.333 


.290 


1.2 


1.33 


.926 


.666 


.486 


.524 


.364 


.262 


.191 


1.25 


1.31 


.896 


.624 


.434 


.516 


.353 


.246 


.171 


1.3 


1.36 


.940 


.662 


.472 


.535 


.370 


.260 


.186 


1.4 


1.69 


1.30 


1.05 


.896 


.666 


.512 


.413 


.353 


1.5 


2.74 


2.13 


1.72 


1.52 


1.16 


.838 


.677 


.598 


1.6 


4.82 


3.62 


2.75 


2.21 


1.90 


1.43 


1.08 


.870 


1.7 


9.41 


6.25 


4.23 


3.07 


3.71 


2.46 


1.67 


1.21 



1229 



1230 



ELECTROCHEMISTRY. 



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APPLICATIONS OF ELECTROCHEMISTRY. 



1231 



Resistances of Sulphate of Copper at 10° C. or &0° F. 

(Ewing and MacGregor.) 



Density. 


Ohms per 


Density. 


Ohms per 




c.c. 


Cu. In. 


c.c. 


Cu. In. 


1.0167 
1.0216 
1.0318 
1.0622 
1.0858 
1.1174 


164.4 
134.8 
98.7 
59.0 
47.3 
38.1 


64.8 
53.1 
38.8 
23.2 
18.6 
15.0 


1.1386 
1.1432 
1.1679 
1.1829 
1.2051 ) 
Saturated j 


35.0 
34.1 
31.7 
30.6 

29.3 


13.8 
13.4 
12.5 
12.0 

11.5 



Resistances of Sulphate of Zinc at lO C. or 50° F. 





Ohms per 




Ohms per 


Density. 






Density. 








c.c. 


Cu. In. 




c.c. 


Cu. In. 


1.0140 


182.9 


72.0 


1.2709 


28.5 


11.2 


1.0187 


140.5 


55.3 


1.2891 


28.3 


11.1 


1.0278 


111.1 


43.7 


1.2895 


28.5 


11.2 


1.0540 


63.8 


25.1 


1.2987 


28.7 


11.3 


1.0760 


50.8 


20.0 


1.3288 


29.2 


11.5 


1.1019 


42.1 


16.6 


1.3530 


31.0 


12.2 


1.1582 


33.7 


13.3 


1.4053 


32.1 


12.6 


1.1845 


32.1 


12.6 


1.4174 


33.4 


13.2 


1.2186 


30.3 


11.9 


1.4220 ) 
Saturated j 


33.7 


13.3 


1.2562 


29.2 


11.5 



Specific resistance of fused sodium chloride (common salt) at various 
temperatures. 

Temperature Cent. 720° 740° 750° 770° 780° 
Ohms per cu. cm. .348 .310 .294 .265 .247 

Applications of Electrochemistry. 

The word electrochemistry is here used to include electrometallurgy, as 
there is no generic term for the two subjects. Electrochemistry may be 
defined as that branch of science relating to the electrical production of 
chemical substances and chemical action or to the generation of electrical 
energy by chemical action. On the other hand electrometallurgy is the 
branch of science that relates to the electrical production and treatment of 
metals. The two subjects are based upon the same principles, the theory, 
laws and data of one being applicable to the other. Hence it is proper 
and now customary to combine them under the head of electrochemistry. 

Electrochemistry may be subdivided as follows: 

A. Electrolytic Chemistry, which consists in separating or produc- 
ing other action upon chemical substance by the decomposing effect of an 
electric current or vice versa. Since the electrolyte is usually in the liquid 
state, there are: 

"Wet methods" with solution. 

"Dry methods v with fused materials. 

In the latter case the materials are maintained in a state of fusion by the 
heat due to the electrolytic current or by external heat. 



1 232 ELECTROCHEMISTRY. 

Electrolytic chemistry is applied to the following purposes: 

1. Primary batteries, including various forms of voltaic cell in which 
electrical energy is generated by chemical action. 

2. Secondary or storage batteries are similar to the foregoing, but the 
chemical action must be reversible, so that after periods of working the cell 
may be charged or brought back to an active condition by sending through 
it a current opposite in direction to that which it generates. 

3. Electrotyping is the art of reproducing the form of type and other 
objects by electrodepositing metal on the object itself or on a mold ob- 
tained from it. 

4. Electroplating is the art of coating articles with an adherent layer of 
metal by electrodeposition, as in nickel plating. 

5. Electrolytic refining of metals and chemicals by the elimination of im- 
purities, as in the conversion of crude copper into pure metal. 

6. Electrolytic production of metals and chemicals, as in the Hall process 
for extracting aluminum from alumina dissolved in fused cryolite, and in 
the Castner process for making caustic soda and chlorine from a solution 
of common salt. 

7. Electrolytic chemical effects, such as bleaching, tanning, etc. 

8. Electrolytic chemical analysis, as in copper determination. 

B. Electro thermal Chemistry includes those methods in which 
electric current raises the temperature of materials, usually to a high degree, 
in order to produce fusion, chemical action or other effects. Since elec- 
trolysis is not desired an alternating current is generally employed. 

9. _ Chemical^ action with electrical heating, as in the production of calcium 
carbide from lime and carbon in an electric furnace. 

10. Electrical smelting consists in reducing metallic compounds at a high 
temperature produced by an electric current, as in the reduction of iron 
ore in an electric furnace, or in the Cowles, process for making aluminum 
bronze from a mixture of alumina, carbon and granulated copper. 

11. Electric fusion of chemicals, usually those that are very refractory, 
such as silica and alumina. It has been proposed to make bricks by melt- 
ing instead of baking clay; electric heat has been used in furnaces for 
melting glass. 

12. Electrical heating and working of metals consists in treating metals 
mechanically with the aid of heat generated by electric currents, as in 
electrical welding, forging, rolling, casting, tempering, etc. 

Strictly speaking, the last two applications are not chemical, but some 
chemical actions usually occur and they are similar to the others in methods 
and results, so that it is customary to consider them under the head of 
electrochemistry. 

C. Chemical Action Due to Electrical IMscharg-es. 

13. Chemical effects of electrical arcs to produce combinations of nitrogen 
and oxygen, for example. 

14. Chemical effects of electric sparks. 

15. Chemical effects of silent electrical discharge, as in the production of 
ozone. 

Historical Notes. — The first electrochemical apparatus was the primary 
battery invented by Volta in 1799. The next year Nicholson and Carlisle 
discovered the chemical action of the electric current in decomposing water. 
In 1807 Sir Humphrey Davy gave his famous lecture "On Some Chemical 
Agencies of Electricity," he having, the same year, discovered the metals 
sodium and potassium by reducing their compounds electrolytically. In 
1834 Faraday established definite laws and nomenclature for electrochem- 
istry. From 1836 to 1839 Jacobi, Spencer, Jordan and Elkington applied 
these principles to practical use in the making of electrotypes. Plante 
began the development of the storage battery in 1859. Since that time, 
but mostly after 1886, the theory and applications of electrochemistry 
have made great progress, so that now it is one of the most important 
branches of science as well as of industry. 

Primary and Secondary Batteries. — The various forms of these 
batteries may be regarded as applications of electrochemistry, but they are 
treated as special subjects in other parts of this book. 

Electrotyping'.- — To reproduce an engraving, typographical composi- 
tion, or other object, a mold of gutta percha, wax, plaster or fusible alloy 
is made from the object. If it is not a conductor it is coated with graphite 
to start the action, connection being made to it by a wire or clamp put 



APPLICATIONS OF ELECTROCHEMISTRY. 



1233 



around it. It is used as the cathode in a bath consisting of a 20 per cent 
solution of copper sulphate acidulated with 2-8 per cent sulphuric acid, 
while the best results are obtained with a current density of .2-.25 amperes 
per square inch of cathode surface. The anode is a plate of copper. The 
ordinary thickness of deposit is .01 to .03 inch. The "shell" thus formed 
is separated from the mold and backed by a filling of type metal. 

Electroplating 1 an article with an adherent coating of metal requires 
the article to be thoroughly cleaned mechanically and chemically. 

Cleaning:. — Solutions for cleaning Gold, Silver, Copper, Brass and Zinc 
are prepared as follows: 





Water. 


Nitric 
Acid. 


Sulphu- 
ric. 


Hydro- 
chloric. 


For copper and brass . . 
Silver 


100 
100 
100 
100 
100 


50 
10 

2 
3 


100 

10 

8 

12 


2 


Zinc 

Iron, wrought 

Iron, cast 


2 
3 



Lead, Tin, Pewter, are cleaned in a solution of caustic soda. 

Objects to be plated with gold or silver must be carefully and thoroughly 
freed from acids before transfer to the solutions. Objects cleaned in soda 
or those cleaned in acid for transfer to acid coppering solutions may be 
rinsed in clean water, after which they should be transferred immediately 
to the depositing solution. 

Baths for plating-. —The reader is referred to the various books on 
electroplating for particulars, as but few, and those the most used solutions 
can be referred to here. 

Solutions should be adapted to the particular object to be plated, and 
must have little if any action upon it. Cyanide of gold and silver act chemi- 
cally upon copper to a slight extent and the objects should be connected to 
the electrical circuit before being immersed. 

Solutions are best made chemically, but can be made by passing a current 
through a plate of the required metal into the solvent. 

Copper. —A good solution for plating objects with copper is made by 
dissolving in a gallon of water 10 ounces potassium cyanide, 5 ounces copper 
carbonate, and 2 ounces potassium carbonate. 

The rate of deposit should be varied to suit the nature and form of the 
surface of the object, large smooth surfaces taking the greatest rate of 
deposit. Electrotype plates must be worked at a slow rate, owing to the 
rough and irregular surface. 

Non-metallic Surfaces may be plated by first providing a conducting sur- 
face of the best black lead or finely ground gas coke. Care is required in 
starting objects of this sort, to obtain an even distribution of the metal, and 
hollow places may be temporarily connected by the use of fine copper wire. 

Copper on iron or on any metal that is attacked by copper sulphate is 
effected by an alkaline solution. One which can be worked cold is made 
up of I ounce of copper sulphate to a pint of water. Dissolve the copper 
sulphate in a half pint of water, add ammonia until all the first formed 
precipitate re-dissolves, forming a deep blue solution, then add cyanide of 
potassium until the blue color disappears. A heavy current is required with 
this solution, enough to give off gas from the surface. This solution will 
deposit at a high rate but ordinarily leaves a rough and crystalline surface, 
and will not do good work on steel. 

A cyanide solution is the most used, takes well on steel.or brass, as well as 
on iron, and permits of many variations. 

For each gallon of water use : 

Copper carbonate 5 ozs. 

Potassium carbonate 2 ozs. 

Potassium cyanide, chem. pure 10 ozs. 

Dissolve about nine-tenths of the potassium cyanide in a portion of the 
water then add nearly all the copper carbonate, which has also been dis- 
solved in a part of the water: dissolve the carbonate of potash in water and 
add slowly to the above solution stirring slowly until thoroughly mixed. 
Test the solution with a small object, adding copper or cyanide until the 
deposit is uniform and strong. For coppering before nickel plating, the 



1234 ELECTROCHEMISTRY. 

coating of copper must be made thick enough to stand hard buffing, and for 
this reason the coppering solution must be rich in cyanide and have just 
enough copper to give a free deposit. Use electrolytically deposited copper 
for anodes, as it gives off copper more freely. Regulate the current for the 
work in the tanks, and it should be rather weak for working this solution. 

Brass Solutions of any color may be made by adding carbonate of zinc in 
various quantities to the copper solution. The zinc should be dissolved in 
water with two parts, by weight, of potassium cyanide, and the mixture 
should then be added to the copper bath. A piece of work in the tank at 
the time will indicate the change in color of the deposit. Two parts copper 
to one zinc gives a yellow brass color. For the color of light brass add a 
little carbonate of ammonia to the brass solution. To darken the color 
add copper carbonate. Varying the amount of current will also change 
the color, a strong current depositing a greater amount of zinc, thus pro- 
ducing a lighter color. 

Silver. — The standard solution for silver plating is chloride of silver 
dissolved in potassium cyanide. This solution consists of 3 ounces silver 
chloride with 9 to 12 ounces of 98 percent potassium cyanide per gallon of 
water. Rub the silver chloride to a thin paste with water, dissolve 9 
ounces potassium cyanide in a gallon of water and add the paste, stirring 
until dissolved. Add more cyanide until the solution works freely. The 
bath should be cleaned by filtering. Great care should be taken to keep 
the proper proportions between current, silver and cyanide. A weak cur- 
rent requires more free cyanide than a strong one, and too much cyanide 
prevents the work plating readily, and gives it a yellowish or brownish 
color. If there is not enough cyanide in the solution the resistance to the 
current is increased and the plating becomes irregular. 

The most suitable current for silver plating seems to De about one ampere 
for each sixty (60) inches of surface coated. 

Gold. — Cyanide of gold and potassium cyanide make the best solution 
for plating with gold. The solution is prepared in the same manner as the 
silver solution just described, using chloride of gold in place of chloride of 
silver. The electrical resistance of the bath is controlled by the quantity 
of cyanide, the more cyanide the less the resistance, but an excess of 
cyanide produces a pale color. Hot baths for hot gilding require from 11 to 
20 grains of gold per quart of solution and a considerable excess of cyanide. 
Baths for cold gilding and for plating should have not less than 60 grains 
per quart and may have as much as 320 grains, this quantity being used with 
a dynamo current for quick dipping. 

Wickel. — The solution now almost universally used for nickel plating 
is made up from the double sulphate of nickel and ammonia, with the 
addition of a little boracic acid. 

The double salt is dissolved by boiling, using 12 to 14 ounces of the salts 
to a gallon of water; the bath is then diluted with water until a hydrometer 
shows a density of 6.5° to 7° Baume. 

Cast anodes are to be preferred as they give up the metal to the solution 
more freely. Anodes should be long enough to reach to the bottom of the 
work and should have a surface greater than that of the objects being plated. 

Current strength should be moderate, for if excessive the work is apt to 
be rough, soft or crystalline. Voltage may vary from 3.5 to 6 volts and the 
most suitable current is from .4 to .8 ampere per 15 square inches surface 
of the object. Zinc is the only metal requiring more current than this, and 
takes about double the amount named. 

A nickel bath should be slightly acid in order that the work may have a 
suitable color. An excess of alkali darkens the work, while too much acid 
causes " peeling." 

Iron. — A hard white film of iron can be deposited from the double 
chloride of iron and ammonia which can be prepared by the current 
process. It is somewhat used for coating copper plates to make them 
wear a long time, the covering being renewed occasionally. 

The Electromotive JForces suited to the different metals are: 

Copper in sulphate Volt, 1.5-2.5 

11 cyanide , 4.-6. 

Silver in " 1.-2. 

Gold in " .5-3. 

Nickel in sulphate 2.5-5.5 



THE ELECTROLYTIC REFINING OF COPPER. 



1235 



The Resistance will depend on the nature of the surface. Work is 
best effected with about equal surface of anode and objects, and the coating 
will be more even, the greater the distance between them, especially where 
there are projecting points or rough surfaces. 

Copper and silver should never show any sign of hydrogen being given off 
at the objects; gold may show a few bubbles if deep color is wanted. 
Nickel is always accompanied with evolution of hydrogen, but the bath 
should not be allowed to froth. 

The Rate of Deposit is proportional to current, as described under 
the head of " Electrolysis," in the proportions given in the table of electro- 
chemical equivalents except in the case of gold, the equivalent of which in 
combination with cyanogen is 195.7, but subject to modifications dependent 
upon the hydrogen action just described; there is also a partial solution of 
the metal, so that there is always a deduction to be made from the theoret- 
ical value. Thus : — 

Gold gives about 80 to 90 per cent. 

Nickel " 80 to 95 " 

Silver " 90 to 95 " 

Copper " 98 " 

An ampere of current maintained for one hour, which serves as a unit of 
quantity called the "ampere-hour," represents 



Gramme 0376 

Ounce Troy . . . .00121 



Grain . . . 
Ounce Avoir. 



.58 
.00132 



which multiplied by the chemical equivalent will furnish the weight of any 
substance deposited. 

The Electrolytic Refining* of Copper. 

The largest and most important of electrochemical industries is copper 
refining, conducted at many places in this country and abroad. The pro- 
cess of refining copper electrolytically consists in the transfer of copper 
from the anode to the cathode, by the selective action of the electric cur- 
rent, and in leaving the impurities behind in the anode, electrolyte or 
sediment. _ 

Theoretically the mere transference of copper should require no expendi- 
ture of energy, the energy needed to precipitate it from its solution being 
balanced by the energy set free upon its change to copper sulphate, but 
practically some is needed on account of the resistance of the electrolyte, 
and differences in mechanical structure as well as in chemical purity of the 
anode and cathode. 

The material at present subjected to profitable electrolytic refining is 
crude copper containing from 96 to 98 per cent pure copper and varying 
amounts of other elements according to the character of the ore and method 
of dry refining adopted. The composition of the crude material varies 
greatly, typical samples being given in the following table: 





No. I. 

Per Cent. 


No. II. 
Per Cent. 


No. III.* 
Per Cent. 


Copper .... 
Arsenic .... 
Antimony . . . 

Lead 

Tin 


96.35 
0.08 
0.10 
1.19 
0.22 
0.05 
0.61 


97.19 
2.68 
0.01 


98.60 
0.80 
0.10 
0.10 


Bismuth . . . 

Iron 

Nickel .... 


0.08 
0.02 
0.02 


0.05 
0.10 
0.10 
0.10 
05 


Sulphur . . . 
Silver .... 


0.69 


Oxygen and loss 


0.71 














100.00 


100.00 


100.00 



* Chili bar. 



1236 



ELECTROCHEMISTRY. 



Besides these, the crude copper frequently contains small quantities of 
gold (about one-tenth to one-fifth ounce per ton). 

The crude material is cast in iron molds into anode plates, about three 
feet long, two feet wide, and one inch thick, weighing approximately 250 
pounds. The cathode plates are of electrolytically refined copper practi- 
cally the same in length and width as the anodes but only one-twentietb 
inch thick. The electrolyte or bath in which the plates are suspended is a 
solution of 12 to 20 per cent copper sulphate, and 4 to 10 per cent sulphuric 
acid, the latter being added to decrease the resistance of the solution. This 
resistance is further reduced by keeping the electrolyte warm at about 
40° C. 

•The containing tanks are of wood, usually lined with sheet lead or 
carefully coated with a pitch compound, and of such dimensions that a 
distance of about one inch exists between the faces of the plates. 

In some cases the plates are arranged in series, and in others in parallel 
or multiple, as illustrated. The former has the advantage of requiring 
electrical connections to be made at the first and last plates only, whereas 




Fig. 1. Series Arrangement of Plates. 



the parallel system requires a connection at every plate; but in the series 
system the leakage of current due to the short-circulating action of the 
sediment and sides of the tank is from 10 to 20 per cent, so that the 
parallel is more generally used. 

The connections between the various plates and the circuit in the parallel 
systems are made by copper rods, which are run at two different levels 
along the edges of the tanks, one bar for anodes and one for cathodes. In 
some instances these rods are of the inverted V shape, so that the edges will 




Fig. 2. Parallel Arrangement of Plates. 



cut through any corrosion that may happen to form at the points of con- 
tact. The drop in pressure at these points is not more than .01 volt. The 
vats are arranged so that each is accessible from all sides, and the circula- 
tion of the electrolyte is possible. This circulation may be obtained by 
blowing a stream of air through the electrolyte, but more frequently by 
arranging the vats in steps and connecting them by pipes so that the elec- 
trolyte may pass from the top of one vat to the bottom of the next, as 
shown in Figs. 3 and 4. This maintains a uniform density of the electrolyte 
which is necessary for the proper formation of the deposit. 

The electrical pressure required is from .2 to .4 volt per tank, with a 
current density of 10 to 15 amperes per square foot of cathode plate sur- 
face. The question of current density is very important, because upon 
this depends the rapidity and quality of the deposit. The rate of deposit, 
however, is limited and varies with different grades of the crude metal, 
depending upon the impurities present. For example, antimony, bismuth 



THE ELECTROLYTIC REFINING OF COPPER. 1237 



and arsenic if present would prevent the use of a current density of more 
than 10 amperes per square foot, as they would be carried over and depos- 
ited, especially if present in a soluble form. The maximum current density 
employed in ordinary copper refineries is as above stated, 10 to 15 amperes 
per square foot. If the current density is too great the following difficulties 
will occur: 

a. Liberation of hydrogen at the cathode, and thus a resultant waste of 
energy. 

b. Poor character of deposit. 

If the current density is too low, the copper is in the tanks too long, 
and this results in excessive interest charges. 

The individual vats are connected in series with each other, so that the 
total voltage required may be approximately equal to that of the gener- 




Fig. 3. Circulating System. 

ator, allowing the usual drop of about 10 per cent. Standard generators 
are built to give 125 volts so that a working pressure of about 110 volts is 
obtained, which is a standard value for lighting and other purposes. 

In practice from 400 to 450 ampere-hours are required per pound of 
copper deposited, the theoretical amount according to Faraday's law being 



+ I 



i- 



LEj 



Fig. 4. General Arrangement of Plant. 

only 386.2 ampere-hours. The loss varies from 4 to 20 per cent, according 
to the system employed. 

Anode Impurities and their Effect npon the Electrolyte. — 

The electrolyte when first added consists of 12 to 20 per cent copper sulphate 
and 4 to 10 per cent sulphuric acid. The impurities likely to exist in the 
crude metal anodes have been given in the sample analyses preceding, 
and the following reactions generally occur in an acidulated solution: 

1. Silver and gold remain undissolved in the anode or fall to the bottom 
of the vat. 

2. Lead is converted to lead sulphate and precipitates. 

3. Antimony, bismuth and tin are partly dissolved as sulphates, or 
form unstable sulphates which precipitate as basic sulphates or oxides; 
they partly also remain in the anode sludge. 

4. Arsenic, nickel, cobalt and iron dissolve, but are not under ordinary 
conditions redeposited, hence they merely contaminate the electrolyte. 



1238 ELECTROCHEMISTRY. 



5. Alkaline earth metals except barium and calcium dissolve readily, 
the latter precipitating as sulphates. 

In addition to contaminating the electrolyte and thus interfering with 
the purity of the deposit the presence of these impurities, except gold, 
silver and lead, is objectionable, due to the fact that the anode is consumed 
unevenly. The more electropositive metals such as tin, zinc, etc., being 
more rapidly attacked, the anode surface does not remain smooth, and 
frequently pieces break off and fall to the bottom of the tank. Arsenic, if 
present, often forms arsenates on the anodes, which results in a non-con- 
ducting film, decreasing the current and thus the output. 

Effect of tlie Electrolyte Impurities on tlie l>eposit. — The 
electrolyte does not accumulate all the impurities of the anode because many 
of them never go into solution but simply fall to the bottom of the vat as 
mud. In addition to the proper constituents of the electrolyte there may 
be present in the dissolved state^ the sulphates of iron, zinc, cadmium, alu- 
minum, sodium, etc., besides basic sulphates of arsenic, bismuth and anti- 
mony. The largest part of the impurities present consists of iron, but the 
most objectionable are compounds of arsenic and antimony, as these yield 
their metals at the cathode, with serious results, since as little as .01 per 
cent of either will reduce the electrical conductivity of copper from 4 to 5 
per cent. 

Cuprous oxide and copper sulphide remain partly in the sludge and 
partly dissolve according to the acidity of the electrolyte. Their only evil 
effect is to neutralize some of the free sulphuric acid. 

The composition of the anode sludge (residue) will evidently vary ac- 
cording to the composition of the anode employed, and in practice various 
amounts of gold, silver and lead are obtained therefrom by subsequent 
treatment. 

The cost of refining copper by the electrolytic method is from | to f 
cent per pound. The following products of refining are marketed: com- 
mercial cathodes, which are sometimes shipped to consumers but more 
frequently cast into wire bars, ingots, cakes or slabs of standard dimensions 
and weight. They usually assay from 99.86 to 99.94 per cent of pure cop- 
per, a sample analysis being as follows: 

PER CENT. 

Copper* 99.938 

Antimony .002 

Iron 004 

Oxygen and loss .056 

100.00 

The yield in commercial cathodes is from 97 to 99 per cent of the anodes 
treated, excluding the anode scrap which varies from 7 to 15 per cent of 
the original anode in parallel operated plants; but this scrap is not a loss, 
as it is collected and recast into anode plates. Besides electrolytic copper, 
most plants recover gold, silver and nickel from the slime as previously 
stated. 

The electrolytic copper refineries in the world are now producing copper 
at the rate of 322,295 tons annually, valued at $96,688,500 with copper 
selling at $300 per ton. In addition the by-product in recovered gold and 
silver is valued at $20,000,000 per annum. There are now in active opera- 
tion 33 electrolytic copper refineries, with a total generator capacity of 
20,000 kilowatts; 10 of these are located in the United States, and supply 
about 86 per cent of the world's output; 6 plants are in England and Wales 
producing about 9 per cent, while the remaining plants are on the conti- 
nent of Europe. 

Silver is refined from copper bullion by taking anodes of the bullion £ 
inch thick and 14 inches square, and cathodes of sheet silver slightly oiled. 
The electrolyte consists of water with 1 per cenrt of nitric acid. When the 
current is started the copper and silver form nitrates of copper and silver 
and free nitric acid from which the silver is deposited, leaving the copper 
in solution. Trays are placed under the cathode for catching the deposited 
silver, and if there is any copper deposited owing to the solution contain- 

*This sample was obtained by refining the crude copper given in 
column III of the preceding table of crude copper anodes. 



PRODUCTION OF CAUSTIC SODA. 1239 

ing too little silver or a superabundance of copper, the copper falls into the 
trays and is redissolved. 

In the Moebius process the deposit is continually removed from the 
cathode by means of a mechanical arrangement of brushes, and falls into 
the trays above mentioned. 

A In 111 in u in. — Practically the output of this metal for the entire world 
is now produced electrolytically. The only process used on a large scale 
is that invented independently in 1886 by Mr. Charles M. Hall in the 
United States, and by Paul L. V. Heroult in France. This process consists 
in electrolyzing alumina dissolved in a fused bath of cryolite. The alumina 
is obtained from the mineral bauxite which occurs abundantly in Georgia, 
Alabama and other regions. The natural material, being a hydrated 
alumina containing silica, iron oxide and titanic oxide in the following 
proportions: 



Al 2 O a 


.56 


Fe 2 3 


.03 


SiOo 


.12 


TiO" 


.03 


H 2 


.26 



must be treated in order to drive off the water and eliminate the impurities. 
This may be accomplished by a chemical process, but it is effected more 
simply by heating the material mixed with a little carbon as a reducing 
agent in an electric furnace. The impurities are thus reduced and collect 
as a metallic regulus in the bottom of the mass. This leaves the alumina 
nearly pure and it may be tapped off while fused or easily separated by 
breaking it up after cooling. In practice it requires two pounds of alumina 
for each pound of aluminum produced. The flux or bath in which the 
alumina is dissolved consists of cryolite, a natural double fluoride of alu- 
minum and sodium (Al 2 F 6 .6NaF) found in Greenland. This is melted in 
a large carbon-lined, rectangular, sheet-iron tank, which constitutes the 
negative electrode, a group of 40 carbon cylinders, each 3 inches diameter 
and 18 inches long, which are suspended in the tank, forming the positive 
electrode. A direct current of about 65 horse-power at 5 to 6 volts is used. 
Only a portion of this voltage is required to decompose the alumina, the 
balance, amounting to about two or three volts, represents the heat pro- 
duced which keeps the bath at the proper temperature and fluidity neces- 
sary for electrolysis — 850 to 900° C. The passage of the current causes 
the aluminum to deposit on the bottom of the tank as a fused metal, being 
drawn off periodically. The oxygen set free combines with the carbon of 
the positive electrodes and passes off as carbonic oxide. The reaction is 
Al 2 03 -I- 3C = 2A1 -f 3CO. About one pound of carbon is consumed for 
one pound of aluminum produced. When the alumina becomes exhausted 
from the bath, the voltage rises and lights a lamp shunted across the 
electrodes, thus giving notice that more material is needed. Each elec- 
trical horse-power produces about one pound of aluminum per day of 24 
hours. According to Faraday's law the weight of aluminum deposited by 
1,000 amperes is .743 pound per hour. The actual yield of metal by the 
Hall process is about 85 per cent of this theoretical amount. 

The aluminum obtained averages 0.1 per cent iron, 0.3 per cent silicon, 
with traces of copper, titanium and carbon, but is guaranteed over 99 per 
cent pure. 

The metal when drawn from the tanks is cast into rough ingots which 
are afterwards remelted and converted into commercial shapes such as 
sheets, rods, wires, etc. 

jp»o»T)Ctj:o:w or caustic soda. 

Caustic soda or sodium hydrate (NaOH) is used in the manufacture of 
hard soaps, in the rendering of wood pulp for paper manufacture, in the 
purification of petroleum and petroleum residues, and also for the produc- 
tion of metallic sodium. 

Many attempts, extending over nearly a century, have been made to 
manufacture caustic soda (NaOH) and chlorine (Cl 2 ) from ordinary salt 
(NaCl), by means of electrolytic action. The fundamental reaction: 

2NaCl + 2H 2 + Elect. = 2NaOH+H 2 + CI, 



1240 



ELECTROCHEMISTRY. 



is readily obtained experimentally, but is difficult to accomplish on a com- 
mercial basis. Salt, or sodium chloride, when electrolyzed in the presence 
of water will form caustic soda, but secondary reactions take place and the 
result is a mixture of salt, caustic and hypochlorite of soda. This diffi- 
culty can be avoided by separating the caustic soda solution that is formed 
by a porous diaphragm, or by drawing it off as soon as formed; and in some 
cases the metallic sodium is absorbed in mercury or molten lead. 

The following conditions have been found necessary for the success of 
this process: 

1. Cost of power must be very low — not in excess of $30 per horse- 
power per annum (24 hours per day). 

2. The process must be continuous. 

3. The electrodes must be as nearly indestructible as possible. 

4. The products of electrolysis must be capable of removal from the 
vessel or electrolyte as the process proceeds. 

5. The maintenance costs must be small. 

6. The plant must operate on a large scale. 

It is only lately that a few processes have been commercially successful. 
The two most prominent systems for the electrolytic production of caustic 
soda and chlorine from common salt are the Castner-Kellner and the 
Acker processes, one operating at moderate temperatures (40° C.) and the 
other at high temperatures (850° C). 

The Castner process employed in this country at Niagara Falls is as 
follows: The electrolytic tank consists of a slate box 4 feet long, 4 feet 




Fig. 5. Castner Cell. 



wide and 6 inches deep, the joints being made by means of a rubber cement. 
Two slate partitions reaching within T x ff inch of the bottom (under which 
are grooves) divide the cell into three compartments, each 15 inches by 
4 feet, sealed from each other by a layer of mercury covering the bottom 
of the tank to a considerable depth. The two end compartments through 
which the brine is passed are provided with carbon anodes, shaped like a 
rail section, the broader flange being placed about a half inch above the 
mercury. These compartments are provided with tight covers and ex- 
haust pipes of rubber and lead to convey the chlorine away. The central 
compartment has an iron cathode composed of twenty upright strips and 
is supplied with pure water, which is drawn off whenever its specific gravity 
increases to 1.27, due to the presence of the maufactured caustic, while 
the liberated hydrogen is led from this chamber by means of pipes and 
used as a fuel for the concentration of the caustic. The tank is pivoted at 
one end on* a knife-blade and rests at the other on an eccentric, which raises 
and lowers that end of the tank about a half an inch once a minute and 
causes a circulation of the mercury between the outer and middle compart- 
ments. The current enters the outer chambers, splits up the sodium 
chloride (common salt, NaCl) into sodium and chlorine (Na and CI), the 
latter is liberated at the carbon anodes and passes through the exhaust 
pipe to the absorption chambers, where it combines with slacked lime to 



PRODUCTION OF CAUSTIC SODA. 1241 

form bleaching powder (CaCl20 2 .CaCl2). The sodium combines with the 
mercury, forming an amalgam containing about 2 per cent of sodium, 
whirh by the tilting of the tank passes to the central chamber, where it 
serves as the anode, and combines with the water to form caustic soda 
(NaOH) and hydrogen (H), the latter appearing at the iron cathode. 

Each of these tanks uses 630 amperes at 4.3 volts; 10 per cent of this 
current is shunted around the inner cell, because otherwise the amalgam 
would fail to deliver enough sodium, and the mercury would oxidize, thus 
producing mercury salts and contaminating the caustic. The theoretical 
voltage required is but 2.3, the remainder being utilized in overcoming 
the ohmic resistance of the electrolyte and in keeping it warm, the limit of 
temperature being 40° C, as above this point chlorate is formed. The 
output of this process per horse-power per day is 12 pounds of caustic and 
80 pounds of bleaching powder for each cell. The product contains from 
97 to 99 per cent caustic, \ per cent sodium carbonate, .3 to .8 per cent of 
sodium chloride and traces of sodium sulphate and silicate. 

The Acker process, formerly used at Niagara, for obtaining caustic soda and 
chlorine from salt is similar to the Castner-Kellner process just described, but 
differs in that it employs molten lead in place of mercury as a seal, fused salt 
instead of brine as the electrolyte and operates at a temperature of 850° C. 
which is required to maintain the fused condition of the electrolyte. The 
containing vessel is a cast-iron tank five feet long, two feet wide and one 
foot deep, the sides above the molten lead being covered with magnesia so 
that the current must pass from the carbon anodes to the lead which acts 
as the cathode, the lower faces of the anode blocks being three-fourths 
inch above the lead. At one end of the tank is a small compartment 
separated from the remainder of the vessel by a partition dipping into the 
lead to such a depth that nothing but this fused lead can pass from one 
compartment to the other. The chambers are loosely closed by fire-clay 
slabs and the escaping chlorine drawn away through side flues by powerful 
exhausts. In the smaller compartment the lead is subjected to a stream 
of steam, which, acting upon the lead sodium alloy, forms ccustic soda and 
liberates hydrogen. The steam jet is introduced below the surface, but 
points vertically upwards, and the resulting spray strikes a curved hood 
which deflects it into a third chamber in which the lead and caustic separate, 
the latter flowing out of the furnace over a cast-iron lip, the lead sinking 
and passing back to the main chamber, while the evolved hydrogen is con- 
ducted away. The fused caustic is collected in an iron pan where it solidifies 
and is removed every hour. The output is 25 pounds of solid caustic per 
hour. This process avoids the evaporation of the water required in the 
Castner-Kellner process, but higher maintenance costs offset this advan- 
tage. The current employed per vessel in the Acker process is 2100 am- 
peres at from 6 to 7 volts, of which energy 54 per cent is used in chemical 
action and the remainder in maintaining the temperature. 

The same methods that have been commercially successful for the pro- 
duction of caustic soda and chlorine from salt are used to produce caustic 
potash and chlorine. Caustic potash is of value for the manufacture of 
soft soaps, the preparation of oxalic acid from sawdust, and for the ex- 
traction of metallic potassium. The raw material, potassium chloride (KC1), 
is more expensive than sodium chloride, costing approximately four times 
as much,* so it is an advantage to employ the electrochemical process 
which is more economical in raw material than an ordinary chemical method 
would be. 

Production of Metallic Sodium. — This metal was formerly ob- 
tained by the reduction of its carbonate or hydrate mixed with carbon, but at 
the present time all the metallic sodium employed in commerce is obtained by 
means of the Castner electrolytic process. The raw material is solid caustic 
which fuses readily at a low red heat and is obtained by the Castner 
caustic process already described. A diagrammatic view of the apparatus 
is shown in Fig. 6. The containing vessel is of steel, the electrodes are 
usually of cast iron. The electrical pressure employed is about 4.4 volts 
direct current, the action being as follows: The vessel is placed in an ordi- 
nary furnace flue, in which the gases are at a temperature high enough to 
maintain the caustic soda in a fused state. The current enters at the posi- 

* NaCl costs $9.00 per ton; KC1 costs $37.05 per ton. 



1242 



ELECTROCHEMISTRY. 



tive electrode, which is a hollow cylinder provided with vertical slits, so as 
to allow free circulation of the electrolyte. The negative electrode is placed 
at the bottom of the vessel, and terminates in the space in the center of 
the anode. A cylinder of iron wire gauze is placed between the electrodes, 
its function being to prevent the separated sodium from spreading over 
the entire surface and coming in contact with the oxygen liberated at the 
anode. The extreme fluidity of the fused caustic, however, allows it to 
pass readily through the gauze openings, while the greater surface tension 
of the liberated sodium will not allow it to pass through the same. The 
metallic sodium in its fused state has a lower specific gravity than the 
fused caustic, hence it remains at the surface, and is bailed out from time 
to time. The liberation of hydrogen at the cathode serves to protect the 
metal from the possible action of the oxygen. 

Potassium Chlorate is produced in considerable quantities both here 
and abroad. The Gibbs process used at Niagara Falls consists in the elec- 




Fig. 6. Castner Metallic Sodium Electrolytic Cell. 

trolysis of potassium chloride solutions, using a copper or iron cathode 
and a platinum anode. The cells are composed of a wooden frame, A, 
covered with some metal, B, such as lead, not attacked by the electrolyte. 
The latest form of cathode consists of a grid of vertical copper wires, C, 
kept in position by crossbars, D, of some insulating material, as shown in 
Fig. 6. The grid is placed in a vertical position against one side of the 
cell frame, and kept in place by the anode of the adjoining cell, from which 
it is insulated by the strips, F, and bars, D. 

The opposite side of the cell from that occupied by the cathode is par- 
tially closed by the anode (see dotted lines of Fig. 7). This consists of a 
thick lead plate, L, covered with platinum foil on the outer side, E (Fig. 8). 
This anode is held in position by the cathode and framework of the follow- 
ing cell. G is a pipe, reaching to the bottom of the cell, by which the po- 
tassium chloride is continuously supplied, and H is the overflow pipe to 
convey the mixed solution of the chloride and chlorate, as well as the lib- 
erated hydrogen gas away from the cell. S, S, S, S are lugs projecting 



PRODUCTION OF CAUSTIC SODA. 



1243 



from the framework, by means of which any number of cells can be bolted 
together to form a series of cells. Fig. 8 shows a group of three cells, the 
heavy plates (X and Y) being used to close the ends of the wooden frame- 
work, and form a fully closed series of cells with the only openings at the 
various supply and overflow points. The current connections are made at 
the points (m +) and (n — ). In normal working the cell is continuously 
fed by each of the supply pipes G, with a solution of potassium chloride, 
the rate of supply being so regulated as to maintain the temperature of the 
cell at 50° C. , and the amount of chlorate in the discharged solution slightly 
under 3 per cent. 

Since the plates C and L of each cell are in metallic contact, due to the 
lead lining, the electrolysis occurs between the anode of one cell and the 
cathode of the following cell (see narrow space between cells), this space 





Fig. 7. Gibbs Cell. 



Fig. 8. Gibbs Cell. 



being not more than one-eighth inch wide. The fact that the cathode is 
a grid allows the electrolyte to circulate around it, and all the solution thus 
passes upwards and out of the cells at H. 

The percentage of chlorate in the overflow solution is low, thus re- 
frigeration is necessary to recover it, and Fig. 9 is a representation of an 
electrolytic chlorate plant using this form of apparatus. £ is the supply 
tank, V the electrolytic cell, R the refrigerators, and P the pump by 
means of which the exhausted electrolyte is returned to the supply tank, 
while the chlorate precipitates out as crystals. The reason for using the 
refrigerator is that in solutions containing only 3 per cent of chlorate, the 
latter will not crystallize out upon natural cooling, as it would if present 
in large quantities. This low percentage of chlorate present is necessary to 
obtain quick recovery, as otherwise the presence of the hydrogen will cause 
secondary reactions, and cut down the efficiency of the conversion. The 
pressure employed is about four volts per cell, of which 1.4 is required to 
convert the chloride into chlorate 

6KC1 + 6H 2 4- Elect. = 6KOH 4- 3H^ + 3CI^ 

6KOH + 3H^ + 3Cb = 2KC10 3 + 4KC1 4- 3H^ 

and the remainder produces the heat that maintains the electrolyte at 50° C. 
which is necessary for the proper reaction. The current density is high, 
about 500 amperes per square foot of anode surface. At Niagara the 
plant consists of fifty such cells, connected up into two sets of 25 cells 
in series. A direct current of 10,000 amperes is supplied at 175 volts, 
which, allowing for line drop and losses at cell contacts, gives the proper 
pressure. 



1244 



ELECTROCHEMISTRY. 



Electrolytic chemical effects such as bleaching have been produced through 
the action of chlorine or other matter set free by an electric current. It 
is possible in this way to cause substances to act while in the nascent state 
and therefore more powerful. Disinfecting and deodorizing of sewage has 
also been accomplished in a similar manner, as in the Woolf process by 




Fig. 9. Arrangement of Gibbs Process, 
the electrolysis of a salt solution mixed with the sewage. The passage 

of the current liberates (Cl 2 ) chlorine and sodium hypochlorite (NaCIO), 
which act upon the refuse matter. 

Electrolytic chemical analysis is a special subject, the discussion of which 
is usually confined to books and journals relating particularly to chemical 
analysis; it is not ordinarily considered in connection with the general 
subject of electrochemistry. 

ELECTROTHERMAL CHEMISTRY. 

Electro thermal Chemistry includes those methods in which an elec- 
tric current raises the temperature of materials, usually to a high degree, 
in order to produce fusion, chemical action or other effects. Since elec- 
trolysis is not desired an alternating current is generally employed. 

The effect on the materials and the amount of product obtained is more 
or less proportional to the heat energy developed in the furnace. While 
the heat necessary to produce a certain change in a given amount of ma- 
terial is perfectly definite, the heat lost by radiation, conduction, etc., is 
variable, so that the efficiency must always be less than 100 per cent. 

The proportion existing between the heat energy employed in an electric 
furnace to produce a desired physical or chemical change and the total 
heat supplied is termed the efficiency of the furnace. 

The degree of efficiency attainable depends upon many factors: 
1. The size of the furnace. 

Necessary temperature for the desired reaction. 
Protection from radiation. 
Arrangement of terminals. 

Method of recharging, continuous operation being most economical 
as the heat of the furnace walls is retained. 

6. Method of removing the charge, it being undesirable to destroy a 
furnace to get at the charge. 

The most important of all these considerations is undoubtedly the size 
of the furnace, since the radiating surface of a small capacity is relatively 
greater than that of a large furnace. Consider two cubical furnaces: one 
of 1000 units' volume, the other of one unit's volume, the radiating surfaces 
would be 600 square units for the former, and 6 for the latter; hence the 
radiating surface for the smaller would be ten times larger per unit ca- 
pacity and the losses would be in the same ratio. 

Electric furnaces are divided into three general classes as follows: 

'The material may be heated by passing current 
directly through it. 
The material may be heated by the heat gen- 
> erated in a conducting core. 

The material may be acted upon by heat radiated 
from an electric arc. 
„The material may be fed through an arc stream. 
( Where the charge is conductive and is heated by 



2. 
3. 

4. 
5. 



Resistance Types. 



6. Arc Types. 

c. Induction Type. 



currents induced in it. 



ELECTROTHERMAL CHEMISTRY. 



1245 



The phenomena occurring in a furnace may be subdivided as follows: 

a. Heating alone without fusion, as in the manufacture of graphite. 

b. Heating and fusion, as in the treatment of bauxite. 

c. Heating and chemical change without fusion, as in the manufacture 
of carborundum. 

d. Heating, fusion and chemical change, as in the manufacture of calcium 
carbide. 

Calcium Carbide. — This compound is produced by an electrothermal 
process invented by Willson in 1891, the total output throughout the 
world being about 300,000 tons in 1902. Its value lies in the fact that 1 
pound of this substance mixed with water produces theoretically 5.5 and 
actually about 5 cubic feet of acetylene, equivalent in illuminating power 
to about 70 cubic feet of ordinary gas. The reaction yielding acetylene is 
CaC 2 + H 2 = CaO + C 2 H 2 . Various forms of electric furnace have been 
employed in the production of calcium carbide. One type invented by 
King and represented in Fig. 10 consists of an iron car, A, which holds the 
materials and carbide, at the same time acting as one 
electrode. It is run into place or removed as desired, 
and being provided with trunnions its contents may 
be tipped out. The other electrode consists of a 
bundle of carbon plates carried by a heavy rod, C, 
composed of a copper strip strengthened by iron 
side bars. The material fed through the channels 
G, F, consists of a mixture of 1 ton of burnt lime and 
f ton of ground coke to produce 1 ton of carbide, 
the reaction being CaO 4- 3C = CaC 2 + CO . An arc 
is first formed between the electrode, C, and the floor 
of the truck. The resulting high temperature con- 
verts the mixture into carbide, the electrode being 
gradually raised and more material added until the 
car is nearly filled with the product, when it is run 
out and replaced by another. At Niagara Falls a 
rotary form of furnace invented by C. S. Bradley 
is used, being operated continuously and producing 
about two tons in 24 hours when supplied with 3,500 
amperes at 110 volts, or about 500 horse-power. Fig. 10. King Car- 
Since no electrolytic action is required, an alterna- bide Furnace, 
ting current is employed. 

Carborundum is a commercial name for carbon silicide (CSi) produced 
in large quantities according to the inventions of A. G. Acheson and his 
assistants. It is used as an abrasive, being hard enough to scratch ruby. 

Hit is formed by intensely heating in an electric furnace a 
mixture of 3£ tons of ground coke, 6 tons of sand and about 
.^ H tons of sawdust and salt, the yield being 3 or 4 tons»of 
P crystalline carborundum and about as much more of the 
1 amorphous material. The furnaces used at Niagara Falls 
| consist ;of fire-brick hearths 16 feet long and 5 feet wide, 
loosely set together so that the liberated CO can readily 
escape, with solid brick walls at each end about 2 feet thick 
and 6 or 8 feet high as illustrated. In the middle of each 
of these walls there are iron frames through which the cur- 
rent is led to a core composed of carbon, weighing about 
1000 pounds and extending the entire length of the furnace. 
This core is raised to a very high temperature (about 3000° 
C.) by passing through it for 36 hours an alternating current 
of about 1000 electrical horse-power at 190 decreasing to 
125 volts. The heat from the core permeates the mass and 
converts it into carbon silicide, which is broken up after the 
furnace has cooled and used to make hones, wheels for 
grinding, etc. 

Manufacture of Graphite. — This application of the 
electric furnace depends only upon heat and was suggested 
to Acheson by the fact that when the temperature limit 
of the carborundum furnace was exceeded even slightly (250° C.) a large 
amount of graphite was formed around the conducting core. In fact, it 
has been stated that a variation of 3 per cent in the size of the carbon core 
one way or the other would seriously interfere with the working efficiency 





1246 ELECTROCHEMISTRY. 

of the carborundum process — when the core is too small the heat becomes 
excessive and it is reduced to graphite — the silicon volatilizing. Acheson's 
experiments indicate that all metallic carbides are decomposed by the 
application of intense heat, the metal constituent volatilizing, the carbon 
remaining behind as practically pure graphite, and his patents are based upon 
this theory. 

The commercial work of the Acheson Company is in two lines: 

A. Graphitizing formed carbon objects. 

B. Graphitizing anthracite coal en masse. 
The product in every case is pure graphite. 

In case A. the material to be graphitized, is stacked up in a furnace be- 
tween the electrodes as a partial core 2 feet square and about 30 feet long, 
being thickly covered and the spaces between the pieces filled with a finely 
ground mixture of carbon and carborundum, alternating current of 
3000 amperes at 220 volts is applied, and changed to 9000 amperes at 
80 volts before the end of the run of about 20 hours. 

In case B it is found that the best results are obtained if the core con- 
sists of a rather impure form of carbon, one which when burned at ordinary 
temperatures would leave a large percentage of ash (10 to 15 per cent). 
This is ground to the size of rice chains and used as the furnace charge, 
with a conducting core of partially graphitized carbon, about 1000 H.P. 
of alternating current being applied for 20 hours. 

Alundum, the trade name for artificial corundum, is an abrasive made 
by a process due to C. B. Jacobs and others. Bauxite, a natural hydrated 
alumina, the same material as used in the Hall aluminum process, is cal- 
cined to drive off the water and then fed into an electric furnace, the con- 
struction of which is shown in the illustration. It consists of a conical 




1111111 



Fig. 12. Carborundum Furnace. 

sheet-iron shell mounted on a hydraulically operated plunger that raises 
and lowers it, to maintain a constant current of 2,000 amperes at 80 volts. 
The electrodes consist of two carbon rods that project into the shell, which 
is cooled by water, from the U-shaped trough, trickling down its outer 
surface. 

The time consumed for fusion is about 12 hours. The mass is allowed to 
cool and is then removed from the furnace by holding the sheet-iron shell 
in position and lowering the plunger, the product being broken up and 
sorted. It consists of four parts; namely, a red and blue mass in the in- 
terior, crystals that form in the blow holes, a porous outer portion and a 
by-product consisting of a metallic regulus of ferro-silicon which is used for 
the treatment of iron in the Bessemer and open-hearth furnaces. The 
porous outer part is used as a recharge, and the mass as well as the crystals, 
which are of the general nature of rubies and sapphires, in fact chemically 
identical with these gems, are ground up and used to make grinding wheels 
and other abrasives. 

Cyanides of Potassium and Sodium are produced electrochemically by 
the process of C. S. Bradley, C. B. Jacobs and others. A mixture of barium 
oxide or carbonate with carbon is heated in an electric furnace to produce 
barium carbide (BaC 2 ). While the mass is still hot, nitrogen (air cannot 
be used, as the oxygen present would oxidize the barium and carbon) is 
passed through it and barium cyanide forms, the complete reaction being: 

BaO + 3C + N 2 = BaC.N, + CO. 

The barium cyanide thus produced is treated with sodium carbonate, the 
result being a mixture of sodium cyanide and barium carbonate. The 
former is separated by dissolving it in water, the insoluble barium 
carbonate being used over again. Potassium cyanide is made in a similar 



ELECTROTHERMAL CHEMISTRY. 1247 

manner and either salt is suitable for gold extraction and other purposes 
for which cyanides are employed. 

Electric Smelting*. — One of the earliest commercial processes in elec- 
trochemistry was that devised by E. H. and A. H. Cowles in 1884. A mix- 
ture of about 2 parts of alumina, 1 or 2 parts of granulated copper and 
1 or 2 parts of carbon was introduced in a brickwork chamber. Bundles of 
carbon rods inserted at the ends formed the electrodes between which a 
current of 3000 amperes at 50 volts was maintained. At a very high 
temperature the alumina was reduced (A1 2 3 + 3C = AI2 + 3CO) and the 
resulting aluminum combined with the copper to form aluminum bronze. 
This process is no longer of commercial importance, since pure aluminum 
can be readily purchased; and when smelted with pure copper gives a better 
grade of aluminum bronze at a lower cost than is possible with the above 
method. 

Iron and steel can be produced by reducing iron ore with carbon in 
an electric furnace. For example, a mixture of magnetite and carbon can 
be heated by passing a current through it as in the Cowles aluminum bronze 
process; through a carbon core in contact with the material as in the car- 
borundum process; or by the action of an arc as in the carbide process. 
The reaction is Fe 3 4 4- 4C = 3Fe 4- 4CO. Pure (i.e., wrought) iron, 
cast iron or steel may be produced, depending upon the proportion of car- 
bon. The chief advantages are the directness of the process and the fact 
that the impurities in the fuel (sulphur, silicon, etc.) are not introduced. 
On the other hand, it is a question whether the electric furnace can com- 
pete in economy with the blast furnace and Bessemer converter. 

The field which is at present being developed is the conversion of scrap 
iron and pig iron into crucible steel by means of the electric furnace. This 
method offers reasonable chance of success, since the cost of crucible steel 
is high and therefore the method employed may be relatively costly. 

There are several distinctive types of furnaces employed, some being of 
the arc type, some of the resistance type, and another of the induction 
type. This latter method seems to be the most promising, since the pos- 
sibility of introducing anode impurities into the charge is absolutely done 
away with. 



X-RAYS. 

Revised by Edward Lyndon. 

The ultimate nature of X-rays is as much a matter of doubt at the 
present day as when Professor Roentgen presented his original papers in 
1895. It is generally conceded that they are the product of cathode rays, 
these latter having their origin in electrical discharges through high vacua. 

X-rays are produced whenever cathode rays strike some solid substance, 
and the method employed for their production consists in exciting a vacuum 
tube, having electrodes sealed in its ends, by means of a static machine 
or from the secondary of a high potential induction coil. 

Under the influence of a high potential dark or cathode rays emanate 
from the negative terminal or cathode; these rays are repelled from the 
surface of the cathode, and where they impinge on a solid substance X-rays 
are emitted. 

X-rays and cathode rays are fundamentally different in that the cathode 
rays are subject to magnetic deflection, while X-rays are not. This fact 
is explained on the assumption that the cathode stream consists of particles 
moving at high velocity and carrying a negative charge. Such a stream 
is capable of being deflected by a magnetic field. When, however, the cathode 
stream strikes the solid substance, called the anti-cathode, the particles 
yield up their electric charge, and in passing from this point as X-rays 
show no magnetic deflection. 

The discharge of the cathode stream does not necessarily take place 
within the tube from terminal to terminal, but may be made to travel in 
any desired direction by altering the position and configuration of the 
cathode. 

The generally accepted idea is that these rays travel in lines normal to 
the surface from which they originate, and for this reason the cathode may 
be so shaped that the rays can be focused on the anti-cathode; that cathode 
rays can be focused is well known, but William Rollins holds that it is 
doubtful if the rays actually travel in lines normal to the cathode surface, 
reasoning that since the cathode stream is made up of moving particles 
carrying a negative charge there must exist a repelling force between all 
such particles; if this repelling force did not exist, the path of travel would 
be normal to the cathode surface, and the focus point would be found at 
the center of curvature of the cathode. Rollins states that the focus point 
lies beyond the center of curvature of the cathode and that this distance 
between the actual focus and the center of curvature increases with in- 
creasing potential across the tube terminals, due to an increased charge 
and consequent increased repelling force between the particles constituting 
the cathode stream. 

Where cathode rays strike upon glass or a like substance, the phenomenone 
of fluorescence appears. These rays are similar in many respects to X-rays, 
both are able to excite fluorescence, to affect sensitive films, and are sub- 
ject to selective absorption in passing through solid substances. 

The fact that reflection and refraction have not been conclusively shown 
by experiment to be properties of X-rays would indicate that these rays 
are not in the order of transverse vibrations. 

Quite recently, however, experiments have been made in which it was 
shown that X-rays are subject to polarization, and while reflection and 
refraction have not been absolutely proven to be properties of the rays, 
the generally accepted idea is that X-rays are ether vibrations of enormous 
frequency and short wave length. These rays, like ultra violet light, will 
discharge electrified bodies. This fact may be accounted for on the material 
theory of X-rays, on the assumption that when the charged particles making 
up the cathode stream strike the anti-cathode they yield up their electric 
charge and pass from this point as X-rays, to all purposes a stream of 
moving particles divested of their electric charge; these particles would then 
tend to become charged again in the presence of an electrified body. It 

1248 



X-RAYS. 



1249 



is more probable, however, that X-rays are ether vibrations, and that dis- 
charge of electrified bodies under their influence is due to ionization of the 
air, being similar in this respect to ultra violet light. 

Tubes, — Tubes for the production of X-rays are made of glass, the 
electrodes are sealed in the tube and the air exhausted, and upon the degree 
of vacuum depends the penetration of the X-rays emitted. 

It is desirable, and the general practice, to provide some metallic body 
in the tube upon which to focus the cathode rays, this being the anti- 
cathode, and it is from this body that X-rays are emitted. In Fig. 1, A 
is the anode, B the anti-cathode, and C the cathode. The relative positions 
of these terminals may vary, considerably with the different types, but in 
all cases the functions are the same. 

A separate electrode in the tube acting as the anti-cathode is not essen- 
tial in the production of X-rays; as they are emitted whenever the cathode 
rays strike any solid substance, they would appear if the cathode rays 
were focused on the glass tube itself, or the cathode rays may be focused 
so as to fall on the anode, making this single electrode both anode and anti- 
cathode. 

The anode and cathode are usually made of aluminum, as this mfetal 
undergoes very little disintegration under the action of discharge. Ov ing 




Fig. 1. 



to the difference in the expansion coefficients of glass and aluminum it is 
necessary to join the anode and cathode to platinum wires, sealing the 
platinum into the glass in order to make the external connections. 

Where the cathode rays strike upon a comparatively small area on the 
anti-cathode considerable heat is developed, consequently some metal, 
such as platinum, which is capable of withstanding high temperature, 
must be used for the anti-cathode. 

Under normal operating conditions the anode and the anti-cathode are 
connected to the positive of the source of supply, while the cathode is, of 
course, connected to the negative. Considerable care should be exercised 
in keeping the direction of current flow through the tube in the right direc- 
tion, for if the direction of current be reversed and continued for a length 
of time, blackening of the tube will result because of the disintegration of 
the platinum anti-cathode, and the tube becomes inoperative. The direc- 
tion of the current flow, per se, through the tube has nothing to do with 
the production of X-rays, but it is essential that the cathode stream should 
travel in such a direction at all times so as to strike the anti-cathode. 

The tube shown in Fig. 1 would emit X-rays if the exciting source were 
an alternating current of sufficiently high potential, but X-rays available 
for use, i.e., those sent out from the anti-cathode, would be emitted only 
half the time, or during that time in which the current would be normal 
in direction, while the tube would be subject to a certain amount of damage 



1250 



X-RAYS. 



during those portions of time in which the current flowed in the wrong- 
direction. 

Tubes have been made for use with alternating currents, one form of 
which is shown in Fig. 2. In the tube shown both terminals are so shaped 
as to focus the cathode rays from each terminal during the half cycle in 
which it is a cathode, upon a common anti-cathode. 

The penetration of X-rays is dependent upon the vacuum in which they 
originate, while the emissivity of the anti-cathode increases as the atomic 
weight of the substance forming it increases. 

Since the penetrative power of the rays is in a measure proportional to 
the degree of vacuum, several tubes of various degrees of exhaustion are 
necessary where the class of work is varied, and in all cases tubes should 
be selected for the particular use for which they are intended ; but one 
having a vacuum, the resistance of which is equivalent to a six or eight- 
inch spark gap, will give fairly good results for a variety of work. 




Fig. 2. 

A. W. Isenthal and H. Snowden Ward state that "there exists a condi- 
tion, the causes for which have not yet been sufficiently studied, when the 
tube emits rays of great penetration and withal yields a vigorous image, 
both on the fluorescent screen and on the plate. The characteristics of 
this stage of maximum efficiency are an incandescent anti-cathode with 
some traces of blue anode light in the tube. Unfortunately this state of 
affairs is more or less transient, and the tube soon becomes perforated." 

The vacuum gradually increases with the amount of use of tubes, this 
being ascribed to the fact that the anti-cathode and other platinum parts 
within the tube are subject to slow disintegration under the action of dis- 
charge, and the particles so separated, on cooling, occlude some of the 
residual gas in the tube. 

If the increased vacuum is due to the occlusion of the residual gas, ob- 
viously the original vacuum may be partially restored by the application of 
heat, the occluded gas being given up under the action of heat. 

This heat may be supplied by some external source or by sending through 
the tube a current of sufficient strength to appreciably warm it, the former 
method being preferable. 

In all cases it is advisable to include a spark gap in the circuit to the tube. 
It lessens the liability of the tube to puncture in case one of the electrodes 
becomes detached, and it acts as a gauge on the vacuum, discharge taking 
place across the gap if the vacuum and the consequent resistance of the tubes 
increase appreciably. 



X-RAYS. 



1251 



Regenerative Tabes. — It is impossible to prevent gradual 
changes in vacuum, and resulting changes in resistance and penetrative 
power of the ravs with continued use of a tube, but these changes from the 
original state may be minimized by the use of Regenerative Tubes, many 
types of which are on the market. 

There are certain substances, such as palladium, etc., which occlude gas at 
ordinary temperatures and yield up this occluded gas on being heated; 
advantage is taken of this property for maintaining the vacuum. One 
type of regenerative tube is shown in Fig. 3. 




Fig. 3. 

The absorbent is placed in a branch of the tube, shown at A; an auxiliary 
path for the current is provided through this branch, but under normal 
conditions no current passes via this auxiliary path. If, however, the 
vacuum increases beyond a predetermined spark length for which the ad- 
justable arm B is set, the current will then travel by way of the auxiliary 
path in preference to the path through the tube, with the result that the 
cathode rays from the auxiliary cathode in the absorbent chamber will 
heat the absorbent, causing it to give up its gas which lowers the vacuum 
in the tube. This gas, however, is reabsorbed when the tube cools. 

Another method of regeneration depends upon the fact that at high 
temperatures platinum is permeable to hydrogen. Fig. 4 shows a tube 
in which a platinum wire is sealed into the side neck of the tube at A and is 
protected by a glass cap. When the resistance of the tube increases ap- 
preciably the glass cap protecting the wire is removed, and as the latter is 
heated by means of a Bunsen Burner or a spirit lamp, hydrogen is in- 
troduced into the tube, lowering the vacuum. 




Fig. 4. 



The tube shown in Fig. 4 has an anti-cathode designed to obviate high 
temperatures at this point. This anti-cathode consists of a heavy metallic 
head with an oblique reflecting surface, the head forming part of a metallic 
tube which extends back into the comparatively cool side neck, this metallic 
tube being connected to the outside terminal by means of a wire. Due to 
the fact that the head and metallic tube have considerable mass and are 
good conductors of heat, exposing a large surface for radiation, the heating 
of the reflecting surface is not excessive. 



1252 



X-RAYS. 



Various forms of anti-cathodes have been devised to obviate high tem- 
peratures, generally taking the form of water cooling (not in direct contact), 
or by so disposing metallic bodies that the heat generated at the reflecting 
surface will be rapidly conducted away. 

Exciting* Source. — The minimum potential across the terminals of a 
vacuum tube for the production of X-rays has been variously estimated from 
7000 to 100,000 volts. The appearance of X-rays, however, under a pres- 
sure of 7000 volts was due to special conditions, and, ordinarily, pressures 
much higher must be employed. 

High potentials could, of course, be obtained from specially designed 
transformers working on alternating current circuits, but since double 
focus tubes, adapted for alternating current, present difficulties in actual 
operation, their use has not become general, and other sources of high 
potential giving a uni-directional current are almost universally used. 

Static machines give very good results, their current being uni-directional 
and the potential practically constant, and therefore a steady discharge is 
produced through tubes excited from these machines. 

They are simple, and since they dispense with batteries and induction 
coils have much to recommend them; unfortunately, however, they behave 
in the most erratic fashion, the polarity being subject to reversal whenever 
rotation of the disks is discontinued, this, of course, being a serious disad- 
vantage. 

The most general method employed for excitation is by induction coils, 
giving high potentials at the terminals of the secondary winding. 

The induced current in the secondary winding is not, however, uni-direc- 
tional, but alternating in character. The wave form of the secondary 
current, while alternating, is not uniform, i.e., the induced E.M.F. due to 
rupturing the current in the primary circuit greatly exceeds the induced 
E.M.F. produced by closing the primary circuit, or, in other words, the in- 
duced E.M.F. at break is greater than E.M.F. of make. 

Fig. 5 shows the manner in which the current in the primary circuit 
varies. 



^Break 



■iBreak 




TIME 



Fig. 5. 



Because of the inductance of the coil, the current does not immediately 
reach its maximum value, but increases logarithmically as indicated by that 
portion of the curve marked "closed." 

The inclination of the curve, or the rapidity with which it reaches its 
maximum, will vary with the constants of the circuit for each particular coil, 
but Fig. 5 shows the general form of the current curve. The rapidity 
with which the current changes in a circuit is proportional to the time con- 
stant of the circuit or L/R, in which L is the self-induction and R the resist- 
ance of the circuit. 

When the circuit is ruptured, however, the time within which the current 
(alls to zero, depending upon the ratio of the inductance (L) and resistance 



X-RAYS. 



1253 



(R) of the circuit, is greatly diminished because R is increased enormously, 
due to opening the circuit. The ratio L/R, and consequently the time in 
which the current falls to zero, is very small as compared with the corre- 
sponding values on closing the circuit. 

Since the induced E.M.F. in the secondary circuit is proportional to the 
rate of change of magnetic lines through the turns of the secondary coil, it is 
evident that the induced E.M.F. of break will greatly exceed that of make, 
as the current of the primary circuit changes very much more rapidly in the 
former case than in the latter. 

Usually the E.M.F. due to closing the primary circuit is not of sufficient 
intensity to excite the tube, so, for this purpose, the current from the sec- 
ondary of an induction coil may be considered as uni-directional. 

Interrupters. — Interrupters for opening and closing the primary 
circuit should have the following characteristics: (1) Uniformity of inter- 
ruption, (2) high frequency, and (3) completeness^ of interruption. With 
respect to frequency of interruption there are limitations imposed by the 
properties of the iron core, and the disposition and number of turns of wire 
composing the coil. 

Since the primary current does not instantly reach its maximum value 
when the circuit is closed, a certain time must be allowed for this increase. 
If the speed of interrupter be such that the circuit is opened before the 
current has reached its maximum value, the full capabilities of the coil are 
not used. This condition is shown in Fig. 6, and the curves shown therein 
are for current in the primary with respect to time. 




k-c- 



k— C- 



fer-C— >- 



TIME 
Fig. 6. 



In the figure, the frequency of the interrupter is such that the circuit 
remains closedonly through the time interval indicated by the letter C, 
during which time the primary current has reached only a value shown by 
the height of the ordinate at the instant of interruption. 

A coil operating with an interrupter having too high a frequency may 
have its effectiveness increased if the E.M.F. impressed on the primary 
circuit be increased, thereby forcing the primary current to a higher value 
in the same time interval; on the other hand, the effectiveness may be 
increased under certain conditions by increasing the time of make and 
reducing the time of break, the frequency of the interrupter and the applied 
E.M.F. remaining the same. 

There are two general types of interrupters, viz., mechanical and electro- 
lytic. Many forms of mechanical interrupters have been devised and 
various designs are on the market in which provisions have been made for 
varying the frequency of interruption and the ratio of time of make and 
break. 

It is essential in all cases that the actual breaking oi the current should 



1254 



X-RAYS. 



(^ 



be as nearly instantaneous as possible, and to this end the spark forming 

between the breaking surfaces or points must be extinguished. In some 

instances sparking across contacts is obvi- 
ated by connecting a condenser across the 
interrupter, while in other designs the 
spark is blown out by a jet of air. 

The electrolytic or Wehnelt interrupter 
is shown in its simplest form in Fig. 7, 
and consists of two electrodes of widely 
dissimilar proportions, such as a platinum 
needle point and a large sheet of lead, im- 
mersed in a solution of dilute sulphuric 
acid. The platinum needle point is intro- 
duced into the electrolyte through a glass 
tube, the platinum being sealed into the 
glass, so that a very small area — practi- 
cally a point — is in direct contact with 
the electrolyte. If thesetwo electrodes 
be connected through an inductance to a 
source of supply, the current in the circuit 
will be subject to regular and rapid inter- 
ruptions. The platinum point electrode 
should be connected to the positive of the 
supply source. 

The speed of this type of interrupter is 
decreased by increasing the area of the 
positive electrode, other conditions re- 
maining the same, while increasing the 
applied E.M.F. increases the frequency 
and the current in the circuit. 
Fig. 8, shows complete diagram of connections for an X-ray outfit in 

which an electrolytic interrupter is made use of, the source of current supply 

being a storage battery. 



^E>- 



^^^^^ 



Fig. 7. 



Ammeter 




To .X.Ray 
s Tube 
i/ \ 

Spark Gap 



Inductance 




— 6=fo 



Induction Goil 



Fia. 8. 

As shown in the figure, a variable inductance is included in the circuit. 
This inductance is unnecessary if there is sufficient self-induction in the 
winding of the induction coil to properly operate the interrupter. 

A variable resistance is also included in circuit in order to vary the applied 
E.M.F. 



FLUORESCOPES. 1255 



FLIOREiCOPES. 

The phenomenon of fluorescence is the emission of visible light when X- 
rays or cathode rays strike certain substances. 

In transforming the energy of X-rays into light for the examination of 
radioscopic images some substance must be used which fluoresces under the 
action of the rays. Roentgen originally used barium platino-cyanide, and 
this is very largely used now, although various other substances, such as 
potassium platino-cyanide and calcium tungstate, are in use. 

Since the amount of light given out by a fluorescent screen is small, it is 
necessary to exclude all other forms of light either by carrying out the ob- 
servations in a dark room or by enclosing the screen in some suitable obser- 
vation chamber having an opening for the eyes. 

The chemicals used in preparing the fluorescent screen are applied to some 
support, this support in turn being fastened in the observation chamber. 
Various supports for the chemicals, such as cardboard, vellum, blackened 
on one side, and rubber, have all been more or less used. 



ELECTRIC HEATING, COOKING AND 
WELDING. 

Revised by Max Loewenthal, E. E. 

For definitions of Heat, Units, Joule's Law, etc., etc., see pages 3 and 4, 
"Electrical Engineering Units." 

Various Methods of Utilizing* the Heat Generated 
by the electric Current. 

1. Metallic Conductors (Uninterrupted Circuit). 

1. Exposed coils of wire or strips. 

(a) Entirely surrounded by air. 

(b) Wound around insulating material. 



2. Wire or strips of metal imbedded in enamel. 

(a) In the form of coils. ) Leonard, Simplex, Generj 
(6) In flat layers. J Crompton, and others. 



3. Wire or strips of metal imbedded in asbestos and other insulating 

materials, 
(a) In the form of coils. 
(6) In flat layers. 

4. Wire imbedded in various insulating compounds. 

(a) Crystallized acetate of sodium, etc. Tommasi. 

5. A Film of metal. 

(a) Rare metal fired on enamel. It>~_~xi„ m ,. 
lb) Rare metal fired on mica. J ±Tometneus. 
(c) Silver deposited on glass. Reed. 

6. Sticks of metal. 

(a) Crystallized silicon in tubes of glass. Le Roy. 

(6) Metallic powder mixed with clay and compressed. Parville\ 

7. Metal in the form of powder or granules. 

(a) Kryptol. 

8. Incandescent filaments in vacuum. 

(a) High wattage, low efficiency lamps. Dowsing, General 
Electric. 

II. Meat of the electric Arc (Interrupted Circuit). 

1. The electric furnace. Siemens, Cowles, Parker, and others. 

2. Heat of arc acting upon material, producing local fusion. 

Meritens, Werdemann, Bernardos, Howells, and others. 

3. Welding by bringing metals in contact. Thomson. 

4. Deflecting arc by magnet. Zerener. 

III. Hydro-electrothermic Sjstem, or Water-Pail Forg*e. 

Burton, Hoho and Lagrange. 

Referring to the above classification, Section I, the methods referred to 
under subheads 1 and 3 require no further explanation. The method unde* 

1256 



ELECTRIC HEATING, COOKING AND WELDING. 1257 

subhead 2 consists in imbedding the resistance wire in some fireproof insu- 
lation such as enamel or glass. This insulation is of comparatively poor 
quality as a conductor of heat, and so thin that it affords the least possible 
resistance to the flow of heat from the heated resistance. 

The Simplex System {Carpenter Patents, subhead 2), employs high resist- 
ance wire imbedded in an enamel, consisting of two parts, the ground mass 
and the surface. The former consists of silica, crystallized borax (for flux- 
ing), fluorspar and magnesium carbonate, mixed in various proportions, 
powdered and fused. To this is added aluminum silicate and pure powdered 
quartz. The enamel proper consists of flint meal, also tin oxide, saltpetre, 
ammonia carbonate, lead sulphate, magnesium sulphate, potassium car- 
bonate, borax, and sometimes gypsum and arsenic. These are carefully 
mixed, as too much of any ingredient will make the enamel crack off, or will 
make the fusion point too high or too low. The insulation resistance varies 
from 40 megohms when cold to 1000 ohms at 400° C. Most enamels melt at 
about 900° C. ; 

The Creneral Electric quartz enamel type unit (subhead 2), consists of 
spirals of "Climax" resistance wire electrically insulated from the surface to 
be heated by quartz enamel. The quartz grains are used as an excellent 
binder for the enamel. 

The Oeneral Electric cartridge type unit (subhead 3), consists of a 
German silver wire flattened into a ribbon and wound edgewise in a spiral. 
To insulate between the turns of this spiral it is dipped in a bath of insulating 
cement. The mass is then squeezed together, so that a thickness of insu- 
lating material of .003 inch remains between the turns. The spiral, forming 
a solid cartridge, is slipped into a brass or German silver shell, with only .01 
inch of mica between the edges of the ribbon and the shell. The heat, pass- 
ing through the thin thickness of mica is conducted to the outer shell and 
thence by direct contact to the surface to be heated. 

The Prometheus System (subhead 5) employs units composed of strips 
of mica about .004 inch thick, on which is painted a thin film of gold or plati- 
num, sometimes only .001 mm. thick. The metals, in the form of powders, 
are mixed with a flux and then painted on the mica, after which the whole is 
subjected to a high temperature, the finished films sometimes having a resist- 
ance of 100,000 ohms, each being made to consume not more than 70 watts, 
this giving a temperature of about 450° C. To prevent injury to the film it 
is covered with another strip of mica, and then together are partly enclosed in 
a thin metal frame. The insulation resistance of these strips varies from 50 
to 300 megohms, and the increase in the resistance of the foil varies from 10 
to 20 per cent during a period varying from 1 to 8 minutes. 

The Reed method or depositing a layer of silver on glass was described 
in the Electrical World, June 5, 1895. 

The method employed by JLelfcoy (subhead 6) consists of enclosing sticks 
of crystallized carbon, having a specific resistance 1333 as high as that of 
ordinary arc light carbon, in glass tubes. For 110 volts, rods are 100 mm. long, 
10 mm. wide, and 3 mm. thick. This takes about 150 watts; and having 
a surface of 26 sq. cm., the dissipation of heat is at the rate of about 5 kg. 
calories per sq. cm. of surface, or an absorption of electrical energy of 6 watts 
per sq. cm. of surface. 

Parville (VEclairage Elec, Jan. 28, 1899) uses rods of metallic powder, 
mixed with fusible clay (quartz, kaolin), compressed under a pressure of 2000 
kg. per sq. cm., and baked at a temperature of 1350° C. A rod 5 cm. long. 
1 cm. wide, 0.3 cm. thick, has a resistance of 100 ohms, and absorbs 16500 
watts per kg. One quart of water boils in 5 minutes with 15 amp. and 110 
volts. 

Kryptol (subhead 7) is a patented German substance, consisting of a 
mixture of graphite, carborundum, silicate and clay in a granular form. A 
bed of this refractory material has an electrode of carbon at each end. The 
size of Kryptol granules varies according to the voltage. The current is de- 
termined by the thickness of the bed. Temperatures up to 3600° F. may be 
obtained. During a test made by H. Allen, a cube of copper weighing 8.45 
grains was melted in one minute, the pressure being 240 volts and the current 
15 amperes. 

The above methods are utilized in the construction of electric cooking and 
heating apparatus, while those enumerated under Sections II and III are 
employed for purposes of welding, smelting, and forging. 



1258 ELECTRIC HEATING, COOKING AND WELDING. 



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ELECTRIC COOKING. 



1259 



ELECTRIC COOKING. 
Cost of Operating- Electric Cooking* 'Utensils. 

On account of the number of variables which enter into the determination 
of the cost of electric heating and cooking, it is impossible to present any 
general data. These variables may be classified as follows: 

1. Cost of current. 2. The skill of the operator from the cooking stand- 
point. 3. The skill of the operator from the standpoint of using the elec- 
trical apparatus economically. 4. The type of apparatus employed. 

It is possible, however, by assuming an arbitrary cost for current, to 
calculate the cost of heating a given quantity of water. Let it be required 
to heat one gallon of water at a temperature of 50° F. (10° C), without 
actually boiling it, to the boiling-point, or 100° C; it would then be elevated 
90° C. Hence 3786 cubic centimeters would be raised 90° C. or 3786 X 90 = 
340,740 water-gramme-degrees-centigrade of heat are produced. The unit 
corresponding to a water-gramme-degree-centigrade is the calorie, which 
requires an expenditure of 4.18 joules, so that the work required to be done 
in raising a gallon of water to the temperature of 100° C. is equal to 340,740 
X 4.18 = 1,424,293 joules. Assuming the cost of electric current, in large 
quantities, to be 5 cents per kilowatt-hour (which is equal to 3,600,000 
joules, as 1 joule = 1 watt per second), the cost of raising one gallon of water 
to the boiling-point is approximately 2 cents. If we assume the current to 
cost 15 cents per kilowatt-hour, then the cost would be 6 cents. 

This calculation, however, is strictly theoretical, as the assumption is 
made that all the heat generated is utilized in raising the temperature of 
the water. This, of course, is not the case, as a certain amount of the heat is 
transmitted to the metal vessel and the air during the time of the operation 
(about 15 minutes). Assuming the efficiency of the vessel to be 70 per cent, 
which represents the ratio between the useful and the total developed heat, 
then the actual cost of heating a gallon of water from 10° to 100° C. at a 
cost for current of 5 cents per kilowatt-hour would be 2 X V°o° = 2.86 cents, 
or at 10 cents per kilowatt-hour would be 2 X 2.86 = 5.72 cents. 

An approximate rule (according to Roger Williams) for estimating the 
amount of energy required to raise the temperature of a quantity of water in a 
given time, by means of an electrically heated pot is: 

One-third watt will raise one pint of water 1° F. in one hour, or 300 watts 
will raise one pint of water from 70° F to 212° F in ten minutes. 

Cost of Heating* Water to Different Temperatures at 
Various Rates for Electric Energy. 

James I. Ayer. 

Initial temperature of water, 60° F. Efficiency of apparatus, 85%. 



Total 
Temp. 
Deg. F. 


One Pint Watts Used for 


Cost in Cents with Current at 


5 m. 


10 m. 


20 m. 


1 Hour 


3 c. 


5 c. 


10 c. 


20 c. 


100 


164 


82 


41.04 


13.68 


.041 


.068 


.136 


.272 


150 


372 


186 


93 


31 


.093 


.155 


.31 


.62 


175 


468 


234 


117 


39 


.117 


.195 


.39 


.78 


200 


576 


288 


144 


48 


.144 


.24 


.48 


.96 


212 


624 


312 


156 


52 


.156 


.26 


.52 


1.04 






One Quart. 












100 


324 


162 


81 


27 


.08 


.136 


.272 


.544 


150 


744 


372 


186 


62 


.186 


.31 


.62 


1.24 


175 


936 


468 


234 


78 


.234 


.39 


.78 


1.56 


200 


1,152 


576 


288 


96 


.288 


.48 


.96 


1.92 


212 


1,248 


624 
One 


312 

Gallon. 


104 


.312 


.52 


1.04 


2.08 


100 


1,296 


648 


324 


108 


.32 


.544 


1.088 


2.17 


150 


2,976 


1,488 


744 


248 


.74 


1.24 


2.48 


4.96 


175 


3,744 


1,872 


936 


312 


.94 


1.56 


3.12 


6.24 


200 


4,608 


2,304 


1,152 


384 


1.15 


1.92 


3.84 


7.68 


212 


4,992 


2,492 


1,248 


416 


1.25 


2.08 


4.16 


8.32 



1260 ELECTRIC HEATING, COOKING AND WELDING. 



Efficiency of JElectric Cooking: Apparatus. 

According to Mr. Crompton, the efficiency of an ordinary cooking-stove 
using solid fuel is only about 2 per cent, 12 per cent being wasted in obtain- 
ing a glowing fire, 70 per cent going up the chimney, and 16 per cent ueing 
radiated into the room. 

In a gas-stove, considering that the number of heat units obtainable from 
the gas at a certain price is but small compared with solid fuel, the venti- 
lating current required for the operation alone consumes at least 80 per cent 
of the heat units obtained by burning the gas. 

In the case of an electrical oven, more than 90 per cent of the heat energy 
can be utilized; and thus, although possibly 5 to 6 per cent only of the heat 
energy of the fuel is present in the electrical energy, 90 per cent of this, or 
4£ per cent of the whole energy, actually goes into the food, and thus the 
electrical oven is practically twice as economical as any other oven, whether 
heated by solid fuel or by gas. 



240 

210 

u!180 

CO 

tu 

ill 150 

cc 

o 

gl20 
90 
60 















y 












S-s 












^ 


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4 




EATIN 


3 2 LBv 


I. OF V 


fATER 

!40. 

>40. 
86.1 










AVERAGE WATTS 
% EFFICIENCY 



















2 4 6 8 10 12 
MINUTES 

Fig. 1. 



Comparative Operating- Costs of Gas and Electric Cooking*. 

Report of Heating Committee, Association of Edison Illuminating 
Companies, September, 1905. 

The comparative operating cost of electric and gas cooking depends upon 
two questions, — the relative rates for gas and electric heat units, and the 
relative heat efficiencies of gas and electric apparatus. A third quantity — 
the effect produced by the different rates and modes of heat applications in 
the two classes of utensils — may effect the efficiency slightly, but the exist- 
ence of this effect is not yet verified. 

Starting with the heat of coal, which may be fairly estimated as 12,000 
B.T.U. per pound, we compute the relative efficiency of the heat conversion 
as follows: 



Gas. 

1 pound coal produces 5 cubic feet gas. 
5 cubic feet gas contain 3000 B.T.U. 
Efficiency heat conversion is 

^ = 25 per cent. 



Electricity. 

1 pound coal produces 0.25 K.W. 
0.25 K.W. contains 853 B.T.U. 
Efficiency heat conversion is 
853 _ - 
12000 =71perCent - 



Efficiency Electrical Heat Conversion _ 
Efficiency Gas Heat Conversion 



ELECTRIC COOKING. 



1261 



With manufacturing processes of equal cost per pound of coal converted, 
it is apparent, then, that an electric heat unit must cost nearly four times as 
much as a gas heat unit, but with present processes the relative rates are: 



..1» Gas. 

$1 .00 per 1,000 cubic feet. 
1 B.T.U. .000167 cents. 



1 



Electricity. 

).10per K.W.H. 
B.T.U. 0.00293 cents. 



Electric B.T.U. 0.00293 
Gas B.T.U. 0.000167 



17.5. 



It is known that the efficiency of electrical apparatus is about four times 
that of gas, and, consequently, as the gas utensil requires four times as many 
B.T.U., the above figure of 17.5 is reduced to 4.4. If, then, the rate for 
electricity is reduced to one-quarter of that assumed, or 2 . 5 cents per K.W.H. 
this figure of 4.4 is changed to 1.1, and we have practically identical 
operating costs. 

Comparison between Ga» and Electric Rates. 

According to James I. Ayer (report for National Electric Light Associa- 
tion, May, 1904) electric heat at an average efficiency of seventy per cent 
equals .4197 K.W.H. per 1,000 effective heat units, and for 105,000 effective 
heat units there would be required 44.065 K.W.H. to give the same results. 
To compete with gas at equal rates, electricity will have to be sold 



at 5.67 cents per K.W.H. where gas is at $2.50 per 1,000 cubic feet, 
at 4.54 cents per K.W.H. where gas is at 2.00 per 1,000 cubic feet, 
at 3.40 cents per K.W.H. where gas is at 
at 2.83 cents per K.W.H. where gas is at 
at 2.27 cents per K.W.H. where gas is at 



1.50 per 1,000 cubic feet. 
1.25 per 1,000 cubic feet. 
1 .00 per 1,000 cubic feet. 

The above is as fair a comparison as can be made where exact figures 
cannot well be secured. The results above quoted have been checked by 
records made in the same family alternately using gas and electricity each 
week for considerable periods in a number of cases, and from a variety of 
records obtained otherwise. It is assumed that suitable equipments both 
of electric and gas appliances are used. 

Cost of Operating- Electrically Heated Utensils. 



Article. 


Average 
Watt Hour 
Consump- 
tion. 


Period of 
Operation. 


Cost Dur- 
ing that 
Period at 
10 cts. per 
K.W.H. 


Chafing dish 

Pint baby milk warmer and food heater 

Quart food heater 

Coffee percolator 


400 

250 

500 

300 

500 

800 

1,200 

60 

250 

500 

500 

500 

300 

300 

200 

1,000 

1,000 

50 


Minutes. 

20 
6 
6 

20 

15 

15 

15 

15 

30 

30 

30 

12 

20 

20 

30 

30 

30 
per hour 


Cents. 

i 
h 
1 


Stove, 6 inches 

Stove, 8 inches 


li 

2 


Broiler 9 X 12 inch 

Curling iron heater 

Iron 3| lbs 

Iron 6 lbs 

Frying pan (7 inches diameter) . . . 
Waffle iron 


3 

2| 
2| 

1 


Tea kettle 


1 


Glue pot, 1 quart 

Soldering iron, 2 lbs 

Doctor's sterilizer 

Bath room radiator 

Heating pad 


1 
1 
5 
5 
* 



1262 ELECTRIC HEATING, COOKING AND WELDING. 






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ELECTRIC HEATING. 1263 



Electric Irons for Domestic and Industrial Purposes. 

The advantages of electric irons over irons heated by gas, coal, or other 
fuel are as follows: Cleanliness, continuous operation, saving time and energy 
by eliminating the travel between iron and source of heat, concentration of 
heat, so that the iron only and not the room is being heated, improved san- 
itary conditions and practically uniform temperature of iron face. In view 
of a number of these advantages, it has been found in actual practice that an 
average family of five persons, where the collars and cuffs are sent out to be 
ironed, consumes about 13.2 kilowatt hours per month for ironing, which 
at the 10 cent rate per K.W.H. amounts to SI .32 per month, which is about 
the same as if gas were used, costing $1 .00 per 1,000 cubic feet. The cost 
of operation varies with size of iron. For ordinary domestic requirements, 
without a current regulator, the iron most commonly used is one weighing 
about six pounds and consuming about 500 watts per hour. The regulators, 
whether of the switch in the handle or resistance in the stand type, effect a 
saving of from 15 to 20 per cent. The power consumption of the various 
types of irons is as follows: 

Watts 

4 pounds Troy Polishing, diamond face 330 

3i pounds Small Seaming (can be connected to lamp socket) . . 200 

4 pounds Gentleman's Small Hat Iron 200 

5^ pounds Light Domestic 500 

b% pounds Light Domestic, round nose 500 

7 pounds Domestic 600 

5£ pounds Morocco Bottom 500 

Morocco Bottom, round nose 500 

Commercial Electric Laundry Equipment. 

(At Eshleman & Craig Company, Philadelphia, Pa.) 

Watts 

7-5 pounds Sad Irons each 3.25 Amp. at 110 V. 2502 

2-7 pounds Sad Irons each 3 .80 Amp. at 110 V. 836 

2 Body Ironers each 41 .50 Amp. at 110 V. 9130 

2-12 inch Sleeve Ironers each 12.40 Amp. at 110 V. 2728 

1 Collar and Cuff Ironer each 6.50 Amp. at 110 V. 715 

3 Bosom Ironers each 16.80 Amp. at 110 V. 5544 

1 Rotary Collar Edger each 2.50 Amp. at 110 V. 275 

1-7 pound Sad Iron each 23.00 Amp. at 24 V. 552 

2-7 pound Sad Iron each 24.00 Amp. at 24 V. 1152 

1 Collar Edging Machine each 6.25 Amp. at 20 V. 125 

1 Heim Collar Shaper each 5.50 Amp. at 20 V. 121 

Total Equipment 23.68 K.W. 
A full description of "A Model Electrically Operated Laundry," by H. S. 
Knowlton may be found in the July, 1905, issue of The Electrical Age, New 
York. 

ELECTlll'C HXATIIG. 

Unless electricity is produced at a very low cost, it is not commercially 
practicable to heat residences or large buildings. While this is true, the 
electric heater still has a field of application, in heating small offices, bath- 
rooms, cold corners of rooms, street railway waiting rooms, the summer villa 
on cool evenings, and in mild climates a still wider range. It has the peculiar 
advantage of being instantly available, and the amount of heat is regulated 
at will. The heaters are perfectly clean, do not vitiate the atmosphere, and 
are portable. 

Radiators and Convectors. 

{Prometheus Electric Company of England.) 

The heating of rooms and buildings can be accomplished either by radiant 
or convected heat. With the former method heating is effected by the 
agency of glow lamps, and with the latter by resistances working at com- 
paratively low temperatures. 



L264 ELECTRIC HEATING, COOKING AND WELDING. 

In the glow lamp type the filaments of the lamps are raised to an exceed- 
ingly high temperature, and the electric energy is transformed mainly into 
radiant heat, only a small portion being given off by conduction and con- 
vection — hence the name 'radiator." 

In the non-luminous type the resistances are either bare or embedded in 
^namel and raised to a comparatively low temperature, which heats the air 
in contact with them, thereby setting up convection currents in the air. 
They are generally designated as radiators, though the term is a misnomer. 
They should rather be named "convectors or air warmers." The difference 
between these two methods of heating is a very wide one. The best method 
to employ depends entirely on the nature of the work for which the heaters 
are required, as explained below. 

Heating 1 l*y Radiation. — The heat from glow lamp radiators 
has been likened to sunshine. The analogy is excellent and has no doubt 
induced many non-technical people to universally employ this type of heat- 
ing in preference to any other, regardless of the nature of the work which 
they desire it to perform. 

It is very necessary in deciding which type of heater will give the most 
satisfactory results, to know the purpose for which it is to be used, and the 
conditions under which it will work. 

Radiant heat only raises the temperature of a body which is opaque 
to heat waves ; it passes through the air without heating it in the slightest, 
and only causes a rise of temperature in the air by heating any objects that 
offer opposition to its passage through them, these in turn heating the air in 
contact with them by conduction. 

Heat waves are unaffected by air currents and the glow lamp radiator is, 
therefore, suitable for warming oneself by out of doors, in balconies, etc., or 
for quickly warming any portion of one's body. The light emitted is also 
considered by some people to add greatly to the attractiveness of the heater. 

The heat rays are reflected forward by means of highly polished reflectors 
placed at the back of the lamps, and strike against any objects in their path. 
The zone of action is dependent on the shape of the reflectors, which for 
constructional reasons are made in simple shapes, confining the heating field 
to a small area. 

The temperature to which the glow lamp radiators will raise any opaque 
body when placed in any definite position relative to the lamps is dependent 
on the density of the heat rays on the surface on which they fall, from which 
no doubt has arisen the popular fallacy that a radiator, in front of which it 
is uncomfortable to hold one's hands, must be emitting more heat than a 
convector, in front of which they may be kept for any length of time without 
any sense of discomfort. The only true measure of the rate at which heat is 
being developed by two different heaters working under exactly similar con- 
ditions is the amount of air heated per unit of time multiplied by the tem- 
perature through which it is raised. Thus a heater constructed to work at 
a very low temperature may be giving out far more heat than one working 
at a high temperature, though the former would appear to be the more 
powerful of the two if gauged merely by the sensation produced on putting 
one's hands close to the flames. 

Air warming by radiant heat is an indirect method by which uniformity 
of temperature throughout a room or building can never be attained. It 
is of the utmost importance that the temperature be uniform, as freedom 
from draughts and consequent comfort and healthy conditions cannot other- 
wise be secured. 

Heating: oy Convection. — The heat generated in the resistance 
warms the body of the convector, and the air is heated by direct contact with 
the hot surfaces. Convection currents are consequently set up in the neigh- 
boring air, which quickly equalizes the temperature throughout the room 
in which the convector is placed. This method of heating dwelling rooms 
is, therefore, under normal conditions, far more efficient than that of radia- 
tion, provided the temperature of the resistance material is not high enough 
to materially affect the humidity of the air. Convectors are not, however, 
in virtue of the comparatively low temperature at which they work, so 
efficient as radiators for quickly warming one's hands or any portion of one's 
body, neither can they compete with radiators when very strong air currents 
are present, or for open air work such as balconies, band stands, etc. 

It has been asserted that convectors do not, like radiators, accomplish 
useful work as soon as they are switched in. Such broad statements are 



ELECTRIC CAR HEATING. 1265 



not based on facts as the relative rate of air heating by a radiator or convec- 
tor, absorbing the same power, depends entirely on their capacity for heat. 
Naturally a convector with a heavy cast iron frame will absorb a large quan- 
tity of heat before it can work at its maximum efficiency, but all the heat 
that is stored in the frame is, of course, taken up by the air after the convector 
is switched off; such convectors, therefore, are suitable only for continuous 
work over long periods. 

Energy Consumption of Electric Heaters. 

According to Houston and Kennelly, one joule of work expended in 
producing heat will raise the temperature of a cubic foot of air about fe° F. 

The amount of power required for electrically heating a room depends 
greatly upon the amount of glass surface in the room, as well as upon the 
draughts and admission of cold air. 

An empirical rule, commonly employed, is to figure from li to 2 watts 
per cubic foot of space to be heated. 

According to an European authority if a sitting-room with a content of 
100 cubic meters is to be heated to 17° C, while the temperature of the 
outside is 3° C, he estimates that 3,500 kilogram calories are required per 
hour; with electric heating this means a consumption of 4 kilowatt-hours 
for every hour, while with coal fuel, about 3 kilograms of coal are required 
per hour. Experience has shown, says the same authority, that for every 
degree Centigrade difference between the lowest outside temperature and 
the desired inside temperature and for every cubic meter of space to be 
heated 1 to 1.5 watts of electric power are required; as an approximate 
average 1 . 2 watts may be assumed. For instance, if the outside temperature 
is 10° C. below, and a sitting-room of 50 cubic meters is to be heated to 18° C, 
the difference of temperature is 28° C. Hence, 1,680 to 1,800 watts are 
required, while the time in which the desired temperature is obtained varies 
from one to three hours, varying of course, according to whether the neigh- 
boring rooms are heated or not. 

Comparison between Electric and Coal Heating*. 

A kilowatt-hour in heat is about 3,600 B.T.U., and costs a consumer in 
our large cities from 5 to 20 cents according to the conditions, or from 72,000 
to 18,000 thermal units per dollar. On the other hand a short ton of ordi- 
nary good steam coal will contain 28,000,000 of B.T.U. and allowing a loss 
of 25 per cent in a boiler wall and flue, some 21,000,000 of heat units can be 
looked for in boiler water, such coal costing from one to three dollars per ton 
according to circumstances, and representing a yield of 21,000,000 to 7,- 
000,000 of thermal units per dollar, or in the neighborhood of three hundred 
times more heat than the electric method would furnish. The comparison 
is in a certain sense unjust, seeing that the retail price of electric energy on 
a small scale is compared with manufacturing cost of fuel alone for heating 
water on a large scale, and a far better relative showing could be made where 
both methods were compared from either the manufacturer's or the pur- 
chaser's standpoint, whatever the scale of production might be. (Editorial 
Electrical World and Engineer.) 

ELECTRIC CAM UEATOO. 

At the Montreal meeting of the American Street Railway Association in 
1895, Mr. J. F. McElroy read an exhaustive paper on the subject of car- 
heating, from which the following abstracts are taken: 

In practice it is found that 20,000 B.T.U. are necessary to heat an 18 to 
20 foot car in zero weather. When the outside temperature is 12£° F. 
only 16,000 B.T.U. are required, etc., which shows the necessity of having 
electric heaters adjustable. 

The amount of heat necessary in a car to maintain a given inside tem- 
perature depends on: 1. The amount of artificial heat which is given to it. 
2. The number of passengers carried. The average person is capable of 
giving out an amount of heat in 24 hours which is equal to 191 B.T.U. 

This is evidently an error, as Kent says that a person gives out about 400 
heat units per hour; and tests by the Bureau of Standards show the same 
(413) for a person at rest, and about twice that for a man at hard labor (835)« 



1266 ELECTRIC HEATING, COOKING AND WELDING. 




Fig. 2. 

Cost of Car Heating-. 

The following table was compiled by Mr. McElroy from the reply re- 
ceived from the Albany Railway Company : 
Average fuel cost on Albany Railway, per amp. hour — .241 cent. 
Average total cost for fuel, labor, oils, waste, and packings per amp. 
hour = .423 cent. 





Cost of fuel per hour for heating a car 

with electric heaters with coal at 

$2.00 per 2000 lbs. 




Position of Switch. 




1st 


2d. 


3d. 


4th. 


5th. 




Amperes equal. 




2.14 


2.88 


6.88 


8.09 


12.0 


Simple high speed condensing . . 
Simple low speed condensing . . 
Compound high speed condensing 
Compound low speed condensing 


cts. 

.43 
.40 
.39 
.36 


cts. 

.58 
.54 
.52 

.48 


cts. 

1.40 
1.30 
1.27 
1.17 


cts. 

1.62 
1.51 
1.47 
1.36 


cts. 

2.41 
2.24 
2.20 
2.03 



Average Cost Per Day for Stoves. 

33 lbs. of coal at ,$4.55 per ton $.075 

Repairs 005 

Dumping and removing coal and ashes, coaling up 
and kindling fire, including cost of kindling, 

and part of cleaning car 100 

Removing stoves for summer, installing for win- 
ter, repairing head linings, repainting, etc., 

average per day 0125 

Total |Tl926 



ELECTRIC CAR HEATING. 



1267 



Diagrams of Wiring* for "Consolidated" Heaters 
for Use Along- Truss Plank. 



TROLLEY, 



SWITCH 



6-Heater Equipment 



*^*^ *Z 



16-Heater Equipment . orou^q 



24-Heater Equipment 



»C»* t« ip Lj.tC'»'CHC»'t>V -!■> - (..;:•« :-W[»." 


"■ ■ "'-»' 


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'I' 1 ■ , , ;Tr »i»'"i|r --r..^.M— ^ 





Truss Plank Heater in position, showing wiring in moulding. 
Fig. 3. 



1268 ELECTRIC HEATING, COOKING AND WELDING. 



Diagrams of Wiring* for fct Consolidated " Heaters 
for Cross Seats. 



8«H.e&ter Equipment 



12-Heater Equipment 



UJ 




ILl 




Cross Seat 'Consolidated" Heater in position. 
Fig. 4. 



ELECTRIC CAR HEATING. 1269 

According to a paper read by J. T. McElroy before the Street Railway 
Association of New York, on car heating, about 10 to 20 per cent of the 
energy required for running is spent in the heaters, and the average of tests 
taken upon American cars with coal and electric heaters for 15-hour runs 
gave the price per day of 15 hours for coal as $2.33, and for electricity $2.20. 

Pointers to Purchasers of Electric Car Heaters. 

(Street Railway Journal, November 5, 1904.) 

We think it only fair to the electric heater to call attention to a very 
common fault on the part of companies purchasing electric car heating 
equipments, which fault usually results in the end in a condemnation of 
electric heaters. This fault lies in trying to get along with a few heaters 
worked at a high temperature rather than a large number worked at a 
lower temperature. The reason why companies attempt to do this is, of 
course, to reduce the first cost of heater equipment. If a car is to be heated 
as comfortably by electric heaters as by hot water, the nearer you can come 
to distributing the heat evenly throughout the length of the car and avoiding 
excessively hot points, the better will be the results. It is coming to be 
more and more established, that heating of any kind can be done more 
efficiently by a large radiating surface worked at low temperature than by a 
small radiating surface worked at high temperature. Furthermore, working 
electric heaters at low temperatures is conducive to a long life, while working 
at high temperature is not. 

Industrial Electric Heating 1 . 

Among the industries to which electrically heated apparatus has been 
successfully applied may be mentioned: Book binderies, printing shops, 
hat factories, candy and chocolate manufactories, laundries, wood-working 
establishments, shoe, paper box, glove, corset, dental goods factories, as 
well as hotels, hospitals, restaurants, laboratories, bakeries, etc. In fact, 
wherever gas or steam is being employed for the localized application of 
heat, electricity has been found, in most cases, a more sanitary, flexible, 
safer, cleaner, as well as equally economical source of heat. 

Electric Heat in Printing* Establishments. — The most ex- 
tensive, as well as most economical, heating equipment in a printing office, 
is, no doubt, that at the Government Printing Office at Washington, D. C, 
designed and installed by the Hadaway Electric Heating Company. 

The following pieces of apparatus are being electrically operated success- 
fully at the present time (1907) in this office: 

Matrix Drying Tables. 

Wax Stripping Tables. 

Wax Melting Kettles. 

Case Warming Cabinet. 

Case Warming Table. 

Wax Knife, Cutting down Machine. 

Building up Tool Heaters. 

Sweating-on Machines. 

Soldering Iron Heaters. 

Embossing and Stamping Press Heads. 

Glue Heater Equipments. 

Glue Cookers. 

Case Making Machines. 

Book Cover Shaping Machines. 

Finishers' Tool Heaters. 

Pamphlet Covering Machines. 

Sealing Wax Melters. 

Further details of this equipment have been published in the Washington 
Electrical Handbook, issued in September, 1904, by the American Institute 
of Electrical Engineers, and a series of articles in the Electrical World and 
Enqineer, Vol. 43, pages 9-14, and succeeding issues. 

The claims made by the government representatives in favor of elec- 
erically heated apparatus as compared with steam and gas, are as follows: 



1270 ELECTRIC HEATING, COOKING AND WELDING. 



The absence of excess of heat that would be found in forms other than 
electrical. 

The ability to reduce the amount of time necessary to make impressions. 

The ability to bring the apparatus to a working condition in less time. 

The fact that in eight years of operation they have not had an instance of 
a burnt-out coil. 

electrically Heated Devices in the Printing* Shop of 
J?. JP. Collier & Son, Ufew York. 

The following list of apparatus is given here in order to show some of the 
details of this class of apparatus as well as the developments of this class of 
industry. 



Apparatus. 



Type and Size. 



Max 



Amp. Amp- 



Min. 



Volts 



Watts 



2 glue pots . 
23 glue pots 

1 glue pot . 
8 glue pots 

2 glue pots . 

2 wax heaters 
5 press heads 
1 press head 
1 press head 
1 press head 
1 press head 
1 press head 
1 press head 



Simplex 20 gal 

Hadaway 1 qt 

Simplex 1 qt 

Hadaway 2 qt 

2 gal 

22 in. X 24 in. X 3| in. 

22 in. X 24 in. X 3| in. 

22 in. X 24 in. X 3| in. 

22 in. X 24 in. X 3| in. 

22 in. X 24 in. X Si in. 

19 in. X 12 in. X 3f in. 

12 in. X 12 in. X 3$ in. 



100 
2 
2.5 

10 

22.8 
100 

35 

36 

36 

36 

36 

30 

25 



22 



2.5 

40" 
2.8 
4 

3.6 
3.5 
4.5 
2.5 
2.5 



110 
110 
110 
110 
220 
110 
110 
110 
110 
110 
110 
110 
110 



22,000 

5,060 

275 

8,800 

12,672 

22,000 

19,250 

3,960 

3,960 

3,960 

3,960 

3,300 

2,750 



111,947 



Forty-nine articles, consuming 112 Kilowatts. 
(11 Press Heads. 
Summary < 36 Glue Pots. 

( 2 Wax Heaters. 

Laboratory Use. — The milk supply of New York City is governed 
by tests made in the Laboratory of the Board of Health, by means of electric 
stoves. Twenty-five 4-inch disc stoves, of 60 watts capacity, are used to 
boil the ether used in the tests. Fourteen times per hour these little stoves 
cause the ether to vaporize. The germ producer, measuring 22X22X22 
inches, is heated to 130° C, by means of electricity, a maximum current of 
16 amperes being employed for 15 minutes every hour, while 3 amperes keep 
up the desired temperature. 

Coffee and Cocoa Dryeri. — The cocoa and coffee trade has applied 
electric heat to its small desiccating or drying cabinets. A dryer 3£ feet by 
5 feet, requiring a temperature of 150 degrees, requires about 74 watts per 
cubic foot when properly jacketed. The beans are particularly susceptible 
to the odors arising from combustion, hence the advantage of electric heat. 
For drying kilns 40 watts per cubic foot are recommended. 

Candy Manufacture. — Warming tables and chocolate dipping-pots 
have proved successful. Fifty watts produce sufficient heat to keep the 
chocolate in working condition. A 30-gallon tank holding caramel paste is 
supplied with 10 kilowatt hours to keep the paste at 285° C., and each melt- 
ing costs about 65 cents. The service is intermittent, hence the adapta- 
bility of electric heat. 

Soldering* and Branding* Irons. — The canning industry, as well 
as the makers of switchboards, and others, find the electric soldering iron 
a useful and economical tool. It has been found more economical to oper- 
ate electric soldering irons heated by current costing 5 cents per kilowatt hour 
than irons heated in gas furnaces, with gas at $1.00 per 1000 cubic feet. 
Heaters of 110- watt capacity are made, into which a soldering iron is thrust, 
thereby doing away with the connecting handle cord. One thousand hogs 
per hour are stamped, "Inspected," by the government meat inspectors in 
Chicago, by means of a 400-watt branding tool, which is an electric soldering 
iron with a die inserted in place of the copper tip. 



ELECTRIC WELDING AND FORGING. 



1271 



Thawing: Water Pipes. 

The following figures show the details of operation of a 44-cell storage 
battery outfit, mounted on an automobile truck, in comparison with those 
obtained by the use of a rheostat in series with a direct-current 3- wire Edison 
system with the neutral wire grounded. The figures represent the average 
amounts in each case. 





Am- 
peres. 


K.W. 
Hours . 


Time, 
Min. 


Pipe, 
Inch. 


Volt- 
age. 


Cost 

per 

Case. 


Revenue 
per Case. 


Storage battery 
Street supply . . 


513 
275 


1.39 
10.4 


5.44 
19.0 


1 

f 


31.5 
120.0 


$10.85 
14.43 


$16.40 
16.93 



The street supply is used until the season has so far advanced that the 
number of cases will warrant the exclusive service of an automobile truck. 



ELECTRIC WEEDING AND FORGING. 

The current employed in electric welding may be theoretically either 
continuous or alternating, but on account of the difficulty of producing low 
tension continuous currents, it is only practicable to employ alternating 
current. All electric welding machines are fitted with an alternating cur- 
rent transformer as an integral part of the machine. 

Thomson Electric Welding* Process. 

The principle involved in the system of electric welding, invented by Prof. 
Elihu Thomson, is that of causing currents of electricity to pass through 
the abutting ends of the pieces of metal which are to be welded, thereby 
generating heat at the point of contact, which also becomes the point of 
greatest resistance, while at the same time mechanical pressure is applied to 
force the parts together. The passage of the current through the metal at 
the point of junction, gradually but quickly brings the temperature of the 
metal to a welding point. Pressure follows up simultaneously, a weld being 
effected at once. 



Horse-Power Used in Electric W r elding > . 

The power required for the different sizes varies nearly as the cross sec- 
tional area of the material at the joint where the weld is to be made. 

Within certain limits, the greater the power, the shorter the time; and 
vice versa. 

The following tables are based upon actual experience in various works, 
and from very careful electrical and mechanical tests made by reliable 
experts. The time given is that required for the application of the current 
only, and may be shortened with a corresponding increase in the amount of 
power applied. 

Round Iron or Steel. 



Diameter. 


Area. 


H.-P. Applied 


Time in 






to Dynamo. 


Seconds. 


i in. 


.05 


2.0 


10 


1 in. 


.10 


4.2 


15 


£ in. 


.22 


6.-5 


20 


1 in. 


.30 


9.0 


25 


fin. 


.45 


13.3 


30 



1272 ELECTRIC HEATING, COOKING AND WELDING. 
Extra Heavy Iron JPipe. 



Inside 


Area. 


H.-P. applied 


Time in 


Diameter. 


to Dynamo. 


Seconds. 


i in. 


.30 


8.9 


33 


| in. 


.40 


10.5 


40 


1 in. 


.60 


16.4 


47 


H in. 


.79 


22.0 


53 


lh in. 


1.10 


32.3 


70 


2 in. 


1.65 


42.0 


84 


2£ in. 


2.25 


63.7 


93 


3 in. 


3.00 


96.2 


106 



General Table. 



Iron and Steel. 


Copper. 


Area in 


Time in 


H.-P. applied 


Area in 


Time in 


H.-P. applied 


sq. in. 


Seconds. 


to Dynamos. 


sq. in. 


Seconds. 


Dynamos. 


0.5 


33 


14.4 


.125 


8 


10.0 


1.0 


45 


28.0 


.25 


11 


23.4 


1.5 


55 


39.4 


.375 


13 


31.8 


2.0 


65 


48.6 


.5 


16 


42.0 


2.5 


70 


57.0 


.625 


18 


51.9 


3.0 


78 


65.4 


.75 


21 


61.2 


3.5 


85 


73.7 


.875 


22 


72.9 


4.0 


90 


83.8 


1.0 


23 


82.1 



\" square " 
\\" round " 


30 
35 


l£" square " 
2" round " 


1 40 
1 75 


2" square " 


90 



Axle l^elding*. 

1" round axle requires 25 Horse-power for 45 seconds. 

48 
60 
70 
95 
100 

The slightly increased time and power required for welding the square 
axle is not only due to the extra metal in it, but in part to the care which it 
is best to use to secure a perfect alignment. 

Tire TFelding'. 

1" x T 3 g tire requires 11 Horse-power for 15 seconds. 
\\" x §" " " 23 " " " 25 

l£"xf" " " 23 " " " 30 

\\" xf" " " 23 " " " 40 

2" x£" " " 29 " " " 55 

2" xf" " " 42 " " " 62 

The time above given for welding is of course that required for the actual 
application of the current only, and does not include that consumed by 
placing the axles or tires in the machine, the removal of the upset, and 
other finishing processes. 

From the data thus submitted, the cost of welding can be readily figured 
for any locality where the price of fuel and cost of labor are known. 



ELECTRIC WELDING AND FORGING. 



1273 



A test on the electric welding equipment of the American Steel Frame 
and Band Iron Company of New York, made by the New York Edison 
Company, to determine the amount of energy used per weld, gave the 
following result. The equipment consists of a 50 horse-power 220 volt, 
direct current motor, belted to a 50 kilowatt 220 volt, 2 phase, 60 cycle, 
separately excited alternator, and three 7.5 kilowatt step-down transform- 
ers, with an approximate ratio of 45 to 1. 

When welding iron frames .0352 square inch in cross section, it takes 
1 kilowatt hour, supplied to the transformer, to make 500 welds, the time 
required being 53 minutes. This averages 2 watt hours per weld, and 
taking the time the current is applied as 0.7 seconds per weld, the welding 
current figures out about 2000 amperes at 4.75 volts. A meter installed 
in the motor circuit showed 4 . 2 kilowatt hours direct-current input for 390 
welds, making an average of 10.77 watt hours per weld. 

Electric Rail Welding-. 

The "Electric " joint, applied by the Lorain Steel Co., is made by welding 
plate? on both sides of the web of the rail. The plates shown in Fig. 6 
are 1 inch by 3 inches, by 18 inches, and have three bosses, three welds 

DIAGRAM OF CONNECTIONS OF RAIL INCLDCR 

T * TROLLEY 

C . B'CI*0UIT BREAKE* 

R. R -RHEOSTATS 
M ■ tOOTQR 

e - booster 




R T • ROTARY TRANSFORMER 
W.T WELOtHG TRANSFORMER 
3 W' SWITCH 



R C-RB ACTIVE COIL 

trC'nuomo ua*p 



Fig. 5. 



SKETCH OF BAH USED IN WILDING 




O 




o 


t 
• 

• 


1 

J*..... -. / 


8' ■ 


^ 


1 


i 






■,..■ ?.. 






— *r 



Web Plates 

Fig. 6. 

being made at each joint. Great pressure up to 35 tons is maintained on 
the joint whilst making and cooling. The welding current runs as high as 
25, 000 amperes. The connections are shown in Fig. 5- 



1274 ELECTRIC HEATING, COOKING AND WELDING. 

Zerener System. 

In this system an arc is used in combination with a magnet which deflects 
the arc, making a flame similar to that of a blow-pipe, but having the tem- 
perature of the arc. The apparatus contains a self-regulating device 
which is driven by a small electric motor ; for welding iron a current of 40 to 
50 amperes- at 40 volts will suffice for strips of metal three mm. thick. 

Her na rd <>!* System. 

In this system the article to be operated upon is made to constitute one 
pole of the electric circuit, while a carbon pencil attached to a portable 
insulated holder, and held by the workman, constitutes the other pole, the 
electric arc — which is the heating agent of the process — being struck 
between the two poles thus formed. This system has been used extensively 
in England for the repair of machinery. The Barrbeat-Strange Patent 
Barrel Syndicate use this system for the welding of the seams of sheet- 
steel barrels. 

Voltex Process for Welding- and Brazing* 

Consists in the use of an electric arc formed between two special carbon 
rods inclined to each other at an angle of about 90°. The whole apparatus 
can generally be held in one hand. With gas and coke, gas costing only 
70 cents per 1000 cubic feet, it is claimed the complete cost of brazing and 
filling up a bicycle frame is $1.43, while with the Voltex process, at 6 cents 
per kilowatt hour, it is only 46 cents. 

Stassano Process of Electric Smelting* 

Consists of heating, in an arc furnace, briquettes composed of iron ore, 
carbon, and lime made into a paste with tar. The smelting process occurs 
in a blast furnace, the iron being reduced, and the siliceous matter of the 
ore slagged off. 

Annealing* of Armor Plate. 

The spot to be treated is brought to a temperature of about 1000 ° F. 
The current used is equivalent to 40,000 amperes per square inch, a density 
which is only possible by the use of cooling by water circulation. The 
operation generally takes seven minutes. 

HYDRO-ELECTROTHER^IIC sYsTEMS. 
S3«>ho and JLag-rang-e System. 

In this system an electrolytic bath is employed, into which an electric 
current of considerable E.M.F. is led, passing from the positive pole which 
forms the boundaries of the bath and presents a large surface to the elec- 
trolyte and thence to the negative pole, consisting of the metal or other 
material to be treated, and which is of relatively small dimensions. 

Through the electrolytic action hydrogen is rapidly evolved at the nega- 
tive pole and forms a gaseous envelope around the pole ; as the gas is 
a very poor conductor of electricity, a large resistance is thus introduced 
in the circuit, entirely surrounding the object to be treated. The current in 
"passing through this resistance develops thermal energy, and this is com- 
municated to the metal or other object which forms the negative pole. 

This system has been extensively used in England, and is described in 
The Electrical World, Dec. 7, 1895. 

Hurton Electric ITorg-e. 

In a patent granted to George D. Burton on an electrolytic forge, the 
portion to be heated is placed in a bath consisting of a solution of sal soda, 
or water, carbonate of soda, and borax. The tank is preferably made of 
porcelain or fire-clay. The anode plate has a contact surface with the 
liquid much greater than the area of contact of the article to be heated. 
This plate is composed of lead, copper, carbon, or other suitable conducting 
material. 



FUSE DATA. 



1275 



Fl'SE DATA. 

In a lecture on "The Rating and Behavior of Fuse Wires," before the 
A. I. E. E,, in October, 1895, Messrs. Stine, Gaytes, and Freeman arrived at 
the following conclusions: 

1. Covered fuses are more sensitive than open ones. 

2. Fuse wire should be rated for its carrying capacity for the ordinary 

lengths employed. 
2(a). When fusing a circuit, the distance between the terminals should 
be considered. 
On important circuits, fuses should be frequently renewed. 
The inertia of a fuse for high currents must be considered when 

protecting special devices. 
• Fuses should be operated under normal conditions to ensure cer- 
tainty of results. 
Fuses up to five amperes should be at least 1£ inches long, one-half 
inch to be added for each increment of five amperes capacity. 
7. Round fuse wire should not be employed in excess of 30 amperes 
capacity. For higher currents flat ribbons exceeding four inches 
in length should be employed. 

fuse Wire. 

The following table shows the sizes of fuse wire and the approximate 
current-carrying capacity of each size: 

Tested fuse IFire. 

(Chase-Shawmut Company, Boston.) 



3. 
4. 



5.- 

6. 



Carrying Capacity 
in Amperes. 


Standard Length 
in Inches. 


Diameter in 
Mils. 


Feet per Pound. 


f 


1* 


10 


2,700 


i 


if 


17 


950 


l 


1* 


20 


670 


li 


if 


23 


510 


2 


if 


25 


430 


3 


1! 


27 


370 


4 


30 


300 


5 


2 


35 


220 


6 


2 


38 


185 


7 


2 


44 


140 


8 


2 


47 


120 


9 


2 


54 


93 


10 


2 


58 


80 


12 


3 


62 


70 


14 


3 


68 


60 


15 


3 


70 


52 


16 


3 


73 


49 


18 


3 


78 


43 


20 


4 


86 


86 


25 


4 


90 


82 


30 


4 


100 


26 


35 


4 


110 


22 


40 


4 


122 


18 


45 


4 


126 


13 


50 


4 


147 


12.5 


60 


5 


160 


10.3 


70 


5 


172 


9.0 


75 


5 


178 


8.3 


80 


5 


190 


7.5 


90 


. 5 


198 


6.7 


100 


5 


220 


5.5 



1276 ELECTRIC HEATING, COOKING AND WELDING. 



Installation of fuses. 

(H. C. Cushing, Jr.) 

Enclosed fuses of standard sizes are now on the market and are preferable 
to link fuses. Where the link fuses are used they should have contact sur- 
faces of tips of harder metal, having perfect electrical connection with the 
fusible part of the strip. 

The use of the hard metal tip is to afford a strong mechanical bearing for 
the screws, clamps, or other devices provided for holding the fuse. 

They should be stamped with about 80 per cent of the maximum current 
they can carry indefinitely, thus allowing about 25 per cent overload before 
the fuse melts. 

The following table shows the maximum break distance and the separation 
of the nearest metal parts of opposite polarity for plain open link fuses, when 
mounted on slate or marble bases for different voltages, and for different 
currents: 

125 VOLTS OR LESS. 



Separation of 

Nearest Metal. 

Parts of Opposite 

Polarity. 



Minimum Break. 
Distance. 



10 amperes or less 
11-100 amperes 
101-300 amperes 



f inch 
1 inch 
1 inch 



f inch 
1 inch 
1 inch 



125 TO 250 VOLTS. 



10 amperes or less 
11-100 amperes . 
101-300 amperes 




1£ inch 
li inch 
1J inch 



Fuse terminals should be stamped with the maker's name, initials, or 
some known trade-mark. 

The lengths of fuses and distances between terminals are important points 
to be considered in the proper installation of these electrical "safety valves." 
No fuse block should have its terminal screws nearer together than one inch 
on 50 or 100 volt circuit, and one inch additional space should always be 
allowed between terminals for every 100 volts in excess of this allowance. 
For example: 

200 volt circuits should have their fuse terminals 2 inches apart, 300 volts 
3 inches, and 500 volts 5 inches. This rule will prevent the burning of the 
terminals on all occasions of rupture from maximum current, and this current 
means a "short circuit." 

Enclosed Fuses. — The "Enclosed Fuse " or "Cartridge Fuse," con- 
sists of a fusible strip or wire placed inside of a tubular holding jacket, 
which is filled with porous or powdered insulating material through which 
the fuse wire is suspended from end to end. The wire, tube and filling 
are made into one complete self-contained device with brass or copper 
terminals or ferrules at each end, the fuse wire being soldered to the inside 
of the ferrules. When an enclosed fuse "blows" by excess current, the 
gases resulting are taken up by the filling, the explosive tendency is reduced 
and flashing and arcing are eliminated. "D. & W.," "G. E.," "Noark" 
and "Shawmut," enclosed fuses are approved by the National Electric 
Code. 



LIGHTNING CONDUCTORS. 

Views concerning the proper function and value of lightning rods, con- 
ductors, arresters and all protective devices have undergone considerable 
modification during the past ten years. There may be said to be four 
periods in the history of the development of the lightning protector. The 
first embraces the discovery of the identity of lightning with the disruptive 
discharge of electrical machines and Franklin's clear conception of the 
dual function of the rod as a conductor and the point as a discharger. The 
second begins with the experimental researches of Faraday and the minia- 
ture house some twelve feet high, which he built and lived in while testing 
the effects of external discharges. Maxwell's suggestion to the British 
Association, in 1876, embodies a plan based upon Faraday's experiments, for 
protecting a building from the effects of lightning by surrounding it with a 
cage of rods or stout wires. The third period begins with the experiments 
of Hertz upon the propagation of electro-magnetic waves, and finds its most 
brilliant expositor in Dr. Oliver J. Lodge, of University College, Liverpool, 
whose experiments made plain the important part which the momentum 
of an electric current plays, especially in discharges like those of the 
lightning flash, and all discharges that are of very high potential and oscilla- 
tory in character. The fourth period is that of the present time, when 
individual flashes are studied ; and protection entirely adequate for the 
particular exposure is devised, based upon some knowledge of the electrical 
energy of the flash, and the impedance offered by appropriate choke coils 
or other devices. For example, under actual working conditions, with 
ordinary commercial voltages, effective protection to electrical machinery 
connected to external conductors may be had with a few choke coils in 
series with intervening arresters. 

A good idea of the growth of our knowledge of the nature and behavior 
of the lightning flash may be obtained from the following publications : 

Franklin's letters. 

Experimental Researches. . . .Faraday. 

Report of the Lightning Rod Conference, 1882. 

Lodge's "Lightning Conductors and Lightning Guards," 1892. 

"Lightning and the Electricity of the Air." . . . McAdie and Henry, 
1899. 

r— .„- -- 



FIQ. 1 EFFECT OF THE ACTION OF LIGHTNING 
UPON A ROD. 

That a lightning rod is called upon to carry safely to earth the discharge 
from a cloud was made plain by Franklin, and the effect of the passage of 
the current very prettily shown in the melting of the rod and the point 
(aigrette). 

Here indeed was a clew to the measurement of the energy of the lightning 
flash. W. Kohlrausch in 1890 estimated that a normal lightning discharge 
would melt a copper conductor 5 mm square, with a mean resistance of 0.01 
ohm in from .03 to .001 second. Koppe in .1895 from measurements of two 
nails 4 mm in diameter fused by lightning, determined the current to be 
about 200 amperes and the voltage about 20,000 volts. The energy of the 
flash, if the time be considered as 0.1 second, would be about 70,000 horse 
power, or about 52,240 kilowatts. 

Statistics show plainly that buildings with conductors when struck by 
lightning suffer comparatively little damage compared with those not pro- 
vided with conductors. The same rod, however, cannot be expected to 
serve equally well for every flash of lightning. There is* great need of a 
classification of discharges based less upon the appearance of the flash than 
upon, its electrical energy. Dr. Oliver J. Lodge has made a beginning with 

1277 



1278 



LIGHTNING CONDUCTORS. 



his study of steady strain and impulsive rush discharges. " The energy 
of an ordinary flash," says Lodge, " can be accounted for by the discharge 
of a very small portion of a charged cloud for an area of ten yards square 
at the height of a mile would give a discharge of over 2,000 foot-tons 
energy." 

We must get clearly in our minds then the idea that the cloud, the air, 
and the earth constitute together a large air condenser, and that when the 
strain in the dielectric exceeds a tension of ^ gramme weight per square 
centimeter, there will be a discharge probably of an oscillatory character. 
And as the electric strain varies, the character of the discharge will vary. 
Remember too that the air is constantly varying in density, humidity and 
purity. We should therefore expect to find, and in fact do, every type of 
discharge from the feeble brush to the sudden and terrific break. Recent 
experiments indicate that after the breaking-down of the air and the pas- 
sage of the first spark or flash, subsequent discharges are more easily ac- 
complished ; and this is why a very brilliant flash of lightning is often 
followed almost immediately by a number of similar flashes of diminishing 
brightness. The heated or incandescent air we call lightning, and the lines 
of fracture of the dielectric can be photographed ; but the electrical waves or 
oscillations in the ether are extremely rapid, and are beyond the limits of 
the most rapid shutter and most rapid plate. Dr. Lodge has calculated the 
rapidity of these oscillations to be several hundred thousand per second. 
Lodge has also demonstrated experimentally that the secondary or induced 
electrical surgings in any metallic train cannot be disregarded ; and, as in 
the case of the Hotel de Ville at Brussels which was most elaborately 
protected by a network, these surgings may spark at points, and ignite 
inflammable material close by. 

While therefore it cannot be said that any known system of rods, wires, 
or points affords complete and absolute protection, it can be said with con- 
fidence that we now understand Avhy " spitting-off " and " side " discharges 
occur ; and furthermore, to quote the words of Lord Kelvin, that " there is 
a very comfortable degree of security . . . when lightning conductors are 
made according to the present and orthodox rules." 

Selection and Installation of Rods. — The old belief that a 
copper rod an inch in diameter could carry safely any flash of lightning is 
perhaps true, but we now know that the core of such a rod would have little 
to do in carrying such a current as a lightning flash, or, for that matter, any 
high frequency currents. Therefore, since it is a matter of surface area 
rather than of cubic contents, and a problem of inductance rather than of 
simple conductivity, tape or cable made of twisted small wires can be used 
to advantage and at a diminished expense. 

All barns and exposed buildings should have lightning rods with the neces- 
sary points and earth connections. Ordinary dwelling-houses in city blocks 
well built up have less need for lightning conductors. Scattered or isolated 
houses in the country, and especially if on hillsides, should have rods. All 
protective trains, including terminals, rods, and earth connections, should 
be tested occasionally by an experienced electrician, and the total resist- 
ance of every hundred feet of conductor should not greatly exceed one ohm. 
Use a good iron or copper conductor. If copper, the conductor should 
weigh about six ounces per linear foot ; if iron, the weight should be about 
two pounds per foot. A sheet of copper, a sheet of iron, or a tin roof, if 
without breaks, and fully connected by well soldered joints, can be utilized 
to advantage. 





a b 

FIG. 2 AND 3 APPROVED CONDUCTORS AND FASTENINGS. 



PERSONAL SAFETY DURING THUNDER-STORMS. 1279 

In a recently published* set of Rules for the Protection of Buildings from 
Lightning, issued by the Electro-Technical Society of Berlin, Dr. Slaby gives 
the results of the work of various committees for the past sixteen years 
studying this question. The lightning conductor is divided into three parts, 

— the terminal points or collectors, the rod or conductor proper attached to 
the building, and the earth plates or ground. All projecting metallic sur- 
faces should be connected with the conductors, which, if made of iron, 
should have a cross section of not less than 50 mm square (1.9 sq. inches) ; 
copper, about half of these dimensions, zinc about one and a half, and 
lead about three times these dimensions. All fastenings must be secure and 
lasting. The best ground which can be had is none too good for the light- 
ning conductor. Eor many flashes an ordinary ground will suffice, but there 
will come occasional flashes when even the small resistance of ^ ohm may 
count. Bury the earth plates in damp earth or running water. The plates 
should be of metal at least three feet square. 

" If the conductor at any part of the course goes near water or gas mains, 
it is best to connect it to them. Wherever one metal ramification ap- 
proaches another, connect them metallically. The neighborhood of small 
bore fusible gas pipes, and indoor gas pipes in general, should be avoided." 

— Dr. Lodge. 



«s* 




IP- 

^1 


:o 




C "a 




7 ~ 4 " M 









FIG. 4 CONDUCTORS AND FASTENINGS*. 
(FROM ANDERSON, AND LIGHTNING ROD CONFERENCE.) 



The top of the rod and all projecting terminal points should be plated, or 
otherwise protected from corrosion and rust. 

Independent grounds are preferable to water and gas mains. Clusters of 
points or groups of two or three along the ridge rod are good. Chain or 
linked conductors should not be used. 

It is not true that the area protected by any one rod has a radius equal 
to twice the height of the conductor. Buildings are sometimes, for reasons 
which we understand, damaged within this area. All connections should 
be of clean well-scraped surfaces properly soldered. A few wrappings of 
wire around a dirty water or gas pipe does not make a good ground. It is 
not necessary to insulate the conductor from the building. 

H. W. Spang gives the following estimate of increase of property destri c- 
tion by lightning from the "Chronicle Fire Tables." 

Property loss. 

$ 8,879,745 
11,315,414 
21,767,185 



ing five years 


No. of fires 


ending 




1892 


2,505 


1897 


5,637 


1902 


15,755 



* Electrotechnische Zeitschrift, 1901, May 29. 



1280 LIGHTNING CONDUCTORS. 



Much of this increase in property loss is said to be due to the great increase 
in the use of wire fences in the suburban districts, also to the vastly in- 
creased use of metal work inside of houses, such as metal lath, steam and 
water pipes, and all metal trimmings now used so much in exterior trim- 
mings. Electric wires and their containing tubes also attract lightning; in 
fact, all the metal work now used in modern building construction serves 
to attract lightning and convey it to the ground or store it up as in a con- 
denser, which, upon being released, is liable to cause a spark and thus set 
fire to adjacent inflammable material. 

It is said that grounded arresters as now employed in power stations in 
connection with outdoor overhead electrical conductors also invite light- 
ning discharges, which, if they take place in the interior of buildings, are 
liable to cause fire loss; and therefore, it is inadvisable to locate such light- 
ning arresters adjacent to wood-work or other inflammable material. Large 
electric signs on the roofs of buildings also serve to attract lightning, and 
being connected with the interior electrical wires, sometimes jeopardize the 
safety of the buildings. Electrical wires in the upper stories of our tall 
buildings are said to become highly electrified during a thunder storm, and 
lightning from these is liable to impair any underground electrical con- 
ductor connected therewith. 

Overhead network wires such as those used for electric light, telephone, 
telegraph and fire alarm, also attract lightning, and the discharges upon 
these wires seem to increase in proportion to the number of grounded 
lightning arresters connected therewith — so much so, that it is now com- 
mon to dispense with the lightning arresters in fire alarm boxes. ^ Where 
lead sheathings of underground circuits or conductors of all kinds are 
metallically connected with the track rails and return circuit of street rail- 
ways, lightning is also liable to be attracted, and discharges from it in some 
cases cause considerable damage. It is also said that the grounding of 
secondary transformer distributing systems at their neutral points has also 
resulted in lightning discharges to the impairment of lighting transformers. 

Mr. Spang suggests that rather than connect overhead circuits directly 
with grounded lightning arresters or to connect return circuits of railways 
with other metallic networks that are grounded, there should be employed 
an overhead parallel wire, which shall be thoroughly connected to earth 
at intervals, and which should preferably be located at the side of any over- 
head electrical circuit and parallel thereto; but experienced engineers who 
have made a thorough study of protection from lightning, show that this 
parallel conductor does not materially benefit the conditions. 

From the Underwriters' standpoint, therefore, the following rules are 
suggested as necessary for protection of buildings from lightning: 

1. The employment of suitable metallic conductors about the ridges, 
chimneys or other ordinary elevations above the roof, in connection with 
all metal work about the roof and also with all exterior and interior metal 
work, pipes, etc., all metallically connected together so as to provide numer- 
ous vertical metallic paths from the roof to the cellar and thereby consti- 
tute with the underground water, gas and other metal pipes, a diffusive 
system of metallic conductors about the roof and building and over the earth. 

2. The shunting of the gas meters by suitable wires or other metal 
conductors. 

3. The employment of two vertical iron or copper conductors along 
opposite sides of a church spire or a high chimney between a metal cross, 
weather vane or other suitable air terminal conductor upon the top thereof 
and the metallic conductors upon the roof, which are metallically con- 
nected with the underground water, gas and other metal pipes or other 
suitable ground connection. 

4. A system of wires or conductors with suitable air terminals above the 
roof of a barn, ice-house or storage warehouse and connected by at least 
four vertical conductors with ground connections distributed over a suitable 
aroa of adjacent earth, so that the atmospheric electricity will be diffused 
over a greater and better conducting area than that offered by the com- 
pactly stored hay, ice, etc. 

5. The placing of lightning arresters or other grounded protection de- 
vires employed with electrical circuits about buildings in iron or non-com- 
bustible boxes, attached to brick, stone or other non-combustible material 
or buildings and preferably upon the outside thereof. 



CHIMNEY PROTECTION. 1281 



CHIM.\£1 PROTECTION. 

The builders of chimneys have made an exhaustive study of lightning 
action and have developed a number of standard fittings for lightning rods. 
One form of lightning-rod point is shown in Fig. 5. 



2 Copper Cable to Ground L 



1 <5\* -» 



f .„ _ ^ |J H- *'~>j || 

Fig. 5. Detail of Lightning-rod Point. 

Usually four of these points are installed at the chimney top, connected 
together by a band, and having two or more conductors to the earth. 

The United States Government has investigated thoroughly the require- 
ments for chimney protection as summarized in the following paragraphs: 

1. Chimney Protection for Power Plants. — Lightning con- 
ductors shall be laid up in the form of a seven-strand cable and each strand 
laid up with seven copper wires of No. 10 B. and S. gauge. For chimneys of 
50 feet and less in height two lightning conductors shall be used. For 
chimneys over 50 feet up to and including 100 feet, three conductors shall be 
installed. For chimneys higher than 100 feet, four conductors shall be 
installed. All heights to be considered from ground level. All conductors 
or cables shall be symmetrically arranged about the chimney with one 
cable on the prevailing weather side of the chimney. Said lightning con- 
ductors or cables to be securely attached both mechanically and electrically 
to independent pure copper earth plates or bars. In cases where the chim- 
ney foundations have already been filled in, instead of earth plates, earth 
terminals may be used, composed of pure copper bars 3 by £ inches by 3 feet. 
In all cases the lightning conductor terminals shall extend to the ground 
water level, and in no case shall they extend to less than 15 feet from the 
ground surface. Earth plates shall consist of pure copper 3 by 3 feet by | 
inch. 

2. Application of Conductors to Chimney. — Each lightning 
conductor shall be secured to the exterior of the chimney by means of 
bronze or brass anchors, without the intervention of any insulators or insu- 
lating material whatever. The brackets for attaching ring or conductors to 
chimneys to be of high grade bronze or brass, composition of same to be 
submitted for approval, and to be fitted with approved clamps for securely 
gripping said conductors and making a good electrical connection there- 
with. The tongues or shanks of the anchors or brackets shall enter the 
masonry of the chimney a distance of at least 6 inches, and shall be at 
least I inch in thickness by 1 inch wide, terminating in a suitable head or 
angle to prevent the anchor from being pulled out of the masonry. 
Anchors to be attached to conductors at intervals of not over 10 feet, and 
M sweated " to the conductors with solder at intervals of 50 feet. Conductors 
to terminate within 5 feet of the top of the chimney, and to be connected 
through the agency of a suitable brass or bronze fitting and be soldered to a 
H D Y h inch ring of copper attached to the periphery of the chimney by 
brackets spaced not over 2 feet apart. Said brackets to enter the brick 
work a distance of at least 6 inches and to be of approved design with a 
tongue at least 1£ inches in width and J inch in thickness, with a suitable 
angle or head to prevent pulling out. All joints in the continuity of said 
copper ring, as well as between the continuity of the ring and conductor or 
conductors running down to the ground bars or plates and including the 
latter, to be scraped bright and after making a secure mechanical joint to 
be " sweated with solder." Said solder shall consist of one-half lead and 
one-half tin. All joints when finished shall be thoroughly washed off with 
Water to remove every trace of soldering salts, acids, or other compounds 



1282 



LIGHTNING CONDUCTORS. 



used. All joints secured by bolts or screws to be lock-nutted. In applying 
conductors where the chimney is already constructed, holes shall be drilled 
in the brick and said anchor brackets and anchors grouted in, the best 
Portland cement being used. 

3. Terminal Rods for JLig-li tiling- Conductors. — Copper ring 
shall be connected through the agency of clamps, insuring a good mechan- 
ical and electrical joint, with vertically arranged copper rods at least f inch 
in diameter and 10 feet in length. The joints to be " sweated with solder " 
as before described. Copper rods to be placed equidistant around this ring, 
and supported in a rigid position vertically through the agency of additional 
anchors set in the masonry and a copper spider resting on chimney top as 
shown in the drawings. Rods to be arranged with a uniform spacing of 
practically 4 feet. This is taken to mean, for example, that ten such 
vertical rods shall be provided for a chimney of 12 feet outside diameter of 
masonry at top. 

4. Discliarg-e Points. — Each rod shall terminate in a two-point brass 
aigrette, each spur or point of this aigrette to be at least 3f inches long, 
the bases of which spurs shall be at least § inch in diameter, tapering to a 
sharp and well finished point ; said aigrette to be provided with approved 
means to secure a strong mechanical and electrical joint with the vertical 
rods heretofore described and to which it is attached. The joints shall be 
" sweated with solder " as heretofore described. 

5. Chimney Rase Protection. — All lightning conductors shall be 
enclosed at bottom with a heavy galvanized-iron pipe of 1£ inch diameter, 
and extending 3 feet into the soil and 10 feet above. Said iron pipe to be 
provided with approved brackets to securely hold it to the chimney; 
brackets to be not over 3 feet apart. 

TE§T§ OF IICJHT.M^O RODS. 

All lightning rods should be tested for continuity and for resistance of 
ground plate each year, and the total resistance of the whole conductor and 
ground plate should never exceed an ohm. 

TESTS OF LIGHTNING RODS. 




THIS LEAD MUST BE 

SOLDFRED TO THE PIPE 

OR. OTHER EARTH SO AS 

TO HAVE NO RE8I8TANCE 

AT THIS JOINT. 



Fig. 6. Diagram of Connections for Test of Lightning Rods. 



ISOLATED ELECTRIC PLANTS. 1283 

The continuity and resistance of the lightning rods above ground can be 
measured with a'Wheatstone bridge. The resistance of the ground plate 
to earth can be determined from three resistance measurements ; from 
ground plate to each of two other grounds and from one to the other of 
these arbitrarily chosen grounds, as follows : 

To make the test, first determine the resistance of the lead wire l x and call 
it l x . Then connect E x and E 2 as shown in the diagram, call the result R x ; 
then connect E x and 2£ 3 , call the result R 2 ; connect E 2 and E 3 and call the 
result R 3 . 

Now, R x = l x + E x + E 2 and E 2 = R x - l x - E x 
R 2 = i t + E x + E3 and E 3 = R 2 - h - E x 
i?3 = E 2 4- E% 
solving, we have 

R x + R 2 — i?3 » 
E x - 2 *■ 

The resistance of the ground plate to earth is E x as calculated from the 
above formula. 

UIRECTIO^ FOR PER§0]¥AI SJLFJ3TY DVRO& 
IHl^DER §!ORM§. 

Do not stand under trees or near wire fences ; neither in the doorways of 
barns, close to cattle, near chimneys or fireplaces. Lightning does not, as 
a rule, kill. If a person has been struck do not give him up as beyond 
recovery, even if seemingly dead. Stimulate respiration and circulation as 
best you can. Keep the body warm ; rub the limbs energetically, give 
water, wine, or warm coffee. Send for a physician. 

THE ECOAOMY OW ISOLATED EJLJECTMC 1»JL 4 M TJL*. 
(By Isaac D. Parsons.) 

™ T1 \ e Rowing investigation was undertaken by the writer and 
Mr. Arnold von bchrenk in an attempt to ascertain which of the two meth- 
ods is the more economical in six classes of buildings in New York and to 

*S rn ^ e as nea fly as possible those conditions, either inherent in a class 
ot buildings or due to peculiarities of installation or management which 
materially influence the economy. The six classes referred to are: — 
Office buildings, loft buildings, department stores, apartment houses, 
hotels, and clubs and over two hundred and fifty buildings were visited 
in the effort to obtain reliable figures and to ascertain the various condi- 
tions ot operation. Of this number seventeen only were found where in- 
formation could be obtained which was reliable in every particular, and 
only these will be considered in detail, as the great variation in conditions 
even among similar buildings of the same class renders incomplete statis- 
tics of very doubtful value. 

The figures as to electrical output of each of these plants were obtained 
trom wattmeter readings or from hourly ammeter readings, and were veri- 

u . by ,P ers , onal observation of the instruments from which they were 
obtained, and were also checked by comparison with other buildings where 
similar conditions exist. In some cases, tests were made of the instru- 
ments to determine their accuracy. The figures recorded as the output 
ot a plant are in every case the total number of kilowatt hours supplied 
at the switchboard and used as light or power, and where a storage battery 
was installed its output only was considered. The expenses of the plants 
were divided into those of labor, gas, central-station auxiliary or break- 
down service, coal, water, ash cartage, oil and waste, repairs incandescent 
lamps and arc-lamp carbons, interest, depreciation, and sundry supplies 
not included in the foregoing. Figures concerning these items were ob- 
tained in most cases directly from the booJks of the chief engineer or owner 
and may be considered within very small limits absolutely accurate. Under 
the item labor are included the wages of all the engineers, firemen, oilers 



1284 LIGHTNING CONDUCTORS. 



and coal passers employed in the plant, excepting in a few cases where 
extra employees were required by a large refrigerating machine or similar 
apparatus. In these cases the wages of the extra men were deducted 
from the total. If it were determined what employees could be dispensed 
with were the plant not installed, and the wages of these men only were 
taken, it would give the true cost of labor chargeable against the plant. 
To decide this, however, was in most instances a rather uncertain and 
difficult problem, and it was thought fairer to include in the expenses the 
wages of all the employees, which, with the other items, give the total cost 
of running the building with a plant. Then, by adding to the expenses of 
the central-station service the cost of the labor necessary for heating, 
elevator supervision, etc., the total cost of running under the conditions 
of central-station supply can be found. The difference between the two 
results is the true amount gained or lost by the installation of the plant. 

The item coal includes that which is burned to generate the steam used 
for the engines driving the generators, for the feed pumps, and in most 
cases that used for the house pump and whatever live steam is used in 
heating the building. In many buildings, refrigerating machines, steam 
laundries, steam cooking apparatus, or pumps, received steam from the 
same boilers as the engines driving the dynamos; but in such instances 
figures from recent tests were available by which the amount of coal used 
for these purposes could be determined. 

With the central-station supply either a boiler or a connection with the 
street mains is required to obtain the steam necessary for heating the 
building, as well as for the hot-water supply and for running the house 
pump, unless it is operated electrically. To determine what extra sum 
must be added to the actual cost of current in order to find the total ex- 
pense of running the building from the central station, figures were ob- 
tained from two large loft buildings, an office building, and six apartment 
houses and hotels using steam for heating and for house pumps only, from 
which the cost of coal, labor, and water required for these purposes could 
be calculated. The expenses for coal were reduced to dollars per 1,000 
cubic feet heated, and showed practically constant factors, irrespective 
of the shape or size of the building, of $1.10 per 1,000 cubic feet for apart- 
ment houses, 90 cents per 1,000 cubic feet for office buildings, and 40 cents 
per 1,000 cubic feet for loft buildings. The cost of labor, which inc.;/.e. 
the wages of the firemen and the expense of elevator supervision, ha t > 
be determined in each particular case, but usually amounts to a sum ab^ut 
equal to the cost of coal. 

Interest was calculated in all cases at 5 per cent on the principal in- 
vested in the plant. Depreciation on dynamos, engines, and switchboards 
of 5 per cent, and on boilers, pumps, and steam piping of 8 per cent, war. 
considered liberal; and since, as a rule, the cost of the dynamos, engine:., 
and switchboards approximates two-thirds of the total cost of installation, 
and that of the boilers, pumps, and steam piping one-third, a uniform 
rate of 10/3 + 8/3, or 6, per cent was charged against the whole plant. If 
5 per cent of the original capital invested in the engines is set aside each 
year as a sinking fund, this sum will accumulate interest at 5 per cent, 
and at the end of fourteen and one half years the total of the amounts 
reserved, with compound interest, will equal the original cost of the engines; 
so that 5 per cent depreciation assumes a life of but fourteen and one-half 
years. Similarly 8 per cent depreciation on boilers assumes a life of ten 
years. As a matter of fact, both of these periods are much exceeded in first 
class modern installations. On storage batteries where depreciation is 
a somewhat doubtful quantity, it was taken as 10 per cent, which assumes 
a life of but seven years. The load factor in every case was calculated for 
the hours the plant was in actual operation. 

As regards load and other conditions of operation, all the buildings can 
be divided into two classes — those used for business purposes, such as 
office and loft buildings and stores, and these which are used for residential 
purposes — such as hotels, apartment houses, and clubs. In the former 
class a small uniform lighting load during most of the day is succeeded at 
about 3 p.m. by a heavy load lasting but a few hours, which after 7 p.m. 
again becomes very small. In the latter class the heavy load, instead of 
falling off in the evening, continues to 1 or 2 a.m., giving a more uniform 
load and a higher load factor. We will consider the business buildings first. 



ISOLATED ELECTRIC PLANTS. 



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FOUNDATIONS AND STRUCTURAL. 
MATERIALS. 

Revised by W. W. Christie. 
POWER S1ATIOIV CONSTRUCTION. 

Chart. 

By E. P. Roberts & Co. 



Sta- 
tion 



Steam 
Plant 



Boilers 



{Foundation 
Setting 
Stack 



Link V 



En- 
gines 



Water. 



Fuel 



Source 

Pumps and injectors, valves 

and gauges 
Heaters 
Sediment ( Blow off 

\ Mud drum 
( Steam pipe and 
J valve to heater 
] Entrained water, 
^Steam ^ separator 
f Placing in building 
I Placing in boiler 
j Removal of coke and ashes 
(^Removal of soot 
Air .... Supply to surface 
> Piping and valves 
Coverings 
Drains and drips 
Supports 
'"Foundation 
Steam to cylinder 
Oil to cylinder 
Steam from cylinder 
Water from cylinder 
Oil to engine 
Oil from engine 
Engine indicator 
f Steam to condenser 
<j Water to condenser 
(^ Water from condenser 



Elec- 
trical 
plant 



Connecting links 



jynamos 



Wire . 



fBelts 
. -i Shafts 
^Pulleys 
Foundation 
Lubrication 
Insulation 
Governing devices 
Measuring devices 
^Safety devices 
''Dynamos to switchboard 
Switchboards to line 
Track to dynamo 
^Distribution devices 



Foundations 
Lubrication 



< 



Dynamo governing devices 
Dynamo measuring devices 
Switchboard "j Feeder to measuring devices 
Safety devices 

^Cut-out and lightning arrester 
f Weatherproof 
Fireproof 
Build- < Ventilated 
, ing Light 

(^Provisions for cranes or other strains foreign to its func 
tions as a shelter. 

128^ 



1290 FOUNDATIONS AND STRUCTURAL MATERIALS. 



FOUNDATIONS. 

The term foundation designates the portion of a structure used as a base 
on which to erect the superstructure, and must be so solid that no move- 
ment of the superstructure can take place after its erection. 

As all foundations or structures of coarse masonry, whether of brick or 
stone, will settle to some extent, and as nearly all soils are compressible 
under heavy weight, care must be taken that the settlement be even all 
over the structure in order to avoid cracks or other flaws. Although it is 
quite general to make the excavation for all the sub-foundation without 
predetermining in more than a general way the nature of the subsoil, and 
then adapting the base of the foundation to the nature of soil found ; yet in 
large undertakings, where there may be question as to the bearing, borings 
are made and samples brought up in order to determine the different strata 
and distance of rock below the surface. Where foundations are not to be 
deep, or the soil is of good quality, a trench or pit is often sunk alongside 
the location of the proposed foundation, and the quality of the soil deter- 
mined in that way. 

foundations on Rock. 

The surface of rock should be cleaned and dressed, all decayed portions 
removed, crevices filled with grouting or concrete, and where the surface 
is inclined it should be cut into a series of level steps before commencing 
the structure. In such cases of irregular levels, all mortar joints must be 
kept as close as possible, in order to prevent unequal settlement. A still 
better way is to bring all such uneven surfaces to a common level with a 
good thick bed of concrete, which, if properly made, will become as incom- 
pressible as stone or brick. 

The load on rock foundation should never exceed one-eighth its crushing- 
load. Baker says " the safe bearing power of rock is certainly not less than 
one-tenth of the ultimate crushing strength of cubes. That is to say, the 
safe bearing power of solid rock is not less than 18 tons per square foot for 
the softest rock, and 180 for the strongest. It is safe to say that almost any 
rock, from the hardness of granite to that of a soft crumbling stone easily 
worn by exposure to the weather or to running water, when well bedded 
will bear the heaviest load that can be brought upon it by any masonry 
construction." Rankine gives the average of ordinary cases as 20,000 
pounds per square foot on rock foundations. Later in this chapter (page 
1322) will be found a table that gives the crushing load in pounds per square 
inch for most of the substances used in foundations and building- walls. 

foundations on Sand or Gravel, 

Strong gravel makes one of the best bottoms to build on; it is easily leveled, 
is almost incompressible, and is not affected by exposure to the atmosphere. 

Sand confined so that it cannot escape forms an excellent foundation, and 
is nearly incompressible. It has no cohesion, and great care must be used 
in preparing it for a foundation. Surface water must be kept from running 
into earth foundation beds, and the beds themselves must be well-drained 
and below frost-line. Baker says that a rather thick bed of sand or gravel, 
well protected from running water, will safely bear a load of 8 to 10 tons per 
square foot. Of course the area of the surface must be proportioned to the 
weight of the superstructure, and to the bearing resistance of the material, 
and for this reason it is common practice to spread the subfoundation to 
give it the proper area. Rankine gives 2,500 to 3,500 lbs. per square foot as 
the greatest allowable pressure on firm earths. 

Foundation on Clay. 

A good stiff clay makes a very good foundation bed, and will support 
great weight if care is taken in its preparation. Water must be kept away 
from it, and the foundation level must be below the frost-line. The less 
clay is exposed to the atmosphere the better will be the result. Baker 

g'ves as safe bearing power for clay 3,000 or 4,000 pounds per square foot, 
audard says a stiff clay will support in safety 5,500 to 11,000 pounds per 
square foot. 



FOUNDATIONS. 1291 



Foundation on Soft Carta. 

Where the earth is too soft to support the superstructure, the trench is 
excavated to a considerable width, and to a considerable depth below the 
frost-line ; then a bed is prepared of stones, sand, or concrete, the latter 
being most in use to-day. In fact, it is a common thing to cover the whole 
area of the basement of large power stations with a heavy layer of concrete, 
of a thickness sufficient to sustain not only the building-walls, but all ma- 
chine foundations. 

Sand makes a good foundation bed over soft earth, if the earth is of a 
quality that will retain the sand in position. Sand may be rammed in 
9-inch layers in a soft earth trench, or it can be used as piles instead of 
wooden ones, by boring holes 6 or 8 inches in diameter and say six feet deep, 
and ramming the sand in wet. It is necessary to cover the surface with 
planking or concrete to prevent the earth pressing upward. Alluvial soils 
are considered by Baker safe under a load of one-half to one ton per square 
foot. 

foundation on Piles. 

When the earth is unsuitable in nature to support foundations, it is com- 
mon to drive piles, on the tops of which the foundation is then built. 
When possible the piles are driven to bed rock, otherwise they are made of 
such length and used in such number as to support the superstructure by 
reason of the friction of their surfaces in the soil. Where the soil is quite 
soft it is also common to drive piles in large number all over the basement 
area in order to consolidate the earth, and make all parts of a better bearing 
quality. 

Piles must be driven and cut off below the water level, and a grillage of 
heavy timbers or a layer of broken stone and a capping of concrete must be 
placed on top of them for supporting the foundation. 

The woods most used for piles are spruce and hemlock in soft or medium- 
soft soils, or when they are to be always under water, hard pine, elm, and 
beech in firmer soils, and oak in compact soils. When piles are liable to be 
alternately wet and dry, white oak or yellow pine should be employed. 

Piles should not be less than 10 inches in diameter at the small end, nor 
more than 14 inches at the large end. They should be straight-grained, and 
have the bark removed. The point is frequently shod with an iron shoe, to 
prevent the pile from splitting, and the head is hooped with an iron band to 
prevent splitting or brooming. 

Safe Load on Piles. 

Rankine gives as safe loads on piles 1,000 pounds per square inch of head, 
if driven to firm ground; 200 pounds, if in soft earth, and supported by 
friction. 

Major Sanders, U. S. Engineers, gives the following rule for finding the 
safe load for a wooden pile driven until each blow drives it short and nearly 
equal distances: 

Weight of hammer in pounds X fall in inches 

Safe load in pounds = 8 x inches driven by last Mow 

Trautwine's rule is as follows : 

. „ M 3 VFall in feet X Lbs. wgt. of hammer x .023 
Extreme load m gross tons = inches driven by last blow + 1 

He recommends as safe load one-half the extreme load where driven in 
6rm soils, and one-sixth when driven in soft earths or mud. The last blow 
should be delivered on solid wood, and not on the " broomed " head. 

Piles under Trinity Church, Boston, support two tons each. 

Piles under the bridge over the Missouri River at Bismarck, Dakota, were 
driven into sand to a depth of 32 feet, and each sustained a load of 20 tons. 

A pile under an elevator at Buffalo, N. Y., driven into the soil to a depth 
of 18 feet, sustained a load of 35 tons. 



1292 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Arrange m ent of Piles. 

Under walls of a building piles are arranged in rows of two or three, spaced 
24 inches or 30 inches on centers. Under piers or machine foundations they 
are arranged in groups, the distance apart being determined by the weight to 
be supported, but usually, as above, from two to three feet apart on centers. 

Concrete Sub-foundation. 

As mentioned in a previous paragraph, concrete is now used to a very 
great extent for foundation beds, not only in soft earths, but to level up all 
kinds of foundation beds. 

Good proportions are by measure, using Portland cement : 

Cement, 1 part; coarse sand, 2 parts; broken stone, 5 parts. 

Only hard and sharp broken stone that will pass through a 1|~ or 2-inch 
ring should be used ; and the ingredients should be thoroughly mixed dry, 
and after mixing, add just as little water as will fully wet the material. 

Concrete should be placed carefully. It is never at its best when dropped 
any distance into place. It should be thoroughly rammed in six- or nine-inch 
layers, and after setting the top of each layer should be cleaned, wet, and 
roughened before depositing another layer over it. It is common practice to 
place side-boards in trenches and foundation excavations in order to save con- 
crete. This is economical, but not good practice, if the earth is even moder- 
ately firm, as filling out the inequalities makes the foundation much firmer 
and steady in place. Weight of good concrete per cubic foot is 130 to 160 lbs. 
dry. 

Foundations of Engines. 

John Young, Ayr, Scotland, says that brick is more resilient than concrete. 

Foundations should weigh 2J to 4 times that of its engine, depending on 
whether horizontal or vertical type, also on the outside forces, belt pull, 
direction, etc. 

He also advises a concrete bed 2 to 3 feet deep of Portland cement con- 
crete, and for large work, coating the earth under the concrete with asphalt 
before concrete is laid. 

This helps preventing rise of moisture in foundation masonry. 

Permissible Loads on foundation Beds. 

Piles, in firm soil, each pile, 30,000 to 140,000 lbs. 

Piles in made ground, each pile, 4,000 " 

Clay, 4,000 " 

Coarse gravel and sand, 2,500 to 3,500 •* 

Rock foundations, average, 20,000 " 

Concrete, 8,000 " 

New York City laws, no pile to be 

weighted with a load exceeding, 40,000 " 

New York City rule for solid nat- 
ural earth per superficial foot, 8,000 " 

Concrete foundations. 

One of the best foundations for engines or other heavy machinery is con- 
structed wholly of concrete, rammed in a mold of planking. The mold can 
be made of any desired shape ; the holding-down bolts placed by template, 
and the material rammed in layers not exceeding 12 inches thick. 

Re-info reed Concrete. 

Re-inforced concrete, or Concrete and Steel Construction, is being used 
quite extensively at the present time for bridges, foundations, retaining 
walls, floors, and even entire buildings. 

When made of the very best Portland cement and good sharp sand and 
hard broken stone all properly incorporated, and when the imbedding of the 
steel bars is carefully and conscientiously done, the results will prove satis- 
factory in that class of work for which it is adapted. 

Brick foundations. 

Only the best hard-burned brick should be used for foundations, and they 
should be thoroughly wet before laying. To insure a thorough wetting, the 



MORTARS. 1293 

bricks should be deposited in a tub of water. Bricks should be jmsh placed 
in a good rich cement mortar. Grouting should never be used, as it taKes too 
long to dry. Joints should be very small. A well-constructed brick founda- 
tion will break as easily in the brick as at the joints after it has been built 
for some time. 

Stone foundations. 

Rubble stone foundations should start with large flat stones on the bottom. 
Care must be taken that all are well bedded in mortar, and that the work is 
well tied together by headers. 

Dimension stone foundations are always laid out with the heavy and thick 
stones at the bottom, and gradually decreasing in height, layer by layer, to 
the top. A large cap-stone, or several if the size is too great for one, is often 
placed on top of the foundation. Care must be taken to bed each stone in 
cement mortar, so that the joints will be thin and yet leave all the spaces 
between the stones completely filled with mortar to prevent any unequal 
trains on the stone. In all large foundations use plenty of headers ; and if 
the backing or center is of rubble, see that all stones are well bedded, and 
the crevices filled with spawls anjl cement. 

I-Beam foundations. 

One of the best and now most common methods of constructing founda- 
tions for piers, walls, columns, etc., is the use of steel I-beams set in con- 
crete. Knowing the weight to be supported and the bearing value of the 
soil, excavation is made of the right dimensions to get the proper area of 
bearing, then I-beams of predetermined dimensions are laid parallel along 
the bottom, and held in place with bolts from one beam to the next. Concrete 
is rammed in all the spaces to a level with the tops of the beams. Another 
similar layer of beams is then laid on top of the first, and at right angles 
thereto, and the spaces also filled with concrete. The column base, or foot- 
ing course, is then set on the structure ready to receive the column. 

For method of calculation of dimensions of I-beams for use in foundations 
for piers and walls, the reader can consult the hand-book of the Carnegie 
Steel Company, and those of other Steel Companies. 

MORTARS. 
Lime Mortar. 

Good proportions are : 1 measure or part quicklime, 3 measures of sand, 
well mixed, or tempered with clean water. 

Quantity required. — Trautwine. 20 cu. ft. sand and 4 cu. ft. of lime, 
making about 22£ cu. ft. mortar, will lay 1,000 bricks with average coarse 
joints. 

Weigrht. — 1 bbl. weighs 230 lbs. net, or 250 lbs. gross ; 1 heaped bushel of 
lump lime weighs about 75 lbs. ; 1 struck bushel ground quicklime, loose, 
weighs about 70 lbs. Average hardened mortar weighs about 105 to 115 lbs. 
per cu. ft. 

Tenacity. — Ordinary good lime mortar 6 months old has cohesive 
strength of from 15 to 30 v lbs. per sq. inch. 

Adhesion to common bricks or rubble. — At 6 months old, 12 to 
24 lbs. per sq. inch. 

Cement Mortar. 

Good proportions are: 1 measure cement, 2 measures sand, £ measure 
water. The above is rich and strong, and for ordinary work will allow in- 
crease of sand to 3 or 4 measures. 

Quantity required. — Trautwine. 1 bbl. cement, 2 bbls. sand, will 
lay 1 cu. vd. of bricks with § inch joints or 1 cu. yard rubble masonry. 
Weig-ht.— 
American Rosendale, ground, loose, average, 56 lbs. per cu. ft. 

" " U. S. struck bushel, 70 " " " " 

English Portland, 81 to 102 " " " " 

" i per struck bushel, 100 to 128 " " " " 

" " per bbl. 400 to 430 " " " " 



1294 FOUNDATIONS AND STRUCTURAL MATERIALS. 

Ave rag- e Strength of Tfeat Cement after © Days in 
Water. 





Tensile, Lbs. 
per sq. in. 


Compress, Lbs. 
per sq. in. 


Compress, 
Tons per sq. ft. 


Portland, artificial . . . 

" Saylor's natural 

U.S. common hydraulic . 


200 to 350 
170 to 370 
40 to 70 


1400 to 2400 

1100 to 1700 

250 to 450 


90 to 154 
71 to 109 
16 to 29 


Cements are weakened by the addition of sand somewhat as shown in the 
following table : calling neat cement 1. 


Sand. 





* 


1 


1^ 


2 


3 


4 


5 


6 


Strength. 


1 


§ 


i 


.4 


* 


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S 


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Adhesion to Bricks or Rubble. 

Adhesion of cement, either neat or mixed with sand, will average about 
three-fourths the tensile strength of the mortar at the same age. 



SAX1> A*» CEMEIT. 

Recommendations of Am. Soc. Civil Engineers. 

Sand. — To be crushed quartz only. To pass, 
1st sieve, 400 meshes per square inch. 
2d " 900 " " " " 

Sand to pass the 400 mesh, but be caught by the 900 mesh, all finer parti- 
cles to be rejected. 

Portland Cement. — For fineness, to pass, 
1st sieve, 2500 meshes per square inch. 
2d " 5476 " " " " 

3d " 10000 " " " " 

Should be stored in bulk for at least 21 days to air-slake and free it from 
lime, as lime swells the bulk, and if not removed is apt to crack the work. 



I HO\ Al¥l> WTEEJL. 

Iron, weigrht of: cu. in. 

Cast, .2604 Lbs. 

Wrought, .2777 " 
a =*sectional area wrought-iron bar. 

x = weight per foot " " " 

3x 10a 



Steel, weigrht of: 



cu. in. 

.2831 Lbs. 



cu. ft. 

450 Lbs. 
480 " 



cu. ft. 

489.3 Lbs. 



Cast Iron. Test. 

Bar an inch square, supported on edges 1 foot apart, must sustain 1 ton at 
center. 



WEIGHT OF FLAT ROLLED IRON. 



1295 



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csoocoi>«oiOTt<cococoi-i©c^90oot^ococoooot-ioeo 


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1.88 
3.75 
5.63 
7.50 
9.38 
11.25 
13.13 
15.00 
16.88 
18.75 
20.63 
22.50 
24.38 
26.25 
28.13 
30.00 
33.75 
37.50 
41.25 
45.00 
48.75 
52.50 
56.25 
60.00 


.2 

5 


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00 


1.67 
3.33 
5.00 
6.67 
8.33 
10.00 
11.67 
13.33 
15.00 
16.67 
18.33 
20.00 
21.67 
23.33 
25.00 
26.67 
30.00 
33.33 
36.67 
40.00 
43.33 
46.67 
50.00 
53.33 


5 


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« ©«, 



WEIGHT OF BARS OF IRON. 



1297 



WEIGHTS Of §m IRE A\» ROMD BAJRS Of 

WROUGHT IHO.\ I* POVID8 PSA 

LOEAL FOOT. 



Iron weighing 480 lbs. per cubic foot. For steel add 2 per cent. 



© 


u 

o3 


u 


u 

© 


?3 


u 

93 


u 
© 

49 




u 

e3 


9 

B 




-3 fl 


© 
e3 . 


2* 


5 ao 

"2 9 


© 

g 

e3 . 


« . 
©*> 

u PS 






C8 O 


PS o 


'X M 


c! O 


S 9 


X SR 


C3 O 


PS o 


3 © 


02 O 


MS 


.d 


3^ 




Q © 




Si 


ps*"* 
.2 


So 


§o 


MM 

«•- 
,9 

O 






«5M 
® _ 
9 PS 

© 




H 


© 


© 


3 


55 


0) 


3 


© 


© 









15 


24.08 


18.91 


1 


96.30 


75.64 


* 


.013 


.010 


1 


25.21 


19.80 


7 
TB 


98.55 


77.40 


£ 


.052 


.041 


f 


26.37 


20.71 


* 


100.8 


79.19 


f 


.117 


.092 


27.55 


21.64 


T 9 B 


103.1 


81.00 


.208 


.164 


it 


28.76 


22.59 


1 


105.5 


82.83 


t 


.326 


.256 


3 T 


30.00 


23.56 


11 
TB 


107.8 ' 


84.69 


.469 


.368 


t 


31.26 


24.55 


I 


110.2 


86.56 


f 


.638 


.501 


32.55 


25.57 


ii 


112.6 


88.45 


.833 


.654 


f 


33.87 


26.60 


i 


115.1 


90.36 


& 


1.055 


.828 


35.21 


27.65 


ii 


117.5 


92.29 


f 


1.302 


1.023 


t 


36.58 


28.73 


6 


120.0 


94.25 


l J 


1.576 


1.237 


37.97 


29.82 


| 


125.1 


98.22 


1.875 


1.473 


f 


39.39 


30.94 




130.2 


102.3 


f 


2.201 


1.728 


40.83 


32.07 


| 


135.5 


106.4 


2.552 


2.004 


j% 


42.30 


33.23 


I 


140.8 


110.6 


11 


2.930 


2.301 


1 


43.80 


34.40 


146.3 


114.9 


1 


3.333 


2.618 


tt 


45.33 


35.60 


i 


151.9 


119.3 


A 


3.763 


2.955 


1 


46.88 


36.82 


I 


157.6 


123.7 


¥ 


4.219 


3.313 


ii 


48.45 


38.05 


7 


163.3 


128.3 


f 


4.701 


3.692 


1 


50.05 


39.31 


I 


169.2 


132.9 


5.208 


4.091 


if 


51.68 


40.59 


j 


175.2 


137.6 


T 5 5 


5.742 


4.510 


4 


53.33 


41.89 


181.3 


142.4 


I 


6.302 


4.950 


* 


55.01 


43.21 




187.5 


147.3 


& 


6.888 


5.410 


56.72 


44.55 


1 


193.8 


152.2 


I 


7.500 


5.890 


* 


58.45 


45.91 


f 


200.2 


157.2 


t 


8.138 


6.392 


60.21 


47.29 


I 


206.7 


162.4 


8.802 


6.913 


& 


61.99 


48.69 


8 


213.3 


167.6 


¥ 


9.492 


7.455 


I 


63.80 


50.11 


1 


226.9 


178.2 


10.21 


8.018 


7 
T5 


65.64 


51.55 


J 


240.8 


189.2 


if 


10.95 


8.601 


¥ 


67.50 


53.01 


| 


255.2 


200.4 


3 


11.72 


9.204 


t 


69.39 


54.50 


9 


270.0 


212.1 


it 


12.51 


9.828 


71.30 


56.00 


I 


285.2 


224.0 


2 


13.33 


10.47 


T§ 


73.24 


57.52 


h 


300.8 


236.3 


i 


14.18 


11.14 


t 


75.21 


59.07 


1 


316.9 


248.9 


15.05 


11.82 


f 


77.20 


60.63 


10 


333.3 


261.8 


t 3 b 


15.95 


12.53 


79.22 


62.22 


| 


350.2 


275.1 


{ 


16.88 


13.25 


iS 


81.26 


63.82 


I 


367.5 


288.6 


h 


17.83 


14.00 


83.33 


65.45 


1 


385.2 


302.5 


I 


18.80 


14.77 


* 


85.43 


67.10 


11 


403.3 


316.8 


t 


19.80 


15.55 


87.55 


68.76 


1 


421.9 


331.3 


20.83 


16.36 


t 


89.70 


70.45 


i 


440.8 


346.2 


• 

V 


21.89 


17.19 


91.88 


72.16 


i 


460.2 


361.4 


22.97 


18.04 


ft 


94.08 


73.89 


12 


480. 


377. 



1298 FOUNDATIONS AND STRUCTURAL MATERIALS. 





- 


qM»8eotcq«»8rtco8cooqnoq^«oi>wqNMOi>» 




lew 


OMOoooeoifltrOMioooONioooocoio 
ic«qt>oqo^c^^»ocqi>-coo^c<jcqiqcDt>occiOQOocovocoocoiftooOMio 

t>©CO©©CO©©C^O<»^OaO^T^t>Oed©©!^<»idi^lr^edc"cd<>ia6ifti^t^'- 




*-t» 


OiMMiOt»050rHMiCt>aOHCOU5t>aiOMt> 

OOioqi>;cqicio^cqc^rHoooooi>^iciqcqi^ooot>.iococ<i©cot^iccos^o 

Wh-OWW0iC^O00H^t>ONO00Hrt<NC0dindd(N00TlHdlOHNMffilft 




rt» 


OHNMM»ai0»flt*0000OOO(N«Tjiiau'5t-(»O 

^c<joj»eqot^rijrHooiocooi>ri;TH<»ioc^^o»oo5cot-c<ioo^cocot-iHiQ 

cccoco^^^^ioioioiococoot>t>i>t-oo^ocio©SS^M^^^SoS 




«w 


0150001001000010010008150080800000000000 








3 


QSJOOOONOO^MMCIHOCIOOOONOOMHOCSNW 

l5^©C0©«NWQ0rt^t : 5«iq00fH^N,«©§S5§00^O«0N00W0>lO 

N05?i^'-OWHeOlO»ONOt»C}H^doOeONNNrt« , c"u"c'T(ia«<»Nl>' 


V 


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QOOl^iflC^NOCONiOCONOOONiO«)MONCOgN«iOt>« 

99^ N .^^ L ^^^ w .^99^ N .^'* ir ?® ?9 r !wSbMowMiflt'Ooo 
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go 

£> 

S 

H 


•R 


oco^Hq»i>»»qMNH5coi>qiomNq^iqNqi>io^ONOMOooia 
c4^cdQoo^wot>cirHeo>d©woc4T*wo*cot^i^o*o6c4cdo*cot^^ido6c4 

INN^!NMMC0C0nc0^^^^^i0i0l0liaCi®Xt*^t»Q000O0>C5OOOH 


H« 


20.00 
21.67 
23.33 
25.00 
26.67 
28.33 
30.00 
31.67 
33.33 
35.00 
36.67 
38.33 
40.00 
41.67 
43.33 
45.00 
46.67 
48.33 
50.00 
53.33 
56.67 
60.00 
63.33 
66.67 
70.00 
73.33 
76.67 
80.00 
83.33 
86.67 
90.00 
93.33 
96.67 
100.00 




J® 


OOC^QOJO©0^t^COOO^OCOC<100COOOt>OOOC<JCOlOt>-QOQ'--ieOlO«0000 
HH(N!N^NW^(MCOC<:cOC<5MCCiCO^'*^^^Ol010« l »©NNI>t'000000 




«t» 






"H 


HHHHHHHHiNlNINlMiNC^^iN^eOCOWMCOM^^^^iOiOlOlOiO©^ 




*+* 


qooqioMHqooqoMHOoocoMHSocooqwqqwqqMqqMq 
dd^(Nd^dddt^o6dddr'(Nd^ddo6dHdii5do6dHMddad 




«R 


338$83a&8S3g$8S8S88S3g88SS8$8g88S£8SS 




H« 


223S*S!£?228^^22 w ^ wo ^w»ot>aooMt>oeot~©Mc-©e'5t~0£2^© 

q^»««oqwcjMi>;rjiflq^(»N©qoMHOM»ioeoHqoowiaMHq 
uj»o»d^©i>i^t>o6o6o50Jooo^^c4c4M^oidot^odo500^c^M^o 

H^^HHHHHHHHHHHHNfKNfflflfflM 




•« 


OHaMP5^ifl?ON(»OOa)OH(NMM'*iONQOONM«5t-OOQ(NMiOt-aiO 

lONaHcciONftHMio^q^^oooqiNcqiqfflMNHiaq^oqN^Dqiq 
c4c4c4cococdeocorj*^^*T^idididid»d^o»t>t^i>o6o6o50>oo*o"rM 


,d 


9 

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a 

M 


^tt^O©t~aO©©THC^<ttTt<lOCOr~00©©^^©aO©C<I'#COOO©<N , '-t<COOO© 



GAUGE FOR SHEET AND PLATE IRON. 



1299 



V. 8. 8T.OD.4RO GAUGE FOR SHEET A»D 
MATE IltO* AJ¥» STEEL. 1*0.1. 



& 


§,d 


o 




43 

ft 


43 


£ . 






3 
O 
o 

U 


©«- o 

!. s : 

M 3! 03 

O g w 


2*2 

.5 scL o 


o 

Si 5 

o ^o ,rH .5 


u a 3 


s- 3 3 


. 00 

col 

81 


©^ s 

ft ©08 

w>2 ° 


mi 

&8S3 


| 


ftfl° 

a^» a 


as s 3 


3 H i 


o ^ 


^22 


32 

©.a 


!§3 

0C.J3 




& 


S* 


ft 




► 


£ 


* 






0000000 


1-2 


0.5 


12.7 


320 


20. 


9.072 


97.65 


215.28 


000000 


15-32 


0.46875 


11.90625 


300 


18.75 


8.505 


91.55 


201.82 


00000 


7-16 


0.4375 


11.1125 


280 


17.50 


7.938 


85.44 


188.37 


0000 


13-32 


0.40625 


10.31875 


260 


16.25 


7.371 


79.33 


174.91 


000 


3-8 


0.375 


9.525 


240 


15. 


6.804 


73.24 


161.46 


00 


11-32 


0.34375 


8.73125 


220 


13.75 


6.237 


67.13 


148.00 





5-16 


0.3125 


7.9375 


200 


12.50 


5.67 


61.03 


134.55 


1 


9-32 


0.28125 


7.14375 


180 


11.25 


5.103 


54.93 


121.09 


2 


17-64 


0.265625 


6.746875 


170 


10.625 


4.819 


51.88 


114.37 


3 


1-4 


0.25 


6.35 


160 


10. 


4.536 


48.82 


107.64 


4 


15-64 


0.234375 


5.953125 


150 


9.375 


4.252 


45.77 


100.91 


5 


7-32 


0.21875 


5.55625 


140 


8.75 


3.969 


42.72 


94.18 


6 


12-64 


0.203125 


5.159375 


130 


8.125 


3.685 


39.67 


87.45 


7 


3-16 


0.1875 


4.7625 


120 


7.5 


3.402 


36.62 


80.72 


8 


11-64 


0.171875 


4.365625 


110 


6.875 


3.118 


33.57 


74.00 


9 


5-32 


0.15625 


3.96875 


100 


6.25 


2.835 


30.52 


67.27 


10 


9-64 


0.140625 


3.571875 


90 


5.625 


2.552 


27.46 


60.55 


11 


1-8 


0.125 


3.175 


80 


5. 


2.268 


24.41 


53.82 


12 


7-64 


0.109375 


2.778125 


70 


4.375 


1.984 


21.36 


47.09 


13 


3-32 


0.09375 


2.38125 


60 


3.75 


1.701 


18.31 


40.36 


14 


5-64 


0.078125 


1.984375 


50 


3.125 


1.417 


15.26 


33.64 


15 


9-128 


0.0703125 


1.7859375 


45 


2.8125 


1.276 


13.73 


30.27 


16 


1-16 


0.0625 


1.5875 


40 


2.5 


1.134 


12.21 


26.91 


17 


9-160 


0.05625 


1.42875 


36 


2.25 


1.021 


10.99 


24.22 


18 


1-20 


0.05 


1.27 


32 


2. 


0.9072 


9.765 


21.53 


19 


7-160 


0.04375 


1.11125 


28 


1.75 


0.7938 


8.544 


18.84 


20 


3-80 


0.0375 


0.9525 


24 


1.50 


0.6804 


7.324 


16.15 


21 


11-320 


0.034375 


0.873125 


22 


1.375 


0.6237 


6.713 


14.80 


22 


1-32 


0.03125 


0.793750 


20 


1.25 


0.567 


6.103 


13.46 


23 


9-320 


0.028125 


0.714375 


18 


1.125 


0.5103 


5.493 


12.11 


24 


1^0 


0.025 


0.635 


16 


1. 


0.4536 


4.882 


10.76 


25 


7-320 


0.021875 


0.555625 


14 


0.875 


0.3969 


4.272 


9.42 


26 


3-160 


0.01875 


0.47625 


12 


0.75 


0.3402 


3.662 


8.07 


27 


11-640 


0.0171875 


0.4365625 


11 


0.6875 


0.3119 


3.357 


7.40 


28 


1-64 


0.015625 


0.396875 


10 


0.625 


0.2835 


3.052 


6.73 


29 


9-640 


0.0140625 


0.3571875 


9 


0.5625 


0.2551 


2.746 


6.05 


30 


1-80 


0.0125 


0.3175 


8 


0.5 


0.2268 


2.441 


5.38 


31 


7-640 


0.0109375 


0.2778125 


7 


0.4375 


0.1984 


2.136 


4.71 


32 


13-1280 


0.01015625 


0.25796875 


6* 


0.40625 


0.1843 


1.983 


4.37 


33 


3-320 


0.009375 


0.238125 


6 


0.375 


0.1701 


1.831 


4.04 


34 


11-1280 


0.00859375 


0.21828125 


5* 


0.34375 


0.1559 


1.678 


3.70 


35 


5-640 


0.0078125 


0.1984375 


5 


0.3125 


0.1417 


1.526 


3.36 


36 


9-1280 


0.00703125 


0.17859375 


^ 


0.28125 


0.1276 


1.373 


3.03 


37 


17-2560 


0.006640625 


0.168671875 


*i 


0.265625 


0.1205 


1.297 


2.87 


38 


1-160 


0.00625 


0.15875 


4 


0.25 


0.1134 


1.221 


2.69 



1300 FOUNDATIONS AND STRUCTURAL MATERIALS. 

(OHTl\^ IMIIiltV OR STRUTS. 
IXodg-kinson's Formula for C'olnmm, 

P = crushing weight in pounds ; d = exterior diameter in inches ; d x = 
interior diameter in inches ; L = length in feet. 



Kind of Columns. 



Solid cylindrical col- ) 
umns of cast iron . j 

Hollow cylindrical 
columns of cast 



Solid cylindrical col- 
umns of wrought 
iron 

Solid square pillar of i 
Dantzic oak (dry) . j 



Both ends rounded, the 
length of the column 
exceeding 15 times its 
diameter. 



Both ends flat, the 
length of the column 
exceeding 30 times its 
diameter. 



P — 33,380 



P — 29,120 



P = 95,850 



a" 3 - 76 
I? 



P — 98,920 



Pz=. 99,320 



P — 299,600 



tf3-55 

^3-55 (j 3-55 

^3.55 



P — 24,540 — , 



These formulae apply only to cases of breakage caused by bending rather 
than mere crushing. Where the column is short, or say five times its diam- 
eter in length, then the following formula applies. 
Let 

P = value given in preceding formulae, 
K=z transverse section of column in square inches, 
C= ultimate compressive resistance of the material, 
W= crushing strength of the column. 



Then 



W- 



P CK 



P + ICK' 

Hodgkinson's experiments were made upon columns the longest of which 
for cast iron was 60£ inches, and for wrought iron 90f inches. 
The following are some of his conclusions : 

1. In all long pillars of the same dimensions, when the force is applied in 
the direction of the axis, the strength of one which has flat ends is about 
three times as great as one with rounded ends. 

2. The strength of a pillar with one end rounded and the other flat is an 
arithmetical mean between the two given in the preceding case of the same 
dimensions. 

3. The strength of a pillar having both ends firmly fixed is the same as 
one of half the length with both ends rounded. 

4. The strength of a pillar is not increased more than one-seventh by en- 
larging it at the middle. 

Gordon's formulae, deduced from Hodgkinson's experiments, are 
more generally used than Hodgkinson's own. They are : 

Columns with both ends fixed or flat P = — - 



1 + a 



w 



Columns with one end flat, the other end round, P = 



fS 



1 -f 1.8a 



Columns with both ends round or hinged, P = 



fS 



l 2J 



STRENGTH OF MATERIALS. 1301 

S = area of cross section in inches ; 
P =. ultimate resistance of column in pounds ; 
f — crushing strength of the material in pounds per square inch ; 
. . , „ Moment of inertia 

r =. least radius of gyration, in inches, r 2 = -z — : 

J area of section ' 

I z= length of column in inches ; 
a = a coefficient depending upon the material ; 

/ and a are usually taken as constants ; they are really empirical varia- 
bles, dependent upon the dimensions and character of the column as well as 
upon the material. (Burr.) 

For solid wrought-iron columns, values commonly taken are : /r= 36,000 

to40,000 ; « = — ^to^. 

New York City Building Laws 1897-1898 give the following values for/: 

Cast iron f — 80,000 lbs. 

Rolled steel .... /= 48,000 lbs. 

Wrought or rolled iron / = 40,000 lbs. 

American oak . . . /= 6,000 lbs. 

Pitch or Georgia pine . / = 5,000 lbs. 

White pine and spruce /= 3,500 lbs. 

For solid cast-iron columns, f= 80,000, a =. -t™-. 

80 000 
For hollow cast-iron columns, fixed ends, p =z v 2 , / = length and 

1 + 800^ 

d — diameter in the same unit, and p = strength in lbs. per square inch. 

Sir Benjamin Baker gives, 

For mild steel / = 67,000 lbs., a = 7^ ^j- 
For strong steel f= 114,000 lbs., a = . 

STHIXGTH OF MATEKIAIS, 

The terms stress and strain are generally used synonymously, authorities 
differing as to which is the proper use. Merriman defines st7 : ess as a force 
which acts in the interior of a body, and resists the external forces which 
tend to change its shape. A deformation is the amount of change of shape 
of a body caused by the stress. The word strain is often used as synony- 
mous with stress, and sometimes it is also used to designate the deforma- 
tion. Merriman gives the following general laws for simple tension or 
compression, as having been established by experiment. 

a. When a small stress is applied to a body, a small deformation is pro- 
duced, and on the removal of the stress the body springs back to its original 
form. For small stresses, then, materials may be regarded as perfectly 
elastic. 

b. Under small stresses the deformations are approximately proportional 
to the forces or stresses which produce them, and also approximately pro- 
portional to the length of the bar or body. 

c. When the stress is great enough, a deformation is produced which is 
partly permanent; that is, the body does not spring back entirely to its 
original form on removal of the stress. This permanent part is termed a 
set. In such cases the deformations are not proportional to the stress. 

d. When the stress is greater still, the deformation rapidly increases, and 
the body finally ruptures. 

e. A sudden shock or stress is more injurious than a steady stress, or than 
a stress gradually applied. 



1302 FOUNDATIONS AND STRUCTURAL MATERIALS. 

£LA§TIC LIMIT. 

The elastic limit of a material under test for tensile strength is defined as 
the point where the rate of stretch begins to increase, or where the defor- 
mations cease to be proportional to the stresses, and the body loses its 
power to return completely to its former dimensions when the stress is re- 
moved. 

Modulus of Elasticity. 

The modulus or coefficient of elasticity is the term expressing the relation 
of the amount of extension or compression of a material under stress to the 
load producing that stress or deformation. It is the load per unit of section 
divided by the extension per unit of length. 
If P — applied load, 

k = sectional area of piece, 
I = length of the part extended, 
A. r= amount of extension, 
M = modulus of elasticity, 

M- P ' A - Pl 

k * l~ k\ 

Following are the Moduli of elasticity for various materials. 
Brass, cast 9,170,000 

" wire 14,230,000 

Copper 15,000,000 to 18,000,000. 

Lead 1,000,000 

Tin, cast 4,600,000 

Iron, cast 12,000,000 to 27,000,000 (?) 

Iron, wrought 22,000,000 to 29,000,000 

Steel 26,000,000 to 32,000,000 

Marble 25,000,000 

Slate 14,500,000 

Glass 8,000,000 

Ash 1,600,000 

Beech 1,300,000 

Birch 1,250,000 to 1,500,000 

Fir 869,000 to 2,191,000 

Oak 974,000 to 2,283,000 

Teak 2,414,000 

Walnut 306,000 

Pine, long-leaf (butt-logs) . . 1,119,200 to 3,117,000 Average, 1,926,00 

factor of Safety. 

This may be defined as the factor by which the breaking strength of a 
material is divided to obtain a safe working-stress. The factor of safety is 
sometimes a rather indefinite quantity, owing to lack of information as to 
the strength of materials, and it is now becoming common to name a defi- 
nite stress which is substantially the result of dividing the average strengths 
by a factor. 

The following factors are found in the "Laws Relating to Building in 
New York City," 1897-1898. 

For beams, girders, and pieces subject to transverse strains, factor of 
safety = 4. 

For wrought-iron or rolled-steel posts, columns, or other vertical sup- 
ports, 4. 

For other materials subject to a compressive strain, 5. 

For tie-rods, tie-beams, and other pieces subject to tensile strain, 6. 

.no.TiF.vr or i\uiTii. 

The moment of inertia of a body about any axis, is the sum of the products 
of the mass of each particle of the body, into the square of its (least) dis- 
tance from the axis. 



MOMENT OF INERTIA. 1303 

RADIUS Of GTRATIOJ. 

The radius of gyration of a section is the square root of the quotient of 
the moment of inertia, divided by the area of the section, or 



Radius of gyrations / Moment of inertia 
\ Area of section. 

The radius of gyration of a solid about an axis is equal to the 



s 



Moment of Inertia 
Mass of the Solid 



Use in the Formulae for .Strength of Girders and 

Columns. 

The strength of sections to resist strains, either as girders or as 
columns, depends on the form of the section and its area, and the property 
of the section which forms the basis of the constants used in the formula© 
for strength of girders and columns to express the effect of the form, is its 
moment of inertia about its neutral axis. Thus the moment of resistance 
of any section to transverse bending is its moment of inertia divided by the 
distance from the neutral axis to the fibers farthest removed from the axis ; 
or 

,, „ . , Moment of inertia _'_ / 

Moment of resistance = -p-r— t= — ^ ^ -. M = — . 

Distance of extreme fiber from axis e 

Moment of Inertia of Compound Shapes. 

(Pencoyd Iron Works.) 

The moment of inertia of any section about any axis is equal to the I about 
a parallel axis passing through its center of gravity -f- (the area of the sec- 
tion x the square of the distance between the axes). 

By this rule, the moments of inertia or radii of gyration of any single sec- 
tions being known, corresponding values may be obtained for any combina- 
tion of these sections. 

Radius of Ojration of Compound Shapes. 

In the case of a pair of any shape without a web the value of R can always 
be found without considering the moment of inertia. 

The radius of gyration for any section round an axis parallel to another 
axis passing through its center of gravity is found as follows : 

Let r = radius of gyration around axis through center of gravity ; R zzz 
radius of gyration around another axis parallel to above; d =z distance be- 
tween axes : 

R=z V~d?~+r 2 

When r is small, R may be taken as equal to d without material error. 

EIEUTEHTTS OF USUAIj SECTIONS. 

Moments refer to horizontal axis through center of gravity. This table is 
intended for convenient application where extreme accuracy is not impor- 
tant. Some of the terms are only approximate ; those marked * are cor- 
rect. Values for radius of gyration in flanged beams apply to standard 
minimum sections only. 

A = area of section ; 

b — breadth ; 

h =z depth ; 
D =. diameter. 



1304 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Shape of Section. 


Moment of 
Inertia. 


Moment 

of 

Resistance. 


Square of 

Least 
Radius of 
Gyration. 


Least 
Radius of 
Gyration. 




bh** 
12 


bh «* 

6 


/Least\ 2 * 
V Side J 






— 


* 

f 


Solid Rect- 
angle. 


Least side* 




3 46 




12 






-6-- 










* 

i 


Hollow Rect- 
angle. 


bh^—b x h^ * 


bht—bihS* 


/i 2 + Z*! 2 * 


h-\- ht 




12 


6h 


12 


4.89 


* 


-6— . 




f-&-\ 


Solid Circle. 


AD** 
16 


AD* 

8 


D** 

16~ 


D* 

4 


k - D- ->j 


Hollow Circle 
A, area of 

large section ; 
a, area of 

small section. 


AD*— ad* 


AD*— ad* 


D*+d** 
16 


D + d 


16 


8D 


5.64 


y 


A — T 


Solid 
Triangle. 


bW 
36 


bh* 

24 


The least 

of the two: 

h 2 b* 

18 ° r 24 


The least 

of the two : 

h b 


-b— H 


or — 

4.24 4.9 




i 


Even Angle. 


Ah* 
10.2 


Ah 

7.2 


63 

25 


b 
5 




V 


« 


-*~J 






P 


Uneven Angle 


Ah* 
9.5 


Ah 
6.5 


(hb)* 


hb 






13(h*+b*) 


2.6 (h + b) 


HS 


Even Cross. 


Ah* 
19 


Ah 
9.5 


h* 
22.5 


h 
4.74 




1 


,1 


Even Tee. 


4h* 
11.1 


8 


b* 
22^5 


b 


r-^ 


4.74 


L~J»- 


H 




4 


^ 


I-Beam. 


Ah* 
6.66 


Ah 
3.2 


b* 
21 


b 
4.58 




Channel. 


Ah* 
7.34 


3.67 


b* 
12.5 




i 


*— h 


I 


b 
3M 


"1 


te 


Deck Beam. 


Ah* 
6.9 


Ah 
4 


6 2 
36.5 


b 
6 



Distance of base from center of gravity, solid triangle, - ; even angle, 

— — ; uneven angle, — — ; even tee, ~; deck beam, — ; all other shapes 

^, h D 
given in the table, - or ~k * 



ELEMENTS OF USUAL SECTIONS. 



1305 



Solid Cast-iron Columns. 

Table, based on Hodgkinson's formula (gross tons). 

The figures are one-tenth of the breaking weight in tons, for solid col- 
umns, ends flat and fixed. 



.5 

es c> 

£5 






Length of Column 


m Feet. 








6. 


8. 


10. 


12. 


14. 


16. 


18. 


20. 


25. 


H 


.82 


.50 


.34 


.25 


.19 


.15 


.13 


.11 


.07 


ii 


1.43 


.87 


.60 


.44 


.34 


.27 


.22 


.18 


.13 


2 


2.31 


1.41 


.97 


.71 


.55 


.44 


.36 


.30 


.20 


2£ 


3.52 


2.16 


1.48 


1.08 


.83 


.67 


.54 


.46 


.31 


2£ 


5.15 


3.16 


2.16 


1.58 


1.22 


.97 


.80 


.66 


.56 


2| 


7.26 


4.45 


3.05 


2.23 


1.72 


1.37 


1.12 


.94 


.64 


3 


9.93 


6.09 


4.17 


3.06 


2.35 


1.87 


1.53 


1.28 


.88 


3£ 


17.29 


10.60 


7.26 


5.32 


4.10 


3.26 


2.67 


2.23 


1.53 


4 


27.96 


17.15 


11.73 


8.61 


6.62 


5.28 


4.32 


3.61 


2.47 


^ 


42.73 


26.20 


17.93 


13.15 


10.12 


8.07 


6.60 


5.52 


3.78 


5 


62.44 


38.29 


26.20 


19.22 


14.79 


11.79 


9.65 


8.06 


5.52 


5i 


88.00 


53.97 


36.93 


27.09 


20.84 


16.61 


13.60 


11.37 


7.78 


6 


120.4 


73.82 


50.51 


37.05 


28.51 


22.72 


18.60 


15.55 


10.64 


6* 


160.6 


98.47 


67.38 


49.43 


38.03 


30.31 


24.81 


20.74 


14.19 


7 


209.7 


128.6 


87.98 


64.53 


49.66 


39.57 


32.30 


27.08 


18.53 


7£ 


268.8 


164.8 


112.8 


82.73 


63.66 


50.73 


41.53 


34.72 


23.76 


8 


339.1 


207.9 


142.3 


104.4 


80.31 


64.00 


52.39 


43.80 


29.97 


8£ 


421.8 


258.6 


177.0 


129.8 


99.90 


79.61 


65.16 


54.48 


37.28 


9 


518.2 


317.7 


217.4 


159.5 


122.7 


97.80 


80.05 


66.92 


45.80 


9£ 


629.5 


3S6.0 


264.2 


193.8 


149.1 


118.8 


97.25 


81.70 


55.64 


10 


757.2 


464.3 


317.7 


233.1 


179.3 


142.9 


117.0 


97.79 


66.92 


10i 


902.6 


553.5 


378.7 


277.8 


213.8 


170.3 


139.4 


116.6 


79.77 


11 


1067.1 


654.4 


447.8 


328.5 


252.7 


201.4 


164.9 


137.8 


94.31 


n * ! 


1252.3 


767.9 


525.5 


385.4 


296.6 


236.4 


193.5 


161.7 


110.7 


12 ; 


1459.6 


895.1 


612.5 


449.3 


345.7 


275.5 


225.5 


188.5 


129.0 



sc 



Where the length is less than 30 diameters, 

Strength in tons of short columns =r - 7ri 

10o -f- 5(7 

S being the strength given in the above table, and C= 49 times the sec- 
tional area of the metal in inches. 

Hollow Columns. 

The strength nearly equals the difference between that of two solid col- 
umns, the diameters of which are equal to the external and internal diam- 
eters of the hollow one. 

More recent experiments carried out by the Building Department of New 
York City on full-size cast-iron columns, and other tests made at the 
Watertown Arsenal on cast-iron mill columns, show Gordon's formula, 
based on Hodgkinson's experiments, to give altogether too high results. 

The following table, from results of the New York Building Department 
tests, as published in the Engineering News, January 13-20, 1898, show actual 
results on columns such as are constantly used in buildings. Applying 
Gordon's formula to the same columns gives the following as the breaking 
load per square inch. For 15-inch columns, 57,000 lbs.; for 8-inch and 6-inch 
columns, 40,000 lbs., all of which are much too high, as shown by the table. 

Prof. Lanza gives the average of 11 columns in the Watertown tests as 
29,600 pounds per square inch, and recommends that 5,000 pounds per square 
inch be used as the maximum safe load for crushing strength. 



1306 FOUNDATIONS AND STRUCTURAL MATERIALS. 





Tests of 


Cast-iron Columns. 










Thickness. 


Breaking Load. 




Diam. 
Inches. 


























Max. 


Min. 


Average. 


Pounds. 


Pounds 
per sq. in. 


1 


15 




1 


1 


1,356,000 


30,830 


2 


15 


li B * 


1 


H 


1,330,000 


27,700 


3 


15 


11 


1 


11 


1,198,000 


24,900 


4 


15| 


1 7 


1 


1,246,000 


25,200 


5 


15 


1H 

1 T5 


1 


m 


1,632,000 


32,100 


6 


15 


1 1 

if 


n 


1t 3 6 


2,082,000+ 


40,400+ 


7 


7| to 8J 


§ 


1 


651,00 


31,900 


8 


8 


i& 


i 


If 3 * 


612,800 


26,800 


9 


6& 


1* 


n 


1& 


400,000 


22,700 


10 


6 5 3 2 


It 1 * 


1& 


455,200 


26,300 



Ultimate Strength of Hollow. Cylindrical Wrought and 
Cast-iron Columns, when fixed at the Ends. 

(Pottsville Iron and Steel Co.) 

Computed by Gordon's formula, p — - 



1+Ci 



(J)" 



p =r Ultimate strength in lbs. per square inch ; 
I = Length of column, ) ^ rt+1% • Bt%mr% „ ni4 . . 
h = Diameter of column, } both m same umts i 
_ I 40,000 lbs. for wrought iron; ) 
80,000 lbs. for cast iron; j 

C — 1/3000 for wrought iron, and 1/800 for cast iron. 

„ 80.000 

For cast iron, p : 



/ 



1+ 800 V h) 



For wrought iron, p = - 



40,000 



l+— (-Y 

^ 3,000 V hj 
If ollow Cylindrical Columns. 



Ratio of 


Maximum Load per sq. in. 


Safe Load per Square Inch. 


Length to 










Diameter. 










1 
h 


Cast Iron. 


Wrought Iron. 


Cast Iron, 
Factor of 6. 


Wrought Iron, 
Factor of 4. 


8 


74075 


39164 


12346 


9791 


10 


71110 


38710 


11851 


9677 


12 


67796 


38168 


11299 


9542 


14 


64256 


37546 


10709 


9386 


16 


60606 


36854 


10101 


9213 


18 


56938 


36100 


9489 


9025 


20 


53332 


35294 


8889 


8823 


22 


49845 


34442 


8307 


8610 


24 


46510 


33556 


7751 


8389 


26 


43360 


32642 


7226 


8161 


28 


40404 


31712 


6734 


7928 


30 


37646 


30768 


6274 


7692 



ELEMENTS OF USUAL SECTIONS. 



1307 



Hollow Cylindrical Columns. — Continued. 



Ratio of 
Length to 


Maximum Load per Sq. In. 


Safe Load per Square Inch. 


Diameter. 
1 
h 


Cast Iron. 


Wrought Iron. 


Cast Iron, 
Factor of 6. 


Wrought Iron, 
Factor of 4. 


32 


35088 


29820 


5848 


7455 


34 


32718 


28874 


5453 


7218 


36 


30584 


27932 


5097 


6983 


38 


28520 


27002 


4753 


6750 


40 


26666 


26086 


4444 


6522 


42 


24962 


25188 


4160 


6297 


44 


23396 


24310 


3899 


6077 


46 


21946 


23454 


3658 


5863 


48 


20618 


22620 


3436 


5655 


50 


19392 


21818 


3262 


5454 


52 


18282 


21036 


3047 


5259 


54 


17222 


20284 


2870 


5071 


56 


16260 


19556 


2710 


4889 


58 


15368 


18856 


2561 


4714 


60 


14544 


18180 


2424 


4545 



Ultimate Strength of Wrous-ht-iron Columns. 

p = ultimate strength per square inch; 

Z= length of column in inches; 

r = least radius of gyration in inches. 

40000 
For square end-bearings, p = - 



For one pin and one square bearing, p = - 



^40000Vr/ 
40000 



1 + 



000\rj 



For two pin bearings, 



30000 
40000 



— 1+ i fi\' 

^20000 \r) 
For safe working-load on these columns use a factor of 4 when used in 
buildings, or when subjected to dead load only; but when used in bridges 
the factor should be 5. 

Wr ought-Iron Columns. 





Ultimate Strength 


in Lbs. 




Safe Strength in 


Lbs. per 


1 


per Square Inch. 


I 
r 


Square Inch — Factor of 5. 


r 


Square 


Pin and 


Pin 


Square 


Pin and 


Pin 




Ends. 
39944 


Sq. End. 


Ends. 




Ends. 


Sq.End. 


Ends. 


10 


39866 


39800 


10 


7989 


7973 


7960 


15 


39776 


39702 


39554 


15 


7955 


7940 


7911 


20 


39604 


39472 


39214 


20 


7921 


7894 


7843 


25 


39384 


39182 


38788 


25 


7877 


7836 


7758 


30 


39118 


38834 


38278 


30 


7821 


7767 


7656 


35 


38810 


38430 


37690 


35 


7762 


7686 


7538 


40 


38460 


37974 


37036 


40 


7692 


7595 


7407 


45 


38072 


37470 


36322 


45 


7614 


7494 


7264 


50 


37646 


36928 


35525 


50 


7529 


7386 


7105 


55 


37186 


36336 


34744 


55 


7437 


7267 


6949 


60 


36697 


35714 


33898 


60 


7339 


7148 


6780 


65 


36182 


34478 


33024 


65 


7236 


6896 


6605 


70 


35634 


34384 


32128 


70 


7127 


6877 


6426 


75 


35076 


33682 


31218 


75 


7015 


6736 


6244 


80 


34482 


32966 


30288 


80 


6896 


6593 


6058 


85 


33883 


32236 


29384 


85 


6777 


6447 


5877 


90 


33264 


31496 


28470 


90 


6653 


6299 


5694 


95 


32636 


30750 


27562 


95 


6527 


6150 


5512 


100 


32000 


30U00 


26666 


100 


6400 


6000 


5333 


105 


31357 


29250 


25786 


105 


6271 


5850 


5157 



1308 FOUNDATIONS AND STRUCTURAL MATERIALS. 

TRA^S¥£R§E STBEIGTH. 

Transverse strength of bars of rectangular section is found to vary di- 
rectly as the breadth of the specimen tested, as the square of its depth, and 
inversely as its length. The deflection under load varies as the cube of the 
length, and inversely as the breadth and as the cube of the depth. Alge- 
braically, if S := the strength and D the deflection, I the length, b the 
breadth, and d the depth, 

S varies as -7- and D varies as =-=5. 
I bd 3 

To reduce the strength of pieces of various sizes to a common standard, 
the term modulus of rupture (B) is used. Its value is obtained by experi- 
ment on a bar of rectangular section supported at the ends and loaded in 
the middle, and substituting numerical values in the following formula : 

A - 2 bd* 
in which P = the breaking load in pounds, I = the length in inches, b the 
breadth, and d the depth. 

fundamental Formula* for flexure of Beams. 

(Merriman.) 

Resisting shear *± vertical shear ; 

Resisting moment = bending moment ; 

Sum of tensile stresses = sum of compressive stresses ; 

Resisting shear = algebraic sum of all the vertical components of the in- 
ternal stresses at any section of the beam. 

If A be the area of the section and S% the shearing unit stress, then resist- 
ing shear = ASs ; and if the vertical shear = V, then V=. ASa. 

The vertical shear is the algebraic sum of all the external vertical forces 
on one side of the section considered. It is equal to the reaction of one sup- 
port, considered as a force acting upward, minus the sum of all the vertical 
downward forces acting between the support and the section. 

The resisting moment =, algebraic sum of all the moments of the inter- 
nal horizontal stresses at any section with reference to a point in that sec- 
ts'/ 
tion, = — , in which S= the horizontal unit stress, tensile or compressive 

as the case may be, upon the fiber most remote from the neutral axis, c = 
the shortest distance from that fiber to said axis, and I— the moment of 
inertia of the cross-section with reference to that axis. 

The bending moment Mis the algebraic sum of the moment of the external 
forces on one side of the section with reference to a point in that section = 
moment of the reaction of one support minus sum of moments of loads be- 
tween the support and the section considered. 

M= — . 

c 

The bending moment is a compound quantity = product of a force by the 
distance of its point of application from the section considered, the distance 
being measured on a line drawn from the section perpendicular to the direc- 
tion of the action of the force. 

Concerning the above formula, Prof. Merriman, Eng. News, July 21, 1894, 
says : The formula just quoted is true when the unit-stress S on the part of 
the beam farthest from the neutral axis is within the elastic limit of the 
material. It is not true when this limit is exceeded, because then the neutral 
axis does not pass through the center of gravity of the cross section, and 
because also the different longitudinal stresses are not proportional to their 
distances from that axis, these two requirements being involved in the de- 
duction of the formula. But in all cases of design the permissible unit- 
stresses should not exceed the elastic limit, and hence the formula applies 
rationally, without regarding the ultimate strength of the material or any 
of the circumstances regarding rupture. Indeed, so great reliance is placed 
upon this formula that the practice of testing beams by rupture has been 
almost entirely abandoned, and the allowable unit-stresses are mainly de- 
rived from tensile and compressive tests, 



TRANSVERSE STRENGTH. 



1309 



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1310 FOUNDATIONS AND STRUCTURAL MATERIALS. 

formulae for Transverse Strength of Beams, 

(Referring to table on preceding page.) 

P = load at middle ; 
W = total load, distributed uniformly ; 
I = length ; b = breadth ; d — depth, in inches ; 
E z=z modulus of elasticity ; 

R = modulus of rupture, or stress per square inch of extreme fiber ; 
/ = moment of inertia ; 

c = distance between neutral axis and extreme fiber. 
For breaking-load of circular section, replace bd 2 by 0.59c? 3 . 
For good wrought iron the value of R is about 80,000, for steel about 
120,000, the percentage of carbon apparently having no influence. (Thurs- 
ton, " Iron and Steel," p. 491.) 

For cast iron the value of R varies greatly according to quality. Thurston 
found 45,740 and 67,980 in No. 2 and No. 4 cast iron, respectively. 

For beams fixed at both ends and loaded in the middle, Barlow, by experi- 
ment, found the maximum moment of stress = ^Pl instead of %Pl, the re- 
sult given by theory . Prof. Wood (' ' Resistance Materials," p. 155) says of this 
case, " The phenomena are of too complex a character to admit of a thorough 
and exact analysis, and it is probably safer to accept the results of Mr. Bar- 
low in practice than to depend upon theoretical results." 

APPROXIMATE GREATEST SAFE LOAD KN 
IBS. OA STEEL BEAMS. 

(Pencoyd Iron Works.) 

Based on fiber strains of 16,800 lbs. for steel. (For iron the loads should be 
one-sixth less, corresponding to a fiber strain of 14,000 lbs. per square inch.) 

L = length in feet between supports ; 
A = sectional area of beam in square inches ; 
D =r depth of beam in inches ; 
a = interior area in square inches ; 
d = interior depth in inches ; 
w = working-load in net tons. 



Shape 


Greatest Safe Load in Lbs. 


Deflection in Inches. 


of 
Section. 


Load in 
Middle. 


Load 
Distributed. 


Load in 
Middle. 


Load 
Distributed. 


Solid 
Rectangle. 


940AD 
L 


1880^D 
L 


wLP 
32 AD 2 


52AD 2 


Hollow 


940 (AD — ad) 
L 


lm(AD-ad) 
L 


wV> 


wL* 


Rectangle. 


32(AD 2 —ad 2 ) 


52(AD 2 —ad 2 ) 


Solid 
Cylinder. 


700AD 
L 


14MAD 
L 


2AAD 2 


38AD 2 


Hollow 


700 (AD — ad) 
L 


l4O0(AD—ad) 
L 


wL z 


wL* 


Cylinder. 


24(AD 2 —ad 2 ) 


38(AD 2 —ad 2 ) 



APPROXIMATE GREATEST SAFE LOAD IN LBS. 1311 



Shape 


Greatest Safe Load in Lbs. 


Deflection in Inches. 


of 
Section. 


Load in 
Middle. 


Load 
Distributed. 


Load 
in Middle. 


Load 
Distributed. 


Even- 
legged 
Angle or 
Tee. 


930 AD 
L 


1860 A D 
L 




wL 3 
VIAD* 


Channel or 
ZBar. 


160CL4Z) 
L 


3200JZ) 
L 


53AD 2 


wL 3 
85AD 2 


Deck 
Beam. 


UfyOAD 
L 


2900.4/) 
L 


wL 5 
50AD* 


wL 3 
WAD* 


I-Beam. 


17S0AD 
L 


ZoWAD 
L 


wL 3 
58AB 2 


wL 3 
93^Z) 2 


I 


II 


III 


IV 


V 



The rules for rectangular and circular sections are correct, while those for 
the flanged sections are approximate, and limited in their application to the 
standard shapes as given in the Pencoyd tables. 

The calculated safe loads will be approximately one-half of loads that 
would injure the elasticity of the materials. 

The rules for deflection apply to any load below the elastic limit, or less 
than double the greatest safe load by the rules. 

If the beams are long, without lateral support, reduce the loads for the 
ratios of width to span as follows : 



Length of Beam. 



Proportion of Calculated Load 
forming Greatest Safe Load. 



20 times flange width. 

30 

40 

50 

60 

70 



Whole calculated load. 

9-10 " " 

8-10 " " 

7-10 

6-10 " " 

5-10 " 



These rules apply to beams supported at each end. For beams supported 
otherwise, alter the coefficients of the table as described below, referring to 
the respective columns indicated by number. 

Changes of Coefficients for Special Form* of Beams. 



Kind of Beam. 



Fixed at one end, loaded 
at the other. 



Coefficient for Safe 
Load. 



One-fourth of the coeffi- 
cient of col. II. 



Coefficient for Deflec- 
tion. 



One-sixteenth of the co- 
efficient of col. IV. 



1312 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Changes of Coefficients — Continued. 



Kind of Beam. 


Coefficient for Safe 
Load. 


Coefficient of Deflec- 
tion. 


Fixed at one end, load 
evenly distributed. 


One-fourth of the coeffi- 
cient of col. III. 


Five forty-eighths of the 
coefficient of col. V. 


Both ends rigidly fixed, 
or a continuous beam, 
with a load in middle. 


Twice the coefficient of 
col. II. 


Four times the coeffi- 
cient of col. IV. 


Both ends rigidly fixed, 
or a continuous beam, 
with load evenly dis- 
tributed. 


One and a half times 
the coefficient of col. 
III. 


Five times the coeffi- 
cient of col. V. 



Let 



modulus of Elasticity and Elastic Resilience. 

P — tensile stress in pounds per square inch at the elastic limit ; 
e — elongation per unit of length at the elastic unit ; 
E = modulus of elasticity = P -f- e ; e = P -=- E. j p2 



Then elasticity resilience per cubic inch = \Pe = 



2 E' 






BEAMS OF MIFORM §TR£^OTH THROUGHOUT 
THEIR LENGTH. 

The section is supposed in all cases to be rectangular throughout. The 
beams shown in plan are of uniform depth throughout. Those shown in 
elevation are of uniform breadth throughout. 

B = breadth of beam. D = depth of beam. 

Fixed at one end, loaded at the other ; 
curve parabola, vertex at loaded end ; BD 2 
p proportional to distance from loaded end. 
% The beam may be reversed so that the up- 
per edge is parabolic, or both edges may be 
parabolic. 

Fixed at one end, loaded at the other ; tri- 
angle, apex at loaded end ; BD 2 proportional 
to the distance from the loaded end. 

Fixed at one end ; load distributed ; tri- 
S angle, apex at unsupported end ; BD 2 pro- 
p portional to square of distance from unsup- 
0, ported end. 

Fixed at one end ; load distributed ; curves 
two parabolas, vertices touching each other, 
at unsupported end ; BI) 2 proportional to dis- 
tance from unsupported end. 

Supported at both ends ; load at any one 
point ; two parabolas, vertices at the points 
of support, bases at point loaded ; BD 2 pro- 
portional to distance from nearest point of 
support. The upper edge or both edges may 
also be parabolic. 

Supported at both ends ; load at anv one 
point ; two triangles, apices at points of sup- 
port, bases at point loaded ; BD 2 propor- 
tional to distance from the nearest point of 
support. 

Supported at both ends ; load distributed ; 
curves two parabolas, vertices at the middle 
of the beam ; bases center line of beam ; BI) 2 
proportional to product of distances from 
points of support. 

Supported at both ends ; load distributed ; 
_ curve semi-ellipge ; BD 2 proportional to the 
\ product of the distances from the points of 
support. 





TRENTON BEAMS AND CHANNELS. 



1313 



TRENTON BE4WS AND (HlWELIi. 

(Trenton Iron Works.) 
v 

To find which beam, supported at both ends, will be required to support 
with safety a given uniformly distributed load : 

Multiply the load in pounds by the span in feet, and take the beam whose 
" Coefficient for Strength " is nearest to and exceeds the number so found. 
The weight of the beam itself should be included in the load. 

The deflection in inches for such distributed load will be found by divid- 
ing the square of the span taken in feet, by seventy (70) times the depth of 
the beam taken in inches for iron beams, and by 52.5 times the depth for 
steel. 

Example. — Which beam will be required to support a uniformly distrib- 
uted load of 12 tons (= 24,000 lbs.) on a span of 15 feet ? 

24,000 X 15= 360,000, which is less than the coefficient of the 12£-mch 125- 
lb. iron beam. The weight of the beam itself would be 625 lbs., which, 
added to the load and multiplied by the span, would still give a product less 
than the coefficient; thus, 



24,625 X 15=369,375. 



The deflection will be : 



15 x 15 
70 X 12£ 



S 



c= 0.26 inch. 



The safe distributed load for each beam can be found by dividing the 
coefficient by the span in feet, and subtracting the weight of the beam. 

When the load is concentrated entirely at the center of the span, one-half 
of this amount must be taken. 

The beams must be secured against yielding sideways, or the safe loads will 
be much less. 

Tit EX TO X ROILED S1EEL BEAMS. 





Weight 


per 


Width of 

Flanges in 

Inches. 




Coefficient for 


Designation of 
Beam. 


Yard in 


Lbs. 


Thickness 
of Stem. 


Strength i n 
Lbs., Minimum 




Min. 


Max. 




Weight. 


15 inch 


150 


190 


5.75 


.45 


753,000 


15 ' 














123 


160 


5.5 


.40 


603,000 


12 ■ 














120 


150 


5.5 


.39 


500,000 


12 « 














96 


125 


5.25 


.32 


407,000 


10 • 














135 


160 


5.25 


.45 


461,000 


10 « 














99 


125 


5.0 


.37 


344,000 


10 ' 














76 


100 


4.75 


.32 


264,000 


9 ' 














81 


105 


4.75 


.31 


262,000 


9 4 














63 


85 


4.5 


.27- 


200,000 


8 ' 














66 


85 


4.5 


.27 


192,000 


8 « 














54 


75 


4.25 


.25 


154,000 


7 4 














60 


80 


4.25 


.27 


151,000 


7 ' 














46.5 


65 


4.0 


.23 


118,000 


6 ' 














50 


65 


3.5 


.30 


104,000 


6 ' 














40 


55 


3.0 


.25 


83,300 


5 ' 














39 


52 


3.13 


.26 


67,000 


5 ' 














30 


42 


3.0 


.22 


52,900 


4 ■ 














30 


40 


2.75 


.24 


41,200 


4 l 














22.5 


32 


2.62 


.20 


31,400 


2 ' 














*i 




.75 


i 


2,660 


U " 


5i 




1.50 


s 


2,300 



1314 FOUNDATIONS AND STRUCTURAL MATERIALS. 



THE\TO\ IROI BEAMS A YI> CHi^YELS. 



bo 

H 




O.J3 . 

to 

_ <D <D 

§§£ 


CO o 

5* 


Coefficient 
in Lbs. for 
Transverse 
Strength. 


p 

£ 

bf 

M 


"<pT3 

03 

«3 u 2 


H ? to 


QQ 

2^ . 

A 0> CC 

M^ <P 


Coefficient 
in Lbs. for 
Transverse 
Strength. 


I-B earns*. 


Channels. 


20 


272 


6! 


ll 
TS 


1,320,000 


15 


190 


4| 


1 


625,000 


20 


200 


6 


1 


990,000 


15 


120 


4 


* 


401,000 


15£ 


200 


5f 


.6 


748,000 


m 


140 


4 


B 


381,000 


15 T 3 B 


150 


5 


* 


551,000 


12i 


70 


3 


.33 


200,100 


15| 


125 


5 


.42 


460,000 


io| 


60 


23 


1 


134,750 


12ft 


170 


5h 


.6 


511,000 


10 


48 


2* 


ft 


102,000 


12* 


125 


4.8 


.47 


377,000 


9 


70 


3| 


ft 


146,000 


12 


120 


5* 


.39 


375,000 


9 


50 


2* 


.33 


104,000 


12 


96 


5J 


.32 


306,000 


8 


45 


2£ 


.26 


88,950 


10* 


135 


5 


.47 


360,000 


8 


33 


2.2 


.20 


65,800 


10* 


105 


4* 


1 


286,000 


7 


36 


2* 


J 


62,000 


10* 


90 


4* 


i 6 S 


250,000 


7 


25£ 


2 


.20 


39,500 


9 


125 


4£ 


.57 


268,000 


6 


45 


a* 


.40 


58,300 


9 


85 


4* 


3 

8 


199,000 


6 


33 


2| 


.28 


45,700 


9 


70 


4 


.3 


167,000 


6 


22* 


11 


.18 


33,680 


8 


80 


*i 


3 

6 


168,000 


5 


19 


If 


.20 


22,800 


8 


65 


4 


.3 


135,000 


4 


161 


H 


.20 


15,700 


7 


55 
120 
90 
50 
40 
40 
30 


3| 
5i 
5 
3J 

3 
3 
2f 


.3 
f 
h 
.3 
\ 

i 


101,000 
172,000 
132,000 
76,800 
62,600 
49,100 
38,700 


3 


15 


H 


.20 


10,500 


6 
6 


Deck Beams. 


6 
6 
5 


8 

7 


65 
55 


4* 

4* 


1 
ft 


91,800 
63,500 


5 






Strut 


Bars. 




4 


37 


3 


i 6 8 


36,800 






















4 


30 


2| 


i 


30,100 


5 


22 


1& 


ft 


11,900 


4 


18 


2 


3 

T8 


18,000 


5 


16 


1ft 


i 


9,100 



TRENTON BEAMS AND CHANNELS. 



1315 



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1316 FOUNDATIONS AND STRUCTURAL MATERIALS. 






3 

o 






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T* <<* CO 

o o o 



bo 

§ oo Ml 

l Km 
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oj © ce 



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Ph 



WOOD. 
Tests of American Woods. 



1317 



In all cases a large number of tests were made of each wood. Minimum 
and maximum results only are given. All of the test specimens had a sec- 
tional area of 1.575 x 1.575 inches. The transverse test specimens were 
39.37 inches between supports, and the compressive test specimens were 

3 PI 
12.60 inches long. Modulus of rupture calculated from formula R = - t-^-\ 

P = load in pounds at the middle, I = length in inches, b =z breadth, 
d = depth : 



Name of Wood. 



Transverse 


Compression 


Tests, 


Parallel to 


Modulus of 


Grain, 


pounds 


Rupture. 


per sq. in. 


Min. 


Max. 


Min. 


Max. 


7440 


12050 


4560 


7410 


6560 


11756 


4150 


5790 


6720 


11530 


3810 


6480 


9680 


20130 


7460 


9940 


8610 


13450 


6010 


7500 


12200 


21730 


8330 


11940 


8310 


16800 


5830 


9120 


7470 


11130 


5630 


7620 


10190 


14560 


6250 


9400 


9830 


14300 


6240 


7480 


18500 


10290 


6650 


8080 


5950 


15800 


4520 


8830 


5180 


10150 


4050 


5970 


10220 


13952 


6980 


8790 


8250 


15070 


4960 


8040 


6720 


11360 


4960 


7340 


4700 


11740 


5480 


6810 


8400 


16320 


6940 


8850 


14870 


20710 


7650 


10280 


11560 


19430 


7460 


8470 


7010 


18360 


5810 


9070 


9760 


18370 


4960 


8970 


7900 


18420 


4540 


8550 


5950 


12870 


3680 


6650 


13850 


18840 


5770 


7840 


11710 


17610 


5770 


8590 


8390 


13430 


3790 


6510 


6310 


9530 


2660 


5810 


5640 


15100 


4400 


7040 


9530 


10030 


5060 


7140 


5610 


11530 


3750 


5600 


3780 


10980 


2580 


4680 


9220 


21060 


4010 


10600 


9900 


11650 


4150 


5300 


7590 


14680 


4500 


7420 


8220 


17920 


4880 


9800 


10080 


16770 


6810 


10700 



% Cucumber tree 

Yellow poplar, white wood . . 
White wood, Basswood . . . 
Sugar maple, Rock maple . . 

Red maple 

Locust 

Wild cherry 

Sweet gum 

Dogwood 

Sour gum, pepperidge .... 

Persimmon 

White ash 

Sassafras 

Slippery elm 

White elm ........ 

Sycamore, Buttonwood . . . 
Butternut, white walnut . . . 

Black walnut 

Shellbark hickory 

Pignut 

White oak 

Red oak 

Black oak 

Chestnut 

Beech 

Canoe birch, paper birch . . . 

Cottonwood 

White cedar 

Red cedar 

Cypress 

White pine 

Spruce pine 

Long-leaved pine, Southern pine 

White spruce 

Hemlock 

Red fir, yellow fir 

Tamarack 



1318 FOUNDATIONS AND STRUCTURAL MATERIALS. 



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wood. 1319 



Rule. — To find the safe uniformly distributed load in tons for white pine 
or spruce beams, multiply the number given in the above table by the thick- 
ness of the beam in inches. For beams of other wood, multiply also by the 
following numbers : 

White Oak. Hemlock. White Cedar. Yellow Pine. Chestnut. 
1.45 .99 .60 1.50 1.08 

Formulae for White Pine Beams. 

Subject to vibration from live loads. 

w = safe load in pounds, less weight of beam. 
I = length of beam in inches. 
d = depth of beam in inches. 
b = breadth of beam in inches. 
For a beam fixed at one end and loaded at the other: 

1000 6d 2 

w =— a— 

For a beam fixed at one end and uniformly loaded : 

1000 bd* 

For a beam supported at both ends and loaded at the middle : 

2000 bd* 

For a beam supported at both ends and uniformly loaded : 

4000 bd 2 
W =—3l- 

Note. — In placing very heavy loads upon short, but deep and strong 
beams, care should be taken that the beams rest for a sufficient distance on 
their supports to prevent all danger from crushing or shearing at the ends. 
Ordinary timbers crush under 6,000 lbs. per square inch. To assure a safety 
of beam against crushing at the end, divide half of the load by 1000 ; the 
quotient will be the least number of square inches of base that should be 
allowed for each end to rest on. 

Table of Safe Load for moderately Seasoned White Pine 
Struts or Pillars. 

The following table, exhibiting the approximate strength of white pine 
struts or pillars, with flat ends, is outlined and interpolated from the rule 
of Rondolet, that the safe load upon a cube of the material being regarded 
as unity, the safe load upon a post whose height is, 

12 times the side will be f 



36 

48 
60 

72 



ft 



700 pounds per square inch is assumed as the safe load upon a cube of 
white pine. 

The strength of each strut is considered with reference to the first-named 
dimension of its cross section, so that if the second dimension is less than 
the first, the strut must be supported in that direction, to fulfill the condi- 
tions of the computation. 

The strength of pillars, as well as of beams of timber, depends much on 
their degree of seasoning. Hodgkinson found that perfectly seasoned blocks 
2 diameters long, required in many cases twice as great a load to crush 
them as when only moderately dry. This should be borne in mind when 
building with green timber. 



1320 FOUNDATIONS AND STRUCTURAL MATERIALS. 



I. Safe Distributed Load§ upon Southern Pine Ream* 
One Inch in Width. 

(C. J. H. Woodbury.) 
(If the load is concentrated at the center of the span, the beams will sus- 
tain half the amount as given in the table.) 



9 




Depth of Beam in 


Inches. 






& 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


15 


16 


1 
0Q 


Load in Pounds per Foot of Span. 


5 


38 


86 


154 


240 


346 


470 


614 


778 


960 














6 


27 


60 


107 


167 


240 


327 


427 


540 


667 


807 












7 


20 


44 


78 


122 


176 


240 


314 


397 


490 


593 


705 


828 








8 


15 


34 


60 


94 


135 


184 


240 


304 


375 


454 


540 


634 


735 






9 




27 


47 


74 


107 


145 


190 


240 


296 


359 


427 


501 


581 


667 


759 


10 




22 


38 


60 


86 


118 


154 


194 


240 


290 


346 


406 


470 


540 


614 


11 






32 


50 


71 


97 


127 


161 


198 


240 


286 


335 


389 


446 


508 


12 






27 


42 


60 


82 


107 


135 


167 


202 


240 


282 


327 


375 


474 


13 








36 


51 


70 


90 


115 


142 


172 


205 


240 


278 


320 


364 


14 








31 


44 


60 


78 


99 


123 


148 


176 


207 


240 


276 


314 


15 








27 


38 


52 


68 


86 


107 


129 


154 


180 


209 


240 


273 


16 










34 


46 


60 


76 


94 


113 


135 


158 


184 


211 


240 


17 










30 


41 


53 


67 


83 


101 


120 


140 


163 


187 


217 


18 












36 


47 


60 


74 


90 


107 


125 


145 


167 


190 


19 














43 


54 


66 


80 


96 


112 


130 


150 


170 


20 














38 


49 


60 


73 


86 


101 


118 


135 


154 


21 
















44 


54 


66 


78 


92 


107 


122 


139 


22 


















50 


60 


71 


84 


97 


112 


127 


23 


















45 


55 


65 


77 


89 


102 


116 


24 




















50 


60 


70 


82 


94 


107 


25 




















46 


55 


65 


75 


86 


98 



Distributed Loads upon Southern Pine Beams Suf- 
ficient to Produce Standard Limit of Deflection. 

(C. J. H. Woodbury.) 



*3 

4> 


Depth of Beam in Inches. 




o . 


a 


2 


3 


4 


5 


6 7 


8 


9 


10 


11 


12 


13 


14 


15 


16 


v3 OQ 


in 


Load in Pounds per Foot of Span. 


®5 


5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 


3 

2 


10 

7 
5 
4 


23 
16 
12 
9 

7 
6 


44 
31 
23 
17 
14 
11 
9 


77 
53 
39 
30 
24 
19 
16 
13 
11 

1 .'•' 


122 
85 
62 
48 
38 
30 
25 
21 
18 
16 
14 


182 
126 
93 
71 
56 
46 
38 
32 
27 
23 
20 
18 
16 


259 

180 

132 

101 

80 

65 

54 

45 

38 

33 

29 

25 

22 

20 

18 


247 
181 
139 
110 
89 
73 
62 
53 
45 
40 
35 
31 
27 
25 
22 
20 


241 

185 
146 
118 
98 
82 
70 
60 
53 
46 
41 
37 
33 
30 
27 
24 
22 


240 

190 

154 

127 

107 

91 

78 

68 

60 

53 

47 

43 

38 

35 

32 

29 

27 

25 


305 

241 

195 

161 

136 

116 

100 

87 

76 

68 

60 

54 

49 

44 

40 

37 

34 

31 


301 

244 

202 

169 

144 

124 

108 

95 

84 

75 

68 

61 

55 

50 

46 

42 

| 39 


300 

248 

208 

178 

153 

133 

117 

104 

93 

83 

75 

68 

62 

57 

52 

48 


301 

253 

215 

186 

162 

147 

126 

112 

101 

91 

83 

75 

69 

63 

58 


.0300 
.0432 
.0588 
.0768 
.0972 
.1200 
.1452 
.1728 
.2028 
.2352 
.2700 
.3072 
.3468 
.3888 
.4332 
.4800 
.5292 
.5808 
.6348 
.6912 
.7500 



MASONRY. 



1321 



UfASOtflOf. 



Brick-Work. 



Brick work is generally measured by 1000 bricks laid in the wall. In con- 
sequence of variations in size of bricks, no rule for volume of laid brick can 
be exact. The following scale is, however, a fair average. 



7 common bricks to a super 
14 
21 

28 " " " 

35 



ft. 4-inch wall. 

9-inch " 

13-inch " 

18-inch " 

22-inch " 



Corners are not measured twice, as in stone-work. Openings over 2 feet 
square are deducted. Arches are counted from the spring. Fancy work 
counted 1£ bricks for 1. Pillars are measured on their face only. 

One thousand bricks, closely stacked, occupy about 56 cubic feet. 

One thousand old bricks, cleaned and loosely stacked, occupy about 72 cu- 
bic feet. 

One cubic foot of foundation, with one-fourth inch joints, contains 21 
bricks. In some localities 24 bricks are counted as equal to a cubic foot. 

One superficial foot of gauged arches requires 10 bricks. 

Stock bricks commonly measure 8| inches by 4± inches by 2| inches, and 
weigh from 5 to 6 lbs. each. 

Paving bricks should measure 9 inches by 4A- inches by If inches, and 
weigh about 4^ lbs. each. 

One yard of paving requires 36 stock bricks, of above dimensions, laid flat, 
or 52 on edge; and 35 paving bricks, laid flat, or 82 on edge. 

The following table gives the usual dimensions of the bricks of some of 
the principal makers. 



Description. 


Inches. 


Description. 


Inches. 


Baltimore front . 
Philadelphia front 
Wilmington front 
Trenton front 
Croton .... 
Colabaugh . . . 


j, 8i X 4| X 2f 

8£ X 4 X 2i 
8J X 3f X 2f 


Maine .... 
Milwaukee . . 
North River . 
Trenton . . . 

Ordinary . . . 


n X 3f X 2f 
8} X 4J X 2| 
8 X 3* X 2i 
8 X 4 X 2\ 
f 7f X 3f X 2i 
(8 X4ix 2J 



Fire Brick - 



J Valentine's (Woodbridge, N. J.) . . $ 
( Downing's (Allentown, Pa.) .... 9 



X 4| X 2£ inches 
X 4| X 2A- inches 



To compute the number of bricks in a square foot of wall. — To the face 
dimensions of the bricks used, add the thickness of one joint of mortar, and 
multiply these together to obtain the area. Divide 144 square inches by 
this area, and multiply by the number of times which the dimension of the 
brick, at right angles to its face, is contained in the thickness of the wall. 



Example. — How many Trenton bricks in a square foot of 12-inch wall, 
the joints being \ inch thick ? 

8~+T x 2\-\-\ — 20.62 ; 144 -f 20.62 = 7 ; 7 X 3 — 21 bricks per square ft. 



1322 FOUNDATIONS AND STRUCTURAL MATERIALS. 



Weight and Bulk of Bricks. 









Number of Bricks, 










by itself. 


in wall with cement. 


Gross 












Tons. 


Pounds. 


Cu. ft. 


C. Brick. 


F. Brick. 


C. Brick. 


F. Brick. 


1 


2240 


22.4 


448 


416.6 


381 


347 


0.04464 


100 


1 


20 


18.6 


17 


15£ 


2.23 


5000 


50.00 


1000 


930 


850 


772 


2.4 


5376 


53.76 


1075 


1000 


914 


834 


2.62 


5872 


58.72 


1130 


1100 


1000 


913 


2.88 


6451 


64.51 


1240 


1200 


1100 


1000 



One perch of stone is 24.75 cubic feet. 
In New York City laws a cubic foot of brick-work is deemed to weigh 
115 lbs. 
Building-stone is deemed to weigh 160 lbs. per cubic foot. 
The safe load for brick-work according to the New York City Laws is as 
folio ws : — 
In tons per superficial foot, 

For good lime mortar 8 tons. 

For good lime and cement mortar mixed . ll£ tons. 
For good cement mortar 15 tons. 

Average Ultimate <Hio.ltiii--I.oad in Pounds per Square 
Inch for Bricks, Stones, Mortars, and Cements. 



Lbs. per 
Sq. In. 



Brick, common (Eastern) 

Brick, best pressed 

Brick (Trautwine) 

Brick, paving, average of 10 varieties (Western) 

Brick-work, ordinary 

Brick-work, in good cement 

Brick-work, first-class, in cement 

Concrete (1 part lime, 3 parts gravel, 3 weeks old) 

Lime mortar, common , 

Portland cement, best English, 

Pure, three months old 

Pure, nine months old 

1 part sand, 1 part cement, 

Three months old 

Nine months old 

Granites, 7750 to 22,750 

Blue granite, Fox Island, Me 

Blue granite, Staten Island, N. Y 

Gray granite, Stony Creek, Conn 

North River (N. Y.) flagging 

Limestones, 11,000 to 25,000 

Limestone from Glen's Falls, N. Y. ... 

Lake limestone, Lake Champlain, N. Y. . . 

White limestone, Marblehead, O 

White limestone from Joliet, 111 

Marbles, 

From East Chester, N. Y 

Common Italian 

Vermont (Southerland Falls Co.) . . . . , 

Vermont, Dorset, Vt , 

Drab, North Bay Quarry, Wis , 



10000 

12000 

770 to 4660 

7150 
300 to 500 
450 to 1000 
930 
620 
770 

3760 
5960 

2480 

4520 
12000 
14875 
22250 
15750 
13425 
12000 
11475 
25000 
11225 
12775 

12950 
11250 
10750 
7612 
20025 



MISCELLANEOUS MATERIALS. 



1323 



Averag-e Ultimate Crushing-- JLoad — Continued. 



Lbs. per 
Sq. In. 



Sandstones 

Brown, Little Falls, N. Y 

Brown, Middletown, Conn. 

Red, Haverstraw, N. Y 

Red-brown, Seneca freestone, Ohio . . . 

Freestone, Dorchester, N. B 

Longmeadow sandstone, Springfield, Mass. 



6000 
9850 
6950 
4350 
9687 
9150 
8000 to 14000 



HHCELLAHE01JS mATERIAI^S. 

Weight of Round Bolt Copper Per Foot. 



Inches. 


Pounds. 


Inches. 


Pounds. 


Inches. 


Pounds. 


j 


1 


.425 


1 


3.02 


If 


7.99 






.756 


li 


3.83 


If 


9.27 


. 




1.18 


U 


4.72 


n 


10.64 






1.70 


11 


5.72 


2 


12.10 


i 




2.31 


ll 


6.81 









Weig-ht 


of Sheet and Bar Brass. 




Thick- 


Sheets 


Square 


Round 


Thick- 


Sheets 


Square 


Round 


ness. 


per 


Bars 


Bars 


ness. 


per 


Bars 


Bars 


Inches. 


sq. ft. 


1 ft. long. 


1 ft. long. 


Inches. 


sq. ft. 


1 ft. long. 


1 ft. long. 




lbs. 


lbs. 


lbs. 




lbs. 


lbs. 


lbs. 


t 


2.7 


.015 


.011 


It 


45.95 


4.08 


3.20 


5.41 


.055 


.045 


48.69 


4.55 


3.57 


f 


8.12 


.125 


.1 


\f 


51.4 


5.08 


3.97 


10.76 


.225 


.175 


54.18 


5.65 


4.41 


T 6 B 


13.48 


.350 


.275 


if 


56.85 


6.22 


4.86 


i 


16.25 


.51 


.395 


59.55 


6.81 


5.35 


h 


19. 


.69 


.54 


1t 7 s 


62.25 


7.45 


5.85 


i 


21.65 


.905 


.71 


l| 


65. 


8.13 


6.37 


24.3 


1.15 


.9 


ll 9 6 


67.75 


8.83 


6.92 


27.12 


1.4 


1.1 


If 


70.35 


9.55 


7.48 


* 


29.77 


1.72 


1.35 


m 


73. 


10.27 


8.05 


32.46 


2.05 


1.66 


if 


75.86 


11. 


8.65 " 


ft 


35.18 


2.4 


1.85 




78.55 


11.82 


9.29 


1 


37.85 


2.75 


2.15 


81.25 


12.68 


9.95 


11 


40.55 


3.15 


2.48 


lit 


84. 


13.5 


10.58 


1 


43.29 


3.65 


2.85 


2 


86.75 


14.35 


11.25 



Composition of Various Grades of Rolled Brass. 



Trade Name. 


Copper. 


Zinc. 


Tin. 


Lead. 


Nickel. 


Common high brass 

Yellow metal 

Cartridge brass 

Low brass 

Clock brass 

Drill rod ......... 


61.5 

60 

66| 

80 

60 

60 

66§ 

61£ 


38.5 

40 

33£ 

20 

40 

40 

33£ 

20£ 


'iV 


l£to2 




ii 




Spring brass 

18 per cent German silver . . . 





1324 FOUNDATIONS AND STRUCTURAL MATERIALS. 



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MISCELLANEOUS MATERIAL. 



1325 



Galvanized Iron IFire Rope. 

Charcoal Rope. For Ship's Rigging and Guys for Derricks. 



5 M 






®a3^ • 
w S3 

43 S<^ 

5^ OCC 



«h « 



11 

10* 
10 

9* 

9 

81 

8 

n 

eh 

6 

5f 

5i 






43 
40 
35 
33 
30 
26 
23 
20 
16 
14 
12 
10 



.5ft§i 



o o 

<*£ 3 tt) 

5^ OOQ 



5 

I 

3f 

3 

2* 

2| 

2§ 

If 

l| 

11 

1| 



Transmission or Haulage Rope. (Roeblingr.) 

Composed of H Strands and a Hemp Center, 7 Wires to the Strand. 

SWEDISH IRON. 







Approxi- 
mate Cir- 
cumfer- 
ence in 
Inches. 




Approxi- 


Allowable 


Mini- 


Trade 
Number. 


Diameter 

in 
Inches. 


Weight 

per Foot 

in Pounds. 


mate 

Breaking 

Strain in 

Tons of 


Working 

Strain in 

Tons of 

2,000 


mum Size 

of 

Drum or 

Sheave 








2,000 Lbs. 


Pounds. 


in Feet. 


11 


u 


4| 


3.55 


34 


6.80 


13 


12 


11 


3 


3.00 


29 


5.80 


12 


13 


H 


4 


2.45 


24 


4.80 


lOf 


14 


H 


3* 


2.00 


20 


4.00 


9* 


15 


l 


3 


1.58 


16 


3.20 


4 


16 


i 


2| 


1.20 


12 


2.40 


7 4 


17 


| 


2i 


0.89 


9.3 


1.86 


18 


11 


2i 


0.75 


7.9 


1.58 


6 


19 


i 


2 


0.62 


6.6 


1.32 


5i 


20 


& 


If 


0.50 


5.3 


1.06 


4 


21 


h 


1J 


0.39 


4.2 


0.84 


4 


22 


4 


l| 


0.30 


3.3 


0.66 


3£ 


23 


1 


ll 


0.22 


2.4 


0.48 


2| 


24 


T S 5 


1 


0.15 


1.7 


0.34 


3 


25 


& 


i 


0.125 


1.4 


0.28 


2i 



CAST STEEL. 



11 

12 
13 
14 
15 



16 
17 
18 
19 
20 



21 
22 
23 
24 
25 



if 

if 

i 



i 



4| 

4i 

4 

3* 

3 



3.55 
3.00 
2.45 

2.00 
1.58 



1.20 
0.89 
0.75 
0.62 
0.50 



0.39 
0.30 
0.22 
0.15 
0.125 



68 
58 
48 
40 
32 



24 

18.6 

15.8 

13.2 

10.6 



8.4 
6.6 
4.8 
3.4 
2.8 



13.6 
11.6 
9.60 
8.00 
6.40 



4.80 
3.72 
3.16 
2.64 
2.12 



1.68 
1.32 
0.96 
0.68 
0.56 



1326 FOUNDATIONS AND STRUCTURAL MATERIALS. 

Standard Hoisting* Rope. 

Composed of 6 Strands and a Hemp Center, 19 Wires to the Strand, 

SWEDISH IRON. 



B 




O CO 


cumfeiv 
nches. 


Weight 


Ap. 
Breaking 


Allowable 
Working 
Strain in 


Min. Size 
of 


eg 
u 
H 


§•3 

3 




per Foot in 
Lbs. 


in Tons 

of 

2,000 Lbs. 


Tons 

of 2,000 

Lbs. 


Drum or 
Sheave 
in Foot. 




2| 


8§ 


1195 


114 


22.8 


16 




2i 




9.85 


95 


18.9 


15 


1 


sj 


t| 


8.00 


78 


15.60 


13 


2 


2 


6i 


6.30 


62 


12.40 


12 


3 


If 


5* 


4.85 


48 


9.60 


10 


4 


If 


5 


4.15 


42 


8.40 


8| 


5 


ll 


4| 


3.55 


36 


7.20 


7f 


51 


If 


4i 


3.00 


31 


6.20 


7 


G 


H 


4 


2.45 


25 


5.00 


6* 


7 


H 


3£ 


2.00 


21 


4.20 


6 


8 


l 


3 


1.58 


17 


3.40 


5i 


9 


1 


2} 


1.20 


13 


2.60 


4 


10 


1 


2i 


0.89 


9.7 


1.94 


4 


m 


1 


2 


0.62 


6.8 


1.36 


3* 


ici 


& 


If 


0.50 


5.5 


1.10 


2f 


10| 


^ 


$ 


0.39 


4.4 


0.88 


2J 


10a 


7 


0.30 


3.4 


0.68 


2 


106 


I 


if 


0.22 


2.5 


0.50 


n 


10c 


£$ 


i 


0.15 


1.7 


0.34 


i 


10a* 


i 


1 


0.10 


1.2 


0.24 


i 



CAST STEEL. 





2| 


8f 


11.95 


228 


45.6 


10 




2* 


7£ 


9.85 


190 


37.9 


9* 


1 


2i 


7* 


8.00 


156 


31.2 


4 


2 


2 


61 


6.30 


124 


24.8 


8 


3 


If 


5* 


4.85 


96 


19.2 


n 


4 


\l 


5 


4.15 


84' 


16.8 


6? 


5 


S 


3.55 


72 


14.4 


5| 


5* 


If 


3.00 


62 


12.4 


5£ 


6 


li 


4 


2.45 


50 


10.0 


5 


7 


ll 


3J 


2.00 


42 


8.40 


4* 


8 


1 


3 


1.58 


34 


6.80 


4 


9 


! 


2| 


1.20 


26 


5.20 


3£ 


10 


2i 


0.89 


19.4 


3.88 


3 


10i 


f 


2 


0.62 


13.6 


2.72 


21 


10} 


ft 


If 


0.50 


11.0 


2.20 


If 


10f 


t 


H 


0.39 


8.8 


1.76 


1* 


10a 


t 


l| 


0.30 


6.8 


1.36 


ii 


106 


It 


0.22 


5.0 


1.00 


i 


10c 


t 


1 


0.15 


3.4 


0.68 


§ 


lOd 


1 


0.10 


2.4 


0.48 


* 



STEAM BOILERS. 1327 



STEAM. 

STEAM BOILERS. 
Points to Remember in Selecting* a Boiler. 

(a) Suitability of furnace and boiler to kind of fuel. 

(b) Efficiency as to evaporative results. 

(c) Rapidity of steaming including 

(I.) "Water capacity for given power. 
(II.) Water surface for given power. 

{d) Steam keeping qualities. 

(e) Safety from explosion. 

(/) Floor space required. 

(g) Portability, and ease with which boiler can be removed when old, for 
replacement by a new boiler. 

(h) Amount of, ease of, and rapidity of repairs. 

(i) Simplicity and fewness of parts. 

(j) Ability to stand forcing in case of necessity. 

(k) Price, including cost of freight and setting. 

(I) Durability and reliability, 
(m) Ease of cleaning and inspection both inside and outside. 

(n) Freedom from excessive strains due to unequal expansion and ability 
to withstand same. 

(o) Efficient natural circulation of water. 
(p) Absence of joints or seams where flames may impinge. 

For central stations it is necessary to arrange for a number of boilers 
rather than one or two large ones. The size of unit adopted will depend 
to some extent on the character of the expected load diagram. With a 
number of boilers the cost of the reserve plant is reduced, though beyond, 
say six, there is less object in increasing the number on this account. 

Types. 

Horizontal Return Tubular. — More generally used in United 
States than any other. Fire first passes under the shell, returns to front 
through tubes, thence up the chimney, except in some cases gases are again 
returned over top of the shell. Limited as to size and pressures carried by 
reason of external tiring. 

Water-tube. — Very largely used where high steam pressures or 
safety from explosion are desirable. Fire passes about the exterior of tubes 
and in most cases under about one-half the circumference of the steam 
drums. Can be built for any size or pressure. Tubes are generally placed 
in a slanting position, from one set of headers to another, as in the Babcock 
& Wilcox, Heine & Co. ; or vertically, as in the Sterling and Cahall. 

Vertical Eire Tube. — Used considerably in New England. Spe- 
cial design by Captain Manning; tubes 15 feet long 2\ inches diameter, 
arranged in vertical shell with large combustion chamber surrounded by a 
water leg. Gases mingle in combustion chamber, and in passing through the 
long narrow tubes give up nearly all the heat, practicably leaving flue gases 
450° to 500° F. By controlling height of water, steam can be superheated. 
Can be built for high pressures and of large size. 

m?™ * S-°I Marin « Boilers. — Not much used for electrical purposes, 
bnell of thick material, short in length and large in diameter. Furnaces 
internal, with return tubes from combustion chamber to uptake, 
i ?*wXn? S are the Winder boiler, of small diameter and considerable 
lengtn (20 to 35 feet). Fired externally, and gases pass under full length to 
cnimney. Flue boiler, has two or three large tubes running full length of 
snen, which is long and of small diameter. Fired externally under the shell, 
gases return through the flues to uptake. Neither of these types is now 
us«d for electrical purposes. 

The Horse-Power of Steam Boiler. 

The committee of the A. S. M. E. on "Trials of Steam Boilers in 1884" 
CTranSc,vol. vi. p. 265), discussed the question of the horse-power of boilers ; 



1328 STEAM. 



The Committee) A.S.M.E. see Trans, vol. xxi.) approves the conclusions of 
the 1885 Code to the effect that the standard " unit of evaporation " should 
be one pound of water at 212° F. evaporated into dry steam of the same 
temperature. This unit is equivalent to 965.7 British thermal units. 

The committee recommends that, as far as possible, the capacity of a 
boiler be expressed in terms of the " number of pounds of water evaporated 
per hour from and at 212°." It does not seem expedient, however, to aban- 
don the widely recognized measure of capacity of stationary or land boilers 
expressed in terms of " boiler horse-power." 

The unit of commercial boiler horse-power adopted by the Committee of 
1885 was the same as that used in the reports of the boiler tests made at the 
Centennial Exhibition in 1876. The Committee of 1885 reported in favor of 
this standard in language of which the following is an extract : 

" Your Committee, after due consideration, has determined to accept the 
Centennial standard, and to recommend that in all standard trials the com- 
mercial horse-power be taken as an evaporation of 30 pounds of water per 
hour from a feed-water temperature of 100° F. into steam at 70 pounds gauge 
pressure, which shall be considered to be equal to 34J units of evaporation ; 
that is, to 34£ pounds of water evaporated from a feed-water temper- 
ature of 212° F. into steam at the same temperature. This standard is 
equal to 33,305 thermal units per hour." 

The present Committee accepts the same standard, but reverses the order 
of two clauses in the statement, and slightly modifies them to read as follows : 

The unit of commercial horse-power developed by a boiler shall be taken 
as 34£ units of evaporation per hour ; that is, 34£ pounds of water evaporated 
per hour from a feed-water temperature of 212° F. into dry steam of the 
same temperature. This standard is equal to 33,317 British thermal units 
per hour. It is also practically equivalent to an evaporation of 30 pounds 
of water from a feed-water temperature of 100° F. into steam at 70 pounds 
gauge pressure.* 

The Committee also indorses the statement of the Committee of 1885 con- 
cerning the commercial rating of boilers, changing somewhat its wording, so 
as to read as follows : 

A boiler rated at any stated capacity should develop that capacity when 
using the best coal ordinarily sold in the market where the boiler is located, 
when fired by an ordinary fireman, without forcing the fires, while exhibit- 
ing good economy ; and, further, the boiler should develop at least one- 
third more than the stated capacity when using the same fuel and operated 
by the same fireman, the full draft being employed and the fires being 
crowded ; the available draft at the damper, unless otherwise understood, 
being not less than \ inch water column. 

Heating: Surface of Boilers. 

Although authorities disagree on what is to be considered the heating 
surface of boilers, it is generally taken as all surfaces that transmit heat 
from the flame or gases to the water. The outside surface of all tubes is 
used in calculations. 

Kent gives the following rule for finding the heating surface of 

Vertical Tubular Boilers. — Multiply the circumference of the fire- 
box (in inches) by its height above the grate. Multiply the combined circum- 
ference of all the tubes by their length, and to these two products add the area 
of the lower tube sheet ; from this sum subtract the area of all the tubes, 
and divide by 144 : the quotient is the area of heating surface in square feet. 

Horizontal Return Tubular Boilers. — (Christie). Multiply the 
length of that part of circumference of the shell (in inches) exposed to the 
fire by its length ; multiply the circumferences of the tubes by their num- 
ber, by their length in inches ; to the sum of these products add two-thirds 
of the area of both tube sheets less twice the area of tubes, and divide the 
remainder by 144. The result is the heating surface in square feet. 

Heating: Surface of Tubes. — Multiply the number of tubes by the 
diameter of a tube in inches, by its length in feet, and by .2618. The diam- 
eter used should be that of the fire side of the tube. 

* According to the tables in Porter's Treatise on the Richards Steam En- 
gine Indicator, an evaporation of 30 pounds of water from 100° F. into steam 
at 70 pounds pressure is equal to an evaporation of 34.488 pounds from and 
at 212° ; and an evaporation of 34\ pounds from and at 212° F. is equal to 
30.010 pounds from 100° F. into steam at 70 pounds pressure. 

The " unit of evaporation" being equivalent to 965.7 thermal units t the 
commercial horse-power = 34.5 x 965.7 = 33 s 317 thermal units. 



STEAM BOILERS. 



1329 



Heating* Surface per Horse-power. — There is little uniformity 
of practice among builders as to the amount of heating surface per horse- 
power, but 12 square feet may be taken as a fair average. Babcock & Wil- 
cox ordinarily allow 10 square feet, but usually specify the number of 
square feet of heating surface. The Heine Boiler Company allow 1\ square 
feet, and the water-tube type in general will develop a horse-power for that 
amount of surface. 

Specifications for boilers should always clearly state the amount of heating 
surface required. 

Orate Surface. — The amount of grate surface per horse-power varies 
with the character of fuel used and the draught that is available. With 
good quality of coal about equal results can be obtained with strong draught 
and small grate surface, and with large grate surface and light draught. 
Pittsburg coal gives best results with strong draught and a small grate sur- 
face. The following table shows the usual requirements, but in general 
grate surface should be liberal in size, and a rate of combustion of about 
10 lbs. per hour will be found good practice. 

Grrate Surface per Horse-Power. (Kent.) 



oSSoO 



on 3 

S u u 



Pounds of Coal burned per square foot 
of Grate per hour. 



8 10 12 15 20 25 30 35 40 



Square Feet Grate per H.P. 



Good coal and 
boiler . . . 

Fair coal or 
boiler . . . 

Poor coal or 
boiler . . . 

Lignite and 
poor boiler . 



10 
9 

8.61 

8 

7 

6.9 

6 

5 

3.45 



3.45 

3.83 

4. 

4.31 

4.93 

5. 

5.75 

6.9 

10. 



.43 


.35 


.28 


.23 


.17 


.14 


.11 


.10 


.48 


.38 


.32 


.25 


.19 


.15 


.13 


.11 


.50 


.40 


.33 


.26 


.20 


.16 


.13 


.12 


.54 


.43 


.36 


.29 


.22 


.17 


.14 


.13 


.62 


.49 


.41 


.33 


.24 


.20 


.17 


.14 


.63 


.50 


.42 


.34 


.25 


.20 


.17 


.15 


.72 


.58 


.48 


.38 


.29 


.23 


.19 


.17 


.86 


.69 


.58 


.46 


.35 


.28 


.23 


.22 


1.25 


1.00 


.83 


.67 


.50 


.40 


.33 


.29 



.09 
.10 
.10 
.11 
.12 
.13 
.14 
.17 

.25 



Area of Gas-Passages and Flues. 

This is commonly stated in a ratio to the grate area. Mr. Barrus says the 
highest efficiency for anthracite coal, when burning 10 to 12 lbs. per square 
foot of grate per hour, is with tube area | to T ^ of grate surface ; and for soft 
coal the tube area should be ^ to | of the grate surface. 

Other rules in common use are to make the area over bridge walls (for 
horizontal return tubular boilers) \ the grate surface ; tube area£ and chim- 
ney area £. 

Air-space in Orates. — Usual practice is 30% to 50% area of grate for 
air space. If fuel clinkers easily, use the largest air space available. With 
coal free from clinker smaller air space may be used. 

Distance between Under Side of Boiler and Top of Orate. 

(For Horizontal Tubular Boiler.) 
For anthracite coal this should be 24 inches for the larger sizes, and can 
be 20 inches for the smaller sizes, such as pea, buckwheat, and rice. For 
bituminous coals non-caking, the grate should be about 30 inches below the 
boiler, and for fatty or gaseous coals from 36 to 48 inches. For average 
bituminous coals the distance can be 36 inches. Anthracite and bituminous 
coals cannot be economically burned in the same furnace. 

Steam Boiler Efficiency. 

The ratio of the heat units utilized in making steam in a boiler, to the 
total heat units in the coal used is called the efficiency of the boiler, and is 



1330 



STEAM. 



rated in per cent. For example, the heating value of good anthracite coal 
is about 14,500 B. T. U., and will evaporate from and at 212° 15 lbs. water 
(14,500 -J- 966). If a boiler under test evaporates 12 lbs. water per pound of 

12 X 100 
combustible, the efficiency will be — — = 80%, a figure not often ob- 
tained, but possible under special conditions. The heating value of bitumi- 
nous coals varies so much that it is necessary to determine it by a coal 
calorimeter before it is possible to determine the boiler efficiency. 

Strength of Riveted Shell. 

(Abridged from Barr on " Boilers and Furnaces.") 
Wrought-iron "boiler-plates should average 45,000 lbs., and mild steel 55,000 
lbs., tensile strength per square inch of section ; but the gross strength of 
plate is lessened by the amount which has been taken out of it for the inser- 
tion of rivets. 

The following tables give the calculated working pressure for double- 
riveted and triple-riveted lap joints, and for butt-joints triple riveted, the 
factor of safety being 5. The rule for calculating the safe working pressure 
is : Multiply together the tensile strength of the plate, the thickness of the 
plate in parts of an inch, and the efficiency of the joint (see Riveting) ; divide 
the product by one-half the diameter of the boiler multiplied by the factor 
of safety. 

Working* Pressure for Cylindrical Shells of Steam Boilers. 

Factor of Safety, 5. (Barr.) 







Lap-joints, Double-Riveted. 


Lap- Joints, Triple 


-Riveted. 




Thick- 














Diam- 


ness in 














eter 


16ths 
of an 
Inch. 


Iron 


Steel 


Steel 


Iron 


Steel 


Steel 


Inches. 


Shell, 


Shell, 


Shell, 


Shell, 


Shell, 


Shell, 




Iron 


Iron 


Steel 


Iron 


Iron 


Steel 






Rivets. 


Rivets. 


Rivets. 


Rivets. 


Rivets. 


Rivets. 


36 


4 


91 


Ill 


Ill 


100 


121 


123 


5 


112 


128 


137 


124 


139 


151 


40 


4 


82 


100 


100 


90 


109 


110 


5 


101 


115 


123 


112 


125 


136 


44 


4 


74 


91 


91 


83 


99 


100 


5 


91 


105 


112 


101 


114 


124 


48 


5 


84 


96 


102 


93 


104 


114 


6 


99 


107 


121 


110 


118 


135 


52 


5 


77 


89 


95 


86 


96 


105 


6 


92 


99 


112 


102 


109 


124 


54 


5 


75 


85 


91 


83 


93 


101 


6 


88 


96 


108 


98 


105 


120 


56 


5 


72 


82 


88 


80 


89 


97 


6 


85 


92 


104 


95 


101 


116 


60 


5 


67 


77 


82 


74 


83 


91 


6 


79 


85 


97 


88 


95 


108 


62 


6 


77 


83 


94 


85 


92 


104 


7 


88 


92 


108 


98 


103 


120 


64 


6 


74 


81 


91 


83 


89 


101 


7 


86 


89 


105 


95 


100 


117 


66 


6 


72 


78 


88 


80 


86 


98 


7 


83 


87 


102 


93 


97 


113 


68 


6 


70 


76 


86 


78 


84 


95 


7 


81 


80 


99 


90 


94 


110 


70 


6 


68 


74 


83 


76 


81 


92 


7 


78 


82 


96 


87 


91 


107 


72 


7 


76 


79 


93 


85 


89 


104 


8 


85 


89 


104 


97 


98 


117 



STEAM BOILERS. 



1331 



Working* Pressure for Cylindrical Shells of 
Steam Hollers. (Barr.) 

Butt Joints, Triple Riveted. Factor of Safety , 5. 



Diameter 
Inches. 


Thick- 
ness in 
16ths of 
an inch. 


Iron 

Shell, 

Iron 

Rivets. 


fir 

Steel 

Shell, 

Iron or 

Steel 

Rivets. 


Diam- 
eter, 
Inches. 


Thick- 
ness in 
16ths of 
an inch. 


Iron 

Shell. 

Iron 

Rivets.* 


Steel 
Shell, 
Iron or 

Steel 
Rivets. 




4 


108 


134 




6 


83 


102 


36 


5 


135 


165 


70 


7 


97 


118 




6 


161 


197 


8 


110 


134 




4 


102 


127 




9 


123 


151 


38 


5 


128 


156 




6 


80 


99 




6 


152 


187 


72 


7 


94r 


115 




4 


97 


120 


8 


107 


131 


40 


5 


121 


148 




9 


120 


147 




6 


145 


178 




7 


90 


110 




4 


93 


115 


75 


8 


102 


125 


42 


5 


116 


141 


9 


115 


141 




6 


138 


169 




10 


128 


157 




4 


89 


109 




7 


87 


106 


44 


5 


110 


135 


78 


8 


99 


121 




6 


132 


161 


9 


111 


135 




4 


85 


105 




10 


123 


151 


46 


5 


106 


129 




8 


92 


112 




6 


126 


154 




9 


103 


126 




5 


101 


124 


84 


10 


115 


140 


48 


6 


121 


148 




11 


126 


158 




7 


141 


172 




12 


137 


167 




5 


97 


119 




8 


86 


105 


50 


6 


116 


142 




9 


96 


117 




7 


135 


165 


90 


10 


107 


131 




5 


93 


114 




11 


117 


143 


52 


6 


111 


137 




12 


128 


156 




7 


130 


159 




8 


80 


98 




5 


90 


110 




9 


90 


110 


54 


6 


107 


132 


96 


10 


100 


123 




7 


125 


153 




11 


110 


134 




5 


87 


106 




12 


120 


146 


56 


6 


103 


127 




8 


75 


92 




7 


121 


148 




9 


85 


104 




5 


84 


102 


102 


10 


94 


115 


58 . 


6 


100 


123 




11 


104 


127 




7 


117 


142 




12 


113 


138 




6 


97 


118 




8 


71 


87 


60 


7 


111 


138 




9 


80 


98 




8 


128 


157 


108 


10 


89 


109 




6 


93 


115 




11 


98 


120 


62 


7 


109 


133 




12 


107 


130 




8 


124 


152 




8 


68 


83 




6 


90 


111 




9 


76 


93 


64 


7 


106 


129 


114 


10 


84 


103 


8 


120 


147 




11 


93 


113 




9 


135 


165 




12 


101 


123 




6 


88 


108 




8 


64 


78 


66 


7 


102 


125 




9 


71 


88 


8 


117 


143 


120 


10 


80 


98 




9 


131 


160 




11 


88 


108 




6 


85 


105 




12 


96 


117 


68 


7 


99 


121 










8 


113 


138 












9 


127 


155 











1332 STEAM. 

Safe Working; Pressure for Shell Plate. 

U. S. Statutes. — 

d — diameter of boiler in inches. 
P=. safe working pressure, lbs. per square inch. 
t =z thickness of metal in inches. 
w =z tensile strength of metal. 
k =z factor of safety = 6 for U. S. and 4.5 for Great Britain. 

^ y 2 x ic 

P — - — for single-riveted. For double-riveted, add 20%. 

d X 6 ° ' 

Board of Trade.— 

> X B X t X 2 



P = 



d X fc X 100 



where the notation is the same as in U. S. rule, and B = percentage of 
strength of joint as compared with solid plate. 

Rules Governing' Inspection of Boiler* in Philadelphia. 

In estimating the strength of the longitudinal seams in the cylindrical 
shells of boilers, the inspector shall apply two formulae, A and B : 



A, 



Pitch of rivets — diameter of holes punched to receive the rivets __ 
~~ pitch of rivets ~" 

percentage of strength of the sheet at the seam. 

SArea of hole filled by rivet x No. of rows of rivets in seam x shear- 
ing strength of rivet _ 
pitch of rivets X thickness of sheet x tensile strength of sheet 
percentage of strength of the rivets in the seam. 
Take the lowest of the percentages as found by formulas A and B, and 
apply that percentage as the " strength of the seam" in the following for- 
mula, C, which determines the strength of the longitudinal seams : 

! Thickness of sheet in parts of inch x strength of seam as obtained 
by formula A or B x ultimate strength of iron stamped on plates _ 
internal radius of boiler in inches X 5 as a factor of safety 
safe working pressure. 

Safe Working: Pressure for Flat Plates. 

U. S. Statutes. — 

P = safe working pressure. 

S =r surface supported, square inches. 

t — thickness of metal in sixteenths of an inch. 

k — constant for plates of different thickness, and for various condi- 
tions. 
p — greatest pitch in inches. 

P -L*±. 
~ p 2 

K— 112 for T Vinch plates and less, fitted with screw stay bolts and nuts, or 
plain bolt fitted with single nut and socket, or riveted head and 

K= 120 for plates more than T 7 g inch thick, under same conditions. 

#:= 140 for flat surfaces where the stays are fitted with nuts inside and out. 

K=z 200 for flat surfaces under same conditions, but with washer riveted to 

plate, washer to be one-half as thick as plate, and of a diameter f 

pitch. 



STEAM BOILKBS. 



1333 



No brace or stay on marine boilers to have a greater pitch than 10J 
inches on fire boxes and back connections. Plates fitted with double-angle 
irons riveted to plate, and with leaf at least two-thirds thickness of plate, 
and depth at least one-fourth of pitch, allowed the same pressure as plate 
with washer riveted on. 

Board of Trade. — Using same notation as in U. S. rules : 

p __ * (< + !)* 
S — 6 

JT = 125 for plates not exposed to heat or flame, the stays fitted with nuts 

and washers, the latter at least three times the diameter of the stay 

and § the thickness of the plate ; 
K=. 187.5 for the same condition, but the washers | the pitch of stays in 

diameter, and thickness not less than plate ; 
K = 200 for the same condition, but doubling plates in place of washers, the 

width of which is f the pitch, and thickness the same as the plate ; 
K =: 112.5 for the same condition, but the stays with nuts only ; 
K = 75 when exposed to impact of heat or flame and steam in contact with 

the plates, and the stays fitted with nuts and washers three times 

the diameter of the stay, and § the plate's thickness ; 
7T = 67.5 for the same condition, but stays fitted with nuts only ; 
K = 100 when exposed to heat or flame, and water in contact with the 

plates, and stays screwed into the plates, and fitted with nuts ; 
K = 66 for the same condition, but stays with riveted heads. 

Ductility of Boiler Plate. — U. S. Inspectors of Steam Vessels. 

In test for tensile strength, sample shall show reduction of area of cross- 
section not less than the following percentages : 

Iron. 

45,000 lbs. tensile strength and under 15 per cent. 

For each additional 1000 t. s. up to 55,000 t. s. add . 1 " 
55,000 lbs. tensile strength, and above 25 '* 

Steel. 

All steel plates £ inch thick and under 50 per cent. 

" " " } to | inch 45 " 

M " " I inch and above 40 " 



Boiler Head Stays. 

The United States Regulations on braces are : " No braces or stays here- 
after employed in the construction of boilers shall be allowed a greater 
strain than 6,000 lbs. per square inch of section. Braces must be put in suf- 
ficiently thick so that the area in inches which each has to support, multi- 
plied by the pressure per square inch, will not exceed 6,000 when divided by 
the cross-sectional area of the brace or stay. 

11 Steel stay-bolts exceeding a diameter of \\ inches, and not exceeding a 
diameter of 1\ inches at the bottom of the thread may be allowed a strain 
not exceeding 8,000 lbs. per square inch of cross-section ; steel stay bolts 
exceeding a diameter of 1\ inches at bottom of thread may be allowed a 
strain not exceeding 9,000 lbs. per square inch of cross-section ; but no 
forged or welded steel stays will be allowed. 

"The ends of such stay may be upset to a sufficient thickness to allow 
for truing up, and including the depth of the thread. And all such stays 
after being upset, shall be thoroughly annealed.** 



1334 



STEAM. 



Direct Braces. — The following table is given by Mr. W 
io,;' Boilers and Furnaces," p. 122. The working strength assun 
mate strength of 6000 lbs. per square inch of section. 



M. Barr 
assumes an ulti. 



Diam- 
eter of 


Wrought Iron 
Stays. 


Inches square each B 
Pressures per 


race will Support for 
Square Inch. 


Brace 
Inches. 


Area 
sq. in. 


Working 
Strength 
Pounds. 


75 
Pounds. 


100 
Pounds. 


125 
Pounds. 


150 
Pounds. 


i 
1 

n 
if 


.60 

.78 

.99 

1.23 

1.48 

1.77 


3600 
4712 
5964 
7362 
8880 
10620 


7.0 
7.9 
8.9 
9.9 
10.7 
11.9 


6.0 
6.9 
7.7 
8.6 
9.5 
10.4 


5.4 
6.1 
6.9 

7.7 
8.5 
9.2 


4.9 
5.6 
6.4 

7.0 

7.7 
8.5 



Diagonal Braces. — (" Boilers and Furnaces," p. 129.) These must be 
calculated separately. 



Let 



Then 



A = surface to be supported in square inches. 
B z=z working pressure in lbs. 
H=z length of diagonal stay in inches. 

L = length of line drawn at right angles from surface, to be sup- 
ported to end of diagonal stay in inches. 

S =: working stress per square inch on stay in lbs. 

a = area required for direct stay in square inches. 
a x zr area of diagonal stay in square inches. 

T=z diameter of diagonal stay in inches. 

H — a x x L -± a. 



▼ .7854 y .% 



X fix H. 



'854 $ X L 



.7854 XT* XSXL 
AxH 



Boiler Setting's. 



Water tube and special types of boilers require special settings largely 
controlled by local conditions, location of flues, etc., and cannot be tabulated 
here. 

The setting of horizontal return tubular boilers has become so nearly 
standardized that the table following, taken in connection with the cuts, 
will give all the general dimensions of brick-work required. 

For all special boiler settings, furnaces, etc., the reader is referred to the 
makers of each. 



STEAM BOILERS. 



1335 




Fig. 3. 



1336 



STEAM. 



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STEAM BOILERS. 



1337 





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7100 
8200 
8750 
9250 
10700 
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14450 
17680 
16600 
17900 
19000 
19600 
21550 
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£ 


Ft. In. 

9- 1 

9- 1 
10- 1 
10- 1 

10- 5 

11- 2 

11- 6 
12- 
12- 

12- 8 

12- 8 

13- 2 
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1338 



STEAM. 



CHIUINEXS. 

The draught power of a chimney varies as the square root of the 
height. 

The retarding friction of the chimney may be taken as equivalent to a 
diminution of its actual area by a layer of gas two inches thick all the way 
around the perimeter of its flue. 

A = actual area of flue in square feet. 
E = effective area of flue in square feet. 
H=: height in feet. 
D =. diameter of flue in feet. 
D t = side of a square chimney equivalent to A, 
Then : E —A — 0.6VZ. ft 

!>!= V^-f 4 mches. (2) 

Horse-power = 3.33 E^M. (3) 

The above formulae are by Kent, and are based on a consumption of 5 
lbs. coal per h. p. per hour. W. W. Christie, in a paper read before the 
A.S.M.E., Trans., vol. xviii., p. 387, gives as his opinion that all chimneys 
should be compared and rated by using coal capacity as a basis, not horse- 
power. In the following table, coal capacity can be found by multiplying 
h.p. by 4. 

Size of Chimneys for Steam-Boilers. 

(W. W. Christie.) 



72 

78 
84 

90 
96 
102 

108 

114 
120 
132 
144 













Height 


of Chimney. 










50 
ft. 


60 
ft. 


70 
ft. 


80 
ft. 


90 
ft. 


100 
ft. 


110 
ft. 


125 
ft. 


150 
ft. 


175 
ft. 


200 
ft. 


225 

ft. 


250 
ft. 


300 
ft. 


Boiler Horse-power=r 3.25 jS H\ 4 lbs. of coal burned considered 1 H.P. 


4 2 
55 
72 
91 

114 


46 
62 
78 
101 

124 
149 
179 


49 
65 
85 
107 

133 
163 
192 
224 

263 


52 

68 

91 

114 

143 
172 
205 
241 

282 
364 


1 

98 
124 

153 

182 

218 
257 

296 
387 
491 
605 


1 

159 
192 
228 
270 

312 
410 
517 
637 

774 

920 


202 
241 

283 

332 
429 
543 

669 

809 
962 
1131 
1310 


1 


1 


1 


1 








257 
302 

351 

458 
579 
715 

865 

ia5i 

1206 
1401 

1609 
1830 
2067 
2314 


























390 
510 
647 
797 

965 
1147 
13*9 
1563 

1794 
2041 
2304 

2584 

2879 
3191 
3861 
4596 






















683 
845 

1021 
1215 
1459 
1654 

1898 
2161 
2434 
2734 

3045 
3374 
4082 
4859 


















1092 
1300 
1524 
1768 

2031 
2311 
2607 
2925 

3257 
3611 
4368 
5200 


1378 
1619 
1875 

2155 
2451 
2766 
3101 

3455 
3*29 
46bl 
5515 


1706 
1976 

2269 
2584 
2915 
3269 

3643 
4037 
4882 
5811 


2165 

2486 
2831 
3195 
3578 

3991 
4420 
5350 
6367 



CHIMNEYS, 



1339 



The following table* will prove useful to those having to do with electric 
installations, and gives the horse-power of chimneys to be used in power 
plants having very efficient engines, such as compound or triple expansion 
engines, when 2 lbs. of coal burned under the boiler produce one horse- 
power at the engine. 

Size of Chimney for Steam Boilers. 

(W. W. Christie.) 





Height of Chimney. 


a 


50' 


60' 


70' 


80' 


90' 


100 / 


IKK 


125' 


150 7 


175' 


200' 


225' 


250' 


30O 7 


e3 

s 


Horse-i 


>ower = 6.5 A^H. When 2 lbs. 


coal burned per hour = 1 H.P. 


18 
21 

24 

27 


84 
110 
144 

182 


f 
92 
124 
156 

202 


98 
130 
170 
214 


104 
136 

182 
228 


1 

196 
248 






1 














30 
33 
36 
39 


228 


248 

298 
358 


266 
326 
384 
448 


286 
344 
410 

482 


306 
364 
436 
514 


318 
384 
456 
540 


404 

482 
566 
















514 
604 


























42 






526 


564 

728 


592 

774 

982 

1210 


62* 

820 

1034 

1274 


662 

858 

1086 

1338 


702 

916 

1158 

1430 


780 
1020 
1294 
1594 












48 
54 
60 












1366 
1690 


















66 

72 
78 
84 












1548 
1840 


1618 
1924 
2262 
2620 


1730 
2102 
2412 
2802 


1930 
2294 
2698 
3126 


2042 
2430 
2918 
3308 


2184 
2600 
3048 
3536 


2756 
3238 
3750 


3412 
3952 


4330 


90 

96 

102 

103 




»• 












3218 
3660 
4134 
4628 


3588 
4082 
4608 
5168 


3796 
4322 
4868 
5468 


4062 
4622 
5214 
5850 


4310 
4902 
5532 
6202 


4538 
5168 
5830 
6538 


4972 
5662 
6360 
7156 


114 
120 
132 
144 


















5758 
6382 
7722 
9192 


6090 
6748 
8164 
9718 


6514 
8736 


6910 
9262 


7286 
9764 


7982 
10700 



Chimney Construction. 

A brick chimney shaft is made up of a series of steps, each of which is of 
uniform thickness, but as we ascend each succeeding step is thinner than 
the one it rests upon. These bed joints at which the thickness changes are 
the joints of least stability. The joints and the one at the ground line 
are the only ones to which it is necessary to apply the formulas for deter- 
mining the stability of the stack. 

The height of the different steps of uniform thickness varies greatly, ac- 
cording to the judgment of the engineer, but 170 feet is, approximately, the 
extreme height that any one section should be made. This length is seldom 
approached even in the tallest chimneys, as the brick-work has to bear, in 
addition to its weight, that due to the pressure of the wind. The steps 
should not exceed about 90 feet, unless the chimney stack is inside a tower 
which protects it from the wind. In chimneys from 90 to 120 feet high the 
steps vary from 17 to 25 feet, the top step being one brick thick ; in chim- 



* ^Chimney Design and Theory," W. W.Christie, D. VanNostrand Company. 



1340 



STEAM. 



B (2 
0Q@ 







Perforated radial bricks used for chimneys. 




Bond in radial brick work. 
Fig. 4. 



CHIMNEYS. 1341 



neys from 130 to 150 feet the steps vary from 25 to 35 feet; in chimneys from 
150 to 200 feet the steps vary from 35 to 50 feet; in chimneys from 200 to 
300 feet and over, the steps vary from 50 to 90 feet, the top step being on© 
and one-half bricks thick. The outside dimensions of a chimney at the 
base should generally not be less than one-tenth of the height of the stack 
for square chimneys; one-eleventh for octagonal, and one-twelfth for round. 
The battery may be 2£ inches for every 10 feet. 

The foundation of a chimney is one of the most important points to be 
considered. When this is upon solid rock it is only necessary to excavate 
to a depth sufficient to prevent the heat of the gases from materially affect- 
ing the natural stone, and to secure the spread of the base. In cases where 
chimneys are to be built upon alluvial clays or made ground, it is necessary 
to excavate until a good stiff clay, hard sand, or rock bottom is reached. 
The excavation is tilled with concrete in various ways, or filled according 
to the judgment of the engineer, so as to economize material without 
endangering the structure. 

Babcock and Wilcox give the following formula for the ability of brick 
chimneys to withstand wind pressure. 

w=. weight of chimney in lbs. (brickwork = 100 to 130 lbs. 

per cubic foot.) 
d — average diameter in feet, or width if square. 
h = height in feet. 
b = width of base. 

k =z constant, for square chimneys = 56. 

for round chimneys z=z 28. 

for octagonal chimneys = 35. 

c=zk — — and w = k -=— . 
w b 



Radial Brick Chimneys. 

Another type of chimney now much used in the East, is built of radial 
brick, perforated vertically with holes about 1" square, passing entirely 
through them. 

The advantage of these bricks is said to be a better bond, as the cement 
makes a dowel in the perforations. 

They are made of a special quality of clay, having greater care in the 
making, are burned at a greater heat than the red brick, and are said to be 
of a more uniform grade. 

Radial brick chimneys as built in the United States do not always have 
lining, for the brick are supposed to be capable of withstanding the heat of 
the gases usually met with, but in special cases a lining is built in them, and 
is carried by the outer shell. 

The less number of joints to the weather is also given as a point in favor 
of the radial brick chimney. 

In making comparisons of the costs of the several types of chimneys, if of 
brick, they should have the same 

height, 

inside diameter, 
lightning protection details, 
ladder equipment, 
quality of workmanship, 
.same factor of stability. 



1342 



STEAM. 



Draft Power for Combustion of Fuels. 

(R.H.Thurston.) 



Fuel. 



Draft of Chini 

ney in Inches 

of Water. 



Fuel. 



'Draft in Ins. 
of Water. 



Wood 

Sawdust . . . 
Sawdust mixed 

small coal . . . 
Steam coal . . , 
Slack, ordinary , 

Slack, very small . 



with 



0.20 to 0.25 
0.50 



0.35 

0.60 

0.40 
0.60 

0.75 



0.75 

0.75 
0.90 

1.25 



Coal-dust 

Semi Anthracite coal 
Mixture of breeze and 

slack 

Anthracite ... . 
Mixture of breeze and 

coal-dust .... 
Anthracite slack . . 



0.80 to 1.25 
1.25 



0.90 
1.00 
1.25 
1.25 
1.30 



1.33 
1.50 
1.75 
1.80 



Heig-ht of Chimney for Burning' Given Amounts of Coal. 

Professor Wood (Trans. A. S. M. E., vol. xi.) derives a formula from 
which he calculates the height of chimney necessary to burn stated quan- 
tity of coal per square foot of grate per hour, for certain temperatures of 
the chimney gas. 





Absolute 


Pounds of Coal per 


Square Foot Grate Area. 


Temp. 










Outside 


Temp. Chim- 


16 




20 


24 


Air. 


ney Gases. 








Height of 


Chimney, Feet. 


© 


700 


67.8 




157.6 


250.9 


49 


800 


55.7 




115.8 


172.4 


©J3 


1000 


48.7 




100.0 


149.1 




1100 


48.2 




98.9 


148.8 


1200 


49.1 




100.9 


152.0 


« <5 


1400 


51.2 




105.6 


159.9 


o %a 


1600 


53.5 




110.9 


168.8 


2000 


63.0 




132.2 


206.5 



Rate of Combustion Due to Heig-ht of Chimney. 

Prof. Trowbridge (" Heat and Heat Engines," p. 153) gives the following 
table, showing the heights of chimneys for producing certain rates of com- 
bustion per square foot of area of section of the chimney. The ratio of the 
grate to the chimney section being 8 to 1. 





Lbs. Coal 


Lbs. Coal 

burned per 

Hour per 

sq. ft. of 

Grate. 




Lbs. Coal 






burned per 




burned per 


Lbs. Coal 


Height 
in Feet. 


Hour per 


Height in 


Hour per 


burned per 


sq. ft. of 


Feet. 


sq. ft. Sec- 


Hour per 




Section of 




tion of 


sq. ft. Grate. 




Chimney. 




Chimney. 




25 


68 


8.5 


70 


126 


15.8 


30 


76 


9.5 


75 


131 


16.4 


35 


84 


10.5 


80 


135 


16.9 


40 


93 


11.6 


85 


139 


17.4 


45 


99 


12.4 


90 


144 


18.0 


50 


105 


13.1 


95 


148 


18.5 


55 


111 


13.8 


100 


152 


19.0 


60 


116 


14.5 


105 


156 


19.5 


65 


121 


15.1 


110 


160 


20.0 



CHIMNEYS. 



1343 



Dimensions and Cost of Brick Chimneys. 

(Buckley.) 



6 




o 


pj 




J4+1 








2 






2-3 


<v . 




u 
o 


fa 


fa 




Outside Wall. 


»h bo 


11 




tt o 


w 


S § 
Q 


Outside 

sions, B 

Squai 




fa - 

*, be 


O c8 

^ S 

op 
Ofa 


2s 

p2 

HO 


is 

< 


No. 
Brick. 


Cost® 

$14 per 

M. 


85 


80 


25 in. 


7 ft. 5 in. 


32,000 


$ 448.00 


$ 60.00 


$ 90.00 


$ 598.00 


135 


90 


30 in. 


8 " 3 " 


40,000 


560.00 


82.00 


144.00 


786.00 


200 


100 


35 in. 


9 " 10 " 


65,000 


910.00 


118.00 


198.00 


1,226.00 


300 


110 


43 in. 


10 " 2 " 


75,000 


1,050.00 


190.00 


252.00 


1,492.00 


450 


120 


51 in. 


11 V 2 " 


87,000 


1,218.00 


261.00 


306.00 


1,785.00 


750 


130 


61 in. 


12 " 6 « 


131,000 


1,834.00 


334.00 


360.00 


2.528.00 


1000 


140 


74 in. 


13 "11 M 


151,000 


2,114.00 


432.00 


414.00 


3,060.00 


1650 


150 


88 in. 


15 «!« 1 " 


200,000 


2,800.00 


482.00 


468.00 


3,750.00 


2500 


160 


110 in. 


17 " 10 " 


275,000 


3,850.00 


720.00 


525.00 


5,095.00 



Steel Mate Chimneys have long been used in the iron and coal re- 
gions, but have only recently come into use in the East, except in the old 
style thin sheet iron guyed stack, which, lasts but a short time. 

Many of the manufacturers of steel structures are now erecting very sub- 
stantial steel-plate stacks lined with tire bricks, that are of artistic outline, 
strong, and when kept well painted are durable and need no guys, as they 
are spread at the base, and bolted to a heavy foundation. They are usually 
designed to stand a wind pressure of 50 lbs. per square foot. 

Sizes of Foundation* for Steel Chimney. 

(Selected from Circular of Philadelphia Engineering Works.) 
Half-Lined Chimneys. 



Diameter, clear, feet . . , 

Height, feet 

Least diameter foundation . 
Least depth foundation . . 

Height, feet 

Least diameter foundation . 
Least depth foundation . . 



3 


4 


5 


s 


7 


9 


11 


100 


100 


150 


150 


150 


150 


150 


15'9" 


16'4" 


20'4" 


21'10 / 


22'7" 


23'8'- 


24'8" 


6' 


6' 


9' 


8' 


9 / 


W 


W 




125 


200 


200 


250 


275 


300 




18'5" 


23'8" 


25' 


29'8'' 


33'6" 


36' 


. . . 


V 


W 


W 


12' 


12'" 


14' 



Brick liining* for Steel Stacks. 

Allowing If inches air space between stack and lining : 

Bricks 8| X 4 X 2 inches, laid without mortar ; 
Lining 8t inches (one brick) thick ; 

Number of bricks per foot in diameter of stack, and per foot of height 
= 47. 

Allowing 1 inch air space between stack and lining : 

Bricks 8| X 4 X 2 inches, laid without mortar ; 
Lining 4 inches (one brick) thick ; 

Number of bricks per foot in diameter of stack, and per foot of height 
= 25. 



1344 



STEAM. 



Dimensions and Cost of Iron Stacks. (Guyed.) 
(Buckley.) 



Horse- 


Height, 


Diameter, 


Number of 


Price Stack 


Price 


Power. 


Feet. 


Inches. 


Iron. 


Complete. 


per Foot. 


25 


40 


16 


12 and 14 


$ 61.00 


$ 1.52 




40 


18 


12 and 14 


71.00 


1.78 




50 


18 


12 and 14 


84.00 


1.68 


75 


50 


20 


12 and 14 


87.00 


1.75 




50 


26 


12 and 14 


105.00 


2.10 




60 


22 


12 and 14 


111.00 


1.85 


100 


60 


24 


12 and 14 


125.00 


2.08 




60 


26 


12 and 14 


133.00 


2.22 




60 


28 


12 and 14 


148.00 


2.45 


125 


60 


28 


10 and 12 


190.00 


3.18 




60 


32 


10 and 12 


203.00 


3.38 


150 


60 


34 


12 and 14 


165.00 


2.75 


200 


60 


36 


10 and 12 


215.00 


3.58 


225 


60 


38 


10 and 12 


228.00 


3.80 


250 


60 


42 


10 and 11 


257.00 


4.28 


300 


60 


46 


10 and 12 


286.00 


4.76 


400 


60 


52 


10 and 12 


340.00 


5.66 



For general details of construction of the various types of chimneys used 
in the U. S. the reader is referred to " Chimney Design and Theory," by 
W. Wallace Christie, published by D. Van Nostrand Co. 

Blowers for forced Draught.* 

Forced Draught Capacity Table for Blowers. 

Temperature air, 62 degrees F.; 18 lbs. air per 1 lb. coal ; 34.5 lbs. water 
per H.P.; barometer, 29.92 ; 234 cubic ft. per 1 lb. coal; evaporation, 6.9 lbs. 
water per 1 lb. coal; pressure, 1* ounces; 5 lbs. coal per H.P. hour. 



u 
9 

O 

s 

■H 

O 
© 

s 

51 


% 

A . 

©*© 

©M 

2 

08 

s 




o 

<- . 

s 


O 
® % 

S s 
SO 

s 


u . 

O © 

<h £ 

Y © 

QQ 


Capacity Blower, 

Cu. Ft. per Min., 

Temp. 62° F. 


Lbs. Coal per Hour 

234 Cu. Ft. 

Air per Lb. Coal. 


H.P. Boiler Capa- 
city 5 Lbs. Coal 
per H.P. Hour. 


Evaporation 

per Hour 34.5 Lbs. 

Water per H.P. 


Brake H.P. 

to drive Blower 

at Speed. 


l 


8J 


2 


4| 


4f 


3300 


348 


90 


18 


620 


.35 


2 


10i 


2f 


5* 


5§ 


2650 


512 


131 


26 


896 


.52 


3 


12 


3i 


6* 


6| 


2320 


711 


182 


36 


1240 


.73 


4 


15* 


4| 


8 


8* 


1800 


1210 


310 


62 


2140 


1.24 


5 


19 


5* 


10 


10* 


1470 


1830 


468 


93 


3210 


1.87 


6 


22* 


6* 


12 


12* 


1240 


2600 


666 


133 


4590 


2.66 


7 


26 


1 


14 


14* 


1075 


3420 


875 


175 


6030 


3.50 


8 


29* 


n 


16J 


950 


4130 


1055 


211 


7280 


4.54 


9 


33 


9* 


18i 


845 


5580 


1425 


285 


9820 


5.72 



(American Blower Co.) 



* From "Furnace Draft; Its Production, by Mechanical Methods" 
— W. W. Christie. 



FUEL. 



1345 



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1346 



STEAM. 



The effect of the temperature of the gases, on the power required to 
operate a fan, is shown very clearly by the following : 

Effect of Temperature of Oases on fan Load. 

Induced Draft. 



Draft in inches of water 

Temperature of gases at fan, degree F. . 
Speed of fan, revolution per minute . . 
Current required by fan motor — amperes 
Current generated by plant — amperes . 
Proportion used by fan — per cent . . . 
Boiler H.P. developed ........ 



1 


2 


0.42 


0.46 


199.6 


162.5 


154. 


179. 


10.3 


13.3 


896. 


1236. 


1.15 


1.17 


521.7 


600.6 



0.24 
330. 
230. 
20.4 
960. 

2.08 
439.2 



The blower used was an American Blower Co.'s centrifugal fan with 
28 X 84 inch wheel. 

The third test, gases 130 deg. hotter than first, requires about 100 per cent 
more power, and yet the boiler evaporation is about 20 per cent less than in 
the first test. — Curtis Pub. Co., by Davis & Griggs. 

The cost of the above Mechanical Draft outfit (2 fans), including motors, 
was $5.53 per boiler H.P. 

All of the blower methods of draft production must be considered in con- 
nection with, and be planned with especial regard to, the quantity of fuel to 
be burned in a given time, and the amount of air needed for the complete 
combustion of the fuel, which air must necessarily pass through the blowers. 

18 to 25 lbs. of coal per square foot of grate per hour is all the coal that 
should or can be burned with economy under natural draft; a greater amount 
necessitates forced draft. 

Another thing which should not be lost sight of in connection with the 
burning of small coals, is the unburnt coal falling through the grate, which 
in the case of anthracite culm has reached 58 per cent (found in the ashes). 
Kinds and Ingredients of fuels. 

The substances which we call fuel are : wood, charcoal, coal, coke, peat, 
certain combustible gases, and liquid hydrocarbons. 

Combustion or burning is a rapid chemical combination. 

The imperfect combustion of carbon produces carbonic oxide (CO), and 
carbonic acid or dioxide (C0 2 ). 

From certain experiments and comparisons Rankine concludes " that the 
total heat of combustion of any compound of hydrogen and carbon is nearly 
the sum of the quantities of heat which the hydrogen and carbon contained 
in it would produce separately by their combustion (CH 4 — marsh gas or 
fire-damp excepted)." 

In computing the total heat of combustion of a compound, it is conven- 
ient to substitute for the hydrogen a quantity of carbon which would give 
the same quantity of heat ; this is accomplished by multiplying the weight 
of hydrogen by 62032 ^- 14500 = 4.28. 

From experiments by Dulong, Despretz, and others, u when hydrogen and 
oxygen exist in a compound in the proper proportion to form water (by 
weight nearly 1 part H to 8 parts O), these constituents have no effect on 
the total heat of combustion. 

" If hydrogen exists in a greater proportion, take into the heat account 
only the surplus." 

Dulong's formula for the total heat of combustion of carbon, hydrogen, 
oxygen, and sulphur, where C,H,0, and S refer to the fractions of one 
pound of the compound, the remainder being ash, etc. Let h ±z total heat 
of combustion in B.T.U. per pound of compound. 

h = 14660 C-f- 62000 (h— ^\ + 4000 #. (A.S.M.E. Trans, vol. xxi.) 

Rankine says : " The ingredients of every kind of fuel commonly used may 
be thus classed : (1) Fixed or free carbon, which is left in the form of char- 
coal or coke after the volatile ingredients of the fuel have been distilled 
away. These ingredients burn either wholly in the solid state, or part in 
the solid state and part in the gaseous state, the latter part being first 
dissolved by previously formed carbonic acid. 

"(2) Hydrocarbons, such as olefiant gas, pitch, tar, naphtha, etc., all of 
which must pass into the gaseous state before being burned. 



FUEL. 



1347 



" If mixed on their first issuing from amongst the burning carbon with a 
large quantity of air, these inflammable gases are completely burned with 
a transparent blue flame, producing carbonic acid and steam. When raised 
to a red heat, or thereabouts, before being mixed with a sufficient quantity 
of air for perfect combustion, they disengage carbon in tine powder, and 
pass to the condition partly of marsh gas, and partly of free hydrogen ; and 
the higher the temperature, the greater is the proportion of carbon thus 
disengaged. 

" If the disengaged carbon is cooled below the temperature of ignition be- 
fore coming in contact with oxygen, it constitutes, while floating in the gas, 
smoke, and when deposited on solid bodies, soot. 

" But if the disengaged carbon is maintained at the temperature of ignition, 
and supplied with oxygen suihcient for its combustion, it burns while float- 
ing in the inflammable gas, and forms red, yellow, or white flame. The 
flame from fuel is the larger the more slowly its combustion is effected. 

" (3) Oxygen or hydrogen either actually forming water, or existing in com- 
bination with the other constituents in the proportions which form water. 
Such quantities of oxygen and hydrogen are to be left out of account in de- 
termining the heat generated by the combustion. If the quantity of water 
actually or virtually present in each pound of fuel is so great as to make its 
latent heat of evaporation worth considering, that heat is to be deducted 
from the total heat of combustion of the fuel. The presence of water or its 
constituents in fuel promotes the formation of smoke, or of the carbona- 
ceous flame, which is ignited smoke, as the case may be, probably by 
mechanically sweeping along fine particles of carbon. 

" (4) Nitrogen, either free or in combination with other constituents. This 
substance is simply inert. 

" (5) Sulphuret of iron, which exists in coal and is detrimental, as tending to 
cause spontaneous combustion. 

" (6) Other mineral compounds of various kinds, which are also inert, and 
form the ash left after complete combustion of the fuel, and also the clinker 
or glassy material produced by fusion of the ash, which tends to «hoke the 
grate." 

Total Heat of Combustion of Fu«l«. (D. K. Clark.) 

The following table gives the total heat evolved by combustibles and their 
equivalent evaporative power, with the weight of oxygen and volume of air 
chemically consumed. 



Combustibles. 



s 

I III 

US S M 



Quantity of Air 
Consumed per 
Pound of C ora- 
bustible. 



lbs. 



lbs. 



Cu. Ft. 
at 62°F. 



02 X> 

S fl 

O oh 
o£« 

cS^ © 

©^3 

S3 0; h 

n S M 
H 



rA 



O 



S§1 

5^2 



3 ° p — 



Hydrogen 

Carbon making CO . . . . . 

Carbon making C0 2 

Carbonic oxide . 

Light Carbureted Hydrogen . . 

Olefiant Gas 

Coal (adopted average desiccated) 
Coke(adopted average desiccated) 

Lignite, perfect 

Wood, desiccated 

Wood, 25 per cent moisture . . 

Petroleum . . 

Petroleum oils . . . c . . . 
Sulphur 



8.0 

1.33 

2.66 

0.57 

4.00 

3.43 

2.45 

2.49 

2.04 

1.40 

1.05 

3.29 

4.12 

1.00 



34.8 
5.8 
11.6 
2.48 
17.4 
15.0 
10.7 
10.81 
8.85 
6.09 
4.57 
14.33 
17.93 
4 35 



457 

76 

152 

33 

229 

196 

140 

142 

116 

80 

60 

188 

235 

57 



62000 

4452 
14500 

4325 
23513 
21343 
14700 
13548 
13108 
10974 

7951 
20411 
27531 

4000 



64.20 

4.61 
15.00 

4.48 
24.34 
22.09 
15.22 
14.0? 
13.51 
11.36 

8.20 
21.13 
28.50 

4.17 



1348 



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FUEL. 



1349 



Temperature of fire. 



By reference to the table of combustibles, it will be seen that the temper- 
ature of the fire is nearly the same for all kinds of combustibles, under sim- 
ilar conditions. If the temperature is known, the conditions of combustion 
may be inferred. The following table, from M. Pouillet, will enable the 
temperature to be judged by the appearance of the fire : 



Appearance. 


Temp. F. 


Appearance. 


Temp. F. 


Red, just visible . . 

" dull 

" cherry, dull . . 
" " full . . 
" " clear . 


977° 
1290 
1470 
1650 
1830 


Orange, deep . . . 

" clear . . . 

White heat .... 

" bright . . . 

" dazzling . . 


2010 
2190 
2370 
2550 
2730 



To determine Temperature oy Fusion of Metals, etc. 



Substance. 


Tern. F. 


Metal. 


Tern. F. 


Metal. 


Tern. F. 


Tallow . . . 
Spermaceti . 
Wax, white . 
Sulphur . . 
Tin ... . 


92° 
120 
154 
239 
455 


Bismuth . 
Lead . . . 
Zinc . . . 
Antimony . 
Brass . . 


518° 
630 
793 
810 
1650 


Silver, pure . . 
Gold, coin . . 
Iron, cast, med. 
Steel .... 
Wrought iron . 


1830° 

2156 

2010 

2550 

2910 



American Woods. 



Kind of Wood. 



Hickory — Shell bark. 
White oak .... 
Hickory — Red heart 
Southern pine ... 

Red oak 

Beech 

Hard maple . . . 
Virginia pine . . . 

Spruce 

New Jersey pine . . 

Yellow pine . . . , 
White pine . . . . 



Weight 
per Cord. 



4469 
3821 
3705 
3375 
3254 
3126 
2878 
2680 
2325 
2137 

1904 
1868 



Value in Tons Coal. 



Anthracite Bituminous 



.52 

.504 

.459 

.443 

.425 

.391 

.364 

.316 

.291 

.259 
.254 



.563 

.481 

.467 

.425 

.41 

.394 

.363 

.338 

.293 



.24 
.235 



1350 



STEAM. 
American Coals. 



State. 



Coal. 
Kind of Coal. 



Pennsylvania. Anthracite 



Cannel . . . 
Connellsville . 



Kentucky. 



Illinois. 



Indiana. 



Maryland. 

Arkansas. 
Colorado. 



Semi-bituminous 
Stone's Gas . 
Youghiogheny 
Brown . . . 
Coking . . , 

Cannel . . . 



Lignite . . 
Bureau Co. 
Mercer Co.. 



Montauk . . 
Block . , . 
Coking . . „ 
Cannel . . . 
Cumberland . 



Lignite . 



Texas. " 

Washington Ter. " 

Pennsylvania. Petroleum < 



Per Cent 

of 

Ash. 



3.49 
6.13 
2.90 
15.02 
6.50 

10.70 
5.00 
5.60 
9.50 
2.75 

2.00 
14.80 
7.00 
5.20 
5.60 

5.50 
2.50 
5.66 
6.00 
13.88 

5.00 
9.25 
4.50 
4.50 
3.40 



Theoretical Value. 



In Heat 
Units. 



14,199 
13,535 
14,221 
13,143 
13,368 

13,155 
14,021 
14,265 
12,324 
14,391 

15,198 
13,360 
9,326 
13,025 
13,123 

12,659 
13,588 
14,146 
13,097 
12,226 

9,215 
13,562 
13,866 
12,962 
11,551 

20,746 



Pounds of 
Water 
Evap. 



14.70 
14.01 
14.72 
13.60 
13.84 

13.62 
14.51 
14.76 
12.75 
14.89 

16.76 
13.84 
9.65 
13.48 
13.58 

13.10 
14.38 
14,64 
13.56 
12.65 

9.54 
14.04 
14.35 
13.41 
11.96 

2147 



The weight of solid coal varies from 80 lbs. to 100 lbs. per cubic foot. 



Tbe Heating- Value of Coals. 



On page 1351 are given the results (Sibley, Journal of Engineering) of some 
experiments made at Cornell University with a coal calorimeter devised by 
Prof. R. C. Carpenter. It consists of two cylindrical chambers, in the inner 
one of which the sample of coal is burned in oxygen. The heated gases pass 
through a coiled copper tube about 10 feet long contained in the outer cham- 
ber. The coil is surrounded by water which expands, the expansion being 
measured in a finely graduated glass tube, thus giving the heat units in the 
coal. The calorimeter is calibrated by burning in it pure carbon. Follow- 
ing are the tables : 



FUEL. 



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1352 



STEAM. 



Proximate Analysis of Coal. 

(Power.) 



Designation of Coal. 



ANTHRACITE. 

Beaver Meadow, Penn 

Peach Mountain, Penn 

Lackawanna, Penn 

Lehigh, Penn 

Welsh, Wales 

SEMI- ANTHRACITE . 

Natural Coke, Virginia 

Cardiff, Wales 

Lycoming Creek, Penn 

Arkansas, No. 16 Geol. Survey .... 

SEMI-BITUMINOUS. 

Blossburg, Penn 

Mexican 

Fort Smith, Arkansas 

Cliff, New South Wales, Australia . . 
Skagit River, State of Washington . . 

Cumberland, Maryland 

Cambria County, Penn 

Mount Kembla, New South Wales, A us. 

Fire Creek, West Virginia 

Arkansas, No. 12 Geol. Survey .... 

BITUMINOUS. 

Wilkeson, Pierce County, Washington . 

Cowlitz, Washington 

New River, West Virginia 

Pictou, Nova Scotia 

Big Muddy, Illinois 

Bellingham Bay, Washington .... 

Midlothian, Virginia 

Connellsville, Penn 

Illinois, Average 

Carbon Hill, Washington 

Clover Hill, Virginia 

Wellington. Vancouver Island, B.C. . . 

Franklin, Washington 

Rocky Mountains 

Newcastle, England 

Mokihinui, Westport, New Zealand . . 
Brunner Mine, Greymouth, New Zealand 

Pittsburg, Penn 

Nanaimo, Vancouver Island, B.C. . . . 

Hocking Valley, Ohio 

Pleasant Valley, Utah ....... 

Kentucky 

Ellensburg, Washington 

Olympic Mountains, Washington . . . 

Scotch, Scotland 

Roslyn, Washington 

Cook's Inlet, Alaska 

Kootznahoo Inlet, Admiralty I., Alaska 

Liverpool, England 

Calispel, Washington 

Carbonado, Washington 

Upper Yakima, Washington 

Methow, Washington 



0-,^ 



1.5 

1.9 

2.12 

3.01 

1.2 

1.12 

1.25 

.67 

1.35 

1.34 

1.0 

1.07 

.85 
1.19 

.97 
2.46 
1.2 

.74 

.88 

1.33 
1.16 
.67 
2.57 
7.12 
3.98 
2.46 
1.26 
8.93 
2.16 
1.34 
2.15 
3.5 
7.55 
1.5 
3.96 
1.59 
1.7 
2.25 
6.95 
5.43 
2. 
2. 
5.1 
3.01 
3.1 
1.25 
3.74 



2.39 
1.8 
1.2 
2.5 



o *3 



2.38 
2.96 
3.91 
3.28 
6.25 

12.44 
12.85 
13.84 
14.93 

14.78 

14.86 

17.2 

17.7 

18.8 

19.87 

20.52 

20.93 

22.42 

24.66 

25.88 

26.12 

26.64 

27.83 

29.5 

29.54 

29.86 

30.10 

30.14 

31.73 

32.21 

34.15 

34.27 

34.65 

34.7 

34.94 

35.68 

36. 

36.05 

36.15 

37.73 

37.89 

39.1 

39.15 

39.19 

39.7 

39.87 

37.02 

39.96 

41.18 

42.27 

42.47 

43.71 



^d 




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< 


88.94 


7.11 


89.02 


6.13 


87.74 


6.35 


88.15 


5.56 


88. 


4.55 


75.08 


11.38 


81.9 


4. 


71.53 


13.96 


74.06 


9.66 


73.11 


10.77 


55.7 


28.44 


73.05 


8.68 


71.8 


9.65 


71.66 


8.35 


72.26 


6.12 


69.37 


9.15 


66.96 


10.91 


75.5 


.8 


58.2 


16.26 


66.75 


6.04 


61.9 


10.69 


70.66 


1.53 


56.98 


13.39 


54.64 


8.74 


59.9 


6. 


53.01 


14.74 


59.61 


8.23 


45.93 


15. 


55.8 


10.31 


56.83 


10.13 


54.85 


8.85 


54.23 


8. 


42.85 


14.95 


59.3 


4.5 


57.92 


3.18 


56.62 


6.11 


55. 


7.3 


51.95 


9.75 


51.3 


5.56 


49.40 


7.44 


56.01 


4.1 


54.4 


3.4 


47.01 


7.77 


48.81 


9.34 


52.65 


4.55 


49.89 


7.82 


45.15 


14.09 


54.9 


4.62 


42.92 


13.21 


52.11 


3.82 


52.21 


4.12 


49.27 


4.26 



FUEL. 



1353 



l»roxiniate Analysis of Coal— Continued, 



Designation of Coal. 


w 03 


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3 


Newcastle, King County, Washington . 


2.12 


46.7 


43.9 


7.15 


.13 


Black Diamond, King County ,Washington 


3.11 


47.19 


45.11 


4.58 


.01 


Black Diamond, Mt. Diablo, California . 


14.69 


33.89 


46.84 


4.58 




LIGNITES. 












Otago (Kaitangata Cr.), New Zealand . 


k 19.61 


37.25 


39.41 


3.73 




Oilman, Washington 


4.8 


47.07 


37.19 


10.06 


.88 


Coos Bay (Newport Mine), Oregon . . 


15.45 


41.55 


34.95 


8.05 


2.53 


Alaska 


14.6 


44.85 


31.2 


9.35 


1.15 


Huron, Fresno County, California 


11.7 


51.73 


19.63 


16.94 


2.73 


lone, Amador County, California . . . 


42.58 34.88 


17.42 


5.12 


Trace. 



Analysis of Coke. 

(From report of John R. Procter, Kentucky Geologi cal Survey.) 



Where Made. 


Fixed 
Carbon 


Ash. 


Sul- 
phur. 


Connellsville, Pa. (Average of 3 samples) . . . 
Chattanocga, Tenn. " "4 " ... 
Birmingham, Ala. " ** 4 " ... 
Pocahontas, Va. " "3 " ... 
New River, W. Va. " " 8 " ... 
Big Stone Gap, Ky. " " 7 " ... 


88.96 
80.51 
87.29 
92.53 
92.38 
93.23 


9.74 
16.34 
10.54 
5.74 
7.21 
5.69 


0.810 
1.505 
1.195 
0.597 
0,562 
0.749 



Space Required to Stow a Ton (2240 lb*.) of Various 
Kind's of Coal. 

ANTHRACITE. 

Welsh, Wales 39 cubic feet. 

Peach Mountain, Penn 41.6 " " 

Beaver Meadow, Penn 40.2 " " 

Lehigh, Penn 40.5 " " 

Lackawanna, Penn 45.8 " " 

SEMI- ANT HB ACITE . 

Cardiff, Whales 38.3 cubic feet. 

Natural Coke, Virginia 50.2 " " 

SEMI-BITUMINOUS. 

Cumberland, Virginia 41.7 cubic feet. 

Blossburgh, Penn 42.2 " " 

Mt. Kembla, Australia 37.7 " " 

Mexican 36.7 " ■■ 

BITUMINOUS. 

New River, Virginia 46 cubic feet. . 

Wellington, Vancouver Island, B.C 41.8 " M 

Midlothian, Virginia 41.4 " " 

Newcastle, England 44 •• " 

Pictou, Nova Scotia 45 " " 

Scotch Splint, Fordel 40.7 •■ " 

Pleasant Valley, Utah 42.3 " " 

Sydney, N. S. W., Australia 47.2 " " 

Takasima, Japan 46.4 " " 

Pittsburgh, Penn 47.8 " " 

Liverpool, England 46.7 " " 

Scotch, Dalkeith 43.8 " M 

Carbon Hill, Washington 36.9 « " 

Clover Hill, Virginia 49.2 " " 

Rocky Mountain 41.2 " " 

LIGNITE. 

Alaska 41.8 cubic feet. 

WOOD. 

Dry pine wood 107 cubic feet. 

Coke. — Coke from ovens, preferred to gas coke as fuel, weighs with 
few exceptions about 40 lbs. per bushel. Light coke will weigh 33 to 38 lbs- 
Heavy coke, 42 to 50 lbs. 



1354 



STEAM. 



Weigrnts of Various Sizes of Coal. 





Lbs. per 
cubic 
foot. 


Cu. foot 
per ton 
of 2000 lbs 


Lehigh buckwheat 


54.04 
56.85 
55.52 
57.25 
57.74 
55.26 
58.26 
53.18 
58.15 
56.07 
56.88 
56.33 
46.48 
47.22 
49.30 
43.85 
48.07 
49.18 
26.30 


37.01 


broken 


35.18 


cupola '. 


36.02 


" dust 


34.93 


" egg 


34.63 


lump 

" nut 


36.19 
34.32 


" pea 


37.60 


stove 


34.39 


Free burning egg 


35.67 


nut 

" " stove 

Pittsburgh 


35.16 
35.50 
43.03 


Illinois 


42.35 


Hocking 


40.56 


Indiana Block 


46.51 


Erie 


41.61 


Ohio Cannel 


40.66 


Connellsville coke . . 


76.04 







Weights per Cubic Foot, Coal and Coke. 




Pounds 
per cu. ft. 



Anth. coal market sizes, loose 

Anth. coal market sizes, moderately shaken . . 
Anth. coal market sizes, heaped bushels 

loose 77-83 lbs. . . 

Bit. coals, broken — loose 

Bit. coals, broken — moderately shaken . . . 
Bit. coals, broken — heaped bushels 70-78 lbs. 

Dry coke 

Dry coke, heaped bushel, (av. 38 lbs.) 35-42 lbs. 



52-56 
56-60 



47-52 
51-56 



23-32 



Sizing* Tests — Anthracite. 

Through round holes, punched in plates. 

Chestnut through lh over £ 

Pea " | •• T % 

Buckwheat " t% " i 

Rice V I " A 

galley .••>.!'.. " i 3 6 '.' & 

Culm ............. " jft 



FUEL. 



1355 



Relative Values of Coals and How to Burn Them. 

(By Jay M. Wliitham.) 

Given boilers and chimney operating under natural draft and having 
certain sizes and dimensions, the capacities measured in steam output, 
which can he produced therewith, when using good grades of these coals, 
are as follows : 



Semi-bituminous coal (8 to 10 per cent ash) . . . 
No. 1 buckwheat anthracite (18 to 22 per cent ash 

in use) 

No. 2 buckwheat anthracite, or rice (18 to 22 per 

cent ash in use) 



Per cent. 



100 
80 
68 



It is more than likely that the percentage of ash and refuse obtained in 
service with Nos. 1 and 2 buckwheat will exceed the 18 to 22 per cent above 
noted, while it is equally probable that with soft coal the percentage will 
not exceed from 8 to 10 per cent. 

It is, of course, a simple matter to increase the combustion of the small 
sizes of anthracite by the use of a fan or a steam blast. A fan blast uses 
from 2£ to 3 per cent of the steam produced in the boilers, while the steam 
blast, used for injecting air into a closed ash-pit, consumes from 7£ to 12 
per cent of the steam produced by the boilers, and seldom operates under 
less than 10 per cent. Hence, in making any estimates as to the relative 
costs of operating with these fuels, these deductions must be made if an 
artificial draft must be used, in order to get net comparative results. 

Given semi-bituminous and small-sized anthracite coals of the ash com- 
positions noted above, my experience has shown that the relation between 
the costs of operating the plant with these coals, under natural draft, to 
produce a given output, are : 





Per Ton. 


Semi-bituminous coal 


$1.33 


No. 1 buckwheat coal 


1.00 


No. 2 buckwheat (rice) coal 


.83 


• 





Paying these prices, the costs for power under natural draft are the 
same, ho matter which coal is used, provided the cost of removing ashes 
is ignored. 

If the anthracite grades have to be burned with blasts, the relative prices 
which one can afford to pay for producing a given quantity of steam are 
as follows : 



Draft. 


Natural. 


Fan Blast. 


Steam Blast. 


Semi-bituminous .... 
No. 1 buckwheat ..... 
No. 2 buckwheat (rice) . . . 


$1.33 

::: 


$0.97 

.82| 


$0.90 
.76£ 



Semi-bituminous coals are burned to advantage only by exercising great 
care in the handling of fires, and by the firemen exerting themselves 
beyond what is necessary when burning buckwheat and rice anthracite 
grades. 



1356 



STEAM. 



Wood as Fuel. 

Green wood contains from 30 to 50 per cent of moisture. After about a 
year in open air the moisture is 20 to 25 per cent. 

The woods of various trees are nearly identical in chemical composition, 
which is practically as follows, showing the composition of perfectly dry 
wood, and of ordinary firewood holding hygroscopic moisture : 



Carbon . . 
Hydrogen 
Oxygen 
Nitrogen , 
Ash . . 



Hygrometric water 



Desiccated Wood. 

50 per cent 

6 per cent 

41 per cent 

1 per cent 

2 per cent 
100 per cent 



Ordinary Firewood. 
37.5 per cent 
4.5 per cent 
30.75 per cent 
0.75 per cent 
1.5 per cent 
75.0 per cent 
25.0 per cent 
100.0 
Some of the pines and others of the coniferous family contain hydrocar- 
bons (turpentine). Ash varies in American woods from .03 per cent to 1.20 
per cent. 

In steam boiler tests wood is assumed as 0.4 the value of the same weight of 
coal. 

The fuel value of the same weights of wood of all kinds is practically the 
same ; and it is important that the wood be dry. 



Weig-nt of Wood* per Cord. 






Weighs per 
Cord, Lbs. 


Equal in value to Coal, 
in Lbs. 


Average pine 

Poplar, chestnut, elm 

Beech, red and black oak .... 
White oak 


2000 
2350 
3250 
3850 
4500 




800 to 925 
940 to 1050 
1300 to 1450 
1540 to 1715 


Hickory and hard maple .... 


1800 to 2000 



A cord of wood = 4x4x8= 128 cubic feet. About 56 per cent is solid 
wood, and 44 per cent spaces. 

liquid Fuels. • 

Petroleum is a hydrocarbon liquid which is found in abundance in Amer- 
ica and Europe. According to the analysis of M. Sainte-Claire Deville, the 
composition of 15 petroleums from different sources was found to be practi- 
cally the same. The average specific gravity was .870. The extreme and the 
average elementary compositions were as follows : 



Chemical Composition of Petroleum. 



Carbon 82.0 to 87.1 per cent. 

Hydrogen 11.2 to 14.8 per cent. 

Oxygen 0.5 to 5.7 per cent. 



Average, 84.7 per cent. 
Average, 13.1 per cent. 
Average, 2.2 per cent. 
100.0 
The total heating and evaporative powers of one pound of petroleum hav- 
ing this average composition are as follows : 

Total heating power = 145 [84.7 + (4.28 x 13.1)] = 20411 units. 
Evaporative power : evaporating at 212°, water supplied at 62° = 18.29 lbs. 
Evaporative power : evaporating at 212°, water supplied at 212° = 21.13 lbs. 
Petroleum oils are obtained in great variety by distillation from petro- 
leum. They are compounds of carbon and hydrogen, ranging from C 10 H 24 
to C 32 H 64 ; or, in weight ; 



FUEL. 



1357 



Chemical Composition of Petroleum Oils. 

-nw™ (71.42 Carbon ) ^ i 73.77 Carbon . . . 72.60 
*rom { 28.58 Hydrogen f lo \ 26.23 Hydrogen . . 27.40 



100.00 



100.00 



100.00 



The specific gravity ranges from .628 to .792. The boiling point ranges 
from 86° to 495° F. The total heating power ranges from 28087 to 26975 units 
of heat ; equivalent t£> the evaporation, at 212°, of from 25.17 to 24.17 lbs. 
of water supplied at 62°, or from 29.08 lbs. to 27.92 lbs. of water supplied 
at 212°. 

Puraacei for the combustion of oil fuel need not be as large as when 
burning coal, as the latter, being solid matter, requires more time for de- 
composition, and the elimination of the products and supporters of com- 
bustion. Coal fuel requires a large fire chamber and the means for the 
introduction of air beneath the grate-bars to aid combustion. Compared 
with oil, the combustion of coal is tardy, and requires some aid by way of 
a strong draft. Oil having no ash or refuse, when properly burned, requires 
much less space for combustion, for the reason that, being a liquid, and the 
compound of gases that are highly inflammable when united in proper pro- 
portions, it gives off heat with the utmost rapidity, and at the point of igni- 
tion is all ready for consumption. 

Prof. J. E. Denton has made a number of boiler evaporative tests, using 
oil for fuel. In the following table the results of tests where various fuels 
were used are brought together, and interesting comparisons are made be- 
tween the cost of coal and cost of oil. See " Power," Feb., 1902. 

Gaseous !Fuels. — Mr. Emerson McMillin (Am. Gas. Lt. Asso., 1887) 
made an exhaustive investigation of the subject of fuel gas ; he states that 
the relative values of these gases, considering that of natural gas as of unit 
value, are: 



By Volume. 



Natural gas . 
Coal gas . . 
Water gas 
Producer gas 




The water gas rated in the above table is the gas obtained in the decom- 
position of steam by incandescent carbon, and does not attempt to fix the 
calorific value of illuminating water gas, which may be carbureted so as to 
exceed, when compared by volume, the value of coal gas. 



Composition of Gases. 



Hydrogen . . . 
Marsh gas . . 
Carbonic oxide 
defiant gas . . 
Carbonic acid . 
Nitrogen . . . 
Oxygen . . . 
Water vapor 
Sulphydric acid 



Natural 
Gas. 



2.18 
92.60 
0.50 
0.31 
0.26 
3.61 
0.34 
0.00 
0.20 

100.00 



Volume. 



Coal 

Gas. 



46.00 
40.00 
6.00 
4.00 
0.50 
1.50 
0.50 
1.50 

100.00 



Water 
Gas. 



45.00 
2.00 

45.00 
0.00 
4.00 
2.00 
0.50 
1.50 

100.00 



Producer 
Gas. 



6.00 
3.00 

23.50 
0.00 
1.50 

65.00 
0.00 
1.00 

"lOO.OO 



1358 



STEAM. 



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FUEL. 1359 



Mechanical Stoking*. 

In boiler installations that can be conveniently handled by one man it is 
doubtful if we can improve on the best hand tiring; but where good firemen 
are scarce, or the installation is of considerable size, it is probable that 
the use of some form of mechanical stoker will result in economy, and 
especially in the prevention of large quantities of smoke, as the combustion 
is gradual and more nearly perfect. 

The types may perhaps be limited to three : the straight feed, as the Mur- 
phy, Honey, Wilkinson, and Brightman ; the under-feed of which the 
11 American " is a good representative ; and the chain stoker, by Coxe and 
the B. & W. Co. 

Mechanical draught is generally used with the two last-mentioned types, 
and sometimes with the first. 

Mr. Eckley B. Coxe developed the chain stoker in the most scientific man- 
ner for the use of the cheap coals of the anthracite region. 

The advantages and disadvantages of mechanical stokers are stated 
by Mr. J. M. Whitham (Trans. A.S.M.E., vol. xvii. p. 558) to be as follows : 
Advantages. 1. Adaptability to the burning of the cheapest grades of fuel. 
2. A 40 per cent labor saving in plants of 500 or more h. p., when provided with 
coal-handling machinery. 3. Economy in combustion, even under forced 
firing, with proper management. 4. Constancy and uniformity of furnace 
conditions, the fires being clean at all times, and responding to sudden de- 
mands made for power. This should result in prolonged life of boilers. 
5. SmokelessnesSc Disadvantages. 1. High first cost, varying from $25 to 
$40 per square foot of grate area. 2. High cost of repairs per year, which, 
with some stokers, is as much as $5 per square foot. 3. The dependence of 
the power-plant upon the stoker engine's working. 4. Steam cost of run- 
ning the stoker engine, which is from £ to § of 1 per cent of the steam generated. 
This is about $50 a year on a 10-hour basis for 1000 h. p., where fuel is $2 per 
ton. 5. Cost of steam used for a steam blast, or for driving a fan blast, 
whenever either is used. This, for a steam blast, is from 5 per cent to 11 
per cent of the steam generated by the boilers, and from 3 per cent to 5 per 
cent for a fan blast. This amounts to about $1000 per year for a steam blast, 
and $500 a year in fuel for a fan blast, for a 1000 h. p. plant on a 10-hour 
basis, when fuel is $2 per ton. 6. Skill required to operate the stoker. 
Careless management causes either loss of fuel in the ash, or loss due to 
poor combustion when the coal is too soon burned out on the grate, thus per- 
mitting cold air to freely pass through the ash. 7. The stoker is a machine 
subject to a severe service, and, like any other machine, wears out and 
requires constant attention. 

W. W. Christie, in article in the Engineering Magazine on the " Economy 
of Mechanical Stoking," says in part : The influence of the mechanical 
stoker upon boiler efficiency has been discussed, but definite information 
is not readily obtained, although general opinions as to the advantage 
of mechanical stoking are numerous. 

The efficiency of a boiler, and consequently of a group of boilers, depends 
upon several independent and distinct factors. 

Thus we have the furnace efficiency, a measure of the completeness of 
the combustion in the furnace ; this is measured by the ratio of the tem- 
perature in the furnace to the temperature of the escaping gases. We 
have also the efficiency of the boiler proper, measured by the quantity of 
heat transmitted to the water compared with that generated in the fur- 
nace. 

There are also two other kinds of efficiencies — one the heat efficiency, per 
pound of fuel, the other the so-called " investment efficiency," which takes 
into account the cost of building, apparatus, boilers, chimneys, wages, and 
fuel. 

It has been maintained that the most economical rate for steam-making 
is that of an evaporation of 4 lbs. of steam per hour per square foot of 
heating surface, which some tests will show is the case. Other tests, 
however, show that it may vary, while the steam economy referred to 1 lb. 
of coal may remain constant. 

The completeness of combustion can be told best by the temperature of 
the escaping gases, and by an analysis of their chemical composition. 
Thus, for an excellent combustion, the temperature of discharge gases 
should not be higher than 400-500° F. If the percentage of oxygen is 1.5 



1360 



STEAM. 



to 2 per cent, it indicates that the fires are too thick, and the rate of com- 
bustion too high for the draft employed. 

If the oxygen exceeds 8 per cent, the fires are too thin, the draft too 
heavy, or too much cold air is entering the furnace above the fire. 

If there is an excess of CO and of O, the boiler is faulty in design, and 
good results cannot be expected. The quantity of air fed to the fire also 
influences the economy of the boiler to a limited degree. 




Per <Sq. ft. of heating surface per B.U. P.; 5 6 7 8 9 10 11 12 13 14 15 16 17 

Hour| Water per sq.ft. of heating surface; 0.90 5.75 4.92 4.31 3.83 3.45 3.13 2.87 2.65 2.46 2.30 2.15 2.03 
Full lines connect StokerJTests Dotted Lines connect Hand Fired Tests. 



Fig. 5. 



Diagram Showing Comparative Economy of Mechanical and 
Hand Stoking. 



This diagram was prepared from results cf about twenty tests made by 
engineers of high standing and ability, and these special ones were selected 
because the heating values of the fuels had been determined by a calori- 
meter, and all the various details were reported in full. 

WATER. 

Weig-ht of Water per Cubic Foot, from 32° to 212° F M and heat- 
units per pound, reckoned above 32° F. (Wm. Kent, Trans. A. S. M. E., 
vi.90.) 





is 


CO 




is 


CO 


c3 ,' 


is 


CO 
4* 


, 


,1s 


CO 






a 
a 


S3 -* 




p 
p 


^p 


P 
P 
4-> 




,J*P 


p 
p 


fcis 


•p ® O 


CS 




.%<v o 


c3 


5 ■^'C 


■a ® o 


c3 


2 Pi2 


"S X ° 


c5 


<c £,£; 


CD 


*> p<£ 


<X> 


® ft'+H 


<X> 


S^-P 


J~ P*«w 


CD 


H 


£ 


w 


H 


? 


w 


H 


£ 


w 


H 


w 


32 


62.42 


0. 


41 


62.42 


9. 


50 


62.41 


18. 


59 


62.38 


27.01 


33 


62.42 


i. 


42 


62 42 


10. 


51 


62.41 


19. 


60 


62.37 


28.01 


34 


62.42 


2. 


43 


62.42 


11. 


52 


62.40 


20. 


61 


62.37 


29.01 


35 


62.42 


3. 


44 


62.42 


12. 


53 


62.40 


21.01 


62 


62.36 


30.01 


36 


62.42 


4. 


45 


62.42 


13. 


54 


62.40 


22.01 


63 


62.36 


31.01 


37 


62.42 


5. 


46 


62.42 


14. 


55 


62.39 


23,01 


64 


62.35 


32.01 


38 


62.42 


6. 


47 


62.42 


15. 


56 


62.39 


24.01 


65 


62.34 


33.01 


39 


62.42 


7. 


48 


64.41 


16. 


57 


62.39 


25.01 


66 


62.34 


34.02 


40 


62.42 


8. 


49 


62.41 


17. 


58 


62.38 


26.01 


67 


62.33 


35.02 



WATER. 



1361 



Weight of Water — Continued . 





MS m 




Ms 


CO 




M S 


CD 




Ms 


50 




S.Q 


*j 


• 


5.Q 


*J 


ft£w> 


~& 


■^ 


|2& 


~& 


-»-» 


s< tub 


~P 


P 


2 h 


-3 


p 




a 
p 


bfliH o 


P 


as 


.,-H CD O 


eS 


s 3 © 


•H ® O 


?3 




•H fllO 


"eS 


£ *3 


•7! <V O 


03 


£ ft&H 


<0 


£ +3"*3 


£ftfc 


cd 


® ftfr 


CD 


^ 


CD 


H 


£ 


h -1 


H 


w 


H 


& 


w 


H 


w 


68 


62.33 


36.02 


105 


61.96 


73.10 


141 


61.36 


109.25 


177 


60.62 


145.52 


69 


62.32 37.02 


106 


61.95 


74.10 


142 


61.34 


110.26 


178 


60.59 


146.52 


70 


62.31 


38.02 


107 


61.93 


75.10 


143 


61.32 


111.26 


179 


60.57 


147.53 


71 


62.31 


39.02 


108 


61.92 


76.10 


144 


61.30 


112.27 


180 


60.55 


148.54 


72 


62.30 


40.02 


109 


61.91 


77.11 


145 


61.28 


113.28 


181 


60.53 


149.55 


73 


62.29 


41.02 


110 


61.89 


78.11 


146 


61.26 


114.28 


182 


60.50 


150.56 


74 


62.28 


42.03 


111 


61.88 


79.11 


147 


61.24 


115.29 


183 


60.48 


151.57 


75 


62.28 


43.03 


112 


61.86 


80.12 


148 


61.22 


116.29 


184 


60.46 


152.58 


76 


62.27 


44.03 


113 


61.85 


81.12 


149 


61.20 


117.30 


185 


60.44 


153.59 


77 


62.26 


45.03 


114 


61.83 


82.13 


150 


61.18 


118.31 


186 


60.41 


154.60 


78 


62.25 


46.03 


115 


61.82 


83.13 


151 


61.16 


119.31 


187 


60.39 


155.61 


79 


62.24 


47.03 


116 


61.80 


84.13 


152 


61.14 


120.32 


188 


60.37 


156.62 


80 


62.23 


48.04 


117 


61.78 


85.14 


153 


61.12 


121.33 


189 


60.34 


157.63 


81 


62.22 


49.04 


118 


61.77 


86.14 


154 


61.10 


122.33 


190 


60.32 


158.64 


82 


62.21 


50.04 


119 


61.75 


87.15 


155 


61.08 


123.34 


191 


60.29 


159.65 


83 


62.20 


51.04 


120 


61.74 


88.15 


156 


61.06 


124.35 


192 


60.27 


160.67 


84 


62.19 


52.04 


121 


61.72 


89.15 


157 


61.04 


125.35 


193 


60.25 


161.68 


85 


62.18 


53.05 


122 


61.70 


90.16 


158 


61.02 


126.36 


194 


60.22 


162.69 


86 


62.17 


54.05 


123 


61.68 


91.16 


159 


61.00 


127.37 


195 


60.20 


163.70 


87 


62.16 


55.05 


124 


61.67 


92.17 


160 


60.98 


128.37 


196 


60.17 


164.71 


88 


62.15 


56.05 


125 


61.65 


93.17 


161 


60.96 


129.38 


197 


60.15 


165.72 


89 


62.14 


57.05 


126 


61.63 


94.17 


162 


60.94 


130.39 


198 


60.12 


166.73 


90 


62.13 


58.06 


127 


61.61 


95.18 


163 


60.92 


131.40 


199 


60.10 


167.74 


91 


62.12 


59.06 


128 


61.60 


96.18 


164 


60.90 


132.41 


200 


60.07 


168.75 


92 


62.11 


60.06 


129 


61.58 


97.19 


165 


60.87 


133.41 


201 


60.05 


169.77 


93 


62.10 


61.06 


130 


61.56 


98.19 


166 


60.85 


134.42 


202 


60.02 


170.78 


94 


62.09 


62.06 


131 


61.54 


99.20 


167 


60.83 


135.43 


203 


60.00 


171.79 


95 


62.08 


63.07 


132 


61.52 


100.20 


168 


60.81 


136.44 


204 


59.97 


172.80 


96 


62.07 


64.07 


133 


61.51 


101.21 


169 


60.79 


137.45 


205 


59.95 


173.81 


97 


62.06 


65.07 


134 


61.49 


102.21 


170 


60.77 


138.45 


206 


59.92 


174.83 


98 


62.05 


66.07 


135 


61.47 


103.22 


171 


60.75 


139.46 


207 


59.89 


175.84 


99 


62.03 


67.08 


136 


61.45 


104.22 


172 


60.73 


140.47 


208 


59.87 


176.85 


100 


62.02 


68.08 


137 


61.43 


105.23 


173 


60.70 


141.48 


209 


59.84 


177.86 


101 


62.01 


69.08 


138 


61.41 


106.23 


174 


60.68 


142.49 


210 


59.82 


178.87 


102 


62.00 


70.09 


139 


61.39 


107 24 


175 


60.66 


143.50 


211 


59.79 


179.89 


103 


61.99 


71.09 


140 


61.37 


108.25 176 


60.64 


144.51 


212 


59.76 


180.90 


104 


61.97 


72.09 






1 













Weig-ht of Water at Temperatures Above 312° T. 

(Dr. R. H. Thurston, " Engine and Boiler Trials," p. 548.) 





o 




© 




o 




© 




o 


c3 

Q, H • 


ght, 
nds 
Cubi 
t. 


& - 

'- -— 

CD CD 


eight, 
unds 
r Cubi 
ot. 


CD CD . 


ght, 
nds 
Cubi 
t. 


c8 

CD <D ^ 
ft *-< wV 


ight, 
nds 
Cubi 
t. 


CD CD" 

ft^ v,V 


ight, 
nds 
Cubi 
t. 


£.g <D 


® 2 "- 1 X 


3 P Sf 


P P 4) 


© p *-> X 


a P M 

P£ CD 
CD Q 


CD P U O 


££ <d 

CD Q 


CD P U g 


P Q 


> O Vp 


CD Q 


!> ftftfr 


CD H 


j> O <D O 
t>- ftft&H 


S> ftft.^ 


^a^i 


212 


59.71 


280 


57.90 


350 


55.52 


420 


52.86 


490 


50.03 


220 


59.64 


290 


57.59 


360 


55.16 


430 


52.47 


500 


49.61 


230 


59.37 


300 


57.26 


370 


54.79 


440 


52.07 


510 


49.20 


240 


59.10 


310 


56.93 


380 


54.41 


450 


51.66 


520 


48.78 


250 


58.81 


320 


56.58 


390 


54.03 


460 


51.26 


530 


48.36 


260 


58.52 


330 


56.24 


400 


53.64 


470 


50.85 


540 


47.94 


270 


58.21 


340 


55.88 


410 


53.26 


480 


50.44 


550 


47.52 



1362 



STEAM. 



Expansion of Water. 

(Kopp : corrected by Porter.) 



Cent. 


Fahr. 


Volume. 


Cent. 


Fahr. 


Volume. 


Cent. 


Fahr. 


Volume. 


4° 


39.2° 


1.00000 


35° 


95° 


1.00586 


70° 


158° 


1.02241 


5 


41 


1.00001 


40 


104 


1.00767 


75 


167 


1.02548 


10 


50 


1.00025 


45 


113 


1.00967 


80 


176 


1.02872 


15 


59 


1.00083 


50 


122 


1.01186 


85 


185 


1.03213 


20 


68 


1.00171 


55 


131 


1.01423 


90 


194 


1.03570 


25 


77 


1.00286 


60 


140 


1.01678 


95 


203 


1.03943 


30 


86 


1.00425 


65 


149 


1.01951 


100 


212 


1.04332 



Water for Boiler Feed.* 

(Hunt andClapp, A. I.M. E., 1888.) 

Water containing more than 5 parts per 100,000 of free sulphuric or nitric 
acid is liable to cause serious corrosion, not only of the metal of the boiler 
itself, but of the pipes, cylinders, pistons, and valves with which the steam 
comes in contact. 

The total residue in water used for making steam causes the interior lin- 
ings of boilers to become coated, and often produces a dangerous hard scale, 
which prevents the cooling action of the water from protecting the metal 
against burning. 

Lime and magnesia bicarbonates in water lose their excess of carbonic 
acid on boiling, and often, especially when the water contains sulphuric 
acid, produce, with the other solid residues constantly being formed by the 
evaporation, a very hard and insoluble scale. A larger amount than 100 
parts per 100,000 of total solid residue will ordinarily cause troublesome 
scale, and should condemn the water for use in steam boilers, unless a bet- 
ter can not be obtained. 

The following is a tabulated form of the causes of trouble with water for 
steam purposes, and the proposed remedies, given by Prof. L. M. Norton. 

CAUSES OF INCRUSTATION. 

1. Deposition of suspended matter. 

2. Deposition of deposed salts from concentration. 

3. Deposition of carbonates of lime and magnesia by boiling off carbonic 
Acid, which holds them in solution. 

4. Deposition of sulphates of lime, because sulphate of fime is but slightly 
soluble in cold water, less soluble in hot water, insoluble above 270° F. 

5 Deposition of magnesia, because magnesium salts decompose at high 
temperature. 

6. Deposition of lime soap, iron soap, etc., formed by saponification of 
grease. 



MEANS FOR PREVENTING INCRUSTATION. 

1. Filtration. 

2. Blowing off. 

3. Use of internal collecting apparatus or devices for directing the circu- 
lation. 

4. Heating feed-water. 

* See also " Boiler Waters; Scale, Corrosion, Foaming" by W. Wallace 
Christie. 



WATER. 



1363 



5. Chemical or other treatment of water in boiler. 

6. Introduction of zinc into boiler. 

7. Chemical treatment of water outside of boiler. 

TABULAR VIEW. 



Troublesome Substance. Trouble. 
Sediment, mud, clay, etc. Incrustation. 

Readily soluble salts. " 

Bicarbonates of lime, magnesia, ) 
iron. j 

Sulphate of lime. ** 

C ^ium d6 and Sulphate ° f magne - } Corrosion. 

Carbonate of soda in large) T» M . wi 

amounts. J ?™™S- 

Acid (in mine waters). 



Corrosion. 



Dissolved carbonic acid and oxy- ) 
gen. } 

Grease (from condensed water). 

Organic matter (sewage). 
Organic matter. 



Priming. 
Corrosion. 



Remedy or Palliation. 

Filtration, Blowing off. 

Blowing off. 

( Heating feed. Addition of 
\ caustic soda, lime, or 
^ magnesia, etc. 

S Addition of carb. soda, 
( barium chloride, etc. 

( Addition of carbonate of 
\ soda, etc. 

(Addition of barium chlo- 
( ride, etc. 

Alkali. 

{Heating feed. Addition 
of caustic soda, slacked 
lime, etc. 

( Slacked lime and filtering, 
< Carbonate of soda. 
(^ Substitute mineral oil. 

(Precipitate with alum or 
\ ferric chloride and filter- 
Ditto. 



Solubilities of Scale-making* Materials. 

(" Boiler Incrustation,'* F. J. Rowan.) 

The salts of lime and magnesia are the most common of the impurities 
found in water. Carbonate of lime is held in solution in fresh water by an 
excess of carbonic acid. By heating the water the excess of carbonic acid 
is driven off and the greater part of the carbonate precipitated. At ordi- 
nary temperatures carbonate of lime is soluble in from 16,000 to 24,000 times 
its volume of water ; at* 212° F. it is but slightly soluble, and at 290° F. (43 
lbs. pressure) it is insoluble. 

The solubility of sulphate of lime is also affected by the temperature ; 
according to Regnault, its greatest solubility is at 95° F., where it dissolves 
in 393 times its weight of water ; at 212° F. it is only soluble in 460 times its 
weight of water, and according to M. Coute, it is insoluble at 290° F. 

Carbonate of magnesia usually exists in much smaller quantity than the 
salts of lime. The effect of temperature on its solubility is similar to that 
of carbonate of lime. 

Prof. R. H. Thurston, in his " Manual of Steam Boilers," p. 261, states 
that: 

The temperatures at which calcareous matters are precipitated are : 
Carbonate of lime between 176° and 248° F. 
Sulphate of lime between 284° and 424° F. 
Chloride of magnesium between 212° and 257° F. 
Chloride of sodium between 324° and 364° F. 



1364 STEAM. 



11 Incrustation and sediment," Prof . Thurston says, " are deposited in 
boilers, the one by the precipitation of mineral or other salts previously 
held in solution in the feed-water, the other by the deposition of mineral 
insoluble matters, usually earths, carried into it in suspension or me- 
chanical admixture. Occasionally also vegetable matter of a glutinous 
nature is held in solution in the feed-water, and, precipitated by heat or 
concentration, covers the heating-surfaces with a coating almost impermea- 
ble to heat, and hence liable to cause an over-heating that may be very dan- 
gerous to the structure. A powdery mineral deposit sometimes met with is 
equally dangerous, and for the same reason. The animal and vegetable oils 
and greases carried over from the condenser or feed-water heater are also 
very likely to cause trouble. Only mineral oils should be permitted to be 
thus introduced, and that in minimum quantity. Both the efficiency and 
the safety of the boiler are endangered by any of these deposits. 

"The only positive and certain remedy for incrustation and sediment 
once deposited is periodical removal by mechanical means, at sufficiently 
frequent intervals to insure against injury by too great accumulation. Be- 
tween times, some good may be done by special expedients suited to the 
individual case. No one process and no one antidote will suffice for all 
cases. 

11 Where carbonate of lime exists, sal-ammoniac may be used as a pre- 
ventive of incrustation, a double decomposition occurring, resulting in the 
production of ammonium carbonate and calcium chloride — both of which 
are soluble, and the first of which is volatile. The bicarbonate may be in 
part precipitated before use by heating to the boiling-point, and thus break- 
ing up the salt and precipitating the insoluble carbonate. Solutions of 
caustic lime and metallic zinc act in the same manner. Waters containing 
tannic acid and the acid juices of oak, sumach, logwood, hemlock, and other 
woods, are sometimes employed, but are apt to injure the iron of the boiler, 
as may acetic or other acid contained in the various saccharine matters 
often introduced into the boiler to prevent scale, and which also make the 
lime-sulphate scale more troublesome than when clean. Organic matters 
should never be used. 

4 * The sulphate scale is sometimes attacked by the carbonate of soda, the 
products being a soluble sodium sulphate and a pulverulent insoluble cal- 
cium carbonate, which settles to the bottom like other sediments and is 
easily washed off the heating-surfaces. Barium chloride acts similarly, 
producing barium sulphate and calcium chloride. All the alkalies are used 
at times to reduce incrustations of calcium sulphate, as is pure crude petro- 
leum, the tannate of soda, and other chemicals. 

44 The effect of incrustation and of deposits of various kinds is to enor- 
mously reduce the conducting power of heating-surfaces ; so much so, that 
the power, as well as the economic efficiency of a boiler, may become very 
greatly reduced below that for which it is rated, and the supply of steam 
furnished by it may become wholly inadequate to the requirements of the 
case. 

44 It is estimated that a sixteenth of an inch thickness of hard 4 scale ' on 
the heating-surface of a boiler will cause a waste of nearly one-eighth its 
efficiency, and the waste increases as the square of its thickness. The boil- 
ers of steam vessels are peculiarly liable to injury from this cause where 
using salt water, and the introduction of the surface-condenser has been 
thus brought about as a remedy. Land boilers are subject to incrustation 
by the carbonate and other salts of lime, and by the deposit of sand or mud 
mechanically suspended in the feed- water." 

Kerosene oil ("Boiler Incrustation," Rowan) has been used to advantage in 
removing and preventing incrustation. From extended experiments made 
on a 100 h. p. water tube boiler, fed with water containing 6.5 grains of 
solid matter per gallon, it was found that one quart kerosene oil per day 
was sufficient to keep the boiler entirely free from scale. Prior to the in- 
troduction of the kerosene oil, the water had a corrosive action upon some 
of the fittings attached to the boiler ; but after the oil had been used for a 
few months it was found that the corrosive action had ceased. 

It should be stated, however, that objection has been made to the intro- 
duction of kerosene oil into a boiler for the purpose of preventing incrusta- 



WATER. 1365 

tion, on account of the possibility of some of the oil passing with the steam 
into the cylinder of the engine, and neutralizing the effect of the lubricant 
in the cylinder. 

When oil is used to remove scale from steam-boilers, too much care can- 
not be exercised to make sure that it is free from grease or animal oil. 
Nothing but pure mineral oil should be used. Crude petroleum is one 
thing ; black oil, which may mean almost anything, is very likely to be 
something quite different. 

The action of grease in a boiler is peculiar. It does not dissolve in the 
water, nor does it decompose, neither does it remain on top of the water ; 
but it seems to form itself into " slugs," which at first seem to be slightly 
lighter than the water, so that the circulation of the water carries them 
about at will. After a short season of boiling, these " slugs," or suspended 
drops, acquire a certain degree of " stickiness," so that when they come in 
contact with shell and flues of the boiler, they begin to adhere thereto. 
Then under the action of heat they begin the process of " varnishing " the 
interior of the boiler. The thinnest possible coating of this varnish is suf- 
ficient to bring about over-heating of the plates. 

The time when damage is most likely to occur is after the fires are banked, 
for then, the formation of steam being checked, the circulation of water 
stops, and the grease thus has an opportunity to settle on the bottom of the 
boiler and prevent contact of the water with the fire-sheets. Under these 
circumstances, a very low degree of heat in the furnace is sufficient to over- 
heat the plates to such an extent that bulging is sure to occur. 

Zinc as a Scale Preventive. — Dr. Corbigny gives the following hypoth- 
esis : he says that " the two metals, iron and zinc, surrounded by water at a 
high temperature, form a voltaic pile with a single liquid, which slowly 
decomposes the water. The liberated oxygen combines with the most oxy- 
dizable metal, the zinc, and its hydrogen equivalent is disengaged at the 
surface of the iron. There is thus generated over the whole extent of the 
iron influenced a very feeble but continuous current of hydrogen, and 
the bubbles of this gas isolate at each instant the metallic surface from the 
scale-forming substance. If there is but little of the latter, it is penetrated 
by these bubbles and reduced to mud ; if there is more, coherent scale is 
produced, which, being kept off by the intervening stratum of hydrogen, 
takes the form of the iron surface without adhering to it." 

Zinc, in the shape of blocks, slabs, or as shavings inclosed in a perforated 
vessel, should be suspended throughout the water space of a boiler, care 
being used in getting perfect metallic contact between the zinc and the 
boiler. It should not be suspended directly over the furnace, as the oxide 
might fall upon the surface and be the cause of the plate being over-heated. 
The quantity placed in a boiler should vary with the hardness of the water, 
and the amount used, and should be measured by the surface presented. 
Generally one square inch of surface for every 50 lbs. water in the boiler is 
sufficient. The British Admiralty recommends the renewing of the blocks 
whenever the decay of the zinc has penetrated the slab to a depth of J inch 
below the surface. 

Purification of Feed-Water by Boiling 1 . 

Sulphates can be largely removed from feed-water by heating it to the tem- 
perature due to boiler pressure in a feed-water heater, or " live steam puri- 
fier" before introduction to boiler. This precipitates those salts in the heater 
and the water can then if necessary be pumped through a filter into the boiler. 
The feed-water U first heated as hot as possible in the ordinary exhaust 
feed-water heater in which the carbonates are precipitated, and then run 
through the purifier, which is most generally a receptacle containing a 
number of shallow pans, that can be removed for cleaning, over which the 
feed- water is allowed to flow from one to the other in a thin sheet. Live 
steam at boiler-pressure is introduced into the purifier, heating the water 
to a temperature high enough to precipitate the salts which form scale on 
the pans. This method of treating feed-water is said to largely increase the 
efficiency of a boiler plant by the almost complete avoidance of scale. 
Purification of feed-water by filtration before introduction to the system is 
often practised with good results. 



1366 



STEAM. 



Tattle of Water Analyses. 

Grains per U. S. Gallon of 231 Cubic Inches. 



Where From. 



Buffalo, N. Y., Lake Erie .... 
Pittsburgh, Allegheny River . . , 
Pittsburgh, Monongahela River . 
Pittsburgh, Pa., artesian well . . 
Milwaukee, Wisconsin River . . . 

Galveston, Texas, 1 

Galveston, Texas, 2 

Columbus, Ohio 

Washington, D. C, city supply . . 
Baltimore, Md., city supply . . . 
Sioux City, la., city supply .... 

Los Angeles, Cal., 1 

Los Angeles, Cal., 2 

Bay City, Michigan, Bay 

Bay City, Michigan, River .... 

Cincinnati, Ohio River 

Watertown, Conn 

Fort Wayne, Ind 

Wilmington, Del 

Wichita, Kansas 

Springfield, 111., 1 

Springfield, 111., 2 

Hillsboro, 111 

Pueblo, Colo. 

Long Island City, L. I 

Mississippi River, above Missouri 

River 

Mississippi River, below mouth of 

Missouri River 

Mississippi River at St. Louis, W. W. 
Hudson River, above Poughkeepsie, 

N. Y, 



Croton River, above Croton Dam 
N. Y 

Croton River water from service 
pipes in New York City. .... 

Schuylkill River, above Philadelphia 
Pa 



5.66 

0.37 

1.06 

23.45 

6.23 

13.68 

21.79 

20.76 

2.87 

2.77 

19.76 

10.12 

3.72 

8.47 

4.84 

3.88 

1.47 

8.78 

10.04 

14.14 

12.99 

5.47 

14.56 

4.32 

4.0 

8.24 

10.64 
9.64 

1.06 



3.32 

3.78 

5.12 

5.71 

4.67 

13.52 

29.15 

11.74 

3.27 

0.65 

1.24 

5.84 

12.59 

10.36 

33.66 

0.78 

4.51 

6.22 

6.02 

25.91 

7.40 

4.31 

2.97 

16.15 

28.0 

1.02 

7.41 
6.94 



4.57 
2.36 
2.16 



.16 



.29 



0.58 

0.58 

0.64 

18.41 

1.76 

326.64 

398.99 

7.02 

Trace 

Trace 

1.17 

3.51 

20'.48 
126.78 
1.79 
1.76 
3.51 
4.29 

24.34 
1.97 
1.56 
2.39 
1.20 

16.0 

0.50 

1.36 
1.54 

.11 

.40 



.49 



0.37 

0.78 

1.04 

20.14 

Trace 

V.58 
0.36 
0.10 
1.03 
2.63 
0.76 
1.15 
3.00 

Trace 
1.59 

8.48 

*2.'l9 
4.28 
1.63 
1.97 



1.22 
1.57 

10.76 

1.92 

1.36 

1.30 



0.18 
1.50 
3.20 
0.82 
6.50 

Trace 
4.00 
6.50 
2.10 
3.80 
4.40 
4.10 
6.00 
8.74 
10.92 

Trace 
1.78 
10.98 
6.17 
2.00 
8.62 
5.83 

Trace 
5.12 
1.0 

5.25 

15.86 
9.85 

.77 

.67 



9.74 

6.60 

10.80 

49.43 

39.30 

353.84 

453.93 

46.60 

8.60 

7.30 

27.60 

26.20 

23.07 

49.20 

179.20 

6.73 

9.52 

31.08 

35.00 

66.39 

33.17 

21.45 

21.55 

28.76 

39.0 

15.01 

36.49 
29.54 

12.70 

7.72 
3.72 
4.24 



pumps. 1367 

PUlttPS. 

Feed-Pnmpg. 

These should be at least double the capacity fouud by calculation from 
the amount of water required for the engines, to allow for blowing off, leak- 
age, slip in the pumps themselves, etc., and to enable the pump to keep 
down steam in case of sudden stoppage of the engines when the fires hap- 
pen to be brisk, and in fact should be large enough to supply the boilers 
when run at their full capacity. In addition, for all important plants, there 
should be either a duplicate feed-pump or an injector to act as stand-by in 
case of accident. The speed of the plunger or piston may be 50 feet per 
minute and should never exceed 100 feet per minute, else undue wear and 
tear of the«valves results, and the efficiency is reduced. If the pump be re- 
quired to stand idle without continually working, the plunger or piston and 
rod should be of brass. 

If 

D — diameter of barrel in inches, 

S = stroke in inches, 

n = number of useful strokes per minute, 

w = cubic feet of water pumped per hour, 

W=: lbs. of water pumped per hour ; 

w = 1.7Mw. 

~" 36.6 * 
If Sn—60, 

JF=:1.36Z>*, 
and 

1.36 

Rubber valves may be used for cold water, but brass, rubber composition, 
or other suitable material is required for hot water or oil. 

If a new pump will not start, it may be due to its imperfect connections or 
temporary stiffness of pump. 

Unless the suction lift and length of supply pipe be moderate, afoot-valve, 
a charging connection, and a vacuum chamber are desirable. The suction- 
pipe must be entirely free from air leakage. If the pump refuses to start 
lifting water with full pressure on, on account of the air in the pump-cham- 
ber not being dislodged, but only compressed each stroke, arrange for run- 
ning without pressure until the air is expelled and water flows. This is 
done with a check-valve in the delivery-pipe, and a waste delivery which 
may be closed when water flows. 

Pumping- Hot Water. — With a free suction-pipe, any good pump 
fitted with metal valves and with hot-water packing will pump water hav- 
ing a temperature of 212°, or higher, if so placed that the water will flow 
into it. 

Robert D. Kinney, in "Power," gives the following formula for deter- 
l 111 ?. 1 ]! 8 ,. what height water of temperatures below the boiling point can 
be lifted by suction. 

D — lift in feet, 

A = absolute pressure on surface of water ; if open to air = 14.7 lbs. 
B and W= constants. See table. 

B= l*U-^> x 0.8 = 115.2^—8 



W W 



1368 



STEAM. 



Water Temp. 


B. 


W. 


Water Temp. 


B. 


W. 


Degrees F. 


Degrees F. 


40 


0.122 


62.42 


130 


2.215 


61.56 


50 


0.178 


62.41 


140 


2.879 


61.39 


60 


0.254 


62.37 


150 


3.708 


61.20 


70 


0.360 


62.31 


160 


4.731 


61.01 


80 


0.503 


62.22 


170 


5.985 


60.80 


90 


0.693 


62.12 


180 


7.511 


60.59 


100 


0.942 


62.00 


190 


9.335 


60.37 


110 


1.267 


61.87 


200 


11.526 


60.13 


120 


1.685 


61.72 


210 


14.127 


59.89 



Speed of Water througrh Pump- Passages and Valves. 

The speed of water flowing through pipes and passages in pumps varies 
from 100 to 200 feet per minute. The loss from friction will be considerable 
if the higher speed is exceeded. 

The area of valves should be sufficient to permit the water to pass at a 
speed not exceeding 250 feet per minute. 

The amount of steam which an average engine will require per indicated 
horse-power is usually taken at 30 pounds. It varies widely, however, from 
about 12 pounds in the best class of triple expansion condensing engines up 
to considerably over 90 pounds in many direct-acting pumps. Where an 
engine is overloaded or underloaded more water per horse-power will be re- 
quired than when operated at rated capacity. Horizontal tubular boilers 
will evaporate on an average from 2 to 3 pounds of water per square foot 
heating-surface per hour, but may be forced up to 6 pounds if the grate sur- 
face is too large or the draught too great for economical working. 



Sizes of Direct-acting* Pumps. 

The two following tables are selected as representing the two common 
types of direct-acting pump, viz., the single-cylinder and the duplex. 



Efficiency of Small Direct-acting* Pumps. 

In ''Reports of Judges of Philadelphia Exhibition," 1876, Group xx., 
Chas. E. Emery says : " Experiments made with steam-pumps at the Amer- 
ican Institute Exhibition of 1867 showed that average size steam-pumps do 
not, on the average, utilize more than 50 per cent of the indicated power in 
the steam cylinders, the remainder being absorbed in the friction of the en- 
gine, but more particularly in the passage of the water through the pump. 
Again, all ordinary steam-pumps for miscellaneous use, require that the 
steam-cylinder shall have three to four times the area of the water-cylinder 
to give sufficient power when the steam is accidentally low ; hence, as such 
pumps usually work against the atmospheric pressure, the net or effective 
pressure forms a small percentage of the total pressure, which, with the 
large extent of radiating surface exposed and the total absence of expansion, 
makes the expenditure of steam very large. One pump tested required 120 
pounds weight of steam per indicated horse-power per hour, and it is be- 
lieved that the cost will rarely fall below 60 pounds ; and as only 50 per 
cent of the indicated power is utilized, it may be safely stated that ordinary 
steam pumps rarely require less than 120 pounds of steam per hour for each 
horse-power utilized in raising water, equivalent to a duty of only 15,000.000 
foot pounds per 100 pounds of coal. With larger steam-pumps, particularly 
when they are proportioned for the work to be done, the duty will be mate- 
rially increased. 



PUMPS. 



1369 



Single-Cylinder Direct-acting- Pump. 

(Standard Sizes for ordinary service.) 




ft 

I! 



Capacity 

per 

Minute 

at 
Given 
Speed. 



O 



"So 



x 



Diameter of 






3^ 
4 
4 
5 

5| 

7 

7i 

8 

6 

7 

8 
10 

8 
10 
12 
10 
10 
12 
12 
14 
10 
10 
10 
12 
12 
12 
14 
16 
16 
14 
14 
16 
16 
18 
16 
18 
20 
18 
20 
22 



.14 

.27 

.39 

.51 

.72 

1.64 

1.91 

2.17 

1.47 

2.00 

2.61 

4.08 

2.61 

4.08 

5.87 

4.08 

6.12 

5.87 

8.80 

12.00 

4.08 

6.12 

8.16 

5.87 

8.80 

11.75 

15.99 

13.92 

20.88 

12.00 

15.99 

13.92 

20.88 

26.43 

20.88 

26.43 

32.64 

26.43 

32.64 

39.50 



300 
300 
300 
275 
275 
250 
250 
250 
250 
250 
250 
250 
250 
250 
250 
250 
200 
250 
175 
175 
250 
175 
150 
250 
175 
150 
150 
175 
150 
175 
150 
175 
150 
125 
125 
125 
125 
125 
125 
125 



130 
130 
125 
125 
125 
110 
110 
110 
100 
100 
100 
100 
100 



18 
35 
49 
64 
90 
180 
210 
239 
147 
200 
261 
408 
261 



100 408 
100 587 



100 
70 

100 
70 



408 
428 
587 
616 



70 840 
100 408 



70 
50 
100 
70 
50 
50 



428 
408 
587 
616 
587 
800 



80 1114 

50 1044 

70 840 

50 800 

80 1114 

50 1044 

50 1322 

50 1044 

50 1322 

50 1632 

50 1322 

50 1632 

50 1975 



33 
33 

45i 

45£ 

45i 

58 

58 

58 

67 

67 



68i 

68* 

64 

68^ 

64 



93 
112 



112 
112 

84 
112 

89 
109 

85 
115 
115 
118 
118 
118 
118 
118 
120 



9h 
15 
15 
15 
17 
17 
17 
20£ 
20* 
30" 
20-t 
30 
30 
30 
24 
30 
28£ 
28* 
28* 
30" 
25 
26 
30 
28i 
26 
34 
34 
38 
27 
34 
34 
34 
40 
38 
40 
40 
40 
40 
40 



1 

1 

1 

1 

1 

1 

1 

1* 

1* 

1* 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

3 

3 

3 

3 

3 

3 



1 
1 
1 
1* 

i| 
i* 

i* 

if 

2 

2 

2 

2* 

2£ 

2* 
2* 
2§ 

2* 
2| 
2£ 
2* 
2£ 
2i 
2* 
2* 
2* 
2* 
2* 
2£ 



3* 
3* 
3i 
3* 
3j 



8 
10 
12 
12 
12 

8 
12 
12 
12 
14 
12 
14 
16 
14 
16 
18 



1370 



STEAM. 



Duplex-Cylinder Direct-acting 1 Pump. 

(Standard sizes for ordinary service.) 













& a 

© d 

d-d 


~ o . 
.3'd'd 

T* c $ 


Sizes of Pipes for 


© 


© 




© 

M4 


o^2 


~ J2 © 

£ O ft 

•3 ft«2 
5.1 © 


Short Lengths. 
To be Increased as 


d 


d 

d 


© 

*d 


2 © 


§*>js 


St3 


0*3 S 
©C-l 3 


Length Increases. 


*>> 

o 


s 


© 




fe|* 


©CO 


I- £ " 










S 
oa 

co 

CM 
O 
M • 

^S © 

S ° 
3 d 


© 

Is 

«M 

o 

M . 

© OD 

II 


l-l 

©"" 
M 
o 

M 

CO 

<M 

o 
,d 

a 

4) 


Z,^ 
.5 © 

^ d 
a o 

©<4H 

s° 

a> © 
cS o 
ft£ 
.22 CO 


M *« 2 

© * 9 

QD ,«^ 

© 5s m 

£ © r> 

1s£ 

-S d 

© ©^ 

go* 


o,4a 

£ 2 «3 

©©*> 

©3£ 


It* 

«w ©»^ 
O bi)© 

.3 §5 


© 

s 

a 

© 


© 

s 

OB 

d 


© 

d 

o 

© 

d 

CO 


© 
ft 

© 

Sh 
08 

,d 
© 

00 


p 


ft 


Hi 


A 


di 


O 


ft 


CO 


m 


s 


3 


2 


3 


.04 


100 to 250 


8 to 20 


% 


t 


* 


11 


1 


4* 


2f 


4 


.10 


100 " 200 


20" 40 


4 


1 


2 


1* 


5| 


3* 


5 


.20 


100 " 200 


40" 80 


5 


1 


i| 


2* 


ll 


6 


4 


6 


.33 


100 " 150 


70" 100 


5f 


1 


i* 


3 


2 


7* 


4* 


6 


.42 


100 " 150 


85 " 125 


6f 


l£ 


2 


4 


3 


7* 


5 


6 


.51 


100 " 150 


100" 150 


7 


If 


2 


4 


3 


7* 


4* 


10 


.69 


75 " 125 


100" 170 


3 


l£ 


2 


4 


3 


9 


5i 


10 


.93 


75 " 125 


135" 230 


2 


2* 


4 


3 


10 


6 


10 


1.22 


75 " 125 


180" 300 


8* 


2 


2* 


5 


4 


10 


7 


10 


1.66 


75 " 125 


245" 410 


9f 


2 


2* 


6 


5 


12 


7 


10 


1.66 


75 " 125 


245" 410 


91 


2* 


3 


6 


5 


14 


7 


10 


1.66 


75 " 125 


245" 410 


»i 


2* 


3 


6 


5 


12 


1 


10 


2.45 


75 " 125 


365" 610 


12 


2* 


3 


6 


5 


14 


10 


2.45 


75 " 125 


365" G10 


12 


2* 


3 


6 


5 


16 


8* 


10 


2.45 


75 " 125 


365" 610 


12 


2* 


3 


6 


5 


18* 


8* 


10 


2.45 


75 " 125 


365" 610 


12 


3 


3* 


6 


5 


20 


8* 


10 


2.45 


75 " 125 


365" 610 


12 


4 


5 


6 


5 


12 


10i 
10i 


10 


3.57 


75 " 125 


530" 890 


14£ 
14i 
lif 

141 


2* 


3 


8 


7 


14 


10 


3.57 


75 " 125 


530" 890 


2* 


3 


8 


7 


16 


101 


10 


3.57 


75 " 125 


530" 890 


2* 


3 


8 


7 


18* 


ioi 


10 


3.57 


75 " 125 


530" 890 


3 


3* 


8 


7 


20 


m 


10 


3.57 


75 " 125 


530" 890 


14i 


4 


5 


8 


7 


14 


12 


10 


4.89 


75 " 125 


730 " 1220 


17 


2* 


3 


10 


8 


16 


12 


10 


4.89 


75 " 125 


730 " 1220 


17 


2* 


3 


10 


8 


18* 


12 


10 


4.89 


75 " 125 


730 " 1220 


17 


3 


3* 


10 


8 


20 


12 


10 


4.89 


75 " 125 


730 " 1220 


17 


4 


5 


10 


8 


18* 


14 


10 


6.66 


75 " 125 


990 " 1660 


19| 


3 


3* 


12 


10 


20 


14 


10 


6.66 


75 u 122 


990 " 1660 


19| 


4 


5 


12 


10 


17 


10 


15 


5.10 


50 " 100 


510 " 1020 


14 


3 


3* 


10 


8 


20 


12 


15 


7.34 


50 " 100 


730 " 1460 


17 


4 


5 


12 


10 


20 


15 
15 


15 
15 


11.47 
11.47 


50 " 100 
50 " 100 


1145 " 2290 
1145 " 2290 


21 
21 










25 





















Let 



HTEdORS. 

liive Steam Injectors. 

W= water injected in pounds her hour. 

P — steam pressure in pounds per square inch- 

Z>zr diameter of throat in inches. 

T=z diameter of throat in millimeters. 



INJECTORS. 



1371 



Then JF=1280Z) 2 Vp 

The rule given by Rankine, " Steam Engine," p. 477, for finding the proper 
sectional area in square inches for the narrowest part of the nozzle is as 
follows : 

cubic feet per hour gross feed-water 

area = ,, 

800 ^pressure in atmospheres 

The expenditure of steam is about one-fourteenth the volume of water 
Injected. 

The following table gives the water delivered for different sizes of injec- 
tors at different pressures ; but when the injector has to lift its water a de- 
duction must be made varying from 10 to 30 per cent according to the lift. 

Deliveries for Live Steam Injectors. 









Pressure of Steam. 






1 
S 

08 


O 00 












® 1-1 














G*rZ 


M 2 


30 lbs. 


60 lbs. 


80 lbs. 


100 lbs. 


120 lbs. 


140 lbs. 


.pH 00 


«mS 














<h .-3 


©•pH 
















®r3 ■ 












O-J- 


•5S 




Delii 


r ery in Gallons per Hour. 




2^ 
















In. 


2 


43 


61 


71 


80 


87 


93 


k 


3 


97 


138 


160 


178 


196 


211 


I 


4 


173 


246 


285 


317 


348 


376 




5 


272 


385 


445 


496 


545 


587 




6 


392 


555 


640 


715 


783 


846 


lj 


7 


533 


755 


871 


973 


1067 


1152 


lj 


8 


696 


985 


1137 


1272 


1393 


1505 


li 


9 


882 


1247 


1440 


1610 


1763 


1905 


H 


10 


1088 


1540 


1777 


1987 


2177 


2352 


2 


11 


1317 


1863 


2150 


2405 


2633 


2846 


2 


12 


1567 


2217 


2560 


2861 


3136 


3387 


21 


13 


1840 


2602 


3005 


3358 


3680 


3975 


21 


14 


2133 


3018 


3485 


3895 


4267 


4610 


2§ 


15 


2450 


3465 


4000 


4471 


4900 


5292 


2£ 


16 


2787 


3942 


4551 


5087 


5575 


6022 




17 


3146 


4450 


5138 


5743 


6291 


6798 


2f 


18 


3527 


4990 


5760 


6438 


7055 


7633 


2f 


19 


3930 


5560 


6418 


7175 


7861 


8492 


2f 


20 


4355 


6160 


7110 


7950 


8710 


9410 


3 



1 millimeter = ^ inch, nearly. 



As the vertical distance the injector lifts is increased, a greater steam 
pressure is required to start the injector, and the highest steam pressure at 
which it will work is gradually decreased. 

If the feed-water is heated a greater steam pressure is required to start 
the injector, and it will not work with as high steam pressure. 

The capacity of an injector is decreased as the lift is increased or the feed- 
water heated. 

Performance of Injectors. — W. Sellers & Co. state that one of 
their injectors delivered 25.5 lbs. water to a boiler per pound of steam ; 
steam pressure 65 lbs.; temperature of feed, 64° F. 

Schaeffer & Budenberg state that their injectors will deliver 1 gallon 
water to a boiler for from 0.4 to 0.8 lbs. steam. They also state that the 
temperatures of feed-water taken by their injector, if non-lifting or at a 
low lift, can be as follows : 



1372 



STEAM. 



Pressure, lbs. . 35 to 45, 50 to 85, 90,105, 120, 135, 150. 

Temperature, °F., 144 to 136, 133 to 130, 129, 122, 118 to 113, 109 to 105, 104 to 100. 

The Hayden & Derby Mfg. Co. state that the results given below are Irom 
actual tests of Metropolitan Double-Tube Injectors. 



With Cold reed-Water. 



On a 2-foot lift : 
On an 8-foot lift : 
On a 14-foot lift : 
On a 20-foot lift : 
When not lifting : 



( Starts with 14 lbs. steam pressure. 
) Works up to 250 lbs. steam pressure. 
( Starts with 23 lbs. steam pressure. 
( Works up to 220 lbs. steam pressure, 
i Starts with 27 lbs. steam pressure. 
( Works up to 175 lbs. steam pressure. 
( Starts with 42 lbs. steam pressure. 
\ Works up to 135 lbs. steam pressure. 
( Starts with 14 lbs. steam pressure. 
( Works up to 250 lbs. steam pressure. 



H ith feed- Water a* 100° F. 



On a 2-foot lift : 
On an 8-foot lift : 
On a 14-foot lift : 
On a 20-foot lift : ' 
When not lifting : 



( Starts with 15 lbs. steam pressure. 
\ Works up to 210 lbs. steam pressure. 
( Starts with 26 lbs. steam pressure. 
( Works up to 160 lbs. steam pressure. 
( Starts with 37 lbs. steam pressure. 
( Works up to 120 lbs. steam pressure, 
i Starts with 46 lbs. steam pressure. 
( Works up to 70 lbs. steam pressure. 
( Starts with 15 lbs. steam pressure. 
| Works up to 210 lbs. steam pressure. 



On a 2-foot lift : 
On an 8-foot lift : 
On a 14-foot lift : 
When not lifting : 



With feed- Water at 120° F. 

( Starts with 20 lbs. steam pressure. 
( Works up to 185 lbs. steam pressure. 
J Starts with 30 lbs. steam pressure. 
( Works up to 120 lbs. steam pressure 
j Starts with 42 lbs. steam pressure. 
( Works up to 75 lbs. steam pressure. 
{ Starts with 20 lbs. steam pressure. 
\ Works up to 185 lbs. steam pressure. 



With Feed- Water at 140° F. 

On a short lift, or when not lifting, this injector will work with steam 
pressures from 20 lbs. to 120 lbs., and on an 8-foot lift with steam pressures 
from 35 lbs. to 70 lbs. _ . , 

Exhaust Injectors working with exhaust steam from an engine, at 
about atmospheric pressure will deliver water against boiler pressure not 
exceeding 80 lbs. per square inch. The temperature of the water may be as 
high as 190° F., while 12 per cent of the water delivered will be condensed 
steam. For pressures over 80 lbs. it is necessary to supplement the exhaust 
steam with a jet of live steam. 

Injector vs. I»ump for Feeding- Boilers. 

The relative value of injectors, direct-acting steam pumps, and pumps 
driven from the engine, is a question of importance to all steam-users. The 
following table (" Stevens Indicator," 1888) has been calculated by D. S. 
Jacobs, M. E., from data obtained bv experiment. It will be noticed that 
when feeding cold water direct to boilers, the injector has a slight economy, 
but Avhen feeding through a heater a pump is much the most economical. 



INJECTORS. 



1373 



Method of Supplying Feed-Water 


Relative Amount 


Saving of Fuel 


to Boiler. 


of Coal Required 


over the 




per Unit of Time, 


Amount 


Temperature of Feed-Water as 
delivered to the Pump or to the 


the Amount for a 


Required 


Direct-Acting 


when the 


Injector, 60° F. Rate of Evap- 


Pump, Feeding 


Boiler is Fed by 


oration of Boiler, 10 lbs. of 


Water at 60°, with- 


a Direct- 


Water per pound of Coal from 


out a Heater, being 


Acting Pump 


and at 212° F. 


taken as Unity. 


without Heater. 


Direct-acting pump feeding water 






at 60°, without a heater .... 


1.000 


.0 


Injector feeding water at 150°, 






without a heater 


.985 


1.5 per cent. 


Injector feeding through a heater 






in which the water is heated 






from 150° to 200° 


.938 


6.2 " 


Direct-acting pump feeding water 






through a heater, in which it is 






heated from 60° to 200° .... 


.879 


12.1 " 


Geared pump, run from the engine, 






feeding water through a heater, 






in which it is heated from 60° to 






200° 


.868 . 


13.2 " 







Sizes for feed- Water JPipes. 

Three and six-tenths gallons of feed-water are required for each h. p. per 
hour. This makes 6 gallons per minute for a 100 h. p. boiler. In proportion- 
ing pipes, however, it is well to remember that boiler-w r ork is seldom per- 
fectly steady, and that as the engine cuts off just as much steam as the work 
demands at each stroke, all the discrepancies of demand and supply have to 
be equalized in the boiler. Therefore we may often have to evaporate dur- 
ing one-half hour 50 to 75 per cent more than the normal requirements. For 
this reason it is sound policy to arrange the feed-pipes so that 10 gallons 
per minute may flow through them, without undue speed or friction, for 
each 100 h. p. of boiler capacity. The following tables will facilitate this 
work. 

Table Giving* Rate of Flow of Water, in feet per minute, 

Throug-h IMpes of Various Sizes, for Varying- 

Quantities of flow. 



Gallons . 
per Min. * 


in. 


1 


in. l£ in. 


l*in. 


2 in. 


2* in. 


3 m. 


4 in. 


5 


218 


1 


221 78* 


r4JL 


30* 


19* 


13* 


7f 


10 


436 


i 


145 157 


109 


61 


38 


27 


15* 


15 


653 




>67h 235| 


163| 


91* 


58* 


40* 


23 


20 


872 


* 


90 314 


218 


122 


78 


54 


30| 


25 1 


L090 


i 


>12* 392* 


272* 


152* 


97* 


67* 


38* 


30 






'35 451 


327 


183 


117 


81 


46 


35 






i 


£7* 549* 


381* 


213* 


136* 


94* 


53§ 


40 






( 


)80 628 


436 


244 


156 


108 


61* 


45 






1] 


L02* 706* 


490* 


274* 


175* 


121* 


69 


50 








785 


545 


305 


195 


135 


76§ 


75 








. . 1177| 


817J 


457* 


292* 


202* 


115 


100 










1090 


610 


380 


270 


153* 


125 












762* 


487* 


337* 


191| 


150 












915 


585 


405 


230 


175 










. . . 


1067* 


682* 


4721 


268* 


200 













1220 


780 


540 


306§ 



1374 



STEAM. 



Table Giving' I.os* in Pressure due to Friction, in Pounds 
per Square Inch, for Pipe lOO Feet Long;. 

(By G. A. Ellis, C. E.) 



Gallons 

Dis- 
charged 
per Min. 


| in. 


lin. 


l£in. 


l£m. 


2 in. 


2^ in. 


3 in. 


4 in. 


5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

75 
100 
125 * 
150 
175 
200 


3.3 
13.0 
28.7 
50.4 
78.0 


( 
" ( 

r 

1! 
2 

3 
4 


).84 
$.16 

}.9S 

2.3 

).0 

'.5 

-.0 

5.0 




0.31 
1.05 
2.38 
4.07 
6.40 
9.15 

12.4 

16.1 

20.2 

24.9 

56.1 
» • • 


0.12 
0.47 
0.97 
1.66 
2.62 
3.75 
5.05 
6.52 
8.15 
10.0 
22.4 
39.0 


6.12 

6.42 

6.91 

1.60 

2.44 
5.32 
9.46 
14.9 
21.2 
28.1 
37.5 


6.21 

6.8l' 
1.80 
3.20 
4.89 
7.0 
9.46 
12.47 


6.10 

6.35 
0.74 
1.31 

1.99 
2.85 
3.85 
5.02 


6.09 
6.33 
6.69 
1.22 



IjOss of Head due to Bends. 

Bends produce a loss of head in the flow of water in pipes. Weisbach 
gives the following formula for this loss : 

H—f ~ where H= loss of head in feet, / = coefficient of friction, v =z ve- 
locity of flow in feet per second, g = 32.2. 

As the loss of head or pressure is inmost cases more conveniently stated in 
pounds per square inch, we may change this formula by multiplying by 
0.433, which is the equivalent in pounds per square inch for one foot head. 

If P = loss in pressure in pounds per square inch, F~ coefficient of fric- 
tion. 

v 2 

P = F -xt-*} v being the same as before. 

From this formula has been calculated the following table of values for F, 
corresponding to various exterior angles, A. 



A — 
F — 



20° 
0.020 


40° 
0.060 


45° 
0.079 


60° 
0.158 


80° 
0.320 


90° 
0.426 


100° 
0.546 


110° 
0.674 


120° 
0,806 



130° 
0.934 



This applies to such short bends as are found in ordinary fittings, such as 
90° and 45° Ells, Tees, etc. 

A globe valve will produce a loss about equal to two 90° bends, a straight- 
way valve about equal to one 45° bend. To use the above formula find the 
speed p. second, being one-sixtieth of that found in Table p. 1373 ; square this 
speed, and divide the result by 64.4; multiply the quotient by the tabular 
value ofF corresponding to the angle of the turn t A. 

For instance, a 400 h.p. battery of boilers is to be fed through a 2-inch pipe. 
Allowing for fluctuations we figure 40 gallons per minute, making 244 feet 
per minute speed, equal to a velocity of 4.6 per second. Suppose our pipe is 
in all 75 feet long ; we have from Table No. 36, for 40 gallons per minute, 
1.60 pounds loss ; for 75 feet we have only 75 per cent of this = 1.20 pounds. 
Suppose we have 6 right-angled ells, each giving Fz=z 0.426. We have then 
4.06 X 4.06 = 16.48 ; divide this by 64.4 = 0,256. Multiply this by F=z 0.42C 



FEED WATER HEATERS. 1375 

pounds, and as there are 6 ells, multiply again by 6, and we have 6 x 0.426 x 
256 = 0.654. The total friction in the pipe is therefore 1.20 -{- 0.654 = 1.854 
pounds per square inch. If the boiler pressure is 100 pounds and the water 
level in the boiler is 8 feet higher than the pump suction level, we have first 
8 X 433 = 3.464 pounds. The total pressure on the pump plunger then is 
100 + 3.464 -4- 1.854= 105.32 pounds per square inch. If in place of 6 right- 
angled ells we had used three 45° ells, they would have cost us only 3 X 
0.079 = 0.237 pounds ; 0.237 X 0.256 = 0.061. 

The total friction head would have been 1.20 + 0.061 = 1.261, and the total 
pressure on the plunger 100 -f- 3.464 + 1.261 = 104.73 pounds per square inch, 
a saving over the other plan of nearly 0.6 pounds. 

To be accurate, we ought to add a certain head in either case, " to produce 
the velocity." But this is very small, being for velocities of ; 

2 . 3 . 4 ; 5 ; 6 ; 8 ; 10 ; 12 and 18 feet per sec. 
0.027 ; 0.061 ; 0.108; 0.168; 0.244; 0.433; 0.672; 0.970 and 2.18 lbs. per sq. in. 
Our results should therefore have been increased by about 0.11 pounds. 

It is usual, however, to use larger pipes, and thus to materially reduce the 
frictional losses. 

Feed Water Heaters. 

(W. W. Christie.) 

Feed Water Heaters may be classified in this way : 

( Steam tube. 

Closed Heaters (indirect) . . . . ° . . . { Water tube. 

j AtmospheriCo 

Open Heaters (direct) j Vacuum. 

The open heater is usually made of cast iron, as this material will with- 
stand the corrosive action of acids found in feed-waters better than any 
other metal. In this type of heater the exhaust steam from engines and 
pumps, and the feed-water broken up into drops by suitable means, are 
brought into immediate contact, and the steam not condensed in heating 
the water passes off to the atmosphere. The quantity of water that can be 
heated is only limited by the amount of steam and water that can be 
brought together. The steam condensed in heating the water is saved and 
utilized for boiler feed. An open heater should be provided with an effi- 
cient oil-separator, a large settling-chamber or hot well in which, if desired, 
a filtering bed of suitable material can be placed to insure the removal from 
the water, of all the impurities held in suspension, a device for skim- 
ming the surface of the water to remove the impurities floating on the water, 
and a large blow-off opening placed at the lowest point in the heater. 

The closed heater is made with a wrought-iron or steel cylindrical shell 
and cast- or wrought-iron heads, having iron or brass tubes inside, 6et in 
tube plates so as to make steam- and water-tight joints, provision being made 
for the expansion and contraction of the tubes. According to the particular 
design of the heater, the exhaust steam passes through or around the tubes, 
the water being on the opposite of the walls of the tubes. The steam and 
water are separated by metal through which the heat of the exhaust steam 
is transmitted to the water. As an oil-separator is very seldom attached to 
a closed heater, the steam condensed in heating the water is wasted. The 
quantity of water that can be heated is limited by the amount of heat that 
can be transmitted through the tubes. The efficiency of heat transmission 
is decreased by the coating of oil that covers the steam side, and the crust 
of scale that coats the water side of the tubes. No provision can be made 
for purifying the water in a closed heater, as the constant circulation of the 
water prevents the impurities from settling. The impurities that are in the 
water pass on into the boiler. Purification must be done by means of an 
auxiliary apparatus. 

When used with a condenser, the feed water heater will increase tne 
vacuum 1 to 2 inches ; when used with cold feed water, the economy is in- 
creased from 7 to 14 per cent ; if feed water is from a hot well, 7 to 8 per cent. 

Two things are very essential to the successful working of all heaters,— 
they must be kept clean from scale and oil deposits, and sufficient exhaust 
steam must be sent through them. 

The probability of there being much scale ingredients thrown down in a 
closed heater where temperature never exceeds 212° F., and in an open heater 
where temperature approaches more nearly to steam temperature, is shown 
By this table 



1376 



STEAM. 



Temperatures at which scale-forming ingredients are precipitated : 

Carbonate of lime 176°-248° F. 

Chloride of magnesium 212°-257° F. 

Sulphate of lime 284° F. -424° F. 

Chloride of sodium 324° F. -364° F. 

The rating of a feed-water heater of the closed type is a subject about 
which little has been written, but the common rule is to give | square feet 
of heating surface for one boiler horse-power. 

In designing, however, the heating surface should be made large enough 
or ample to transmit the maximum number of heat units per unit of time, 
and then the water velocity should be adjusted to suit the capacity required. 

For heat transmitted, one well-known manufacturer uses 350 B. T. Units 
per degree F. difference of temperature per square foot of heating surf ace per 
hour, as a maximum ; other types of heaters would use only 150 to 200 B. T. TJ.'s 
as the maximum. 

As the tubes forming the heating surface in closed heaters are made of 
different materials, if we take 

Copper as 100 "Wrought iron as . . .58 

Brass as 87 Cast iron as .... 49 

we can readily see that if one-third square foot surface area is right for a 
copper pipe, we will need Vs° of i or t?£i or about six-tenths for iron coils, 
per boiler horse-power. 

The power to transmit heat varies not only with the material, but also with 
the design of the heater, the velocity of the water, and water and steam 
capacity of the heater. 

The velocity of the water through the heater should be from 100 to 200 
feet per minute. 

The proportions of open heaters depend largely upon the character of the 
water used in the heater, for it should have sufficient time to become thor- 
oughly heated and the scale-forming ingredients settled and eliminated from 
the feed as it passes out of the heater. 

B.T.U. PER DEG. F. DIF. TEMP. PER SQ. FT. SURFACE PER HOUR. 
° S | § 8 S 



ill! 



< 100 

S 

5 

S 150 





H 


-n'l^M 


>• 






'V, 


JsX 
























1 h'' 




^0c 




^> 


'ftp 






















ki 


s*e 






->^£< 


£^ 






















FT 


*Yv 







































































































G INDICATE PLAIN TUBES H.EAT ABSORPTION CURVES 

• " -CORRUGATED TUBES 

Fig. 6. 
Saving* by Heating- Feed- Water. 

(W. W. Christie.) 

In converting water at 32° F. into steam at atmospheric pressure, it must 
be raised to 212° F., the boiling point. 

The specific heat of water varies somewhat with its temperature, so that to 
raise a pound of water from 32° to 212° F. or 180° F., requires 180.8 heat units. 

To convert it into steam, after it has reached 212° F., requires 965.8 heat 
Units, or in all 180.8 + 965.8=1146.6 units of heat, thermal units. 

The saving to be obtained by the use of waste heat, as exhaust steam, 
heating the water by transfer of some of its heat through metal walls, is 
calculated by this formula: 



PUMP EXHAUST. 



1377 



Gain in per cent = 
in which H 



100 (h 2 — h j _ 100 (t 2 — t x ) 



very nearly, 



H—h x ~ tf-^ + 32 
: total heat in steam at boiler pressure (above that in water at 
32° F.) in B. T. U. 
h 2 = heat in feed-water (above 32° F.) after heating. 
h x =z heat in feed- water (above 32° F.) before heating. 
t 2 =. temperature of feed-water after heating °F. 
t t = temperature of feed-water before heating °F. 
given H= 1146.6, t 2 =: 212, ^ =: 112, or a difference of 100°; and we obtain by 
use of the above formula, gain in per cent =z 9.37, or for 10° approximately 
.937 per cent, for 11° 1.03 per cent, so we may say that for every 11° F. added 
to the feed-water temperature by use of the exhaust steam, 1 per cent of 
fuel saving results. 
The table which follows is taken from " Power." 

Percentage of Saving* in Fuel hy Heating- Feed-Water by 
Waste Steam, Steam at «0 Pounds Oaug-e Pressure. 





Temperature of Water Entering Boiler. 


is 5 

'2 g 


120° 


130° 


140° 


150° 


160° 


170° 


180° 


190° 


1 
200° 


1 
210° 220° 


250° 


35° 


7.24 


8.09 


8.95 


9.89 


10.66 


11.52 


12.38 


13.24 


14.09 


14.95 


15.81 


19.40 


40° 


6.84 


7.69 


8.56 


9.42 


10.28 


11.14 


12.00 


12.87 


13.73 


14.59 


15.45 


18.89 


45° 


6.44 


7.30 


8.16 


9.03 


9.90 


10.76 


11.62 


12.49 


13.36 


14.22 


15.09 


18.37 


50° 


6.03 


6.89 


7.76 


8.64 


9.51 


10.38 


11.24 


12.11 


12.98 


13.85 


14.72 


17.87 


55° 


5.63 


6.49 


7.37 


8.24 


9.11 


9.99 


10.85 


11.73 


12.60 


13.48 


14.35 


17.38 


60° 


5.21 


6.08 


6.96 


7.84 


8.72 


9.60 


10.47 


11.34 


12.22 


13.10 


13.98 


16.86 


65° 


4.80 


5.67 


6.56 


7.44 


8.32 


9.20 


10.08 


10.96 


11.84 


12.72 


13.60 


16.35 


70° 


4.38 


5.26 


6.15 


7.03 


7.92 


8.80 


9.68 


10.57 


11.45 


12.34 


13.22 


15.84 


75° 


3.96 


4.84 


5.73 


6.62 


7.51 


8.40 


9.28 


10.17 


11.06 


11.95 


12.84 


15.33 


80° 


3.54 


4.42 


5.32 


6.21 


7.11 


8.00 


8.88 


9.78 


10.67 


11.57 


12.46 


14.82 


85° 


3.11 


4.00 


4.90 


5.80 


6.70 


7.59 


8.48 


9.38 


10.28 


11.18 


12.07 


14.32 


90° 


2.68 


3.58 


4.48 


5.38 


6.28 


7.18 


8.07 


8.98 


9.88 


10.78 


11.68 


13.81 


95° 


2.25 


3.15 


4.05 


4.96 


5.86 


6.77 


7.66 


8.57 


9.47 


10.38 


11.29 


13.31 


100° 


1.81 


2.71 


3.62 


4.53 


5.44 


6.35 


7.25 


8.16 


9.07 


9.98 


10.88 


12.80 



Pump Exhaust. 

In many plants the only available exhaust steam comes from the steam 
pumps used for elevator service, boiler-feeding, etc. ; or in condensing plants 
from the air-pumps, water-supply, and boiler feed-pumps. It should also be 
remembered that all direct-acting steam pumps are large consumers of 
steam, taking several boiler h. p. for each indicated h. p., and that the ex- 
haust steam from them will heat about six times the same quantity by weight 
of cold water, from 50° to 212° F., and that these pumps, or the independent 
condenser pumps, are more economical when all the exhaust from them is 
used for heating feed-water than the best kind of triple expansion condens- 
ing engines. With the pumps all the heat not used in doing work can be 
conserved and returned to the boiler in the feed-water, whereas even with 
triple expansion engines at least 80 per cent of the total heat in the steam is 
carried away in the condensing water. 

While the supply of exhaust from these pumps may not be sufficient to 
raise the temperature to the highest point, yet the saving is large and con- 
stant. 

These results do not take any account of the purifying action in the 
"open" heaters on the feed-water, the improved condition of which, by di- 
minishing the average deposit within the boiler, materially increases both 
Vhq boiler capacity and the economy ; while the more uniform temperature 



1378 



STEAM. 



accompanying the use of a hot feed reduces the repairs and lengthens the 
life of all boilers. 

If the quantity of water passing through the heater is only what is re- 
quired to furnish steam for the engine from which the exhaust comes, more 
than four-fifths of this exhaust steam will remain uncondensed, and will 
thus become available for other purposes, such as heating buildings, dryer 
systems, etc. ; in which case the returns can be sent back to the boiler by 
suitable means. 

Il'EI JECOWOIMZEMS. 

Performance of a Green Economizer with a Smoky Coal. 
(D. K. Clark, S. E., p, 286.) 

From tests by M. W. Grosseteste, covering a period of three weeks on a 
Green economizer, using a smoke-making coal, with a constant rate of com- 
bustion under the boilers, it is apparent that there is a great advantage in 
cleaning the pipes daily — the elevation of temperature having been in- 
creased by it from 88° to 153°. In the third week, without cleaning, the ele- 
vation of temperature relapsed in three days to the level of the first week ; 
even on the first day it was quickly reduced by as much as half the extent 
of relapse. By cleaning the pipes daily an increased elevation of tempera- 
ture of 65° F. was obtained, whilst a gain of 6% was effected in the evapora- 
tive efficiency. 

The action of Green's economizer was tested by M. W. Grosseteste for a 
period of three weeks. The apparatus consists of four ranges of vertical 
pipes, 6£ feet high, 3| inches in diameter outside, nine pipes in each range, 
connected at top and bottom by horizontal pipes. The water enters all the 
tubes from below, and leaves them from above. The system of pipes is 
enveloped in a brick casing, into which the gaseous products of combustion 
are introduced from above, and which they leave from below. The pipes 
are cleared of soot externally by automatic scrapers. The capacity for 
water is 24 cubic feet, and the total external heating-surface is 290 square 
feet. The apparatus is placed in connection with a boiler having 355 square 
feet of surface. 

Green's Economizer. — Results of Experiments on its Efficiency as Affected 
by the State of the Surface. 

(W. Grosseteste.) 





Temperature of Feed- 


Temperature of Gas- 




water. 


eous Products. 


Time. 














February and March. 


Enter- 


Leav- 




Enter- 


Leav- 






ing 


ing 


Differ- 


ing 


ing 


Differ- 




Feed- 


Feed- 


ence. 


Feed- 


Feed- 


ence. 




heater. 


heater. 




heater. 


heater. 






Fahr. 


Fahr. 


Fahr. 


Fahr. 


Fahr. 


Fahr. 


1st Week 


73.5° 


161.5° 


88.0° 


849° 


261° 


588° 


2d Week 


77.0 


230.0 


153.0 


882 


297 


585 


3d Week — Monday . . 


73.4 


196.0 


122.6 


831 


284 


547 


Tuesday . . 


73.4 


181.4 


108.0 


871 


309 


562 


Wednesday 


79.0 


178.0 


99.0 











Thursday . 


80.6 


170.6 


90.0 


952 


329 


623 


Friday . . 


80.6 


169.0 


88.4 


889 


338 


551 


Saturday 


79.0 


172.4 


93.4 


901 


351 


550 



1st Week. 

Coal consumed per hour 214 lbs. 

Water evaporated from 32° F. per hour 1424 
Water per pound of coal ...... 6.65 



2d Week. 


3d Week. 


216 lbs. 
1525 
7.06 


213 lbs. 
1428 
6.70 



FUEL ECONOMIZERS. 



1379 



The Fuel Economizer Company, Matteawan, N.Y., describe the construc- 
tion of Green's economizer, thus: The economizer consists of a series of sets 
of cast-iron tubes about 4 inches in diameter and 9 feet in length, made in 
sections (of various widths) and connected by " top " and " bottom headers," 
these again being coupled by " top " and " bottom branch pipes " running 
lengthwise, one at the top and the other at the bottom, on opposite sides 
and outside the brick chamber which encloses the apparatus. The waste 
gases are led to the economizer by the ordinary flue from the boilers to the 
chimney. 

The feed-water is forced into the economizer by the boiler pump or in- 
jector, at the lower branch pipe nearest the point of exit of gases, and 
emerges from the economizer at the upper branch pipe nearest the point 
where the gases enter. 

Each tube is provided with a geared scraper, which travels continuously 
up and down the tubes at a slow rate of speed, the object being to keep the 
external surface clean and free from soot, a non-conductor of heat. 

The mechanism for working the scrapers is placed on the top of the econ- 
omizer, outside the chamber, and the motive power is supplied either by a 
belt from some convenient shaft or small independent engine or motor. 
The power required for operating the gearing, however, is very small. 

The apparatus is fitted with blow-off and safety valves, and a space is pro- 
vided at the bottom of the chamber for the collection of the soot, which is 
removed by the scrapers. 

One boiler plant equipped with the Green economizer gave, under test, 
these results. 

The total area of heating surface in the plant was 3,126 square feet, and 
the number of tubes in the economizer 160. The results were as follows: — 



Particulars of Test. 




1. Duration of test hours 

2. Weight of dry coal consumed lbs. 

3. Percentage of ash and refuse . . . per cent 

4. Weight of coal consumed per hour per square 

foot grate surface lbs. 

5. Weight of water evaporated lbs. 

6. Horse-power developed on basis of 30 lbs. per 

h.p. fed at 100° and evaporated at 70 lbs., h.p. 

7. Average boiler pressure (above atmosphere), 

lbs. 

8. Average temperature of feed-water entering 

economizer deg. Fahr. 

9. Average temperature of feed-water entering 

boilers deg. Fahr. 

10. Number of degrees feed-water was heated by 

economizer deg. Fahr. 

11. Average temperature of flue gases entering 

economizer deg. Fahr. 

12. Average temperature of flue gases entering 

chimney deg. Fahr. 

13. Number degrees flue gases were cooled by econ- 

omizer deg. Fahr. 

14. Lbs. water evaporated per lb. of coal, as ob- 

served 

15. Equivalent evaporation per lb. of coal from 

and at 212° 

16. Percentage gained by using the economizer 

per cent 



The steam in this test contained 1.3 per cent of moisture. 



1380 



STEAM. 



W. S. Hntton gives the following results of tests of a steam boiler with 
and without an economizer. 



With Econ- 
omizer. 



Duration of test, hours 

Weight of coal, pounds 

Steam pressure, pounds 

Temp, water entering economizer, degrees 

" " " boiler, degrees . . 

Degrees feed-water heated by economizer 
Temp, gases entering economizer, degrees 

" " " chimney, degrees . 

Degrees gases cooled by economizer . . 
Evaporation per lb. coal, from and at 212°, pounds 
Saving by economizer, per cent . . . 



7856 

58 

88 
225 
137 
618 
365 
253 

10.613 

28.9 



Without 
Econo- 
mizer. 



Hi 

10282 

57 

' 85 



645 
8.235 



Green's I?uel Economizer. — Clark gives the following average re- 
sults of comparative trials of three boilers at Wigan used with and without 
economizers : 

Without With 

Economizers. Economizers. 

Coal per square foot of grate per hour . . . 21.6 21.4 

Water at 100° evaporated per hour .... 73.55 79.32 

Water at 212° per pound of coal 9.60 10.56 

Showing that in burning equal quantities of coal per hour the rapidity of 
evaporation is increased 9.3% and the efficiency of evaporation 10% by the 
addition of the economizer. 

The average temperature of the gases and of the feed-water before and 
after passing the economizer were as follows : 

With 6-ft. grate. 

Before. After. 
Average temperature of gases . . • 649 340 

Average temperature of feed-water . 47 157 

Taking averages of the two grates, to raise the temperature of the feed- 
water 100°, the gases were cooled down 250°. 



With 4-ft. grate. 

Before. After. 

501 312 

41 137 



§TEAM SEPARATORS. 



Carefully conducted experiments have shown that water, oil, or other 
liquids passing through pipes along with steam do not remain thoroughly 
mixed with the stea^i itself, but that the major portion of these liquids fol- 
lows the inner contour of the pipe, especially in the case of horizontal 
pipes. 

From this it would necessarily follow that a rightly designed separator to 
meet these conditions must interrupt the run of the liquid by breaking the 
continuity of the pipe, and offering a receptacle into which the liquid will 
flow freeiy, or fall by gravity — that this appliance must further otter the 
opportunity for the liquid to come to rest out of the current of steam, for it 
is not enough to simply provide a well or a tee in the pipe, since the current 
would jump or draw the liquid over this opening, especially if the velocity 
was high. 

It is also evident that means must be provided in this appliance for inter- 
rupting the progress of those particles of the liquid which are traveling in 
the current of the steam, and do this in such a way that these particles will 



STEAM SEPARATORS. 



1381 



also be detained and allowed to fall into the receptacle provided, which 
receptacle must be fully protected from the action of the current of the 
steam ; otherwise, the separated particles of water or oil will be picked 
up and carried on past the separator. 

To prevent the current from jumping the liquid over the well, and to 
interrupt the forward movement of those particles traveling in or with the 
current, it follows that some obstruction must be interposed in the path of 
the current. 

Steam separators should always be placed as near as possible to the steam 
inlet to the cylinder of the engine. Oil separators are placed in the run of 
the exhaust pipe from engines and pumps, for the purpose of removing the 
oil from the steam before it is used in any way where the presence of oil 
would cause trouble. 

Prof. R. C. Carpenter conducted a series of tests on separators of several 
makes in 1891. The following table shows results under various conditions 
of moisture : 



4 


Test with Steam of about 10% 
of Moisture. 


Tests with Varying Moisture. 


®o* 


Quality of 
Steam 
Before. 


Quality of 
Steam 
After. 


Efficiency 
per cent. 


Quality of 
Steam 
Before. 


Quality of 
Steam • 
After. 


Average 
Efficiency. 


B 
A 
D 
C 
E 
F 


87.0% 
90.1 
89.6 
90.6 

88.4 
88.9 


98.8% 

98.0 

95.8 

93.7 

90.2 

92.1 


90.8 
80.0 
59.6 
33.0 
15.5 
28.8 


66.1 to 97.5% 
51.9 " 98 

72.2 " 96.1 
67.1 " 96.8 
68.6 " 98.1 
70.4 " 97.7 


97.8 to 99 % 

97.9 "99.1 
95.5 " 98.2 
93.7 " 98.4 
79.3 " 98.5 
84.1 " 97.9 


87.6 
76.4 
71.7 
63.4 
36.9 
28.4 



Conclusions from the tests were : 1. That no relation existed between the 
volume of the several separators and their efficiency. 

2. No marked decrease in pressure was shown by any of the separators, 
the most being 1.7 lbs. in E. 

3. Although changed direction, reduced velocity, and perhaps centrifugal 
force are necessary for good separation, still some means must be provided 
to lead the water out of the current of the steam. 

A test on a different separator from those given above was made by Mr. 
Charles H. Parker, at the Boston Edison Company's plant, in November, 
1897, and the following results obtained : 

Length of run 3-4 hrs. 

Average pressure of steam 158 lbs. per sq. in. 

Temperature of upper thermometer in calorimeter on 

outlet of separator 368.5° F. 

Temperature of lower thermometer in calorimeter on 

outlet of separator 291.7° F. 

Normal temperature of lower thermometer, when steam 

is at rest 292.9° F. 

Degrees cooling as shown by lower thermometer . . . 1.2° F. 

Moisture in steam delivered by separator as shown by 

cooling of lower thermometer 06 per cent. 

Water discharged from separator per hour 52 lbs. 

Steam and entrained water passing through engine, as 
shown by discharge from air pump of surface con- 
denser 7359 lbs. 

Steam and entrained water entering separator .... 7411 lbs. 

Moisture taken out by separator 72 

Total moisture in steam (.06 plus .72) 78 per cent. 

Efficiency of separator 92.3 per cent. 



1382 



STEAM. 



SAFETY VAIVES. 
Calculation of Weight, etc., for liever Safety- Valve. 

Let W = weight of ball at end of lever, in pounds ; 
w =z weight of lever itself, in pounds ; 
V=z weight of valve and spindle, in pounds ; 
L = distance between fulcrum and center of ball, in inches ; 
I =: distance between fulcrum and center of valve, in inches ; 
g = distance between fulcrum and center of gravity of lever, in inches; 
A = area of valve, in square inches ; 

P — pressure of steam, in pounds per square inch at which valve will 
open. 

Then PA x I = T V X L + w x g + V X I ; 

D WL_±wg+Vl . 
whence P =: —jf ; 

PAl-wg-Vl . 
W ~ L ■ 

T _ P Al — wg—Vl 
L ~ W 

Example. — Diameter of valve, 4 inches ; distance from fulcrum to center 
of ball, 36 inches ; to center of valve, 4 inches ; to center of gravity of lever, 
16 inches ; weight of valve and spindle, 6 lbs. ; weight of lever, 10 lbs. ; re- 
quired the weight of ball to make the blowing-olf pressure 100 lbs. per 
square inch ; area of 4-inch valve = 12.566 square inches. Then 

„ PAl — wg—Vl 100X12.566X4 — 10X16 — 6X4 

W= =^ = — =5 = 134.5 lbs. 

Rules Governing* Safety- Valve*. 

(Rule of U. S. Supervising Inspectors of Steam-vessels as amended 1894.) 

The distance from the fulcrum to the valve-stem must in no case be less 
than the diameter of the valve-opening ; the length of the lever must not be 
more than ten times the distance from the fulcrum to the valve-stem ; the 
width of the bearings of the fulcrum must not be less than three-quarters 
of an inch ; the length of the fulcrum -link must not be less than four inches; 
the lever and fulcrum-link must be made of wrought iron or steel, and the 
knife-edged fulcrum points and the bearings for these points must be made 
of steel and hardened ; the valve must be guided by its spindle, both above 
and below the ground seat and above the lever, through supports either 
made of composition (gun-metal) or bushed with it ; and the spindle must 
fit loosely in the bearings or supports. 

Lever safety-valves to be attached to marine boilers shall have an area of 
not less than 1 square inch to 2 square feet of the grate surface in the 
boiler, and the seats of all such safety-valves shall have an angle of inclina- 
tion of 45° to the center line of their axes. 

Spring-loaded safety-valves shall be required to have an area of not less 
than 1 square inch to 3 square feet of grate surface of the boiler, except as 
hereinafter otherwise provided for water-tube or coil and sectional boilers, 
and each spring-loaded valve shall be supplied with a lever that will raise the 
valve from its seat a distance of not less than that equal to one-eighth the 
diameter of the valve-opening, and the seats of all such safety-valves shall 
have an angle of inclination to the center line of their axes af 45°. All 
spring-loaded safety-valves for water-tube or coil and sectional boilers 
required to carry a steam-pressure exceeding 175 lbs. per square inch shall 
be required to have an area of not less than 1 square inch to 6 square feet 
of the grate surface of the boiler. Nothing herein shall be construed so as to 
prohibit the use of two safety-values on one water-tube or coil and sectional 
boiler, provided the combined areax>f such valves is equal to that required 
by rule for one such valve. 



SAFETY VALVES. 



1383 



Rule on Safety-Valves in Philadelphia Ordinances.— 

Every boiler when fired separately, and every set or series of boilers when 
placed over one fire, shall have attached thereto, without the interposition 
of any other valve, two or more safety-valves, the aggregate area of which 
shall have such relations to the area of the grate and the pressure within 
the boiler as is expressed in schedule A. 

Schedule A. — Least aggregate area of safety-valve (being the least sec- 
tional area for the discharge of steam) to be placed upon all stationary 
boilers with natural or chimney draught (see note a). 

22.5 G 
P-r-8.62' 
in which A is area of combined safety-valves in inches ; G is area of grate in 
square feet ; P is pressure of steam in pounds per square inch to be carried 
in the boiler above the atmosphere. 

The following table gives the results of the formula for one square foot of 
grate, as applied to boilers used at different pressures : 

Pressures per square inch : 

10 20 30 40 50 60 70 80 90 100 110 120 150 175 

Yalve area in square inches corresponding to one square foot of grate : 
1.2 .79 .58 .46 .38 .33 .29 .25 .23 .21 .19 .17 .14 .12 

[Note a.] — Where boilers have a forced or artificial draught, the inspec- 
tor must estimate the area of grate at the rate of one square foot of grate 
surface for each 16 lbs. of fuel burned on the average per hour. 

The various rules given to determine the proper area of a safety-valve do 
not take into account the effective discharge area of the valve. A correct 
rule should make the product of the diameter and lift proportional to the 
weight of steam to be discharged. 

Mr. A. G. Brown (The Indicator and its Practical Working) gives the fol- 
lowing as the lift of the lever safety-valve for 100 lbs. gauge pressure. Tak- 
ing the effective area of opening at 70 per cent of the product of the rise and 
the circumference 

3 3£ 4 4J 5 6 

.0507 .0492 .0478 .0462 .0446 .043 

For " pop " safety-valves, Mr. Brown gives the following table for the 
rise, effective area, and quantity of steam discharged per hour, taking the 
effective area at 50 per cent of the actual on account of the obstruction 
which the lip of the valve offers to the escape of the steam. 



Diameter of valve, inches 2 1\ 
Rise of valve, inches . . .0583 .0523 



Di. valve in. 


1 


n 


2 


2i 


3 


3^- 


4 


U 


5 


6 


Lift inches. 


.125 


.150 


.175 


.200 


.225 


.250 


.275 


.300 


.325 


.375 


Area, sq. in. 


.196 


.354 


.550 


.785 


1.061 


1.375 


1.728 


2.121 


2.553 


3.535 


Gauge- 
press. 


Steam discharged per hour, lbs. 


30 lbs. 


474 


856 


1330 


1897 


2563 


3325 


4178 


5128 


6173 


8578 


50 


669 


1209 


1878 


2680 


3620 


4695 


5901 


7242 


8718 


12070 


70 


861 


1556 


2417 


3450 


4660 


6144 


7596 


9324 


11220 


15535 


90 


1050 


1897 


2947 


4207 


5680 


7370 


9260 


11365 


13685 


18945 


100 


1144 


2065 


3208 


4580 


6185 


8322 


10080 


12375 


14895 


20625 


120 


1332 


2405 


3736 


5332 


7202 


9342 


11735 


14410 


17340 


24015 


140 


1516 


2738 


4254 


6070 


8200 


10635 


13365 


16405 


19745 


27340 


160 


1696 


3064 


4760 


6794 


9175 


11900 


14955 


18355 


22095 


30595 


180 


1883 


3400 


5283 


7540 


10180 


13250 


16595 


20370 


24520 


33950 


200 


2062 


3724 


5786 


8258 


11150 


14465 


18175 


22310 


26855 


37185 



If we also take 30 lbs. of steam per hour, at 100 lbs. gauge-pressure — 
h.p., we have from the above table : 

Diameter inches .11&2 2£3 3|4 4£&6 
Horse-power . . 38 69 107 153 206 277 336 412 496 687 



1384 



STEAM. 



A boiler having ample grate surface and strong draft may generate 
double the quantity of steam its rating calls for ; therefore in determining 
the proper size of safety-valve for a boiler this fact should be taken into 
consideration and the effective discharge of the valve be double the rated 
steam-producing capacity of the boiler. 

The Consolidated Safety-valve Co.'s circular gives the following rated 
capacity of its nickel-seat " pop " safety-valves : 



Size, in . . 


1 


1* 


1* 


2 


2* 


3 


3* 


I 4 


4* 


5 


5* 


Boiler } from 
H.P. \ to 


8 


10 


20 


35 


60 


75 


100 


325 


150 


175 


200 


10 


15 


30 


50 


75 


100 


125 


150 


175 


200 


275 



rxtjles for (o\im(ti\c; boiler tests. 

The Committee of the A. S. M. E. on Boiler-tests recommended the fol- 
lowing revised code of rules for conducting boiler trials. (Trans, vol. xx. 
See also p. 34, vol. xxi, A. S. M. E., for latest code. 

Code of 1897. 

Preliminaries to a Trial. 

jT. Determine at the outset the specific object of the proposed trial, whether 
it be to ascertain the capacity of the boiler, its efficiency as a steam gener- 
ator, its efficiency and its defects under usual working conditions, the econ- 
omy of some particular kind of fuel, or the effect of changes of design, 
proportion, or operation ; and prepare for the trial accordingly. 

II. Examine the boiler, both outside and inside ; ascertain the dimensions 
of grates, heating surfaces, and all important parts ; and make a full 
record, describing the same, and illustrating special features by sketches. 
The area of heating surfaces is to be computed from the outside diameter of 
water-tubes and the inside diameter of fire-tubes. All surfaces below the 
mean water level which have water on one side and products of combustion 
on the other are to be considered water-heating surface, and all surfaces 
above the mean water level which have steam on one side and products of 
combustion on the other are to be considered as superheating surface. 

III. Notice the general condition of the boiler and its equipment, and 
record such facts in relation thereto as bear upon the objects in view. 

If the object of the trial is to ascertain the maximum economy or capa- 
city of the boiler as a steam generator, the boiler and all its appurtenances 
should be put in first-class condition. Clean the heating surface inside and 
outside, remove clinkers from grates and from sides of the furnace. Re- 
move all dust, soot, and ashes from the chambers, smoke connections, and 
flues. Close air leaks in the masonry and poorly-fitted cleaning-doors. See 
that the damper will open wide and close tight. Test for air leaks by firing 
a few shovels of smoky fuel and immediately closing the damper, observing 
the escape of smoke through the crevices, or by passing the flame of a can- 
dle over cracks in the brickwork. 

IV. Determine the character of the coal to be used. For tests of the effi- 
ciency or capacity of the boiler for comparison with other boilers the coal 
should, if possible, be of some kind which is commercially regarded as a stan- 
dard. For New England and that portion of the country east of the Allegheny 
Mountains, good anthracite egg coal, containing not over 10 per cent of ash, 
and semi-bituminous Clearfield (Pa.), Cumberland (Md.), and Pocahontas 
(Va.) coals are thus regarded. West of the Allegheny Mountains, Poca- 
hontas (Va.), and New River (W. Va.) semi-bituminous, and Youghiogheny 
or Pittsburg bituminous coals are recognized as standards.* There is no 
special grade of coal mined in the Western States which is widely recog- 
nized as of superior quality or considered as a standard coal for boiler test- 
ing. Big Muddy Lump, an Illinois coal mined in Jackson County, 111., is 

* These coals are selected because they are about the only coals which con- 
tain the essentials of excellence of quality, adaptability to various Hinds of 
furnaces, grates, boilers, and methods of firing, and wide distribution and 
general accessibility in the markets. 



RULES FOR CONDUCTING BOILER TESTS. 1385 

suggested as being of sufficiently high grade to answer the requirements in 
districts where it is more conveniently obtainable than the other coals men- 
tioned above. 

For tests made to determine the performance of a boiler with a particular 
kind of coal, such as may be specified in a contract for the sale of a boiler, 
the coal used should not be higher in ash and in moisture than that speci- 
fied, since increase in ash and moisture above a stated amount is apt to 
cause a falling off of both capacity and economy in greater proportion than 
the proportion of such increase. 

V. Establish the correctness of all apparatus used in the test for weighing 
and measuring. These are : 

1. Scales for weighing coal, ashes, and water. 

2. Tanks, or water meters for measuring water. Water meters, as a rule, 
should only be used as a check on other measurements. For accurate work, 
the water should be weighed or measured in a tank. 

3. Thermometers and pyrometers for taking temperatures of air, steam, 
feed-water, waste gases, etc. 

4. Pressure gauges, draft gauges, etc. 

The kind and location of the various pieces of testing apparatus must be 
left to the judgment of the person conducting the test; always keeping in 
mind the main object, i.e., to obtain authentic data. 

VI. See that the boiler is thoroughly heated before the trial to its usual 
working temperature. If the boiler is new and of a form provided with a 
brick setting, it should be in regular use at least a week before the trial, 
so as to dry and heat the walls. If it has been laid off and become cold, it 
should be worked before the trial until the walls are well heated. 

VII. The boiler and connections should be proved to be free from leaks 
before beginning a test, and all water connections, including blow and extra 
feed pipes, should be disconnected, stopped with blank flanges, or bled 
through special openings beyond the valves, except the particular pipe 
through which water is to be fed to the boiler during the trial. During the 
test the blow-off and feed-pipes should remain exposed. 

If an injector is used, it should receive steam directly through a felted 
pipe from the boiler being tested.* 

If the water is metered after it passes the injector, its temperature should 
be taken at the point at which it enters the boiler. If the quantity is deter- 
mined before it goes to the injector, the temperature should be determined 
on the suction side of the injector, and if no change of temperature occurs 
other than that due to the injector, the temperature thus determined is 
properly that of the feed-water. When the temperature changes between 
the injector and the boiler, as by the use of a heater or by radiation, the 
temperature at which the water enters and leaves the injector and that at 
which it enters the boiler should all be taken. The final temperature cor- 
rected for the heat received from the injector will be the true feed-water 
temperature. Thus if the injector receives water at 50° and delivers it at 
120° into a heater which raises it to 210°, the corrected temperature is 210 — 
(120 — 50) =140°. 

See that the steam main is so arranged that water of condensation can- 
not run back into the boiler. 

VIII. Starting and Stopping a Test. — A test should last at least ten hours 
of continuous running, but, if the rate of combustion exceeds 25 pounds of 
coal per square foot of grate per hour it may be stopped when a total of 250 
pounds of coal has been burned per square foot of grate surface. A longer 
test may be made when it is desired to ascertain the effect of widely vary- 
ing conditions, or the performance of a boiler under the working conditions 
°l a Prolonged run - The conditions of the boiler and furnace in all respects 
should be, as nearly as possible, the same at the end as at the beginning of 
the test. The steam pressure should be the same ; the water level the 

* In feeding a boiler undergoing test witH an injector talcing steam from 
another boiler, or the main steam pipe from several boilers, the evaporative 
results may be modified by a difference in the quality of the steam from such 
source compared with that supplied by the boiler being tested, and in some 
cases the connection to the injector may act as a drip for the main steam pipe. 
If it is known that the steam from the main pipe is of the same quality as that 
furnished by the boiler undergoing the test, the steam may be taken from such 
main pipe. 



1386 STEAM. 

same ; the fire upon the grates should be the same in quantity and condi- 
tion ; and the walls, flues, etc., should be of the same temperature. Two 
methods of obtaining the desired equality of conditions of the fire may "be 
used, viz. : those which were called in the Code of 1885 " the standard 
method" and " the alternate method," the latter being employed where it 
is inconvenient to make use of the standard method. 

IX. Standard Method. — Steam being raised to the working pressure, 
remove rapidly all the fire from the grate, close the damper, clean the ash- 
pit, and as quickly as possible start a new fire with weighed wood and coaL, 
noting the time and the water level while the water is in a quiescent stated 
just before lighting the fire. 

k At the end of the test remove the whole fire, which has been burned low, 
clean the grates and ash-pit, and note the water level when the water is in 
a quiescent state, and record the time of hauling the fire. The water level 
should be as nearly as possible the same as at the beginning of the test. 
If it is not the same, a correction should be made by computation, and not 
by operating the pump after the test is completed. 

X. Alternate Method. — The boiler being thoroughly heated byaprelimi* 
nary run, the fires are to be burned low and well cleaned. Note the amount 
of coal left on the grate as nearly as it can be estimated ; note the pressure 
of steam and the water level, and note this time as the time of starting the 
test. Fresh coal which has been weighed should now be fired. The ash- 
pits should be thoroughly cleaned at once after starting. Before the end of 
the test the fires should be burned low, just as before the start, and the 
fires cleaned in such a manner as to leave the bed of coal of^the same 
depth, and in the same condition, on the grates, as at the start. The 
water level and steam pressures should previously be brought as nearly as 
possible to the same point as at the start, and the time of ending of the test 
should be noted just before fresh coal is fired. If the water level is not the 
same as at the start, a correction should be made by computation, and not 
by operating the pump after the test is completed. 

XI. Uniformity of Conditions. — In ail trials made to ascertain maximum 
economy or capacity, the conditions should be maintained uniformly con- 
stant. Arrangements should be made to dispose of the steam so that the 
rate of evaporation may be kept the same from beginning to end. This 
may be accomplished in a single boiler by carrying the steam through a 
waste steam pipe, the discharge from which can be regulated as desired. 
In a battery of boilers, in which only one is tested, the draft can be regu- 
lated on the remaining boilers, leaving the test boiler to work under a con- 
stant rate of production. 

Uniformity of conditions should prevail as to the pressure of steam, the 
height of water, the rate of evaporation, the thickness of fire, the times of 
firing and quantity of coal fired at one time, and as to the intervals between 
the times of cleaning the fires. 

XII. Keeping the Records. — Take note of every event connected with the 
progress of the trial, however unimportant it may appear. Record the 
time of every occurrence and the time of taking every weight and every 
observation. 

The coal should be weighed and delivered to the fireman in equal propor- 
tions, each sufficient for not more than one hour's run, and a fresh portion 
should not be delivered until the previous one has all been fired. The time 
required to consume each portion should be noted, the time being recorded 
at the instant of firing the last of each portion. It is desirable that at the 
same time the amount of water fed into the boiler should be accurately 
noted and recorded, including the height of the water in the boiler, and the 
average pressure of steam and temperature of feed during the time. By 
thus recording the amount of water evaporated by successive portions of 
coal, the test may be divided into several periods if desired, and the degree 
of uniformity of combustion, evaporation, and economy analyzed for each 
period. In addition to these 'records of the coal and the feed-water, half 
hourly observations should be made of the temperature of the feed-water, 
of the flue gases, of the external air in the boiler-room, of the temperature 
of the furnace when a furnace pyrometer is used, also of the pressure of 
steam, and of the readings of the instruments for determining the moisture 
in the steam. A log should be kept on properly prepared blanks containing 
columns for record of the various observations. 

When the "standard method" of starting and stopping the test is used, 



RULES FOR CONDUCTING BOILER TESTS. 1387 

the hourly rate of combustion and of evaporation and: the horse-power may 
be computed from the records taken during the time when the fires are in 
active condition. This time is somewhat less than the actual time which 
elapses between the beginning and end of the run. This method of 
computation is necessary, owing to the loss of time due to kindling the fire 
at the beginning and burning it out at the end. 

XIII. Quality of Steam. — The percentage of moisture in the steam should 
be determined by the use of either a throttling or a separating steam calor- 
imeter. The sampling nozzle should be placed in the vertical steam pipe 
rising from the boiler. It should be made of £-inch pipe, and should extend 
across the diameter of the steam pipe to within half an inch of the opposite 
side, being closed at the end and perforated with not less than twenty £-inch 
holes equally distributed along and around its cylindrical surface, but none 
of these holes should be nearer than £ inch to the inner side of the steam 
pipe. The calorimeter and the pipe leading to it should be well covered 
with felting. Whenever the indications of the throttling or separating 
calorimeter show that the percentage of moisture is irregular, or occasion- 
ally in excess of three per cent, the results should be checked by a steam 
separator placed in the steam pipe as close to the boiler as convenient, with 
a calorimeter in the steam pipe just beyond the outlet from the separator. 
The drip from the separator should be caught and weighed, and the per- 
centage of moisture computed therefrom added to that shown by the 
calorimeter. 

Superheating should be determined by means of a thermometer placed in 
a mercury well inserted in the steam pipe. The degree of superheating 
should be taken as the difference between the reading of the thermometer 
for superheated steam and the readings of the same thermometer for satu- 
rated steam at the same pressure as determined by a special experiment, 
and not by reference to steam tables. 

XIV. Sampling the Coal and Determining its Moisture. — As each barrow 
load or fresh portion of coal is taken from the coal pile, a representative 
shovelful is selected from it and placed in a barrel or box in a cool place 
and kept until the end of the trial. The samples are then mixed and 
broken into pieces not exceeding one inch in diameter, and reduced by the 
process of repeated quartering and crushing until a final sample weighing 
about five pounds is obtained, and the size of the larger pieces is such that 
they will pass through a sieve with J-inch meshes. From this sample two 
one-quart, air-tight glass preserving jars, or other air-tight vessels which 
will prevent the escape of moisture from the sample, are to be promptly 
filled, and these samples are to be kept for subsequent determinations of 
moisture and of heating value, and for chemical analyses. During the 
process of quartering, when the sample has been reduced to about 100 
pounds, a quarter to a half of it may be taken for an approximate determi- 
nation of moisture. This may be made by placing it in a shallow iron pan, not 
over three inches deep, carefully weighing it, and setting the pan in the 
hottest place that can be found on the brickwork of the boiler setting or 
flues, keeping it there for at least twelve hours, and then weighing it. 
The determination of moisture thus made is believed to be approximately 
accurate for anthracite and semi-bituminous coals, and also for Pittsburg 
or Youghiogheny coal ; but it cannot be relied upon for coals mined west of 
Pittsburg, or for other coals containing inherent moisture. For these latter 
coals it is important that a more accurate method be adopted. The method 
recommended by the Committee for all accurate tests, whatever the char- 
acter of the coal, is described as follows : 

Take one of the samples contained in the glass jars, and subject it to a 
thorough air-drying in a warm room, weighing it before and after, thereby 
determining the quantity of surface moisture it contains. Then crush the 
whole of it by running it through an ordinary coffee mill, adjusted so as to 
produce somewhat coarse grains (less than T Vinch), thoroughly mix the 
crushed sample, select from it a portion of from 10 to 50 grams, weigh it in 
a balance which will easilv show a variation as small as 1 part in 1,000, and 
dry it in an air or sand bath at a temperature between 240 and 280 degrees 
Fahr. for one hour. Weigh it and record the loss, then heat and weigh it 
again repeatedly, at intervals of an hour or less, until the minimum weight 
has been reached and the weight begins to increase by oxidation of a por- 
tion of the coal. The difference between the original and the minimum 
weight is taken as the moisture in the air-diaed coal. This moisture should 



(*-?) 



1388 STEAM. 

preferably be made on duplicate samples, and the results should agree 
within 0.3 to 0.4 of one per cent, the mean of the two determinations being 
taken as the correct result. The sum of the percentage of moisture thus 
found and the percentage of surface moisture previously determined is the 
total moisture. 

XV. Treatment of Ashes and Refuse. — The ashes and refuse are to be 
weighed in a dry state. For elaborate trials a sample of the same should 
be procured and analyzed. 

XVI. Calorific Tests and Analysis of Coal. — The quality of the fuel 
should be determined either by heat test or by analysis, or by both. 

The rational method of determining the total heat of combustion is to 
burn the sample of coal in an atmosphere of oxygen gas, the coal to be 
sampled as directed in Article XIV. of this code. 

The chemical analysis of the coal should be made only by an expert 
chemist. The total heat of combustion computed from the results of the 
ultimate analysis may be obtained by the use of Dulong's formula (with 
constants modified by recent determinations), viz. : 14,600 C -\- 62,000 

-J- 4,000 S, in which C, H, O, and S refer to the proportions of 

carbon, hydrogen, oxygen, and sulphur respectively, as determined by the 
ultimate analysis.* 

It is recommended that the analysis and the heat test be each made by 
two independent laboratories, and the mean of the two results, if there is 
any difference, be adopted as the correct figures. 

It is desirable that a proximate analysis should*also be made to determine 
the relative proportions of volatile matter and fixed carbon in the coal. 

XVII. Analysis of Flue Gases. — The analysis of the flue gases is an espe- 
cially valuable method of determining the relative value of different meth- 
ods of firing, or of different kinds of furnaces. In making these analyses, 
great care should be taken to procure average samples — since the compo- 
sition is apt to vary at different points of the flue. The composition is also 
apt to vary from minute to minute, and for this reason the drawings of gas 
should last a considerable period of time. Where complete determinations 
are desired, the analyses should be intrusted to an expert chemist. For 
approximate determinations the Orsat or the Hempel apparatus may be 
used by the engineer. 

XVIII. Smoke Observations. — It is desirable to have a uniform system of 
determining and recording the quantity of smoke produced where bitumi- 
nous coal is used. The system commonly employed is to express the degree 
of smokiness by means of percentages dependent upon the judgment of the 
observer. The Committee does not place much value upon a percentage 
method, because it depends so largely upon the personal element, but if 
this method is used, it is desirable that, so far as possible, a definition be 
given in explicit terms as to the basis and method employed in arriving at 
the percentage. 

XIX. Miscellaneous. — In tests for purposes of scientific research, in 
which the determination of all the variables entering into the test is de- 
sired, certain observations should be made which are in general unneces- 
sary for ordinary tests. These are the measurement of the air supply, the 
determination of its contained moisture, the determination of the amount 
of heat lost by radiation, of the amount of infiltration of air through the 
setting, and (by condensation of all the steam made by the boiler) of the 
total heat imparted to the water. 

As these determinations are not likely to be undertaken except by engi- 
neers of high scientific attainments, it is not deemed advisable to give 
directions for making them. 

XX. Calculations of Efficiency . — Two methods of defining and calculat- 
ing the efficiency of a boiler are recommended. They are : 

-. -ru« • * *.%_ *. •-, Heat absorbed per lb. combustible 

1. Efficiency of the boiler = = — - „ . .. =- — rr^r • 

Heating value of 1 lb. combustible 

o -c^ • * x-u t, -i * Heat absorbed per lb. coal 

2. Efficiency of the boiler and grate = — : - *1 _ .. .• 

Heating value of 1 lb. coal 

* Favre and Silberman give 14,544 B.T.U. per pound carbon; Berthelot 
14,647 B. T. U. Favre anrt Silberman give 62,032 B. T. U. per pound hydro- 
gen ; Thomson 61,816 B. T. U. • 



RULES FOR CONDUCTING BOILER TESTS. 



1389 



The first of these is sometimes called the efficiency based on combustible, 
and the second the efficiency based on coal. The first ig recommended as a 
standard of comparison for all tests, and this is the one which is understood 
to be referred to when the word " efficiency " alone is used without qualifi- 
cation. The second, however, should be included in a report of a test, 
together with the first, whenever the object of the test is to determine the 
efficiency of the boiler and furnace together with the grate (or mechanical 
stoker), or to compare different furnaces, grates, fuels, or methods of firing. 

The heat absorbed per pound of combustible (or per pound coal) is to be 
calculated by multiplying the equivalent evaporation from and at 212° 
per pound combustible (or coal) by 965.7. (Appendix XXI.) 

XXI. The Heat Balance. — An approximate " heat balance," or statement 
of the distribution of the heating value of the coal among the several items 
of heat utilized and heat lost, may be included in the report of a test when 
analyses of the fuel and of the chimney gases have been made. It should 
be reported in the following form : 

Heat Balance, or Distribution of the Heating Value of the Combustible. 

Total Heat Value of 1 lb. of Combustible B. T. U. 



Per 
Cent. 



1. Heat absorbed by the boiler = evaporation from and at 
212° per pound of combustible X 965.7. 
Loss due to moisture in coal — per cent of moisture re- 
ferred to combustible -f 100 X [(212 — t) + 966 + 0.48 
(T — 212)] (t = temperature of air in the boiler-room, 
T=i that of the flue gases). 
Loss due to moisture formed by the burning of hydro- 
gen = per cent of hydrogen to combustible ■—■ 100 X 9 
X [(212 — t) + 966 -f 0.48 ( T — 212)]. 
4.* Loss due to heat carried away in the dry chimney gases 
=: weight of gas per pound of combustible x 0.24 x 
(T—t). 

CO 
5.f Loss due to incomplete combustion of carbons 



2. 



3. 



~co 2 +co 



+ 



per cent Cin combustible 
100" 



X 10,150. 



6. Loss due to unconsumed hydrogen and hydrocarbons, to 
heating the moisture in the air, to radiation, and un- 
accounted for. (Some of these losses may be sepa- 
rately itemized if data are obtained from which they 
may be calculated.) 

Totals 



100.00 



* The weight of gas per pound of carbon burned may be calculated from 
the gas analysis asfolloivs: 

Dry gas per pound carbon = U C ° 2 + * ff + 7 ^° + N) l in which C0 2 , 

CO, O, and Hare the percentages by volume of the several gases. As the 
sampling and analyses of the gases in the present state of the art are liable 
to considerable errors, the result of this calculation is usually only an approx- 
imate one. The heat balance itself is also only approximate for this reason, 
as well as for the fact that it is not possible to determine accurately the per- 
centage of unburned hydrogen or hydrocarbons in the flue gases. 

The weight of dry 'gas per pound of combustible is found by multiplying 
the dry gas per pounci, of carbon by the percentage of carbon in the combusti- 
ble, and dividing by 100. 

t C0 2 and CO are respectively the percentage by volume of carbonic acid 
and carbonic oxide in the flue gases. The quantity 10,150— No. heat units 
generated by burning to carbonic acid one pound of carbon contained in car' 
conic oxide. 



1390 STEAM. 

XXII. Report of the Trial. — The data and results should be reported in 
the manner given in either one of the two following tables, omitting lines 
where the tests have not been made as elaborately as provided for in such 
tables. Additional lines may be added for data relating to the specific 
object of the test. The extra lines should be classified under the headings 
provided in the tables, and numbered, as per preceding line, with sub let- 
ters, a, b, etc. The Short Form of Report, Table No. 2, is recommended 
for commercial tests and as a convenient form of abridging the longer form 
for publication when saving of space is desirable. 

Table Ho. 1. 

Data and Results of Evaporative Test. 

Arranged in accordance with the complete form advised by the Boiler 
Test Committee of the American Society of Mechanical Engineers. 

Made by of boiler at to 

determine . 

Principal conditions | governing the trial 

Kind of fuel 

Kind of furnace 

State of the weather 

1. Date of trial 

2. Duration of trial hours 

Dimensions and Proportions. 
(A complete description of the boiler should be given on an annexed sheet.) 

3. Grate surface . . . width . . . length . . . area . . sq. ft. 

4. Water-heating surface " 

5. Superheating surface . . - M 

6. Ratio of water-heating surface to grate surface 

7. Ratio of minimum draft area to grate surface 

Average Pressures. 

8. Steam pressure by gauge lbs. 

9. Force of draft between damper and boiler ins. of water 

10. Force of draft in furnace " 

11. Force of draft or blast in ash-pit " " 

Average Temperatures. 

12. Of external air deg. 



13. Of fireroom 

14. Of steam 

15. Of feed-water entering heater . . 

16. Of feed-water entering economizer . 

17. Of feed-water entering boiler . . . 

18. Of escaping gases from boiler . . . 

19. Of escaping gases from economizer 

Fuel. 

20. Size and condition 

21. Weight of wood used in lighting fire lbs. 

22. Weight of coal as fired* " 

* Including equivalent of wood used in lighting the fire, not including un- 
burnt coal withdrawn from furnace at times of cleaning and at end of test. One 
pound of wood is taken to 'be equal to 0.4 pound of coal, or, in case greater 
accuracy is desired, as having a heat value equivalent to the evaporation of 
6 pounds of water from and at 212° per pound (6 X 965.7 = 5,794 B. T.U.J. 



RULES FOR CONDUCTING BOILER TESTS. 1391 

23. Percentage of moisture in coal * ... per cent. 

24. Total weight of dry coal consumed . . lbs. 

25. Total ash and refuse lbs. 

26. Total combustible consumed 

27. Percentage of ash and refuse in dry coal per cent 

Proximate Analysis of Coal. 

Of Coal. Of Combustible, 

28. Fixed carbon per cent. per cent. 

29. Volatile matter " " 

30. Moisture " 

31. Ash " 



100 per cent 100 per cent. 

32. Sulphur, separately determined " " 

Ultimate Analysis of Dry Coal. 

33. Carbon (C) per cent. 

34. Hydrogen (B) " 

35. Oxygen (O) " 

36. Nitrogen (X) " 

37. Sulphur (S) " 



100 per cent. 

38. Moisture in sample of coal as received " 

Analysis of Ash and Refuse. 

39. Carbon per cent. 

40. Earthy matter " 

Fuel per Hour. 

41. Dry coal consumed per hour lbs. 

42. Combustible consumed per hour " 

43. Dry coal per square foot of grate surface per hour ... " 

44. Combustible per square foot of water-heating surface per 

hour " 

Calorific Value of Fuel. 

45. Calorific value by oxygen calorimeter, per lb. of dry coal . B. T. U. 

46. Calorific value by oxygen calorimeter, per lb. of combustible " 

47. Calorific value by analysis, per lb. of dry coalt " 

48. Calorific value by analysis, per lb. of combustible .... " 

Quality of Steam. 

49. Percentage of moisture in steam per ceni, 

50. Number of degrees of superheating deg. 

51. Quality of steam (dry steam =z unity) , . . . 

Water. 

52. Total weight of water fed to boiler J lbs. 

53. Equivalent water fed to boiler from and at 212° .... " 

54. Water actually evaporated, corrected for quality of steam 

55. Factor of evaporation § 

56. Equivalent water evaporated into dry steam from and at 

212°. (Item 54 X Item 55) " 

* This is the total moisture in the coal as found by drying it artificially. 
t See formula for calorific value under Article XVI. of Code. 
% Corrected for inequality of water level and of steam pressure at begin 
ging and end of test. 

§ Factor of evaporation — ~ ' in which H and h are respectively the 

total heat in steam of the average observed pressure, and in water of the aver- 
age observed temperature of the feed. 



1392 STEAM. 

Water per Hour 

57. Water evaporated per hour, corrected for quality of steam lbs. 

58. Equivalent evaporation per hour from and at 212° .... " 

59. Equivalent evaporation per hour from and at 212° per 

square foot of water-heating surface " 

Horse-Power. 

60. Horse-power developed. (34£ lbs. of water evaporated per 

hour into dry steam from and at 212° equals one horse- 
power) * H.P. 

61. Builders' rated horse-power «« 

62. Percentage of builders' rated horse-power developed . . . per cent. 

Economic Results. 

63. Water apparently evaporated per lb. of coal under actual 

conditions. (Item 53 -7- Item 22) lbs. 

64. Equivalent evaporation from and at 212° per lb. of coal 

(including moisture). (Item 56 -j- Item 22) " 

65. Equivalent evaporation from and at 212° per lb. of dry 

coal. (Item 56 -f- Item 24) " 

66. Equivalent evaporation from and at 212° per lb. of combus- 

tible. (Item 56 ~ Item 26) « 

(If the equivalent evaporation, Items 64, 65, and 66, is 
not corrected for the quality of steam, the fact should 
be stated.) 

Efficiency. 

67. Efficiency of the boiler ; heat absorbed by the boiler per 

lb. of combustible divided by the heat value of one lb. 

of combustible t per cent. 

68. Efficiency of boiler, including the grate ; heat absorbed by 

the boiler, per lb. of dry coal fired, divided by the heat 
value of one lb. of dry coal t 

Cost of Evaporation. 

69. Cost of coal per ton of 2,240 lbs. delivered in boiler room . $ 

70. Cost of fuel for evaporating 1,000 lbs. of water under ob- 

served conditions $ 

71. Cost of fuel used for evaporating 1,000 lbs. of water from 

and at 212° $ 

Smoke Observations. 

72. Percentage of smoke as observed 

73. Weight of soot per hour obtained from smoke meter . . . 

74. Volume of soot obtained from smoke meter per hour . . 

Tattle !¥©. 2. 

Data and Results of Evaporative Test. 

Arranged in accordance with the Short Form advised by the Boiler Test 
Committee of the American Society of Mechanical Engineers. 

Made by on boiler, at to 

determine 

* Held to be the equivalent of 30 lbs. of water per hour evaporated from 
100° Fahr. into dry steam at 70 lbs. gauge pressure. 

t In all cases where the word " combustible ** is used, it means the coal with- 
out moisture and ash, but including all other constituents. It is the same as 
what is called in Europe " coal dry and free from ash.** 

t The heat value of the coal is to be determined either by an oxygen calorim- 
eter or by calculation from ultimate analysis. When both methods are 
used the mean value is to be taken. 



RULES FOB CONDUCTING BOILER TESTS. 1393 

Grate surface sq.ft. 

Water-heating surface 

Superheating surface ** 

Kind of fuel 

Kind of furnace 

Total Quantities. 

1. Date of trial 

2. Duration of trial . . . , hours. 

3. Weight of coal as fired lbs. 

4. Percentage of moisture in coal per cent. 

5. Total weight of dry coal consumed lbs. 

6. Total ash and refuse " 

7. Percentage of ash and refuse in dry coal per cent. 

8. Total weight of water fed to the boiler lbs. 

9. Water actually evaporated, corrected for moisture or super- 

heat in steam " 

Hourly Quantities. 

10. Dry coal consumed per hour lbs. 

11. Dry coal per hour per square foot of grate surf ace ... " 

12. Water fed per hour " 

13. Equivalent water evaporated per hour from and at 212° 

corrected for quality of steam " 

14. Equivalent water evaporated per square foot of water- 

heating hour " 

Average Pressures, Temperatures, etc. 

15. Average boiler pressure . . lbs. per sq. in 

16. Average temperature of feed-water deg. 

17. Average temperature of escaping gases " 

18. Average force of draft between damper and boiler . . . ins. of water 

19. Percentage of moisture in steam, or number of degrees of 

superheating 

Horse-Power. 

20. Horse-power developed (Item 13 -f- 34£) H.P. 

21. Builders' rated horse-power " 

22. Percentage of builders' rated horse-power per cent. 

Economic Results. 

23. Water apparently evaporated per pound of coal under 

actual conditions. (Item 8 -7- Item 3) lbs. 

24. Equivalent water actually evaporated from and at 212° per 

pound of coal as fired. (Item 9 ~ Item 3) " 

25. Equivalent evaporation from and at 212° per pound of dry 

coal. (Item 9 -f- Item 5) M 

26. Equivalent evaporation from and at 212° per pound of 

combustible. [Item 9 -f- (Item 5 — Item 6)] 

(If Items 23, 24, and 25 are not corrected for quality of 
steam, the fact should be stated.) 

Efficiency. 

27. Heating value of the coal per pound B.T.U. 

28. Efficiency of boiler (based on combustible) ** 

29. Efficiency of boiler, including grate (based on coal) ... :i 

Cost of Evaporation. 

30. Cost of coal per ton of 2,240 pounds delivered in boiler-room $ 

31. Cost of coal required for evaporation of 1,000 pounds of 

water from and at 212° $ 



1394 



STEAM. 



IVETIIItJII^AiriOX ©1? THE MOISTURE IM 

§T£AM. 

The determination of the quality of steam supplied by a boiler is one of 
;he most important items in a boiler test. The three conditions to be de- 
termined are : 

a. If the steam is saturated, i.e., contains the quantity of heat due to the 

pressure. 

b. If the steam is wet, i.e., contains less than the amount of heat due to the 

pressure. 

c. If the steam is superheated, i.e., contains more than the amount of heat 

due to the pressure. 

There are several methods of determining the quality of steam ; one being 
to condense all the steam evaporated by a boiler in a surface condenser, and 
weigh the condensing water, taking the temperature at its entrance to and 
exit from the condenser. Another is by use of a barrel calorimeter, in 
which a sample of the steam is condensed directly in a barrel partly filled 
with cold water, the added weight and temperature taken, and by use of a 
formula the quality of steam can be determined. 

Both the above-named methods are now practically obsolete, as their place 
has been taken by the throttling calorimeter, used for steam in which the 
moisture does not exceed 3 per cent, and the separating calorimeter, for 
steam containing a greater amount of moisture. 

Throttling- Calorimeter. 

In its simplest form this instrument can be made up from pipe fittings, 
the only special parts necessary being the throttling nozzle, which is readily 
made by boring out a piece of brass rod that is the same diameter as a half- 
inch steam pipe, leaving a small hole in one end, say T x s inch diameter. The 
inside end of the small hole should be tapered with the end of a drill so as 
not to cause eddies ; and the thermometer well, which is a small piece of 
brass pipe, plugged at one end, and fitted into a half-inch brushing to fit 
into place. The following cut shows the instrument as made up from fittings. 
The whole must be carefully covered with some non-conductor, as hair felt. 

THERMOMETER 
WELL 



INSULATING 
" MATERIAL 




Pig. 7. 

For more accurate work the instruments designed by George H. Barrus, 
M.E., and Prof. R. C. Carpenter, are to be preferred. Professor Carpenter's 
instrument is shown in the following cut, and differs from the primitive 
instrument previously described only by the addition of the manometer, 



DETERMINATION OF MOISTURE. 



1395 



A'hich determines the pressure of the steam above the atmosphere in the 
oody of the calorimeter. With a free exit to the air the pressure in the 
calorimeter may be taken as that of the atmosphere. 



Carpenter's Throttling- Calorimeter. 

(I size. Schaeffer & Budenberg.) 




Fig. 8. 

The perforated pipe for obtaining the sample of steam to be tested should 
preferably be inserted in a vertical pipe, and should reach nearly across 
its diameter. 

Directions tor Use. — Connect' as shown in the preceding cuts, fill 
the thermometer cup with cylinder oil and insert the thermometer. Turn 
on the Globe valve for ten minutes or more in order to bring the tempera- 
ture of the instrument to full heat, after which note the reading of the ther- 
mometer in the calorimeter, and of the attached manometer or of a barometer. 
The steam gauge should be carefully calebrated to see that it is correct. 
A barometer reading taken at the time the calorimeter is in use, gives 
greater accuracy in working up the results than taking the average 
atmospheric pressure as 14.65 pounds. Pressure in pounds may be deter- 
mined from the mercury column of the barometer and manometer by divid- 
ing the inches rise by 2.03, or taking one pound for each two inches of 
mercury. 

Following is the formula for determining the quality of steam by use of 
the throttling calorimeter. 

Hz=z total heat in a pound of steam at the pressure in the pipe. 
h bs total heat in a pound of steam at the pressure in the calorimeter. 
L = latent heat in a pound of steam at the pressure in the pipe. 
t = temperature in the calorimeter. 

b =. temperature of boiling point at calorimeter pressure (taken as 
212° with the " fittings " instrument). 
0.48 = specific heat of superheated steam. 
x sa quality of the steam. 
y sb percentage of moisture in the steam. 
H— h— .48(t — b) 

x = 100 — y. 



y = 



x ioo. 



1396 



STEAM. 



If h be taken as 212°, as it can be with but slight error, then 
H-n*A- -AS jt -212) xm 
L 
Following are tables calculated from the above formula. 

^moisture in Steam. 

Determinations by Throttling Calorimeter. 





Gauge-pressures . 


s 
1 


5 


10 


20 


30 


40 


50 


60 


70 


75 


80 


85 


90 




Per Cent of Moisture in Steam. 


0° 
10° 

20° 
30° 
40° 


0.51 
0.01 


0.90 
0.39 


1.54 

1.02 

.51 

.00 


2.06 

1.54 

1.02 

.50 


2.50 

1.97 

1.45 

.92 

.39 


2.90 
2.36 
1.83 
1.30 
.77 
.24 


3.24 
2.71 
2.17 
1.64 
1.10 
.57 
.03 


3.56 
3.02 
2.48 
1.94 
1.40 
.87 
.33 


3.71 
3.17 
2.63 
2.09 
1.55 
1.01 
.47 


3.86 
3.32 
2.77 
2.23 
1.69 
1.15 
.60 
.06 


3.99 
3.45 
2.90 
2.35 
1.80 
1.26 
.72 
.17 


4.13 
3.58 
3.03 
2.49 
1.94 


50° 










1.40 


60° 












.85 


70° 














.31 





Gauge-pressure. 


1 

•** 


100 


110 


120 


130 


140 


150 


160 


170 


180 


190 


200 


250 










Per Cent of Moisture in 


Steam 






0° 


4.39 


4.63 


4.85 


5.08 


5.29 


5.49 


5.68 


5.87 


6.05 


6.22 


6.39 


7.16 


10° 


3.84 


4.08 


4.29 


4.52 


4.73 


4.93 


5.12 


5.30 


5.48 


5.65 


5.82 


6.58 


20° 


3.29 


3.52 


3.74 


3.96 


4.17 


4.37 


4.56 


4.74 


4.91 


5.08 


5.25 


6.00 


30° 


2.74 


2.97 


3.18 


3.41 


3.61 


3.80 


3.99 


4.17 


4.34 


4.51 


4.67 


5.41 


40° 


2.19 


2.42 


2.63 


2.85 


3.05 


3.24 


3.43 


3.61 


3.78 


3.94 


4.10 


4.83 


50° 


1.64 


1.87 


2.08 


2.29 


2.49 


2.68 


2.87 


3.04 


3.21 


3.37 


3.53 


4.25 


60 J 


1.09 


1.32 


1.52 


1.74 


1.93 


2.12 


2.30 


2.48 


2.64 


2.80 


2.96 


3.67 


70° 


.55 


.77 


.97 


1.18 


1.38 


1.56 


1.74 


1.91 


2.07 


2.23 


2.38 


3.09 


80° 


.00 


.22 


.42 


.63 


.82 


1.00 


1.18 


1.34 


1.50 


1.66 


1.81 


2.51 


90° 








.07 


.26 


.44 


.61 


.78 


.94 


1.09 


1.24 


1.93 


100° 














.05 


.21 


.37 


.52 


.67 
.10 


1.34 


110° 














.76 



The easiest method of making the determinations from the observations 
is by use of the following diagram, prepared by Professor Carpenter. 

Find in the vertical column at the left the pressure observed in the 
main pipe -f- atmospheric pressure (the absolute pressure), then move hori- 
zontally to the right until over the line giving the degree of superheat 
(t — &), and the quality of steam will be found in a curve corresponding to 
one of those shown, and which may be interpolated where results do not 
lome on one of the lines laid down. 



DETERMINATION OF MOISTURE. 



1397 



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10 20 30 40 50 60 70 80 90 

DEGREES OF SUPERHEAT IN THE CALORIMETER 
D.AGRAM GIVING RESULTS FROM THROTTLING CALORIMETER WITHOUT COMPUTATION 

FIG. 9 



1398 



STEAM. 



By putting a valve in the discharge pipe of the calorimeter, being careful 
that when open it offers no obstruction to a free passage of the steam, de- 
terminations may be made from temperatures without reference to a steam 
table, and by using the following diagram by Professor Carpenter no calcu- 
lation is necessary. 

a. Determine the boiling-point of the instrument by opening supply and 

discharge valves, and showering the instrument with cold water to 
produce moisture in the calorimeter, in which case the boiline-Doint 
will be 212° or thereabouts. v^^* 

b. Determine temperature due to the boiler pressure by closing the dis- 

charge-valve, leaving the supply-valve open, and obtain the full boiler 
pressure in the calorimeter. 

c. Open the discharge-valve and let the thermometer settle to the tempera- 

ture due to the superheat. 

Deduct the temperature of the boiling-point from this last temperature to 
obtain the degrees superheat. 

Suppose the boiling-point of the calorimeter to be 213°, the following dia- 
gram will give the result directly from the temperatures. 

To use the diagram when the boiling-point differs from 212°, add to the 
temperature of superheat the difference between the true boiling-point and 
212°, if less than 212° ; and subtract the difference if the true boiling-point 
be greater than 212 ; use the result as before. 



/Separating Calorimeter. 

This instrument separates the moisture from the sample of steam, and the 
percentage is then found by the ordinary formula. 

amount of moisture x 100 . . 

r= per cent moisture. 



total steam discharged as sample " 

One of the most convenient forms of this type of calorimeter is the one 
designed by Professor Carpenter, and shown in Fig. 11. 

The sample of steam is let into the instrument through the angle valve 
6, the moisture gathers in the inner chamber, its weight in pounds and 
hundredths being shown on the scale 12, and the dry steam flows out through 
the small calibrated orifice 8. 

By Napier's law the flow of steam through an orifice is proportional to 
the absolute pressure, until the back pressure equals .58 that of the supply. 

The gauge 9 at the right shows in the outer scale the flow of steam 
through the orifice 8 in a period of 10 minutes' time. 

After attaching the instrument to the pipe from which sample is taken 
through a perforated pipe as with the throttling or other instrument, it 
must be thoroughly wrapped with hair, felt, or other insulator. Steam is 
then turned on through the angle valve, and time enough allowed to thor- 
oughly heat the instrument. 

In taking an observation, first observe and record height of water on 
scale 12, then let the steam flow for 10 minutes, observing the average posi- 
tion of the pointer on the flow-gauge ; at the end of 10 minutes observe 
the height of water in gauge 12, and the difference between this and the 
first observation will be the amount of moisture in the sample ; the percent- 
age of moisture will then be found as follows : 

difference in scale 12 x 100 

difference on scale 12 4- average for 10 minutes on the flow-gauge 

— % moisture. 

For tests and data on " Calorimeters," see papers in Trans. A.S.M.E., by 
Messrs G. H. Barrus, A. A. Goubert, and Professors Carpenter, Denton, 
Jacobus, and Peabody c 



DETERMINATION OF MOISTURE. 



1399 





220 


230 


m 


TEMPERATURE IN CALORIMETER 
250 260 270 280 290 300 


310 


320 


380 


310 










/ 


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CURVES OF QUALITY 

FOR USE WITH 














/ 




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230 


y 




7 




CARPENT 


ER'S THROTTLING CALC 


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?ic 





















































230 240 250 260 270 280 290 300 310 
TEMPERATURE IN CALORIMETER 



330 340 



DIAGRAM FOR COMPUTING RESULTS WITH THROTTLING CALORIMETER. 
Fig. 10. 



1400 STEAM. 

Quality of Steam Shown by Color of Issuing* Jet. 




Fig. 11. Carpenter's New Evaporat- 
ing Calorimeter. (Schaeffer & Bu- 
denberg.) 



Prof. J. E. Denton (Trans. A. S. 
M. E., vol. x., p. 349) has demon- 
strated that jets of steam escaping 
from an orifice in a boiler or steam 
reservoir show unmistakable 
change of appearance to the eye 
when the steam varies less than 
one per cent from the condition of 
saturation either in the direction of 
wetness or superheating. Conse- 
quently if a jet of steam flow from 
a boiler into the atmosphere under 
circumstances such that very lit- 
tle loss of heat occurs through 
radiation, etc., and the jet be 
transparent close to the orifice, or 
be even a grayish white color, 
the steam may be assumed to be 
so nearly dry that no portable 
condensing "calorimeter will be 
capable of measuring the amount 
of water therein. If the jet be 
strongly white, the amount of 
water may be roughly judged up 
to about 2 per cent, but beyond 
this a calorimeter only can deter- 
mine the exact amount of moist- 
ure. With a little experience any 
one may determine by this meth- 
od the conditions of steam within 
the above limits. A common 
brass pet cock may be used as an 
orifice, but it should, if possible, 
be set into the steam drum of the 
boiler and never be placed farther 
away from the latter than four 
feet, and then only when the in- 
termediate reservoir or pipe is 
well covered, for a very short 
travel of dry steam through a 
naked pipe will cause it to become 
perceptibly moist. 

FACTORS OF EVAPO- 
HATI.O.Y, 



In order to facilitate the calcu- 
lation of reducing the actual rate 
of evaporation of water from a certain temperature into steam of a cer- 
tain pressure, into the rate from water at 212° F. into steam of 212° a 



table of factors of evaporation is made up from the formula 



H — h 
965.7 



where 



His the total heat of steam at the observed pressure, and h the total heat 
of feed-water of the observed temperature. 



FACTORS OF EVAPORATION. 



1401 



Table of Factors of Evaporation. 

;(W. W. Christie, M.E.) 



Gauge 




















Pressure. 





10 


20 


30 


40 


45 


50 


52 


54 


Temp, of 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


Feed. 




















212° F. 


1.0003 


1.0088 


1.0149 


1.0197 


1.0237 


1.0254 


1.0271 


1.0277 


1.0283 


209 


1.0035 


1.0120 


1.018U 


1.0228 


1.0268 


1.0286 


1.0302 


1.0309 


1.0315 


206 


1.0066 


1.0151 


1.0212 


1.0260 


1.0299 


1.0317 


1.0334 


1.0340 


1.0346 


203 


1.0098 


1.0183 


1.0243 


1.0291 


1.0331 


1.0349 


1.0365 


1.0372 


1.0378 


200 


1.0129 


1.0214 


1.0275 


1.0323 


1.0362 


1.0380 


1.0397 


1.0403 


1.0409 


197 


1.0160 


1.0246 


1.0306 


1.0354 


1.0394 


1.0412 


1.0428 


1.0434 


1.0441 


194 


1.0192 


1.0277 


1.0338 


1.0385 


1.0425 


1.0443 


1.0460 


1.0466 


1.0472 


191 


1.0223 


1.0308 


1.0369 


1.0417 


1.0457 


1.0474 


1.0491 


1.0497 


1.0503 


188 


1.0255 


1.0340 


1.0400 


1.0448 


1.0488 


1.0506 


1.0522 


1.0528 


1.0535 


185 


1.0286 


1.0371 


1.0432 


1.0480 


1.0519 


1.0537 


1.0554 


1.0560 


1.0566 


182 


1.0317 


1.0403 


1.0463 


1.0511 


1.0551 


1.0568 


1.0585 


1.0591 


1.0598 


179 


1.0349 


1.0434 


1.0495 


1.0542 


1.0582 


1.0600 


1.0616 


1.0623 


1.0629 


176 


1.0380 


1.0465 


1.0526 


1.0574 


1.0613 


1.0631 


1.0648 


1.0654 


1.0660 


173 


1.0411 


1.0497 


1.0557 


1.0605 


1.0645 


1.0663 


1.0679 


1.0685 


1.0692 


170 


1.0443 


1.0528 


1.0589 


1.0636 


1.0676 


1.0694 


1.0710 


1.0717 


1.0723 


167 


1.0474 


1.0559 


1.0620 


1.0668 


1.0707 


1.0725 


1.0742 


1.0748 


1.0754 


164 


1.0505 


1.0591 


1.0651 


1.0699 


1.0739 


1.0756 


1.0773 


1.0780 


1.0786 


161 


1.0537 


1.0622 


1.0682 


1.0730 


1.0770 


1.0788 


1.0804 


1.0811 


1.0817 


158 


1.0568 


1.0653 


1.0714 


1.0762 


1.0801 


1.0819 


1.0836 


1.0842 


1.0848 


155 


1.0599 


1.0684 


1.0745 


1.0793 


1.0833 


1.0850 


1.0867 


1.0873 


1.0880 


152 


1.0631 


1.0716 


1.0776 


1.0824 


1.0864 


1.0882 


1.0898 


1.0905 


1.0911 


149 


1.0662 


1.0747 


1.0808 


1.0855 


1.0895 


1.0913 


1.0930 


1.0936 


1.0942 


146 


1.0693 


1.0778 


1.0839 


1.0887 


1.0926 


1.0944 


1.0961 


1.0967 


1.0973 


143 


1.0724 


1.0810 


1.0870 


1.0918 


1.0958 


1.0975 


1.0992 


1.0998 


1.1005 


140 


1.0756 


1.0841 


1.0901 


1.0949 


1.0989 


1.1007 


1.1023 


1.1030 


1.1036 


137 


1.0787 


1.0872 


1.0933 


1.0980 


1.1020 


1.1038 


1.1055 


1.1061 


1.1067 


134 


1.0818 


1.0903 


1.0964 


1.1012 


1.1051 


1.1069 


1.1086 


1.1092 


1.1098 


131 


1.0849 


1.0934 


1.0995 


1.1043 


1.1083 


1.1100 


1.1117 


1.1123 


1.1130 


128 


1.0881 


1.0966 


1.1026 


1.1074 


1.1114 


1.1132 


1.1148 


1.1155 


1.1161 


125 


1.0912 


1.0997 


1.1057 


1.1105 


1.1145 


1.1163 


1.1179 


1.1186 


1.1192 


122 


1.0943 


1.1028 


1.1089 


1.1136 


1.1176 


1.1194 


1.1211 


1.1217 


1.1223 


119 


1.0974 


1.1059 


1.1120 


1.1168 


1.1207 


1.1225 


1.1242 


1.1248 


1.1254 


116 


1.1005 


1.1090 


1.1151 


1.1199 


1.1239 


1.1256 


14273 


1.1279 


1.1286 


113 


1.1036 


1.1122 


1.1182 


1.1230 


1.1270 


1.1288 


1.1304 


1.1310 


1.1317 


110 


1.1068 


1.1153 


1.1213 


1.1261 


1.1301 


1.1319 


1.1335 


1.1342 


1.1348 


107 


1.1099 


1.1184 


1.1245 


1.1292 


1.1332 


1.1350 


1.1366 


1.1373 


1.1379 


104 


1.1130 


1.1215 


1.1276 


1.1323 


1.1363 


1.1381 


1.1398 


1.1404 


1.1410 


101 


1.1161 


1.1246 


1.1307 


1.1355 


1.1394 


1.1412 


1.1429 


1.1435 


1.1441 


98 


1.1192 


1.1277 


1.1338 


1.1386 


1.1426 


1.1443 


1.1460 


1.1466 


1.1473 


95 


1.1223 


1.1309 


1.1369 


1.1417 


1.1457 


1.1475 


1.1491 


1.1497 


1.1504 


92 


1.1255 


1.1340 


1.1400 


1.1448 


1.1488 


1.1506 


1.1522 


1.1529 


1.1535 


89 


1.1286 


1.1371 


1.1431 


1.1479 


1.1519 


1.1537 


1.1553 


1.1560 


1.1566 


86 


1.1317 


1.1402 


1.1463 


1.1510 


1.1550 


1.1568 


1.1584 


1.1591 


1.1597 


83 


1.1348 


1.1433 


1.1494 


1.1541 


1.1581 


1.1599 


1.1616 


1.1622 


1.1628 


80 


1.1379 


1.1464 


1.1525 


1.1573 


1.1612 


1.1630 


1.1647 


1.1653 


1.1659 


77 


1.1410 


1.1495 


1.1556 


1.1604 


1.1644 


1.1661 


1.1678 


1.1684 


1.1690 


74 


1.1441 


1.1526 


1.1587 


1.1635 


1.1675 


1.1692 


1.1709 


1.1715 


1.1722 


71 


1.1472 


1.1558 


1.1618 


1.1666 


1.1706 


1.1723 


1.1740 


1.1746 


1.1753 


68 


1.1504 


1.1589 


1.1649 


1.1697 


1.1737 


1.1755 


1.1771 


1.1778 


1.1784 


65 


1.1535 


1.1620 


1.1680 


1.1728 


1.1768 


1.1786 


1.1802 


1.1809 


1.1815 


62 


1.1566 


1.1651 


1.1711 


1.1759 


1.1799 


1.1817 


1.1833 


1.1840 


1.1846 


59 


1.1597 


1.1682 


1.1743 


1.1790 


1.1830 


1.1848 


1.1864 


1.1871 


1.1877 


56 


1.1628 


1.1713 


1.1774 


1.1821 


1.1861 


1.1879 


1.1896 


1.1902 


1.1908 


53 


1.1659 


1.1744 


1.1805 


1.1852 


1.1892 


1.1910 


1.1927 


1.1933 


1.1939 


50 


1.1690 


1.1775 


1.1836 


1.1884 


1.1923 


1.1941 


1.1958 


1.1964 


1.1970 


47 


1.1721 


1.1806 


1.1867 


1.1915 


1.1954 


1.1972 


1.1989 


1.1995 


1.2001 


44 


1.1752 


1.1837 


1.1898 


1.1946 


1.1986 


1.2003 


1.2020 


1.2026 


1.2032 


41 


1.1783 


1.1868 


1.1929 


1.1977 


1.2017 


1.2034 


1.2051 


1.2057 


1.2064 


38 


1.1814 


1.1900 


1.1960 


1.2008 


1.2048 


1.2065 


1.2082 


1.2088 


1.2095 


35 


1.1845 


1.1931 


1.1991 


1.2039 


1.2079 


1.2096 


1.2113 


1.2119 


1.2126 


32 


1.1876 


1.1962 


1.2022 


1.2070 


1.2110 


1.2128 


1.2144 


1.2151 


1.2157 



1402 



STEAM. 





Table of factors of Evaporation. 






Gauge 
Pressure. 


56 


58 


60 


65 


70 


75 


80 1 85 


90 


95 


Temp, of 
Feed. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs, 


lbs. 


lbs. 1 lbs. 


lbs. 


lbs. 


212° tf. 


1.0290 


1.02951 1.0301 


1.0315 


1.0329 


1.0341 


1.0353 1.0365 


T.0376 


1.0387 


209 


1.0321 


1.0327 1.0333 


1.0346 


1.0360 


1.0372 


1.0385 1.0397 


1.0408 


1.0419 


206 


1.0352 


1.0358 1 1.0364 


1.0378 


1.0391 


1.0403 


1.0416 1.0428 


1.0439 


1.0450 


203 


1.0384 


1.0390 1.0396 


1.0464 


1.0423 


1.0435 


1.0448 1.0460 


1.0471 


1.0482 


200 


1.0415 


1.0421 1.0427 


1.0441 


1.0454 


1.0466 


1.0479! 1.0491 


1.0502 


1.0513 


197 


1.0447 


1.0453 1.0458 


1.0477 


1.0486 


1.0498 


1.0511 1 1.0522 


1.0533 


1.0544 


194 


1.0478 


1.0484, 1.0490 


1.0504 


1.0517 


1.0529 


1.0542 1.0553 


1.0565 


1.0576 


191 


1.0510 


1.0515 1 1.0521 


1.0535 


1.0549 


1.0561 


1.0573: 1.0585 


1.0596 


1.0607 


188 


1.0541 


1.05471 1.0553 


1.0566 


1.0580 


1.0592 


1.0605 1.0616 


1.0628 


1.0639 


185 


1.0572 


1.0578' 1.0584 


1.0598 


1.0611 


1.0623 


1.06361 1.0648 


1.0659 


1.0670 


182 


1.0604 


1.0610 1.0615 


1.0629 


1.0643 


1.0655 


1.0668 1.0679 


1.0690 


1.0701 


179 


1.0635 


1.0641 1.0647 


1.0660 


1.0674 


1.0686 


1.0699 


1.0710 


1.0722 


1.0733 


176 


1.0666 


1.06721 1.0678 


1.0692 


1.0705 


1.0717 


1.0730 


1.0742 


1.0753 


1.0764 


173 


1.0698 


1.07041 1.0709 


1.0723 


1.0737 


1.0749 


1.0762 


1.0773 


1.0784 


1.0795 


170 


1.0729 


1.0735J 1.0741 


1.0754 


1.0768 


1.0780 


1.0793 


1.0804 


1.0816 


1.0827 


167 


1.0760 


1.07661 1.0772 


1.0786 


1.0799 


1.0811 


1.0824 


1.0836 


1.0847 


1.0858 


164 


1.0792 


1.0798! 1.0803 


1.0817 


1.0831 


1.0843 


1.0856 


1.0867 


1.0878 


1.0889 


161 


1.0823 


1.0829| 1.0835 


1.0848 


1.0862 


1.0874 


1.0887 


1.0898 


1.0910 


1.0921 


158 


1.0854 


1.0860' 1.0866 


1.0880 


1.0893 


1.0905 


1.0918 


1.0929 


1.0941 


1.0952 


155 


1.0886 


1.0892 1 1.0897 


1.0911 


1.0925 


1.0937 


1.0949 


1.0961 


1.0972 


1.0983 


152 


1.0917 


1.0923 1.0929 


1.0942 


1.0956 


1.0968 


1.0981 


1.0992 


1.1004 


1.1015 


149 


1.0948 


1.0954! 1.0960 


1.0974 


1.0987 


1.0999 


1.1012 


1.1023 


1.1035 


1.1046 


146 


1.0979 


1.0985 1.0991 


1.1005 


1.1018 


1.1030 


1.1043 


1.1055 


1.1066 


1.1077 


143 


1.1011 


1.1017 


1.1022 


1.1036 


1.1050 


1.1062 


1.1074 


1.1086 


1.1097 


1.1108 


140 


1.1042 


1.1048 


1.1054 


1.1067 


1.1081 


1.1093 


1.1106 


1.1117 


1.1129 


1.1140 


137 


1.1073 


1.1079 


1.1085 


1.1099 


1.1112 


1.1124 


1.1137 


1.1148 


1.1160 


1.1171 


134 


1.1104 


1.1110 


1.1116 


1.1130 


1.1143 


1.1155 


1.1168 


1.1180 


1.1191 


1.1202 


131 


1.1136 


1.1142 


1.1147 


1.1161 


1.1175 


1.1187 


1.1199 


1.1210 


1.1222 


1.1233 


128 


1.1167 


1.1173 


1.1179 


1.1192 


1.1206 


1.1218 


1.1231 


1.1242 


1.1253 


1.1264 


125 


1.1198 


1.1204 


1.1210 


1.1223 


1.1237 


1.1248 


1.1262 


1.1273 


1.1285 


1.1296 


122 


1.1229 


1.1235 


1.1241 


1.1255 


1.1268 


1.1281 


1.1293 


1.1294 


1.1316 


1.1327 


119 


1.1260 


1.1266 


1.1272 


1.1286 


1.1299 


1.1311 


1.1324 


1.1336 


1.1347 


1.1358 


116 


1.1292 


1.1298 


1.1303 


1.1317 


1.1331 


1.1343 


1.1355 


1.1366 


1.1378 


1.1389 


113 


1.1323 


1.1329 


1.1334 


1.1348 


1.1362 


1.1374 


1.1387 


1.1398 


1.1409 


1.1420 


110 


1.1354 


1.1360 


1.1366 


1.1374 


1.1393 


1.1405 


1.1418 


1.1429 


1.1441 


1.1452 


107 


1.1385 


1.1391 


11397 


1.1411 


1.1424 


1.1436 


1.1449 


1.1460 


1.1472 


1.1483 


104 


1.1416 


1.1422 


1.1428 


1.1442 


1.1455 


1.1467 


1.1480 


1.1491 


1.1503 


1.1514 


101 


1.1447 


1.1453 


1.1459 


1.1473 


1.1486 


1.1498 


1.1511 


1.1523 


1.1534 


1.1545 


98 


1.1479 


1.1485 


1.1490 


1.1504 


1.1518 


1.1530 


1.1542 


1.1554 


1.1565 


1.1576 


95 


1.1510 


1.1516 


1.1521 


1.1535 


1.1549 


1.1561 


1.1574 


1.1583 


1.1596 


1.1607 


92 


1.1541 


1.1547 


1.1553 


1.1566 


1.1580 


1.1592 


1.1605 


1.1616 


1.1628 


1.1639 


89 


1.1572 


1.1578 


1.1584 


1.1598 


1.1611 


1.1623 


1.1636 


1.1647 


1.1659 


1.1670 


86 


1.1603 


1.1609 


1.1615 


1.1629 


1.1642 


1.1654 


1.1667 


1.1678 


1.1690 


1.1701 


83 


1.1634 


1.1640 


1.1646 


1.1660 


1.1673 


1.1685 


1.1698 


1.1709 


1.1721 


1.1732 


80 


1.1665 


1.1671 


1.1677 


1.1691 


1.1704 


1.1716 


1.1729 


1.1741 


1.1752 


1.1763 


77 


1.1696 


1.1702 


1.1708 


1.1722 


1.1735 


1.1747 


1.1760 


1.1772 


1.1783 


1.1794 


74 


1.1728 


1.1734 


1.1739 


1.1753 


1.1767 


1.1779 


1.1791 


1.1803 


1.1814 


1.1825 


71 


1.1759 


1.1765 


1.1770 


1.1784 


1.1798 


1.1810 


1.1823 


1.1834 


1.1845 


1.1856 


68 


1.1790 


1.1796 


1.1802 


1.1815 


1.1829 


1.1841 


1.1854 


1.1865 


1.1877 


1.1888 


65 


1.1821 


1.1827 


1.1833 


1.1846 


1.1860 


1.1872 


1.1885 


1.1896 


1.1908 


1.1919 


62 


1.1852 


1.1858 


1.1864 


1.1877 


1.1891 


1.1903 


1.1916 


1.1927 


1.1939 


1.1.950 


59 


1.1883 


1.1889 


1.1895 


1.1909 


1.1922 


1.1934 


1.1947 


1.1958 


1.1970 


1.2981 


56 


1.1914 


1.1920 


1.1926 


1.1940 


1.1953 


1.1965 


1.1978 


1.1989 


1.2001 


1.2012 


53 


1.1945 


1.1951 


1.1957 


1.1971 


1.1984 


1.1996 


1.2009 


1.2020 


1.2032 


1.2043 


50 


1.1976 


1.1982 


1.1988 


1.2002 


1.2015 


1.2027 


1.2040 


1.2052 


1.2063 


1.2074 


47 


1.2007 


1.2013 


1.2019 


1.2033 


1.2046 


1.2058 


1.207l| 1.2083 


1.2094 


1.2105 


44 


1.2039 


1.2044 


1.2050 


1.2064 


1.2078 


1.2090 


1.21021 1.2114 


1.2125 


1.2136 


41 


1.2070 


1.2076 


1.2081 


1.2095 


1.2109 


1.2121 


1.2133 1.2145 


1.2156 


1.2167 


38 


1.2101 


1.2107 


1.2112 


1.2126 1.2140 


1.2162 1.2164 1.2176 


1.2187 


1.2198 


35 


1.2132 


1.2138 


1.2143 


1.21571 1.2171 


1.21831 1.21961 1.2207 


1.2218 


1.2229 


32 


1.2163 


1.2169 


1.2175 


1.2188! 1.2202 


1.2214| 1.22271 1.2239 


1.2249 


1.2260 



FACTORS OF EVAPORATION. 



1403 





Table of 


facto 


rs of 


Evaporati 


on. 






Gauge 


















Pressure. 


100 


105 


115 


125 


135 


145 


155 


165 


185 


Temp, of 
Feed. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


212° F, 


1.0397 


1.0407 


1.0427 


1.0445 


1.0462 


1.0478 


1.0493 


1.0509 


1.0536 


209 


1.0429 


1.0438 


1.0458 


1.0476 


1.0493 


1.0509 


1.0524 


1.0540 


1.0567 


206 


1.0460 


1.0470 


1.0489 


1.0510 


1.0527 


1.0543 


1.0558 


1.0574 


1.0601 


203 


1.0492 


1.0502 


1.0521 


1.0540 


10557 


1.0573 


1.0588 


1.0604 


1.0631 


200 


1.0523 


1.0533 


1.0552 


1.0571 


1.0588 


1.0604 


1.0619 


1.0635 


1.0662 


197 


1.0555 


1.0565 


1.0584 


1.0602 


1.0619 


1.0635 


1.0650 


1.0666 


1.0693 


194 


1.0586 


1.0596 


1.0615 


1.0635 


1.0652 


1.0668 


1.0683 


1.0699 


1.0726 


191 


1.0617 


1.0627 


1.0647 


1.0665 


1.0682 


1.0698 


1.0713 


1.0729 


1.0756 


188 


1.0649 


1.0659 


1.0678 


1.0696 


1.0713 


1.0729 


1.0744 


1.0760 


1.0787 


185 


1.0680 


1.0690 


1.0709 


±\0728 


1.0745 


1.0761 


1.0776 


1.0792 


1.0819 


182 


1.0712 


1.0722 


1.0741 


1.0759 


1.0776 


1.0792 


1-0807 


1.0823 


1.0850 


179 


1.0743 


1.0753 


1.0772 


1-0790 


1.0807 


1.0823 


1.0838 


1.0854 


1.0881 


176 


1.0774 


1.0784 


1.0803 


1.0822 


1.0839 


1.0855 


1.0870 


1.0886 


1.0913 


173 


1.0806 


1.0816 


1.0835 


1.0853 


1.0870 


1.0886 


1.0901 


1.0917 


1.0944 


170 


1.0837 


1.0847 


1.0866 


1.0884 


1.0901 


1.0917 


1.0932 


1.0948 


1.0975 


167 


1.0868 


1.0878 


1.0897 


1.0916 


1.0933 


1.0949 


1.0964 


1.0980 


1.1007 


164 


1.0900 


1.0910 


1.0929 


1.0946 


1.0963 


1.0979 


1.0994 


1.1010 


1.1037 


161 


1.0931 


1.0941 


1.0960 


1.0979 


1.0996 


1.1012 


1.1027 


1.1043 


1.1070 


158 


1.0962 


1.0972 


1.0991 


1.1010 


1.1027 


1.1043 


1.1058 


1.1074 


1.1101 


155 


1.0993 


1.1003 


1.1023 


1.1041 


1.1058 


1.1074 


1.1089 


1.1105 


1.1132 


152 


1.1025 


1.1035 


1.1054 


1.1073 


1.1090 


1.1107 


1-1122 


1.1138 


1.1165 


149 


1.1056 


1.1066 


1.1085 


1.1103 


1.1120 


1.1136 


1.1151 


1.1167 


1.1194 


146 


1.1087 


1.1097 


1.1116 


1.1135 


1.1152 


1.1168 


1.1183 


1.1199 


1.1226 


143 


1.1118 


1.1129 


1.1148 


1.1166 


1.1183 


1.1199 


1.1214 


1.1230 


1.1257 


140 


1.1150 


1.1160 


1.1179 


1.1197 


1.1214 


1.1230 


1.1245 


1.1261 


1.1288 


137 


1.1181 


1.1191 


1.1210 


1.1228 


1.1245 


1.1262 


1.1277 


1.1293 


1.1320 


134 


1.1212 


1.1222 


1.1241 


1.1260 


1.1277 


1.1293 


1.1308 


1.1324 


1.1351 


131 


1.1243 


1.1253 


1.1273 


1.1291 


1.1308 


1.1324 


1.1339 


1.1355 


1.1382 


128 


1.1275 


1.1285 


1.1304 


1.1322 


1,1339 


1.1355 


1.1370 


1.1386 


1.1413 


125 


1.1306 


1.1316 


1.1335 


1.1353 


1.1370 


1.1386 


1.1401 


1.1417 


1.1444 


122 


11337 


1.1347 


1.1366 


1.1384 


1.1401 


1.1417 


1.1438 


1.1448 


1.1475 


119 


1.1368 


1.1378 


1.1397 


1.1415 


1.1432 


1.1449 


1.1464 


1.1480 


1.1507 


116 


1.1399 


1.1409 


1.1429 


1.1447 


1.1464 


1.1480 


1.1495 


1.1511 


1.1538 


113 


1.1431 


1.1441 


1.1460 


1.1478 


1.1495 


1.1511 


1.1526 


1.1542 


1.1569 


110 


1.1462 


1.1472 


1.1491 


1.1509 


1.1516 


1.1542 


1.1557 


1.1573 


1.1600 


107 


1.1493 


1.1503 


1.1522 


1.1540 


1.1557 


1.1573 


1.1588 


1.1604 


1.1631 


104 


1.1524 


1.1534 


1.1553 


1.1571 


1.1588 


1.1605 


1.1619 


1.1635 


1.1662 


• 101 


1.1555 


1.1565 


1.1584 


1.1602 


1.1620 


1.1636 


1.1652 


1.1668 


1.1695 


98 


1.1586 


1.1596 


1.1616 


1.1634 


1.1651 


1.1667 


1.1683 


1.1699 


1.1726 


95 


1.1618 


1.1628 


1.1647 


1.1665 


1.1682 


1.1698 


1.1713 


1.1729 


1.1756 


92 


1.1649 


1.1660 


1.1678 


1.1696 


1.1713 


1.1729 


1.1744 


1.1760 


1.1787 


89 


1.1680 


1.1690 


1.1709 


1.1727 


1.1744 


1.1760 


1.1775 


1.1791 


1.1818 


86 


1.1711 


1.1721 


1.1740 


1.1758 


1.1775 


1.1791 


1.1806 


1.1822 


1.1849 


83 


1.1742 


1.1752 


1.1771 


1.1789 


1.1806 


1.1823 


1.1837 


1.1853 


1.1880 


80 


1.1773 


1.1783 


1.1802 


1.1820 


1.1837 


1.1854 


1.1869 


1.1885 


1.1912 


77 


1.1804 


1.1814 


1.1834 


1.1852 


1.1869 


1.1885 


1.1900 


1.1916 


1.1943 


74 


1.1835 


1.1845 


1.1865 


1.1883 


1.1900 


1.1916 


1.1932 


1.1948 


1.1975 


71 


1.1867 


1.1877 


1.1896 


1.1914 


1.1931 


1.1947 


1.1961 


1.1977 


1.2004 


68 


1.1898 


1.1908 


1.1927 


1.1945 


1.1962 


1.1978 


1.1993 


1.2009 


1.2036 


65 


1.1929 


1.1939 


1.1958 


1.1976 


1.1993 


1.2009 


1.2024 


1.2040 


1.2067 


62 


1.1960 


1.1970 


1.1989 


1.2007 


1.2024 


1.2040 


1.2055 


1.2071 


1.2098 


59 


1.1991 


1.2001 


1.2020 


1.2038 


1.2055 


1.2071 


1.2086 


1.2102 


1.2129 


56 


1.2022 


1.2032 


1.2051 


1.2069 


1.2086 


1.2102 


1.2117 


1.2133 


1.2160 


53 


1.2053 


1.2063 


1.2082 


1.2100 


1.2117 


1.2134 


1.2148 


1.2164 


1.2191 


50 


1.2084 


1.2094 


1.2113 


1.2131 


1.2148 


1.2165 


1.2180 


1.2196 


1.2223 


47 


1.2115 


1.2125 


1.2144 


1.2163 


1.2180 


1.2196 


1.2211 


1.2227 


1.2254 


44 


1.2146 


1.2156 


1.2176 


1.2194 


1.2211 


1.2227 


1.2242 


1.2258 


1.2285 


41 


1.2177 


1.2187 


1.2207 


1.2225 


1.2242 


1.2258 


1.2273 


1.2289 


1.2316 


38 


1.2208 


1.2219 


1 2238 


1.2256 


1.2273 


1.2289 


1.2304 


1.2320 


1.2347 


35 


1.2240 


1.2250 


12269 


12287 


1.2304 


1.2320 


1.2335 


1.2351 


1.2378 


32 


1.2271 


1.2281 


1.2300 


1.2318 


1.2335 


1.2351 


1.2366 


1 .2382 


1.2409 



1403a 



FACTORS OF EVAPORATION. 





Table of factors of evaporation. 












W. Wallace Christie. 








Gauge 
Pressure. 


200 


215 


230 


245 


260 


275 


290 


300 


Temp, of 


lbs. 


lbs. 


lbs. 


lbs. 


I lbs. 


lbs. 


lbs. 


lbs. 


Feed. 


















212° F. 


1:0555 


1.0574 


1.0591 


1.0605 


1.0622 


1.0639 


1.0653 


1.0663 


209 


1.0586 


1.0605 


1.0622 


1.0639 


1.0654 


1.0670 


1.0684 


1.0694 


206 


1.0616 


1.0635 


1.0653 


1.0669 


1.0685 


1.0700 


1.0715 


1.0724 


203 


1.0648 


1.0668 


1.0684 


1.0701 


1.0717 


1.0732 


1.0746 


1.0756 


200. 


1.0680 


1.0699 


1.0716 


1.0733 


1.0749 


1.0764 


1.0779 


1.0788 


197 


1.0711 


1.0730 


1.0747 


1.0764 


1.0781 


1.0795 


1.0810 


1.0819 


194 


1.0743 


1.0762 


1.0779 


1.0796 


1.0813 


1.0827 


1.0842 


1.0851 


191 


1.0774 


1.0793 


1.0811 


1.0827 


1.0844 


1.0858 


1.0873 


1.0882 


188 


1.0806 


1.0825 


1.0843 


1.0859 


1.0875 


1.0890 


1.0905 


1.0914 


185 


1.0838 


1.0857 


1.0875 


1.0891 


1.0907 


1.0923 


1.0937 


1.0946 


182 


1.0869 


1.0888 


1.0906 


1.0923 


1.0938 


1.0954 


1.0968 


1.0977 


179 


1.0900 


1.0917 


1.0937 


1.0954 


1.0969 


1.0985 


1.0999 


1.1009 


176 


1.0932 


1.0950 


1.0968 


1.0985 


1 . 1000 


1.1016 


1.1030 


1 . 1040 


173 


1.0964 


1.0983 


1 . 1000 


1.1017 


1 . 1032 


1.1048 


1 . 1062 


1.1072 


170 


1.0995 


1.1014 


1.1031 


1.1048 


1 . 1063 


1.1079 


1 . 1093 


1.1103 


167 


1 . 1026 


1 . 1045 


1 . 1062 


1.1079 


1 . 1094 


1.1110 


1.1124 


1.1134 


164 


1.1057 


1.1076 


1.1093 


1.1110 


1.1126 


1.1141 


1 . 1155 


1.1165 


161 


1 . 1088 


1.1107 


1.1124 


1.1141 


1.1157 


1.1172 


1.1187 


1.1196 


158 


1.1120 


1.1139 


1.1156 


1.1173 


1.1189 


1.1204 


1.1219 


1 . 1228 


155 


1.1151 


1.1170 


1.1188 


1.1204 


1 . 1220 


1.1235 


1 . 1250 


1.1259 


152 


1.1182 


1 . 1201 


1.1219 


1 . 1235 


1.1251 


1.1266 


1.1281 


1 . 1290 


149 


1.1213 


1 . 1232 


1 . 1250 


1 . 1266 


1.1282 


1.1297 


1.1312 


1.1321 


146 


1.1245 


1.1264 


1.1282 


1.1298 


1.1314 


1.1329 


1.1344 


1.1353 


143 


1.1276 


1.1295 


1.1313 


1 . 1329 


1.1345 


1.1361 


1.1375 


1.1384 


140 


1.1308 


1 . 1326 


1.1344 


1.1360 


1.1376 


1 . 1392 


1.1406 


1.1415 


137 


1.1339 


1.1357 


1.1375 


1.1392 


1.1407 


1.1424 


1.1437 


1.1447 


134 


1.1371 


1.1389 


1.1407 


1 . 1424 


1 . 1438 


1.1456 


1.1469 


1.1479 


131 


1 . 1402 


1.1421 


1.1438 


1.1455 


1.1470 


1.1487 


1 . 1500 


1.1510 


128 


1.1433 


1 . 1452 


1 . 1469 


1.1486 


1.1501 


1.1518 


1.1532 


1.1541 


125 


1.1464 


1 . 1483 


1.1500 


1.1517 


1.1532 


1.1549 


1.1563 


1.1572 


122 


1 . 1496 


1.1515 


1 . 1532 


1.1549 


1 . 1564 


1 . 1580 


1.1595 


1.1604 


119 


1.1527 


1.1546 


1.1563 


1.1580 


1 . 1596 


1.1611 


1 . 1626 


1.1635 


116 


1.1559 


1.1577 


1 . 1594 


1.1611 


1.1627 


1 . 1642 


1.1657 


1.1666 


113 


1.1589 


1.1608 


1.1626 


1.1642 


1.1658 


1.1673 


1.1688 


1.1697 


110 


1 . 1620 


1.1639 


1.1657 


1 . 1673 


1.1689 


1.1704 


1.1719 


1.1728 


107 


1.1651 


1.1670 


1.1688 


1.1704 


1.1720 


1.1735 


1.1750 


1.1760 


104 


1.1682 


1.1701 


1.1719 


1.1735 


1.1751 


1.1766 


1.1781 


1.1790 


101 


1.1713 


1.1732 


1.1750 


1.1766 


1.1782 


1.1797 


1.1812 


1.1821 " 


98 


1 . 1744 


1 . 1763 


1.1781 


1.1797 


1.1813 


1.1829 


1.1843 


1.1853 


95 


1.1776 


1 . 1794 


1.1812 


1.1829 


1 . 1844 


1 . 1860 


1 . 1874 


1.1884 


92 


1.1807 


1.1826 


1 . 1843 


1.1860 


1.1875 


1.1891 


1.1905 


1.1915 


89 


1.1838 


1 . 1857 


1.1874 


1.1891 


1.1906 


1.1922 


1.1936 


1.1946 


86 


1 . 1869 


1 . 1888 


1.1905 


1.1922 


1 . 1937 


1.1953 


1.1967 


1.1977 


83 


1 . 1900 


1.1919 


1.1936 


1.1953 


1.1968 


1.1984 


1.1999 


1.2008 


80 


1.1931 


1 . 1950 


1.1967 


1.1984 


1.2000 


1.2015 


1.2030 


1.2039 


77 


1.1962 


1:1981 


1.1998 


1.2015 


1.2031 


1.2046 


1.2061 


1.2070 


74 


1 . 1993 


1.2012 


1.2029 


1.2046 


1.2062 


1.2077 


1.2092 


1.2101 


71 


1.2024 


1.2043 


1.2061 


1.2077 


1.2092 


1.2108 


1.2123 


1.2132 


68 


1 . 2055 


1.2074 


1.2092 


1.2108 


1.2124 


1.2139 


1.2154 


1.2163 


65 


1.2087 


1.2105 


1.2123 


1.2139 


1.2155 


1.2170 


1.2185 


1.2194 


62 


1.2118 


1.2136 


1.2154 


1.2172 


1.2186 


1.2201 


1.2216 


1.2225 


59 


1.2149 


1.2167 


1.2185 


1.2202 


1.2217 


1.2233 


1.2247 


1.2256 


56 


1.2180 


1.2198 


1.2216 


1.2232 


1.2248 


1.2264 


1.2278 


1.2288 


53 


1.2211 


1.2229 


1.2247 


1.2264 


1.2279 


1.2295 


1.2309 


1.2319 


50 


1.2242 


1.2261 


1.2278 


1.2295 


1.2310 


1.2326 


1.2340 


1.2350 


47 


1.2273 


1.2292 


1.2309 


1 . 2326 


1.2341 


1.2357 


1.2371 


1.2381 


44 


1.2304 


1 . 2323 


1 . 2340 


1.2357 


1.2372 


1.2388 


1.2402 


1.2412 


41 


1.2335 


1.2354 


1.2371 


1 . 2388 


1.2403 


1.2419 


1.2433 


1.2443 


38 


1.2366 


1.2385 


1 . 2402 


1.2419 


1.2434 


1.2450 


1.2464 


1.2474 


35 


1.2397 


1.2416 


1.2433 


1.2450 


1 . 2465 


1.2481 


1.2496 


1.2505 


32 


1 . 2428 


1.2447 


1 . 2464 


1.2481 


1.2497 


1.2512 


1.2527 


1.2536 



FACTORS OF EVAPORATION. 



1403b 





Table of factors of Evaporation. — Continued, 


y 


Gauge 
Pressure. 
Temp, of 

Feed. 



Lbs. 


10 
Lbs. 


20 
Lbs. 


30 
Lbs. 


40 
Lbs. 


45 
Lbs. 


50 
Lbs. 


52 
Lbs. 


54 
Lbs. 


300° F. 

295 

290 

287 

284 

281 

278 

275 

272 

269 

266 

263 

260 

257 

254 

251 

248 

245 

242 

239 

236 

233 

230 

227 

224 

221 

218 

215 


0.907 
0.912 
0.917 
0.921 
0.924 
0.927 
0.930 
0.933 
0.936 
0.940 
0.943 
0.946 
0.949 
0.952 
0.955 
0.958 
0.961 
0.964 
0.967 
0.970 
0.974 
0.977 
0.980 
0.983 
0.986 
0.989 
0.993 
0.997 


0.915 
0.920 
0.926 
0.930 
0.933 
0.936 
0.939 
0.942 
0.945 
0.948 
0.951 
0.955 
0.958 
0.961 
0.964 
0.967 
0.970 
0.974 
0.977 
0.981 
0.984 
0.987 
0.990 
0.993 
0.996 
0.999 
1.002 
1.005 


0.922 
0.927 
0.932 
0.936 
0.939 
0.942 
0.945 
0.948 
0.951 
0.954 
0.958 
0.961 
0.964 
0.967 
0.970 
0.974 
0.977 
0.980 
0.983 
0.986 
0.989 
0.992 
0.996 
0.999 
1.002 
1.005 
1.008 
1.010 


0.926 
0.932 
0.937 
0.940 
0.944 
0.947 
0.950 
0.953 
0.956 
0.959 
0.963 
0.966 
0.969 
0.972 
0.975 
0.978 
0.982 
0.985 
0.988 
0.991 
0.994 
0.998 
1.001 
1.004 
1.007 
1.010 
1.013 
1.016 


0.930 
0.936 
0.941 
0.945 
0.948 
.0.951 
0.954 
0.958 
0.961 
0.964 
0.968 
0.971 
0.974 
0.977 
0.980 
0.983 
0.987 
0.990 
0.993 
0.995 
0.998 
1.001 
1.005 
1.008 
1.011 
1.014 
1.017 
1.020 


0.932 
0.937 
0.943 
0.946 
0.949 
0.953 
0.956 
0.959 
0.962 
0.966 
0.969 
0.972 
0.975 
0.978 
0.981 
0.984 
0.987 
0.990 
0.994 
0.997 
1.000 
1.003 
1.007 
1.010 
1.013 
1.016 
1.019 
1.022 


0.934 
0.939 
0.944 
0.948 
0.951 
0.954 
0.957 
0.960 
0.963 
0.967 
0.970 
0.973 
0.976 
0.979 
0.983 
0.986 
0.989 
0.992 
0.995 
0.999 
1.002 
1.005 
1.008 
1.011 
1.014 
1.017 
1.021 
1.024 


0.9347 
0.9399 
0.9453 
0.9485 
0.9517 
0.9548 
0.9580 
0.9612 
0.9642 
0.9675 
0.9708 
0.9738 
0.9770 
0.9801 
0.9833 
0.9865 
0.9897 
0.9929 
0.9960 
0.9992 
1.0024 
1.0055 
1.0087 
1.0118 
1.0149 
1.0180 
1.0212 
1.0244 


0.9353 
0.9406 
0.9459 
0.9492 
0.9524 
0.9554 
0.9586 
0.9618 
0.9648 
0.9681 
0.9714 
0.9744 
0.9776 
0.9807 
0.9840 
0.9872 
0.9904 
0.9935 
0.9966 
1.0000 
1.0030 
1.0061 
1.0093 
1.0124 
1.0155 
1.0186 
1.0217 
1.0251 




56 
Lbs. 


58 
Lbs. 


60 
Lbs. 


65 
Lbs. 


70 
Lbs. 


75 
Lbs. 


80 
Lbs. 


85 
Lbs. 


90 
Lbs. 


95 
Lbs. 


300° F. 

295 

290 

287 

284 

281 

278 

275 

272 

269 

266 

263 

260 

257 

254 

251 

248 

245 

242 

239 

236 

233 

230 

227 

224 

221 

218 

215 


0.9359 
0.9412 
0.9465 
0.9498 
0.9530 
0.9561 
0.9592 
0.9624 
0.9654 
0.9687 
0.9720 
0.9750 
0.9782 
0.9814 
0.9846 
0.9877 
0.9910 
0.9941 
0.9972 
1.0004 
1.0036 
1.0067 
1.0099 
1.0130 
1.0161 
1.0193 
1.0225 
1.0257 


0.9365 
0.9418 
0.9472 
0.9504 
0.9536 
0.9567 
0.9598 
0.9630 
0.9660 
0.9693 
0.9727 
0.9757 
0.9789 
0.9820 
0.9853 
0.9884 
0.9916 
0.9948 
0.9979 
1.0011 
1.0042 
1.0073 
1.0106 
1.0137 
1.0168 
1.0199 
1.0231 
1.0263 


0.9370 
0.9423 
0.9477 
0.9509 
0.9541 
0.9572 
0.9603 
0.9635 
0.9665 
0.9699 
0.9732 
0.9762 
0.9794 
0.9825 
0.9857 
0.9889 
0.9921 
0.9953 
0.9984 
1.0016 
1.0048 
1.0089 
1.0111 
1.0142 
1.0173 
1.0204 
1.0236 
1.0268 


O.c 
0.1 
0.1 

0/ 
0/ 
0.1 
0.1 
0.! 
0.1 
0. 
0. 
0.1 
0. 
0. 
0. 
0. 
0. 
0. 
0. 

1. 
1. 
1. 
1. 
1 

1. 
1. 

1. 


)385 
)438 
)492 
)524 
)556 
)587 
)618 
)650 
)680 
)713 
)746 
)776 
)808 
)840 
?872 
3904 
3936 
)968 
3999 
3030 
3062 
3094 
3125 
3156 
0187 
0218 
0251 
0283 


0.93< 
0.94, 
0.95( 
0.951 
0.95( 
0.96( 
0.96 
0.96 
0.96 
0.97 
0.97 
0.97 
0.98 
0.98 
0.98 
0.99 
0.99 
0.99 
1.00 
1.00 
1.00 
1.01 
1.01 
1.01 
1.02 
1.02 
1.02 
1.02 


18 
51 
)5 
M 
39 
)0 
Jl 
33 
U 
26 
30 
30 
22 
53 
So 
17 
19 
SO 
11 
43 
76 
V 
39 
70 
01 
32 
64 
•6 


0.9411 
0.9464 
0.9517 
0.9550 
0.9582 
0.9613 
0.9644 
0.9676 
0.9706 
0.9739 
0.9772 
0.9802 
0.9834 
0.9865 
0.9897 
0.9930 
0.9962 
0.9993 
1.0024 
1.0056 
1.0088 
1.0119 
1.0151 
1.0182 
1.0213 
1.0244 
1.0276 
1.0309 


0.9423 
0.9476 
0.9530 
0.9562 
0.9594 
0.9625 
0.9656 
0.9688 
0.9718 
0.9752 
0.9784 
0.9815 
0.9847 
0.9878 
0.9910 
0.9942 
0.9974 
1.0005 
1.0036 
1.0068 
1.0100 
1.0132 
1.0134 
1.0195 
1.0226 
1.0257 
1.0289 
1.0321 


0.9435 
0.9487 
0.9541 
0.9573 
0.9605 
0.9636 
0.9667 
0.9700 
0.9730 
0.9763 
0.9796 
0.9826 
0.9858 
0.9890 
0.9921 
0.9953 
0.9985 
1.0016 
1.0047 
1.0080 
1.0112 
1.0143 
1.0175 
1.0206 
1.0237 
1.0269 
1.0300 
1.0332 


0.9446 
0.9499 
0.9553 
0.9585 
0.9617 
0.9648 
0.9679 
0.9711 
0.9741 
0.9774 
0.9807 
0.9837 
0.9869 
0.9901 
0.9933 
0.9965 
0.9997 
1.0028 
1.0059 
1.0091 
1.0123 
1.0154 
1.0186 
1.0217 
1.0248 
1.0280 
1.0312 
1.0344 


0.9456 
0.9509 
0.9563 
0.9595 
0.9627 
0.9658 
0.9690 
0.9721 
0.9751 
0.9785 
0.9818 
0.9848 
0.9880 
0.9911 
0.9943 
0.9975 
1.0007 
1.0038 
1.0069 
1.0102 
1.0134 
1.0165 
1.0197 
1.0228 
1.0259 
1.0290 
1.0322 
1.0354 



1403c 



STEAM. 



Table of Factors of Evaporation. — Continued. 



Gauge 




















Pressure. 


100 


105 


115 


125 


135 


145 


155 


165 


185 


Temp, of 
Feed. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


300° F. 


0.9467 


0.9477 


0.9498 


0.9514 


0.9532 


0.9548 


0.9564 


0.9579 


0.9606 


295 


0.9520 


0.9530 


0.9551 


0.9567 


0.9585 


0.9601 


0.9617 


0.9631 


0.9659 


290 


0.9573 


0.9584 


0.9604 


0.9621 


0.9639 


0.9655 


0.9671 


0.9685 


0.9713 


287 


0.9605 


0.9616 


0.9636 


0.9653 


0.9671 


0.9687 


0.9703 


0.9717 


0.9745 


284 


0.9637 


0.9648 


0.9669 


0.9685 


0.9703 


0.9719 


0.9735 


0.9749 


0.9777 


281 


0.9669 


0.9679 


0.9700 


0.9716 


0.9734 


0.9750 


0.9766 


0.9780 


0.9808 


278 


0.9700 


0.9710 


0.9731 


0.9747 


0.9765 


0.9781 


0.9797 


0.9812 


0.9840 


275 


0.9732 


0.9742 


0.9763 


0.9779 


0.9797 


0.9813 


0.9829 


0.9844 


0.9872 


272 


0.9762 


0.9772 


0.9793 


0.9810 


0.9827 


0.9844 


0.9859 


0.9874 


0.9902 


269 


0.9795 


0.9805 


0.9826 


0.9842 


0.9860 


0.9877 


0.9892 


0.9907 


0.9935 


266 


0.9828 


0.9838 


0.9859 


0.9876 


0.9893 


0.9910 


0.9925 


0.9940 


0.9968 


263 


0.9858 


0.9868 


0.9889 


0.9906 


0.9923 


0.9940 


0.9955 


0.9970 


0.9998 


260 


0.9890 


0.9901 


0.9921 


0.9938 


0.9955 


0.9972 


0.9988 


1.0002 


1.0030 


257 


0.9921 


0.9932 


0.9952 


0.9969 


0.9986 


1.0003 


1.0019 


1.0033 


1.0061 


254 


0.9953 


0.9964 


0.9984 


1.0001 


1.0019 


1.0035 


1.0051 


1.0065 


1.0093 


251 


0.9985 


0.9996 


1.0017 


1.0033 


1.0051 


1.0067 


1.0083 


1.0097 


1.0125 


248 


1.0018 


1.0028 


1.0049 


1.0065 


1.0083 


1.0099 


1.0115 


1.0129 


1.0167 


245 


1.0049 


1.0059 


1.0080 


1.0096 


1.0114 


1.0130 


1.0146 


1.0160 


1.0188 


242 


1.0080 


1.0090 


1.0111 


1.0127 


1.0145 


1.0162 


1.0177 


1.0192 


1.0220 


239 


1.0112 


1.0122 


1.0143 


1.0159 


1.0177 


1.0194 


1.0209 


1.0224 


1.0252 


236 


1.0144 


1.0154 


1.0175 


1.0192 


1.0209 


1.0226 


1.0241 


1.0256 


1.0284 


233 


1.0175 


1.0185 


1.0206 


1.0223 


1.0240 


1.0257 


1.0272 


1.0287 


1.0315 


230 


1.0207 


1.0217 


1.0238 


1.0255 


1.0272 


1.0289 


1.0304 


1.0319 


1.0347 


227 


1.0238 


1.0248 


1.0269 


1.0286 


1.0303 


1.0320 


1 . 0335 


1.0350 


1.0378 


224 


1.0269 


1.0280 


1.0300 


1.0317 


1.0334 


1.0351 


1.0367 


1.0381 


1.0409 


221 


1.0300 


1.0311 


1.0331 


1.0348 


1.0365 


1.0382 


1.0398 


1.0412 


1.0440 


218 


1.0332 


1.0343 


1.0363 


1.0380 


1.0398 


1.0414 


1.0430 


1.0444 


1.0472 


215 


1.0364 


1.0375 


1.0395 


1.0412 


1.0430 


1.0446 


1.0462 


1.0476 


1.0504 



FACTORS OF EVAPORATION. 



1403d 



Table of factors of Evaporation. — Concluded. 



Gauge 


















Pressure. 


200 


215 


230 


245 


260 


275 


290 


300 


Temp, of 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Feed. 


















300 °F. 


0.9626 


0.9645 


0.9662 


0.9679 


0.9694 


0.9710 


0.9724 


0.9734 


295 


0.9679 


0.9697 


0.9715 


0.9732 


0.9747 


0.9763 


0.9777 


0.9787 


290 


0.9733 


0.9751 


0.9769 


0.9786 


0.9801 


0.9817 


0.9831 


0.9840 


287 


0.9765 


0.9783 


0.9801 


0.9818 


0.9833 


0.9849 


0.9863 


0.9873 


284 


0.9797 


0.9S16 


0.9833 


0.9850 


0.9865 


0.9881 


0.9895 


0.9905 


281 


0.9828 


0.9847 


0.9864 


0.9881 


0.9896 


0.9912 


0.9926 


0.9936 


278 


0.9859 


0.9878 


0.9895 


0.9912 


0.9927 


0.9943 


0.9957 


0.9967 


275 


0.9891 


0.9910 


0.9927 


0.9944 


0.9959 


0.9975 


0.9989 


0.9999 


272 


0.9921 


0.9940 


0.9958 


0.9974 


0.9990 


1.0005 


1.0020 


1.0029 


269 


0.9954 


0.9973 


0.9991 


1.0007 


1.0023 


1.0038 


1.0053 


1.0063 


266 


0.9987 


1.0006 


1.0024 


1.0040 


1.0056 


1.0071 


1.0086 


1.0095 


263 


1.0017 


1.0036 


1.0054 


1.0070 


1.0086 


1.0102 


1.0116 


1.0125 


260 


1.0049 


1.0058 


1.0086 


1.0103 


1.0118 


1.0133 


1.0148 


1.0157 


257 


1.0081 


1.0099 


1.0117 


1.0134 


1.0149 


1.0164 


1.0179 


1.0188 


254 


1.0113 


1.0132 


1.0149 


1.0166 


1.0181 


1.0197 


1.0211 


1.0221 


251 


1.0145 


1.0164 


1.0181 


1.0198 


1.0213 


1.0229 


1.0243 


1.0253 


248 


1.0177 


1.0196 


1.0213 


1.0230 


1.0245 


1.0261 


1.0275 


1.0285 


245 


1.0208 


1.0227 


1.0244 


1.0261 


1.0276 


1.0292 


1.0306 


1.0316 


242 


1.0239 


1.0258 


1.0275 


1.0293 


1.0308 


1.0323 


1.0337 


1.0347 


239 


1.0271 


1.0290 


1.0307 


1.0324 


1.0340 


1.0355 


1.0370 


1.0379 


236 


1.0303 


1.0322 


1.0340 


1.0356 


1.0372 


1.0387 


1.0402 


1.0411 


233 


1.0334 


1.0353 


1.0371 


1.0387 


1.0403 


1.0418 


1.0433 


1.0442 


230 


1.0367 


1.0385 


1.0403 


1.0419 


1.0435 


1.0450 


1.0465 


1.0474 


227 


1.0398 


1.0416 


1.0434 


1.0450 


1.0466 


1.0482 


1.0496 


1.0505 


224 


1.0429 


1.0447 


1.0465 


1.0482 


1.0497 


1.0513 


1.0527 


1.0536 


221 


1.0460 


1.0478 


1.0496 


1.0512 


1.0528 


1.0544 


1.0558 


1.0567 


218 


1.0492 


1.0511 


1.0528 


1.0545 


1.0560 


1.0576 


1.0590 


1.0600 


215 


1.0524 


1.0543 


1.0562 


1.0577 


1.0592 


1.0608 


1.0622 


1.0632 



PROPERTUS OF SiTlRlTEI) ITEAM. 

(W. W. Christie, M.E.) 



e 

° si 


Sf'oS 


0) 

.• 6 

*x* hi 

o g 

SPLH 

H 


Heat Units in one Pound 
above 32° F. 


Volume. 


« o 




1* 

.a* 

*3 


cot A 
v hi G 

3«*« 


1&A 


Relative 


s Specific 


oo 


g* 

go 

> 


Cu. Ft. 

in 1 Cu. 

Ft. of 

Water. 


Cu. Ft. 
in one 
Lb. of 

Steam. 


-ail 

JqQQ 


29.74 
29.72 
29.71 
29.70 


.089 
.096 
.104 
.112 


32 
34 
36 
38 




2 
4 
6 


1092.7 
1090.37 
1088.98 
1087.59 


1092.7 
1092.37 
1092.98 
1093.59 


208080 
193180 
179380 
166380 


3387 
3138 
2910 
2700 


.000295 
318 
344 
370 


29.68 
29.65 
29.63 
29.61 


.122 
.132 
.142 
.152 


40 
42 
44 
46 


8 
10 
12 
14 


1086.20 
1084.81 
1083.41 
1082.02 


1094.20 
1094.81 
1095.41 
1096.02 


154330 
143220 
133120 
123840 


2506 
2328 
2164 
2013 


399 
429 
462 
496 


29.59 
29.56 
29.54 
29.51 


.164 
.176 
.190 
.205 


48 
50 
52 
54 


16 
18 
20 
22 


1080.63 
1079.25 
1077.86 
1076.47 


1096.63 
1097.25 
1097.86 
1098.47 


115490 

107630 

100330 

93680 


1874 
1745 
1626 
1516 


533 
573 
615 
659 


29.47 
29.44 
29.40 
29.37 


.220 
.236 
.254 
.273 


56 
58 
60 
62 


24 
26 
28 
30 


1075.08 
1073.69 
1072.31 
1070.92 


1099.08 
1099.69 
1100.31 
1100.92 


87500 
81740 
76370 
71330 


1415 
1321 
1234 
1153 


706 
757 
810 
867 


29.33 
29.28 
29.24 
29.19 


.292 
.313 
.335 
.359 


64 
66 
68 
70 


32 
34 
36 
38 


1069.53 
1068.14 
1066.75 
1065.35 


1101.53 
1102.14 
1102.75 
1103.35 


66630 
62290 
58340 
54660 


1078 
1009 
944.7 
885.0 


927 

991 

.001059 

1130 


29.14 
29.09 
29.03 
28.96 


.385 
.411 
.440 
.470 


72 
74 
76 

78 


40 
42 
44 
46 


1063.96 
1062.57 
1061.18 
1059.79 


1103.96 
1104.57 
1105.18 
1105.79 


51210 
48000 
45060 
42280 


829.5 
777.9 
729.9 
685.2 


1205 
1286 
1370 
1459 


28 90 
28.83 
28.76 
28.68 


.502 
.535 
.571 
.609 


80 

82 
84 
86 


48 
50 
52 
54 


1058.40 
1057.01 
1055.62 
1054.22 


1106.40 
1107.01 
1107.62 
1108.23 


39690 
37320 
35100 
33030 


643.8 
605.0 
568.8 
535.2 


1553 
1653 
1758 
1869 


28.60 
28.51 
28.42 
28.32 


.650 
.692 
.738 

.785 


88 
90 
92 
94 


56 
58 
60 
62 


1052.83 
1051.44 
1050.05 
1048.66 


1108.84 
1109.45 
1110.06 
1110.67 


31100 
29290 
27600 
26020 


503.7 
474.6 
447.1 
421.5 


1985 

.002107 

2237 

2372 


28.22 
28.11 
28.00 
27.89 


.834 

.887 

.943 

1.001 


96 

98 

100 

102 


64 
66 
68 
70 


1047.27 
1045.87 
1044.48 
1043.08 


1111.28 
1111.89 
1112.50 
1113.10 


24540 
23140 
21830 
20620 


397.5 
375.1 
354.0 
334.5 


2516 
2666 
2824 
2900 


27.76 
27.63 
27.49 
27.34 


1.062 
1.126 
1.193 
1.265 


104 
106 
108 
110 


72 
74 
76 

78 


1041.69 
1040.29 
1038.90 
1037.52 


1113.71 
1114.32 
1114.93 
1115.55 


19500 
18460 
17470 
16520 


316.1 
298.8 
282.7 
267.5 


.003163 
3347 
3537 
3738 


27.19 
27.03 
26.86 
26.68 


1.341 
1.421 
1.504 
1.591 


112 
114 
116 
118 


80 

82 
84 
86 


1036.12 
1034.74 
1033.35 
1031.94 


1116.16 
1116.78 
1117.39 
1117.99 


15640 
14820 
14050 
13320 


253.3 
239.9 
227.3 
215.5 


3948 

004168 

4399 

4640 


26.49 
26.30 


1.682 
1.779 


120 
122 


88 
90 


1030.55 
1029.16 


1118.60 
1119.21 


12630 
11980 


204.4 
193.9 1 


4892 
005156 



1404 



PROPERTIES OF SATtHATED §TE AHf . — Continued. 



m 

5 


« 02 (h 

■gi* 

n 




Heat Units in one Pound 
above 32° F. 


Volume. 


a o 
o 


.3 

.sg 


* • 




Ill's 


Rela- 
tive. 


Specific 




Cu. Ft. 
inlCu. 
Ft. of 
Water. 


Cu. Ft. 
in one 
Lb. of 
Steam. 


■Sf§! 

'SOW 


26.09 
25.88 
25.65 
25.41 


1.879 
1.984 
2.096 
2.213 


124 
126 
128 
130 


92 
94 
96 

98 


1027.76 
1026.37 
1024.97 
1023.58 


1119.82 
1120.43 
1121.04 
1121.65 


11370 

10800 

10265 

9760 


184.1 
174.8 
166.1 
157.8 


.005432 
5720 
6020 
6336 


25.17 
24.91 
24.64 
24.36 


2.335 
2.461 
2.594 
2.732 


132 

134 
136 
138 


100 
102 
104 
106 


1022.18 
1020.79 
1019.39 
1018.00 


1122.26 

1122.87 
1123.48 
1124.09 


9276 
8826 
8401 
7991 


150.1 

142.8 
135.8 
129.3 


6664 
7005 
7361 
7732 


24.06 
23.75 
23.43 
23.09 


2.876 
3.029 
3.188 
3.353 


140 
142 
144 
146 


108.1 
110.1 
112.1 
114.1 


1016.60 
1015.20 
1013.81 
1012.41 


1124.70 
1125.31 
1125.92 
1126.53 


7613 
7258 
6920 
6595 


123.2 
117.3 
111.8 
106.6 


8120 
8522 
8942 
9379 


22.74 
22.37 
21.99 
21.59 


3.526 
3.707 
3.896 
4.090 


148 
150 
152 
154 


116.1 

118.1 
120.1 
122.1 


1011.01 
1009.61 
1008.22 
1006.82 


1127.14 
1127.75 
1128.36 
1128.97 


6290 
6004 
5734 
5477 


101.7 
97.03 
92.61 

88.43 


.009833 
.01031 
.01080 
.01131 


21.17 
20.74 
20.29 
19.82 


4.295 
4.507 
4.729 
4.960 


156 
158 
160 
162 


124.1 
126.1 
128.1 
130.1 


1005.42 
1004.02 
1002.62 
1001.22 


1129.85 
1130.19 
1130.80 
1131.41 


5232 
5000 
4779 
4569 


84.47 
80.70 
77.14 
73.77 


.01184 
.01239 
.01296 
.01356 


19.33 
18.82 
18.29 
17.76 


5.200 
5.451 
5.711 
5.981 


164 
166 
168 
170 


132.2 
134.2 
136.2 
138.2 


999.82 
998.42 
997.02 
995.62 


1132.02 
1132.63 
1133.24 
1133.85 


4368 
4177 
3996 
3826 


70.56 
67.51 
64.62 
61.85 


.01417 
.01481 
.01548 
.01617 


17.16 
16.57 
15.95 
15.31 


6.262 
6.555 
6.857 
7.172 


172 
174 
176 
178 


140.2 
142.2 
144.2 
146.2 


994.22 
992.82 
991.42 
990.02 


1134.46 
1135.07 
1135.68 
1136.29 


3664 
3510 
3365 
3226 


59.25 
56.76 
54.40 
52.14 


.01688 
.01762 
.01838 
.01918 


14.64 
13.95 
13.23 
12.48 


7.500 
7.841 
8.194 
8.558 


180 

182 
184 
186 


148.2 
150.3 
152.3 
154.3 


983.62 
987.21 
985.81 
984.41 


1136.90 
1137.51 
1138.12 
1138.73 


3093 
2966 
2846 
2733 


50.01 
47.97 
46.06 
44.17 


.02000 
.02085 
.02172 
.02264 


11.71 

10.91 

10.08 

9.22 


8.936 
9.330 
9.738 
10.16 


188 
190 
192 
194 


156.3 
158.3 
160.3 
162.3 


983.00 
9S1.60 
980.20 
978.79 


1139.34 
1139.95 
1140.56 
1141.17 


2624 
2519 
2420 
2325 


42.41 
40.73 
39.13 
37.59 


.02358 
.02455 
.02556 
.C2660 


8.33 
7.40 
6.45 
5.46 


10.59 
11.05 
11.52 
12.00 


196 
198 
200 
202 


164.3 
166.4 
168.4 
170.4 


977.39 
975.98 
974.58 
973.17 


1141.78 
1142.39 
1143.00 
1143.61 


2234 
2147 
2064 
1985 


36.13 
34.73 
33.40 
32.13 


.02768 
.02879 
.02994 
.03112 


4.44 
3.38 
2.28 
1.15 


12.50 
13.02 
13.56 
14.12 


204 
206 
208 
210 


172.4 
174.4 
176.4 
178.5 


971.76 
970.36 
968.95 
967.54 


1144.22 
1144.83 
1145.44 
1146.05 


1916 
1844 
1775 
1708 


30.92 
29.76 
28.63 
27.57 


.03235 
.03361 
.03493 
.03628 


0.00 


14.70 


212 |180.5 


966.13 


1146.66 


1644 


26.60 


.03760 



1405 



1406 



STEAM. 





PROPERTIEi OF SATURATED 

(Compiled by W. W. Christie.) 


STEAM. 


Pounds per 
Square Inch. 


Cup 

IS 


Heat Units in one 
Pound above 32° F. 


Vol 


nme. 




6 

00 


6 


Si 
at 


S3 2,2 
3 


*5 

IIhWm 


Rela- 
tive 


Specific 






Cu. Ft. 

in 1 Cu. 

Ft. of 

Water. 


Cu. Ft, 
in one 
Lb. of 
Steam. 








1 

2 
3 
4 


102. 
126.2 
141.6 
153.0 


70.1 
94.4 
109.8 
121.4 


1042.9 
1026.0 
1015.2 
1007.2 


1113.0 
1120.4 
1125.1 
1128.6 


20623 
16730 
7325 

5588 


330.4 
171.9 
117.3 
89.51 


.0030 
.0058 
.0085 
.0112 






5 
6 

7 
8 


162.3 
170.1 
176.9 
182.9 


130.7 
138.5 
145.4 
151.4 


1000.7 
995.2 
990.4 
986.2 


1131.4 
1133.8 
1135.8 
1137.7 


4530 
3816 
3302 
2912 


72.56 
61.14 

52.89 
46.65 


.0138 
.0164 
.0189 
.0214 






9 
10 
11 
12 


188.3 
193.2 
197.7 
201.9 


156.9 
161.9 
166.5 
170.7 


982.4 
978.9 
975.7 
972.8 


1139.3 
1140.8 
1142.2 
1143.5 


2607 
2361 
2159 
1990 


41,77 
37.83 
34.59 
31.87 


,0239 
.0264 
.0289 
.0314 




.'304 
1.3 


13 
14 
15 
16 


205.8 
209.5 
213.0 
216.3 


174.7 
178.4 
181.9 
185.2 


970.0 
967.4 
964.9 
962.6 


1144.7 
1145.8 
1146.9 
1147.9 


1845 
1721 
1614 
1519 


29.56 
27.58 
25.85 
24.33 


.0338 
.0363 
.0387 
.0411 


2.3 
3.3 
4.3 
5.3 


17 
18 
19 
20 


219.4 
222.3 
225.2 
227.9 


188.4 
191.4 
194.2 
197.0 


960.4 
958.3 
956.3 
954.4 


1148.8 
1149.7 
1150.6 
1151.4 


1434 
1359 
1292 
1231 


22.98 
21.72 
20.70 
19.73 


.0435 
.0459 
.0483 
.0507 


6.3 
7.3 
8.3 
9.3 


21 
22 
23 
24 


230.5 
233.0 
235.4 
237.7 


199.6 
202.2 
204.6 
207.0 


952.5 
950.8 
949.0 
947.4 


1152.2 
1153.0 
1153.7 
1154.4 


1176 
1126 
1080 
1038 


18.84 
18.04 
17.30 
16.62 


.0531 
.0554 
.0578 
.0602 


10.3 
11.3 
12.3 
13.3 


25 
26 

27 
28 


240.0 
242.1 
244.2 
246.3 


209.3 
211.5 
213.6 
215.7 


945.8 
944.2 
942.7 
941.3 


1155.1 
1155.8 
1156.4 
1157.0 


998.4 
962.3 

928.8 
897.6 


16.00 
15.42 

14.88 
14.38 


.0625 
.0649 
.0672 
.0695 


14.3 
15.3 
16.3 
17.3 


29 
30 
31 
32 


248.3 
250.2 
252.1 
253.9 


217.7 
219.7 
221.6 
223.5 


939.9 
938.9 
937.1 
935.9 


1157.6 
1158.2 
1158.8 
1159.3 


868.5 
841.3 
815.8 
791.8 


13.91 
13.48 

13.07 
12.68 


.0719 
.0742 
.0765 

.0788 


18.3 
19.3 
20.3 
21.3 


33 
34 
35 
36 


255.7 
257.4 
259.1 
260.8 


225.3 
227.1 
228.8 
230.5 


934.6 
933.3 
932.1 
931.0 


1159.9 
1160.4 
1160.9 
1161.5 


769.2 
748.0 
727.9 
708.8 


12.32 
11.98 
11.66 
11.37 


.0812 
.0835 
.0858 
.0881 


22.3 
23 3 
24.3 
25.3 


37 
38 
39 
40 


262.4 
264.0 
265.6 
267.1 


232.1 
233.8 
235.3 
236.9 


929.8 
928.6 
927.5 
926.4 


1161.9 
1162.4 
1162.9 
1163.4 


690.8 
673.7 
657.5 
642.0 


11.07 
10.79 
10.53 
10.28 


.0904 
.0927 
.0949 
.0972 


1 
2 


6.3 
7.3 


41 

42 


268.6 
270.0 


238.4 
239.9 


925.4 
924.3 


1163.8 
1164.3 


627.3 
613.3 


10.05 
9.826 


.0995 
.1018 



PROPERTIES OF SATURATED STEAM. 



1407 



PROPERTIES OE SATURATED 


STEAM — Continued. 


Pounds per 
Square Inch. 


4a 

e3 . 

— ** 

o 3 

§£ 


Heat Units in one 
Pound above 32° F. 


Vol 


ume. 


4-1 

<Q O 


6 

CO 


6 

Is 

.a Ah 




43«S.A . 

M ""' f-> C 


MP $2 
H 


Rela- 
tive 


Specific 


° 2 


8)£ 

§Ah 

6 


Cu. Ft. 

in 1 Cu. 

Ft. of 

Water. 


Cu. Ft. 
in one 
Lb. of 
Steam. 


28.3 
29.3 
30.3 
31.3 


43 

44 

45 

. 46 


271.5 
272.9 
274.3 
275.6 


241.4 
242.8 
244.2 
245.6 


923.3 
922.3 
921.3 
920.3 


1164.7 
1165.1 
1165.6 
1166.0 


599.9 
587.0 
574.7 
563.0 


9.609 
9.403 
9.207 
9.018 


.1041 
.1063 
.1086 
.1109 


32.3 
33.3 
34.3 
35.3 


47 
58 
49 
50 


276.9 
278.2 
279.5 
280.8 


247.0 
248.3 
249.6 
250.9 


919.4 
918.4 
917.5 
916.6 


1166.4 
1166.8 
1167.2 
1167.6 


551.7 
540.9 
530.5 
520.5 


8.838 
8.665 
8.498 
8.338 


.1131 
.1154 
.1177 
.1199 


36.3 
37.3 
38.3 
39.3 


51 
52 
53 
54 


282.1 
283.3 
284.5 
285.7 


252.2 
253.5 
254.7 
255.9 


915.7 
914.8 
913.9 
913.1 


1167.9 
1168.3 
1168.7 
1169.0 


510.9 
501.7 
492.8 
484.2 


8.185 
8.037 
7.894 
7.756 


.1222 
.1244 
.1267 
.1289 


40.3 
41.3 
42.3 
43.3 


55 
56 
57 

58 


286.9 
288.0 
289.1 
290.3 


257.1 
258.3 
259.5 
260.6 


912.2 
911.4 
910.6 
909.8 


1169.4 
1169.7 
1170.1 
1170.4 


475.9 
467.9 
460.2 
452.7 


7.624 
7.496 
7.372 
7.252 


.1312 
.1334 
.1357 
.1379 


44.3 
45.3 
46.3 
47.3 


59 
60 
61 
62 


291.4 
292.5 
293.6 
294.6 


261.7 
262.9 
264.0 
265.1 


909.0 
908.2 
907.4 
906.7 


1170.8 
1171.1 
1171.4 
1171.8 


445.5 
438.5 
431.7 
425.2 


7.136 
7.024 
6.916 
6.811 


.1401 
.1424 
.1446 
.1468 


48.3 
49.3 
50.3 
51.3 


63 
64 
65 
66 


295.7 
296.7 
297.7 
298.7 


266.1 
267.2 
268.3 
269.3 


905.9 
905.2 
904.4 
903.7 


1172.1 
1172.4 
1172.7 
1173.0 


418.8 
412.6 
406.6 
400.8 


6.709 
6.610 
6.515 

6.422 


.1491 
.1513 
.1535 
.1557 


52.3 
53.3 
54.3 
55.3 


67 
68 
69 
70 


299.7 
300.7 
301.7 
302.7 


270.3 
271.3 
272.3 
273.3 


903.0 
902.3 
901.5 
900.9 


1173.3 
1173.6 
1173.9 
1174.2 


395.2 
389.8 
384.5 
379.3 


6.332 
6.244 
6.159 
6.076 


.1579 
.1602 
.1624 
.1646 


56.3 
57.3 
58.3 
59.3 


71 

72 
73 

74 


303.6 
304.6 
305.5 
306.4 


274.3 
275.3 
276.2 

277.2 


900.2 
899.5 
898.8 
898.1 


1174.5 
1174.8 
1175.1 
1175.4 


374.3 
369.4 
364.6 
360.0 


5.995 
5.917 
5.841 
5.767 


.1668 
.1690 
.1712 
.1734 


60.3 
61.3 
62.3 
63.3 


75 

76 

77 
78 


307.3 
308.2 
309.1 
310.0 


278.1 
279.0 
280.0 
280.9 


897.5 
896.8 
896.2 
895.5 


1175.6 
1175.9 
1176.2 
1176.5 


355.5 
351.1 
346.8 
342.6 


5.694 
5.624 
5.555 
5.488 


.1756 
.1778 
.1800 
.1822 


64.3 
65.3 
66.3 
67.3 


79 
80 
81 

82 


310.9 
311.8 
312.6 
313.5 


281.8 
282.7 
283.5 
284.4 


894.9 
894.3 
893.7 
893.1 


1176.7 
1177.0 
1177.3 
1177.5 


338.5 
334.5 
330.6 
326.8 


5.422 
5.358 
5.296 
5.235 


.1844 
.1866 
.1888 
.1910 


68.3 
69.3 


83 
84 


314.3 
315.1 


285.3 
286.1 


892.4 
891.8 


1177.8 
1178.0 


323.1 
319.5 


5.176 
5.118 


.1932 
.1954 



1408 



STEAM. 



PROPERTIES OF SATtRATED STE Alff — Continued. 



Pounds per 
Square Inch. 


43 

. ^ 

o g 

• OQ 

ft® 

2 Qj 

H 


Heat Units in one 
Pounds above 32° F. 


Volume. 




6 
u 

OQ 


9 

u 


Si 

5* 


+3 TO ft--. 




Rela- 
tive 


Specific 






Cu. Ft. 

in lCu. 
Ft. of 
Water. 


Cu. Ft. 
n lLb. 

of 
Steam. 




70.3 
71.3 
72.3 
73.3 


85 
86 
87 
88 


316.0 
316.8 
317.6 
318.4 


287.0 

287.8 
288.7 
289.5 


891.2 
890.6 
890.1 
889.5 


1178.3 
1178.5 
1178.8 
1179.0 


315.9 
312.5 
309.1 
305.8 


5.061 
5.006 
4.951 

4.898 


.1976 
.1998 
.2020 
.2042 


74.3 

75.3 
76.3 
77.3 


89 
90 
91 

92 


319.2 
320.0 
320.8 
321.6 


290.3 
291.1 
291.9 

292.7 


888.9 
888.3 
887.8 
887.2 


1179.3 
1179.5 
1179.8 
1180.0 


302.5 
299.4 
296.3 
293.2 


4.846 
4.796 
4.746 
4.697 


.2063 
.2085 
.2107 
.2129 


78.3 
79.3 
*0.3 
31.3 


93 
94 
95 
96 


322.3 
323.1 
323.8 
324.6 


293.5 
294.3 
295.1 
295.9 


886.6 
886.1 
885.5 
885.0 


1180.2 
1180.4 
1180.7 
1180.9 


290.2 
287.3 
284.5 
281.7 


4.650 
4.603 
4.557 
4.513 


.2151 
.2173 
.2194 
.2216 


32.3 
i*3.3 
84.3 
85.3 


97 
98 
99 
100 


325.3 
326.1 
326.8 
327.5 


296.6 

297.4 
298.1 
298.9 


884.5 
883.9 
883.4 
882.9 


1181.1 
1181.4 
1181.6 
1181.8 


279.0 
276.3 
273.7 
271.1 


4.469 
4.426 
4.384 
4.342 


.2238 
.2260 
.2281 
.2303 


U6.3 
W.3 
(58.3 

*;9.3 


101 
102 
103 
104 


328.2 
329.0 
329.7 
330.4 


299.6 
300.4 
301.1 
301.8 


882.3 
881.8 
881.3 
880.8 


1182.0 
1182.2 
1182.5 
1182.7 


268.5 
266.0 
263.6 
261.2 


4.302 
4.262 
4.223 
4.185 


.2325 
.2346 
.2368 
.2390 


£(0.3 
S'1.3 

112.3 
93.3 


105 
106 
107 
108 


331.1 

331.8 
332.4 
333.1 


302.5 
303.3 
304.0 
304.7 


880.3 
879.8 
879.3 
878.8 


1182.9 
1183.1 
1183.3 
1183.5 


258.9 
256.6 
254.3 
252.1 


4.147 
4.110 
4.074 
4.038 


.2411 
.2433 
.2455 
.2476 


34.3 
95.3 
96.3 
97.3 


109 
110 
111 
112 


333.8 
334.5 
335.1 
335.8 


305.4 
306.1 
306.8 
307.4 


878.3 
877.8 
877.3 
876.9 


1183.7 
1183.9 
1184.1 
1184.3 


249.9 
247.8 
245.7 
243.6 


4.003 
3.969 
3.935 
3.902 


.2498 
.2519 
.2541 
.2563 


S8.3 
99.3 
100.3 
in .3 


113 
114 
115 
116 


336.5 
337.1 
337.8 
338.4 


308.1 
308.8 
309.5 
310.1 


876.4 
875.9 
875.4 
875.0 


1184.5 
1184.7 
1184.9 
1185.1 


241.6 
239.6 
237.6 
235.7 


3.870 
3.838 
3.806 
3.775 


.2584 
.2606 
.2627 
.2649 


102.3 
103.3 
104.3 
105.3 


117 
118 
119 
120 


339.1 
339.7 
340.3 
340.9 


310.8 
311.4 
312.1 
312.7 


874.5 
874.0 
873.6 
873.1 


1185.3 
1185.5" 
1185.7 
1185.9 


233.8 
231.9 
230.1 
228.3 


3.745 
3.715 
3.685 
3.656 


.2670 
.2692 
.2713 
.2735 


108.3 
107.3 
103.3 
103.3 


121 
122 
123 
124 


341.6 
342.2 
342.8 
343.4 


313.4 
314.0 
314.7 
315.3 


872.7 
872.5 
871.8 
871.3 


1186.1 
1186.3 
1186.5 
1186.6 


226.5 
224.7 
223.0 
221.3 


3.628 
3.600 
3.572 
3.545 


.2757 
.2778 
.2800 
.2821 


115.3 
111.3 


125 
126 


344.0 
344.6 


315.9 
316.6 


870.9 
870.4 


1186.8 
1187.0 


219.6 
218.0 


3.518 
3.492 


.2842 
.2864 



PROPERTIES OF SATURATED STEAM. 



1409 



PROPERTIES OF SATURATED 8TE AM — Continued. 



Pounds per 
Square Inch. 


o 

o 6 


Heat Units in one 
Pound above 32° F. 


Volume. 


o © 

d*a 


6 

u 

p 


6 

4 


3 d 

U O 

H 


si 


a ° * d 

±* c3 »»;h 

h3 


a. fl • 

II °3® 

H 


Rela- 
tive 

TmTFtT. 

in 1 Cu 

Ft. of 

Water. 


Specific 


°o 

.SPdJS 
'von 




Cu. Ft. 

inlLb. 

of 

Steam . 


112.3 
113.3 
114.3 
115.3 


127 
128 
129 
130 


345.2 
345.8 
346.4 
347.0 


317.2 
317.8 
318.4 
319.0 


870.0 
869.6 
869.1 
868.7 


1187.2 
1187.4 
1187.6 
1187.8 


216.4 
214.8 
213.2 
211.6 


3.466 
3.440 
3.415 
3.390 


.2885 
.2907 
.2928 
.2950 


116.3 
117.3 
118.3 
119.3 


131 
132 
133 
134 


347.6 
348.2 
348.8 
349.3 


319.6 
320.2 
320.8 
321.4 


868.3 
867.8 
867.4 
867.0 


1187.9 
1188.1 
1188.3 
1188.5 


210.1 
208.6 
207.1 
205.7 


3.366 
3.342 
3.318 
3.295 


.2971 
.2992 
.3014 
.3035 


120.3 
121.3 
122.3 
123.3 


135 
136 
137 
138 


349.9 
350.5 
351.0 
351.7 


322.0 
322.6 
323.2 
323.8 


866.6 
866.2 
865.7 
865.3 


1188.6 
1188.8 
1189.0 
1189.1 


204.2 
202.8 
201.4 
200.0 


3.272 
3.249 
3.227 
3.204 


.3057 
.3078 
.3099 
.3121 


124.3 
125.3 
126.3 
127.3 


139 
140 
141 
142 


352.2 
352.7 
353.3 
353.8 


324.3 
324.9 
325.5 
326.1 


864.9 
864.5 
864.1 
863.7 


1189.3 
1189.5 
1189.7 
1189.8 


198.7 
197.3 
196.0 
194.7 


3.182 
3.161 
3.140 
3.119 


.3142 
.3163 
.3185 
.3206 


128.3 
129.3 
130.3 
131.3 


143 

144 
145 
146 


354.4 
354.9 
355.5 
356.0 


326.8 
327.2 
327.8 
328.3 


863.3 
862.9 
862.5 
862.1 


1190.0 
1190.2 
1190.3 
1190.4 


193.4 
192.2 
190.9 
189.7 


3.099 
3.078 
3.058 
3.038 


.3227 
.3249 
.3270 
.3291 


132.3 
133.3 
134.3 
135.3 


147 
148 
149 
150 


356.5 
357.1 
357.6 
358.1 


328.9 
329.4 
330.0 
330.5 


861.7 
861.4 
861.0 
860.6 


1190.6 
1190.8 
1191.0 
1191.1 


188.5 
187.3 
186.1 
184.9 


3.019 
3.000 
2.981 
2.962 


.3313 
.3334 
.3355 
.3376 


136.3 
137.3 
138.3 
139.3 


151 
152 
153 
154 


358.6 
359.2 
359.7 
360.2 


331.1 
331.6 
332.2 
332.7 


860.2 
859.8 
859.4 
859.1 


1191.3 
1191.4 
1191.6 
1191.8 


183.7 
182,6 
181.5 
180.4 


2.943 
2.925 
2.908 
2.890 


.3398 
.3419 
.3439 
.3460 


140.3 
141.3 
142.3 
143.3 


155 
156 
157 
158 


360.7 
361.2 
361.7 
362.2 


333.2 
333.7 
334.3 
334.8 


858.7 
858.3 
857.9 
857.6 


1191.9 
1192.1 
1192.2 
1192.4 


179.2 
178.1 
177.0 
176.0 


2.870 
2.853 
2.835 
2.819 


.3484 
.3505 
.3526 
.3547 


144.3 
145.3 
146.3 
147.3 


159 
160 
161 
162 


362.7 
363.2 
363.7 
364.2 


335.3 
335.8 
336.3 
336.9 


857.2 
856.8 
856.5 
856.1 


1192.5 
1192.7 
1192.8 
1193.0 


174.9 
173.9 
172.9 
171.9 


2.802 
2.786 
2.770 
2.754 


.3568 
.3589 
.3610 
.3631 


148.3 
149.3 
150.3 
151.3 


163 
164 

165 
166 


364.7 
365.2 
365.7 
366.2 


337.4 
337.9 
338.4 
338.9 


855.7 
855.4 
855.0 
854.7 


1193.1 
1193.3 
1193.5 
1193.6 


171.0 
170.0 
169.0 
168.1 


2.739 
2.723 
2.707 
2.693 


.3650 
.3672 
.3693 
.3714 


152.3 
153.3 


167 
168 


366.7 
367.1 


339.4 
339.9 


854.3 
853.9 


1193.7 
1193.9 


167.1 
16§.2 


2.677 
2.662 


.3735 
.3756 



1410 



STEAM. 



PROPERTIES OF SIT1H4TE1) 8TEAM- 


Continued. 


Pounds per 
Square Inch. 


o 

fl g 

is 

H 


Heat Units in One 
Pound above 32° F. 


Volume. 


© o 


6 
u 
9 

00 


.8* 


2^ 
S3 

a* 
< 


S*» o o 


>«5 

ii o «.£ 

w 


Rela- 
tive 


Specific 


° 2 

«"£ 
-£LS ci 

.SPSS ® 


|2 


Cu. Ft. 

in 1 Cu. 

Ft. of 

Water. 


Cu. Ft. 
in 1 Lb. 

of 
Steam. 


154.3 
155.3 
156.3 
157.3 


169 
170 
171 
172 


367.6 
368.1 
368.6 
369.1 


340.4 
340.9 
341.4 
341.9 


853.6 
853.2 
852.9 
852.6 


1194.0 
1194.2 
1194 3 
1194.5 


165.3 
164.3 
163.4 
162.5 


2.648 
2.631 
2.617 
2.603 


.3777 
.3799 

.3820 
.3842 


158.3 
159.3 
160.3 
161.3 


173 
174 
175 
176 


369.5 
370.0 
370.5 
370.9 


342.4 
342.8 
343.3 
343.8 


852.2 
851.9 
851.5 
851.2 


1194.6 
1194.8 
1194.9 
1195.0 


161.6 
160,7 
159.8 
158.9 


2.588 
2.574 
2.560 
2.545 


.3863 
.3885 
.3906 
.3928 


162.3 
163.3 
164.3 
165.3 


177 
178 
179 
180 


371.4 
371.9 
372.3 
372.8 


344.3 
344.8 
345.3 
345.7 


850.8 
850.5 
850.2 
849.8 


1195.2 
1195.3 
1195.5 
1195.6 


158.1 
157.2 
156.4 
155.6 


2.533 
2.518 
2.505 
2.493 


.3949 
.3970 
.3991 
.4012 


166.3 
167.3 
168.3 
169.3 


181 
182 
183 
184 


373.2 
373.7 
374.1 
374.6 


346.2 
346.7 
347.1 
347.6 


849.5 
849.2 
848.8 
848.5 


1195.7 
1195.9 
1196.0 
1196.2 


154.8 
154.0 
153.2 
152.4 


2.480 
2.467 
2.454 
2.441 


.4033 
.4054 
.4075 
.4096 


170.3 
171.3 
172.3 
173.3 


185 

186 
187 
188 


375.0 
375.5 
375.9 
376.4 


348.1 
348.6 
349.0 
349.5 


848.2 
847.8 
847.5 
847.2 


1196.3 
1196.4 
1196.6 
1196.7 


151.6 
150.8 
150.0 
149.2 


2.428 
2.416 
2.403 
2.390 


.4118 
.4140 
.4162 
.4183 


174.3 
175.3 
176.3 
177.3 


189 
190 
191 
192 


376.8 
377.2 
377.7 
378.1 


349.9 
350.4 
350.8 
351.3 


846.9 
846.5 
846.2 
845.9 


1196.8 
1197.0 
1197.1 
1197.2 


148.5 
147.8 
147.0 
146.3 


2.379 
2.367 
2.355 
2.344 


.4204 
.4225 
.4246 
.4267 


178.3 
179.3 
180.3 
181.3 


193 
194 
195 
196 


378.5 
379.0 
379.4 
379.9 


351.7 
352.2 
352.6 
353.1 


845.6 
845.3 
845.0 
844.6 


1197.4 
1197.5 
1197.6 
1197.8 


145.6 
144.9 
144.2 
143.5 


2.332 
2.321 
2.310 
2.299 


.4287 
.4308 
.4329 
.4350 


182.3 
183.3 
184.3 
185.3 


197 
198 
199 
200 


380.3 
380.7 
381.1 
381.5 


353.5 
354.0 
354.4 
354.8 


844.3 
844.0 
843.7 
843.4 


1197.9 
1198.0 
1198.1 
1198.3 


142.8 
142.1 
141.4 
140.8 


2.287 
2.276 
2.265 
2.255 


.4372 
.4393 
.4414 
.4435 


186.3 
187.3 
188.3 
189.3 


201 
202 
203 
204 


381.9 

382.4 
382.8 
383.2 


355.3 
355.7 
356.1 
356.6 


843.1 
842.8 
842.5 

842.2 


1198.4 
1198.5 
1198.7 
1198.8 


140.1 
139.5 
138.8 
138.1 


2.244 
2.235 
2.223 
2.212 


.4456 
.4477 
.4498 
.4520 


190.3 
191.3 
192.3 
193.3 


205 
206 
207 
208 


383.6 
384.0 

384.4 
384.8 


357.0 
357.4 
357.9 
358.3 


841.8 
841.5 
841.2 
841.0 


1198.9 
1199.0 
1199.2 
1199.3 


137.5 
136.9 
136.3 
135.7 


2.203 
2.193 
2.183 
2.174 


.4540 
.4560 
.4580 
.4600 


194.3 
195.3 


209 
210 


385.2 
385.6 


£58.7 
359.1 


840.7 
840.4 


1199 4 
1199.5 


135.1 
134.5 


2.164 
2.154 


.4621 
.4642 



PROPERTIES OP SATURATED STEAM. 



1411 



PROPERTIES OT SATURATED 


STEA1T — Continued. 


Founds per 
Square Inch. 


4> 


Heat Units in One 
Pound above 32° F. 


Volume. 


o 


6 

u 
3 
to 


6 

■3g 
.8* 
< 


a* 


03 © c3+j» 


lldHS 


Rela- 
tive 


Specific 




&2 


Cu. Ft. 

in 1 Cu. 

Ft. of 

Water. 


Cu. Ft. 

inl 

Lb. of 

Steam. 




196.3 
197.3 
198.3 
199.3 


211 

212 
213 
214 


386.1 
386.5 
386.9 

387.3 


359.6 
360.0 
360.4 
360.9 


840.1 
839.8 
839.5 
839.2 


1199.7 
1199.8 
1199.9 
1200.1 


133.9 
133.3 
132.8 
132.2 


2.145 
2.135 
2.126 
2.117 


.4663 
.4684 
.4705 
.4726 


200.3 
201.3 
202.3 
203.3 


215 
216 
217 
218 


387.7 
388.1 
388.5 
388.9 


361.3 
361.7 
362.1 
362.5 


838.9 

838.6 
838.3 
838.0 


1200.2 
1200.3 
1200.4 
1200.5 


131.6 
131.0 
130.4 
129.9 


2.108 
2.098 
2.089 
2.080 


.4747 
.4768 
.4789 
.4810 


204.3 
205.3 
206.3 
207.3 


219 
220 
221 
222 


389.3 
389.6 
390.1 
390.5 


362.9 
363.3 
363.7 
364.1 


837.8 
837.5 
837.3 
837.0 


1200.7 
1200.8 
1201.0 
1201.1 


129.3 
128.7 
128.1 
127.6 


2.070 
2.061 
2.052 
2.043 


.4831 
.4852 
.4873 
.4894 


208.3 
209.3 
210.3 
211.3 


223 

224 
225 
226 


390.8 
391.2 
391.6 
392.0 


364.5 
364.9 
365.3 
365.8 


836.7 
836.4 
836.1 
835.8 


1201.2 
1201.3 
1201.4 
1201.6 


127.0 
126.5 
126.0 
125.4 


2.035 
2.027 
2.018 
2.010 


.4915 
.4936 
.4956 
.4977 


212.3 
213.3 
214.3 
215.3 


227 
228 
229 
230 


392.4 
392.8 
393.2 
393.5 


366.1 
366.5 
366.9 
367.3 


835.6 
835.3 
835.0 
834.7 


1201.7 
1201.8 
1201.9 
1202.0 


124.9 
124.4 
123.9 
123.3 


2.002 
1.993 
1.984 
1.976 


.4998 
.5019 
.5040 
.5061 


216.3 
217.3 
218.3 
219.3 


231 

232 
233 
234 


393.9 
394.3 
394.7 
395.1 


367.7 
368.1 
368.5 
368.9 


834.4 
834.1 
833.9 
833.6 


1202.1 
1202.2 
1202.4 
1202.5 


122.9 
122.4 
121.9 
121.4 


1.968 
1.960 
1.952 
1.944 


.5082 
.5103 
.5124 
.5145 


220.3 
221.3 
222.3 
223.3 


235 
236 
237 
238 


395.5 
395.9 
396.3 
396.6 


369.2 
369.6 
370. 
370.4 


833.4 
833.1 
832.8 
832.5 


1202.6 
1202.7 
1202.8 
1202.9 


120.9 
120.4 
119.9 
119.4 


1.936 
1.928 
1.921 
1.913 


.5165 
.5186 
.5207 
.5228 


224.3 
225.3 
226.3 
227.3 


239 
240 
241 
242 


397.0 
397.4 
397.8 
398.1 


370.8 
371.1 
371.5 
371.9 


832.2 
832.0 
831.7 
831.4 


1203.0 
1203.1 
1203.2 
1203.3 


119.0 
118.5 
118.0 
117.5 


1.905 
1.898 
1.891 
1.884 


.5249 
.5270 
.5291 
.5312 


228.3 
229.3 
230.3 
231.3 


243 
244 
245 
246 


398.5 
398.9 
399.2 
399.6 


372.3 
372.7 
373.1 
373.4 


831.1 
830.8 
830.6 
830.4 


1203.4 
1203.5 
1203.7 
1203.8 


117.1 
116.7 
116.2 
115.7 


1.857 
1.868 
1.861 
1.853 


.5332 
.5353 
.5374 
.5395 


232.3 
233.3 
234.3 
235.3 


247 
248 
249 
250 


400.0 
400.3 
400.7 
401.1 


373.8 
374.2 
374.6 
375.0 


830.1 
829.8 
829.5 
829.2 


1203.9 
1204.0 
1204.1 
1204.2 


115.3 
114.9 
114.4 
114.0 


1.846 
1.839 
1.832 
1.825 


.5416 
.5436 
.5457 
.5478 


238.3 
241.3 


253 
256 


402.1 
403.1 


376.0 
377.0 


828.5 
827.9 


1204.5 
1204.9 


112.7 
111.4 


1.806 
1.785 


.5540 
.5603 



1412 



STEAM. 



PROPERTIES OE SATURATED STEAM — Continued. 



Pounds per 
Square Inch. 


° © 

© £ 

•*? 03 

a © 

u u 

S3 

© 


Heat Units in One 
Pound above 32° F. 


Volume. 


<M 
O 


© 

02 


© 

< 




all « 

03 © o3 -£ 


*8 

4- A • 


Rela- 
tive. 


Specific 


*H O 

*> © 9 




Cu. Ft. 

in 1 Cu. 

Ft. of 

Water. 


Cu. Ft. 
in 1 Lb. 

of 
Steam. 


-as* 


244.3 
247.3 
250.3 
253.3 


259 
262 
265 
268 


404.2 
405.2 
406.1 
407.2 


378.1 
379.2 
380.2 
381.2 


827.1 
826.3 
825.6 
824.9 


1205.2 
1205.5 
1205.8 
1206.1 


110.2 
109.2 
107.8 
106.7 


1.766 
1.746 
1.728 
1.709 


.5665 
.5727 
.5789 
.5852 


256.3 
259.3 
262.3 
265.3 


271 

274 
277 
280 


408.1 
409.1 
410.0 
411.1 


382.3 
383.3 
384.3 
385.3 


824.1 
823.4 

822.7 
822.0 


1206.4 
1206.7 
1207.0 
1207.3 


105.6 
104.5 
103.4 
102.3 


1.691 
1.673 
1.656 
1.639 


.5914 
.5976 
.6039 
.6101 


268.3 
271.3 
274.3 
277.3 


283 
286 
289 
292 


412.1 
413.0 
414.0 
415.0 


386.3 
387.3 
388.3 
389.2 


821.3 
820.6 
819.9 
819.3 


1207.6 
1207.9 
1208.2 
1208.5 


101.3 
100.3 
99.3 
98.35 


1.621 
1.606 
1.591 
1.575 


.6164 
.6226 
.6288 
.6350 


280.3 
283.3 
285.3 
290.3 


295 
298 
300 
305 


415.9 
416.9 
417.4 
418.9 


390.2 
391.1 
391.9 
394.5 


818.6 
818.0 
817.4 
815.2 


1208.8 
1209.1 
1209.3 
1209.7 


97.42 
96.47 
95.8 
94.37 


1.560 
1.545 
1.535 
1.510 


.6412 
.6474 
.6515 
.6618 


295.3 
300.3 
305.3 
310.3 


310 
315 
320 
325 


420.5 
421.9 
423.4 
424.8 


396.0 
397.6 
399.1 
400.6 


814.2 
813.0 
812.0 
810.9 


1210.2 
1210.6 
1211.1 
1211.5 


92.92 
91.52 
90.16 
88.84 


1.488 
1.465 
1.443 
1.422 


.6721 
.6824 
.6927 
.7030 


315.3 
320.3 
325.3 
330.3 


330 
335 
340 
345 


426.3 
427.7 
429.1 
430.5 


402.1 
403.6 
404.8 
406.1 


809.8 
808.8 
808.1 
807.2 


1211.9 
1212.4 
1212.9 
1213.3 


87.55 
86.31 
85.10 
83.92 


1.401 
1.382 
1.394 
1.343 


.7133 
.7236 
.7339 
.7442 


335.3 
385.3 
435.3 
485.3 


350 

400 
450 
500 


431.96 
444.9 
456.6 
467.4 


407.3 
420.8 
433.2 
444.5 


806.4 
796.9 
788.1 
780.0 


1213.7 
1217.7 
1221.3 
1224.5 


82.71 
72.8 
65.1 
58.8 


1.325 

1.167 

1.042 

.942 


.7545 
.8572 
.9595 
1.0617 


535.3 
585.3 
635.3 
685.3 


550 
600 
650 
700 


477.5 
486.9 
495.7 
504.1 


455.1 
465.2 
474.6 
483.4 


772.5 
765.3 
758.6 
752.3 


1227.6 
1230.5 
1233.2 
1235.7 


53.6 
49.3 
45.6 
42.4 


.859 
.790 
.731 
.680 


1.1638 
1.2659 
1.3679 
1.4699 


735.3 
785.3 
835.3 
885.3 


750 
800 
850 
900 


512.1 
519.6 
526.8 
533.7 


491.9 
499.9 
507.7 
515.0 


746.1 
740.4 
734.8 
729.7 


1238.0 
1240.3 
1242.5 
1244.7 


39.6 
37.1 
34.9 
33.0 


.636 
.597 
.563 
.532' 


1.5720 
1.6740 
1.7760 
1.8780 


935.3 
985.3 


950 
1000 


540.3 
546.8 


523.3 
529.3 


723.4 
719.4 


1246.7 
1248.7 


31.4 
30.0 


.505 
.480 


1.9800 
2.0820 



SUPERHEATED STEAM. 



1413 



SUPERHEATED ITEA9I. 

Dry saturated steam, after being heated to a higher temperature than that 
corresponding to its pressure, is called superheated steam. 

The behavior of superheated steam is similar to that of gases ; it is a bad 
conductor of heat, and can lose some of its heat without becoming saturated 
or wet steam. 

Superheated steam has a greater volume per unit of weight than saturated 
steam at the same pressure. 





Pressure, 


Pounds. 


70 


115 


170 


Vol< 


> at 390° F. . 




1.1 

1.33 

1.57 


1.06 
1.29 
1.52 


1.02 "Lenke" 


Vol 


at 570° F. . 




1.24 


Vol 


at 750° F. . 




1.46 











Saturated steam in engines condenses during admission to 20% to 25% of 
the quantity admitted, causing a large part of the low theoretical efficiency 
when it is used. 

Superheated steam does not condense during this period if sufficiently 
superheated. 600° to 700° F. is the temperature to which steam should be 
superheated to get its fullest benefit. Engines must be built to stand this 
high temperature, or its use should not be attempted. 

For piping to convey superheated steam, copper is not suitable, as it loses 
about 40% of its strength at the high temperature. 

Wrought iron and steel with long lengths, and few flange joints, have 
proved to be the best. 

The expansion at 100° F. is about 4£ inches in 100 ft., and must be taken 
care of in the design of steam lines. 

Superheated steam can travel at 30 to 40% higher velocity through steam 
ports than saturated steam. 

lubrication of Engines Using* Superheated Steam, 

A 120 I.H.P. Engine uses 4 lbs. of oil per 24 hours for lubrication. 
A 300 I.H.P. Corliss Comp. Engine uses 2.2 lbs. of oil per 10 hours, both 
cylinders. 

Superheaters. 

Superheating is accomplished by passing the steam, immediately before 
use, through a series of pipes placed in the path of the furnace gases, or 
placed over a furnace of their own, where the steam can be given the higher 
temperature. 

The manufacture of separate superheaters in the United States is at pres- 
ent very limited, but abroad many types are in use, and are described in 
Dawson's Pocket Book. 

Economy of Different Types of Steani Engines Using: 
Superheated Steam. 

(W. W. Christie, in Railroad Gazette, March, 1903.) 

The various results given herewith should not be compared with each other 
on the basis of water per horse-power per hour, as pressures and other con- 
ditions are different, but the economy arising from the use of superheated 
steam over the use of saturated steam in the same engine can properly be 
compared by one percentage diagram. 

The following tests (A. S. M. E., Vol. xxi, p. 788) were made by Mr. E. H. 
Foster, on a Worthington duplex direct acting triple expansion pumping 
engine, having six cylinders arranged in tandems of three on each side. The 
engine was fitted with the Schwoerer patented superheater. 

* Compared with saturated steam. 



1414 



STEAM. 



Test No 


1. 


2. 


3. 


4. 


5. 






I.H.P 


106.3 

0. 

21.8 


106.8 

0. 

21.2 


103. 
118.6 
18.9 


105. 
122.5 
18.5 


105.1 


Superheat, deg. F 

Steam per pump H.P. per hr., lbs. 


117.7 
18.0 



The average economy as shown by the above tests in using steam super- 
heated 119.6° F. is 14.1 per cent over that of saturated steam. 

Perry, in the " Steam Engine," gives the results of several tests on a Cor- 
liss compound engine with steam jacketed cylinders when developing about 
500 H.P. With saturated steam at 96 lbs. pressure the steam consumption 
was 19.8 lbs. per indicated horse-power per hour, but when the steam was 
superheated 118° F. the steam consumption dropped to 15.6 lbs., a gain of 
20.8 per cent. Other tests on a single expansion engine equipped with a 
Schmidt superheater gave, when using saturated steam, an economy of 38 
lbs. per I.H.P. per hour. When using steam with 300° superheat the steam 
consumption was 17 lbs., showing 55.3 per cent increase in favor of the lat- 
ter method. 

In a paper read before the Society of German Engineers in 1900, Oscar 
Hunger reported a test of a vertical cross compound pumping engine with 
23.6 in. and 37.4 in. x 31.5 in. cylinders and running at 40 r.p.m. At 75 lbs. 
pressure the steam consumption was 20.5 lbs. with saturated steam. With 
steam superheated 180.5° and a pressure of 150 lbs., the steam consumption 
became 12.9 lbs., or a gain of 30.7 per cent over saturated steam at the lower 
pressure. 

Again, tests of a 3,000 H.P. vertical triple expansion engine at the Berlin 
electric light works (Engineering Record, vol. xlii, p. 345) show that a gain of 
12.5, 17.9 and 18.7 per cent results from superheating the steam 181, 235 and 
264° F. respectively. 

Other tests in Bavaria, with a Sulzer compound engine (Engineering News, 
vol. xli, p. 213), give a gain of 16 per cent with steam superheated 114°, 18.5 
per cent when superheated 121°, and 25.9 per cent when superheated 173° F. 




100 150 200 250 300 

JPERHEAT IN STEAM-DEGREES FAHR. 

Fig. 12. 
Economy of Superheated Steam. 

The accompanying diagram* has been obtained from the above tests by 
plotting the degrees F. of superheat as abscissae and the per cent of economy 
as ordinates. Inspection of this diagram shows that the greatest economy 
results in the use of superheated steam in simple engine, as might be ex- 
pected. On the other hand, marked economies are shown for compound and 
triple expansion engines, but the percentage of gain decreases as the num- 
ber of expansions increases. 

* W. W. Christie. 



CONDENSATION IN STEAM-PIPES. 



1415 



COXDEyS4TIO\ I\ STEIW.PIPES. 

(W. w. c.) 

No very satisfactory figures are found for the absolute condensation 
losses in steam pipes, most of reported tests being compared with hair felt. 

0.012 lbs. per 24 hours per sq. ft. of pipe per degree Fahr., difference in 
temperature of steam and external air, which may be used in calculations, 
is based on the following : 





Sq. ft. 
Sur- 
face. 


Lbs. of Water. 


Difference 

in temperature 

Deg. F. 


u o 


Covering. 




Test by. 


in 24 


per 
sq. ft. 








hrs. 


in 24 
hrs. 








Bedle & Bauer. 


4130 


11315 


2.74 


262 


.0104 


Asbestos. 




Norris. 


3892 


9360 


2.40 


234 


.0103 


Asbestos. 




Brill. 








308 


.0105 


Magnesia sect'l. 




Norton. 








315 


.0125 


Magnesia. 





The last test by C. L. Norton (Trans. A. S.M. E., 1898) was made with the 
utmost care. Mr. Norton found that a pipe boxed in with charcoal 1 inch 
minimum thickness was 20 per cent better insulated than when magnesia 
was used, corroborating Mr. Reinhart's statements concerning his experi- 
ence using flue dust to insulate pipes. 

Aboard Ship. — The battleship "Shikishima" carries 25 Belleville 
boilers capable under full steam of developing 15,000 I.H.P. in the main 
engines besides working the auxiliaries, each boiler supplying steam for 
150 I.H.P. When at anchor, one boiler under easy steam, i.e., evaporating 
from 9 lb. to 10 lbs. of water from and at 212° F., per pound of coal — was 
just able to work one 48 K.W. steam dynamo at about half power, together 
with one feed pump, and the air and circulating pumps connected with the 
auxiliary condenser, into which the dynamo engine exhausted, besides 
working a fire and bilge pump occasionally. 

The dynamo was about 160 ft. of pipe length away from the boiler, the 
total range of steam pipe length connected being 500-600 ft. 

Performing the first-mentioned service with only one boiler under steam, 
the coal burned varied from 3£ to 5 tons per day of 18 hours, for about 65 
I.H.P., or about 7 lbs. per indicated horse-power "at the best to 10 lbs. at the 
worst, an average of 8 lbs. and over, which shows that more than half the 
fuel must have been expended in keeping the pipes warm. All pipes were 
well covered and below decks, and machinery in first-class condition. 
(London-Engr.) 

Heating* Pipes. — To determine the boiler H.P. necessary for heating, 
it maybe assumed that each sq. ft. of radiating surface will condense about 
0.3 lbs. of steam per hour as a maximum when in active service ; thus 20,000 
sq. ft. times 0.3=6000 lbs. of condensation, which divided by 30 gives 200 
boiler horse-power. 

Condensed steam in which there is no oil may be returned to the boiler 
with the feed- water to be re-evaporated. 



1416 



STEAM. 



ODTFIOW OF STEAM FROM A GIVE5T OITIAL 
PRIIKKMIE INTO YARIOll I (HI I It PRESSIRES. 

(D. K. Clark.) 



Absolute 


Outside 




Velocity of 


Actual Ve- 


Weight Dis- 


Pressure in 


Pressure 


Ratio of 


Outflow at 


locity of 


charged per Sq. 


Boiler per 


per Sq. 


Expansion. 


Constant 


Outflow 


In. of Orifice 


Sq. lnoh. 


Inch. 




Density. 


Expanded. 


per Minute. 


Lbs. 


Lbs. 


.Ratio. 


Ft. per Sec. 


Ft. per Sec. 


Lbs. 


75 


74 


1.012 


227.5 


230 


16.68 


75 


72 


1.037 


386.7 


401 


28.35 


75 


70 


1.063 


490 


521 


35.93 


75 


65 


1.136 


660 


749 


48.38 


75 


61.62 


1.198 


736 


876 


53.97 


75 


60 


1.219 


765 


933 


56.12 


75 


50 


1.434 


873 


1252 


64. 


75 


45 


1.575 


890 


1401 


65.24 


75 


43.46, 58 % 


1.624 


890.6 


1446.5 


65.3 


75 


15 


1.624 


890.6 


1446.5 


65.3 


75 





1.624 


890.6 


1446.5 


65.3 



When, however, steam of varying initial pressure is discharged into the 
atmosphere — pressures of which the atmospheric pressure is not more 
than 58 per cent — the velocity of outflow at constant density, that is, sup- 
posing the initial density to be maintained, is given by the formula — 

V— 3.5953 yh, 
where P=: the velocity of outflow in feet per minute, as for steam of the 
initial density, h = the height in feet of a column of steam of the given 
absolute initial pressure of uniform density, the weight of which is equal to 
the pressure on the unit of base. 

The following table is calculated from this formula : 

OUTFLOW OF STEAM 1 Y TO THE ATMOSPHERE. 

(D. K. Clark.) 



Absolute 




• 








Initial 


Outside 


Ratio of 


Velocity of 


Actual Ve- 


Weight Dis- 


Pressure in 


Pressure 


Expansion 


Outflow at 


locity of 
Outflow, 


charged per 


Boiler in 


in Lbs. per 


in 


Constant 


Sq. Inch of 


Lbs. per 
Sq. Inch. 


Sq. Inch. 


Nozzle. 


Density. 


Expanded. 


Orifice per Min. 


Lbs. 


Lbs. 


Ratio. 


Ft. per Sec. 


Ft. per Sec. 


Lbs. 


25.37 


14.7 


1.624 


863 


1401 


22.81 


30 


14.7 


1.624 


867 


1408 


26.84 


40 


14.7 


1.624 


874 


1419 


35.18 


45 


14.7 


1.624 


877 


1424 


39.78 


50 


14.7 


1.624 


880 


1429 


44.06 


60 


14.7 


1.624 


885 


1437 


52.59 


70 


14.7 


1.624 


889 


1444 


61.07 


75 


14.7 


1.624 


891 


1447 


65.30 


90 


14.7 


1.624 


895 


1454 


77.94 


100 


14.7 


1.624 


898 


1459 


86.34 


115 


14.7 


1.624 


902 


1466 


98.76 


135 


14.7 


1.624 


906 


1472 


115.61 


155 


14.7 


1.624 


910 


1478 


132.21 


165 


14.7 


1.624 


912 


1481 


140.46 


215 


14.7 


1.624 


919 


1493 


181.58 



STEAM PIPES. 



1417 



§TEAM PIPES. 

Rankine says the velocity of steam flow in pipes should not exceed 6000 
feet per minute (100 feet per second). As increased size of pipe means in- 
creased loss by radiation, care should be taken that in order to decrease the 
velocity of flow, the losses by radiation do not become considerable. 

The quantity discharged per minute may be approximately found by 
Rankine's formula (" Steam Engine," p. 298), W =. 60 ap -j- 70 = 6 ap -f- 7, in 
which W=: weight in pounds, a == area of orifice in square inches, and p = 
absolute pressure. The results must be multiplied by k =: 0.93 for a short 
pipe, and by k = 0.63 for their openings as in a safety valve. 

Where steam flows into a pressure greater than two-thirds the pressure in 
the boiler, W~=z 1.9 ak^(p—d) d, in which d = difference in pressure in 
pounds per square inch between the two sides, and a,p, and k as above. 
Multiply the results by 2 to reduce to h.p. To determine the necessary dif- 
ference in pressure where a given h.p. is required to flow through a given 
opening, 



2 T 4 



HP 2 

14 a*k' 



Flow of Steam Tlirougrh Pipes. 

(G. H. Babcock in " Steam.'*) 

The approximate weight of any fluid which will flow in a minute through 
any given pipe with a given head or pressure may be found by the formula 

Hp l -p 2 )d* 



ID( 



'(^) 



in which W= weight in pounds, d = diameter in inches, Z>= density or 
weight per cubic foot, p t = initial pressure, p 2 = pressure at the end of the 
pipe, and L = length in feet. 

The following table gives, approximately, the weight of steam per minute 
which will flow from various initial pressures, with one pound loss of pres- 
sure through straight smooth pipes, each having a length of 240 times its 
own diameter. For sizes below 6 inches, the flow is calculated from the 
actual areas of " standard " pipe of such nominal diameters. 

For h.p. multiply the figures in the table by two. For any other loss of 
pressure, multiply by the square root of the given loss. For any other 
length of pipe, divide 240 by the given length expressed in diameters, and 
multiply the figures in the table by the square root of this quotient, which 
will give the flow for 1 pound loss of pressure. Conversely dividing the 
given length by 240 will give the loss of pressure for the flow given in the 
table. 

Table of Flow of Steam Through Pipes. 



Initial Pres- 


Diameter of Pip 


e in Inches. Length of each == 240 Diameters. 


sure by 
Gauge. 














I 


1 


U 


2 


2£ 


3 


4 


Lbs. per Sq. 
















Inch. 
















Weight 


of Stean 


l per Mi 


a. in Lbs., with 1 I 


;b. Loss of 


Pressure. 


1 


1.16 


2.07 


5.7 


10.27 


15.45 


25.38 


46.85 


10 


1.44 


2.57 


7.1 


12.72 


19.15 


31.45 


58.05 


20 


1.70 


3.02 


8.3 


14.94 


22.49 


36.94 


68.20 


30 


1.91 


3.40 


9.4 


16.84 


25.35 


41.63 


76.84 


40 


2.10 


3.74 


10.3 


18.51 


27.87 


45.77 


84.49 


50 


2.27 


4.04 


11.2 


20.01 


30.13 


49.48 


91.34 


60 


2.43 


4.32 


11.9 


21.38 


32.19 


52.87 


97.60 


70 


2.57 


4.58 


12.6 


22.65 


34.10 


56.00 


103.37 


80 


2.71 


4.82 


13.3 


23.82 


35.87 


58.91 


108.74 


90 


2.83 


5.04 


13.9 


24.92 


37.52 


61.62 


113.74 


100 


2.95 


5.25 


14.5 


25.96 


39.07 


64.18 


118.47 


120 


3.16 


5.63 


15.5 


27.85 


41.93 


68.87 


127.12 


150 


3.45 


6.14 


17.0 


30.37 


45.72 


75.09 


138.61 



1418 



STEAM. 



Table 


of Flow of 


Steam 


Tlirou 


g"li Pipes. — Continued. 


Initial Pres- 


Diameter of Pipe in Inches. Length of Eachr= 240 Diameters. 


sure by 
Gauge. 












5 6 


8 


10 


12 


15 


18 


Lbs. per Sq. 














Inch. 














Weight of Steam per Min. in Lbs 


., with 1 Lb. Loss of Pressure. 


1 


77.3 


115.9 


211.4 


341.1 


502.4 


804 1177 


10 


95.8 


143.6 


262.0 


422.7 


622.5 


996 


1458 


20 


112.6 


168.7 


307.8 


496.5 


731.3 


1170 


1713 


30 


126.9 


190.1 


346.8 


559.5 


824.1 


1318 


1930 


40 


139.5 


209.0 


381.3 


615.3 


906.0 


1450 


2122 


50 


150.8 


226.0 


412.2 


665.0 


979.5 


1567 


2294 


60 


161.1 


241.5 


440.5 


710.6 


1046.7 


1675 


2451 


70 


170.7 


255.8 


466.5 


752.7 


1108.5 


1774 


2596 


80 


179.5 


269.0 


490.7 


791.7 


1166.1 


1866 


2731 


90 


187.8 


281.4 


513.3 


828.1 


1219.8 


1951 


2856 


100 


195.6 


293.1 


534.6 


862.6 


1270.1 


2032 


2975 


120 


209.9 


314.5 


573.7 


925.6 


1363.3 


2181 


3193 


150 


228.8 


343.0 


625.5 


1009.2 


1486.5 


2378 


3481 



The loss of head due to getting up the velocity, to the friction of the 
3team entering the pipe and passing elbows and valves, will reduce the 
flow given in the table. The resistance at the opening and that at a 
globe valve are each about the same as that for a length of pipe equal to 

114 diameters divided by a number represented by 1 + -j- • For the sizes of 

pipes given in the table these corresponding lengths are : 



1 1* 
20 25 34 



2 2i 
41 47 



3 I 4 
52 | 60 



6 


8 


10 


12 


15 


18 


71 


79 


84 


88 


92 


95 



The resistance at an elbow is equal to § that of a globe valve. These 
equivalents — for opening, for elbows, and for valves — must be added in 
each instance to the actual length of pipe. Thus a 4-inch pipe, 120 diame- 
ters (40 feet) long, with a globe valve and three elbows, would be equivalent 
to 120 -f 60 + 60 4- (3 X 40) = 360 diameters long ; and 360 -f- 240 = 1£. It 
would therefore have 1£ lbs. loss of pressure at the flow given in the table, 
or deliver (1 -f- ViJ = .gi6), 81.6 per cent of the steam with the same (1 lb.) 
loss of pressure. 

Equation of Pipes (Steam). 

It is frequently desirable to know what number of one size of pipes will 
equal in capacity another given pipe for delivery of steam or water. At 
the same velocity of flow two pipes deliver as the squares of their internal 
diimeters, but the same head will not produce the same velocity in pipes of 
diiferent sizes or lengths, the difference being usually stated to vary as the 
square root of the fifth power of the diameter. The friction of a fluid 
within itself is very slight, and therefore the main resistance to flow is the 
friction upon the sides of the conduit. This extends to a limited distance, 
and is, of course, greater in proportion to the contents of a small pipe than 
«i,- a il rg S^ }• may be approximated in a given pipe bv a constant multi- 
plied by the diameter, or the ratio of flow found by dividing some power of 
tne diameter by the diameter increased by a constant. Careful compari- 
sons ota large number of experiments, by different investigators, has de- 
T 2 *?,?• fcne following as a close approximation to the relative flow in pipes 
or dilrerent sizes under similar conditions : 

w d * 

W 00 

_ V d + 3.6 

W being the weight of fluid delivered in a given time, and d being the 

internal diameter in inches. 



STEAM PIPES. 



1419 



The diameters of " standard " steam and gas pipe, however, vary from the 
nominal diameters, and in applying this rule it is necessary to take the true 
measurements, which are given in the following table : 

Table of Standard Sizes Steam and Cfax Pipes. 



m 

o 

H 


Diameter. 




Diameter. 


(0 


Diameter. 






H 






H 


1 


<1> 


Inter- 


Exter- 


aT 


Inter- 


Exter- 




Inter- 


Exter- 


N 


nal. 


nal. 


N 


nal. 


nal. 


N 


nal. 


nal. 


w. 






m 






m 






1 


.27 


.40 


2h 


2.47 


2.87 


9 


8.94 


9.62 


1 


.36 


.54 


3 


3.07 


3.5 


10 


10.02 


10.75 


.49 


.67 


3* 


3.55 


4 


11 


11 


11.75 




.62 


.84 


4 


4.03 


4.5 


12 


12 


12.75 


1 


.82 


1.05 


4i 


4.51 


5 


13 


13.25 


14 


1 


1.05 


1.31 


5 


5.04 


5.56 


14 


14.25 


15 


\l 


1.38 


1.66 


6 


6.06 


6.62 


15 


15.43 


16 


1.61 


1.90 


7 


7.02 


7.62 


16 


16.4 


17 


2 


2.07 


2.37 


8 


7.98 


8.62 


17 


17.32 


18 



The following table gives the number of pipes of one size required to 
equal in delivery other larger pipes of the same length and under the same 
conditions. The upper portion above the diagonal line of blanks pertains to 
" standard " steam and gas pipes, while the lower portion is for pipe of the 
actual internal diameters given. The figures given in the table opposite the 
intersection of any two sizes is the number of the smaller-sized pipes 
required to equal one of the larger. 



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DIAGRAM GIVING 

DIAMETER OF STEAM AND EXHAUST PIPES 

FOR ENGINE CYLINDERS FROM 5 TO 40 INCHES CHAMETER, 
^L^lvVtOtX AT PISTON SPEEDS UP TO 1,000 

X \\\\\j\ FEET PER MINUTE 



FROM "POWER" 



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STEAM. 



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STEAM PIPES. 



1421 



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1422 STEAM. 

RELATIVE VAJLUE Of STEAM PIPE (OVEROG, 

(By H. G. Stott.) 

Before awarding a contract for covering the steam pipes in the Manhattan 
Railway Company's power-house, a careful investigation and test of different 
types and thicknesses of covering was made under the author's direction. 

The method adopted consisted in coupling up about 200 feet of 2-in. iron 
pipe. 

Sections 15 feet in length were marked off on the straight portions of the 
pipe, and so arranged as not to include any pipe couplings or bends. Two 
feet from each end of each section heavy potential wires were soldered on 
to the pipe, and at the extreme ends of the pipe, cream copper insulated 
cables were soldered on, the openings in the pipe having been previously 
closed by means of a standard coupling and plug. One of these cables ran 
direct to one terminal of a 250-kilowatt 250-volt steam-driven direct-coupled 
exciter. The cable connected to the other end of the pipe was then con- 
nected to three ammeter shunts in series, in order to enable the readings to 
be easily checked, after which it was carried through a circuit breaker and 
switch to the other exciter terminal. 

Invitations for bids were sent to all the principal pipe covering manufac- 
turers and jobbers, specifying that each one would be expected to cover one 
or more sections of the 2-inch pipe for a competitive test, and that samples 
from the successful bidders' covering would be analyzed in the company's 
chemical laboratory, and no covering accepted which departed more than 
3 per cent from this analysis. 

A special Weston Milli- Voltmeter was ordered, with which readings were 
taken from the potential wires, the latter all being brought to mercury cups 
on a testing table near which the ammeters were also located. 

Current sufficient to heat the pipe to approximately 370 degrees Fahr. 
(corresponding to a steam gauge pressure of 160 pounds) was kept on for three 
days continuously in order to dry out the various coverings, after which they 
were allowed to cool off to the air temperatures before starting the test. 

The temperature of the room was kept between 27 and 31 degrees Cent. 
(80 and 88 degrees Fahr., about) during the entire test. Each section has 
about 600 readings taken. 

The method of test was to put a current of sufficient quantity through 
the pipe to heat to, say, 220 degrees Fahr., and keep this current on for a 
sufficient time to enable all sections to maintain a constant temperature 
(this period was found to be about ten hours), when readings of the milli- 
volt-meter were taken on each section with simultaneous ammeter readings. 

A constant temperature having been obtained, it is evident that the watts 
lost in each section give an exact measure of the energy lost in maintaining 
a constant temperature, and from the watts lost the B. T. XJ. are readily 
calculated. Diagram No. 1 shows the result of the test values being re- 
duced to loss in B. T. U. per square foot of pipe surface at various temper- 
atures in the curves, and at a temperature corresponding to steam at 160 
pounds pressure in the table. 

After a series of readings had been completed, the current was raised 
sufficiently to give approximately 50 degrees Fahr. rise in the least efficient 
covering, and maintained constant for ten hours, when another series of 
readings was taken, and so on until the temperature of the pipe had reached 
a point far above anything used in practice. 



STEAM PIPE COVERINGS. 



1423 




1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.8 
HEAT LOSS:- B.T.U. PER SQ. FT. OF PIPE SURFACE PER MINUTE. 
DIAGRAM I. 

Fig. 14. 




$10000 $20000 $30000 $10000 $50000 $60000 



total expensej "cost of covering and heat loss. / 
Fig. 15. 



1424 



STEAM. 



RELATITE ECOIVOHY OF DIFFERENT TUICH- 
ItfiEfciSES OW (OVEHOG. 

85 per cent magnesia used as basis. 

The diagram shows that for two years, covering an inch thick is most eco- 
nomical. After two years the relative cost decreases quite fast with in- 
crease in thickness; and at ten years, covering three inches thick is far the 
most economical, and this without regard to pipe diameter. 



Electrical Test of Steam Pipe Covering's. 



No of 
Curve 



2 
3 
4 
5 
6 
7 
8 

9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 



Covering. 



Solid Cork, Sectional , 

85 per cent Magnesia, Sectional , 

Solid Cork, Sectional 

85 per cent Magnesia, Sectional , 

Laminated Asbesto Cork, Sectional 

85 per cent Magnesia, Sectional 

Asbestos Air Cell [Indent] Sectional 

(Imperial) 

Asbestos Sponge Felted, Sectional 

Asbestos Air Cell [Long] Sectional 

" Asbestocel " [Radial], Sectional 

Asbestos Air Cell [Long], Sectional 

" Standard " Asbestos, Sectional 

" Magnesian ", Sectional 

" Romanit " [Silk] Wrapped 

85 per cent Magnesia 2 Seetional and \" Block 

ii u i* ii ii "£" Plaster 

44 « 2-1" " , 

ii ti 2-1" '* 

44 " 2" " 

" " 2" " 

Bare Pipe [From Outside Tests] 



Aver. 
Thick- 


B.T.U. 

Loss per 
Sq. ft. at 


ness. 


lOOlb.pr. 


1.68 


1,462 


1.18 


2,008 


1.20 


2,048 


1.19 


2,130 


1.48 


2,123 


1.12 


2,190 


1.26 


2,333 


1.24 


2,552 


1.70 


2,750 


1.22 


2,801 


1.29 


2,812 


1.12 




1.28 




1.51 


1,452 


2.71 


1,381 


2.45 


1,387 


2.50 


1,412 


2.24 


1,465 


2.34 


1,555 


2.20 


1,568 




13,000 



percent 
Heat 
Saved 

Cover- 
ing. 



87.1 
84.5 
84.2 
83.6 
83.7 

83.2 
83.1 
80.3 
78.8 

78.5 
78.4 



88.8 
89.4 
88.7 
89.0 
88.7 
88.0 
87.9 



In a paper read before the A. S. M. E. in June, 1898, Prof. C. L. Norton 
of the Massachusetts Institute Technology, gave a series of tables showing 
the results of tests. For the sake of brevity the descriptions of the differ- 
ent materials are omitted. The tables follow: 



STEAM PIPE COVERINGS. 



1425 



Specimen. 



Name. 






HS.j?S 



5 •** «H " 



■»-» O O e3 






H"~ 



£0 o-* 



A 

B 

C 

D 

E 

F 

G 

H 

I 

J 

K 

L 

O 

P 



Nonpareil Cork Standard 
Nonpareil Cork Octagonal 
Manville High Pressure . 

Magnesia 

Imperial Asbestos . . . 

W. B 

Asbestos Air Cell . . . 
Manville Infusorial Earth 
Manville Low Pressure . 
Manville Magnesia Asbestos 
Magnabestos . . . 
Molded Sectional 
Asbestos Fire Board 

Calcite 

Bare Pipe .... 



2.20 
2.38 
2.38 
2.45 
2.49 
2.62 
2.77 
2.80 
2.87 
2.88 
2.91 
3.00 
3.33 
3.61 
13.84 



15.9 
17.2 
17.2 
17.7 

18.0 
18.9 
20.0 
20.2 
20.7 
20.8 
21.0 
21.7 
24.1 
26.1 
100. 



1.00 
.80 
1.25 
1.12 
1.12 
1.12 
1.12 
1.50 
1.25 
1.50 
1.12 
1.12 
1.12 
1.12 



27 
16 
54 
35 
45 
59 
35 



65 
48 
41 
35 



Specimen. 



Box A, 1 with sand .... 3.18 

2 with cork, powdered . . 1.75 

3 with cork and infusorial 1.90 

earth 

4 with sawdust 2.15 

5 with charcoal 2.00 

6 with ashes 2.46 

Brick wall 4 inches thick . . 5.18 



Miscellaneous Substances. 

B.T.U. per 

sq. ft. per 

min. 
at 200 lbs. 



Specimens. 



Pine wood 1 inch thick 
Hair felt 1 inch thick 
Cabot's seaweed quilt 
Spruce 1 inch thick . 
Spruce 2 inches thick 
Spruce 3 inches thick 
Oak 1 inch thick . . 
Hard pine 1 inch thick 



B.T.U. per 
sq. ft. per 

min. 
at 200 lbs. 
. 3.56 
. 2.51 
. 2.78 
. 3.40 
2.31 
. 2.02 
. 3.65 
. 3.72 



Prof. R. C. Carpenter says that there is great difference in the flow of heat 
through a metal plate between different media. In discussing Professor 
Norton's paper he gave the values as shown in the following table as the 
result of experiments conducted in his laboratory. 

Heat Transmitted in Thermal Units Throng-h Clean Cast- 
iron Plate T 7 g Inch Thick. (Carpenter.) 



Difference 

of 

Temperature. 


Steam to Water. 


Lard Oil to Water. 


Air to Water. 


Per Square Foot. 


Per Square Foot. 


Per Square Foot. 


Per Deg 


Total per 


Per Deg. 


Total per 


Per Deg. 


Total per 


Degrees F. 


per hour 


minute 


per hour 


minute 


per hour 


minute 


B. T. U 


B. T. U. 


B. T. U. 


B. T. IT. 


B. T. U. 


B.T.U. 


25 


21 


8.8 


6.5 


2.7 


1.2 


0.5 


50 


48 


40 


13 


10.8 


2.5 


2.7 


75 


84 


110 


19.5 


24.5 


3.7 


5.8 


100 


127 


211 


26 


43.3 


5.0 


8.3 


125 


185 


375 


31.5 


65.5 


6.2 


13 


150 


255 


637 


39 


72.5 


7.5 


18.7 


175 






45.5 


132 


8.7 


25.4 


200 






52 


173 


10 


33 


300 






78 


390 


15 


75 


400 










20 


133 


500 










25 


208 



The above investigation indicates that the substance which surrenders the 
heat is of material importance, as is also the temperature of the surrounding 
media. 

In estimating the effective steam-heating or boiler surface of tubes, the 
surface in contact with air or gases of combustion (whether internal or 
external to the tubes) is to be taken. 

For heating liquids by steam, superheating steam, or transferring heat 
from one liquid or gas to another the mean surface of the tubes is to be 
taken. 



1426 



STEAM. 



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BOILER-TUBES. 1429 

Collapsing* Pressure. 

Bessemer Steel Tubes, Lap Welded. 
A. S. M. E. Trans. 1906— R. T. Stewart. 

P= 1000 (l—^/l--1600 f. J • „ (A) 

P = 86670 l - — 1386 . (B) 

P=z collapsing pres. lbs. per sq. in. 
d z=z outs. diam. of tube — inches. 
t = thickness of wall — inches. 

Use A for values of P less than 581 lbs. 

for values of — less than 0.023. 
a 

Use B for values greater than these. 

Material tested was 56000 — 60000 lbs. tensile strength. 

Up to 8" diam. and 20 ft. long. 



Resistance of Tubes to Collapse. 

Bulletin, No. 5, Exp. Station — Univ. 111., 1906 — A. P. Carman 
Where ratio -z is greater than 0.03. 



a. For brass : 



P = 93365 4 — 2474. 
a 



b. For seamless cold drawn steel : 



c. For lap-welded steel : 



Pzr'9552o4 — 2090. 
a 



P ='83270 ~ -1025. 
a 



"Where -z is less than 0.06. 
a 

For seamless cold drawn steel : 

p= 1,000,000 ft\ 

For lap-welded steel : 

/»= 1,250,000 f^Y 



1430 



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PIPE BENDS. 



1431 



Tensile Strain of Bolts. 



Diameter 


Area at 


At 7,000 


At 10,000 


At 12,000 


At 15,000 


At 20,000 


of Bolt 


bottom of 


lbs. per sq. 


lbs. per sq. 


lbs. per sq. 


lbs. per sq. 


lbs. pel 


in inches. 


Thread. 


inch. 


inch. 


inch. 


inch. 


sq. inch.. 


| 


.125 


875 


1,250 


1,500 


1,875 


2,500 


| 


.196 


1,372 


1,960 


2,350 


2,940 


3,920 


1 


.3 


2,100 


3,000 


3,600 


4,500 


6,000 


i 


.42 


2,940 


4,200 


5,040 


6,300 


8,400 




.55 


3,850 


5,500 


6,600 


8,250 


11,000 


ii 


.69 


4,830 


6,900 


8,280 


10,350 


13,800 


i^ 


.78 


5,460 


7,800 


9,300 


11,700 


15,600 


if 


1.06 


7,420 


10,600 


12,720 


15,900 


21,200 


li • 


1.28 


8,960 


12,800 


15,360 


19,200 


25,600 


H 


1.53 


10,710 


15,300 


18,360 


22,950 


30,600 




1.76 


12,320 


17,600 


21,120 


26,400 


35,200 


i$ 


2.03 


14,210 


20,300 


24,360 


30,450 


40,600 


2 


2.3 


16,100 


23,000 


27,600 


34,500 


46,000 


h 


3.12 


21,840 


31,200 


37,440 


46,800 


62,400 


2* 


3.7 


25,900 


37,000 


44,400 


55,500 


74,000 



The breaking strength of good American bolt iron is usually taken at 
50,000 lbs. per sq. in., with an elongation of 15 per cent before breaking. It 
should not set under a strain of less than 25,000 lbs. The proof strain is 
20,000 lbs. per sq. in., and beyond this amount iron should never be strained 
in practice. 

"MM3 BE.\DS, 
Made from Wrought Iron or Steel Pipe* 

(Crane Co.) 




Fig. 17. 



The radius of any bend should not be less than 5 diameters of the pipe, and 
a larger radius is much preferable. The length X of straight pipe at each 
end of bend should be not less than as follows: 



5-inch Pipe X— 6 inches, 
6-inch Pipe X— 7 inches, 
7-inch Pipe X= 8 inches, 
8-inch Pipe Xz= 9 inches, 



10-inch Pipe X= 12 inches, 
12-inch Pipe X= 14 inches, 
14-inch Pipe X= 16 inches. 



1432 



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STEAM PIPE. 



1433 



*TAX1>AJR.D PIPE JFJLAUGKES. 

A. S. M. E. and Master Steam and Hot Water Fitters' Association stan- 
dard, adopted August, 1894. Medium pressure includes pressures ranging 
below 75 pounds. High pressure ranges up to 200 pounds per square inch. 





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Notes. — Sizes up to 24 inches are designed for 200 lbs. or less. 

Sizes from 24 to 48 inches are divided into two scales, one for 200 lbs., the 
other for less. 

The sizes of bolts given are for high pressure. For medium pressures the 
diameters are i inch less for pipes 2 to 20 inches diameter inclusive, and J 
inch less for larger sizes, except 48-inch pipe, for which the size of bolt is If 
inches. 

When two lines of figures occur under one heading, the single columns up 
to 24 inches are for both medium and high pressures. Beginning with 24 
inches, the left-hand columns are for medium and the right-hand lines are 
for high pressures. 

The sudden increase in diameters at 16 inches is due to the possible inser- 
tion of wrought-iron pipe, making with a nearly constant width of gasket a 
greater diameter desirable. 

When wrought-iron pipe is used, if thinner flanges than those given are 
sufficient, it is proposed that bosses be used to bring the bolts up to the 
standard lengths. This avoids the use of a reinforcement around the pipe. 

Figures in the third, fourth, fifth, and last columns refer only to pipe for 
200 lbs. pressure. 

In drilling valve flanges a vertical line parallel to the spindles should b© 
midway between two holes on the upper side of the flanges. 



1434 STEAM. 



ST13AM EI«OES. 

Steam engines are often classed according to the number of cylinders the 
steam passes in succession, and which are different in size, 

Simple expansion, 
Compound, 
Triple, 
Quadruple. 

Any one of the above classes, if run non-condensing, is called low-pres- 
sure, or non-condensing ; and if run with condenser is called high-pressure, 
or condensing. 

Nowadays the above classes are made in two types : high speed, including 
all engines running above, say, 150 revolutions per minute ; and low speed, 
all those running at less than 150 revolutions. 

This division is scarcely correct, as some of the long-stroke engines run- 
ning at 125 revolutions have more than 1000 feet piston speed, while few 
of the so-called high speed machines exceed 600 feet per minute piston 
speed. 

In selecting an engine for electrical work it is necessary to see that the 
machine is extra heavy in all its parts ; especially so for electric railway 
work, as the changes in load are often great and sudden, and in case of 
short circuit, engines are liable to be called on for tremendous increase in 
output, and should have no weak parts. This especially applies to fly- 
wheels, of which a large number have burst on the large, slow-running 
engines used in railway power-houses. 

Bearings should all be of extra large size, especially so on the main shaft 
journals of large direct-connected units. 

The selection of size (horse-power) depends largely upon the rating of the 
connected electrical machinery and the number of hours it runs, much being 
left to the judgment of the advising engineer. JFor direct-connected units 
it is not necessary to install an engine of greater rated capacity than the 
rated output of the generator, as the engine will easily care for overload on 
the generator if rated at \ cut-off, as is usual. 

Some builders of engines rate their sizes for connections to dynamos so as 
to supply 1£ h. p per k.w. capacity of the dynamo. 

The selection of condensing or high-pressure engines has in the past de- 
pended largely on availability of an adequate supply of water for condens- 
ing purposes ; but to-day the cooling tower with water enough to fill a 
supply-tank once, and a regular supply for boiler-feed, is a very satis- 
factory arrangement. 



STEAM ENGINES. 1435 



A DIGEST OF THE FIVAI REPORT OF COM- 

MIITEE 0\ ITAWDARDIZATIOJV OJF 

EflTOIJtfKS AM) DIAA^OS. 

(Transactions, A. S. M. E., Vol. 23, 1902.) 

1. The Committee of Standardization of Engines and Dynamos has the 
pleasure to submit its final report. 

2. The Committee's investigation has covered the standardization of the 
following points : 

<1) The standard sizes of units recommended. 

(2) The corresponding revolutions per minute for these units. 

(3) The sizes of shafts for the two classes of center-crank and side- 

crank engines. 

(4) The length along the shaft required for the generator. 

(5) The height of axis of shaft over top of sub-base. 

(6) The width of top of sub-base. 

(7) Armature fit. 

(8) Overload capacity of engines and generators. 

(9) Brush holders. 

(10) Holding-down bolts, keys, and outboard bearings. 

Size of Units. 

3. Our endeavor has been to reduce the number of standard units to the 
fewest sizes. For reasons previously stated, the largest size embraced in 
our list is 200-kilowatt capacity. 

In this connection our report covers the standardization of dibect- 
cubbent generators only. 



Revolutions. 

4. These standard speeds have been chosen after investigation of the 
practice of all the engine and generator builders in the country. It will 
be observed that we have provided for a permissible variation of speed of 
five per cent above or below the mean speed, which we recommend. 



Shaft Diameters. 

5. These are the result of analysis of the existing practice of all manu- 
facturers, and a consideration of all the conditions affecting the diameter 
of the shaft. 

In order that the reason for the diameters of shafts that we have recom- 
mended shall be thoroughly understood, we may explain that (especially in 
shafts for side-crank engines) the permissible deflection has determined the 
diameter. This, in some cases, is larger than would have been necessary 
for torsion and bending if deflection did not have to be considered. 

As cases sometimes arise where cross-compound engines or double engines 
are connected to generators coming within our recommendation, and, as 
such units require considerable larger shafts than those given in our tables, 
we deem it necessary to state, specifically, that our recommendations apply 
only to engines of usual proportions, with the generator attached at the 
Bide of, instead of between, the cranks. 



Xieng-th of Generator along* the Shaft. 

6. We found that the practice of manufacturers required provision foi 
two classes, which may be called " long " and " short " generators. 



1436 STEAM. 

We have carefully considered the fact that for these varying lengths of 
generator and shaft, the engine builder has to provide different lengths of 
sub-base, and in order to reduce the expense of patterns here to a minimum, 
our idea is that these patterns would be made so that the end away from 
the commutator can be extended the necessary amount, five or six inches, 
to take care of the increased length of bed. 

Height of Shaft. 

7. There are two classes of generators to be provided for under this head : 
Those which are split vertically, and those which are split horizontally. 
The former have a fiat base which rests directly upon the flat top of the 
sub-base, while the latter have feet which take the weight of the gene- 
rator. 

In order to arrange that the engine builders' patterns may be reduced to a 
minimum and still be stock patterns, which will fit every style of machine, 
we have chosen dimensions for height of axis of shaft above top of sub- 
base, sufficient to allow for the vertically-split machines, and also, ex- 
cept as stated later, to clear the periphery of the horizontally-split 
machines. 

As will be seen, the scheme provides for a main pattern to which patterns 
for the stools and seatings for both horizontally-and vertically-split gener- 
ators can be attached before the pattern is sent to the foundry — stools for 
the horizontally-split machines, and rectangular seatings for the vertically- 
split machines. 

In the case of the 150 and 200-kilowatt units, we have provided for a 
recess in the top of the sub-base to allow the lower part of some horizon- 
tally-split generator frames to be accommodated, and so to avoid unduly 
raising the center of the shaft. In the case of the vertically-split machines 
and those which are split horizontally and do not need this recess, the top 
of the sub-base will be flat and continuous. 



Width of Top of Sub-Base. 

8. This has been decided by examination of existing practice, and we 
believe that the figures we have recommended will cover the necessities 
for all sizes of generators. 

Armature fit. 

9. In the matter of armature fit, our recommendation is for what is known 
as a single fit. 

We have obtained the opinions of manufacturers in respect to the allow- 
ance to be made for a pressed fit, and find that allowances of T ^ inch for 
shafts 4 inches to 6 inches, inclusive, and To % inch for shafts 6£ inches to 
11 inches, inclusive, represent the best existing practice. 

The armature bore is to be the exact size given in the table, and the 
allowance is to be made by the increase of diameter of engine shaft. 

We believe, that in order to secure the best results, it will be necessary 
to work to a definite gauge ; to this end we recommend that the generator 
builder furnish a gauge the exact diameter of the bore, and the engine 
builder make the necessary allowance for the press fit, as recommended. 

Overload Capacity of Eng-ines and Generators. 

10. Generator builders are frequently called upon to provide, during 
short periods, for overloads of as much as 50 per cent, and, in occasional 
cases, of even 100 per cent. 

Bearing in mind that our recommendations are entirely for standard 
practice, we recommend that the standard overload rating of any direct- 
connected unit should not, in any case, exceed 25 per cent of the rated 
capacity. 



STEAM ENGINES. 1437 



Brash Holders, 



11. We recommend that the brush-holder rigging shall be supported upon 
the generator frame. 



Holding-down Bolts, Keys, and Outboard Bearing's. 

12. We recommend that the holding-down bolts, shaft keys for securing 
the generator hub to the shaft, and the outboard bearings, should be 
furnished by the engine builders. 

In the table will be found columns showing sizes of shaft keys which 
we recommend; also the number and size of holding-down bolts. 

It will be noticed that we do not give any lengths for keys. We believe 
it best to leave the determination of the length of key for adjustment by 
engine and generator builders in each individual case. 

Sizes of keys have been taken, so that standard rolled stock can be 
employed. 

We recommend that the keys be made straight, and be used as feathers. 
They should therefore fit accurately on the edges, and not on the top. 
proper allowance should be made in cutting the keyway in the armature 
hub, so that there will be sufficient clearance at the top of the key. 



Suggestions. 

13. In the course of our investigation our attention has been called to 
a number of points, which, from their nature, are not exactly in the same 
category as those on which we have made recommendations, but we con- 
sider them of such importance that we desire to offer them as suggestions 
for consideration by members of the Society, with a view to their adoption 
if considered sufficiently meritorious. 

A. .Pressing: Armature owi Shaft. — Usually the contract definitely 
provides by whom this is to be done, but our suggestion is that if there is 
no such provision in the contract, it should be understood that the engine 
and generator builders shall agree who is to do this work, so as to avoid 
any dispute when the separate portions of the unit are delivered on the 
premises. 

B. Floor-Iiine. — For convenience in operation, and for the informa- 
tion of engine and generator builders, we suggest that for units up to 75 
kilowatts, inclusive, the floor line should come at the bottom of the sub- 
base ; and for units 100 kilowatts to 200 kilowatts, inclusive, the floor line 
should be one inch below the rough top of the sub-base. 

C. Protecting" Commutators from Oil. — In view of the fact 
that in some cases the distance between bearing and commutator is very 
small, it is well for engine builders to bear in mind that provision should 
be made to prevent oil from the bearing getting on the commutator. 

B. Some generator builders have asked that the end of the shaft shall 
be drilled and tapped to facilitate, if necessary, the removal or placing of 
the armature on the shaft at the place of erection ; we suggest that this 
be done. 

S. In some cases, generator builders require special nuts, bolts, or fix- 
tures for attaching generators to the shaft. Under these conditions we 
suggest that the generator builders should furnish all attachments to their 
apparatus that are not already specified in our report. 



1438 



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HALF SECTION |HALF SECTION FOR SOME 160 
■ AND 200 K.W. 8ENERATQR6 
HORIZONTALLY PARTED. 



3 






9m 



STEAM ENGINES. 



1439 



Summary of Tests of Steam Engines of Various Types 

By Prof. R. C. Carpenter. 



Style of 
Engine. 




On "go 


Steam per 
I.H.P. per 
Hour. 


tual coal 
r I.H.P. 
OT Hour. 


J2 ®2 


er Cent 
bserved 
I.P. to 
apacity. 


oiler 
vap. per 
Combus. 
&A.212. 


Kind of 
Coal. 




fc 


h3 


<3 & A 


s * M 


OnO^Q 


«£5,d« 




Simple non- 


6 


200 


34.8 


4.47 


110 


55 


11.50 


Pea A. 


condensing 


1 


405 


34.5 


6.54 


257 


63.4 


9.11 


Culm 


slide valve. 


7 


1975 


35.7 


4.60 


862 


51. 


9.46 


Soft Pa. 




11 


300 


37.3 


4.49 


90 


44. 


12.20 


« a 




11 


300 


34.3 


4.72 


95 


46.7 


10.20 


" 111. 




24 


1000 


31.8 


5.38 


717 


71.7 


9.15 


" 




31 


270 


41.5 


5.50 


126 


47.5 


10.60 


Hard, Buck 




33 


270 


31.6 


4.61 


147 


54.5 


10.70 


Pea 


Average. 






35.1 


5.07 




54.2 


10.24 




Simple non- 


17 


300 


30.1 


3.09 


139 


46 


11.45 


Clearfield 


condensing 


19 


150 


26.9 


3.5 


90 


60 


9.73 


Hard, Buck 


Corliss. 


22 


350 


28. 


3.77 


153 


44.7 


8.55 


Soft, Ohio 


Average. 






28.3 


3.45 




50.3 






Compound 


2 


1000 


30.5 


4.22 


603.5 


60.3 


9.03 


1 Soft, 3 Hard 


non-con- 


4 


1250 


36.8 


4.33 


674 


53.8 


9.92 


Culm and slack 


densing. 


21 


400 


34.20 


4.17 


203 


51. 


10.23 


Soft, Pa. 




24 


1200 


30.37 


4.93 


754 


62.7 


9.01 


" 111. 


Average of. 






32.28 


4.55 










Compound 


3a 


600 


29.4 


4.43 


174 


29 


10.38 


1 Soft, 3 hard 


condensing 
high-speed 


3 


600 


23.2 


3.50 


190 


32 


9.93 


<< it 


8 


400 


20.2 


3.14 


154 


38 


8.29 


Soft, Ohio 


automatic. 


86 


400 


16.7 


2.40 


180 


45 


7.75 


it (« 




13 ' 


250 


24.6 


2.95 


86 


34.5 


10.51 


" Pa. 




16 


350 


22.7 


3.41 


164 


47 


9.50 


Hard pea 




18 


1200 


25.6 


3.61 


904 


75 


10.58 


a (i 




21 


400 


29.3 


3.81 


188 


47 


10.23 


Soft 


Average. 






23.96 


3.41 






9.64 




Compound 


10 


825 


22.7 


4.06 


482 


58.2 


8.29 


Culm & Slack 


condensing 


14 


1000 


21.9 


2.56 


277 


27.7 


10.96 


ii n 


Corliss, 


14 


1000 


20. 




314 


31.4 


10.96 


ii ti 


Greene, 


28 


350 


16.64 


2.10 


182 


52.2 


11.80 


Soft 


Mcintosh & 


27 


500 


16.90 


2.61 


290 


58. 


9.36 


" 


Seymour, 


30 


2000 


14.5 


1.80 


814 


40.7 


10.7 


it 


etc., etc. 


34 


200 


17.3 


2.91 


145 


72. 


11.14 


» 




35 


1600 


20.5 


2.18 






11.14 


(« 


Average. 






18,8 


2.60 






10.54 





14 40 STEAM. 

Hone-power of Steam Xng-ines. 
Nominal Horse-power. — Now very little used. 
D =. dia. cyl. in inches. 
A =: area of piston in sq. inches. 
L z=z length of stroke in feet. 

D 2 L 
Watt gives, nominal H.P. = ~^f 

Boulton & Watt, nominal H.P. == — • 

Kent gives as handy rule for estimating the h.p. of a single cylinder engine, 

D 2 

— . This rule is correct when the product of the m.e.p. and piston speed = 

21,000. 

The above rule also applies to compound triple and quadruple engines, and 
is referred to the diameter of the low-pressure cylinder, and the h.p. of such 
an engine then becomes 

(dia. low-pres. cyl.) 2 _ _ . . _ . 

* ^ ^- = H.P. (roughly.) 

Indicated Horse Power: I. ISC. P. — The power developed in 
the cylinder of a steam engine is correctly determined only by use of the 
indicator, and comparisons and steam consumption are always calculated 
on that basis. 
M.E.P. = mean pressure in pounds per square inch, as shown by the 
indicator card. 
i= stroke of piston in feet. 
n — number of revolutions per min. 
a = effective area of head side of piston. 
a, == effective area of crank side of piston. 
r -p. p _ [(« X m.e.p.) -f («/ X m.e.p.)] X Ln 
' 33,000 

1'or multiple cylinder engines, compute I.H.P. for each cylinder, and add 
results together for total power. 

It rake Horse-power. — The brake horse-power (B.H.P.) of an engine 
is the actual or available horse-power at the engine pulley ; at any given 
speed and given brake-load, the B.H.P is less than the corresponding I.H.P. 
by the horse-power required to drive the engine itself at the given speed, 
and .with the pressures at the bearings, guides, etc., corresponding to the 
given brake-load. 
If JF=load in lbs. on brake lever or rope, 

/= distance in feet of center of brake-wheel from line of 

action of brake-load, 
JV= revolutions per minute ; 

th*n BM.=g. 

The mechanical efficiency of any given engine is less the greater the 
expansion ratio employed, and of two engines of the same type, developing 
the same power at the same speed, that which uses the higher degree of 
expansion will have the lower mechanical efficiency. The effect of this, 
though not usually important, is to make the best ratio of expansion in any 
given case somewhat less than that which makes the steam consumption 
per I. H.P. -hour a minimum. 

The mechanical efficiencies on full load of modern engines range from 80 
to 95 per cent. Large engines have, of course, higher mechanical efficien- 
cies than small ones (a very small engine may have as low a mechanical 
efficiency as 40 to 50 per cent, but this is generally due to bad design and 
insufficient care being taken of the engine), simple than compound engines, 
and compound than triple engines — at any rate when not very large. 

Prof. Thurston estimates that the total mechanical loss in non-condensing 
engines having balanced valves may be apportioned as follows : — main 
bearings 40 to 47 per cent, pistons and rods 33 percent, crank-pins 5£ per cent 
slide-valves and rolls 2£ per cent, and eccentric straps 5 per cent. An unbal- 
anced slide-valve may absorb 26 per cent, and in a condensing engine the 
air pump 12 % of the total mechanical loss. 



STEAM ENGINES. 



1441 



Cylinder Ratios in Compound Engine*. 

The object of building multiple cylinder engines is, 

a, to use high steam pressure, 

6, to get the greatest number of expansions from the steam, 

c, to reduce the cylinder condensation. 

Prof. Thurston says : " Maximum expansion, as nearly adiabatic as prac- 
ticable*, is the secret of maximum efficiency." 

Although the theory of determining the sizes of cylinders is perfectly 
understood, yet there are so many causes for varying the results that prac- 
tically tc-day but little attention is given to calculations, the plan being to 
use dimensions such as have proved best practice in the past. 

The proportions of cylinders are supposed to be such as to equally divide 
the number of expansions and work among them, and these dimensions 
have to be varied somewhat to meet the experience of the engineer. 

Given the initial pressure (absolute) i.P. and the terminal pressure (abso- 

i.P. 
lute) t.P.y then the total number of expansions is E z^-j-~ , and the num- 
ber of expansions for each cylinder is as follows : 

For compound "^E, 

For triple expansion V E, 

For quadruple expansion V E. 

Better results are often obtained by cutting off a trifle earlier in the high- 
pressure cylinder ; and this fact, in connection with the extent of reheaters 
and receivers, changes the actual ratios from the ideal to the practical ones 
shown in the following table : 

Number of expansions for Condensing 1 [Engines. 





i.P. 

Abso- 
lute. 


Total 
Expan- 
sions. 


Expansions in Each Cylinder. 


Type. 


1st. 


2d. 


3d. 


4th. 


Single cylinder .... 

Compound 

Triple compound . . . 
Quadruple compound 


65 
145 
185 
265 


7 
22 
30 
48 


7. 
4.8 
3.2 
2.7 


4.6 
3.1 
2.65 


3.0 
2.6 


2.55 



For triple engines, Jay M. Whitham * recommends the following relative 
sizes of cylinders when the piston-speed is from 750 to 1,000 ft. per minute : 



Boiler Pressure 

(above 
Atmosphere). 


High-Pressure 
Cylinder. 


Intermediate 
Cylinder. 


Low-Press ure 
Cylinder. 


130 
140 
150 
160 


1 
1 
1 
1 


2.25 
2.40 
2.55 
2.70 


5.00 
5.85 
6.90 
7.25 



The following are the maximum, average, and minimum values of t!he 
relative cylinder volumes of triple-expansion condensing engines, working 
with boiler pressures of 150 or 160 lbs. per square inch above atmosphere, on 
board 65 boats launched within the last three or four years : — 



High-Pressure 
Cylinder. 



Maximum value 
Average " 
Minimum " 



Intermediate 
Cylinder. 



2.84 
2.58 
1.89 



Low-Pressure 
Cylinder. 



7.56 
6.71 

4.59 



* American Society of Mechanical Engineers, 1889. 



1442 



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Ratio 

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STEAM ENGINES. 1443 

Receiver Capacity. — In compound engines with cranks at right 
angles the receiver capacity should be from 1 to 1.5 times that of the 
high-pressure cylinder (Seaton), or not less than the capacity of the low- 
pressure cylinder ("Practical Engineer")- When the cranks are oppo- 
site, the receiver capacity need not exceed that of the steam passage from 
the high-pressure to the low-pressure cylinder. The general effect of large 
receiver capacity is to cause a drop between the pressure at the end of the 
high-pressure expansion stroke and the beginning of the high-pressure ex- 
haust stroke and low-pressure admission, thus increasing the power devel- 
oped in the high-pressure, and decreasing the power developed in the low- 
pressure cylinder ; this leads to a loss of power in the engine, and one 
which — at any rate in engines with cranks at right angles — is greater the 
more the receiver capacity exceeds that necessary for free passage of the 
steam. 

Steam Ports and Passages. — The areas of these should be such 
that the mean linear velocity of the steam does not exceed 5,000 to 6,000 feet 
per minute ; hence, if 

D = diameter of cylinder in inches, 
A — area of cylinder in square inches, 
a = area of port or passage in square inches, 
S = piston-speed in feet per minute ; 
__ AS _ D 2 S 
' a ~" 6,000 ~" 7,639 

for mean velocity of steam 6,000 feet per minute ; 
_ AS _ &*S 
a ~ 5,000 — 6,366 
for mean velocity of steam 5,000 feet per minute. 

The lengths of the steam passages between the cylinders and valves 
should be as small as possible, in order to minimize clearance and resist- 
ance to flow of steam. 

Condensers and Pumps. 

Condensers are principally of two types, viz., Jet Condensers, in which 
the steam and condensing water mix in a common vessel, from which both 
are pumped by the air-pump ; and Surface Condensers, in which the steam 
generally passes into a chamber containing a number of brass tubes, through 
which the condensing water is made to circulate. The latter form is usually 
adopted where water is bad, as it enables the same feed-water to be passed 
through the boiler over and over again. 

The capacity of a jet condenser should not be less than one-fourth of the 
low-pressure cylinder, but need not exceed one-half, unless the engines are 
very quick running ; one-third is a good average ratio. Large condensers 
require more time for forming the vacuum, while small condensers are 
liable to flood and overflow back to the cylinders. The amount of condens- 
ing water required per pound of steam condensed varies with the tempera- 
ture of the exhaust, of the " hot-well," and of the condensing water. (The 
44 hot-well" is the receptacle into which the air-pump delivers the water 
from the condenser.) The feed-water is obtained from the "hot-well," 
which should be maintained at 110° to 120° F. Sometimes even 130° F. can be 
obtained with care. 

The amount of cooling or tube surface depends upon the difference be- 
tween the temperature of the exhaust steam and the average temperature 
of the cooling water, and on the thermal conductivity and thickness of the 
metal tubes. For copper and brass tubes in good condition the rate of 
transmission is about 1,000 units (equivalent to about 1 lb. of steam con- 
densed) per square foot per 1° F. difference of temperature per hour. With 
the hot- well at 110° and the cooling water at 60°, the average difference is 
25°, and 25 lbs. of steam should be condensed per hour per square foot. In 
practice allowance must be made for the working conditions of the tubes, 
and half the above, i.e., £lb. of steam per 1° F. difference is nearer the usual 
allowance ; and under the above conditions about 12.5 lbs. of steam would be 
condensed per square foot per hour, which is considered very fair work. 

The tubes are generally of brass, No. 18 S.W.G. thick, and from £ to 1 in. 
diameter, according to the length of th<? tubes ; they are usually } in. in 



1444 



STEAM. 



diameter, and spaced at a pitch of 1^ in., while the tube-plates, which are 
also of brass, are 1| to 1J in. thick for | in tubes. The length of the tubes, 
when unsupported between plates, should not exceed 120 diameters. 
If H = total heat of 1 lb. of exhaust steam in B T.U., 
t = temperature F.° of hot-well, 
t x = temperature F.° of cooling water on entering, 
t 2 = temperature F.° of cooling water on leaving, 

Oj = quantity in lbs. of cooling water per lb of steam for jet condenser 
Q 2 = ditto for surface condenser : 

t=z „ , ^ - for jet condenser, 



t — H— Q 2 (t 2 — ^i), for surface condensers. 
N.B. H — t =1,050 approximately. 
Values of Q 1 and Q 2 for different temperatures of cooling water, when H- 
1150, t = 110, and t 2 = 100 in case of Q 2 : — 









Values of t x 








40 


50 


60 


70 


80 


&. . . . 


15 


17 


21 


26 


35 


Q t . . . . 


17 


21 


26 


35 


52 



Area of injection orifice should be such as to allow a velocity of flow of 
water not exceeding 1,500 feet per minute. It is better to have' a large ori- 
fice and to control the flow of water by an injection valve. 

Area of orifice in square inches. 

= lbs. water per minute -j- 650 to 750. 
= area of piston -j- 250. 

The cooling or circulating water in surface condensers should travel some 
20 ft. lineally through the tubes. In small condensers, where this is not 
convenient, and the water only circulates twice through short tubes, the 
rate of flow must be reduced. 

A replenishing cock should be fitted to allow of the passage of part of the 
circulating water into the air-pump suction to provide for water lost in 
drains, blowing off, leakage, etc. This may have one-tenth the area of the 
feed-pipe. 

A cock should be fitted close to the exhaust inlet for introducing caustic 
soda when required to dissolve grease off the tubes. 

Assume your engine to require 20 pounds of steam per horse-power per 
hour, or one-third of a pound per minute, and to exhaust at atmospheric 
pressure. One pound of steam at atmospheric pressure contains 1146.1 heat 
units above 32°. One pound of water at this temperature contains approxi- 
mately 120 — 32 = 88 heat units above 32°, so that to change a pound ol steam 
at atmospheric pressure into water at 120°, we should have to take from it 
1146.1 — 88 = 1058.1 heat units, and for one-third of a pound, 1058.1 -J- 3 = 
352.7 heat units. Suppose the injection water to be 60°. In heating to 120° 
each pound will absorb approximately 60 heat units, so that it would take 
352.7-^-60 = 5.88 pounds of injection water per minute per horse-power 
under' the assumed conditions. A higher terminal pressure, higher tem- 
perature of injection, less efficiency in the engine, or lower hot-well 
temperature, will increase this figure. 

In order to cover all conditions, makers and dealers figure that a con- 
denser should be able to supply from a gallon to a gallon and a half of in- 



CONDENSERS. 



1445 



jection water per minute for each indicated horse-power developed. The 
capacity of a single-acting vertical air-pump should be from one-tenth to 
one-twelfth that of the cylinder; of a double-acting horizontal pump, from 
one-sixteenth to one-nineteenth. 

Ejector Condensers are made on the principle of steam injectors except 
that the action is reversed, the cooling water taking the place of the steam 
in the injector, and the exhaust steam that of the feed-water. In order to 
ensure their successful working, the cooling water should be supplied at a 
head of 15 feet to 25 feet, either from a tank above or from a centrifugal or 
other pump. The amount of cooling water required is about the same as 
for jet condensing; the vacuum is from 20 in. to 25 in. 

Some builders of ejector condensers advise that the exhaust pipe from 
engine be carried up to a height of 30 feet above the level of condenser dis- 
charge, then drop straight to condenser. 

Increased momentum of the steam is very beneficial to a vacuum. 

Thirty feet provides an ample safeguard against water flooding the engine 
cylinder. 

Ejector Condenser Capacities. 



Exhaust 
Pipe 
Dia. 


Water. 


Steam 
Condensed 


Condensing 
Water req. 


Suitable 
for 




Inlet. 


Outlet. 


per Hour, 
Lbs. 


per Hour, 
Gallons. 


Engines of 


% 


1 


1 


200 


550 


5-10I.H.P. 


2 


1J 


400 


1,100 


10-20 ■ 




3 


2* 


2 


800 


2,200 


20-40 ' 




4 


3 


2* 


1,500 


4,000 


35-70 ' 




5 


3* 


3 


2,000 


5,500 


50-100 4 




6 


4 


3* 


3,000 


8,250 


75-150 ■ 




7 


5 


4 


4,000 


11,000 


100-200 4 




8 


6 


5 


6,000 


16,500 


150-300 < 




10 


7 


6 


8,000 


22,000 


200-400 ■ 




12 


8 


7 


12,000 


33,000 


300-600 < 




14 


10 


9 


20,000 


55,000 


500-1,000 « 




16 


11 


10 


28,000 


77,000 


700-1,400 « 




18 


12 


12 


36,000 


99,000 


1,000-2,000 ' 




24 




. . . 


60,000 


176,000 


2,000-4,000 ' 





This type of condenser finds favor in large electric plants which are situ- 
ated near abundant water supplies. An example of this is the Edison Station 
of the Public Service Corporation at Paterson, N.J., where they have been 
in use with great success for some years. 

Air-pumps are used to draw the condensed water from the condenser to 
the hot-well, together with the air originally contained in the water, or 
which may find its way in through glands, etc., and with jet condensers 
they also draw the cooling water. A cubic foot of ordinary water contains 
about .05 cubic foot of air at atmospheric pressure, which expands in the 
condenser to about .4 cubic foot of air ; hence the term air-pump. 

The eflftciency of a single-acting air-pump may be taken at .6 to .4, and 
generally .5, while that of the double-acting pump may be .5 to .3, say .4 on 
average. For jet condensing, the volume of the air-pump should be theo- 
retically 1.4 times the volume of condensed 4- cooling water ; for good 
working it should be from twice to thrice that required by theory. Or if 
v z=. volume of condensed water per minute in cubic feet, 
V=z volume of cooling water per minute in cubic feet, 
n — number of strokes (useful) of air-pump per minute, 
A = volume of air-pump in cubic feet ; 

v 4- V 
A = 2.8 for single-acting pumps, 

v 4- V 
= 3.5 for double-acting pumps. 

Since, for surface condensing, the air-pump does not draw the cooling 
water, and as the feed-water, being used over again, should not contain so 
much air, it would appear that the air-pump might be much smaller 
than for jet condensing. However, surface condensers are frequently 
arranged for use as jet condensers in case of mishap, and with surface con- 



1446 



STEAM. 



densing a better vacuum is expected, so that for surface condensing the air- 
pump is only Slightly less than for jet condensing. In actual practice the 
air-pump is made from one-tenth to one-twenty-ftfth the capacity of 
the low-pressure cylinder, according to the number of expansions and 
nature of condenser, while a comparison of a number of marine engines by 
different makers shows a ratio of one-sixteenth to one twenty -first. 

If expansion joints are used in the exhaust pipe, a copper bellows joint is 
better than the ordinary gland and stuffing-box type, through which air is 
apt to leak. 

Air-pump valves should have sufficient area that the full quantity of cool- 
ing and condensed water in jet condensation in passing does not exceed a 
velocity of 400 feet per minute ; in practice the area is larger than this. A 
large number of small valves is perhaps better than one or two large valves 
which are sluggish, owing to their inertia. The clearance space between 
head and foot valves should not exceed one-fifteenth the capacity of the 
pump as ordinarily constructed. 

If a — area through foot valves in square inches, 
a, == area through head valves in square inches, 
d == diameter of discharge pipe in inches, 
D = diameter of the air-pump in inches, 
S '= speed (useful) in feet per minute ; 

If there be no air vessel or receiver, d should be 10 per cent larger. 

An air-pipe should be fitted to the hot-well one-fourth the diameter of 
the discharge pipe. 

Circulating; Pumps.-The size of these depend chiefly on conditions 
mentioned for air-pumps, and they may bear a constant relation to the air- 
pump as to size, or to the L.P. cylinders. 

Air-pump. Circulating Pump. Ratio. 

Single acting Single acting .6 

Single acting Double acting .31 

Double acting Double acting .52 

or if V= volume of cooling water in cubic feet per minute, 
S= length of stroke in feet, 
n= number of strokes (useful) per minute, 
C= capacity of pump in cubic feet, 
Z>= diameter of pump in inches ; 

C=— , D= 13.55V ~S' 

n* ▼ nS 

Circulating pump valves should be of sufficient area so that the mean velo- 
city of flow does not exceed 3 or 4 feet per sec. High velocities tend to 
wear out the valves, and cause undue resistance in the pump. In the suc- 
tion and delivery pipes the velocity should not exceed 500 feet per minute, 
or for large and easy leads 600 feet per minute. Better results, however, 
will be obtained by using larger pipes, so as to reduce the velocity, espe- 
cially if the pipes are long. For single-acting pumps the suction may be 
smaller than the delivery, if the pump be below the water-level. 
If a = minimum area through valves in square inches, 
d z= minimum diameter of pipe in inches, 
A = area of pump in square inches, 
D =z diameter of pump in inches, 
S ss mean speed (useful) of pump in feet per minute ; 

AS . D^S 

a= 180' d = -K> 

where K varies from 22 for small pumps to 25 for large pumps, while for the 
suction of single-acting pumps it may be 27. 

Air chambers should always be fitted, which for single-acting pumps may 
be twice the capacity of the pump. An air-pipe should be fitted to the 



CONDENSERS. 1447 

highest points of the water passages for escape of air to enable the con- 
denser and pipes to run full. If the speed of the circulating pump cannot be 
varied independently, it is advisable to fit a water valve between the two ends 
of the pump, so that the discharge may be varied to suit the requirements. 

Strainers should be fitted to the inlet of the suction pipe; and the aggre- 
gate area of the passages should be from two to four times the area of the 
pipe, according to the velocity of flow in the pipe. Owing to difficulty 
experienced in cleaning strainers when under water, they are sometimes 
fixed in a cast-iron vessel near the suction entrances to the pump, with a 
door arranged in some convenient position for cleaning. 

Foot Valve.— When the water level is below that of the pump, a foot 
valve should be fitted just above the surface of the water. A door should 
be provided for examining the valve without disturbing the suction pipe, 
or an air ejector may be used to charge the pump. 

COOLLY^ IOWER TE*T. 

On August 2, 1898, during a run from 7 a.m. till 12 midnight, from the 
daily records, the following data is reported by Vail, A.S.M.E. Trans. Vol. 20. 

Maximum. Minimum. 

Temperature, atmosphere 103° 83° 

Temperature, condenser discharge to tower • . * . 128° 106° 

Temperature, condenser suction 98° 91° 

Degrees of heat extracted, through tower . . .32° 21° 

Speed of fans, revolutions per minute ...... 160 140 

Vacuum at condenser 26 20 

Strokes of condenser pump 50 38 

Pounds, boiler feed 121 100 

Temperature, boiler feed 212° 200° 

Engine, horse-power developed 900 H.P. 400 H J*. 

A continuous heavy load was carried during the entire 17 hours' run. 
This was not a test record, but simply daily service. 

Another day, November 5, 1898, from a 20 and 36 X 42 tandem compound 
condensing Corliss engine, the conditions were as follows : 

Engine revolutions 120 per min. 

Steam pressure 112 

Vacuum at condenser 25 

The area of the cards shows the work done in highpres* 

sure cylinder to be 311.8 H.P. 

And in low-pressure cylinder to be 331.5 H.P. 

Total 643.3 H.P. 

"Work done in low-pressure cylinder below atmospheric line 185.1 horse* 
power. Simultaneously with the engine, the pump and fan engines were 
indicated. Tower used was Barnard Type of Cooling Tower. 

The work done by the pump 13.75 H.F 

The work done by the fan engines 13.5 H.P 

Total external work 27.25 H.F, 

23.6 1.H.P. of Engine per I.H.P. of Pump and Fans. 



1448 GAS. 

GAS EtfGKOTES.* 

Nearly all commercially successful gas engines are those in which the 
cycle of operation is that proposed and patented by M. Bean de Rochas, in 
France in 1862. 

He states as necessary to economy with an explosion engine four condi- 
tions : 

1. The greatest possible cylinder volume with the least possible cooling 
surface. 

2. The greatest possible rapidity of expansion, or piston speed. 

3. The greatest possible expansion : and 

4. The greatest possible pressure at the commencement of the expansion. 
From the above Bean de Rochas reasoned these operations : 

a. Suction during an entire outstroke of the piston. 

b. Compression during the following instroke. 

c. Ignition at the dead point and expansion during the third stroke. 

d. Forcing out of the burned gases from the cylinder on the fourth 

and last return stroke. 
He proposed to accomplish ignition by increase of temperature due to 
compression. 
The otto engine uses the above cycle and flame ignition. 

Classification. 

Gas engines may be classified in accordance with the principles of the 
cycle of operations: • 

1. Explosion of gases without compression. 

2. Explosion of gases with compression. 

3. Combustion of gases with compression. 

4. Atmospheric motors. 

According to the gas used they may be classified thus : — 

A. Coal gas. 

B. Carburetted gas. 

C. Producer or Dowson gas. 

The methods of igniting the charge are 
/. Electrical arc. 
g. Flame. 
k. Incandescence. 
m. Chemical or catalytic action. 
The Otto engine is a good example of flame ignition. 

Diameter of gas main from meter to engine should be dia= .027 Brake 
H.P. + 0.79 inches. 

Atmospheric air is the working fluid of all gas engines and the fuel which 
heats it is inflammable gas. 

The air and gas are mixed thoroughly before passing into the cylinder 
itself. 

( More wasteful of fuel than four-cycle engine. Back- 
„, , . firing, or premature explosion of gas and air mix- 

i wo-cycie engine. < t ure# Used in large power units, with blast furnace 



i 



' More readily governed than two cycle. 
No pumps. 

_ i • j No inclosed crank chambers. 

if our-cycle engine. «< Must ^ e Du jit heavy in comparison with power pro- 
duced. 
v Heavy flywheels. 
There is but little difference between gas and gasoline engines, the main 
difference being a special fitting to supply the oil in the form of a vapor or 
atomized sprav. . 

Gasoline being richer than gas, by its use a much larger H.P. can be ob- 
tained from a given size of engine. 

The theoretical efficiency of a gas engine is about three times greater than 
that of a steam engine. 

Contrary to steam engine experience, when underloaded it Is a compara- 
tively efficient heat engine. 

• W. W. Christie. 



GAS ENGINES. 1449 

The highest recorded efficiency is the consumption of 8000 B.T.U.'s per 
Brake H.P., or a thermal efficiency of 31.75 per cent. Governing is not quite 
as easily accomplished under quickly varying loads, as in the steam engine, 
although late models leave little to be desired. 

In general, governing is accomplished by three methods : (1) the hit-and- 
miss, where the gas valve is closed during one or more revolutions of the 
engine; (2) by varying the mixture of air and gas in the cylinder, thereby 
producing explosions of greater or less pressure intensity ; (3) advancing or 
retarding the point of ignition. 

The average mixture is 1 part of gas to 8 to 12 parts of air in a gas engine. 

Gas engines can be run successfully and with a fair degree of economy to 
within 3 or 4 per cent of their normal rating. 

B. A. Thwaite says the " lean gases of low calorific power, such as are 
obtainable as a by-product of the manufacture of iron, are the very ones 
which enable the highest efficiency to be secured in internal-combustion 
engines." 

A gas rich in thermal units enables a larger power to be derived from a 
given engine than can be obtained by the use of a lean gas. 

Less air is required to mix with lean gas, and a higher compression is 
reached, for the mixture has a higher ignition point than rich gas mixtures. 

High compression conduces to high efficiency. 

Compression varies inversely as the calorific value of the gas, high for a 
lean gas, and vice-versa. 

For natural gas the compression displacement is made about 30 per cent 
of piston displacement. 

"Water for cylinder jacket should flow through at a rate of 4 to 5 gallons 
per H.P. per hour ; best conditions are when jacket water removes 4000 
B.T.U. per H.P. per hour. 

Best piston speed is about 600' per minute. 

Comparative Economy. 



Lbs. of Coal 
per Brake 
H.P. per 
Annum. 



Steam engine plant — simple non-condensing 
Steam engine plant — compound condensing 
Gas engine plant with producer gas . . . 



11,250 
6,400 
3,050 



Per Cent. 

Thermal efficiency simple non-condensing plant 5.5 

Thermal efficiency compound condensing plant 9.7 

Thermal efficiency gas engine plant using producer gas . . 20.3 
Thermal efficiency gas engine plant using waste blast fur- 
nace gas 23.5 

The standard gas is the natural gas of western Pennsylvania, whose calo- 
rific value is about 1000 B.T.U. 's per cubic foot. 
Ordinary illuminating gas has 750 B.T.U's. per cubic foot. 
Producer gas may be as low as 120-130 B.T.U. 's per cubic foot. 
Consumption of gas or gasoline by engines is, conservatively: 

Natural gas 10-12 cu. ft. per Br. H.P. hour. 

Illuminating gas 18-20 cu. ft. per Br. H.P. hour. 

Commercial 74° gasoline . . £-% gallon per H.P. hour. 
Gas engines operate on, say,lj lbs. of good anthracite or bituminous coal, 
approximately, in some cases as low as 1 lb. anthracite or bituminous coal. 
Gas generated from wood in Riche's retort, according to James M. N($il, 
has a calorific power of 3029 calories per cubic meter, or : 
340.8 B.T.U. per cubic foot ) . „. „ - ^ n4 . ar . „ na 
324.5 B.T.U. per cubic foot { ls ^ lven for water S as ' 
590.0 B.T.U. per cubic foot is given for coal gas. 
1 ton of wood produces 25,000 cu. ft. of gas and 400 lbs. charcoal, and colts 
14 cents per 1000 cu. ft. with wood at $3.00 a ton, neglecting in this calcu la- 
tion the charcoal. 



1450 



GAS. 



Mr. T. Fairly, Leeds, England, gives the heating power of coal gas corre- 
sponding to lighting powers as follows: no correction being made for the 
condensation of the steam produced by the combustion of hydrogen. 

Lighting power : — 

C.P. 11 12 13 14 15 16 17 18 

B.T.TT. 533 555 578 601 624 648 678 704 

Value of Coal Gas of Different Candle Powers for 
Motive Power. 

(C. Hunt.) 





Consumption 


Relative Value 


Relative Value 


Candle Power. 


Cubic Feet per 


for Motive 


for 




I.H.P. 


Power. 


Lighting. 


11.96 


30.31 


1.000 


1.000 


15.00 


24.41 


1.241 


1.254 


17.20 


22.70 


1.335 


1.438 


22.85 


17.73 


1.700 


1.910 


26.00 


16.26 


1.864 


2.173 


29.14 


15.00 


2.020 


2.436 



Gas Engine Power Plant. 

Lackawanna Steel Co., Buifalo, N.Y., uses Blast Furnace Gases. 

8-1000 H.P. Gas Engines in place, 1903. 16-2000 H.P. Gas Engines to go in 
later. 

Electric Generating plant consists of : 

5-500 K.W. 3 phase, 25 cycle, 440 volt machines. (Gen. Elec. Co.) 

4-500 K.W. 250 volt, direct current machines. (Sprague.) 

Eight of the above are direct connected to horizontal, duplex, 2 cycle, 
double-acting, Korting Gas Engines. 

One is direct connected to a 1000 H.P. Porter-Allen steam engine. 

Engines use the waste gas from the furnaces. 

By volume : CO, 24% ; C0 2 , 12% ; N, 60% ; H, 2% ; CH 4 , 2%. 
Calorific Power, 90 B.T.U.'s per cubic foot. 

The steam boilers in this plant are 250 H.P. Vertical Cahall Boilers ; 48 
have Roney Stokers, others are gas fired. 

They each have a two-part cylindrical monitor on the roof of the boiler 
house, that is easily removed, enabling rapid and easy cleaning of tubes. 
m Power," Dec, 1903. 

Gas Engine Pumping* Plant Test. 

OTidvale, W.J". Triplex pump driven by a 5 H.P. gasoline engine, 
7th trial. Discharge 153 gallons per minute. Lift, 65 ft. total. Used 5£ gal- 
lons of gasoline or 0.312 gallons per H.P. hour. 

Oreenstmrg*, Ind. Triplex pump driven by a 6 H.P. crude oil engine 
(Indianapolis, Ind., Eng. Co.), 9th trial. Discharge 184 gallons per minute, 
total lift 81.3 feet. Montpelier Crude Oil, 2 cents a gallon — 0.47 gallons per 
H.P. hour. (Eng. Rec. V. 38, 508.) 

Cost of Lifting- Water. 

With gas at 22£ cents per 1000 ft. One H.P. for 3000 hours, with a gas en- 
gine at,— 

Wilmerding, Pa $9.58 

Pitcairn, Pa 10.99 

E. Pittsburg, Pa 12.70 — J load on during test. 

(Eng. Rec. V. 38, 397.) 
The Heat Energy from burning gas is disposed of in the Otto gas 
engine as follows : 



STEAM TURBINES. 1451 



Averages of Many Teats* 

1. Actual work and friction 17 per cent. 

2. Hot expelled gases 15£ per cent. 

3. Water jacket 52 per cent. 

4. Conduction and radiation 15$ per cent. 

Gas ^Engine Pumping* Plant. 

Pittsburg Plate Glass Co., Ford City, Pa., uses natural gas of 1000 
B.T.U.'s, obtained on the premises. 
Each pumping unit of six units (5 now in — 1903) consists of : 
One 11" X 12" — 3 cyl. Westinghouse Vertical Gas Engine direct 
geared to a 16" x 15" single acting triplex pump, Stillwell-Bierce 
& Smith-Vaile Co. 
Compressed air is used to start the engines, being tanked in 3 steel 
storage tanks for this purpose. A 3 H.P. electric motor sup- 
plies this air at 180 lbs. pressure. 
Total head pumped against, 215 ft. 
Gallons per minute, 1101. 
Total cost per million gallons, $7.02. 
Steam plant doing same work cost $1,700 per month (average) for 

fuel alone. 
Gas method cost $180 per month for fuel alone. 
Full test and diagram of engine efficiency in " Power," Dec, 1903, p. 708. 



§TEAH TURBINE!.* 

Steam turbines, machines in which jets of steam striking vanes or buckets 
at a high velocity, are used as a motive power, may be classified thus : 



1. Radial flow 



Outward. 
Inward. 



2. Parallel or axial flow \ %£ s °™ 



( De Laval. 
J Parsons 
j Rateau. 
L Curtis. 



3. Mixed flow. 

If steam at a high pressure be allowed to escape through a suitably de- 
signed diverging nozzle into a lower pressure, a large proportion of its heat 
energy will be converted into kinetic energy, and the steam will expand 
adiabatically to the pressure of the medium or fluid into which it is discharged. 

There is a wide difference between steam turbines and water turbines, for 
the nozzle velocity of steam is, say, 2,000 feet per second against 96 feet for 
water. 

Then again, 1 cubic foot of water gives the same amount of kinetic energy 
as 1 cubic foot of steam at 50 lbs. pressure. 

The efficiencies of all types depend very largely upon the terminal press- 
ure at the exhaust end, and likewise on the completeness of the vacuum, 
where condensers are used ; which accords with reciprocating steam-engine 
practice. 

The absence of lubrication in the internal or steam spaces, permits the use 
of condensation and return of all water of condensation to the boilers. 

Both the above factors, as well as the use of superheated steam, assist in 
securing the high efficiencies already obtained with this motor. 

Experience shows that water carried over from the boiler does no harm in 
them. 

One point which is made in their favor, is, no boiler scale when the same 
feed water is used continuously. In that event, boilers may suffer even more 
seriously from corrosion from the water being too pure, unless raw water is 
added from time to time to neutralize the corrosive tendency. 

The steam turbine has opened up a field of usefulness all its own ; for ex- 

* W. W. Christie. 



1452 



STEAM. 



ample, the driving of centrifugal pumps, where in reciprocating engine prac- 
tice great efficiency was only obtained with low heads, turbine efficiency is 
maintained even at very great head. While used also to drive fans, prob- 
ably the greatest field ope'n to steam turbines is the driving of electric gener- 
ators, direct-connected or direct-geared. 



De Laval Steam Turbine. 

In this type the total power of the stream is devoted to the production of 
velocity in an expanding nozzle. 

The jet so produced is driven against a set of vanes on a single wheel, 
ingeniously supported and run at a very high peripheral speed, the lineal 
velocity of teeth in this type being about 100 feet per second, and gearing 
ratio 10 to 1. 

It is limited only by attending imperfections in gearing, and the type is not 
especially applicable to large sizes ; thev are not at present being built larger 
than 300 H.P. 

As now designed, there is no way to reverse this machine. 




imam 



Fig. 21. 



Tests of a De Laval Turbine by Dean and Main showed the saving by the 
use of superheated steam over that of saturated steam to be : 





Amount 
of 
Super- 
heat. 


Load 


Load 


Steam 


Dry Steam 


Saving by 


No. of 


with 


with 


used per 


used per 


use of 


Nozzles 


Super- 


Satu- 


Brake H.P. 


Brake H.P. 


Super- 


in Use. 


heated 


rated 


Avith Sup. 


with Sat. 


heated 




Steam. 


Steam. 


Steam. 


Steam. 


Steam. 




Deg. F. 


H.P. 


H.P. 


Lbs. 


Lbs. 


% 


Eight 


84 


352 


333 


13.94 


15.17 


8.8 


Seven 


64 


298 


285 


14.35 


15.56 


8.4 



Other tests by the same engineers gave with superheated steam : 



STEAM TUKBINES. 



1453 



De l^aval Turbine. 

Number of Nozzles Open, Eight (8). 
Average Reading of Barometer, 30.18 in. 
Average Temperature of Room, 83° F. 





H 

O 

w 


Steam used 

per 

Hour. (Lbs.) 


Pressure above 

Governor 
Valve. (Lbs.) 


Pressure below 

Governor 
Valve. (Lbs.) 


q 

M 

a 


O 

> 


GO'S Sh 
35 <© 


S3 

ao j-i 
. ® 


I* 

si 

o 

w 


Steam used per 
Brake Horse 

Power per 
Hour. (Lbs.) 




A.M. 


















May 22 


8-9 


4,833 


208.3 


200.6 


27.2 


81° F. 




356.6 


13.55 


(i 


9-10 


4,936 


207.5 


199.3 


27.2 


86° F. 




355.7 


13.88 


" 


10-11 


5,083 


207.7 


202.1 


27.2 


91° F. 




357.8 


14.21 


it 


11-12 


4,976 


208.3 


199.4 


27.2 


88° F. 




354.1 


14.05 


« 


M. P.M. 


















»« 


12-1 


4,841 


207.5 


194.3 


27.3 


82° F. 




343.5 


14.09 




1-2 


4,768 


206.9 


195.6 


27.2 


75° F. 




344.4 


13.84 



Governing is accomplished by regulating the steam pressure at admission 
in much the same way as in reciprocating steam engines. 



The Parsons Steam Turbine. 

In the Parsons turbine the steam, after leaving the governor valve, enters 
a steam passage and turns to the right, first passing a stationary set of blades, 
then the blades of a revolving cylinder ; this operation is repeated a number 
of times, the steam moving in an axial direction until it has reached the 



FIXED 




MOVING. 



FIXED 



f MOVING 



FIXED 



^MOVING 



Fig. 22. Vanes, Westinghouse-Parsons Turbine. 

other end of the turbine, when it is exhausted, sometimes at as low a tem- 
perature as 126° F. 

The steam velocity is not as great in this type as it is in the De Laval. 

Fig. 23 shows the relative floor space occupied by Westinghouse-Parsons* 
turbines, vertical and horizontal steam engines. 



1454 



STEAM. 









HORIZONTAL CORLISS 












■ 


' VERTICAL CORLISS 


Hi 










STEAM TURBINE 










1 


it I H 


m 


















u 



CD 




a. 


(H 


§ 


0) 


aj 


n 


QQ 


Ch 


o 


© 
E 


o 


o 


fe 


H 


+3 


i— • 





ed 


© 


a 


fr 


u 



© o 

H © 
CQ 



Fig. 23. 



1.1 

1.0 
0.9 
0.8 
0.7 
0.6 
0.5 
0.4 
0.3 
0.2 
0.1 















9 












\ 












V 


\ 










Horizonti 
CorliBB 


\ 


































V«rtioal 


\C 










CorlisB 


v^ 




G 


















Steam ( 
Turbine 

























1,000 2,000 3,000 4,000 5,000 
Electrical Horse Power 



Fig. 24. 



STEAM TURBINES. 



1455 



Type. 


Rows of 

Rotating 

Bucket 

Rings. 


Steam Velo- 
city, Feet 
per Second. 


Revolu- 
tions per 
Minute. 


Peripheral 
Speed, Feet 
per Second. 


Buckets. 


Parsons . . 
Rateau . . 
Curtis . . . 
De Laval 


35 

25 

8 

1 


400 

800 
2,000 
4,000 


3,600 

2,400 

1,800 

20,000 


200 

400 

400 

1,200 


Inserted 
Inserted 
Solid 
Inserted 



(" Dodge.") 

This type can be built so as to reverse by interchanging the steam and ex- 
haust pipe connections. The efficiency, however, is somewhat reduced re- 
versing. 

Governing is accomplished by regulating the steam at inlet as in other 
types of engines. 

A 400 K.W. Turbine gave a steam consumption of 14.47 full load to 16 lbs. 
at half rating, 19 lbs. at one-quarter rating. All per brake H.P. 

The turbine at Hartford, average load, 1800 K.W., 155 lbs. steam pressure, 
27 inch vacuum, 45° F. superheat, gave 19.1 lbs. of steam per K.W. hgur ; 
equal to about 11.46 per I. H.P. hour. 



Curtis Steam Turbine. 

In the Curtis Steam Turbine the velocity is given to the -steam in an 
expanding nozzle, designed so as to convert nearly all of the steam's 
expansive force into velocity in itself. 



STEAM Oi££T 



NOZZLE 
MOVING BLADES 
STATIONARY BLADES 
MOVING- BLADES 
STATIONARY BLA PES 
MOVING BLADES 

yZZLE DIAPHRAGM 




MOVING BLADES , 



WmEMMwlMilMM 



ccc^ccceecccccecc^ 



MOVING BLADES 



NOVING BLADES \ 






Fig. 25. 

Leaving the nozzle the steam passes successively two or more lines of 
vanes on the moving element, placed alternately, with reversed vanes, on 
the fixed element. 



1456 



STEAM. 



Governing is effected by closing or opening some of the nozzle valves, 
thus narrowing or widening the steam belt. 

Speed regulation is 2 to 4%. 

Revolutions per minute of 600 K.W. machine is 1500. 

Velocity of steam leaving the jet is 2000 ft. per second. 

Compared with large engine outfits in Manhattan Railway Company's 
New York Power Plant — the weights of Curtis is to weight of Reciprocating 
outfit as 1 is to 8. 




Fig. 26. 



The condensing type is usually designed for 150 lbs. gauge steam pressure, 
and a vacuum of 28 inches of mercury at sea level. 

Under these conditions normal overload may be 100%. 

Nozzles are different for different pressures of steam. 

This type is now being built with a condenser in its base, thereby securing 
fewer joints and connections and a better vacuum, resulting in a slight 
increase in the height of the machine. 

A vertical shaft and step bearing are typical of the Curtis turbine, 



STEAM TURBINES. 



1457 



larger sizes, and though being lubricated with oil, experiments are now 
being carried out, having in view the use of water in place of the oil as 
a floating medium, then steam packing of stem will be avoided, and no 
oil be used in condenser proper. 

This table gives some idea of the proportions of the Curtis Turbines, and 
is taken from a paper by A. H. Kruesi. 

DIRECT CURRENT. 



Num- 




Speed, 
R.P.M. 




Condensing 


Number 


Horizontal 


ber of 


K.W. 


Volts. 


or Non- 


of 


or 


Poles. 






Condensing. 


Stages. 


Vertical. 


2 


1J 


5,000 


80 


Non-Condensing 


1 


Horizontal 


2 


15 


4,000 


80 


" 


1 


" 


2 


25 


3,600 


125 


" 


1 


M 


4 


75 


2,400 


125 


(i 


2 


II 


4 


150 


2,000 


125 or 250 


'* 


2 


U 


4 


300 


1,800 


250 


(< 


4 


i< 


4 


300 


2,000 


550 


Condensing 


3 


ii 


4 


600 


1,800 


550 


" 


3 


" 


4 


500 


1,800 


550 


t< 


2 


Vertical 



ALTERNATING CURRENT. — 60 CYCLES. 



2 


100 


3,600 


2,300 


Condensing 


3 


Horizontal 


4 


500 


1,800 


2,300 


u 


2 


Vertical 


8 


1500 


900 


2,300 


(( 


2 


" 


12 


3000 


600 


2,300 


" 


4 


it 


14 


5000 


514 


2,300 


(1 


4 


it 




15000 30000 

HORSE POWER 



40000 



Fig. 27. 



Curves Showing the Relation of Foundation Material to 
Horse-Power. 



The Rateau type is somewhat similar to the De Laval, except that the 
combinations of nozzles and single wheel is repeated many times, with less 
expansion than in the older turbines. 

In making comparisons with other types of engines, it is found that for 
steam turbines, the average weight of the machine in lbs. per Brake H.P. 
is 52 lbs., against 422 for gas engines. 

About the same ratio, or 1 to 8, applies to reciprocating steam engines. 



1458 



STEAM. 



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STEAM TABLE. 1459 

A handy rule for approximately determining the outflow of the steam is 
the following : 

If the absolute steam pressure at the inlet end of the orifice is p at- 
mospheres s kg. steam will flow through each mm. 2 of the smallest section 

area of the orifice per hour. 

The above company have in many trials demonstrated this to be true 
within five per cent. 



1460 WATER-POWER. 



WATER-POWER. 

In determining the feasibility of utilizing water-power to operate electri- 
cally the industries of any particular town or city, careful consideration 
must be given to the following points, viz. : 1. The amount of water-power 
permanently available. 2. The cost of developing this power. 3. The in- 
terest on this amount. 4. The total demand for power. 5. The amounts 
and relative locations of the various kinds of power. 6. The cost of steam 
plants now in operation. 7. The interest on this amount. 8. Cost of fuel 
for plants now in operation. 9. Cost of operating present plants. Labor. 
10. Cost of maintenance of present plants. 11. The amounts and kinds of 
electric power already in operation. 12. The distance of transmission. 
13. The estimated cost of the hydraulic machinery. 14. The guaranteed 
efficiency and regulation of the hydraulic machinery. 15. Estimated cost of 
electric machinery. 16. Estimated cost of line construction. 17. Total cost 
of operating hydraulic and electric machinery. 18. Total cost of mainte- 
nance of hydraulic and electric plants. 19. The interest on the total esti- 
mated cost of proposed plant. 20. The estimated gross income. 

Charles T. Main makes the following general statements as to the value 
of a water-power : " The value of an undeveloped variable power is usually 
nothing if its variation is great, unless it is to be supplemented by a steam- 
plant. It is of value then only when the cost per horse-power for the double- 
plant is less than the cost of steam-power under the same conditions as 
mentioned for a permanent power, and its value can be represented in the 
same manner as the value of a permanent power has been represented. 

" The value of a developed power is as follows : If the power can be run 
cheaper than steam, the value is that of the power, plus the cost of plant, 
less depreciation. If it cannot be run as cheaply as steam, considering its 
cost, etc., the value of the power itself is nothing, but the value of the plant 
is such as could be paid for it new, which would bring the total cost of run- 
ning down to the cost of steam-power, less depreciation." 

Mr. Samuel Webber, Iron Age, Feb. and March, 1893, criticises the state- 
ments of Mr. Main and others who have made comparisons of costs of steam 
and of water-power unfavorable to the latter. He says : " They have based 
their calculations on the cost of steam, on large compound engines of 1000 
or more h. p. and 120 pounds pressure of steam in their boilers, and by care- 
ful 10-hour trials succeeded in figuring down steam to a cost of about $20 
per h. p., ignoring the well-known fact that its average cost in practical use, 
except near the coal mines, is from $40 to $50. In many instances dams, 
canals, and modern turbines can be all completed at a cost of $100 per h. p.; 
and the interest on that, and the cost of attendance and oil, will bring 
water-power up to but about $10 or $12 per annum ; and with a man compe- 
tent to attend the dynamo in attendance, it can probably be safely estimated 
at not over $15 per h. p. 

SYIVOPSIi OE REPORT REQUIRED OJJ 

WATER-POWER PROPERTY. 

Location. 

Geographical, etc. 
Sketch of river and its tributaries. 
Surrounding country and physical features. 
Sources ; lakes, springs, etc. 

Water's head; area drained, nature of, whether forest, swamp, snow- 
covered mountains, etc. 
Elevation of head waters and of mouth. 
Length from main source to mouth. 
Accessibility ; how and by what routes. 

Reports. 

Reports of IT. S. Coast or Geological Survey. 

Reports of Engineers U. S. Army. 

Any other reports. 

Any estimate by engineers and for what purpose. 

When it first attracted attention and for what reason. 

History. 



REPORT ON WATER-POWER PROPERTY. 1461 

Rainfall. 

Average for several years for the drainage area. Maximum, what month. 
Minimum, what month. Comparison with other similar localities. 

Volume of Water, 

Gauging of river if possible. Reports by other engineers. 
Cubic feet per second flow. 

Cubic feet per second per mile of watershed = say .2 to .3 of total rainfall 
and | available as water-power. 
Comparison with other rivers. 

Reservoirs* 

Possibility of storing water for dry time. 

Available Fall. 

Location of ; accessibility, by what routes. 

Can power be used locally, or would it be necessary to transmit it, and if 
so, where to, and distances ? Nature of country over which it would have to 
be carried. 

Volume of water in cubic feet per second. 

Horse-Power of River. 

Calculated from available fall and volume. 

Horse-power for each fall or dam. 

Location of dams, dimensions, length, and height, best method of con- 
struction, estimated cost. 

Backwater ; volume, and how far ; what interests disturbed by it ; benefits, 
if any. 

Compare power with that of similar rivers. 

Probable cost of power at dams and transmitted. 

Applications Possible. 

Near by ; at distance, stating when and for what. Note industries appli- 
cable to ; comparison with other applications. 

I¥ew Industries Suggested, 

and old industries already going to which power is applicable. 

Cost to these, and comparison with cost of other forms of power already 
in use. 

Property of the Company. 

Land, buildings, water rights, flo wage rights, franchises, lines, rights of 
way. Character of deeds. Probable value. 

Comparison with other similar properties. 

Other resources. 

liabilities. 

Stocks, bonds, floating debt, other. 

Earning* Capacity. 

Probable cost of power per h. p. at power-house. 

Probable cost of power per h. p. delivered or transmitted. 

Price for which it can be sold at power-house, and price transmitted or 
delivered. 

General Features. 

Surrounding country, its characteristics, people, cities, and towns, indus- 
tries, condition of finances. 

Facilities for transportation, water and rail. 

Nearness of sources of supplies and sales of products. 

Horse-Power of a Waterfall. 

The horse-power of a waterfall is expressed in the following formula : 
Q = quantity of water in cubic feet flowing over the fall in 1 minute. 
£T= total head in feet, i.e., the distance between the surface of the water at 
the top of the fall, and that at its foot. In a water-power the head is 
the distance between the surface of the water in the head-race, and that 
of the water in the tail-race. 



1462 WATER-POWER. 

w = weight of water per cubic foot = 62.36 lbs. at 60° F. 

O X H x w 
Gross horse-power of waterfall = Y or .00189 QH. 

Loss of head at the entrance to and exit from a water-wheel, together with 
the friction of the water passing through, reduces the power that can be 
developed to about 70 per cent of the gross power of the fall. 

Horse-Power of a Running 1 Stream. 

The power is calculated by the same formula as for a fall, but in this cae« 
H=r. theoretical head due to the velocity of the water in the stream = 

-— - where 

64.4 
v = velocity of water in feet per second. 
Q = the cubic feet of water actually impinging against the bucket per 

minute. 

Gross horse-power as .00189 QH. 

Wheels for use in the current of a stream realize only about .4 of the gross 
theoretical power. 

Current motors are often developed to operate in strong currents, such as 
that of the Niagara River opposite Buffalo, but are of little use excepting 
for small powers. Such a small fraction of the current velocity can be 
made use of that a current motor is extremely inefficient. In order to 
realize power from a current it is necessary to reduce its velocity in taking 
the power, and to get the full power would necessitate the backing up of the 
whole stream until the actual head equaled the theoretical. 

Power of Water flowing- in a Pipe* 

if due to velocity = — = — where v = velocity in feet per second. 

f 
H x due to pressure = — , where/ = pressure in lbs. per square foot. 

and w =. 62.36 lbs. =r weight 1 cubic foot of water. 
H 2 distance above datum line in feet. 

2$r ~ r w 

In hydraulic transmission the work or energy of a given quantity of water 
under pressure is the volume in cubic feet x lbs. pressure per square foot. 
Q = cubic feet per second. 
P = pressure in lbs. per square inch. 

Horse-power = ^p = -2618 PQ. 

Mill-Power. 

It has been customary in the past to lease water-power in units larger 
than the horse-power, and the term mill-power has been used to designate 
the unit. The term has no uniform value, but is different in all localities. 

Emerson gives the following values for the seven more important water- 
power. 

Holyoke, Mass. — Each mill-power at the respective falls is declared to have 
the right during 16 hours in a day to draw 38 cubic feet of water per second 
at the upper fall when the head there is 20 feet, or a quantity proportionate 
to the height at the falls. This is equal to 86.2 horse-power as a maximum. 

Lowell, Mass. — The right to draw during 15 hours in the day so much 
water as shall give a power equal to 25 cubic feet a second at the great fall, 
when the fall there is 30 feet. Equal to 85 h. p. maximum. 

Lawrence, Mass. — The right to draw during 16 hours in a day so much 
water as shall give a horse-power equal to 30 cubic feet per second when the 
head is 25 feet. Equal to 85 h. p. maximum. 

Minneapolis, Minn. — 30 cubic feet of water per second with head of 22 
feet. ' Equal to 74.8 h. p. 



MERCURY AND WATER. 



1463 



Manchester , N. H. — Divide 725 by the number of feet of fall minus 1, and 
the quotient will be the number of cubic feet per second in thai fall. For 20 
feet fall this equals 38.1 cubic feet, equal to 86.4 h. p. maximum. 

Cohoes, N.Y. — "Mill-power" equivalent to the power given by 6 cubic 
feet per second, when the fall is 20 feet. Equal to 13.6 h. p. maximum. 

Passaic, jV. J. — Mill-power : The right to draw 8£ cubic feet of water per 
second, fall of 22 feet, equal to 21.2 horse-power. Maximum rental, $700 per 
year for each mill-power = $33.00 per h. p. 

The horse-power maximum above given i6 that due theoretically to the 
weight of water and the height of the fall, assuming the water-wheel to have 
perfect efficiency. It should be multiplied by the efficiency of the wheel, 
say 75 per cent for good turbines, to obtain the h.p. delivered by the wheel. 

At Niagara power has in all cases been sold by the horse-power delivered 
to the wheels if of water, and to the building-line if electrical. 

Charges for water in Manchester, Lowell, and Lawrence, are as follows : 
Manchester, 

About $300 per year per mill-power for original purchases. 

$2 per day per mill-power for surplus. 

Lowell. 
About $300 per year per mill-power for original purchases. 
$2 per day per mill-power during " back-water." 
$4 per day per mill-power for surplus under 40 per cent. 
$10 per day per mill-power for surplus over 40 per cent and under 50 per cent. 
$20 per day per mill-power for surplus over 50 per cent. 
$75 per day per mill-power for any excess over limitation. 

Lawrence. 
About $300 per year per mill-power for original purchases. 
About <$1200 per year per mill-power for new leases at present. 
$4 per day per mill-power fur surplus up to 20 per cent. 
$8 per day per mill-power for surplus over 20 and under 50 per cent. 
$4 per day per mill-power for surplus under 50 per cent. 



COMPARISON OF (OLlM\o» OF 


WATER I]¥ 


FEET. 


IHercury in Indie*. 


and Pressure in litis., per Square Inch. 


Lbs. 


Water. | 


Merc'ry 


Water. 


Merc'ry 


Lbs. 


Merc'ry 


Water. 


Lbs. 


Press. 










Press. 






Press. 


Sq. In. 


Feet. 


Inches. 


Feet. 


Inches. 


Sq. In. 


Inches. 


Feet. 


Sq. In. 


1 


2.311 


2.046 


1 


0.8853 


0.4327 


1 


1.1295 


0.4887 


2 


4.622 


4.092 


2 


1.7706 


0.8654 


2 


2.2590 


0.9775 


3 


6.933 


6.138 


3 


2.6560 


1.2981 


3 


3.3885 


1.4662 


4 


9.244 


8.184 


4 


3.5413 


1.7308 


4 


4,5181 


1.9550 


5 


11.555 


10.230 


5 


4.4266 


2.1635 


5 


5.6476 


2.4437 


6 


13.866 


12.2276 


6 


5.3120 


2.5962 


6 


6.7771 


2.9325 


7 


16.177 


14.322 


7 


6.1973 


3.0289 


7 


7.9066 


3.4212 


8 


18.488 


16.368 


8 


7.0826 


3.4616 


8 


9.0361 


3.9100 


9 


20.800 


18.414 


9 


7.9680 


3.8942 


9 


10.165 


4.3987 


10 


23.111 


20.462 


10 


8.8533 


4.3273 


10 


11.295 


4.8875 


11 


25.422 


22.508 


11 


9.7386 


4.7600 


11 


12.424 


5.3762 


12 


27.733 


24.554 


12 


10.624 


5.1927 


12 


13.554 


5.8650 


13 


30.044 


26.600 


13 


11.509 


5.6255 


13 


14.683 


6.3537 


14 


32.355 


28.646 


14 


12.394 


6.0582 


14 


15.813 


6.8425 


15 


34.666 


30.692 


15 


13.280 


6.4909 


15 


16.942 


7.3312 


16 


36.977 


32.738 


16 


14.165 


6.9236 


16 


18.072 


7.8200 


17 


39.288 


34.784 


17 


15.050 


7.3563 


17 


19.201 


8.3087 


18 


41.599 


36.830 


18 


15.936 


7.7890 


18 


20.331 


8.7975 


19 


43,910 


38.876 


19 


16.821 


8.2217 


19 


21.460 


9.2862 


20 


46.221 


40.922 


20 


17.706 


8.6544 


20 


22.590 


9.7750 


21 


48.532 


42.968 


21 


18.591 


9.0871 


21 


23.719 


10.264 


22 


50.843 


45.014 


22 


19.477 


9.5198 


22 


24,849 


10.752 


23 


53.154 


47.060 


23 


20.362 


9.9525 


23 


25.978 


11.241 


24 


55.465 


49.106 


24 


21.247 


10.385 


24 


27.108 


11.7300 


25 


57.776 


51.152 


25 


22.133 


10.818 


25 


28.237 


12.219 


26 


60.087 


53.198 


26 


23.018 


11.251 


26 


29.367 


12.707 


27 


62.398 


55.244 


27 


23.903 


11.683 


27 


30.496 


13.196 


28 


64.709 


57.290 


28 


24.789 


12 116 


28 


31.626 


13.685 


39 


67.020 


59.336 


29 


25.674 


12.549 


29 


32.755 


14.174 


30 


69.331 


61.386 


30 


26.560 


12.981 


30 


33.885 


14.662 



1464 



WATER-POWER. 







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PRESSURE OF WATER. 



1465 



PRESSURE OF WATER. 

The pressure of water in pounds per square inch for every foot in height 
to 300 feet ; and then by intervals to 1000 feet head. 



Feet 


Press., 


Feet 


Press., 


Feet 


Press., 


Feet 


Press., 


Feet 


Press., 


He'd. 


Sq. In. 


He'd. 


Sq. In. 


He'd. 


Sq. In. 


Head. 


Sq. In. 


Head. 


Sq. In. 


1 


0.43 


65 


28.15 


129 


55.88 


193 


83.60 


257 


111.32 


2 


0.86 


66 


28.58 


130 


56.31 


194 


84.03 


258 


111.76 


3 


1.30 


67 


29.02 


131 


56.74 


195 


84.47 


259 


112.19 


4 


1.73 


68 


29.45 


132 


57.18 


196 


84.90 


260 


112.62 


5 


2.16 


69 


29.88 


133 


57.61 


197 


85.33 


261 


113.06 


6 


2.59 


70 


30.32 


134 


58.04 


198 


85.76 


262 


113.49 


7 


3.03 


71 


30.75 


135 


58.48 


199 


86.20 


263 


113.92 


8 


3.46 


72 


31.18 


136 


58.91 


200 


86.63 


264 


114.36 


9 


3.89 


73 


31.62 


137 


59.34 


201 


87.07 


265 


114.79 


10 


4.33 


74 


32.05 


138 


59.77 


202 


87.50 


266 


115.22 


11 


4.76 


75 


32.48 


139 


60.21 


203 


87.93 


267 


115.66 


12 


5.20 


76 


32.92 


140 


60.64 


204 


88.36 


268 


116.09 


13 


5.63 


77 


33.35 


141 


61.07 


205 


88.80 


269 


116.52 


14 


6.06 


78 


33.78 


142 


61.51 


206 


89.23 


270 


116.96 


15 


6.49 


79 


34.21 


143 


61.94 


207 


89.66 


271 


117.39 


16 


6.93 


80 


34.65 


144 


62.37 


208 


90.10 


272 


117.82 


17 


7.36 


81 


35.08 


145 


62.81 


209 


90.53 


273 


118.26 


18 


7.79 


82 


35.52 


146 


63.24 


210 


90.96 


274 


118.69 


19 


8.22 


83 


35.95 


147 


63.67 


211 


91.39 


275 


119.12 


20 


8.66 


84 


36.39 


148 


64.10 


212 


91.83 


276 


119.56 


21 


9.09 


85 


36.82 


149 


64.54 


213 


92.26 


277 


119.99 


22 


9.53 


86 


37.25 


150 


64.97 


214 


92.69 


278 


120.42 


23 


9.96 


87 


37.68 


151 


65.40 


215 


93.13 


279 


120.85 


24 


10.39 


88 


38.12 


152 


65.84 


216 


93.56 


280 


121.29 


25 


10.82 


89 


38.55 


153 


66.27 


217 


93.99 


281 


121.72 


26 


11.26 


90 


38.98 


154 


66.70 


218 


94.43 


282 


122.15 


27 


11.69 


91 


39.42 


155 


67.14 


219 


94.86 


283 


122.59 


28 


12.12 


92 


39.85 


156 


67.57 


220 


95.30 


284 


123.02 


29 


12.55 


93 


40.28 


157 


68.00 


221 


95.73 


285 


123.45 


30 


12.99 


94 


40.72 


158 


68.43 


222 


96.16 


286 


123.89 


31 


13.42 


95 


41.15 


159 


68.87 


223 


96.60 


287 


124.32 


32 


13.86 


96 


41.58 


160 


69.31 


224 


97.03 


288 


124.75 


33 


14.29 


97 


42.01 


161 


69.74 


225 


97.46 


289 


125.18 


34 


14.72 


98 


42.45 


162 


70.17 


226 


97.90 


290 


125.62 


35 


15.16 


99 


42.88 


163 


70.61 


227 


98.33 


291 


126.05 


36 


15.59 


100 


43.31 


164 


71.04 


228 


98.76 


292 


126.48 


37 


16.02 


101 


43.75 


165 


71.47 


229 


99.20 


293 


126.92 


38 


16.45 


102 


44.18 


166 


71.91 


230 


99.63 


294 


127.35 


39 


16.89 


103 


44.61 


167 


72.34 


231 


100.06 


295 


127.78 


40 


17.32 


104 


45.05 


168 


72.77 


232 


100,49 


296 


128.22 


41 


17.75 


105 


45.48 


169 


73.20 


233 


100.93 


297 


128.65 


42 


18.19 


106 


45.91 


170 


73.64 


234 


101.36 


298 


129.08 


43 


18.62 


107 


46.34 


171 


74.07 


235 


101.79 


299 


129.51 


44 


19.05 


108 


46.78 


172 


74.50 


236 


102.23 


300 


129.95 


45 


19.49 


109 


47.21 


173 


74.94 


237 


102.66 


310 


134.28 


46 


19.92 


110 


47.64 


174 


75.37 


238 


103.09 


320 


138.62 


47 


20.35 


111 


48.98 


175 


75.80 


239 


103.53 


330 


142.95 


48 


20.79 


112 


48.51 


176 


76.23 


240 


103.90 


340 


147.28 


49 


21.22 


113 


48.94 


177 


76.67 


241 


104.39 


350 


151.61 


50 


21.65 


114 


49.38 


178 


77.10 


242 


104.83 


360 


155.94 


51 


22.09 


115 


49.81 


179 


77.53 


243 


105.26 


370 


160.27 


52 


22.52 


116 


50.24 


180 


77.97 


244 


105.69 


380 


164.61 


53 


22.95 


117 


50.68 


181 


78.40 


245 


106.13 


390 


168.94 


54 


23.39 


118 


51.11 


182 


78.84 


246 


106.56 


400 


173.27 


55 


23.82 


119 


51.54 


183 


79.27 


247 


106.99 


500 


216.58 


56 


24.26 


120 


51.98 


184 


79.70 


248 


107.43 


600 


259.90 


57 


24.69 


121 


52.41 


185 


80.14 


249 


107.86 


700 


303.22 


58 


25.12 


122 


52.84 


186 


80.57 


250 


108.29 


800 


346.54 


59 


25.55 


123 


53.28 


187 


81.00 


251 


108.73 


900 


389.86 


60 


25.99 


124 


53.71 


188 


81.43 


252 


109.16 


1000 


433.18 


61 


26.42 


125 


54.15 


189 


81.87 


253 


109.59 






62 


26.85 


126 


54.58 


190 


82.30 


254 


110.03 






63 


27.29 


127 


55.01 


191 


82.73 


255 


110.46 






64 


2'/ .72 


128 


55.44 


192 


83.17 


256 


110.89 







14:66 WATER-POWER. 



RIVETED ITEEL PIPES, 

Riveted sheet steel pipe is much used on the Pacific Coast for conveying 
water for considerable distances under high heads, say as much as 1700 feet. 
Corrosion of iron and steel pipe has always been an argument against its 
use, but for about thirty years such pipe has been in use in California; and 
a life of twenty-five years is not considered the limit, when both inside and 
outside of the pipe are treated with a coating of asphalt. 

The method of covering with asphalt referred to affords perfect protec- 
tion against corrosion, and so long as the coating is intact, makes it practi- 
cally indestructible so far as all ordinary wear is concerned. The conditions 
which interfere with the best service are where the coating is worn off by 
abrasion in transportation, or where the pipe is subject to severe shock by 
the presence of air, or by a sudden closing of the gates, or where the service 
is intermittent, causing contraction and expansion, which opens the joints 
and breaks the covering. With ordinary care these objections can mostly 
be overcome. While the primary object of coating pipe in this way is to 
prevent oxidization, and thus insure its durability, it is incidentally an ad- 
vantage in providing a smooth surface on the inside, which reduces the fric- 
tion of water in its passage. 

The Coast method of laying pipe is to take the shortest practicable dis- 
tance that the ground will permit, placing the pipe on the surface and con- 
necting directly from ditch, flume, or other source of supply to the wheel. 
Avoid short turns or acute angles, as they lessen the head and produce shock. 

The ordinary method of jointing is the slip joint, made up in much the 
same way as stove-pipe. Of course this is only adapted to comparatively 
low heads, special riveted-joint construction being necessary for the higher 
falls. In laying such pipe where the lengths come together at an angle, a 
lead joint should be made. This is done by putting on a sleeve, allowing a 
space, say three-eighths of an inch, for running in lead. With a heavy 
pressure, and especially on steep grades, the lengths should be wired 
together, lugs being pu* on the sections forming the joints for this purpose; 
and where the grade is very steep, the pipe should be securely anchored 
with wire cable. 

In laying the pipe line it is customary to commence at the wheel, and with 
slip joint the lower end of each length should be wrapped with cotton drill- 
ing or burlaps to prevent leaking ; care being taken in driving the joints 
together not to move the gate and nozzle from their position. Some tempo- 
rary bracing may be necessary to provide against this. 

Where several wheels are to be supplied from one pipe line, a branch 
from the main in the form of the letter Y is preferable to a right angle out- 
let. When taken from the main at a right angle, the tap-hole should be 
nearly as large as the main, reducing by taper joint to the size of pipe 
attached to the wheel gate. 

It is advised where practicable to lay the pipe in a trench, covering it 
with earth. Even in warm climates, where this is not necessary as protec- 
tion from frost, it is desirable to prevent contraction and expansion by 
variations of temperature, as well as to afford security against accident. 
When laid over a rocky surface a covering of straw or manure will protect 
it from the sun, and generally prevent freezing ; as where kept in motion, 
water under pressure will stand a great degree of cold without giving 
trouble in this way. After connections are made, it should be tested before 
covering to see that the joints are tight. 

Care should be taken when the pipes are first filled to see that the air is 
entirely expelled, the use of air valves being necessary in long lines laid 
over undulating surfaces. Care should also be taken before starting to see 
that there are no obstructions in the pipe or connections to wheel, and that 
there are no leaks to reduce the pressure. Pipe lines of any considerable 
length should be graduated as to size, being larger near the top and reduced 
toward the lower end, the thickness of iron for various sizes being deter- 
mined by the pressure it is to carry. This is a saving in first cost, and 
facilitates transportation by admitting of length, being run inside of each 
other. 

When used near railroad stations, pipe is generally made in 27 ft. lengths 
for purpose of economizing freight, this being the length of a car. When 
transported long distances by wagon, it is usually made in about 20 ft. 
lengths. For pipe of large diameter, or for transportation over long dis- 
tances, as also for mule packing, it is made in sections or joints of 24 to 30 
inches in length, rolled and punched, with rivets furnished to put together 



RIVETED STEEL PIPES. 



1467 



on the ground where laid. Pipe of this character, being cold riveted, is 
easily put together with the ordinary tools for the purpose. In such case, 
preparation should be made for coating with asphalt before laying. 

.Riveted steel pipes have also been extensively used in the East in the in- 
stallation of the new Avater supply for Newark, Jersey City and Paterson, 
N.J., also at Kochester, N.Y., and were furnished by Mr. Thos. H. Millson, 
of East Jersey Pipe Company, Paterson, N.J. 

Data of Rivet Spacing^ for Circular Seams of Pipe. 

Pipes 48" to 51" Diameter. 



Diameter of pipe . . 


. 


48 


48 


48 


51 


51 


51 


51 


Thickness .... 




§ 


A 

I 


1 
i 


I 
1 


T "W 


1 

3 


A 


Diameter of rivets . 


. 


1 


TF 

1 


Number of rivets . 


. 


100 


84 


74 


108 


92 


80 


64 


Length of long plate 


. 


151.582 


151.779 


151.975 


162.764 


163.354 


163.943 


164.532 


Length of short plate 




149.895 


149.717 


149.538 


161.007 


161.203 


161.399 


161.595 


Rivet pitch on long plate, 


1.515 


1.807 


2.053 


1.507 


1.776 


2.049 


2.571 


Rivet pitch on short plate, 


1.498 


1.782 


2.020 


1.491 


1.752 


2.017 


2.525 


Lap, center to edge . . . 


1 


ll 3 6 


If 


1 


It 3 * 


If 


1A 


Lap at circum., seams . . 


2 


2| 


2f 


2 


2| 


2| 


3i 



Data of Rivet Spacing-a for liOng-itudinal Seam* of Pipe. 



Number in first row . . 
Number in second row . 
Number in both rows . . 
Rivet pitch in both rows . 
Distance between rows . 
Lap, center to edge . . . 
Lap at longitudinal seam, 



35 


29 


25 


35 


29 


25 


34 


28 


24 


34 


28 


24 


69 


57 


49 


69 


57 


49 


2.277 


2.721 


3.125 


2.277 


2.721 


3.125 


1* 


1A 


lx 5 6 


1A 


It 3 * 


iA 


15 

IB 


1A 


m 


it 


1A 


m 


3 


3h 


4 


3 


n 


4 



22 
21 
43 

3.542 

II 

*A 

41 



This formula for the design of riveted steel pipe is taken from Cassier's 
Magazine, 1902 : — 

P=Zl ^ c T>_Ztf 

R ' } •" -Mb 

T= for iron, usually 48,000 lbs. per sq. in. 
T— for steel, 62,000 lbs. per sq. in. 
P = safe working pressure, per sq. in. 
t = thickness of sheet in inches. 
B = radius of pipe in inches. 
c = factor of safety : 3 to 3.5 for this work. 
/== proportional strength of plates after riveting: 

Double riveting ... 0.7 

Single riveting ... 0.5 

The Water Power Plant at Puyallup River near Tacoma will have a 
steel pipe line 1700 feet long, beginning 48" diameter, reducing to 36" diam- 
eter at the end, built by Ridson Iron Works, San Francisco, Cal. 



1468 WATER-POWER. 

In many cases much expense may be saved in pipe by conveying the 
water in a flume or ditch along the hillside, covering in this way a large 
part of the distance, then piping it down to the power station by a short 
line. This is more especially applicable to large plants, where the cos't of 
the pipe is an important item. 

DATA FOR FLinF^ 4*1> HITCHES. 

To give a general idea as to the capacity of flumes and ditches for carry- 
ing water, the following data is submitted : 

The greatest safe velocity for a wooden flume is about 7 or 8 feet per second. 
For an earth ditch this should not exceed about 2 feet per second. In Cali- 
fornia it is the general practice to lay a flume on a grade of about \ inch to the 
rod, or often 2 inches to the 100 feet, depending on the existing conditions. 

Assuming a rectangular flume 3 feet wide, running 18 inches deep, its 
velocity and capacity would be shown as below : 

Grade. Vel. in Ft. per Sec. Quantity Cu. Ft. Min. 

4 inch to rod 2.6 702 

J " " " 3.7 999 

} " " " 5.3 1,431 

As the velocity of a flume or ditch is dependent largely on its size and 
character of formation, no more specific data than the above can be given. 

It is not safe to run either ditch or flume more than about | or g full. 

WOODE.V^flVE PIPE. 

Wooden-stave pipe has been used to some extent on the Pacific Coast for 
conveying water long distances under heads not much exceeding 200 feet. 
Although the construction of such pipe is quite simple, yet considerable 
skill and care are necessary to make water-tight work. The plant of the 
San Gabriel Los Angeles Transmission, California, uses several miles of 
wooden-stave pipe, 48 ins. diameter. The pipe is laid uniformly ten feet 
below hydraulic grade; and the wood is of such thickness as to be always 
water-soaked, and will thus outlast almost any other form of construction. 

The staves are placed so as to break joints, the flat sides are dressed to a 
true circle, and the edges to radial planes. The staves are cut off square at 
the ends, and the ends slotted, a tight-fitting metallic tongue being used to 
make the joint. 

The pipe depends upon steel bands for its strength, and in the case above 
mentioned they are of round steel rod placed ten inches apart from center 
to center. Where the pressures vary along the line, bands can be spaced 
closer or wider apart to make the necessary strength. The preference is 
given round bands over flat ones, on account of their embedding themselves 
in the wood better as it swells. They also expose less surface to rust than 
would flat ones of the same strength. The ends of the bands are secured 
together through a malleable iron shoe, having an interior shoulder for the 
head of the bolt, and an exterior shoulder for the nut, the whole band thus 
being at right angles to the line of the pipe. Where curvesare not too 
sharp, they can easily be made in the wooden pipe ; but for short turns, sec- 
tions of steel-riveted pipe of somewhat larger internal diameter than that 
of the wooden pipe are introduced. The joints between wood and steel are 
made by a bell on the steel pipe that is larger than the outside diameter of 
the wooden pipe. After partly filling the space between bell and wood with 
oakum packed hard, for the remainder use neat Portland cement. 

Advantages claimed for this type are that it costs less than any other 
form, and especiallv so where transportation is over the rugged country 
where it is most liable to be used ; great length of lif e, and greater capacity 
than either casMron or steel-riveted. Compared with new riveted pipe, the 
carrying capacitv of stave pipe is said to be from 10 to 40 % more, and this 
difference increases with age as the wooden pipe gets smoother, while the 
friction of the metal pipe increases to a considerable degree. 

As compared with open flumes, the life is so much greater and repairs so 
much less as to considerably more than counterbalance the first cost. For 
detailed information on wooden-stave pipe, see papers by A. L. Adams, 
September, 1898, Am. Soc. C. E. 

Note. Mr. Arthur L. Adams writes that the pipe laid at Astoria, Ore., 

about which he wrote ten years ago has not proved lasting, one third of it 
hf ving been renewed during the first decade of its existence. 



RIVETED HYDRAULIC PIPE. 



1469 



lABIE ©* RIVETED HYDRAVIIC PIPI. 

(Pelton Water Wheel Co.) 
Showing weight, with safe head for various sizes of double-riveted pipe. 



ft 
ft . 

°.S 
1.5 
5.5 


ft 

ft . 
oq 

-5.5 


Thickness of 
iron by wire 
gauge. 


Head in feet 
the pipe will 
safely stand. 


Cu. ft. water 
pipe will con- 
vey per min. 
at vel. 3 ft. 
per sec. 


Weight per 
lineal ft. in 
lbs. 


ft 

ft . 

5.5 


ft 
'ft 
u_, 02 

*2 


Thickness of 
iron by wire 
gauge. 


Head in feet 
the pipe will 
safely stand. 


Cu. ft. water 
pipe will con- 
vey per min. 
at vel. 3 ft. 
per second. 


ft 


3 


7 


18 


400 


9 


2 


18 


254 


16 


165 


320 


16i 


4 


12 


18 


350 


16 


2* 


18 


254 


14 


252 


320 


20| 


4 


12 


16 


525 


16 


3 


18 
18 


254 
254 


12 
11 


385 
424 


320 
320 


27J 


5 


20 


18 


325 


25 


3 

5 


30 


5 


20 
20 


16 
14 


500 
675 


25 
25 


18 


254 


10 


505 


320 


34 


5 


20 
20 


314 
314 


16 
14 


148 
227 


400 
400 


18 


6 


28 


18 


296 


36 


4i 


22£ 


fi 


38 


16 


487 


36 


5| 
7i 


20 


314 


12 


346 


400 


30 


6 


28 


14 


743 


36 


20 
20 


314 
344 


11 
10 


380 
456 


400 
400 


32£ 
36£ 


7 
7 


38 


18 


254 


50 


3 

8| 


38 


16 


419 


50 


22 


380 


16 


135 


480 


20 


7 


38 


14 


640 


50 


22 
22 
22 


380 
380 

380 


14 
12 
11 


206 
316 
347 


480 
480 
480 


24f 
32f 
35f 


8 


50 


16 


367 


63 


3 


8 
8 


50 
50 


14 
12 


560 
854 


63 
63 


if 


22 


380 


10 


415 


480 


40 


9 
9 


63 
63 


16 
14 


327 
499 


80 
80 


81 

lOf 


24 
24 
?4 


452 
452 
45? 


14 
12 
11 


188 
290 
318 


570 
570 
570 


27i 
39 


9 


63 


12 


761 


80 


14i 


24 
24 


452 
452 


10 

8 


379 
466 


570 
570 


43£ 
53 


10 


78 


16 
14 
12 
11 


295 


100 
100 
100 
100 


9J 


10 
10 
10 


78 
78 
78 


450 
687 
754 


llf 
15| 
17* 


26 
26 
26 


530 
530 
530 


14 
12 
11 


175 
267 

294 


670 
670 
670 


42 


10 


78 


10 


900 


100 


26 
26 


530 
530 


10 

8 


352 
432 


670 
670 


47 


11 


95 


16 
14 
12 
11 


269 


120 
120 
120 
120 


9f 


57J 


11 
11 
11 


9b 
95 
95 


412 

626 

687 


13 
171 

18f 


28 

28 
?8 


615 
615 
615 


14 
12 
11 


102 
247 
273 


775 
775 

775 


31i 
45 


11 


95 


10 


820 


120 


21 


28 
28 


615 
615 


10 

8 


327 
400 


775 
775 


St 


12 


113 


16 


246 


142 
142 


Hi 


12 


113 


14 


377 


14 


30 


706 


12 


231 


890 


44 


12 
12 
12 


113 
113 
113 


12 
11 
10 


574 
630 
753 


142 
142 
142 


18| 
19| 
22| 


30 
30 
30 
30 


706 
706 
706 
706 


11 
10 
8 

7 


254 
304 
375 
425 


890 
890 
890 
890 


48 
54 
65 


13 


132 


16 


228 


170 


12 


74 


13 


132 


14 


348 


170 


15 


36 


1017 


11 


141 


1300 


58 


13 
13 
13 


132 
132 
132 


12 
11 
10 


530 
583 
696 


170 
170 
170 


20 
22 

24£ 


36 
36 
36 


1017 
1017 
1017 


10 
8 

7 


155 
192 
210 


1300 
1300 
1300 


67 

78 

88 


14 


153 


16 


211 


200 


13 


40 


1256 


10 


141 


1600 


71 


14 


153 


14 


324 


200 


16 


40 


1?56 


8 


174 


1600 


86 


14 


153 


12 


494 


200 


21* 


40 


1?56 


7 


189 


1600 


97 


14 


153 


11 


543 


200 


23£ 


40 


1256 


6 


213 


1600 


108 


14 


153 

176~ 

176 


10 


648 


200 


26 


40 


1256 


4 


250 


1600 


126 


15 
15 


16 
14 


197 
302 


225 
225 


13| 
17 


42 

4? 


1385 
1385 


10 
8 


135 

165 


1760 
1760 


74* 
91 


15 


IV b 


12 


460 


225 


23 


42 


1385 


7 


180 


1660 


102 


15 


J. 7 b 


11 


507 


225 


24* 


42 


1385 


6 


210 


1760 


114 


15 


IV b 


10 


606 


225 


28 


42 
42 


1385 
1385 


4 


240 
270 


1760 
1760 


133 


16 


201 


16 


185 


255 


14f 


137 


16 


201 


14 


283 


255 


m 


42 


1385 


3 


300 


1760 


145 


16 


201 


12 


432 


255 




42 


1385 


1 


321 


1760 


177 


16 


201 


11 


474 


255 


26£ 


42 


1385 


363 


1760 


216 


16 


201 


10 


567 


255 


29£ 















1470 



WATER-POWER. 



Cubic Feet of Water per TOLinute Discharged Through 
Orifice 1 Square Inch in Area. 





.For any other size of 


orifice, multiply by its area in square inches. 




*& 6 




V, 6 




V, 6 




V, © 




"8 ® 




V, ® 




V, ® 




4* S>£ 




-^ <» 4J 




+s ®g 




p »« 




4i »^ 




*? £-*> 




+» ©-S 


CO 

0> 


a> boa 


a> 


0) f-i £ 




<V U S 


CO 

CO 


<D ^ c 


CO 


<£> bfls 
fa c3.5 


CO 

a 


© *H - 


CO 

43 


© ^ a 


— 


fa ^.S 


A 


fa ^-2 


A 


fa g.9 


A 


fa si .5 


A 


A 


fa g.S 


— 


fa rt.a 


3s 


2.2 b 




2.2 fc 










c3 M 


2.2 s 






0QS 


2 JS^ 


CD g 


*Q£ 








g«£ 


$a 


^Pi 


X S 


gfli 




gs£ 


S 5 


ga£ 


3 


1.12 


13 


2.20 


23 


2.90 


33 


3.47 


43 


3.95 


53 


4.39 


63 


4.78 


4 


1.27 


14 


2.28 


24 


2.97 


34 


3.52 


44 


4.00 


54 


4.42 


64 


4.81 


5 


1.40 


15 


2.36 


25 


3.03 


35 


3.57 


45 


4.05 


55 


4.46 


65 


4.85 


6 


1.52 


16 


2.43 


26 


3.08 


36 


3.62 


46 


4.09 


56 


4.52 


66 


4.89 


7 


1.64 


17 


2.51 


27 


3.14 


37 


3.67 


47 


4.12 


57 


4.55 


67 


4.92 


8 


1.75 


18 


2.58 


28 


3.20 


38 


3.72 


48 


4.18 


58 


4.58 


68 


4.97 


9 


1.84 


19 


2.64 


29 


3.25 


39 


3.77 


49 


4.21 


59 


4.63 


69 


5.00 


10 


1.94 


20 


2.71 


30 


3.31 


40 


3.81 


50 


4.27 


60 


4.65 


70 


5.03 


11 


2.03 


21 


2.78 


31 


3.36 


41 


3.86 


51 


4.30 


61 


4.72 


71 


5.07 


12 


2.12 


22 


2.84 


32 


3.41 


42 


3.91 


52 


4.34 


62 


4.74 


72 


5.09 



Table Snowing* the Theoretical Velocity and Discharge in 
Cubic feet Through an Orifice of 1 Square Inch Issu- 
ing Under Mead* Varying from 1 to lOO feet. 





Theoreti- 


Theoret- 




Theoreti- 


Theoret- 




Theoreti- 


Theoret- 


.s • 


cal Dis- 


ical 




cal Dis- 


ical 


a . 


cal Dis- 


ical 


•d ® 


charge in 


Velocity 




charge in 


Velocity 


•d® 


charge in 


Velocity 


Sfa 


Cu. Ft. 


in Feet 


Sfa 


Cu. Ft. 


in Feet 


a>fa 


Cu. Ft. 


in Feet 


W 


per Min. 


per Min. 


a 


per Min. 


per Min. 


W 


per Min. 


per Min. 


1 


3.34 


481.2 


35 


19.77 


2847.6 


69 


27.74 


3997.1 


2 


4.73 


680.4 


36 


20.05 


2887.2 


70 


27.94 


4021.1 


3 


5.79 


833.4 


37 


20.33 


2926.8 


71 


28.14 


4054.5 


4 


6.68 


962.4 


38 


20.60 


2966.4 


72 


28.34 


4283.0 


5 


7.47 


1075.8 


39 


20.87 


3004.8 


73 


28.53 


4111.3 


6 


8.18 


1178.4 


40 


21.13 


3043.2 


74 


28.73 


4139.4 


7 


8.84 


1273.2 


41 


21.38 


3081.1 


75 


28.93 


4165.2 


8 


9.45 


1360.8 


42 


21.64 


3118.5 


76 


29.11 


4194.9 


9 


10.02 


1443.6 


43 


21.90 


3156.4 


77 


29.30 


4222.4 


10 


10.57 


1521.6 


44 


22.15 


3191.8 


78 


29.49 


4249.8 


11 


11.08 


1596.0 


45 


22.40 


3227.8 


79 


29.68 


4265.9 


12 


11.57 


1666.8 


46 


22.65 


3263.6 


80 


29.87 


4303.6 


13 


12.05 


1734.6 


47 


22.89 


3298.9 


81 


30.06 


4330.8 


14 


12.50 


1800.6 


48 


23.14 


3333.8 


82 


30.24 


4357.4 


15 


12.94 


1863.6 


49 


23.38 


3368.4 


83 


30.42 


4383.6 


16 


13.37 


1924.8 


50 


23.61 


3402.5 


84 


30.61 


4410.2 


17 


13.78 


1984.2 


51 


23.85 


3436.4 


85 


30.79 


4436.4 


18 


14.18 


2041.8 


52 


24.08 


3469.9 


86 


30.97 


4462.4 


19 


14.57 


2097.6 


53 


24.31 


3503.1 


87 


31.15 


4488.2 


20 


14.95 


2152.2 


54 


24.54 


3536.0 


88 


31.33 


4514.0 


21 


15.31 


2205.0 


55 


24.76 


3568.6 


89 


31.50 


4539.5 


22 


15.67 


2256.6 


56 


24.99 


3600.9 


90 


31.68 


4565.0 


23 


16.02 


2307.6 


57 


25.21 


3632.9 


91 


31.86 


4590.3 


24 


16.37 


2357.4 


58 


25.43 


3664.6 


92 


32.04 


4615.4 


25 


16.71 


2406.0 


59 


25.65 


3696.1 


93 


32.20 


4040.5 


26 


17.04 


2453.4 


60 


25.87 


3727.3 


94 


32.38 


4665.3 


27 


17.36 


2500.2 


61 


26.08 


3758.2 


95 


32.55 


4690.1 


28 


17.68 


2545.8 


62 


26.29 


3788.9 


96 


32.72 


4714.7 


29 


17.99 


2590.8 


63 


26.51 


3819.3 


97 


32.89 


4739.2 


30 


18.30 


2635.8 


64 


26.72 


3849.6 


98 


33.06 


4763.5 


31 


18.60 


2679.0 


65 


26.92 


3879.5 


99 


33.23 


4787.8 


32 


18.90 


2722.2 


66 


27.13 


3909.2 


100 


33.40 


4812.0 


33 


19.20 


2764.2 


67 


27.33 


3938.7 








34 


19.49 


2806.2 


68 


27.54 


3968.4 









THEORY OF ROD FLOAT GAUGING. 



1471 



flow of Water Throug-li an Orifice. 

a = area of orifice in square inches. 

Q = cubic feet discharged per minute. 

h = head in inches. 

#=.624 V^xa. 
The best form of aperture for giving the greatest flow of water is a coni- 
cal aperture whose greater base is the aperture, the height or length of the 
section of cone being half the diameter of aperture, and the area of the 
small opening to the area of the large opening as 10 to 16 ; there will be no 
contraction of the vein, and consequently the greatest attainable discharge 
will be the result. 



MEASUREMENT OF M.OW OE WATER IX A 
STREAM. 

The quantity of water 
flowing in a stream may 
be roughly estimated 
as follows : 

Find the mean depth 
of the stream by taking 
measurements at 10 or 
12 or more equal dis- 
tances across. Multi- 
ply this mean depth 
by the width of the 
stream, which will give 
the total cross-section 
of the prism. 

Find the velocity of 
the flow in feet per 




Fig. 28. 




minute, by timing a 
float over a measured 
distance, several times 
to get a fair average. 
Use a thin float, such 
as a shingle, so that it 
may not be influenced 
by the wind. 

The area or cross- 
section of the prism 
multiplied by the ve- 
locity per minute will 
give the quantity per 
minute in cubic feet. 

Owing to the friction 
of the bed and banks 
the actual flow is re- 
duced to about 83 per 
cent of the calculated 
flow as above. 



Fig. 29. 



THEORY OE ROD FLOAT OAUCHICG. 

(From Report on Barge Canal, 1901, Edward A. Bond, N. Y. State Engineer.) 

The hydrometric rod may consist of either a plain wooden rod of uniform 
diameter, weighted at its lower end with iron or lead pipe of equal diam- 
eter, so as to make it sink vertically in the water to nearly its full length, 



1472 WATER-POWER. 

or of a tin tube of uniform diameter, made either continuous or in sections 
fitting water-tightly into each other, and properly weighted with leaden 
shot, bullets, etc., at the bottom. If such a rod is placed carefully in the 
water, so as to prevent any vertical motion, and its projecting part is not 
acted upon by the wind, it may be assumed that in a short time it will move 
with the mean velocity of the water in the vertical plane in which it floats. 

When a straight cylindrical rod of uniform diameter is immersed verti- 
cally in a moving body of water and kept from sinking, it encounters 
therein filaments having different velocities in the direction of the stream, 
anil eventually acquires an intermediate velocity which is very nearly the 
mean of those acting upon it. Some of the fluid particles will be moving 
faster than the rod, while others move slower ; tne former will tend to 
accelerate the motion of the rod, both by direct pressure and by the lateral 
friction, while the latter tend to retard it. In the ensuing state of equili- 
brium and uniform motion, the accelerating and retarding forces acting 
on the rod must be equal, and will form a couple which causes the rod 
to assume a sMghtly inclined position in the water. Furthermore, when 
the channel is regular, and the rod reaches nearly to the bottom, the general 
law according to which the velocity of the successive filaments from the 
surface downwards varies, has been determined approximately by experi- 
ment, and it becomes possible to express the sums of the said accelerating 
and retarding forces in relatively simple mathematical terms. From the 
equality of these expressions, it is then found that the rod assumes the 
velocity of the water filament, which is located at a depth =0.61 X, where 
(L\\ denotes the immersed length of the rod. In like manner, the velocity 
\v x ) of the rod may also be compared with the computed or theoretical mean 
vel ocity (v 2 ) of all the water filaments in the vertical line or plane from the 
surface to the depth (X) ; and as it is found therefrom that (t' t ) is a little 
lesu than (v 2 ), it may be considered that (y x ) is equal to the mean velocity 
{vt*) for a depth a little greater than the said length (X). Under ordinary 
conditions in canals and rivers with regular channels and moderate veloci- 
ties, the immersed length (X) of the rod should be about 94% of the depth 
(T) of the water in the vertical plane of observation. 

From his extensive experiments at Lowell with such rods 2 inches in 
diameter and of different length (X) ranging from 87 to 99 per cent of the 
depth (T), the latter being made to vary from 8.1 to 9.5 feet, and with mean 
velocities (v m ) ranging from 0.5 to 2.8 feet per second, Francis deduced the 
following empirical formula for finding (vm) from the observed velocity (Vj) 
of the rod: 



, = v x ( 1.102 — 0.116 y V 



Commenting on the results given by this formula in comparison with the 
simultaneous observations of discharge over his standard weir, Mr. 
Francis states that taking the whole of the experiments together, the aver- 
age difference is about f of 1 per cent, and that the largest difference is an 
excess of about 3.7 per cent over the weir measurement when the velocity 
was only 0.5 foot per second. It is also probable that the above formula 
will not give trustworthy values of (vm) when the immersed length (X) of the 
rod is less than 75 per cent of the depth (T); hence it is desirable to make (X) 
as nearly equal to (T) as the character of the bed of the channel will permit. 

Practical Consideration. — In order that the work of gauging a 
water-course with rods may be prosecuted expeditiously and with fairly 
accurate results, certain practical considerations should be observed. The 
rods should be straight cylinders of uniform diameter having the smoothest 
practicable surface. Their diameter should be as small as is compatible 
with proper strength and stiffness, and the loading at the bottom should be 
concentrated so as to bring the center of gravity as low down as possible in 
the water, at the same time being rigidly attached so as to remain in place 
even if the rod is inverted. They should also have ample buoyancy, in order 
to bring them quickly to their normal depth of immersion after accidental 
submergence, and the projecting portion should be as short as possible con- 
sistent with the function of serving as a marker. In their experiments, 
Francis and Cunningham used tin tubes about 2 inches in diameter, while 
Grebenau and others used varnished wooden rods, having diameters from 
1.2 to 1.5 inches. Cunningham also used such rods, but gave the preference 
to the tubes. 



HORSE-POWER OF WATER. 



1473 



Miners' Inch Measurements. 

(Pelton Water Wheel Co.) 

Miners' inch is a term much in use on the Pacific Coast and in the mining 
regions, and is described as the amount of water flowing through a hole 1 
inch square in a 2-inch plank under a head of 6 inches to the top of the 
orifice. 

Fig. 28 shows the form of measuring-box ordinarily used ; and the follow- 
ing table gives the discharge in cubic feet per minute of a miners' inch 
of water, as measured under the various heads and different lengths and 
heights of apertures used in California. 



C3 


Openings 2 Inches High. 


Openings 4 Inches High. 


O b£ . 

rj S3 OQ 

SO* 


Head to 


Head to 


Head to 


Head to 


Head to 


Head to 


Center, 


Center, 


Center, 


Center, 


Center, 


Center, 


5 Ins. 


6 Inches. 


7 Inches. 


5 Inches. 


6 Inches. 


7 Inches. 




Cu.Ft. 


Cu. Ft. 


Cu. Ft. 


Cu. Ft. 


Cu. Ft. 


Cu. Ft. 


4 


1.348 


1.473 


1.589 


1.320 


1.450 


1.570 


6 


1.355 


1.480 


1.596 


1.336 


1.470 


1.595 


8 


1.359 


1.484 


1.600 


1.344 


1.481 


1.608 


10 


1.361 


1.485 


1.602 


1.349 


1.487 


1.615 


12 


1.363 


1.487 


1.604 


1.352 


1.491 


1.620 


14 


1.364 


1.488 


1.604 


1.354 


1.494 


1.623 


16 


1.365 


1.489 


1.605 


1.356 


1.496 


1.626 


18 


1.365 


1.489 


1.606 


1.357 


1.498 


1.62S 


20 


1.365 


1.490 


1.606 


1.359 


1.499 


1.63C 


22 


1.366 


1.490 


1.607 


1.359 


1.500 


1.631 


24 


1.366 


1.490 


1.607 


1.360 


1.501 


1.632 


26 


1.366 


1.490 


1.607 


1.361 


1.502 


1.633 


28 


1.367 


1.491 


1.607 


1.361 


1.503 


1.634 


30 


1.367 


1.491 


1.608 


1.362 


1.503 


1.635 


40 


1.367 


1.492 


1.608 


1.363 


1.505 


1.637 


50 


1.368 


1.493 


1.609 


1.364 


1.507 


1.639 


60 


1.368 


1.493 


1.609 


1.365 


1.508 


1.64C 


70 


1.368 


1.493 


1.609 


1.365 


1.508 


1.641 


80 


1.368 


1.493 


1.609 


1.366 


1.509 


1.641 


90 


1.369 


1.493 


1.610 


1.366 


1.509 


1.641 


100 


1.369 


1.494 


1.610 


1.366 


1.509 


1.642 



Note. — The apertures from which the above measurements were obtained 
were through material 1\ inches thick, and the lower edge 2 inches above the 
bottom of the measuring-box, thus giving full contraction. 

FI.OW Of WATER OVER WEIRS. 
Weir Dam Measurement. 

(Pelton Water Wheel Co.) 

Place a board or plank in the stream, as shown in Fig. 29, at some point 
where a pond will form above. The length of the notch in the dam should 
be from two to four times its depth for small quantities, and longer for 
large quantities. The edges of the notch should be beveled toward the 
intake side as shown. The overfall below the notch should not be less than 
twice its depth, that is, 12 inches if the notch is 6 inches deep, and so on. 

In the pond, about 6 feet above the dam, drive a stake, and then obstruct 
the water until it rises precisely to the bottom of the notch, and mark the 
stake at this level. Then complete the dam so as to cause all the water to 
flow through the notch, and, after time for the water to settle, mark the 
stake again for this new level. If preferred, the stake can be driven with 
its top precisely level with the bottom of the notch, and the depth of the 
water be measured with a rule after the water is flowing free, but the marki 



1474 



WATER-POWER. 



are preferable in most cases. The stake can then be withdrawn ; and the 
distance between the marks is the theoretical depth of flow corresponding 
to the quantities in the table. 

Francis's Formulae for Weirs. 



Weirs with both end contractions ) 
suppressed j 

Weirs with one end contraction \ 
suppressed j 

Weirs with full contraction . . 



As given by- 
Francis. 

Q =a 3.33lh* 

Q = 3.33(1 — Ah) ti* 

Q — 3.33(1 — ,2h)h? 



As modified by 
Smith. 

3.29 (*+£)** 
3.29lh* 



3.29 



(-a 



The greatest variation of the Francis formulae from the value of c given 
by Smith amounts to 3£ per cent. The modified Francis formulae, says Smith, 
will give results sufficiently exact, when great accuracy is not required, 
within the limits of h, from .5 feet to 2 feet, I being not less than 3 h. 

Q — discharge in cubic feet per second, I ±= length of weir in feet, h = 
effective head in feet, measured from the level of the crest to the level of 
still water above the weir. 

If Q / = discharge in cubic feet per minute, and V and W are taken in inches, 

the first of the above formulae reduces to Q / = OAl'h'* ■ The values are suf- 
ficiently accurate for ordinary computations of water-power for weirs 
without end contraction, that is, for a weir the full width of the channel 
of approach, and are approximate also for weirs with end contraction when 
I — at least 107*, but about 6 per cent in excess of the truth when I == 4ft. 

Weir Table. 
Table Showing the Quantity of Water Passing over Weirs in Cubic Feet 

per Minute. 



oo fl 

.a '-*"* 
+3 © u 



w E ° . o 

Be. P5«h*S ~ 

>5 'ji r-H a*.-. 

^ u % ° a, © 

2 u a ce ©►> 



4.85 
5.78 
6.68 
7.80 
8.90 
10.00 
11.23 
12.45 
13.72 
15.02 
16.36 
17.75 
19.17 
20.63 
22.11 
23.63 
25.20 
26.78 
28.43 
30.06 
31.75 
33.45 
35.22 
36.98 
38.80 
40.63 
42.49 
44.39 
46.29 
48.22 



« ° a 

J- Sh — ' 

III 

*l 

5 



^ 5 T3 fa ^ 

£ fc, 00 O g'S 

£ © 3 £ ® fc> 



50.20 
52.18 
54.22 
56.25 
58.33 
60.42 
62.55 
64.68 
66.86 
68.98 
71.27 
73.45 
75.77 
78.04 
80.36 
82.63 
85.04 
87.43 
89.82 
92.16 
94.67 
97.11 
99.50 
102.10 
104.63 
107.13 
109.74 
112.31 
114.91 
117.51 



O ° G 



-2 «H 

•a fc os a 


a 


fa .5 * w *» _d 

•2 ^ © ^ be i- 


oo fl 

5 © tH 


Cub 
per 
pass 
eacl 
Len 
Wei 


g-gg 


120.18 


m 


122.82 


12| 


125.52 


13 


128.14 


13i 


130.93 


13§ 


133.65 


13| 


136.43 


14 


139.18 


HI 


141.99 


14| 


144.80 


147.64 


15 


150.47 


m 


153.35 


15£ 


156.20 


15| 


159.14 


16 


162.07 


16J 


164.99 


16£ 


167.89 


16f 


169.92 


17 


173.90 


13 


176.92 


179.94 


17| 


182.99 


18 


186.03 


18* 


189.13 


18J 


192.20 


18| 


195.32 


19 


198.47 


m 

19} 


201.59 


207.94 


19} 



^ ^ EC o a © 

214.32 
220.76 
227.30 
233.92 
240.54 
247.22 
254.03 
260.83 
267.77 
274.70 
281.72 
288.82 
295.93 
303.10 
310.36 
317.69 
325.03 
332.42 
339.91 
347.45 
355.02 
362.77 
370.34 
378.12 
385.87 
393.66 
401.63 
409.58 
417.48 
425.68 



HORSE-POWER OF WATER. 



1475 



X 4 BJLES lOIt CALCULATING THE HORIE-POWER 
Of 1 IVAXElt. 

(Pelton Wheel Co.) 





Miners ' Inch Table. 




Cubic feet Table. 


The following table gives 


the horse- 


The following table gives the 


power 


of one miners' inch of water 


horse-power of 


one cubic foot of 


under heads from 


one up 


to eleven 


water per minute under heads from 


hundred feet. This inch equals 1£ 


one 


up to eleven hundred feet. 


cubic feet per minute. 












.5 


Horse- 


.9 

.SB'S 


Horse- 


B 


Horse- 


ej 

02 ** 


Horse- 




Power. 




Power. 


Power. 


IS® 


Power. 


w. 




w 




w 




H 




1 


.0024147 


320 


.772704 


1 


.0016098 


320 


.515136 


20 


.0482294 


330 


.796851 


20 


.032196 


330 


.531234 


30 


.072441 


340 


.820998 


30 


.048294 


340 


.547332 


40 


.096588 


350 


.845145 


40 


.064392 


350 


.563430 


50 


.120735 


360 


.869292 


50 


.080490 


360 


.579528 


60 


.144882 


370 


.893439 


60 


.096588 


370 


.595626 


70 


.169029 


380 


.917586 


70 


.112686 


380 


.611724 


80 


.193176 


390 


.941733 


80 


.128784 


390 


.627822 


90 


.217323 


400 


.965880 


90 


.144892 


400 


.643920 


100 


.241470 


410 


.990027 


100 


.160980 


410 


.660018 


110 


.265617 


420 


1.014174 


110 


.177078 


420 


.676116 


120 


.289764 


430 


1.038321 


120 


.193176 


430 


.692214 


130 


.313911 


440 


1.062468 


130 


.209274 


440 


.708312 


140 


.338058 


450 


1.086615 


140 


.225372 


450 


.724410 


150 


.362205 


460 


1.110762 


150 


.241470 


460 


.740508 


160 


.386352 


470 


1.134909 


160 


.257568 


470 


.756606 


170 


.410499 


480 


1.159056 


170 


.273666 


480 


.772704 


180 


.434646 


490 


1.183206 


180 


.289764 


490 


.788802 


190 


.458793 


500 


1.207350 


190 


.305862 


500 


.804900 


200 


.482940 


520 


1.255644 


200 


.321960 


520 


.837096 


210 


.507087 


540 


1.303938 


210 


.338058 


540 


.869292 


220 


.531234 


560 


1.352232 


220 


.354156 


560 


.901488 


230 


.555381 


580 


1.400526 


230 


.370254 


580 


.933684 


240 


.579528 


600 


1.448820 


240 


.386352 


600 


.965880 


250 


.603675 


650 


1.569555 


250 


.402450 


650 


1.046370 


260 


.627822 


700 


1.690290 


260 


.418548 


700 


1.126860 


270 


.651969 


750 


1.811025 


270 


.434646 


750 


1.207350 


280 


.676116 


800 


1.931760 


280 


.450744 


800 


1.287840 


290 


.700263 


900 


2.173230 


290 


.466842 


900 


1.448820 


300 


.724410 


1000 


2.414700 


300 


.482940 


1000 


1.609800 


310 


.748557 


1100 


2.656170 


310 


.499038 


1100 


1.770780 



When the Evact Head is found in Above Table. 

Example.— Have 100 foot head and 50 inches of water. How many 
horse-power ? 

By reference to above table the horse-power of 1 inch under 100 feet 
head is .241470. The amount multiplied by the number of inches, 50, will 
give 12.07 horse-power. 

When Exact Head is not found in Table. 

Take the horse-power of 1 inch under 1 foot head, and multiply by the 
number of inches, and then by number of feet head. The product will be 
the required horse-power. 

The above formula will answer for the cubic-feet table, by substituting 
the equivalents therein for those of miners' inches. 

Note.— The above, tables are based upon an efficiency of 85 percent. 



1476 



WATER-POWER. 



WATER-WHEELS. 

Undershot Wheels, in which the water passes under acting by im- 
pulse, when constructed in the old-fashioned way with flat boards as floats, 
have a maximum theoretical efficiency of 50 per cent ; but with curved floats, 
as in Poncelet's wheel, which are arranged so that the water enters without 
shock and drops from the floats into the tail-race without horizontal velo- 
city, the maximum efficiency is as great as for overshot wheels, and the 
available efficiency is found to be about 60 per cent. The velocity of the 
periphery should be about .5 of the theoretical velocity of the water due to 
the head. 

.Breast and Overshot Wheel*. 

The best peripheral velocity is about 6 feet per second, and for the water 
supplied to it about 12 feet per second, which is the velocity due to a fall of 
about 2J feet ; therefore, the point at which the water strikes the wheel 
should be 2\ feet below the top-water level. The chief cause of loss in over- 
shot wheels is the velocity which the water possesses at the moment it falls 
from the float or bucket ; overshot wheels are good for falls of 13 feet to 20 
feet ; below that breast wheels are preferable. The capacity of the buckets 
should be three times the volume of water held in each. The distance apart 
of the buckets may be 12 inches in high-breast and overshot wheels, or 18 
inches in low-breast wheels, while the opening of buckets may be 6 to 8 
inches in high-breast, and 9 inches to 12 inches in low-breast wheels. 

TVRBOES. 

These may be divided into two main classes, viz., pressure and impulse 
turbines. The former maybe again divided into the following: parallel- 
flow, outward-flow, and inward-flow turbines, according to the direction in 
which the water flows through the turbine in relation to its axis. 

Parallel-flow turbines, sometimes called downward-flow, are best 
suited for low falls, not exceeding say 30 feet. Fontaine's turbine is of this 
class, the wheel being placed at the bottom of the water-pipe or flume, just 
above the level of the tail-race. The water passes through guide blades and 
strikes the curved floats of the wheel. Jonval's turbine is of similar type, 
but is arranged to work partly by suction, and may be placed above the 
level of the tail-race without loss of power, which is often more convenient 
for working. The efficiency is from 70 to 72 per cent with well-designed 
wheels of this type. 




Fig. 30. Victor Wheel set in ordinary Flume. 

Outward-flow Turbines have a somewhat higher efficiency than the 
parallel-flow — as much as 88 per cent has been realized by Boyden's tur- 
bine ; Fourneyron's has given a maximum of 79 per cent. 

Inward-flow Turbines have been designed by Swain and others. 
Tests made on a Swain turbine by J. B. Francis gave a maximum effi- 
ciency of 84 per cent with full supply, and with the gate a quarter open 61 
per cent, the circumferential velocity of the wheel ranging from 80 to 60 
per cent of the theoretical velocity due to the head of water. In Swain's 
turbine the edges of the floats are vertical and opposite the guide blades, 



DIMENSIONS OF TURBINES. 



1477 



the edges towards the bottom of the floats being bent into a quadrant form. 
The Victor turbine is claimed to give 88 per cent under favorable conditions. 
It receives the water upon the outside, and discharges it downward and out- 
ward, the lines of discharge occupying the entire diameter of the lower portion 
of the wheel, excepting only the space tilled by the lower end of the shaft. 

Impulse Turbines are suitable for very high falls. The Girard and 
Pelton are both of this type. It is advised that pressure turbines be used 
on heads of 80 feet or 100 feet, but above this an impulse turbine is best. 
A Girard turbine is working under a fall of 650 feet. 
Installing: Turbines. 

Particular attention must be paid to the designing and construction of 
water-courses. The forebay leading to the flume should be of such size that 
the velocity of the water never exceeds 1* feet per second, and should be 
free from abrupt turns or other defects likely to cause eddies. The tail-race 
should have similar capacity and sufficient depth below the surface of the 
stream to allow at least 2 feet of dead water standing when the wheels are 
not in motion, and with large wheels, 3 feet to 4 feet ; after extending sev- 
eral feet beyond the flume, this may be gradually sloped up to the level of 
the stream. It is not uncommon to see 2 feet or 3 feet of head lost in 
defective races. 

When setting turbines some distance above the tail-race, the mouth of the 
draft-tube must be 2 inches to 4 inches below the lowest level of the stand- 
ing tail-water. Theoretically draft-tubes may be 30 feet long ; but 20 feet 
is as long as is desirable on account of the difficulty of keeping air-tight ; 
they should be made as short as possible by. placing the turbine at the 
bottom of the fall. 

Particulars of the setting recommended for Victor turbines are given 
below, as an example. 

Table of Dimensions of Victor Turbine. 





A. 


B. 


C. 


D. 


E. 


F. 1 


K. 


"3 


© 

© 

pd 

O 
© 

S3 


t © 
u_. co d 

<D *"< P 


i 

© 
© © 

S£© 


o 
u 

r-H © 

p © © 

®ii 

-u ec p 

3SS 


£ s 

«H » ©« M vV 

p^gS& 


m i 

o p,g 

© O O 

S ©<M • 


r-H U 

O.d^ 

o ^^ © 
£ A &od 


-M«H 

^ R ^ 5 © 


© 

rd 
S«M . 

do© 

Ord^ 

M bX)^ 

Bv ° 


In. 


In. 


In. 


Ft. 


In. 


In. 


In. 


O M BO ' 

+a © p £3 


Lbs. 


6 


10 


13* 


2 


12 


1 


5* 


fcfi£.2 J 


165 


8 


13* 


17* 
20* 


2* 


ion 


Kf 


W 


&*t* 


260 


10 


16 


3 


m 


7* 


'C'H P. 


350 


12 


18 T 3 S 


23 T 3 6 


3* 


28* 


m 


9| 


S°^ 


500 


15 

m 


Sr* 


28 X 3 S 
31* 
35* 


4 
5 


35* 


2 T 7 B 
2H 


11 
12f 




830 
1125 


20 


30* 


6 


37* 


3i\ 


13* 


© c3m-< qtf 


1475 


22* 
25 


33* 
35* 


40f 


6* 
6* 


42 
43f 


3 r 7 s 


14* 
15* 


© P « 
^©^ 


1900 
2335 


27* 


38* 


43| 


7* 


48*1 
50* 


311 


16* 


© d ® d 


3225 


30 


40* 


46 


8 


4| 


17* 


<H e8 ® O 


3540 


32* 


43* 


49* 


9 


55f 


*§ 


19* 


^ © t> 


4500 


35 


46* 


53 


9 


59 




20 


SjdS 


5450 


40 


52* 


60* 


10 


641 


5f 


22 


2<m § d . 

OOnOffl 
M „•>« O © 


7500 


44 

48 


56* 
60* 


65* 
70* 


11 
12 


67* 

74| 


5 4 


24 
26 


9380 
11700 


55 


68 


80 


14 


85* 


7* 


28 


19000 


63 


80* 


92 


16 


96* 


7| 


1 32 


oq'O O t* 





DIMENSIONS OF TURBINES. 

Tables of sizes of turbine wheels vary so much under different makers, 
and are so extensive, as not to permit their insertion here, but through the 
kindness of Mr. Axel Ekstrom of the General Electric Company I am per- 
mitted to print the following sheets of curves for the McCormick type 
turbine and the Pelton impulse wheel. From them may be made deter- 
minations of dimensions in much shorter time than is necessary by use of 
tables. 



1478 



WATEK-POWER. 



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Fig. 31. 



DATA ON HYDRAULIC TURBINES. 



1479 




Fig. 32. 



1480 



WATER-POWER. 



THE IMPtliE UlTEB.nUKKL. 



Mr. Ross E. Browne states that " The functions of a water-wheel, operated 
by a jet of water escaping from a nozzle, is to convert the energy of the jet, 
dii3 to its velocity, into useful work. In order to utilize this energy fully, 
the wheel bucket, after catching the jet, must bring it to rest before dis- 
charging it, without inducing turbulence or agitation of the particles. This 
cannot be fully eif ected, and unavoidable difficulties necessitate the loss of 
a portion of the energy. The principal losses occur as follows : 

" First : In sharp or angular diversion of the jet in entering, or in its 
course through the bucket, causing impact, or the conversion of a portion of 
thei energy into heat instead of useful work. 

"Second: In the so-called frictional resistance offered to the motion of 
the water by the wetted surfaces of the buckets, causing also the conver- 
sion of a portion of the energy into heat instead of useful work. 

"Third: In the velocity of the water as it leaves the bucket, represent- 
ing energy which has not been converted into work. 

4 Hence, in seeking a high efficiency, there are presented the following 
con. jiderations : 

" Lst. The bucket surface at the entrance should be approximately paral- 
lel (o the relative course of the jet, and the bucket should be curved in such 
a m inner as to avoid sharp angular deflection of the stream. If, for exam- 
ple, a jet strikes a surface at an angle and is sharply deflected, a portion of 
the water is backed, the smoothness of the stream is disturbed, and there 
results considerable loss by impact and otherwise. 

2d, The number of buckets should be small, and the path of the jet in the 
buqiV.et short ; in other words, the total wetted surface should be small, as 
the loss by friction will be proportional to this. 

44 Jl small number of buckets is made possible by applying the jet tangen- 
tial lj to the periphery of the wheel. 

44 3d. The discharge end of the bucket should be as nearly tangential to 
the irheel-periphery, as compatible with the clearance of the bucket which 
follows ; and great differences of velocity in the parts of the escaping 
waUr should be avoided. In order to bring the water to rest at the dis- 
charge end of the bucket, it is easily shown mathematically that the velo- 
city of the bucket should be one-half the velocity of the jet. 

44 in ordinary curved or cup bucket will cause the heaping of more or less 
dea I or turbulent water in the bottom of the bucket. This dead water is 
sub lequently thrown from the wheel with considerable velocity, and repre- 
sent s a large loss of energy. 

44 The introduction of the wedge in the bucket is an efficient means of 
av<\ (ding this loss." 

Wheels of this type are very efficient under high heads of water, and have 
been used to a great extent in the extreme western parts of the United 
Stages, where the fall is in hundreds of feet. It is difficult to say at what 
point of head the efficiency becomes such as to induce the use of some other 
form of wheel; but at 200 feet head the efficiencies of both impulse and tur- 
bine will be so much alike that selection must be governed by other factors. 

T3sts of one of the leading impulse wheels show efficiencies varying from 
80 % to 86 % according to head and size of jet. However, many factors 
besides the efficiency enter into selection of water-wheels, which must be 
subject to local conditions, and as in most water-power plants, each is r 
special case by itself, and selection of apparatus best fitted in all ways must 
govern. 



SHAFTING. 1481 

SHAFTING, PULLEYS, BELTING, ROPE- 
DRIVING. 

SHAFTOG. 

Thurston gives the following formulae for calculating power and size of 
shafting. 

H.P. = horse-power transmitted. 
d = diameter of shaft in inches. 
r =. revolutions per minute. 



For head shafts well For lron > HP - = 125 ; d = V r — 

supported against^ For cold . z, 

springing. r > lled iron HPt _ ^. ^_ y/^_^£j 

For line shafting [ For iron > ^ p - = W ; V ~ 



hangers 8 feet ^ For cold . 3/55 ATP 

a P art - r'lld iron, JT.P. = %~)d- $ °° Ur ' 

^ 55 V r 

f^ • r7 D «**•",, ?/625~HP. 

For transmission For iron > H.P. = ^gJ ^ = V r 

simply, no pul- J F o cold- ^ " */ WlLP. 
le y s - r'lld iron, H.P.= — — : d = V 

^ 3o " r 

Jones and Laughlin's use the same formulae, with the following excey 
tions : 

For line shafts, cold-rolled iron, H.P. r= — -; dz=\ : — -'. 

50 ' T r 

For transmission and for short-counters, 

™ , . „ n d 3 r _ . 3 /50 H.P. 

Turned iron H.P. = — — ; d =. v • 

50 ' t r 

Cold-rolled iron H.P. = — - ; d= V 

30 " r 

Pulleys should be placed as near to bearings as practicable, but cate 
should be taken that oil does not drip from the box into the pulley. 

The diameter of a shaft safe to carry the main pulley at the center oi a 
bay may be found by multiplying the fourth power of the diameter obtained 
by the formulae above given, by the length of the bay, and dividing the pro- 
duct by the distance between centers of bearings. The fourth root of tl le 
quotient will be the required diameter. 

The following table is based upon the above rule, and is substantially 
correct : 



1482 



SHAFTING, PULLEYS, BELTING, ETC. 



4) bC «M,£j 



Is* 



■2.3 ^8 



in. 

2 

24 

3 

3* 

4 

4* 
5 

54 
6 



Diameter of Shaft necessary to carry the Load at the Center of 
a Bay, which is from Center to Center of Bearings. 



24 ft. 



in. 
2§ 

24 
3 



3 ft. 



2i 

2f 
3| 
34 
4 



3* ft. 



2| 
2| 
3i 
3f 
44 
44 
5 



1ft. 



in. 
2* 



54 



5 ft. 



in. 
2| 
3 

?. 

44 



5| 
6| 



6 ft. 



in. 

2| 

3 



54 
5f 
6 



8 ft. 



m. 

24 
3f 
4 



54 
6 

64 



10 ft. 



in. 
3 

3| 
4 

4' 
& 
5| 
6 



Should the load be placed near one end of the bay, multiply the fourth 
power of the diameter of shaft necessary to safely carry the load at the cen- 
ter of the bay (see above table) by the product of the two ends of the shaft, 
and divide this product by the product of the two ends of the shaft where 
the pulley is placed in the center. The fourth root of this quotient will be 
the required diameter. 

A shaft carrying both receiving and driving pulleys should be figured as 
a head-shaft. 

Deflection of Shafting*. 

(Pencoyd Iron Works.) 

As the deflection of steel and iron is practically alike under similar con- 
ditions of dimensions and loads, and as shafting is usually determined by 
its transverse stiffness rather than its ultimate strength, nearly the same 
dimensions should be used for steel as for iron. 

For continuous line-shafting it is considered good practice to limit the 
deflection to a maximum of T £ 3 of an inch per foot of length. The weight 
of bare shafting in pounds = 2.6 d 2 L = W, or when as fully loaded with 
pulleys as is customary in practice, and allowing 40 lbs. per inch of width 
for the vertical pull of the belts, experience shows the load in pounds to be 
about 13 d 2 L = W. Taking the modulus of transverse elasticity at 26,000,000 
lbs., we derive from authoritative formulae the following: 

L=^/S73 d 2 , d = y — , for bare shafting; 

L = J/ 175 d 2 , d = y — , for shafting carrying pulleys, etc.; 

L being the maximum distance in feet between bearings for continuous 
shafting subjected to bending stress alone, d r= diam. in inches. 

The torsional stress is inversely proportional to the velocity of rotation, 
while the bending stress will not be reduced in the same ratio. It is there- 
fore impossible to write a formula covering the whole problem and suffi« 
ciently simple for practical application, but the following rules are correct 
within the range of velocities usual in practice. 

For continuous shafting so proportioned as to deflect not more than ^ 
of an inch per foot of length, allowance being made for the weakening 
effect of key-seats, 



f = \I WR.P. 



1 ,L= ^/720c?2 for bare shafts ; 



SHAFTING. 



1483 



7 



70 H.P. 



, L =y 140d 2 , for shafts carrying pulleys, etc. 



d = diam. in inches, L rr length in feet, r =z revols. per minute. 

The following table (by J. B. Francis) gives the greatest admissible dis- 
tances between the bearings of continuous shafts subject to no transverse 
strain, except from their own weight. 



Distance between 
Bearings in ft. 

f * \ 

Diam. of Shaft, Wrought-iron Steel 
in inches Shafts. Shafts 

2 15.46 15.89 

3 17.70 18.19 

4 19.48 20.02 

5 20.99 21.57 



Distance between 
Bearings in ft. 

t % 

Diam. of Shaft, Wrought-iron Steel 
in inches. Shafts. Shafts 

6 22.30 22.92 

7 23.48 24.13 

8 24.55 25.23 

9 25.53 26.24 



The writer prefers to apply a formula in all cases rather than use tables, 
as shafting is nearly always one-sixteenth inch less in diameter than the 
sizes quoted. The following tables are made up from the formulae first 
given in this chapter. 

Horse-Power Transmitted by Turned Iron Shafting-* 

As Prime Mover or Head Shaft well Supported by Bearings. 



s 








Revolutions per Minute. 








60 


80 


100 


125 


150 


175 


200 


225 


250 


275 


300 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


If 


2.6 


3.4 


4.3 


5.4 


6.4 


7.5 


8.6 


9.7 


10.7 


11.8 


12.9 


2 


3.8 


5.1 


6.4 


8 


9.6 


11.2 


12.8 


14.4 


16 


17.6 


19.2 


2J 


5.4 


7.3 


8.1 


10 


12 


14 


16 


18 


20 


22 


24 


2£ 


7.5 


10 


12.5 


15 


18 


22 


25 


28 


31 


34 


37 


2f 


10 


13 


16 


20 


24 


28 


32 


36 


40 


44 


48 


3 


13 


17 


20 


25 


30 


35 


40 


45 


50 


55 


60 


3+ 


16 


22 


27 


34 


40 


47 


54 


61 


67 


74 


81 


3* 


20 


27 


34 


42 


51 


59 


68 


76 


85 


93 


102 


3f 


25 


33 


42 


52 


63 


73 


84 


94 


105 


115 


126 


4 


30 


41 


51 


64 


76 


89 


102 


115 


127 


140 


153 


4* 


43 


58 


72 


90 


108 


126 


144 


162 


180 


198 


216 


5 


60 


80 


100 


125 


150 


175 


200 


225 


250 


275 


300 


5£ 


80 


106 


133 


166 


199 


233 


266 


299 


333 


366 


400 



Approximate Centers of Bearing's for Wrought Iron Li n«' 
Shafts Carrying- a fair Proportion of Pulleys. 



Shaft, Diameter Inches . . 


n 


If 


2 


2* 


2£ 


2| 


3 


3* 


4 


4* 


c. to c. Bearings — Feet . . 


7 


n 


8 


8* 


9 


9i 


10 


11 


12 


13 


Shaft, Diameter Inches . . 


5 


5* 


6 


6* 


7 
16 


17 


8 
18 


9 
19 


10 


c. to c. Bearings — Feet . . 


13* 


14 


15 


15* 


20 



1484 



SHAFTING, PULLEYS, BELTING, ETC. 



Line-shafting, Bearings 8 ft. Apart. 



i 

5 








Revolutions per Minute. 








100 


125 


150 


175 


200 


225 


250 


275 


300 
H.P. 


325 
H.P. 


350 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


If 


6 


7.4 


8.9 


10.4 


11.9 


13.4 


14.9 


16.4 


17.9 


19.4 


20.9 


13 


7.3 


9.1 


10.9 


12.7 


14.5 


16.3 


18.2 


20 


21.8 


23.6 


25.4 


2 


8.9 


11.1 


13.3 


15.5 


17.7 


20 


22.2 


24.4 


26.6 


28.8 


31 


2i 


10.6 


13.2 


15.9 


18.5 


21.2 


23.8 


26.5 


29.1 


31.8 


34.4 


37 


2i 


12.6 


15.8 


19 


22 


25 


28 


31 


35 


38 


41 


44 


2| 


15 


18 


22 


26 


29 


33 


37 


41 


44 


48 


52 


2* 


17 


21 


26 


30 


34 


39 


43 


47 


52 


56 


60 


2| 


23 


29 


34 


40 


46 


52 


58 


64 


69 


75 


81 


3 


30 


37 


45 


52 


60 


67 


75 


82 


90 


97 


105 


3i 

si 


38 


47 


57 


66 


76 


85 


95 


104 


114 


123 


133 


47 


59 


71 


83 


95 


107 


119 


131 


143 


155 


167 


58 


73 


88 


102 


117 


132 


146 


162 


176 


190 


205 


4 


71 


89 


107 


125 


142 


160 


178 


196 


213 


231 


249 



POWER TRANSMISSION ONLY. 



a 








Revolutions per Minute. 








100 


125 


150 


175 


200 


233 


267 


300 


333 


367 


400 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


n 


6.7 


8.4 


10.1 


11.8 


13.5 


15.7 


17.9 


20.3 


22.5 


24.8 


27.0 


if 


8.6 


10.7 


12.8 


15 


17.1 


20 


22.8 


25.8 


28.6 


31.5 


34.3 


if 


10.7 


13,4 


16 


18.7 


21.5 


25 


28 


32 


36 


39 


43 


i* 


13.2 


16.5 


19.7 


23 


26.4 


31 


35 


39 


44 


48 


52 


2 


16 


20 


24 


28 


32 


37 


42 


48 


53 


58 


64 


2* 


19 


24 


29 


33 


38 


44 


51 


57 


63 


70 


76 


2i 


22 


28 


34 


39 


45 


52 


60 


68 


75 


83 


90 


2| 


27 


33 


40 


47 


53 


62 


70 


79 


88 


96 


105 


2* 


31 


39 


47 


54 


62 


73 


83 


93 


104 


114 


125 


2f 


41 


52 


62 


73 


83 


97 


111 


125 


139 


153 


167 


3 


54 


67 


81 


94 


108 


126 


144 


162 


180 


198 


216 


»l 


68 


86 


103 


120 


137 


160 


182 


205 


228 


250 


273 


3£ 


85 


107 


128 


150 


171 


200 


228 


257 


285 


313 


342 



Horse-power Transmitted by Cold-rolled Iron Shafting-. 

AS PRIME MOVER OR HEAD SHAFT "WELL SUPPORTED BY BEARINGS. 



i 








Revolutions per 


Minute. 








3 


60 


80 


100 


125 


150 


175 


200 


225 


250 


275 


300 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H 


2.7 


3.6 


4.5 


5.6 


6.7 


7.9 


9.0 


10 


11 


12 


13 


If 


4.3 


5.6 


7.1 


8.9 


10.6 


12.4 


14.2 


16 


18 


19 


21 


2 


6.4 


8.5 


10.7 


13 


16 


19 


21 


24 


26 


29 


32 


21 


9 


12 


15 


19 


23 


26 


30 


34 


38 


42 


46 




12 


17 


21 


26 


31 


36 


41 


47 


52 


57 


62 


2f 


16 


22 


27 


35 


41 


48 


55 


62 


70 


76 


82 


3 


21 


29 


36 


45 


54 


63 


72 


81 


90 


98 


108 




27 


36 


45 


57 


68 


80 


91 


103 


114 


126 


136 


3£ 


34 


45 


57 


71 


86 


100 


114 


129 


142 


157 


172 


3f 


42 


56 


70 


87 


105 


123 


140 


158 


174 


193 


210 


4 


51 


69 


85 


106 


128 


149 


170 


192 


212 


244 


256 


4* 


73 


97 


121 


151 


182 


212 


243 


273 


302 


333 


364 



SHAFTING. 1485 

LINE-SHAFTING, BEARINGS 8 FT, APART. 



i 

S 








Revolutions per Minute. 








100 


125 


150 


175 


200 


225 


250 


275 


300 


325 


350 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


n 


6.7 


8.4 


10.1 


11.8 


13.5 


15.2 


16.8 


18.5 


20.2 


21.9 


23.6 


if 


8.6 


10.7 


12.8 


15 


17.1 


19.3 


21.5 


23.6 


25.7 


28.9 


31 


if 


10.7 


13.4 


16 


18.7 


21.5 


24.2 


26.8 


29.5 


32.1 


34.8 


39 


i* 


13.2 


16.5 


19.7 


23 


26.4 


29.6 


32.9 


36.2 


39.5 


42.8 


46 


2 


16 


20 


24 


28 


32 


36 


40 


44 


48 


52 


56 


2| 


19 


24 


29 


33 


38 


43 


48 


52 


57 


62 


67 


22 


28 


34 


39 


45 


50 


56 


61 


68 


74 


80 


2f 


27 


33 


40 


47 


53 


60 


67 


73 


80 


86 


94 


1 


31 


39 


47 


54 


62 


69 


78 


86 


93 


101 


109 


41 


52 


62 


73 


83 


93 


104 


114 


125 


135 


145 


3 


54 


67 


81 


94 


108 


121 


134 


148 


162 


175 


189 


3* 


68 


86 


103 


120 


137 


154 


172 


188 


205 


222 


240 


3i 


85 


107 


128 


150 


171 


192 


214 


235 


257 


278 


300 



POWER TRANSMISSION AND SHORT COUNTERS. 



i 








Revolutions pei 


Minute. 








s 


100 


125 


150 


175 


200 


233 


267 


300 


333 


367 


400 


Ins. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H.P. 


H 


6.5 


8.1 


9.7 


11.3 


. 13 


15.2 


17.4 


19.5 


21.7 


23.9 


*26 


H 


8.5 


10.7 


12.8 


15 


17 


19.8 


22.7 


25.5 


28.4 


31 


34 


H 


11.2 


14 


16.8 


19.6 


22.5 


26 


30 


33 


37 


41 


45 


if 


14.2 


17.7 


21.2 


24.8 


28.4 


33 


38 


42 


47 


52 


57 


if 


18 


22 


27 


31 


35 


41 


47 


53 


59 


65 


71 


n 


22 


27 


33 


38 


44 


51 


58 


65 


72 


79 


87 


2 


26 


33 


40 


46 


53 


62 


71 


80 


88 


97 


106 


2£ 
2* 


32 


40 


47 


55 


63 


73 


84 


95 


105 


116 


127 


38 


47 


57 


66 


76 


89 


101 


114 


127 


139 


152 


2§ 


44 


55 


66 


77 


88 


103 


118 


133 


148 


163 


178 


2| 


52 


65 


78 


91 


104 


121 


138 


155 


172 


190 


207 


2* 


69 


84 


99 


113 


138 


161 


184 


207 


231 


254 


277 


3 


90 


112 


135 


157 


180 


210 


240 


270 


300 


330 


360 



Hollow Shaft*. 

Let d be the diameter of a solid shaft, and d x d 2 the external and internal 
diameters of a hollow shaft of the same material. Then the shafts will be 

of equal torsional strength when d 3 = * 2 • 



A 10-inch hollow shaft with 



internal diameter of 4 inches will weigh 16 % less than a solid 10-inch shaft, 
but its strength will be only 2.56 % less. If the hole were increased to 5 
inches diameter the weight would be 25% less than that of the solid shaft, 
and the strength 4.25 % less. 

Table for laying* Out Shafting*. 

The table on the following page is used by Wm. Sellers & Co. for the lay- 
ing out of shafting. 



1486 



SHAFTING, PULLEYS, BELTING, ETC. 





Double 
Cone- 
Vise 
Coupl'g. 


•sgqoiri 

J0}9OIVI(X 


<tt - 3M5 J 3? , <o t~ i> oc a> O •■« c^rt^t-??©: ©> 




•89qoui 
4 q^Su97 


iSo t- oo*ci o «-* <n w "4"*^ qo as « uj ^ w'oo 5 




•aai 'xog jo Sui 
-j«9g jo q^Sugi 


^^OOCSC^CNeO^^OOg^^gOOgCM 




ob 


c 

c3 
oT 

00* 

Si 

© 

bo 
fl 

a 

a 



hi 

© 

■a 

ca 
W 

© 

e 

eS 

o 
AC 

? 
c 

4) 

S 
| 

© 
O 

fl 

« 

2 


Use of Table. — Look for size of first shaft in left-hand ool- 
umn, under the head of size of first shaft, and in the top line 
of table marked size of second shaft, find the size of the shaft 
to be coupled to it. The intersection gives the length B ; this 
added to the length A, or distance from center to center of 
bearing, and in cases similar to Fig. 34 to the length C, gives 
the length of the first shaft, thus : as in Fig. 33, B + A -f B z= 
length ; Fig. 34, C + A + B — length. 


Make bearings at equal 
distances from each 
other when practicable; 
always put 2 bearingson 
first, which is collared 
shaft. See Figs. 33 & 34. 


£ 






8$ 




t- 


§38 




i 
ff 


cn o5?Seo 




fc 


tsSaas 






sa&sfFs 


ii 

s 


s> 


sSlteSss 


> 

s 
m 


1 


sS , S , Sacl§5| , 


^< 


sSfsssJs&IT 


ii 

S 


# 

i 

$ 




- 


SstsSssjITa 


- 


*i 


«_h« p^«^ ?1<NCN g 


s 


WW 




1 


CM 


13 ^*£ 3Ti2 '"° ^ °^ 


In coupling shafts of dilt'erent 
sizes either reduce the end c4 
the large shaft in diameter and 
use a small coupling, or use a c 
ling to suit the larger shaft, > 
1 cone bored for smaller nomim 




§r 


m cTw « « "£* TrTdT 




1. 


•*» -4n -** 

•m — r< c^ ci m <*■ ia 




* 


cT©*^^^ 




§r 


-*» -*» 




8 a s 


Nominal 

Size of 

1st Shaft, 

ins. 


2Sl2?e* <?f (N<$f m c^«V ^*ift TAto y?t~ t?cc 




ii 


Length of 

Collared 

Knd for 

Fast Coll. 

ins. 


<$'•*"$'•«»??"£; 


?t- r- x © ~ 





i I- 



BELTING. 1487 



pvujnrs. 

Unwin says the number of arms is arbitrary, and gives the following 
values : 

a = Number of arms = for a single set = 3 -f- — -• 

d — diameter pulley. 

t == thickness of edge of rim of pulley — .75 inches -f .005rf. 
T— thickness of middle of rim of pulley = 2t -f c. 
b = breadth of rim of pulley = %(B-\- 0.4). 
B =: breadth of belt. 

for single belt = .6337 \ — 
h = breadth of arm at hub < . JL_ 



for double belt 



" a 



h x = breadth of arm at rim = § h. 

e = thickness of arm at hub = 0.4 h. 
e x == thickness of arm at rim — 0.4 h^. 

c = crowning z=z 5 X ? b. 

L — length of hub rz about § b. 

Reuleaux says pulleys of more than one set of arms may be considered 
as separate pulleys, except proportions of arms may be 0.8 to 0.7 that of 
single-arm pulleys. 

To Find Size of Pulley. 

D = diameter of driver, or No. teeth in gear. 
d =i diameter of driven, or No. teeth in pinion. 
Rev = revolutions per minute of driver. 
rev = revolutions per minute of driven. 

Rev B 

J D x Rev ' D x Rev 

d = — rev = ^ 

rev d 

BELTING. 

The coefficient of friction of belts on pulleys varies greatly, and it is there 
fore customary to use some arbitrary formula that has proved safe in 
practice. 

d =z diameter pulley in inches. 
nd = circumference. 
v = velocity of belt (or pulley face) in feet per minute. 
a = angle of arc of contact, commonly assumed as 180°. 

I = length of arc of contact in feet z= • 

Fz=. tractive force per square inch cross-section of belt. 
w — width of belt in inches. 
t = thickness of belt in inches. 

F 
S =3 tractive force per inch of width =s — • 

rpm =. revolutions per minute. 
n d 
v — ~l2 X r P m " 
_v w S _ d w S X rpm 
33000 ~ 126050 
A rule in common use for approximate determination of the H.P. of belts 
Cs, that a single belt 1 inch wide, traveling 1000 feet per minute, will trans- 
mit 1 horse-power. This corresponds to a strain on the belt of 33 lbs. per 
inch of width. 



1488 



SHAFTING, PULLEYS, BELTING, ETC. 



Authorities say single bells can be safely worked at 45 lbs. strain per 
inch of width, and on this basis 

jj p v w dw x rpm 

733 "" 2800 * 
Double belts are said to be able to transmit power in the ratio of 10 to 7 
for single belts. 

v w d w x rpm 

' 513 — 1960 

If the double belt is twice the thickness of the single belt, then it is fair 
to assume that it will transmit twice the power, and 

H. P. of double belt = _ = ^ ■ 

Jl, JF. Nagrle (Trans. A.S.M.E., vol. ii. 1881) gives the following 
formula 



H. P. of double belts : 



H. P. = CVtw 



(F— 0.012 V 2 \ 



550 ) 
Where C—\ — 10- 00758 ^. 

/= coefficient of friction. 

Horse •Power of a Belt one Inch Wide, Arc of Contact MO°. 

Comparison of Different Formulae. 



a 


d 












Form. 5 


Nagle's 


Form. 


>>u . 


>** . 


ft Ph 


Form. 1 


Form. 2 


Form. 3 


Form. 4 


Double. 


3 7 2 7/ single 




3 ^"S 




H.P. = 


H.P. = 


H.P. = 


H.P. = 


Belt 


Belt. 


c*> 3 




wv 


wv 


wv 


wv 


H.P. = 






H(»S 


*-h © fl 
















©©£ 




cc ©^ 


550 


1100 


1000 


733 


wv 
513* 


Laced. 


Riveted. 


10 


600 


50 


1.09 


.55 


.60 


.82 


1.17 


.73 


1.14 


30 


1200 


100 


2.18 


1.09 


1.20 


1.64 


2.34 


1.54 


2.24 


30 


1800 


150 


3.27 


1.64 


1.80 


2.46 


3.51 


2.25 


3.31 


40 


2400 


200 


4.36 


2.18 


2.40 


3.27 


4.68 


2.90 


4.33 


50 


3000 


250 


5.45 


2.73 


3.00 


4.09 


5.85 


3.48 


5.26 


60 


3600 


300 


6.55 


3,27 


3.60 


4.91 


7.02 


3.95 


6.09 


70 


4200 


350 


7.63 


3.82 


4.20 


5.73 


8.19 


4.29 


6.78 


80 


4800 


400 


8.73 


4.36 


4.80 


6.55 


9.36 


4.50 


7.36 


90 


5400 


450 


9.82 


4.91 


5.40 


7.37 


10.53 


4.55 


7.74 


100 


6000 


500 


10.91 


5.45 


6.00 


8.18 


11.70 


4.41 


7.96 


ilO 


6600 


550 




. . . 




• • • 




4.05 


7.97 


120 


7200 


600 










. . . 


3.49 


7.75 



"Width of Belt for a given Horse-Power. 

The width of belt required for any given horse-power may be obtained 
by transposing the formulae for horse-power so as to give the value of w. 
Thus : 

From formula (1), w =r 

From formula (2), w = 

From formula (3), w — 

From formula (4), w = 

From formula (5),* w = 

* For double belts. 



550 H. P. 9.17 H. P. 


2101 H. P. 


275 H. P. 


v V 


~ d X rpm 


~ L X rpm 


1100 H.P. 18.33 H.P. 


4202 H. P. 


530 H. P. 


v V 


~ d X rpm 


~ L X rpm 


1000 H. P. 16.67 H. P. 


3820 H. P. 


500 H.P. 


v V 


~ d x rpm 


~ L X rpm 


733 H. P. 12.22 H. P. 


2800 H. P. 


360 H.P. 


v V 


d X rpm 


~~ L < X rpm 


513 H. P. 8.56 H. P. 


1960 H. P. 


257 H. P. 


v V 


d X rpm 


~ L X rpm 



BELTING. 



1489 



\ x 3.14161 -f [2 x distance 



length of Belt. 

Approximate rule ; two pulleys I ( ^ — 

between centers] = length of belt. 

Leng-th of Belt in Roll. 

Outside diameter roll in inches 4- diameter hole x number turns x .1309 
= length of belt in inches for double belt. 

Weight of Belt (approximate). 



Length in feet x width in inches __ 



double belts. 



13 



weight of single belt. Divide by 8 for 



Horse-Power Transmitted by Tig-lit. Double Endless 
JLeather Belting 1 . 

(Buckley.) 



Width, 
Inches. 


4 


6 


8 


10 


12 


14 


16 


18 


20 


22 


24 


B 2000 


14 


22 


29 


36 


43 


50 


58 


65 


72 


80 


87 


H 2400 


17 


26 


35 


44 


52 


60 


70 


78 


88 


96 


105 


£ 2800 


20 


30 


40 


51 


61 


71 


81 


91 


102 


112 


122 


ft 3000 


22 


33 


44 


54 


65 


76 


87 


98 


108 


120 


131 


% 3500 


25 


38 


50 


63 


76 


89 


101 


114 


127 


140 


153 


© 4000 


29 


43 


58 


73 


87 


101 


116 


131 


145 


160 


174 


, 4500 
•- 5000 


32 


49 


65 


82 


98 


114 


131 


147 


163 


180 


196 


36 


55 


73 


91 


109 


127 


145 


163 


182 


200 


218 


% 5500 


40 


60 


80 


100 


120 


140 


160 


180 


200 


220 


240 


© 6000 

ft 

0Q 


44 


65 


87 


109 


130 


153 


175 


200 


218 


240 


260 



(Speed x width -^ 550 = horse-power, light, double.) 
(Horse-power x 550 -f- speed = width, light, double.) 

Horse-Power Transmitted by Heavy, Double Endless 
Leather Belting*. 



Width, 
Inches. 



& 2000 

S 2400 

fe 2800 

ft 3000 

t 3500 

© 4000 

a 4500 

■3 5000 

% 5500 

© 6000 

ft 



18 


27 


36 


21 


31 


42 


24 


36 


48 


27 


40 


53 


30 


45 


60 


35 


52 


70 


38 


59 


78 


43 


66 


87 


48 


72 


96 


52 


78 


104 



10 



43 
53 
61 
65 
75 
88 
98 
110 
120 
122 



12 



51 

62 
73 
78 
91 
104 
118 
130 
144 
153 



14 



60 
72 
85 
90 
106 
121 
137 
152 
168 
183 



16 



70 
83 
96 
104 
121 
139 
157 
174 
192 
210 



18 



80 
94 
109 
118 
137 
157 
176 
196 
216 
240 



20 



86 
105 
122 
129 
152 
174 
196 
218 
240 
262 



22 



96 
115 
135 
144 
168 
192 
216 
240 
264 
283 



24 



104 
120 
146 
157 
184 
209 
235 
262 
288 
312 



(Speed x width ~- 460 = horse-power, heavy, double.) 
(Horse-power x 460 -J- speed =; width, heavy, double.) 



1490 



SHAFTING, PULLEYS, BELTING, ETC. 



ROPE IMIi V IX*. 



Cr= Circumference of rope in inches. 
D — Diameter of pulley in feet. 
i?= Revolutions per minute. 



Horse-power of Rope : 



CxDxR _ 



200 



= H.P. 



or, Half the diameter of rope multiplied by the hundreds of feet per min- 
ute traveled. (L. I. Seymour.) 

Breaking strength of manila rope in pounds = C 2 X coefficient. The 
coefficient varies from 900 for £-inch to 700 for 2-inch diameter rope. The 
following is a reliable table prepared by T. Spencer Miller, M.E. (See En- 
gineering News, December 6, 1890.) 



Diameter. 


Circumference. 


Ultimate Strength. 


Coefficient. 


h 


n 


2,000 


900 


1 


2 


3,250 


845 


1 


2J 


4,000 


820 


| 


2| 


6,000 


790 


1 


3 


7,000 


780 


?! 


3* 


9,350 


765 


3f 


10,000 


760 


If 


1 


13,500 


745 


ll 


15,000 


735 


If 


5 


18,200 


725 


If 


5| 


21,750 


712 


2 


6 


25,000 


700 



This table was compiled by averaging and graduating results of tests at 
the Watertown Arsenal and Laboratory of Riehle Brothers, in Philadelphia. 

Weight of manila rope in pounds per foot =z .032 (Circumference in 
inches) 2 . (C. W. Hunt.) 

or, diameter of rope in inches squared = weight in pounds per yard ap- 
proximately. 

The coefficient of friction on a rope working on a cast-iron pulley z= 0.28 ; 
when working in an ungreased groove it is increased about three times, or 
from 0.57 to 0.84. If the pulleys are greased, the coefficient is reduced 
about one-half. It has been found by experiment that a rope 6 inches cir- 
cumference in a grooved pulley possesses four times the adhesive resistance 
to slipping, exhibited by a half-worn, ungreased 4-inch single belt. 

The length of splice should be 72 times the diameter of rope. The strength 
of a rope containing a properly made " long splice" was found to be 7,000 
pounds per square inch of section. 

A mixture of molasses and plumbago makes an excellent dope for trans- 
mitting ropes. Grease and oils of all kinds should be kept from transmis- 
sion ropes, since, as a rule, they are injurious. 

Following is another formula for horse-power of manila rope : 

jrp _ (T -QV 
' '~ 33000 ' 

in which H.P. is the horse-power transmitted by one rope, V the velocity in 
feet per minute, T the maximum working stress, and Cthe centrifugal 
tension, so that (T — C) is the net tension available for the transmission of 
power. Taking the total maximum stress at 200d 2 and allow 20 % of this 



for slack side tension, we have T t) = IGOd 2 , so that H.P. =■ 



(16 d 2 — C) V 
33,000 



A table has been calculated by this rule, giving the horse-power per rop«, 
transmitted at various speeds. 



ROPE DRIVING. 



1491 



C = Centrifugal Tension in Manila Ropes ~ Pounds. 



Velocity 
of Rope 
in ft. per 
Min. 








Nominal Diameter of Rope 


tn Inches. 






i 
2" 


f 


1 


3 


1 


li 


n 


If 


n 


If 


If 


2 


1000 


0.7 


1.1 


1.5 


2.1 


2.7 


3.4 


4.3 


5.1 


6.2 


7.2 


8.3 


11 


1500 


1.5 


2.4 


3.4 


4.7 


6.2 


7.6 


9.7 


11 


13 


16 


18 


25 


2000 


2.7 


4.3 


6.1 


8.2 


11 


13 


17 


20 


24 


28 


33 


44 


2500 


4.3 


6.7 


9.6 


13 


17 


21 


27 


32 


38 


45 


52 


69 


3000 


6.2 


9.7 


13 


18 


24 


30 


39 


45 


55 


64 


74 


100 


3500 


8.4 


13 . 


19 


25 


34 


42 


53 


63 


75 


89 


102 


136 


4000 


11 


17 


24 


33 


44 


54 


69 


82 


98 


116 


133 


177 


4500 


14 


22 


31 


42 


55 


69 


87 


103 


125 


146 


168 


223 


5000 


17 


27 


39 


52 


69 


86 


109 


129 


156 


183 


210 


275 


5500 


21 


33 


47 


63 


83 


104 


132 


156 


189 


221 


254 


332 


6000 


24 


39 


56 


75 


99 


125 


157 


188 


225 


257 


303 


396 


6500 


39 


45 


65 


88 


116 


145 


183 


217 


261 


307 


353 


462 



Horse-Power of Manila Ropes. 



Velocity 
of Rope. 
Ft. per 
Min. 




Nominal 


Diameter of Rope in 


Inches. 




h 


f 


I 


3 


1 


li 


li 


If 


H 


If 


If 


2 


2000 


2.25 


3.51 


5.14 


6.84 


9.08 


11.5 


14.0 


17.0 


20.3 


23.8 


27.5 


S6.1 


2100 


2.35 


3.67 


5.27 


7.15 


9.40 


11.8 


14.7 


17.8 


21.1 


24.8 


28.8 


37.6 


2200 


2.45 


3.82 


5.48 


7.45 


9.80 


12.3 


15.3 


18.5 


22.0 


25.9 


30.0 


39.2 


2300 


2.55 


3.98 


5.71 


7.75 


10.2 


12.8 


15.9 


19.3 


22.9 


26.9 


31.2 


40.8 


2400 


2.62 


4.10 


5.89 


7.98 


10.5 


13.2 


16.4 


19.8 


23.6 


27.7 


32.2 


42.0 


2500 


2.70 


4.21 


6.05 


8.21 


10.8 


13.6 


16.8 


20.4 


24.3 


28.5 


33.1 


43.2 


2600 


2.78 


4.33 


6.21 


8.43 


11.1 


14.0 


17.3 


21.0 


25.0 


29.3 


34.0 


44.4 


2700 


2.85 


4.45 


6.39 


8.67 


11.4 


14.4 


17.8 


21.5 


25.6 


30.5 


35.0 


45.6 


2800 


2.94 


4.59 


6.59 


8.93 


11.75 


14.8 


18.3 


22.2 


26.4 


31.0 


36.0 


47.0 


2900 


3.00 


4.68 


6.73 


9.13 


12.0 


15.1 


18.7 


22.7 


27.0 


31.6 


36.8 


48.0 


3000 


3.06 


4.78 


6.87 


9.32 


12.3 


15.4 


19.1 


23.2 


27.6 


32.3 


37.6 


49.1 


3100 


3.12 


4.87 


7.01 


9.50 


12.5 


15.7 


19.5 


23.6 


28.2 


33.0 


38.3 


50.0 


3200 


3.18 


4.97 


7.14 


9.70 


12.7 


16.0 


19.9 


24.0 


28.7 


33.7 


39.0 


51.0 


3300 


3.25 


5.07 


7.27 


9.89 


13.0 


16.3 


20.3 


24.5 


29.2 


34.3 


39.8 


52.0 


3400 


3.30 


5.15 


7.39 


10.0 


13.2 


16.6 


20.6 


25.0 


29.7 


34.8 


40.4 


52.8 


3500 


3.35 


5.22 


7.50 


10.2 


13.4 


16.9 


20.9 


25.3 


30.1 


35.4 


41.0 


53.6 


3600 


3.40 


5.30 


7.61 


10.3 


13.6 


17.1 


21.2 


25.7 


30.6 


35.9 


41.6 


54.4 


3700 


3.44 


5.36 


7.70 


10.4 


13.7 


17.3 


21.5 


26.0 


30.0 


36.3 


42.1 


55.0 


3800 


3.46 


5.40 


7.76 


10.5 


13.8 


17.4 


21.6 


26.2 


31.1 


36.6 


42.4 


55.4 


3900 


3.49 


5.45 


7.81 


10.6 


13.9 


17.6 


21.8 


26.4 


31.4 


36.9 


42.7 


55.8 


4000 


3.51 


5.49 


7.86 


10.6 


14.0 


17.7 


21.9 


26.5 


31.6 


37.1 


43.0 


56.1 


4100 


3.53 


5.52 


7.92 


10.7 


14.1 


17.8 


22.0 


26.7 


31.8 


37.3 


43.2 


56.4 


4200 


3.55 


5.54 


7.95 


10.8 


14.2 


17.9 


22.1 


26.8 


31.9 


37.5 


43.4 


56.8 


4300 


3.56 


5.55 


7.98 


10.8 


14.2 


17.9 


22.2 


26.9 


32.0 


37.6 


43.6 


56.9 


4400 


3.57 


5.56 


7.99 


10.8 


14.2 


18.0 


22.2 


27.0 


32.1 


37.6 


43.6 


57.0 


4500 


3.56 


5.55 


7.96 


10.8 


14.2 


17.9 


22.2 


26.9 


32.0 


37.6 


43.5 


56.9 


4600 


3.55 


5.54 


7-95 


10.8 


14.2 


17.9 


22.1 


26.8 


31.9 


37.5 


43.4 


56.8 


4700 


3.53 


5.50 


7.90 


10.7 


14.1 


17.8 


22.0 


26.6 


31.7 


37.2 


43.1 


56.4 


4800 


3.51 


5.48 


7.86 


10.7 


14.0 


17.7 


21.9 


26.5 


31.6 


37.1 


43.0 


56.2 


4900 


3.49 


5.45 


7.81 


10.6 


13.9 


17.6 


21.8 


26.4 


31.4 


36.9 


42.7 


55.8 


5000 


3.45 


5.38 


7.73 


10.5 


13.8 


17.4 


21.5 


26.1 


31.0 


36.4 


42.2 


55.2 


5100 


3.43 


5.35 


7.67 


10.4 


13.7 


17.2 


21.3 


25.9 


30.8 


36.2 


41.9 


54.8 


5200 


3.38 


5.26 


7.56 


10.2 


13.5 


17.0 


21.0 


25.5 


30.4 


35.6 


41.3 


54.0 


5300 


3.34 


5.20 


7.47 


10.1 


13.3 


16.8 


20.8 


25.2 


30.0 


35.2 


40.8 


53.4 


5400 


3.28 


5.11 


7.34 


9.95 


13.1 


16.5 


20.4 


24.8 


29.4 


34.6 


40.1 


52.5 


5500 


3.21 


5.00 


7.20 


9.75 


12.8 


16.2 


20.0 


24.2 


28.9 


33.9 


39.3 


51.4 


6000 


2.78 


4.33 


6.21 


8.43 


11.1 


14.0 


17.3 


21.0 


25.0 


29.3 


34.0 


44.4 


6500 


2.17 


3.38 


4.85 


6.60 


8.6 


10.9 


13.5 


16.4 


19.5 


22.9 


26.5 


34.7 



1492 



SHAFTING, PULLEYS, BELTING, ETC. 



HORSE POWER 







































^f 


































■? 


3 


f 


































A 


/ 
































4 


/ 


/ 
































J 


/ 


/ 


































/ 




/ 
































/ 


/ 


/ 


































/ 


/ 


































/ 




I 
/ 
































/ 




j 


1 






















) 


/ 








l 
I 




/ 


































1 








































































































\ 










I 




\ 


























\ 








\ 






























\ 














\ 






































\ 






































\ 














ROPE DRIVING 

HORSE POWER OF MANILLA ROPE 
AT VARIOUS SPEEDS 




















\ 


























































\ 


V 






























\ 






























\ 
































,iN 


» V 


A 






















% 


* 




k 


f 


V 
























N/- 




rS 


k 






























v \ 











































i fe 

> o 



8 > 



5 3 



OOOCO^NOOO^^OJ 



Fig. 36. 



ROPE DKIVING. 



1493 



Horse-Power of " Stevedore " Transmission Rope at 
Various Speeds. 

In this table the effect of the centrifugal force has been taken into con- 
sideration, and the strain on the fibers of the rope is the same at all 
speeds when transmitting the horse-power given in the table. When more 
than one rope is used, multiply the tabular number by the number of the 
ropes. At a speed of 8,400 per minute the centrifugal force absorbs all the 
allowable tension the rope should bear, and no power will be transmitted. 





Table of the Horse-Po 

(Hunt's '. 


wer of Transmission Rope. 

Formula.) 




«M 
O 

u 

P ft 


Speed of the Rope in Feet per Minute. 


a 


q 


1,500 


2,000 


2,500 


3,000 


3,500 


4,000 


4,500 


5,000 


6,000 


7,000 


8,400 


in 


h 


1.45 


1.9 


2.3 


2.7 


3. 


3.2 


3.4 


3.4 


3.1 


2.2 


.0 


.20 


5 
8 


2.3 


3.2 


3.6 


4.2 


4.6 


5.0 


5.3 


5.3 


4.9 


3.4 


.0 


.25 


t 


3.3 


4.3 


5.2 


5.8 


6.7 


7.2 


7.7 


7.7 


7.1 


4.9 


.0 


.30 


I 


4.5 


5.9 


7.0 


8.2 


9.1 


9.8 


10.8 


10.7 


9.3 


6.9 


.0 


.36 


1 


5.8 


7.7 


9.2 


10.7 


11.9 


12.8 


13.6 


13.7 


12.5 


8.8 


.0 


.42 


H 


9.2 


12.1 


14.3 


16.8 


18.6 


20.0 


21.2 


21.4 


19.5 


13.8 


.0 


.54 


H 


13.1 


17.4 


20.7 


23.1 


26.8 


28.8 


30.6 


30.8 


28.2 


19.8 


.0 


.60 


if 


18. 


23.7 


28.2 


32.8 


36.4 


39.2 


41.5 


41.8 


37.4 


27.6 


.0 


.72 


2 


23.2 


30.8 


36.8 


42.8 


47.6 


51.2 


54.4 


54.8 


50. 


35.2 


.0 


.84 



For a temporary installation w r hen the rope is not to be long in use, it 
might be advisable to increase the work to double that given in the tables. 

Slip of Ropes and Relts. 

(W. W. Christie.) 
Some French trials, with constant resistance, the power expended and 
slip in several modes of transmission was as follows : 

Ropes, 158.54 gross h.p., Slip, 0.33 per cent. 

Cotton belt, 159.67 " " 0.78 " 

Leather " 158.84 " " 0.96 " 

" " 160.23 " " 0.78 " 

Stated in percentage value, the results were : 

Ropes, 100.00 gross power, Slip, 0.100. 

Cotton belt, 100.87 " " 0.237. 

Leather " 100.37 " " 0.292. 

" " 101.07 " " 0.237. 



( 



1494 



SHAFTING, PULLEYS, BELTING, ETC. 



Manila Cordage. 


Tarred 
Hemp. 


Size, Cir- 


Size, 


Weight of 


Feet in 


Breaking Strain 


Weight of 


cumfer'ce. 


Diameter. 


100 


one 


of New Ropes. 


100 


Inches. 


Inches. 


Fathoms. 


Pound. 


Pounds. 


Fathoms. 










For Ropes in use 




li 


3 

8 


31 


20 


deduct £ from 


40 


1* 


1 


44 


14 


these figures, for 


55 


If 


9 
l 6 


60 


10 


chafing, etc. 


75 


2 


79 


n 


3000 


100 


21 


1 


99 


6 


4000 


125 


2§ 


tl 


122 


5 


5000 


155 


2| 


i 


146 


4 


6000 


190 


3 


i 


176 


3§ 


7000 


225 


31 


H* 


207 


3 


8500 


265 


3* 


i£ 


240 


2i 


9500 


300 


3| 


ij 


275 


% 


11000 


355 


4 


1 s 

if 


305 


2 


12500 


405 


4i 


355 


If 


14000 


455 


3 


If 


395 


16000 


500 


5 


If 


490 


H 


20000 


630 


5* 


If 


595 


l 


24000 


750 


6 


2 


705 


10 in. 


27000 


910 


6£ 


2J 


825 


8i 


31500 


1050 


7 


2i 


960 


n 


37000 


1235 


n 


2f 


1100 


ei 


42500 


1400 


8 


2f 


1255 


ii 


4850o 


1600 


8* 


n 


1415 


5 


54500 


1820 


9 


3 


1585 


4* 


61500 


2050 



Hawser laid will weigh £ less. 
Notes on the Uses of Wire Rope. 

(Roebling.) 

Two kinds of wire rope are manufactured. The most pliable variety con- 
tains 19 wires in the strand, and is generally used for hoisting and running 
rope. 

For safe working load allow £ or £ of the ultimate strength, according to 
speed, so as to get good wear from the rope. Wire rope is as pliable as new 
hemp rope of the same strength ; but the greater the diameter of the 
sheaves the longer wire rope will last. 

Experience has proved that the wear increases with the speed. It is, 
therefore, better to increase the load than the speed. Wire rope must not 
be coiled or uncoiled like hemp or manila — all untwisting or kinking must 
be avoided. 

In no case should galvanized rope be used for running. One day's use 
scrapes off the zinc coating. 



Table of Strains Produced lij 


Load* on Inclined Planes. 




Strain in Lbs. on 


Elevation in 
100 Ft. 


Strain in Lbs. on 


Elevation in 100 Ft. 


Rope from a Load 


Rope from a Load 




of 1 Ton. 


of 1 Ton. 


Ft. Deg. 




Ft. Deg. 




10= 5£ 


212 


90 = 42 


1347 


20=1U 
30=16f 


404 


100 = 45 


1419 


586 


110 = 47| 


1487 


40=21| 
50 = 26| 


754 


120 = 50J 


1544 


905 


130 = 52| 


1592 


60=31 


1040 


140 = 54* 


1633 


70 = 35 


1156 


150 = 56J 


1671 


80 = 38§ 


1260 


160 = 58 


1703 



WIRE ROPE. 



1495 



Table of Transmission of Power by Wire Ropes. 

Showing necessary size and speed of wheels and rope to obtain any de- 
sired amount of power. 

(Roebling.) 



Diam. 

of 
Wheel 
in Ft. 



No. of Rev- 


Diam. 
of 


Horse- 


Diam. 

of 


olutions. 


Rope. 


Power. 


Wheel 
in Ft. 


80 


1 


3.3 


10 


. 100 


1 


4.1 




120 


1 


5. 




140 


1 


5.8 




80 


ft 


6.9 


11 


100 


& 


8.6 




120 


A 


10.3 




140 


T 7 8 


12.1 




80 


1 


10.7 


12 


100 


£ 


13.4 




120 


\ 


16.1 




140 


\ 


18.7 




80 


9 
T5 


16.9 


13 


100 


ft 


21.1 




120 


9 
15 


25.3 




80 


f 


22. 


14 


100 


f 


27.5 




120 


1 


33. 




80 


§ 


41.5 


15 


100 


§ 


51.9 




120 


f 


62.2 





No. of Rev- 
olutions. 



80 
100 
120 
140 



100 
120 
140 

80 
100 
120 
140 

80 
100 
120 

80 
100 
120 

80 
100 
120 



Diam. 

of 
Rope. 



Horse- 
Power. 



58.4 
73. 
87.6 
102.2 

75.5 
94.4 
113.3 
132.1 

99.3 
124.1 
148.9 
173.7 

122.6 
153.2 
183.9 

148. 
185. 
222. 

217. 

259. 
300. 



Note. For list of transmission ropes, see page 1325. 

The drums and sheaves should be made as large as possible. The mini- 
mum size of drum is given in a column in table. 

It is better to increase the load than the speed. 

Wire rope is manufactured either with a wire or a hemp center. The 
latter is more pliable than the former, and will wear better where there is 
short bending. The weight of rope with wire center is about 10 per cent 
more than with hemp center. 



1496 



CHAINS. 



€HAIH[. 

The size of chain is determined by the size of the stock used in making 
the links. 

The strength of the iron always used for chains is from 41,000 to 55,000 lbs. 
tensile strength per square inch. 

Coil Chain. 

(John C. Schmidt & Co., York, Pa.) 



Size of 


Links 


Av. Weight 


Proof 


Size of 


Links 


Av. Weight 


Proof 


Iron 


per 
Foot. 


per 100 


Load in 


Iron 


per 


per 100 


Load in 


in Ins. 


Ft. in Lbs. 


Lbs. 


in Ins. 


Foot. 


Ft. in Lbs. 


Lbs. 


3-16 


13 


45 


600 


1-2 


8 


225 


7,000 


1-4 


12 


75 


1,400 


9-16 


7 


320 


9,000 


5-16 


11 


120 


2,500 


5-8 


6 


400 


11,000 


3-8 


10 


150 


4,000 


3-4 


5* 


590 


16,000 


7-16 


9 


200 


5,000 


7-8 


5 


770 


22,000 



Short I*i nk Chains. 

Proof Tests Adopted November 11, 1896. 
(Jones & Laughlins, Limited.) 



Size. 
(Ins.) 


Proof. 
(Lbs.) 


BB 

Crane. 
(Lbs.) 


BBB 

Crane. 
(Lbs.) 


Average 

Weight 

per Foot. 

(Lbs.) 


* 


700 


770 


900 


.5 


1,200 


1,320 


1,500 


.9 


t 


2,500 


2,750 


3,200 


1.22 


3,500 


3,850 


4,425 


1.6 


t 


4,800 


5,280 


6,100 


2.0 


6,200 


6,820 


7,850 


2.5 


A 


7,800 


8,580 


9,870 


3.2 


I 


9,600 


10,560 


12,150 


4.2 


¥ 


11,500 


12,650 


14,550 


5.0 


13,800 


15,180 


17,475 


5.9 


? 


16,200 


17,820 


20,500 


6.7 


18,800 


20,680 


23,780 


7.9 


if 


21,500 


23,650 


27,200 


9.0 




24,600 


27,100 


31,200 


10.2 


li- 


26,300 


28,930 


33,300 


11.4 


29,500 


32,450 


37,300 


12.7 


lt 


33,000 


36,300 


41,750 


14.2 


36,500 


40,150 


46,175 


15.8 


it 


40,000 


44,000 


50,600 


17.2 


44,000 


48,400 


55,660 


18.8 


it 


48,200 


53,000 


60,950 


20.4 


52,500 


57,750 


66,400 


22.2 


it 


57,000 


62,700 


72,100 


24.0 


61,700 


67,870 


78,050 


26.7 


W 


66,500 


73,150 


84,120 


28.5 


71,600 


78,760 


90,575 


31.0 



Safe working load should be about one-half of proof test. 
The breaking strain is about double the proof test. 



LUBRICATION. 1497 



IlBKItlTIOX. 

When two bodies are compelled to move, one upon the other, the resist- 
ance encountered is called friction, of which we have three kinds : rolling 
and sliding of solids, and fluid friction of liquids and gases. 

The reduction of friction and its consequent generation of heat is accom- 
plished to a large extent by the use of lubricants. 

Thurston says the characteristics of an efficient lubricant must be : 

1. Enough " body," or combined capillarity and viscosity to keep the sur- 
faces between which it is interposed from coming in contact under maxi- 
mum pressure. 

2. The greatest fluidity consistent with the preceding requirements. 

3. The lowest possible co-efficient of friction under the conditions of 
actual use, i.e., the sum of the two components, solid and fluid friction, 
should be a minimum. 

4. A maximum capacity for receiving, transmitting, storing, and carrying 
away heat. 

5. Freedom from tendency to decompose, or to change in composition by 
gumming or otherwise, on exposure to the air while in use. 

6. Entire absence of acid or other properties liable to produce injury of 
materials or metals with which they may be brought in contact. 

7. A high temperature of evaporization and of decomposition and a low 
temperature of solidification. 

8. Special adaptation to the conditions as to speed and pressure of rubbing 
surfaces under which the unguent is to be used. 

9. It must be free from grit and all foreign matter. 

All Animal or Vegetable Oils eventually decompose, and become 
gummy, and retard the speed of any machine to which they may be applied. 

mineral Oils — which are used in steam and electrical engineering— 
do not absorb oxygen, and do not take fire spontaneously, as do the animal 
and vegetable oils. 

Greases have their proper place, as in railroad car axles, and in cups 
feeding journals that do not require lubrication until a certain predeter- 
mined temperature has been reached, for which the grease to be used is 
suited. 

Vegetable Oils should not be used in anyplace from which there is 
any prospect of their being taken to the inside of a steam boiler, as they 
materially encourage corrosion and pitting of boiler shells. 

Weigrht of Oil per Gallon. The Pennsylvania Railroad specifica- 
tions call for these approximate weights : Lard oil, tallow oil, neatsfoot oil, 
bone oil, colza oil, mustard-seed oil, rape-seed oil, paraffin oil, 500 degree fire 
test oil, engine oil, and cylinder lubricant, 7£ pounds per gallon. 

Well oil and passenger car oil 7.4 lbs. per gallon. 

Navy sperm oil 7.2 " " " 

Signal oil , , 7.1" " " 

300 degree burning oil 6.9 " " " 

150 degree burning oil 6.6 " " " 

In many of the large power plants the lubrication of a large proportion of 
the bearings is controlled by a system which pumps the oil through pipes to 
bearings, and after its use, it is drained to a central point there to be filtered, 
and foreign matter eliminated, and then used over again. 

Lubrication is more apt to be overdone than to be neglected to damage of 
machinery. 



( 



1498 



LUBRICATION. 



Best & ub ri cants for Different Purposes. 

(Thurston.) 



Low temperatures, as in rock drij 
driven by compressed air . . 

Very great pressures, slow speed 
Heavy pressures, slow speed . 
Heavy pressures, high speed . 
Light pressures, high speed 

Ordinary machinery .... 
Steam cylinders 



Watches and other delicate mech- 
anisms 



I Light mineral lubricating oils. 

( Graphite, soapstone and other solid 

( lubricants. 

( The above, lard and tallow and other 

\ greases. 

( Sperm-oil, castor-oil, and heavy 

( mineral oils. 

( Sperm, refined, petroleum, olive, 

( rape, cotton-seed oils. 

!Lard oil, tallow oil, heavy mineral 
oils, and the heavier vegetable 
oils. 
Heavy mineral oils, lard, tallow. 
( Clarified sperm, neatsfoot, porpoise, 
< olive, and light mineral lubricat- 
( ing oils. 



For mixture with mineral oils, sperm is best ; lard is much used ; olive and 
cotton-seed oils are good. 



After making a series of exposure tests to ascertain the efficiency of lead 
and zinc paints, G. R. Henderson, N. & W. Railroad, reaches the following 
conclusions. 

Tin. — The best results were obtained with the first coat white lead, and 
second coat, white zinc. The second coating of zinc gave generally the best 
results, and the second coating of lead the most. 

Galvanized Iron. — The same remarks apply to galvanized iron as 
given for tin. 

Sheet Iron. — The mixture of one-third white zinc and two-thirds white 
lead, for both coats, gave the best results on this material, and, in general, 
the zinc paint gave better results than the lead paints. 

Poplar. — The second coats of zinc showed up well on poplar, no matter 
whether the priming coats were Avhite lead or white zinc, or mixed lead and 
zinc. The lead second coating showed up the most on this material, but in 
each case where the second coat was of zinc, totally or partially, the paint 
was in a perfect condition. 

White Pine. — The same remarks apply to white pine as to poplar. 

Yellow Pine. — This material seems to be difficult to properly treat 
with paints ; the best results were obtained with the first coat of lead, and 
the second coat of lead and zinc mixed. Where the first coat was of lead 
and zinc mixed or entirely of zinc, the results were poor throughout, which 
seems to indicate that as a general thing the lead is better for priming on 
this material/ 

Conclusion. — Lead priming and zinc coating are generally good for 
tin, galvanized iron, poplar and white pine. Sheet iron shows up best with 
both coats of mixed paints. Yellow pine appeared best with the first coat 
of lead and the second coat of lead and zinc mixed. 

Comparing the materials which were painted, we find that, generally, pop- 
lar retains the paint better than white pine; and would therefore, be pre- 
ferred for siding on buildings, etc. Yellow pine seems to be the worst of 
all for this purpose. Black iron as a whole retains the paint better than 
either tin or galvanized iron. 



MISCELLANEOUS TABLES. 



1499 



MISCELLANEOUS TABLES. 

WEIGHTS A!¥D MEASl T RES. 

Measure of Capacity. 

Gallon. — The standard gallon measures 231 cubic inches, and contains 

8.3388822 pounds avoirdupois = 58372.1757 grains Troy, of distilled water, at 
its maximum density 39.83° Fahrenheit, and 30 inches barometer height. 

Bushel. —The standard bushel measures 2150.42 cubic inches =77.627413 
pounds avoirdupois of distilled water at 39.83° Fahrenheit, barometer 30 
inches. Its dimensions are 18^ inches inside diameter, 19£ inches outside, 
and 8 inches deep ; and when heaped, the cone must not be less than 6 
inches high, equal 2747.70 cubic inches for a true cone. 

Pound. — The standard pound avoirdupois is the weight of 27.7015 cubic 
inches of distilled water, at 39.83° Fahrenheit, barometer 30 inches, and 
weighed in the air. 

Measure of JLengrth. 



Miles. 


Furlongs. 


Chains. 


Rods. 


Yards. 


Feet. 


Inches. 


1 


8 


80 


320 


1760 


5280 


63360 


0.125 


1 


10 


40 


220 


660 


7920 


0.0125 


0.1 


1 


4 


22 


66 


792 


0.003125 


0.025 


0.25 


1 


5.5 


16.5 


198 


0.00056818 


0.0045454 


0.045454 


0.181818 


1 


3 


36 


0.00018939 


0.00151515 


0.01515151 


0.0606060 


0.33333 


1 


12 


0.000015783 


0.000126262 


0.001262626 


0.00505050 


0.0277777 


0.083333 


X 







Measur 


e of Sui 


■face. 






Sq. Miles. 


Acres. 


S. Chains 


Sq. Rods. 


Sq. Yards 


Sq. Feet. 


Sq. Inches 


X 


640 


6400 


102400 


3097600 


27878400 


4014489600 


0-001562 


1 


10 


160 


4840 


43560 


6272640 


0.0001562 


0.1 


1 


16 


484 


4356 


627264 


0.000009764 


0.00625 


0.0625 


1 


30.25 


272.25 


39204 


0.000000323 


0.0002066 


0.002066 


0.0330 


1 


9 


1296 


0.0000000358 


0.00002296 


0.0002296 


0.00367 


0.1111111 


1 


144 


0.00000000025 


0.000000159 


0.00000159 


0.00002552 


0.0007716 


0.006944 


1 







measure 


of Capacity. 




Cub. Yard. 


Bushel. 


Cub. Feet. 


Pecks. 


Gallons. 


Cub. Inch. 


1 
0.03961 
0.037037 
0.009259 


21.6962 

1 
0.803564 
0.25 
0.107421 


27 
1.24445 

1 
0.31114 
0.133681 
0.000547 


100.987 
4 
3.21425 

X 
0.429684 
0.001860 


201.974 
9.30918 
7.4805 
2.32729 

X 
0.004329 


46656 

2150.42 

1728 

537.605 

231 

X 



1500 



MISCELLANEOUS TABLES. 





measure of Liquid* 






Gallon. 


Quarts. 


Pints. 


Gills. 


Cub. Inch. 


1 
0.25 
0.125 
0.03125 
0.004329 


4 
1 

0.5 

0.125 

0.17315 


8 

2 
1 
0.25 
0.03463 


32 

8 

4 

1 

0.13858 


231 
57.75 
28.875 
7.21875 

1 



Measures of Weig-hts. 

AVOIRDUPOIS. 



Ton. 


Cwt. 


Pounds. 


Ounces. 


Drams. 


1 


20 


2240 


35840 


573440 


0.05 


1 


112 


1792 


28672 


0.00044642 


0.0089285 


1 


16 


256 


0.00002790 


0.000558 


0.0625 


1 


16 


0.00000174 


0.0000348 


0.0016 


0.0625 


1 







TROY. 






Pounds. 


Ounces. 


Dwt. 


Grains. 


Pound Avoir 


1 
0.083333 
0.004166 
0.0001736 
1.215275 


12 

1 
0.05000 
0.002083333 
14.58333 


240 

20 
1 
0.0416666 
291.6666 


5760 

480 

24 

1 
7000 


0.822861 
0.068571 
0.0034285 
0.00014285 

1 



APOTHECARIES. 



Pounds. 


Ounces. 


Drams. 


Scruples. 


Grains. 


1 
0.08333 
0.01041666 
0.0034722 
0.00017361 


12 

1 

0.125 

0.0416666 

0.0020833 


96 
8 

1 
0.3333 
0.016666 


288 

24 

3 

1 

0.05 


5760 

480 

60 

20 

1 



Equivalent* of Lineal Iff easures — Iff etrical and English. 





Meters. 




English Measures. 


















Inches. 


Feet. 


Yards. 


Miles. 


Millimeter . . mm 
Centimeter . cm 
Decimeter . . . 

Meter 

Decameter . . 
Hectometer . . 
Kilometer . . . 


.001 
.01 

.1 
1. 

10. 

100. 

1,000. 

10,000. 


.039370 

.393701 

3.937011 

39.370113 


.003281 
.032809 
.328084 
3.280843 
32.80843 
328.0843 
3280.843 


.001094 
.010936 
.109361 
1.093614 
10.93614 
109.3614 
1093.614 


.000621 

.006214 

.062137 

.621372 

6 213718 













Micron = .000,001 meter 
zz .C01 millimeter 



MISCELLANEOUS TABLES. 



1501 



equivalents of I,iiieal Measures — Met. and Eng-. — Continued. 
English Measures. Meters. Reciprocals. 



1 inch 

12 inches = 1 foot 

3 feet = 1 yard 

5£ yards=16£ feet=l rod or pole 

4 poles = 66 feet = 22 yards = 1 chain (Gunter's) 
80 chains = 320 poles — 5280.ft.rr 1760 yds. = lmile 



.02539954 
.3047945 
.9143835 
5.029109 
20.11644 
1609.3149 



39.37079 
3.280899 
1.093633 
.1988424 
.0497106 
.00062138 



A Gunter's chain has 100 links. Each link — 7.92 inches =z 0.2017 meter. 
Equivalents of Superficial Measures — Metrical and Eng-. 

(METRICAL AND ENGLISH MEASURES.) 



Milliare . . . 
Centiarerrsq.met 
Deciare . . . 

Are 

Decare (not used) 
Hectare . . . 
Square kilometer 



Square 
meters. 



.1 
1. 

10. 
100. 

1000. 

10000. 

1000000. 



English Measures. 



Square 
inches. 



155.01 
1550.06 
15500.59 
155005.9 



Square 
feet. 



1.076 
10.764 
107.64 
1076.4 
10764.3 
107643. 



Square 
yards. 



.119 

1.196 

11.960 

119.6033 

1196.033 

11960.33 



Acres. 



2.4711431 
247.11431 



Square 
miles. 



.386126 



English Measures. 



Metrical Measures. Reciprocals. 



6.451367 sq. cent. 
.09289968 sq.mt. 
.8360972 " " 

25.29194 " " 



1 square inch 

144 square inches z=z 1 square foot . 

9 square feet =: 1 square yard . . 

30^ sq. yds. ) 1 perch = 1 square rod 

272£ sq. ft. j ~ or pole 

160perches = ) ^ 

10 sq. chains } ~ * acre • • • • 
640 acres == 1 square mile .... 



4046.711 

2589894.5 



.1550059 
10.7642996 
1.196033 

.0395383 

.00024711 
.00000038612 



Equivalents of Weigrhts 


— Metrical and English. 




Grammes 


English Weights. 




Oz. 

avoir. 


Lbs. 
avoir. 


Tons 
2000 lbs. 


Tons 
22401bs. 


Troy 
weight. 


Milligramme . 
Centigramme . 
Decigramme . 
Gramme . . . 
Decagramme . 
Hectogramme. 
Kilogramme . 
Myriagramme . 
Quintal . . . 
Millier or Tonne 


.001 
.01 
.1 
1. 

10. 

100. 

1000. 

10000. 

100000. 

1000000 


' .0353 

.3527 

3.5274 

35.2739 

352.7394 

3527.3943 


' .ooi2 

.02205 

.22046 

2.2046 

22.0462 

220.4261 

2204.6215 


.001102 

.011023 

.110231 

1.102311 


.000984 
.009842 
.098421 
.984206 


.015 Grs. 
.15 " 
1.543 " 
15.43235'* 

. . . . oz. 

32.150727" 
321.507266" 
3215.07266 " 
32150.72655" 


English Weights — "Avoirdupois." 


Grammes. 


Reciprocals. 


1 grain 




.06479895 
1.771836 
28.349375 
453.592652 
45359.265 
50802.376 
907.18524 
1016.04753 

.06479895 
1.555175 
31 msdOfi 


15.43234875 
564383 


24.34375 grains =z 1 dram 
16 drams — 1 ounce = 437.5 
16 ounces = 1 pound = 7000 
100 lbs. = 1 cwt. (American 
112 lbs. = 1 cwt. (English) . 
20 cwt. = 1 ton (Am.) in kil< 
20 cwt. = 1 ton (Eng.) in kil 
English Weights — " T: 
1 grain 






grains 
grains 
) . . . . 

38 . . . 


• • 


.0352739 

.00220462 

.000022046 

.00001968 

001102311 


OS . . . 




.000984206 


roy." 




15.43234875 
.6430146 


24 grains = 1 dwl 
20 dwt — 1 oz. 


\ 








12 oz. = 1 lb 


37 


3.241954 






.00267923 



1502 



MISCELLANEOUS TABLES. 



8 



i— i t» 
eg © 






OH 



«g 



8*5 

cScN 

On 



a 



•9® 



,o © 

51 






Nli5H(^HOJ 

.ONNOtHIN 
OO(Nt*l0rt 




<N <D ^ — t~ Oi _ 



*C<N l> 00 



>88 

CO 



(CriONI>0 



<S8 



§S^ 



-SSS8 



I : :a : 



'a 

• d 



sis -s« 

=o«®oo 



SSs 



* © * <D 



3 S a -^o^o 






«> « /v. £2 & £; 2? w ~ S 

ooOnmqhuso^ 
S3°oQo5'*n^c' 



.Q GO 
- ©£ 



^HC0lOO5C0rt<(MCC>e2f0 



O d pG*§ 
<*-i ^ eg eg c3 ri 
O ^ to e3 *r! ." 

© © >^S a 

•g ii-2 § as 

,Q ©•£ II co fcJD 



rd c 



5 * 

c3 3 



MISCELLANEOUS TABLES. 1503 

Metrical Measures Equivalent to English Measures. 



Meters. 


Inches. 


Feet. 


l m /m 


0.039 


0.0033 


2 


0.079 


0.0066 


3 


0.118 


0.0098 


4 


0.157 


0.0131 


5 


0.197 


0.0164 


6 


0.236 


0.0197 


7 


0.276 


0.0230 


8 


0.315 


0.0262 


9 


0.354 


0.0295 


10°>/ m = lc/ m 


0.394 


0.033 


2 


0.787 


0.066 


3 


1.181 


0.098 


4 


1.575 


0.13-1 


5 


1.969 


0.164 


6 


2.362 


0.197 


7 


2.756 


0.230 


8 


3.150 


0.262 


9 


3.543 


0.295 


10,/ m = .l m 


3.937 


0.328 


.2 


7.874 


0.656 


•3 


11.811 


0.984 


.4 


15.748 


1.312 


.5 


19.685 


1.640 


.6 


23.622 


1.969 


.7 


27.560 


2.297 


.8 


31.497 


2.625 


.9 


35.434 


2.953 


1*0 


39.370 


3.281 



Table for the Conversion of Mils. 
Centimeters. 



(l-lOOO Inches) into 





Centi- 




Centi- 




Centi- 




Centi- 


Mils. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


1 


.00254 


18 


.04571 


35 


.08888 


52 


.1321 


2 


.00508 


19 


:04825 


36 


.09142 


53 


.1346 


3 


.00762 


20 


.05079 


37 


.09396 


54 


.1372 


4 


.01016 


21 


.05333 


38 


.09650 


55 


.1397 


5 


.01270 


22 


.05587 


39 


.09904 


56 


.1422 


6 


.01524 


23 


.05841 


40 


.1016 


57 


.1448 


7 


.01778 


24 


.06095 


41 


.1041 


58 


.1473 


8 


.02032 


25 


.06348 


42 


.1067 


59 


.1499 


9 


.02286 


26 


.06602 


43 


.1092 


60 


.1524 


10 


.02540 


27 


.06856 


44 


.1118 


61 


.1549 


11 


.02793 


28 


.07110 


45 


.1143 


62 


.1575 


12 


.03047 


29 


.07364 


46 


.1168 


63 


.1600 


13 


.03301 


30 


.07618 


47 


.1194 


64 


.1626 


14 


.03555 


31 


.07872 


48 


•1219 


65 


.1651 


15 


.03809 


32 


.08126 


49 


.1245 


66 


.1676 


16 


.04063 


33 


.08380 


50 


.1270 


67 


.1702 


17 


.04317 


34 


.08634 


51 


.1295 


68 


.1727 



1504 MISCELLANEOUS TABLES. 

Table for the Conversion of Mils. — Continued. 





Centi- 




Centi- 




Centi- 




Centi- 


Mite. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


Mils. 


meters. 


69 


.1752 


77 


.1956 


85 


.2159 


93 


;2362 


70 


.1778 


78 


.1981 


86 


.2184 


94 


.2387 


71 


.1803 


79 


.2006 


87 


.2209 


95 


.2413 


72 


.1829 


80 


.2032 


88 


.2235 


96 


.2438 


73 


.1854 


81 


.2057 


89 


.2260 


97 


.2465 


74 


.1879 


82 


.2083 


90 


.2286 


98 


.2489 


75 


.1905 


83 


.2108 


91 


.2311 


99 


.2514 


76 


.1930 


84 


.2133 


92 


.2336 


100 


.2540 



Sng-lish Meaiurei Equivalent to Metrical Measures. 





CO 


CO 


w 




QQ 










<D 


u 










03 


a 


G 

i-4 




Id 

fa 




fa 


0) 


o 

M 


1 














& 


0.794 


1 


0.0254 


0.01 


.003 


10 


3.048 


A 


1.588 


2 


.0508 


0.02 


.006 


20 


6.096 


t 


2.381 


3 


.0762 


0.03 


.009 


30 


9.144 


3.175 


4 


.1016 


0.04 


.012 


40 


12.192 


£ 


3.969 


5 


.1270 


0.05 


.015 


50 


15.240 


J% 


4.762 


6 


.1524 


0.06 


.018 


60 


18.288 


f 


5.556 


7 


.1778 


0.07 


.021 


70 


21.336 


6.350 


8 


.2032 


0.08 


.024 


80 


24.384 


32 


7.144 


9 


.2286 


0.09 


.027 


90 


27.431 


TS 


7.937 


10 


.2540 


.1 


.030 


100 


30.479 


i 


8.731 


11 


.2794 


.2 


.061 


200 


60.959 


9.525 


12 


.3048 


.3 


.091 


300 


91.438 


M 


10.319 






.4 


.122 


400 


121.918 


35 


11.112 






.5 


.152 


500 


152.397 


11.906 






.6 


.183 


600 


182.877 


f 

T 
3) 

is 

¥ 

II 
U 

¥ 


12.700 
13.494 
14.287 
15.081 
15.875 
16.668 
17.462 
18.256 
19.050 
19.843 
20.637 
21.430 
22.224 






.7 


.213 


700 


213.356 






.8 
.9 

1.0 

2 

3 

4 

5 

6 

7 

8 

9 
10 


.244 

.274 

.305 

.610 

.914 

1.219 

1.524 

1.829 

2.134 

2.438 

2.743 

3.048 


800 
900 
1000 


243.836 
274.315 
304.794 


q 


23.018 














ii 


23.812 














H 


24.606 














l 


25.400 















MISCELLANEOUS TABLES. 



1505 



Conversion of Inches and Eigrhtns into Decimals of a 

Toot. 









Fractions of an Inch. 






Inches. 























i 


1 


1 


* 


f 


1 


i 





.0000 


.01041 


.02083 


.03125 


.04166 


.05208 


.0625 


.07291 


1 


.08333 


.09375 


.10416 


.11458 


.125 


.13541 


.14588 


.15639 


2 


.16666 


.17707 


.1875 


.19792 


.20832 


.21873 


.22914 


.23965 


3 


.25 


.26041 


.270 


.28125 


.29166 


.30208 


.3125 


.32291 


4 


.33333 


.34375 


.35416 


.364 


.375 


.38541 


.39588 


.40639 


5 


.41666 


.42707 


.437 


.44792 


.45832 


.46873 


.47914 


.48965 


6 


.5 


.51041 


.520 


.53125 


.54166 


.55208 


.5625 


.57291 


7 


.58333 


.59375 


.60416 


.614 


.625 


.63541 


.64588 


.65639 


8 


.66666 


.67707 


.685 


.69792 


.70832 


.71773 


.72914 


.73965 


9 


.75 


.76041 


.770 


.78125 


.79169 


.80208 


.8425 


.82291 


10 


.83333 


.84375 


.85416 


.864 


.875 


.88541 


.89588 


.90639 


11 


.91666 


.92707 


.937 


.94792 


.95832 


.96873 


.97914 


.98965 


12 


1 foot. 


foot. 


foot. 


foot. 


foot. 


foot. 


foot. 


foot. 



. in. = 0.005208 ft ; ^ in. = 0.00265 ft. ; 5 \ in. — 0.001375 ft. 
GREEK IET'I£R»I. 



A 


a 


Alpha. 


B 


/3 


Beta. 


r 


y 


Gamma. 


A 


8 


Delta. 


E 


€ 


Epsilon. 


Z 


< 


Zeta. 


H 


V 


Eta. 





e 


Theta. 


I 


t 


Iota. 


K 


K 


Kappa. 


A 


A 


Lambda. 


M 


M 


Mu. 



N 


V 


Nu. 


H 


£ 


Xi. 








Omicron 


n 


■n 


Pi. 


p 


P 


Rho. 


2 


<r s 


Sigma. 


T 


T 


Tau. 


Y 


V 


Upsilon. 
Phi. 


$ 


* 


X 


X 


Chi. 


* 


$ 


Psi. 


n 


a 


Omega. 



AWOVLAR VEIOCITY. 

The number of degrees per second through which a body revolves about a 
center. 

w=z2n n 
where 

n— revolutions per second 

w — angular velocity. 



FRICTION. 

The following laws of friction are only approximate, the first not being 
true where pressures are very great, and the third beyond a velocity of 150 
feet per minute. 

2. Friction varies directly as the pressure on the surfaces in contact. 

2. Friction is independent of the extent of the surface in contact. 

3. Friction is independent of the velocity, when the surfaces are in motion. 

4. Boiling friction varies directly as the pressure, and inversely as the diam- 

eter of the rolling bodies, where the cylinders and balls are of the same 
substances, and are pulled or pushed, as in a car or wagon. 
Where the road is propelled by a crank fixed on the axle, the law is 
reversed. 



1506 



MISCELLANEOUS TABLES. 



TEMPERATURE, or OTEHglTY OF HEAT. 

Standard Points — Fahrenheit. Centigrade. Reaumur, 

Boiling point of water under ) 

one atmosphere . . . . j 
Melting point of ice .... 
(Absolute zero ; known by ) 

theory only j 

9° Fahrenheit — 5° Centigrade = 4° Reaumur. 

Temp Fah. r= - Temp. Cent, -f 32° = - Temp. Reau. -}- 32° 

5 5 

Temp. Cent. = - (Temp. Fah. — 32°) = - Temp. R6au. 



212° 


100° 


80° 


32° 


0° 


0° 


,— 461°.2 


— 274° 


— 219°.2) 



4 4 ' 

= g (Temp. Fah. — 32°) = - Temp. Cent. 



Temp. Reau. 
Table of Comparison of Different Thermometers. 



Fah. 


R£au. 


Cent. 


Fah. 


R6au. 


Cent. 


Fah. 


Reau. 


Cent. 


212 


80.0 


100.0 


180 


65.7 


82.2 


148 


51.5 


64.4 


211 


79.5 


99.4 


179 


65.3 


81.6 


147 


51.1 


63.8 


210 


79.1 


98.8 


178 


64.8 


81.1 


146 


50.6 


63.3 


209 


78.6 


98.3 


177 


64.4 


80.5 


145 


50.2 


62.7 


208 


78.2 


97.7 


176 


64.0 


80.0 


144 


49.7 


62.2 


207 


77.7 


97.2 


175 


63.5 


79.4 


143 


49.3 


61.6 


206 


77.3 


96.6 


174 


63.1 


78.8 


142 


48.8 


61.1 


205 


76.8 


96.1 


173 


62.6 


78.3 


141 


48.4 


60.5 


204 


76.4 


95.5 


172 


62.2 


77.7 


140 


48.0 


60.0 


203 


76.0 


95.0 


171 


61.7 


77.2 


139 


47.5 


59.4 


202 


75.5 


94.4 


170 


61.3 


76.6 


138 


47.1 


58.8 


201 


75.1 


93.8 


169 


60.8 


76.1 


137 


46.6 


58.3 


200 


74.6 


93.3 


168 


60.4 


75.5 


136 


46.2 


57-7 


199 


74.2 


92.7 


167 


60.0 


75.0 


135 


45.7 


57.2 


198 


73.7 


92.2 


166 


59.5 


74.4 


134 


45.3 


56.6 


197 


73.3 


91.6 


165 


59.1 


73.8 


133 


44.8 


56.1 


196 


72.8 


91.1 


164 


58.6 


73.3 


132 


44.4 


55.5 


195 


72.4 


90.5 


163 


58.2 


72.7 


131 


44.0 


55.0 


194 


72.0 


90.0 


162 


57.7 


72.2 


130 


43.5 


54.4 


193 


71.5 


89.4 


161 


57.3 


71.6 


129 


43.1 


53.8 


192 


71.1 


88.8 


160 


56.8 


71.1 


128 


42.6 


53.3 


191 


70.6 


88.3 


159 


56.4 


70.5 


127 


42.2 


52.7 


190 


70.2 


87.7 


158 


56.0 


70.0 


126 


41.7 


52.2 


189 


69.7 


87.2 


157 


55.5 


69.4 


125 


41.3 


51.6 


188 


69.3 


86.6 


156 


55.1 


68.8 


124 


40.8 


51.1 


187 


68.8 


86.1 


155 


54.6 


68.3 


123 


40.4 


50.5 


186 


68.4 


85.5 


154 


54.2 


67.7 


122 


40.0 


50.0 


185 


68.0 


85.0 


153 


53.7 


67.2 


121 


39.5 


49.4 


184 


67.5 


84.4 


152 


53.3 


66.6 


120 


39.1 


48.8 


183 


67.1 


83.8 


151 


52.8 


66.1 


119 


38.6 


48.3 


182 


66.6 


83.3 


150 


52.4 


65.5 


118 


38.2 


47.7 


181 


66.2 


• 82.7 


149 


52.0 


65.0 


117 


37.7 


47.2 



MISCELLANEOUS TABLES. 1507 

Table of Comparison of Different Thermometers— Continued. 



Fah. 


Reau. 


Cent. 


Fah. 


R£au. 


Cent. 


Fah. 


Reau. 


Cent. 


116 


37.3 


46.6 


70 


16.8 


21.1 


24 


—3.5 


—4.4 


115 


36.8 


46.1 


69 


16.4 


20.5 


23 


—4.0 


—5.0 


114 


36.4 


45.5 


68 


16.0 


20.0 


22 


—4.4 


—5.5 


113 


36.0 


45.0 


67 


15.5 


19.4 


21 


—4.8 


—6.1 


112 


35.5 


44.4 


66 


15.1 


18.8 


20 


—5.3 


—6.6 


111 


35.1 


43.8 


65 


14.6 


18.3 


19 


—5.7 


—7.2 


110 


34.6 


43.3 


64 


14.2 


17.7 


18 


—6.2 


—7.7 


109 


34.2 


42.7 


63 


13.7 


17.2 


17 


—6.6 


—8.3 


108 


33.7 


42.2 


62 


13.3 


16.6 


16 


—7.1 


—8.8 


107 


33.3 


41.6 


61 


12.8 


16.1 


15 


—7.5 


—9.5 


106 


32.8 


41.1 


60 


12.4 


15.5 


14 


—8.0 


—10.0 


105 


32.4 


40.5 


59 


12.0 


15.0 


13 


—8.4 


—10.5 


104 


32.0 


40.0 


58 


11.5 


14.4 


12 


—8.8 


—11.1 


103 


31.5 


39.4 


57 


11.1 


13.8 


11 


—9.3 


—11.6 


102 


31.1 


38.8 


56 


10.6 


13.3 


10 


—9.7 


—12.2 


101 


30.6 


38.3 


55 


10.2 


12.7 


9 


—10.2 


—12.7 


100 


30.2 


37.7 


54 


9.7 


12.2 


8 


—10.6 


—13.3 


99 


29.7 


37.2 


53 


9.3 


11.6 


7 


—11.1 


—13.8 


98 


29.3 


36.6 


52 


8.8 


11.1 


6 


—11.5 


—14.4 


97 


28.8 


36.1 


51 


8.4 


10.5 


5 


—12.0 


—15.0 


96 


28.4 


35.5 


50 


8.0 


10.0 


4 


—12.4 


—15.5 


95 


28.0 


35.0 


49 


7.5 


9.4 


3 


—12.8 


—16.1 


94 


27.5 


34.4 


48 


7.1 


8.8 


2 


—13.3 


—16.6 


93 


27.1 


33.8 


47 


6.6 


8.3 


1 


—13.7 


—17.2 


92 


26.6 


33.3 


46 


6.2 


7.7 





—14.2 


—17.7 


91 


26.2 


32.7 


45 


5.7 


7.2 


—1 


—14.6 


—18.3 


90 


25.7 


32.2 


44 


5.3 


6.6 


—2 


—15.1 


—18.8 


89 


25.3 


31.6 


43 


4.8 


6.1 


—3 


—15.5 


—19.4 


88 


24.8 


31.1 


42 


4.4 


5.5 


—4 


—16.0 


—20.0 


87 


24.4 


30.5 


41 


4.0 


5.0 


—5 


—16.4 


—20.5 


86 


24.0 


30.0 


40 


3.5 


4.4 


—6 


— lfi.8 


—21.1 


85 


23.5 


29.4 


39 


3.1 


3.8 


—7 


—17.3 


—21.6 


84 


23.1 


28.8 


38 


2.6 


3.3 


—8 


—17.7 


—22.2 


83 


22.6 


28.3 


37 


2.2 


2.7 


—9 


—18.2 


—22.7 


82 


22.2 


27.7 


36 


1.7 


2.2 


—10 


—18.6 


—23.3 


81 


21.7 


27.2 


35 


1.3 


1.6 


—11 


—19.1 


—23.8 


80 


21.3 


26.6 


34 


0.8 


1.1 


—12 


—19.5 


—24.4 


79 


20.8 


26.1 


33 


0.4 


0.5 


—13 


—20.0 


—25.0 


78 


20.4 


25.5 


32 


0.0 


0.0 


—14 


—20.4 


^25.5 


77 


20.0 


25.0 


31 


—0.4 


—0.5 


—15 


—20.8 


—26.1 


► 76 


19.5 


24.4 


30 


—0.8 


—1.1 


—16 


—21.3 


—26.6 


75 


19.1 


23.8 


29 


—1.3 


—1.6 


—17 


—21.7 


—27.2 


74 


18.6 


23.3 


28 


—1.7 


—2.2 


—18 


—22.2 


—27.7 


73 


18.2 


22.7 


27 


—2.2 


—2.7 


—19 


—22.6 


—28.3 


72 


17.7 


22.2 


26 


—2.6 


—3.3 


—20 


—23.1 


—28.8 


71 


17.3 


21.6 


25 


—3.1 


—3.8 









Number of 


Degrees Cent. = 


= Number 


of Degree* Fah. 




Tenths of a Degree — Centigrade Scale. 


Degrees 




Cent. 
























.0 


.1 


.3 


.3 


.4 


.5 


.6 


.7 


.8 


.9 




Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 





0.00 


0.18 


0.36 


0.54 


0.72 


0.90 


1.08 


1.26 


1.44 


1.62 


1 


1.80 


1.98 


2.16 


2.34 


2.55 


2.70 


2.88 


3.06 


3.24 


3.42 


2 


3.60 


3.78 


3.96 


4.14 


4.32 


4.50 


4.68 


4.86 


5.04 


5.22 


3 


5.40 


5.58 


5.76 


5.94 


6.12 


6.30 


6.48 


6.66 


6.84 


7.02 



1508 



MISCELLANEOUS TABLK5. 



JVnmber 


of Degrees Cent. rs " 


lumber of Degrees 






Fall. — (Continued.) 




Tenths of a Degree — Centigrade Scale. 


Degrees 




Cent. 
























.0 


.1 


.3 


.3 


.4 


.5 


6 


• t 


.8 


.9 




Fan. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


Fah. 


4 


7.20 


7.38 


7.56 


7.74 


7.92 


8.10 


8.28 


8.46 


8.64 


8.82 


5 


9.00 


9.18 


9.36 


9.54 


9.72 


9.90 


10.08 


10.26 


10.44 


10.62 


6 


10.80 


10.98 


11.16 


11.34 


11.52 


11.70 


11.88 


12.06 


12.24 


12.42 


7 


12.60 


12.78 


12.96 


13.14 


13.32 


13.50 


13.68 


13.86 


14.04 


14.22 


8 


14.40 


14.58 


14.76 


14.94 


15.12 


15.30 


15.48 


15.66 


15.84 


16.02 


9 


16.20 


16.38 


16.56 


16.74 


16.92 


17.10 


17.28 


17.46 


17.64 


17.82 



lumber of Degrees Fah. = dumber of Degrees Cent. 







Tenths of a Degree - 


- Fahrenheit Scale 






Degrees 
Fah. 


































.0 


.1 


.2 


.3 


.4 


.5 


.6 


.7 


.8 


.9 




Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 


Cent. 





0.00 


0.06 


0.11 


0.17 


0.22 


0.28 


0.33 


0.39 


0.44 


0.50 


1 


0.56 


0.61 


0.67 


0.72 


0.78 


0.83 


0.89 


0.94 


1.00 


1.06 


2 


1.11 


1.17 


1.22 


1.28 


1.33 


1.39* 


1.44 


1.50 


1.56 


1.61 


3 


1.67 


1.72 


1.78 


1.83 


1.89 


1.94 


2.00 


2.06 


2.11 


2.17 


4 


2.22 


2.28 


2.33 


2.39 


2.44 


2.50 


2.56 


2.61 


2.67 


2.72 


5 


2.78 


2.83 


2.89 


2.94 


3.00 


3.06 


3.11 


3.17 


3.22 


3.28 


6 


3.33 


3.39 


3.44 


3.50 


3.56 


3.61 


3.67 


3.72 


3.78 


3.83 


7 


3.89 


3.94 


4.00 


4.06 


4.11 


4.17 


4.22 


4.28 


4.33 


4.39 


8 


4.44 


4.50 


4.56 


4.61 


4.67 


4.72 


4.78 


4.83 


4.89 


4.94 


9 


5.00 


5.06 


5.11 


5.17 


5.22 


5.28 


5.33 


5.39 


5.44 


5.50 



Coefficients of Expansion at Ordinary Temperatures. 

(Solids.) 





Material. 




Coefficient of Expansion ^ 




°F. 


°c. 




.0000114 

.0000104 

.00000306 

.0000100 

.0000055 

.0000078 

.00000961 

.00000399 

.00000521 

.00000841 

.0000046 

.00000587 

.00000677 


.0000206 




.0000187 


Brick 


.00000551 


Bronze .... 


.0000180 


Cement and ) 




from 


.000010 


Concrete j 
Copper .... 

Glass 

Gold 




* ' to 

from 

* ' to 


.000014 

.0000173 

.00000719 

.00000938 

.0000151 




.0000083 




.0000106 


Iron, wrought 


.0000122 



MISCELLANEOUS TABLES. 



1509 



Coefficients of Expansion — (Continued.) 



Material. 




Coefficient of Expansion. 


°F. 


°c. 


Lead 


.0000158 

.000004 

.0000026 

.0000049 

.00000494 

.0000020 

.0000040 

.0000067 

.0000108 

.0000056 

.00000611 

.00000689 

.0000116 

.00000276 

.0000163 


0000284 


Marble (average) 

Masonry 

Platinum 


from 
* ' to 


.000007 
.0090047 
.00D0088 
.00000890 


Porcelain 

Sandstone 

Silver 


from 
' ' to 


.0000036 
.0000070 
.000012 
.0000194 


Slate 


.0000102 


Steel, untempered 

Steel, tempered 

Tin 


.0000110 
.0000124 
.0000209 




.00000496 


Zinc 


.0000293 







HEAT. 

Specific Heat of Substances. 

The specific heat of a body at any temperature is the ratio of the quantity 
of heat required to raise the temperature of the body one degree to the 
quantity of heat required to raise an equal mass of water at or near to its 
temperature of maximum density (4°C. or 39.2°F.) through one degree. 

Specific Heats of Metals. 

(Tomlinson.) 



Metal. 


Specific Heat at 




0°C. or 32°F. 


50°C.orl22°F. 


100°Cor212°F 


Aluminum 


0.2070 
0.0901 
0.0941 
0.1060 
0.0300 
0.0320 
0.0473 
0.0547 
0.0523 
0.0901 


0.2185 
0.0923 
0.0947 
0.1130 
0.0315 
0.0326 
0.0487 
0.0569 
0.0568 
0.0938 


0.2300 


Copper 

German Silver 

Iron 

Lead 

Platinum 

Platinum Silver 

Silver 


0.0966 
0.0952 
0.1200 
0.0331 
0.0333 
0.0501 
0.0591 


Tin 


0.0595 


Zinc 


0.0976 



Mean Specific Heat of Platinum 

(Pouillet.) 

Between 0°C. (32°F.) and 100°C. (212°F.) 
44 300°C. (572°F.) 
" 500°C. (932°F.) 
" 700°C. (1292°F.) , 
" 1000°C. (1832°F.) 
" 1200°C. (2192°F.) , 



0.0335 
0.0343 
0.0352 
0.0360 
0.0373 
0.038* 



1510 



MISCELLANEOUS TABLES. 



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MISCELLANEOUS TABLES. 



1511 



Mean Specific Heat of Water, 

(Regnault.) 

Between 0°C. (32°F.) and 40°C. (104°F.) . ••..'. 1.0013 

" « " M 80°C. (176°F.) 1.0035 

M " " " 120°C. (248°F.) 1.0067 

" " " " 160°C. (320°F.) 1.0109 

" " M " 200°C. (392°F.) .... a 1.0160 

" " ■• " 230°C. (446°F.) 1.0204 

Mean Specific Heat of Glass (Kohlrausch) 0.19 

Specific Heat of Oases and Vapors at Constant .Pressure, 



Substance. 



Specific Heat for 
Equal. 



Volumes. Weights. 



Observer. 



Air 

Carbon monoxide 
Carbon dioxide . 
Hydrogen . . . 
Nitrogen . . . . 
Oxygen . . . . 
Steam . . . . , 



0.2375 


0.2375 


Regnault 


0.2370 


0.2450 


Regnault 


0.2985 


0.1952 


Wiedermann 


0.2359 


3.4090 


Regnault 


0.2368 


0.2438 


Regnault 


0.2405 


0.2175 


Regnault 


0.2989 


0.4805 


Regnault 



Total Heat of Steam. 

British Thermal Unit : (B. T. U.) is the quantity of heat which 
will raise the temperature of one pound of water one degree Fah. at or near 
its temperature of maximum density 39.1°. 

French Calorie : is the quantity of heat that will raise the tempera- 
ture of one kilogramme of pure water 1°C. at or near4°C. 

Pound Calorie : is the quantity of heat that will raise the tempera- 
ture of one pound of water 1°C. 

1 B. T. U. = .252 Calories. 
1 Calorie r= 3.968 B. T. U. 
1 lb. Calorie =1.8B. T. U. 
1 pound Calorie = 0.4536 Calorie. 



The Mechanical Equivalent of Heat. 



Joule gives 
Professor Rowland, 



1 B. T. TJ. = 772 ft. lbs. 
1 B. T. U. == 778 ft. lbs. 

1 ft. lb. = =J- = .001285 B. T. U, per minute. 



' 778 
1 H. P. = 42.416 B.T.U. 

i^ee Table of Energy Equivalents on p 1258.) 



1512 



MISCELLANEOUS TABLES. 



Specific diiavitv. 



Names of Sub- 
stances. 


co b£ 


-2 . s 

© QfG 


Names of Substances. 


GO bC 


© © a 


Woods. 












Cedar, Indian 


1.315 


.0476 


Oil, Linseed . . , . . . 


.940 


.0340 


" American 


.561 


.0203 


" Olive ,.oo..= 


.915 


.0331 


Citron .... 


.726 


.0263 


44 Turpentine . . . . 


.870 


.0314 


Cocoa-wood . . 


1.040 


.0376 


" Whale . . 




.932 


.0337 


Cherry-tree . . 


.715 


.0259 


Proof Spirit . . 


. 


.925 


.0334 


Cork 


.240 


.0087 


Vinegar . . . 


. 


1.080 


.0390 


Cypress, Spanish 
Ebony, American 


.644 


.0233 


Water, distilled 




1.000 


.0361 


1.331 


.0481 


" sea . . 




1.030 


.0371 


" Indian . 


1.209 


.0437 


'• Dead Sea 


. 


1.240 


.0448 


Elder-tree . . . 


.695 


.0252 


Wine. .... 




.992 


.0359 


Elm, trunk of 


.671 


.0243 


" Port . ■ 




.997 


.0361 


Filbert-tree . . 


.600 


.0217 








Fir, male . . . 


.550 


.0199 


Miscellaneous. 






" female . . 


.498 


.0180 


Ebonite ....... 


1.8 




Hazel .... 


.600 


.0217 


Pitch , . . 


1.6 




Jasmine, Spanish 


.770 
.556 


.0279 
.02.01 


Asphaltum | 


.905 
1.650 


.0327 


Juniper-tree . . 




.0597 


Lemon-tree . . 


.703 


.0254 


Beeswax . . . . . . . 


.965 


.0349 


Lignum-vitse . . 


1.333 


.0482 


Butter , . 


.942 


.0341 


Linden-tree . . 


.604 


.0219 


Camphor 


.988 


.0357 


Logwood . . . 


.913 


.0331 


India rubber 


.933 


.0338 


Mastic-tree . . 


.849 


.0307 


Fat of Beef ...... 


.923 


.0334 


Mahogany . . . 


1.063 


.0385 


" Hogs . . . . . . 


.936 


.0338 


Maple .... 
Medlar .... 


.750 


.0271 


44 Mutton 


.923 


.0334 


.944 


.0342 


Gamboge . . . . . . . 


1.222 


.0442 


Mulberry . . . 


.897 


.0324 


Gunpowder, loose .... 


.900 


.0325 


Oak, heart of, 60 old 


1.170 


.0423 


44 shaken . , . 


1.000 


.0361 


Orange-tree . . 


.705 


.0255 


" solid ... | 


1.550 


.0561 


Pear-tree . . . 


.661 


.0239 


1.800 


.0650 


Pomegranate-tree 


1.354 


.0490 


Gum Arabic 


1.452 


.0525 


Poplar .... 


.383 


.0138 


Indigo 


1.009 


.0365 


" white Spanish 


.529 


.0191 


Lard ......... 


.947 


.0343 


Plum-tree . . . 


.785 


.0284 


Mastic ........ 


1.074 


.0388 


Quince-tree . . 


.705 


.0255 


Spermaceti . . . . • . 


.943 


.0341 


Sassafras . . . 


.482 


.0174 


Sugar ........ 


1.605 


.0580 


Spruce .... 


.500 


.0181 


Tallow, sheep .... 


.924 


.0334 


old . . . 


.460 


.0166 


44 calf . . o . . . 


.934 


.0338 


Pine, yellow . . 


.660 


.0239 


44 ox .... o . 


.923 


.0334 


44 white . . 


.554 


.0200 


Atmospheric air . . . . 


.0012 


.000043 


Vine . . o . . 


1.327 


.0480 






W'g't 


Walnut .... 


.671 


.0243 


Oases. Vapors. 




cu.ft. 


Yew, Dutch . . 


.788 


.0285 






gr'ns. 


" Spanish 


.807 


.0292 


Atmospheric air . . . . 


1.000 


527.0 


1, i quids. 






Ammoniacal gas .... 


.500 


263.7 


Acid, Acetic . . 


1.062 


.0384 


Carbonic acid , . - . . 


1.527 


805.3 


" Nitric . . 


1.217 


.0440 


Carbonic oxid ..... 


.972 


512.7 


" Sulphuric . 


1.841 


.0666 


Carbureted hydrogen . . 


.1)72 


5i2.7 


" Muriatic . 


1.200 
1.500 


.0434 
.0542 


Chlorine . . . . . 


2.500 


1316 


" Fluoric . . 


Chlorocarbonous acid . . 


3.472 


1828 


11 Phosphoric 


1.558 


.0563 


Chloroprussic acid . . . 


2.152 


1134 


Alcohol, commer. 


.833 


.0301 


Fluoboric acid . . . 1 ' . 


2 371 


1250 


" pure 


.792 


.0287 


Hydriodic acid ..*... 


4.346 


2290 


Ammoniac, liquid 


.897 


.0324 


Hydrogen ....... 


.069 


36.33 


Beer, lager . . . 
Champagne . . 


1.034 
.997 


.0374 
.0360 


Oxvffftn . ...... 


1.104 


581.8 


Sulphuretted hydrogen . 


1.777 


9370 


Cider 


1.018 


.0361 


Nitrogen • . 


.972 


512.0 


Ether, sulphuric 


.739 


.0267 


Vapor of alcohol .... 


1.613 


851.0 


Naptha .... 


.848 




44 turpentine spirits 


5.013 


2642 


Egg 


1.090 


.0394 


44 water .... 


.623 


328.0 


Honey .... 


1-450 


.0524 


Smoke of bituminous coal 


.102 


53.80 


Human blood 


1.054 


.0381 


44 wood ..... 


.90 


474.0 


Milk 


1.032 


.0373 


Steam at 212° . . . . . 


.488 


257.3 



MISCELLANEOUS TABLES. 



1513 



T4 BI>E OJP SPECIFIC OHJLVITY 4 "¥« C»IX 

Water at 39.1° Fahrenheit = 4° Centigrade ; 62.425 pounds to the cubic foot 
(authority, Kent, Haswell, and D. K. Clark). 





Specific 
Gravity. 




Lbs. per 


Lbs. per 


Kilos per 




Authority. 


Cubic 


Cubic 


Cubic 






Foot. 


Inch. 


Deem. 


Aluminum, pure cast 


2.56 


P. R. C. 


159.63 


.0924 


2.56 


" " rolled 


2.68 


** 


167.11 


.0967 


2.68 


" " anne'ld 


2.66 


" 


165.86 


.0960 


2.66 


" nickel alloy, cast 


2.85 


" 


178.10 


.1031 


2.85 


M " m rolled 


2.76 


" 


172.10 


.0996 


2.76 


ff " " ann'ld 


2.74 


44 


170.85 


.0989 


2.74 


Aluminum Bronze, 10% 


7.70 


Riche. 


480.13 


.2779 


7.70 


5% 


8.26 


" 


515.63 


.2984 


8.26 


Brass, cu. 67, zn. 33 cast 


8.32 


Haswell. 


519.36 


.3006 


8.32 


11 cu. 60, zn. 40 " 


8.405 


Thurston. 


524.68 


.3036 


8.405 


Cobalt 


8.50 


R.-A. 


530.61 


.3071 


8.50 


Brass, plates . . . 










.... 


high yellow . 


° 8.586 


P.R.C*. 


535.38 


.'3698' 


8.586 


Bronze composition . 












cu. 90, tin 10 . 


' 8.669 


Thurston. 


541.17 


.3132' 


3 8.669 


Bronze composition . 






. , . 






cu. 84, tin 16 . 


' 8.832 


Haswell. 


551.34 


.3191 ' 


8.832 


Lithium . • • • . 


0.57 


R.-A. 


36.83 


.0213 


.57 


Potassium .... 


0.87 


" 


54.31 


.0314 


.87 


Sodium . . . . . 


0.97 


<( 


60.55 


.0350 


.97 


Rubidium .... 


1.52 


11 


94.89 


.0549 


1.52 


Calcium 


1.57 


u 


98.01 


.0567 


1.57 


Magnesium . . . . 


1.74 


<( 


108.62 


.0629 


1.74 


Caesium . . . . , 


1.88 


ii 


117.36 


.0679 


1.88 


Boron ...... 


2.00 


Haswell. 


124.85 


.0723 


2.00 


Glucinum . « • • 


2.07 


R.-A. 


129.22 


.0748 


2.07 


Strontium .... 


2.54 


" 


158.56 


.0918 


2.54 


Barium ..... 


3.75 


<( 


234.09 


.1355 


3.75 


Zirconium .... 


4.15 


ii 


259.06 


.1499 


4.15 


Selenium . ■ . . « 


4.50 


Haswell. 


280.91 


.1626 


4.50 


Titanium . . . . . 


5.30 


ii 


330.85 


.1915 


5.30 


Vanadium . . . . 


5.50 


R.-A. 


343.34 


.1987 


5.50 


Arsenic . . . . . 


5.67 


h 


353.95 


.2048 


5.67 


Columbium .... 


6.00 


Haswell. 


374.55 


.2168 


6.00 


Lanthanum . . . » 


6.20 


" 


387.03 


.2240 


6.20 


Niobium . • * « ■ 


6.27 


R.-A. 


391.40 


.2265 


6.27 


Didymium .... 


6.54 


" 


408.26 


.2363 


6.54 


Cerium ..... 


6.68 


ii 


417.00 


.2413 


6.68 


Antimony .... 
Chromium .... 


6.71 
6.80 


ii 


418.86 
429.49 


.2424 
.2457 


6.71 
6.80 


Zinc, cast . . . > . 


6.861 


Haswell. 


428.30 


.2479 


6.861 


11 pure ... o 
" rolled .... 


7.15 


R.-A. 


446.43 


.2583 


7.15 


7.191 


Haswell. 


448.90 


.2598 


7.191 


Wolfram . . . <> . 


7.119 


ii 


444.40 


.2572 


7.119 


Tin, pure 

Indium ..... 


7.29 


R.-A. 


455.08 


.2634 


7.29 


7.42 


ii 


463.19 


.2681 


7.42 


Iron, cast .... 


7.218 


Kent. 


450.08 


.2605 


7.218 


" wrought . . . 
" wire ... o 


7.70 


ii 


480.13 


.2779 


7.70 


7.774 


Haswell. 


485.29 


.2808 


7.774 


Steel, Bessemer . . 


7.852 


" 


479.00 


.2837 


7.852 


" soft . . . . 


7.854 


Kent. 


489.74 


.2834 


7.854 


Iron, pure .... 


7.86 


R.-A. 


490.66 


.2840 


7.86 



1514 



MISCELLANEOUS TABLES. 



TABLE OF SPECIFIC GRAVITY. — Continued. 





Specific 
Gravity. 


Authority. 


Lbs. per 
Cubic 
Foot. 


Lbs. per 
Cubic 
Inch. 


Kilos per 
Cubic 
Deem. 


Manganese .... 


8.00 


R.-A. 


499.40 


.2890 


8.00 


Cinnabar 


8.809 


Haswell. 


505.52 


.2925 


8.098 


Cadmium ..... 


8.60 


R.-A. 


536.85 


.3107 


8.60 


Molybdenum . . . 


8.60 


(< 


536.85 


.3107 


8.60 


Gun Bronze .... 


8.750 


Haswell. 


546.22 


.3161 


8.750 


Tobin Bronze . . . 


8.379 


A. C. Co. 


523.06 


.3021 


8.379 


Nickel 


8.80 


R.-A. 


549.34 


.3179 


8.80 


Copper, pure . . . 
Copperplates and sheet 


8.82 


" 


550.59 


.3186 


8.82 


8.93 


A. of C. M. 


556.83 


.3222 


8.93 


Bismuth 


9.80 


R.-A. 


611.76 


.3540 


9.80 


Silver 


10.53 


" 


657.33 


,3805 


10.53 


Tantalum .... 


10.80 


" 


674.19 


.3902 


10.80 


Thorium 


11.10 


« 


692.93 


.4010 


11.10 


Lead 


11.37 


« 


709.77 


.4108 


11.37 


Palladium .... 


11.50 


« 


717."88 


.4154 


11.50 


Thalium 


11.85 


" 


739.73 


.4281 


11.85 


Rhodium 


12.10 


" 


755.34 


.4371 


12.10 


Kuthenium . . . „ 


12.26 


" 


765.33 


.4429 


12.26 


Mercury 


13.59 


" 


848.35 


.4909 


13.59 


Uranium 


18.70 


M 


1167.45 


.6755 


18.70 


Tungsten 


19.10 


M 


1192.31 


.6900 


19.10 


Gold 


19.32 


*' 


1206.05 


.6979 


19.32 


Platinum 


21.50 


(< 


1342.13 


.7767 


21.50 


Iridium 


22.42 


(< 


1399.57 


.8099 


22.42 


Osmium . . . „ . 


22.48 


11 


1403.31 


.8121 


22.48 



Authorities — R.-A. — Professor Roberts-Austen. 

Haswell— Haswell's Engineer's Pocket Book. 

P. R. C — Pittsburg Reduction Co.'s tests. 

Kent — Kent's Mechanical Engineer's Pocket Book. 

Thurston — Report of Committee on Metallic Alloys of U. S. 

Board appointed to test iron, steel, and other metals. 

Thurston's Materials of Engineering. 
Riche — Quoted by Thurston. 
A. C. Co. — Ansonia Brass and Copper Co. 
A. of C. M. —Association of Copper Manufacturers. 

SPECIFIC GRAVITY AT ©2° FAHRENHEIT OF 
ALUMINIM l\l) AIVIHOVM AEJLOYS. 

Aluminum Commercially Pure, Cast . ... ........ * 2.56 

Nickel Aluminum Alloy Ingots for rolling . , . . 2.72 

Casting Alloy 2.85 

Special Casting Alloy, Cast 3.00 

Aluminum Commercially Pure, as rolled, sheets and wire . , . , . 2.68 

" " " Annealed 2.66 

Nickel Aluminum Alloy, as rolled, sheets and wire ........ 2.76 

" " " Sheets Annealed 2.74 

Weiglit. 

Using these specific gravities, assuming water at 62 degrees Fahrenheit, 
and at Standard Barometric Height, as 62.355 lbs. per cubic foot (authority, 
Kent and D. K. Clark). ,. mn •„ 

Sheet of cast aluminum, 12 inches square and 1 inch thick, weighs 13.3024 lbs. 
Sheet of rolled aluminum, 12 inches square and 1 inch thick,weighs 13.9259 lbs. 
Bar of cast aluminum, 1 inch square and 12 inches long, weighs 1.1085 lbs. 
Bar of rolled aluminum, 1 inch square and 12 inches long, weighs 1.1605 lbs. 
Bar of aluminum, cast, 1 inch round and 12 inches long, weighs .8706 lbs, 
Bar of rolled aluminum, 1 inch round and 12 inches long, weighs .9114 lbs. 



POWER REQUIRED TO DRIVE MACHINERY 

SHOPS, AND TO DO VARIOUS KINDS 

OP WORK. 



PROXY BIUHE 

d 




4 



Constant = ~^- = .0001904. 



Fig. 1. 



Then 
Horse-power = .0001904 X d x to X revolutions per minute. 

Horse-Power formula*. 

In an article by C. H. Benjamin in March, 1899, Machinery are the follow- 
ing formulas for computing the horse-power required to operate tools, where 
W — weight metal removed per hour. 

Experiments with several lathes give: 

H.P. = .035 W for cast iron. 

H.P. = .067 W for machinery steel. 

Experiments with a Gray planer give: 

H.P. = .032 W for cast iron. 

Experiments with a Hendey shaper give 

H.P. = .030 W for cast iron. 

For milling machines we have: 

H.P. = .14 W. for cast iron. 

H.P. » .10 W for bronze. 

H.P. = .30 W for tool steel. 

In each case, the power required to run the tool, light, should be added. 

Power Used by Machine-Tool*. 

(R. E. Dinsmore, from the Electrical World.) 

1. Shop shafting 2 T 3 B - in. x 180 ft. at 160 revs., carrying 26 pulleys 

from 6 in. diam. to 36 in., and running 20 idle machine belts . 1.32 H. F 

2. Lodge-Davis upright back-geared drill-press with table, 28 in. 
swing, drilling f in. hole in cast iron, with a feed of 1 in. per 

minute 0.78 H. P. 

3. Morse twist-drill grinder No. 2, carrying 26 in. wheels at 3200 

revs ' 0.29 H. P. 

4. Pease planer 30 in. x 36 in., table 6 ft., planing cast iron, cut 

\ in. deep, planing 6 sq. in. per minute, at 9 reversals .... 1.06 H. P. 

5. Shaping-machine 22 in. stroke, cutting steel die, 6 in. stroke, y 

in. deep, shaping at rate of 1.7 square inch per minute . . . 0.37 H. P. 

6. Engine-lathe 17 in. swing, turning steel shaft 2| in. diam., cut 

T \ deep, feeding 7.92 in. per minute 0.43 H. P. 

7. Engine lathe 21 in. swing, boring cast-iron hole 5 in. diam., cut 

r 3 5 diam., feeding 0.3 in. per minute 0.23 H. P. 

8. Sturtevant No. 2, monogram blower at 1800 revs, per minute, 

no piping 0.8 H. P. 

9. Heavy planer 28 in. X 28 in. x 14 ft. bed, stroke 8 in., cutting 

steel, 22 reversals per minute 3.2 H. P 

1616 



1516 POWER REQUIRED TO DRIVE MACHINERY, ETC. 



Power Required for Machine Tools — Results of Tests. 
Tests of Various Machine Tools. 

(From a paper read by F. B. Duncan before the Engineers' Society of 
Western Pennsylvania.) 

Engine Lathes. 

16 in.; motor power required, approximate, 2 H.P. at maximum. 
18 in. X 6 ft.; motor power required, 2.1 H.P. 
36 in. X 10 ft.; motor power required, 10 H.P. 

Planebs. 

10 X 10 X 20 ft. ; 3 tools, f X & in. cut; cutting speed, 18 ft.; planing 
40-ton iron casting. H.P. required for cut, 26.5; for return, 23.6; for re- 
verse, 42.9. Ratio return, 3 to 1. Motor, 30 H.P., belted to countershaft. 

8 X 8 X 20 ft.; 3 tools, f X £ in. cut; cutting speed, 18 ft.; planing 32-ton 
iron casting; H.P. for cut, 16; for return, 14-8; for reverse, 28.2. Ratio 
return, 3 to 1. Motor, 25 H.P., belted to countershaft. 

66 X 60 in. X 12 ft.; 2 tools \ X 1-16 in. cut; cutting speed, 21 ft.; plan- 
ing 4 ton open hearth casting. H.P. required for cut, 10; for return, 14; for 
reverse, 16. Ratio return, 3^ to 1. Motor mounted on planer housing with 
42-inch 1,500-pound flywheel, running at 400 revolutions, mounted on 
motor shaft; flywheel used as driving pulley for return of platen. 

28 X 52 in. X 6 ft.; 1 cutting tool, f X i in. cut; cutting speed, 22 ft.; 
planing 3-ton iron casting. H.P. required for cut, 3.1; for return, 3.8; for 
reverse, 4.4. Ratio return, 4 to 1. Motor, 3 H.P., 800 revolutions. Aver- 
age load on motor, 2.48. Flywheel, 30 in. diameter, 496 pounds, 800 revo- 
lutions, mounted on motor shaft and used as pulley for return of platen. 

Miscellaneous. 

28 in. Gisholt turret lathe: machining Tropenas cast steel weight, 400 
pound; size cut, one tool, f X 5-16 in.; 4 tools, £X 5-64 in.; weight casting. 
400 pounds; power for cut, 3.9 H.P 

21 in. drill press; power required, 1 H.P. 

5 ft. radial drill; maximum power required, 2.03 H.P. Motor used, 2 H.P. 
600 revolutions. 

Double and emery wheel stand ;two 18 X 2 in. wheels, 950 rev.; 2 laborers 
grinding castings; maximum H.P., momentarily, 6; average, 3.5. Motor, 
5 H.P., mounted on grinder shaft. 

10 ft. boring and turning mill; cutting tools, 2; cut, f X 1-16 in.; cutting 
speed, 20 ft.; machining 3.5-ton casting; H.P. required for cut, 8.6. Motor 
used, 12 H.P. 

Slotter; cut, | X 1-16 in.; speed of tool, 20 ft.; machining open hearth 
steel castings; power requirea, 6.98 H.P. 

Flat turret lathe; \\ H.P. motor required. 

Gisholt tool grinder; speed, 1,600 to 1,800 rev.; power required, 7 for 
short periods, 4 on average. Motor used, 5 H.P. 

The figures given in the following table for the power required to run 
the planing machines empty, do not include the maximum horse-power at 
the instant of reversal, but represent the average forward and return of the 
empty table. 



POWER REQUIRED FOR MACHINE TOOLS. 



1517 



Results of tests at the Baldwin Locomotive Works, Philadelphia : 





Size. 


Material 
Cut. 


73 

"o 

O 

H 

*o 

d 


Horse-Power. 


Kind of 
Machines. 


T3 

d 

o «j 

OGQ 




Total Cutting. 




Min. 


Max. 


Ave. 


Wheel lathe 


84 in. 

84 in. 

84 in. 

78 in. 

78 in. 
36 in. X 12 in. 
62 in. X 35 ft. 
62 in. X 35 ft. 
36 in. X 12 ft. 
24 in. X 13 ft. 
36 in. X 18 ft. 
56 in. X 35 ft. 
56 in. X 24 ft. 

90 in. 

42 in. 

4 ft. 6 in. 

5 ft. 6 in. 
40 in. X15 in. 

19 in. str. 


Cast iron 

Cast iron 

Cast iron 

Cast iron 

Cast iron 

Wrought iron 

Wrought iron 

Wrought iron 

Wrought iron 

Steel 

Wrought iron 

Wrought iron 

Wrought iron 

Cast steel 

Cast steel 

Cast steel 

Cast iron 

Wrought iron 

Wrought iron 


2 
2 
2 

1 
1 
1 
2 
2 
2 
2 
2 
2 
2 
2 
1 
1 
1 
1 
1 






2.9 

4.2 

5.3 

4.3 

5.5 

4.4 

20.6 

23.0 

11.3 


7.9 

5.8 

6.2 

4.7 

7.1 

6.7 

21.6 

26.0 

13.8 


6.1 


Wheel lathe . 






5.1 


Wheel lathe . 
Boring mill . 




1.5 


5.8 
4.5 


Boring mill . 






6.5 


Slotter . . . 
Planer . . . 
Planer . . . 
Planer . . . 
Planer . . . 


1.5 
i.4 

2.7' 

1.95 

3.2 

4.6 

4.56 

1.43 

0.96 

2.1 

1.6 

1.8 

1.3 


1.5 
11.4 
5.8 
3.0 
4.3 
4.3 
9.9 
6.0 
2.1 
1.1 
2.4 
2.4 
2.2 
1.8 


5.3 
21.1 
24.5 
12.5 

8 


Planer . . . 






16 7 


Planer . . . 
Planer . . . 
Wheel lathe 


13.0 
16.0 


13.7 
17.7 


13.3 
16.8 
6 38 


Radial drill . 






2.1 


Boring mill . 






4 6 


Boring mill . 
Slotter . . . 


4.2 


4.8 


4.4 
7 3 


Shaper . . . 


4.8 


9.7 


7.3 



Results of tests, in ten different plants by C. H. Benjamin, to determine 
the proportion of power absorbed by the counters, belting, line shaft, etc. 















Useful 






Friction Horse-Power. 




Horse- 














Power. 


Nature of Work. 


<£ p 


8 ** 










6 






8^ 


8*3 


© 3.5 

rHQQ ^ 


Per 

Bear- 
ing. 


Per 

Coun- 
ter. 


Per 
Belt. 


i 


Per 
Man. 




Pn o 


Pm o 










& 
fc 




Boiler shop 


4.77 


.205 


.04 


.550 


.538 


.477 


.310 


.877 


Bridge work . . 






3.28 


.137 


.04 


.337 


.606 


.521 


.164 


.142 


Heavy machinery. 






5.70 


.233 


.038 


.581 


.665 


.453 


.707 


.160 


Heavy machinery. 






8.55 


.306 


.06 


.799 


.600 


.475 


.627 


.342 


Average . . . 






5.57 


.220 


.044 


.567 


.602 


.481 


.452 


.380 


Light machinery 






2.75 


.276 


.034 


.204 


.155 


.095 


.790 


.099 


Small tools . . 






8.00 


.400 


.09 


.689 


.127 


.119 


.109 


.152 


Small tools . . 






2.49 


.233 


.03 


.240 


.121 


.113 


.881 


.227 


Sewing machines 






4.36 


.430 


.05 


.397 


.269 


.208 


.180 


.204 


Sewing machines 






5.08 


.134 


.034 


.406 


.172 


.154 


.181 


.093 


Screw machines . 






6.33 


.381 


.05 


.633 


.291 


.235 


.296 


.396 


Average . . . 






4.83 


.309 


.048 


.428 


.189 


.154 


.406 


.195 



For group driving determine average horse-power for each tool, add these 
together and use a motor with a capacity of from 40 to 70 per cent of the 
total thus obtained. The size of motor will depend upon the way the ma- 
chines are worked — i.e., cutting speed, feed, material cut, and whether mod- 
ern air-hardened tools are used; also to what extent machines are to operate 
simultaneously. The larger the group the smaller the motor relative to 
total power. 



1518 POWER REQUIRED TO DRIVE MACHINERY, ETC. 

Motor Power for Machine Tools. Actual Installation*. 

William R. Trigg Works. 

Horse-power of motors used at the Wm. R. Trigg Works, Richmond, Va. 
(See article by Wm. Burlingham, in September, 1902, Machinery.) 

*"*«■* H ofMo P t°or r 

18 in. Cincinnati D. H. shaper 3 

10 ft. Pond boring mill 20 

18 in. Newton slotter 7£ 

No. 6 Baush radial drill 5 

5 ft. radial drill 5 

14 in. Newton slotter 5 

36 in. X 12 ft. Woodward & Powell planer 15 

56 in. X 56 in. X 12 ft. Gray planer 20 

30 in. X 30 in. X 8 ft. Woodward & Powell planer .... 10 

No. 5 Mitts & Merrill keyseater 3 

No. 1 Newton floor boring machine 7.5 

38 in. X 44 ft. shaft lathe 7.5 

Niles hor. boring machine 15 

No. 4 duplex milling machine, Newton 10 

7 ft. Betts boring mill 15 

10-in. Betts slotter 3 

5 1-in. Baush boring mill 7.5 

No. 1 Acme bolt cutter 7.5 

42 in. X 42 in. X 20 ft. planer 15 

Dallett & Co. portable deck planer 5 

62 in. X 30 ft. Putnam lathe 10 

36 in. X 25 ft. Putnam lathe 7.5 

22 ft. Bending rolls 

Driving 35 

Lifting 10 

12 in. straightening rolls 15 

No. 3 double punch 10 

Duplex planer 15 

Double angle shear 10 

No. 4 punch 10 

No. 4 punch 10 

No. 2 punch 5 

No. 3 hor. punch 7.5 

No. 6 Sturtevant blower 12 

Hannibal Shops. 

Horse-power of motors used at the Hannibal shops of the St. Joseph and 
Hannibal Ry. {Railroad Gazette.) 

Machine Shop. 
Mo^i't^ Horse-Power 

Machine ' of Motor. 

54 in. planer 15 

42 in. planer 10 

32 in. planer 7.5 

Emery grinder 

Grindstone 

Double centering machine 3 

90 in. driving wheel lathe 6 

2 quartering ends of same 3 

48 in. lathe 5 

18 in. slotter 

22 in. shaft lathe 5 

Car wheel borer 5 

Car wheel preac ..-„,,,,., 10 



MOTOR POWER FOR MACHINE TOOLS. 1519 

Ayf„«i,;^« Horse-Power 

Machme - of Motor. 

Journal lathe 

Grindstone 10 

32 in. lathe 4 

18 in. shaper 5 

40 in. vertical drill 2 

4-spindle gang drill 7.5 

Milling machine 3 

Grinding machine 3 

32 in. lathe 

Flat turret lathe 4 

18 in. lathe 

18 in. brass turret lathe 

16 in. lathe 4 

16 in. lathe 

16 in. lathe 

Drill 5 

No. 5 radial drill 

Acme triple bolt cutter 

2 in. double bolt cutter 5 

No. 6 radial drill 5 

No. 5 oscillating grinder 25 

24 in. lathe 

24 in. lathe 5 

Acme nut tapper 3 

16 in. tool room lathe 2 

No. 2 oscillating grinder 

Twist drill grinder 5 

Boiler Shop. 

No. 6 Niles power bending rolls 35 

Double punch and shears 6 

Flue tumblers 15 

Flue cutter 

Flue scarfer 3.5 

Small punch 2 

Blacksmith Shop. 

Bolt header 

Grindstone 5 

Bolt shears 5 

Punch and shears 7.5 

Bradley hammer 5 

Forge blower 15 

Forge fan 10 

Wood Mill. 

Automatic cut-off saw 10 

38 in. band resaw 8 

Vertical borer 7.5 

Automatic car gainer 15 

Mortiser 15 

Buzz planer 7.5 

Single surfacer 13 

Planer and matcher 25 

Self-feed large rip saw 25 

Small rip saw 15 

Four-sided timber planer 45 

Power feed railroad cutoff saw 10 

Rip saw 15 

Outside moulder 22 . 5 

Double surfacer 17.5 

Upright moulder 9.5 

Large tenoner 7.5 

Scroll saw , . , , 2 



1520 POWER REQUIRED TO DRIVE MACHINERY, ETC. 

MonhinPQ Horse-Power 

Machines. of Motor# 

Sharpener and gummer 

Band saw, setter and filer 

Emery wheels 

Grindstone 5 

Shavings exhauster 60 

Elevator 7.5 

Cabinet Shop. 

Patternmaker's lathes 5 

Scroll saw 3 

Tenoning machine 5 

Hollow chisel mortiser 4 

Universal saw bench 5 

Central Railroad of Hew Jersey Shops. 

Horse-power of motors used at the Central Ry. of New Jersey ShopSi 
(Railroad Gazette.) 

t tmi ^ Horse-Power 

Lathes - of Motor. 

88 in. wheel 7* 

72 in. driving wheel 5 

Single head axle 2 

Double head axle 5 

36 in. X 16 ft 4 

33 in. X 18 ft 3 

30 in. X 12 ft 3 

24 in. X 16 ft 3 

42 in. X 14 ft 3 

28 in. X 12 ft 2 

Planers, Slotters, Shapers. 

60 in. X 60 in. X 25 ft. Pond planer 15 

36 in. X 36 in. X 10 ft. Pond planer 5 

36 in. X 36 in. X 10 ft. planer . . 7* 

24 in. X 24 in. X 6 ft. Pond planer 5 

48 in. X 54 in. X 14 ft. planer 7$ 

24 in. crank planer 4 

16 in. traveling head shaper 3 

8 in. slotter 3 

14 in. slotter 4 

24 in. slotter 4 

Boring and Turning Mills — Boring Machines. 

80 in. boring mill 5 

39 in. boring mill t 5 

39 inch vertical boring machine 3 

36 in. car wheel boring machine 5 

8 ft. boring mill with slotter 7£ 

Driving wheel quartering machine . . . ; 5 

Rod borer 3 

Drill Presses. 

No. 3 Bickford radial drill 3 

30 in. drill press 2 

30 in. drill press . 2 

40 in. drill press (floating) 

40 in. drill press 3 

40 in. drill press (floating) 

8-spindle arch-bar drill 5 

Grinders. 

B. & S. surface grinder 3 

Water tool grinder 5 

Angle cock grinder 3 



MOTOR POWER FOR MACHINE TOOLS. 1521 

Miscellaneous. Horse-Power 

of Motor. 

54 in. throat single end punch . . . l 10 

No. 6 bulldozer complete 7£ 

3 in. heading and forging machine 10 

Newton cold-saw 10 

£ in. bolt heading machine 5 

i in. Acme single head bolt cutter 2 

Bolt shears 4 

10 ft. boiler rolls 5 

84 in. driving wheel press 5 

42 in. car wheel press 5 

36 in. car wheel press 3 

An Ideal Railway Shop. 
Estimated motor power for various tools for a railway shop. (From a 
paper read before the Master Mechanics' Convention, June, 1902, by 
L. R. Pomeroy.) Horse-Power 

Lathes, of Motor. 

90 in. driving wheel 7.5 

80 in. driving wheel 7.5 

42 in. truck wheel tire turning, heavy 5 

Axle, single, heavy, for driving axles 5 

Axle, double head 5 

48 in. X 14 ft. engine, heavy 5 

38 in. X 16 ft. engine, heavy 3 

30 in. X 12 ft. engine, heavy 3 

28 in. X 12 ft. engine, heavy 2 

26 in. X 8 ft. engine, very heavy 2.5 

20 in. X 10 ft. engine, medium . . 2 

18 in. X 10 ft. engine, medium 2 

16 in. X 8 ft. engine, medium 2 

2 X 24 flat turret . 3 

21 in. heavy screw machine 3 

20 in. universal monitor, for brass 1 

18 in. universal monitor, for brass 2 

16 in. Fox lathe, with turret 2 

12 in. speed lathe 2 

Drill Presses. 

72 in. radial, heavy 5 

60 in. radial, heavy 

48 in. radial, medium 2 

40 in. upright heavy 

36 in. upright heavy 2$ 

30 in. upright, heavy 

20 in. upright, light 

Cotter drilling machine 2 

Sensitive drill .5 

Grinding Machines. 

Landis grinder for piston rods, etc 3 

Surface grinder 

Universal grinding machine (same as No. 2B.&S.). ... 2 

Twist drill grinder 

Sellers or Disholt tool grinder 3 

Two 20 in. wet tool grinders 5 

Small tool grinder (B. & S. No. 1) 1 

Flexible swinging, grinding, and polishing machine .... 

Large buffing and polishing wheel 2£ 

Planers. 

72 in. X 72 in. X 14 ft 15 

60 in. X 60 in. X 28 ft 15 

54 in. X 52 in. X 14 ft 15 

42 in X 42 in. X 16 ft 10 

38 in. X 38 in. X 10 ft 7.5 

36 in. X 36 in. X 10 ft 7.5 

30 in. X 30 in. X 8 ft 5 



1522 POWER REQUIRED TO DRIVE MACHINERY, ETC. 



Horse-Powei 
, , ' of Motor. 

16 m traveling head shaper 2 

16 in. shaper 2 

14 in. shaper 2 

12 in. shaper 2 

Richards side planer, 20 in. X 6 in 5 

Slotting Machines. 

18 in. slotting machine 7.5 

14 in. slotting machine 5 

10 in. slotting machine 3 

Colburn keyseating machine 5 

Boring Mills. 

84 in. boring and turning mill, two heads 7.5 

62 in. boring and turning mill, two heads 5 

37 in. boring and turning mill, two heads 5 

30 in. horizontal boring and drilling machine 5 

Cylinder boring machine 7.5 

Milling Machines. 

Heavy vertical milling machine 10 

Vertical milling machine (No. 6 Becker-Brainard) .... 7.5 

Heavy slab milling machine 15 

Universal milling machine (heavy) 5 

Plain horizontal milling machine (same as Becker-Brainard 

No. 7) 4 

Small, plain milling machine for brass work 2.5 

Universal milling machine (same as B. & S. No. 3) . . . . 1 

Bolt and Nut Machinery. 

2\ in. single head bolt cutter 2 

1 J in. double head bolt cutter 4 

5-spindle nut-tapping machine 3 

Bolt-pointing machine 3 

Nut-facing machine 3 

Heavy power hacksaw 2 

Small power hacksaw 1 

Blacksmiths' Tools. 

Quick-acting belt hammer 5 

3 in. bolt heading and upsetting machine 3 

H bolt heading and upsetting machine 3 

Heavy shear to cut 4 X 4bar 7£ 

Shear to cut up to 5 X 1 in 5 

Shear to cut up to \\ in. round iron 5 

No. 3 Newton cold saw cutting-off machine 5 

Boiler Tools. 
16 ft. gap hyd. fixed riveter, pump, accumulator, and crane, 

complete 100 

Heavy boiler plate punch or shear, 48 in. throat depth . . 10 

Heavy boiler plate punch or shear, 30 in. throat depth . . 7.5 

Tank plate punch, 30 in. throat depth 5 

Tank plate shear, 24 in. throat depth 5 

Boiler plate shear, 30 in. throat depth, f in. plate ... 7.5 

Flange punch 5 

12 ft. boiler rolls for \ in. plate 

Light 6 ft. rolls 35 

Plate planer, 20 ft 3 

Woodworking Tools. 

Patternmaker's lathe 6 

Band saw 3 

Medium-sized saw bench, crosscut and rip saw 5 

Medium-sized hand planing and jointing machine f> 



HOBSE-POWER IN MACHINE-SHOPS. 



152£ 



W§ nrsft'powcr in machine -shops; Friction; 


Men 


employed. 




(Flatl 


Ler.) 












Horse-power. 




13 
o 


6 








> 


<D 


> 




H 
u 




Kind 




T3 . 


•3 >> 


'u 


* 






Name of Firm. 


of 






z* 


O 




Work. 




1$ 




"2 «M 

3 ee 


u 






3 




.S % 






o 


O 






o 


V 


a> 


o 


p 


d 


6 






H 


« 


tf 


^ 


K 


» 


% 


Lane & Bodley .... 


E. & W.W. 


58 








132 


2.27 




J. A. Fay & Co 


W. W. 


100 


15 


85 


15 


300 


3.00 


3.53 


Union Iron Works . . 


E.,M. M. 


400 


95 


305 


23 


1600 


4.00 


5.24 


Frontier Iron &Brass Wks 


M.E.,etc. 


25 


8 


17 


32 


150 


6.00 


8.82 


Taylor Mfg. Co 


E. 


95 








230 


2.42 




Baldwin Loco. Works 


L. 


2500 


2000 


500 


80 


4100 


1.64 


8.20 


W. Sellers & Co. (one de- 


















partment) 


H.M. 


102 


41 


61 


40 


300 


2.93 


4.87 


Pond Machine Tool Co. . 


M. T. 


180 


75 


105 


41 


432 


2.40 


4.11 


Pratt & Whitney Co. . . 


» 


120 








725 


6.04 




Brown & Sharpe Co. . . 


(< 


230 








900 


3.91 




Yale & Towne Co. . . . 


C.&L. 


135 


67 


68 


49 


700 


5.11 


10.25 


Ferracute Machine Co. . 


P. &D. 


35 


11 


24 


31 


90 


2.57 


3.75 


T. B. Wood's Sons . . . 


P. & S. 


12 








30 


2.50 




Bridgeport Forge Co. . 


H. F. 


150 


75 


75 


50 


130 


.86 


1.73 


Singer Mfg. Co 


S.M. 


1300 








3500 


2.69 




Howe Mfg. Co 


44 


350 








1500 


4.28 




Worcester Mach. Screw Co. 


M. S. 


40 








80 


2.00 




Hartford " " " 


" 


400 


100 


300 


25 


250 


0.62 


0.83 


Nicholson File Co. . . 


F. 


350 








400 


1.14 




Averages 





346.4 






38.6% 


818.3 


2.96 


5.13 



Abbreviations: E., engine; W.W., wood-working machinery; M. M., 
mining machinery ; M. E., marine engines ; L., locomotives ; H. M., heavy 
machinery ; M. T., machine-tools ; C. & L., cranes and locks ; P. & D., 
presses and dies; P. & S., pulleys and shafting; H. F., heavy f orgings ; 
S. M., sewing-machines ; M. S., machine-screws ; F., files. 

Verts at tlie Win, It. TrSg-g- Works. 

(See September, 1902, Machinery.) 

62 in. X 30 ft. lathe, turning hard cast iron. Tool of Sanderson self- 
hardening steel. About 6 H.P. required to run the lathe light. Experi- 
ments: (1) Cut, & in. deep, 1-16 in. feed; 21 ft. cutting speed; 33.8 lbs. metal 
removed per hour; 1.15 H.P. = .034 lb. wt. metal removed per hour. (2) 
Cut, i in. deep, 1-16 in. feed; 33 ft. cutting speed; 54.8 lbs. metal removed 
per hour; 1.52 H.P. = .028 lb. wt. metal removed per hour. 

36 in. X 12 ft. Woodward & Powell planer, two tools cutting on cast steel. 
Cuts were \ in. deep by 1-16 in. feed. First experiment, cutting speed, 17.15 
ft. per minute; reverse speed, 60 ft. per minute. H.P. cutting, 2.15; return- 
irg, 2.22; reverse to cut, 4.77; reverse to return, 11. Second experiment, 
cutting speed, 21.83 ft. per minute; reverse speed, 68.6 ft. per minute. H.P. 
catting, 2.85; returning, 3.06; reverse to cut, 6.52; reverse to return, 11. In 
these experiments the reverse to cut consumed (of course for an instant only) 
from 2.22 to 2 29 times the power required to cut; and the reverse to return 



1524 POWER REQUIRED TO DRIVE MACHINERY, ETC. 

from 4.95 to 3.59 the power required to return; or from 5.11 to 3.86 the 
power required for cutting. 

36 in. X 25 ft. Putnam lathe, cutting shaft nickel steel, oil tempered and 
annealed, with Sanderson self-hardening tool steel. Diameter work, 9f in. 
Experiments: (1) Cut £ in. deep X £ in. feed, 5.76 revolutions. H.P. = 1.5. 
(2) Cut 3-16 X i, 4.65 revolutions, H.P. = 1.76. (3) Cut J X £, 3.28 revo- 
lutions, H.P. = 1.9. (4) Cut 1 X £, 2.71 revolutions, H.P. = 1.26. 

Another line of experiments was conducted with the same lathe cutting 
nickel steel shaft 9f in. diameter, cut constant at i in. deep and feed £ in. per 
revolution. The speed of motor was gradually increased from No. 3 notch 
to No. 11 notch of the controller, representing an increase of motor revolu- 
tions from 220 to 700 per minute, or an increase in the revolutions of the 
lathe from 3.03 per minute to 9.64 per minute. The H.P. required increased 
from 1.068 to 4.26. 



Cotton Machinery. 

Wm. O. Webber. 
Looms. 



Make. 



Amoskeag, Whitin 
Amoskeag, Whitin 
Lowell Shop . . . 
Lowell Shop . . . 
Lowell Shop . . . 

Whitin 

Amoskeag .... 
Whitin 



Width. 



49 in. 
45 in. 
40 in. 
36 in. 
32 in. 
40 in. 
48 in. 
.40 in. 



Picks 
per Min. 



142 ft. 
142 ft. 
160 ft. 
160 ft. 
170 ft. 
144 ft. 
144 ft. 
147 ft. 



Picks 
per Inch. 



68X80 
68X80 
72X80 
64X90 
64X88 
80X84 
80X84 
84X92 



Warp. 

Weft. 



24 X31 
24 X31 
24 X31 
24 X38 

27* X38 
28 X33 
28 X33 
28 X33 



Horse- 
power. 



.254 

.214 

.273 

.286 

.311 

.2315 

.257 

.256 



Slashers. — 2,872 ends 

Cut in 84 seconds = 3 . 93 horse-power. 
Cut in 64 seconds = 4.574 horse-power. 
Cut in 52 seconds =5.53 horse-power. 

Warpers. — 359 ends, 50 yds. per min. = .313 H.P. 

Shears, 4 blades and fans, 1,800 R.P.M. 

100 yards per min. 42 inch cloth = 6.07 H.P. 



Cards. 









Horse- 








power. 


Finisher, Lowell 


36 inch cylinder 


128 R. 


.187 


Finisher, Amoskeag 


36 inch cylinder 


140 R. 


.247 


Finisher, Whitim 


36 inch cylinder 


140 R. 


.19 


Lowell breaker 


36 inch cylinder 


128 R. 


.225 


Amoskeag breaker 


36 inch cylinder 


140 R. 


.247 


Whitin breaker 


36 inch cylinder 


140 R. 


.173 


Revolving top flat card . . . 


40 inch cylinder 


162 R. 


.921 



POWER REQUIRED. 



1525 



Printing* machinery, Power Required. 

Wm. 0. Webber. 



30 in. X 52 in. 2 rev. No. 8 Cottrell press, 19 impressions per minute 
27 in. X 41 in. No. 20 Adams press, 16 impressions per minute 

32 in. X 54 in. Huber perfecting press 

43 in. X 64 in. Huber perfecting press, automatic feed 

27 in. X 41 in. No. 4 Adams job press 

26 in. X 40 in. No. 2 Adams job press 

32 in. X 54 in. No. 1 Potter cylinder roller press 

26 in. No. 1 Hoe perfecting press 

Web paper- wetting machine 



Horse- 
Power. 



1.189 
.68 

2.44 

5.55 
.43 
.337 
.50 

5.41 
.52 



Newspaper Printing Machinery. 



One 10 page web perfecting press, 12,000 per hour 
One 10 page' web perfecting press, 24,000 per hour 
One 12 page web perfecting press, 12,000 per hour 
One 12 page web perfecting press, 24,000 per hour 
One 32 page web perfecting press, 12 000 per hour 



Horse- 
power. 



15.39 

31. 

20.45 

29.56 

28.73 



Calico Printing Machinery — Capacity 100 yds. print goods per min. 



Horse- 
power. 



One 19 cylinder, soaper and dryer, full .... 

One cutting machine, full 

One set drying cans to cutting machine, full . . 
One back starcher, 3 wide machines, full. . . . 
One indigo skying machine, 5 vats, all working full 
One 40 in. 5 roll calender, working full .... 
One single color printing machine 



Rev. 


Foot- 


per 
min. 


pounds. 


110 


2,182 


65 


1,525 


110 


1,282 


115 


2,330 


64 


2,635 


234 


5,390 



3.97 
2.77 
2.33 
4.24 
4.78 
9.80 
10.6 



Power Required For Sewings-machines. 

Light-running 20 machines to 1 h.p. 

Heavy work on same 15 " " " 

Leather-sewing 12 " *' *' 

Button-hole machines ... 8 to 12 " " " 



1526 POWER REQUIRED TO DRIVE MACHINERY, ETC. 



POWER C©]¥SU]fri?Ti©]¥. 



Character 


Average 

K.W. 

Hours 

per 

Month. 


Average 
Con- 
nected 


Indi- 
vidual 


Ave. 

No. of 


Connect- 
ed Motor 
Load 




of Installations. 


Motor 
Load, 
H.P. 


or 
Group 
Drive.* 


Mo- 
tors. 


Times 

Average 

Load. 


O <n 


Bakeries 


1,582 


32.8 


G 


2.7 


27.8 


~~17 


Bakeries 




705.3 
326.7 


22.5 
51.4 


I 
G 


3.1 

2.8 


19.5 
33.3 


g 


Boiler shops . . . 




11 


Boiler shops , . . 




1,172 


32.2 


I 


5.2 


20.7 


5 


Boots and shoes . 




3,050 


39.7 


G 


5.8 


42.8 


13 


Box making . . . 




1,555 


18.1 


G 


4.3 


45.4 


20 


Blacksmiths . . . 




586 
5,736 


9.4 

40.5 


G 
G 


2.2 

7.4 


34.2 
45.0 


12 


Brass finishing . . 




9 


Butchers and packers 


1,990 


24.8 


G 


2.0 


36.4 


13 


Butchers and packers 


1,049 


36.9 


I 


6.7 


18.8 


10 


Breweries 


12,310 
644 


94.0 
14.5 


G 
G 


4.6 
1.6 


33.0 
30.1 


8 


Carpet cleaning . . 


12 


Cement mixing . . . 


2,009 


37.5 


G 


1.0 


24.9 


4 


Candy manufactory . 


1,893 


26.6 


G 


3.5 


33.6 


10 


Candy manufactory . 


796 


29.9 


I 


7.5 


16.3 


8 


Cotton mills .... 


11,829 


99.0 


G 


3.0 


60.1 


3 


Carriage works . . . 


2,091 


24.8 


G 


3.5 


35.5 


22 


Chemical works . . 


4,802 


109. 


G 


5.5 


23.5 


6 


Clothing manufacturing 


; 1,181 


23. 


G 


4.0 


44.5 


33 


Grain elevators . . . 


3,842 


114.4 


G &I 


3.8 


32.6 


19 


Feather cleaners . . 


2,447 


54.4 


G&I 


5.5 


25.7 


2 


General manufacturing 


6,133 


67.5 


G&I 


6.4 


33.9 


181 


Engrv. and electrotypii 


lg 863 


12.4 


G 


2.5 


46.9 


8 


Engrv. and electrotypii 


ig 2,369 


46.3 


I 


26.7 


22.5 


7 


Glass grinding . . . 


2,760 


33.5 


G 


3.0 


36.6 


6 


Foundries 


2,057 
2,419 


27.7 
81.1 


G 

I 


2.3 
7.0 


43.7 
21.3 


15 


Foundries 


18 


Furniture manufacturii 


ig 1,750 


35.7 


G 


3 6 


35.6 


9 


Flour mills .... 


41,276 
' 2,905 


148.5 
70.5 


G 
G 


3.1 
6.4 


48.1 
28.3 


13 


Hoisting and conveying 


5 


Hoisting and conveying 


5 6,562 


253. 


I 


20.0 


13.0 


9 


Ice cream 


596 
4,645 


31. 

36.7 


G&I 
G&I 


5.4 

2.5 


35.9 
53.4 


7 


Refrigeration . . . 


17 


Jewelry manufacturing 


2,526 


31.7 


G 


4.6 


31.6 


5 


Laundries 


676 


10.8 


G 


2.1 


34.0 


19 


Marble finishing . . 


1,464 


19.8 


G &I 


1.3 


51.3 


12 


Machine shops . . . 


4,006 


57.6 


G 


4.5 


34.5 


51 


Newspapers .... 


3,150 


47.4 


G 


4.8 


38.0 


24 


Newspapers .... 


4,975 


137.0 


I 


17.3 


15.1 


21 


Ornamental iron works 


2,771 


38.4 


G 


3.6 


41.6 


9 


Paint manufacturing 


2,814 


60.4 


G&I 


4.6 


26.5 


11 


Printers and bookbinde 


rs 1,147 


20.4 


G 


2.6 


39.5 


54 


Printers and bookbinde 


rs 6,215 


76.8 


I 


24.0 


26.0 


39 


Plumbing manufacturii 


ig 3,020 


42.4 


G 


4.8 


21.5 


15 


Rubber manufacturing 


1,051 


26.0 


G &I 


15. 


24.7 


2 


Sheet metal mfg. . . 


1,321 


38.8 


G 


3.7 


27.3 


17 


Soap manufacturing 
Seeds 


3,434 


73.0 


G 


10.0 


27.6 


2 


2,917 


55.1 


G&I 


5.8 


24.4 


5 


Structural steel . . 




6,514 


176.0 


I 


16.1 


18.5 


6 


Structural steel . . 




77,704 


552.1 


G 


35.6 


31.1 


6 


Stone cutting . . 




7,425 


76.5 


G&I 


3.8 


34.4 


20 


Tanners 




2,466 


28.6 


G 


2.6 


54.6 


5 


Tobacco working . 




3,441 


62.3 


G 


7.0 


37.5 


4 


Wholesale groceries 




2,005 


47.0 


G&I 


4.5 


26.0 


17 


Wood working . . 




2 306 


39.5 


G&I 


3.6 


33.3 


64 


Woolen mills . . . 




20,985 


150. 


G 


3.0 


71.0 


1 


.. Averages. . . . 




3,500 


6.08 


33.9 


951 


* G 


B 


tands for Grc 


up. I. i 


or Indiv 


dual. 







POWER FOR ELECTRIC CRANES. 1527 

Power for Electric Cranes. 

Journal Society of Western Engineers. 

The following data on the power required for electric traveling cranes were 
given by Mr. S. S. Wales at a meeting of the Engineers' Society of Western 
Pennsylvania. 

An electric crane is divided into three general parts — bridge, trolley, and 
hoist, each of which has its own motor and controlling system, and each 
subjected to different conditions of work. 

For the bridge, where the ratio of axle bearings to diameter of wheel is 
between one to five and one to six, the following table will answer our pur- 
pose for weights and traction for different spans: 

Let L = working load of crane in tons. 

Jp = weight of bridge alone in tons. 
w = weight of trolley alone in tons. 
S = speed in feet per minute. 
P — pounds per ton required. 



Span. 


W. 


P. 


25 ft. 


.3L 


30 lbs. 


50 ft. 


.6L 


35 lbs. 


75 ft. 


1. L 


40 lbs. 


100 ft. 


1.5L 


45 lbs. 



For the trolley we would assume the weight and traction as shown in the 
following table: 

L. W. P, 

1 to 25 tons. .3L 30 lbs. 

25 to 75 tons. AL 35 lbs. 

75 to 150 tons. .5L 40 lbs. 

Now the power required for bridge will be: 

{L + W + w)XP XS __ Hp 
33,000 ' # 

which result will be used in connection with the motor characteristic to 
determine the gear reduction from motor to track wheel. As the nominal 
H.P. rating of a series motor is based on an hour's run with a rise of 75° C. 
above the surrounding air and as conditions of bad track, bad bearings, or 
poor alignment of track wheels may be met with, 1* times the above result 
should be taken as the proper size motor for the bridge. 
For the trolley the power required would be: 

(L + w) X P X S = 

33,000 * ' 

which will be used for speed and gear reductions, but 1\ times this should 
be used for size of motor. 

For hoist work we cannot have so large margin of power, as the variation 
from full load to no load may imply a possible dangerous increase of speed, 
and unless the crane is to be subjected to its maximum load continuously or 
is to be worked where the temperature of the surrounding air will be high, 
it is safe to use the size found by assuming 1 H.P. per 10 ft. ton per minute 
of hoisting. This is nearly equal to assuming the useful work done as 60 
per cent of the power consumed. 

As an illustration, let us take a crane of 50-ton capacity, lifting speed of 
hoist 15 feet per minute. Bridge to be 70 feet span and to run 200 feet per 
minute with load. Trolley to travel 100 feet per minute with full load. 
On the foregoing assumption the bridge would weigh 50 tons and require 
40 pounds per ton for traction, and the trolley would weigh 20 tons, and 
require 35 pounds per ton for traction. 

The power for the bridge would be: 

120 X40X 200 _ 9Q pr p 
3p00 ~ 



1528 POWER REQUIRED TO DRIVE MACHINERY, ETC. 

and the size motor 1* times this would give 43* H.P. or 50 H.P., this 
being the nearest standard size, and the specification should read not less 
than 50 H.P. motor to be used for bridge travel. 
Similarly the trolley will require 

70 X 35 X 100 _ „ p 
33^00 -7.43 H.P. 

and the size motor required will be 1£ times this, or 8 . 28 H.P. 
The hoist would require 

50 X 15 



10 



= 75 H.P. 



and would be specified not less than 75 H.P. motor to be used as hoists. 



Operating- Cost of Electric Elevators, 

From Circular of Cincinnati Gas and Electric Co. 
Six Months' Average. 



Freight Elevators.* 


Passenger Elevators, t 






Average 






Average 


No. 


H.P. 


Monthly 
Cost. 


No. 


H.P. 


Monthly 
Cost. 




10 


$11.92 


1 


15 


$39.54 




10 


10.00 


2 


20* 


19.05 




20 


33.01 


1 


18 


65.83 




5 


5.00 


2 


17* 


17.30 




5 


4.00 


1 


22* 


23.57 




5 


5.00 


1 


15 


14.22 




5 


4.00 


5 


73 


59.40 




5 


7.37 


2 


32 


38.16 




5 


4.00 


3 


38* 


34.55 




5 


11.86 


2 


10* 


19.80 




10 


9.50 


1 


8 


9.73 




10 


9.50 


1 


8 


14.87 




8* 


9.49 


1 


11 


18.42 




25 


23.75 


1 


15 


9.15 




5 


3.50 


1 


15 


22.01 




10 


9.50 


1 


15 


4.75 




5 


4.75 


2 


16* 


17.62 




10 


11.30 


1 


12* 


14.66 




8 


7.60 


2 


12* 


12.33 




20 


28.06 


2 


11 


17.74 




7* 


7.12 


3 


41 


37.95 




5 


4.75 


1 


10 


23.49 




5 


4.60 


1 


16 


18.24 




5 


5.25 


1 


10 


19.05 




7* 


7.12 


1 


10 


19.50 








1 
1 


13 
10 


13.30 
18.98 


30 


221* 


$241.95 








1 
45 


26 
523 


35.31 




$658.58 



* Average cost per elevator per month $8. Average cost per month 
per horse-power, $1.09. 

t Average cost per elevator per month, $14.64. Average cost per month 
>r horse-power, $1.26. 



per 



POWER USED BY MACHINE TOOLS. 



1529 



Saving: by Electric Drive. — Fig. Nos. 2 and 3 show graphically 
the saving made in power by the use of electric drive over the use of 
shafting and belting. 



60 



40 



LU 

O 
OL 

I 

UJ 
CD 

£20 
O 

I 






TIME 



ESTIMATED FRICTION 
LOSS IN ENGINE 



ESTIMATED FRICTION 
LOSS IN ENGINE 



9 10 

A.M. 



3 ± 
P.M. 



Fig. 2. 1895, Diagram of Losses in Power Transmission, 
Factory of Central Stamping Co., Brooklyn, N.Y. 
Crocker- Wheeler Electric Company. 




Fig. 3. 1895, Diagram of Losses in Power Transmission, 
Factory of Central Stamping Co., Newark, N.J. 
Crocker-Wheeler Electric Company. 



1530 POWER REQUIRED TO DRIVE MACHINERY, ETC. 



LIST ©E TOOLI A^D SUPPLIES USJEEUJL IH 

IXSTAEMXO ELECTRIC MOHTS AJD 

DYIAMOS. 



1 Tool chest. 

1 Magneto and cable. 

1 Speed indicator. 

1 Tape line, 75 ft. 

1 Rule, 2 ft. 

1 Scraper, for bearings. 

1 Blow lamp. 

1 Clawhammer, No. 13. 

1 Ball pein hammer, No. 24. 

1 B. & S. pocket wrench, No. 4. 

1 Monkey wrench, 10 inch. 

1 Set (2) Champion screw-drivers. 

1 Large screw-driver, 12-inch. 

1 Off-set screw-driver. 

1 Ratchet brace, No. 33. 

Bits, h |, h f , I, 3, 1 inch. 
1 Clarke Expansive bit, ^ to 3 inch. 
1 Screw-driver bit. 
1 Gimlet bit. 
1 Wood countersink. 
1 Extension drill, § in. length, 24 in. 
1 Long or extension gimlet. 
1 Cold chisel, f inch. 
1 Half round cold chisel. 
1 Cape chisel. 

1 Wood chisel, firmer paring, f inch. 
1 Brick drill. 



Piles, one each : round, flat, half- 
round and three-square. 
1 Saw, 20 inch. 
1 Hack-saw, 10 inch. 
10 Extra saw blades. 
1 Plumb bob. 
1 Brad awl. 
1 Pair carbon tongs. 
1 Soldering copper, No. 3. 
1 Pound of solder. 
1 Pair of climbers. 
1 Come-along. 
1 Splicing-clamp. 
1 Strap and vise. 
1 Pair line pliers, 8 inch. 
1 Pair of sirle-cutting pliers, 5 inch. 
1 Pair of diagonal-cutting pliers, 5 in 
1 Pair of round-nose pliers, 5 inch. 
1 Pair of flat-nose pliers, 5 inch. 

1 Pair of burner pliers, 7 inch. 
6 Sheets of emery cloth. 
6 Sheets of crocus cloth. 

2 Gross of assorted machine screws. 
2 Gross of assorted wood screws. 

150 Special screws. 
Taps, 6-30, 10-24, 12-24, 18-18. 
Drills, 34, 21, 9, 15-64. 
Tap wrench. 

The following-named tools will probably be required in constructing lines 
for city or commercial lighting : 

(Davis.) 



Article. 



Stubs' pliers, plain . . . . , 
Climbers and straps . . . . , 
Pulley-block and ecc. clamp 
Come-along and strap . . . , 

Splicing-clamps , 

Linemen's tool-bag and strap , 
Soldering-furnace . . . . , 
Gasoline blow-pipes . . . . 

Soldering coppers , 

Pole-hole shovels 

Pole-hole spoon, regular . . , 
Octagon digging-bars . . . 

Tamping-bars , 

Crowbar 

Pick-axe 

Carrying-hook, heavy . . . 

Cant-hook 

Pike-poles 

Pole-supporter 

Comb, pay-out reel and straps 

Nail-hammer 

Linemen's broad hatchets 

Drawing-knives 

Hand-saw 

Ratchet-brace, bits .... 
Screw-drivers . . r . . . 

Wrench 

Bastard file 



Size. 



8 in. 

'fo ' 
No. 3 
B. &S. 



21b. 
8 ft. 

7 ft. 

8 ft. 
7 ft. 

10 1b. 



4 ft. 
16 ft. 

6 ft; 

' i lb! 

6 in. 
12 in. 
26 in. 
10 in. 

8 in. 
12 in. 
12 in. 



Cost 
about 



$2.00 
3.00 
8.00 
2.25 
2.50 
4.80 
6.00 
6.00 

.95 
1.50 
1.25 
3.50 
2.60 

.90 

.75 
6.00 
2.00 
2.40 
12.00 
20.00 
1.00 
1.50 
2.10 
1.50 
3.00 

.80 
1.25 

.30 



THAWING WATER PIPES. 



1531 



APPROXIMATE LIST OF STPPIIES 

REQUIRED IN INSTALLING 15 CITY LAMPS AND 20 COMMERCIAL LAMPS 
ON A FITE-MILE CIRCUIT, SETTING POLES 132 FEET APART. 

(Davis.) 



Articles. 



Electric-light poles 
Electric-light poles 
Electric-light poles 
Cross-arms, 4-pin . 
Painted oak pins . 
Oak pins and bolts 
Iron break-arms . 
Lag-screws and washers 
Glass insulators, D. G. 
Pole steps .... 
Guy stranded cable . 
Cross-arm brace and bolts 
Line wire 



Size or 
Diameter. 



30 ft., 6 in. 
35 ft., 7 in. 
40 ft., 7 in. 

4 ft. 

H in. 



\ X 7 in. 

f X 8'in*. 
fin. 

6BS' 



Price 
about 



$2.40 each 

4.15 " 

5.50 " 

.30 " 

.02 " 

.07 " 

.75 " 

.04 " 

.07* " 

.05 M 

.07 lb. 

.20 each 

125.00 mi. 



Quantity. 



180 

40 * 
200 
800 

24 

25 

400 

850 

2500 

500 lbs. 

40 
6 miles 



MATERIAL REdriRED FOR COKHECTIIO IX 
LAMPS. 

(Davis.) 



Sleet-proof pulleys . . 
Street-lamp cleats, iron 
Arc-lamp cordage . 
Suspension cable . 
Hard-rubber tube . 
Soft-rubber tubing 
Arc cut-out . . . 
Porcelain insulators 

screws . . . 
Oak brackets and spikes 



and 



fin. 

| in -5 
IXl 
I in. 



|0.75 each. 
25 " 
1.25 hd. ft. 

.02| ft. 
1.50 lb. 
.20 ft. 
3.50 each 

2.40 hd. 
2.50 " 



30 

15 

25 

3000 ft. 

5 lbs. 

200 ft. 

20 

400 
150 



THA WIXO FROZEX WATER PIPE§ 
ELECTRICALLY. 

The use of electricity for thawing out frozen underground water pipes 
requires a transformer say of 10 or 20 kilowatts capacity, which can be 
taken to the locality required, connecting the primary with the high ten- 
sion circuit passing the place, and then connecting the secondary through 
an ampere meter and rheostat to the service in trouble. Where services 
from the street mains to two adjacent houses are both frozen, it is only 
necessary to connect the secondary circuit to the kitchen faucet of both 
houses and thus the circuit is complete through the service of one house 
to the street main and back through the service of the second house. 

Where the service of but one house is to be thawed, one end of the sec- 
ondary circuit is connected to the kitchen faucet and the other end to the 
nearest street hydrant or other street connection. Currents varying from 
20 to 500 amperes are used, obviously, varying according to the conditions; 
and the time taken to thaw the ice sufficiently to start the water running 
will be from 10 to 45 minutes or perhaps 3 to 8 hours, according to circum- 
stances. 



1532 POWER REQUIRED TO THAW WATER PIPES. 

The average time for the ordinary house service will seldom exceed 45 
minutes, while for a five or six inch pipe that has been frozen solid the 
highest amount of current and time mentioned will be required. 

It is very seldom necessary to melt the entire plug of ice, as the thawing 
of a thin sheet nearest the metal will start the water running and that will 
consume the ice in a short time. 

The following table is compiled from data that have appeared in various 
periodicals. It represents average conditions for last year, and shows what 
may be expected in the future: 



Size Pipe. 


Length. 


Volts. 


Amps. 


Time Required 
to Thaw. 


I" 


40 ft. 


50 


300 


8 min. 


100 ft. 


55 


135 


10 min. 


F 


250 ft. 


50 


400 


20 min. 


1" 


250 ft. 


50 


500 


20 min. 


1" 


700 ft. 


55 


175 


5 hrs. 


4" 


1300 ft. 


55 


260 


3 hrs. 


10" 


800 ft. 


70 


400 


2 hrs. 



The following notes on melting points of various substances may be of 
assistance in checking thermometers and showing the safe limits on elec- 
trical apparatus that operates in heated conditions. 

C. F. 

Pure cane sugar (granulated) melts at 160 320 

Tin melts at • . 235 455 

Bismuth melts at 269 518 

Lead melts at 327 618 

Zinc melts at . 419 788 



^ 



$ 



<C> 



I I I IV 

; 



• ^Accoai ith pa: 

INDEX. 



Abbreviations for units, 6. 
Absohm, value of, 7. 
Absolute units, 2. 
Absorbent for X-ray tubes, 1251. 
Abvolt, value of, 7. 
Acceleration, average rate of, 666. 
definition of, 3. 
formula for, 664. 
Acetic acid in electrolyte, test for, 

878. 
Acheson process, graphite produc- 
tion by, 1245. 
Acid, conducting power of, table of, 

905. 
Acker process, caustic soda by, 1240. 
Acoustic telephone call system, 294. 
Action of wattmeters, 1039. 
Active material, increase of, 873. 

loss of battery plates, 881. 
Acyclic machines, def. of, 504. 
Adhesion of cement, 1294. 
Admittance, symbol of, 8. 
Admixture of copper, effect of, 144. 
Advance wire, properties of, 202, 207. 
Aerial circuits, charging current per 
1000 feet of A.C., 253-258. 
lines, res. of, 61. 
telephone cables, 188. 

capacity of, 1085. 
wires, capacity per 1000 feet of, 
table of, 252. 

location of orosses in, 327. 
A-geing of iron and steel, 455. 
of transformers, guarantee against 

serious, 498. 
tests, curves of, 453. 
A I. E. E., copper wire tables of, 

146. 
Air-blast transformers, 449. 
dielectric strength of, 233. 
-gap ampere turns, 367. 
break down, 1056. 



Air-gap, discussion of, 363. 
flux, 365. 
pumps, 1445. 
resistance, effect of moving body 

on, 659. 
space in grates, 1329. 
spec. ind. cap. of, 35. 
Alarm, fire, U. S. Navy, 1210. 
Alcohol, spec. ind. cap. of, 37. 
All-day efficiency of transformers, 

454. 
Alloys of copper, conductivity of, 
table of, 910. 
of copper, table of, 144. 
phys. and elec. prop, of, table of, 
134-140. 
Alternating circuits, power in, meas 
of, 69. 
current ammeters, use of, 945. 
arc circuits, reactance coil for, 

466. 
arc lamps, 568. 
armatures, 410. 

circuit breakers, design of, 952. 
circuits, protection against 
abnormal potentials on, 981. 
circuits, prop, of, 259. 
definition of, 501. 
distribution, pressure for, 261. 
electrolysis, 860. 
electromagnets, 127. 
flow, formula for, 1213. 
lines, table for calc, 279. 
meas. of, 26, 42. 
motor equipments, weight of, 

719. 
motors, 421. 

potential regulators, 467. 
power curves, 70. 
railway motor characteristic; 

713. 
system, 707. 



1533 



1534 



INDEX. 



Alternating current railway trolleys, 
640. 

meas. self-induction with, 66. 

single-phase sub-station, views 
of, 943. 

switchboard panels, 912. 

voltage and current in terms of 
D.C., 438. 

wiring examples, 272. 
Alternators, parallel running of, 419. 
regulation tests of, 382. 
regulators for, 409. 
revolving field type, 409. 
armature reaction of, 414. 
connected in multiple, 420. 
definition of, 502. 
E.M.F. of. 404. 
Aluminum and copper compared, 

195. 
alloys, spec, gravity of, 1514. 
bar data, 911. 
conductors, calc. of, 277. 
fusing effect of current on, 217. 
phys. and elec. prop, of, 134. 
production of, 1238. 
spec. res. of, 132. 
temperature coef. of, 133. 
wire, cost of, 195. 

deflection in feet of, 226. 

for high tension lines, 199. 

limit of sag for, 225. 

properties of, 194. 

reactance factors for, 266. 

skin effect factor for, 238. 

stranded, dimensions of, 197. 

table of resistance of, 196, 198. 

weather-proof, 197. 
Alundum furnace, 1245. 
Amalgamating zinc, 14. 
Am. Inst, of Elec. Eng., rules of, 500a. 

copper wire tables of, 146. 
Ammeters, A. C. type, use of, 945. 
and voltmeters, meas. res. with, 78. 
Bristol recording, 1036. 
description of, 41. 
differential, use of, 903. 
jacks for, 922. 
scales of, figuring of, 946. 
shunts for, 41. 
soft iron, 41. 



Ammunition hoist, electric, 1147, 

1191. 
Ampere, definition of, 5. 

-hour meter, Shallenberger, 1028, 
international, def. of, 9. 
measurement of, 10. 
specification for determining, 10< 
value of, 8. 

-turns for armature teeth, 367. 
in field magnets, 366. 
of A.C. armatures, 414. 
of air-gap, 369. 

of electromagnets, table of, 114. 
of plunger solenoids, table of, 
128. 
Analyses of boiler feed waters, 1366. 
of coals, 1352. 
of coke, 1353. 
of gaseous fuels, 1357. 
Anchorage of trolley wires, 637. 
Anchored lamps, navy spec, for, 

1173. 
Angle of lag in three-phase circuits, 

406. 
Angular distance between brushes, 
table of, 344. 
velocity, 3, 1505. 
Anilin, spec. ind. cap. of, 37. 
Animal oils, 1497. 
Annealing of armor plate, electric, 

1274. 
Annual expenses of telephone cables, 

1087. 
Annunciator wiring, 294. 
Anode, definition of, 1229. 

impurities, effect of, 1237. 
Answering jacks, 1091. 
Antenna, 1057. 

Anthony bridge, diagram of, 31. 
Anthracite, properties of, 1351. 

sizing tests of, 1354. 
Anti-cathode, use of, 1248. 
Anti-coherers, 1066. 
Antimony, phys. and elec. prop, of 
134. 
spec. res. of, 132. 
temperature coef. of, 133. 
Anylene, spec. ind. cap. of, 37. 
Apothecaries' measure, 1500. 
Apparent power, def. of, 50 . 



INDEX. 



1535 



Arachid oil, spec. ind. cap. of, 37. 
Arc, chemical effect of electric, 

1232. 
circuits, reactance coil for A. C, 

466. 
dynamo, efficiency curves of, 338. 

ext. characteristic curve of, 337. 

permeability curve of, 338. 
lamps, candle-power of, 579- 

classification of, 568. 

regulation in, 576, 

trimming of, 583. 
light carbons, tests of, 577. 

circuits, ins. res. of, 81. 

efficiency, 580. 

installations, table of, 598. 
rectifiers, G.E. mercury type, 480. 
station lightning arrester, 986. 
switchboards, 922. 
type furnace, 1244. 
Ardois signal system, 1181. 
Armature coils, allowable number of 

turns for, 374. 
coils, placing of, 358. 

trial slots for, 373. 

values for number of, 373. 

wire for, 372. 
conductors, carrying cap. of, 375. 

drag on, 351. 

size of, data on, 358 . 
commutation, 364. 
cores, data on, 357. 

disks for, 356. 

energy dissipation in, 107. 

hysteresis in, 341. 

magnetic density of, 357. 
faults, tests for, 402. 
ground, test for, 402. 
losses, formula for, 358. 
reaction, 350. 

data on, 364. 

in alternators, 414. 
resistance loss, meas. of, 509. 

meas. of, 79, 401. 
shafts, 341. 
slots, design of, 357. 

sizes of, 372. 
teeth, ampere turns for, 367. 
teeth, design of, 357. 
winding, 342. 



Armature coils, constants, 376. 

for converters, 441. 
Armatures, disk type, 341. 

drum type, 341. 

heating of, 349. 

of alternators, 408. 
copper loss in, 407. 
winding of, 410. 

ring type, 341. 

slotted or toothed type, 341. 

temperature rise in, 358. 

ventilation of, 350. 
Armored submarine cables, 189. 
Armor plate, annealing of, electric, 

1274. 
Army, U. S., use of elec. in, 1123. 
Artificial light needed in each 

month, 606. 
Ash in American coals, 1350. 
A.S.M.E. boiler test rules, 1384. 

direct connected sets, standards 
of, 1435. 
Astatic galvanometer, Kelvin type t 
23. 

needle system, 23. 
Atkinson repeater, 1048. 
Atmospheric discharges, 1278. 

electricity, effect on transformers 
of, 449. 
Auto-coherers, 1066. 
Automatic block signalling, 622. 

booster, use of, 892. 

exchange systems, 1105. 

telephone system, 1122. 
Automobile batteries, 1227. 

electrolyte for, 877. 

electric, 1224. 

motors, 1227. 

power required by, 1224. 
Auto-starter, connections of, 954. 

-transformer, def . of, 503. 
railway control, 767. 
use of, 429. 
Auxiliary armature coils, 351. 

bus bars, 935. 

control system, 767. 

D.C. circuits, 939. 

power, 867. 

relays, 956. 

trunk signals, 1096. 



1536 



INDEX. 



Average dynamo efficiencies, table 

of, 377. 
Avoirdupois measure, 1500. 
Axle welding, electric, 1272 
Ayrton and Mather shunt, 29. 
and Perry secohmmeter, 69. 
and Perry standard of self- 
induction, 66. 
and Sumpner method, A.C. power 

by, 71. 
and Sumpner test of transformers, 

496. 
method, location of crosses in 
cables by, 327. 

Backward lead of motor brushes, 

353. 
Balance coil for three-wire system 
generator, 355. 
Kelvin electric, 43. 
method, determ. magn. values by, 
91. 
Balanced three-phase circuit, energy 
in, 405. 
three-phase system, 73. 
Balancing circuits by transposition, 
285. 
magnetic circuits in dynamos, 349. 
resistance for arc lamps, 581. 
transformers for three-wire second- 
aries, 472. 
Baldwin Locomotive Works, power 

tests at, 1517. 
Ballistic galvanometer, 25. 

method, determ. magn. values by, 
91. 
B. A. Ohm, value of, 131. 
Bare wires, carrying capacity of, 

208. 
Barie, value of, 7. 

Barn test for motor efficiency, 803. 
Barometric correction, 519. 
Barrel armature winding constants, 

376. 
Bars, commutator, number of, 361. 
Baths for plating, 1233. 
Batteries, automobile storage, 1227. 
dry, descr. of, 18. 
E.M.F. of, meas. of, 62, 74. 
E.M.F., comparison of, 76. 



Batteries, grouping of, 19. 
ins. res. of, meas. of, 87. 
primary, action of, 14. 
resistance of, 60. 
Battery capacity for given dis- 
charge, 900. 
charging with arc rectifiers, 482. 
chloride of silver type, 16. 
equipment, installation of, 897. 
plates, appearance of, 874. 

buckling of, 881. 

cadmium test of, 878. 

dimensions of, 883. 

types of, 874. 
system, three-wire, 899. 
transmitters, 1071. 
troubles, 881. 
while working, res. of, 61. 
Battle order indicators, U. S. Navy, 

1202. 
service, navy, 1153. 
Beams and channels, Trenton, safe 
loads on, 1313. 

spacing of, 1315. 
bending moment of, 1308. 
breaking load on, 1309. 
coefficient changes for special 

forms of, 1311. 
coefficients for special cases of,1311. 
deck, 1314. 
deflection of, 1309. 
flexure of, 1308. 
general formulae for, 1309. 
max. moment of stress of, 131Q. 
modulus of rupture of, 1308. 
of uniform cross-section, tra>-,d. 

str. on, 1309. 
of uniform strength, 1312. 
resisting moment of, 1308. 
safe load on steel, 1310. 

on southern pine, 1320. 

on wood, 1318. 
spacing of, for various loads, 1»- 5. 
strength of white pine, 1319. 
transverse strength of, 1308. 
Bearing friction in dynamos, 386- 

friction, meas. of, 509. 
Bearings, meter, 1009. 
Bell telephone receiver, 1070. 
Bell wiring, 293. 



INDEX. 



1537 



Bells for cable ends, des. of, 333. 

U. S. Navy, spec, for, 1211. 
Belting, leather, 1487. 

horse-power of double, 1489. 
of leather, 1489. 
of single, 1489. 

strength of leather, 1487. 
Belt, length in roll, 1489. 

length of, 1489. 

-off test of motor, 396. 

-on test of motor, 396. 

slip of, 1493. 

• eight of leather, 1489. 

width for given h. p., 1488. 
Bending moment of beams, 1308. 
Bends, pipe, dimensions of, 1431. 
Benzene, spec. ind. cap. of, 37, 227. 
Bernardos system of welding, 1274. 
Bessemer steel, phys. and elec. prop. 

of, 135. 
Biased bells, use of, 1103. 
Bipolar dynamos, armature wind- 
ings for, 345. 
Birmingham wire gauge, 141. 
Bismuth, phys. and elec. prop, of, 
135. 

spec. res. of, 132. 

temperature coef. of, 133. 
Bituminous coal, properties of, 1351. 
Blacksmith shop machinery, power 
to run, 1519. 

tools, power required for, 1522. 
Blake transmitters, 1072. 
Bleaching process, 1244. 
Block signalling, automatic, 622. 

system, distributed signal, 627. 

Blondel oscillograph, des. of, t ?, *-54 

Blowers, effect of temperature of 

air on load of, 1346. 

for forced draught, 1344. 

Board of Trade, boiler rules of, 1332. 

regulations, 781. 
Boat cranes, navy spec, for, 1194. 
Bodies of cars, weight of, 734. 
Body of car, preparation of, 745. 
Boiler feed water, 1362. 

purification by boiling of, 1365. 

flues, collapsing pressure of, 1429. 

head stays, 1333. 

plate, ductility of, 1333. 



Boiler rules, U. S. statutes, 1332. 
settings, 1334. 
dimensions of, 1336. 
shell, strength of riveted, 1330. 
shop machinery, power to run, 

1519. 
strength of riveted shells of, 

1330. 
test codes, 1384-1392. 
tests, A.S.M.E. code, 1384. 
tools, power required for, 

1522. 
tubes, charcoal iron, sizes of, 
1428. 
collapsing pressure of, 1429 
Boilers, steam, 1327. 
heating surface of, 1328. 
horse-power of, 1327. 
points in selecting, 1327. 
safe working pressure for, 1330 . 
types of, 1327. 
working pressure of, 1330. 
Boker & Co.'s wire, properties of, 

202. 
Bolt and nut machinery, power 

required for, 1522. 
Bolts, strength of, 1431. 
Bonded joints and rails, rel. value 
of, 780. 
rails, electrolytic action on, 855. 
Bonding car tracks, 771. 
condition of track, 800. 
third rail, 778. 
Bonds, efficiency of, 781 . 
requirements for, 775. 
resistance of, 776. 
testing rail, 801. 
tests of, 773. 
types of, 772. 
Booster calculations for railways, 
810. 
characteristics of, 813. 
comparison, 897. 
controlling discharge by, 889. 
D.C. type, 435. 
definition of, 50 * 
diagram, 810. 
for street railways, 807. 
shunt and automatic types of, 
892. 



1538 



INDEX. 



Booster system, constant current, 
diagram of, 901. 

temperature rise in, 814. 
Boring machines, power required 

by, 1520. 
Boston Edison Co., conduit constr., 

cuts of, 309-313. 
Boulenge* chronograph, 1128. 
Box poles, 632. 
Braces, boiler head, 1334. 

diagonal, 1334. 

direct, 1334. 
Bracket construction, 644. 
Brackets for trolley lines, 635. 
Brake controllers, list of, 755. 
Brakes failing to operate, 805. 
Braking of cars, emergency, 731. 
Branch terminal telephone system, 

1093. 
Branding irons, electric, 1270. 
Brass, rolled, composition of, 1323. 

weight of sheet and bar, 1323. 
Brazing by Voltex process, 1274. 
Break-down point test of synchron- 
ous motors, 399. 

-down tests for high voltages, 233. 

in armature lead, test for, 402. 
Breaking load of beams, 1309. 
Breaks in cables, location of, 327. 
Breast water-wheels, 1476. 
Brick chimneys, cost of, 1343 

foundations, 1292. 

manholes, cost of, 303. 

stone, mortars, crushing load of, 
1322. 

work, 1321. 
Bricks, number in wall, 1321. 

sizes of, 1321. 

weight and bulk of, 1322. 
Bridge, Carey-Foster, 58. 

connection, multiple unit system, 
765. 

for supporting trolley, 648. 

method, meas. cap. by, 64. 
meas. mutual ind. by, 68. 

slide-wire, 58. 

Wheatstone, 31. 
Bridging party lines, 1111. 

telephone system, 1076, 1093. 
Brill cars, dimensions of. 737. 



Brilliancy, intensity of, 599. 
Bristol recording meters, 1036. 
British standard candle, 530. 

thermal unit, 3, 1511. 
Brooklyn bridge, electrolytic action 

on, 858. 
Brooks Potentiometer, 49. 
Brown & Sharpe wire gauge, 141. 

wire gauge, law of, 142. 
Brown rail bond tester, 802. 
Brush contact, friction of, 362. 
resistance loss, meas. of, 509. 
discharge from wires, 235. 
faces, area of, 361. 
drop in volts at, 362. 
losses at, 362. 
friction, 384. 

meas. of, 50 . 
machine, ext. characteristic curve 
of, 337. 
Brushes, angular dist. between, 
table of, 344. 
armature, 351. 

carbon and copper, res. of, 362. 
current densities for materials for, 

442. 
forward lead of, 350. 
motor, position of, 353. 
B.T.U., gas and elec., ratio between, 

1261. 
Bucking of cars, 806. 
Buckling of battery plates, 881 . 
Buildings, design of power station, 
866. 
electrolysis in steel frame, 859. 
Bunsen cell, 14. 

photometer, 535. 
Burglar alarm mats, wiring of, 295. 
Burnley dry cell, 18. 
Burton electric forge, 1274. 
Bus bars, arrangement of, 933. 
copper for, 910. 
data on, 911. 
design of, 933. 
high-tension station, 933. 
structure of, 935. 
Bushel, 1499. 
Busy test, 1091. 
Button transmitters, 1074. 
Buzzer, field. 1140- 



INDEX. 



1539 



<«it»i not shop, power required tor, 

1520 
Cable connectors, Seeley's type, 190. 
ends, bells for, 333. 

insulating, 322. 
flexible dynamo, table of, 172. 
heads, 320. 

joints, Dossert type, 191. 
loss of power in lead sheath of, 

293. 
machinery, depreciation of, 770. 
three cond. white core ins., table 

of, 170 
Cables, break-down of insulation of, 

980. 
breaks in, location of, 327. 
capacity of lead sheathed, 251. 
conductivity of, meas. of, 330. 
current carrying capacity of, 208. 
dielectric tests of, 332. 
distributing, 1083. 
drawing in underground, 319. 
faults in, location of, 328. 
for car wiring, prop, of, 173. 
high-tension, insulation of. 939. 
G. E. rubber ins., tables of, 164- 

172. 
gutta-percha insulated, 232. 
in ducts, heating of, 210. 
ins. res. of, tests of, 321. 
joints in paper insulated, 191. 
lead covered, carrying cap. of, 213. 
locating crosses in, 327. 
paper and lead cov., tables of, 

174-178. 
paper insulated, properties of, 

1083. 
rubber covered, 161. 
rubber insulated, carrying cap. of, 

210. 
rubber insulated, joints in, 190. 
submarine, 189. 

testing of, 331. 
telegraph, 189. 
telephone, 188, 1082. 

capacity of, 1085. 

expenses of, 1087. 

size of, 1086. 
testing cap. of, 325. 

joints of, 323. 



Cables, three-phase, power carrying 
cap. of, 216 
twisted pair. 1082. 
types of underground 320. 
underground and submarine, tests 

of. 321. 
varnished cambric ins , tables of. 

178a- 187a. 
varnished cambric ins , triple 

cond., 185. 
watts lost in. 210. 
Cadmium cell, Weston. 19. 
phys. and elec. prop, of, 135. 
test of battery plates, 878. 
Calcium carbide, production of. 

1245. 
Calcspar, spec. ind. cap. of, 36. 
Calculation of A.C. lines, 279. 
of dynamo efficiencies, 391. 
of transmission lines, 264. 
Calibrating jacks, 941. 
Calibration data for Westinghouse 
wattmeter. 1016. 
of A.C. instruments, 26-28. 
of wattmeters, checking of, 1014. 
Calico printing machinery, power 

to run, 1525. 
Call bells, wiring of, 293. 

U. S. Navy spec, for, 1211. 
Calling apparatus, 1075. 
Calorie, 3, 1511. 

Calorimeter, directions for use of, 
1395. 
separating. 1398. 
throttling, 1394. 
diagram of, 1399. 
Cambric ins. cables, D.C., tables of, 

178a- 187a. 
Canals, constr. of, 868. 
Candle-foot, 525. 

-hours, variation in, 546. 
-meter, 525. 
Candle-power, meas. of, 584. 
Navy spec, for, 1171. 
of arc lamps, 579. 
of coal gas. 1450. 
of lamps, 544. 
of searchlights, 1127. 
standard of, 52 . 
Candy manufacture, elec. in, 1270. 



1540 



INDEX. 



Canning industry, electric heat in, 

1270. 
Caoutchouc, spec. ind. cap. of, 36, 
Capacitance of transmission circuits, 

249. 
Capacity and inductance, neutrali- 
zation of, 292. 
curves of railway motors, 676. 
definition of, 5. 
distorting effect of, 1079. 
effect of line, 264, 
electrostatic, measurement of, 40. 
Gott method, 326 
Kelvin method, 326. 
loss of storage batteries, 881. 
measurement of, 63. 
meas. coef . of induction by, 65. 
measures of, 1499. 
of A.C. circuits, 259. 

effect of, 1216. 
of battery for given discharge, 900. 
of cables, direct discharge method, 
325 

Gott's method, 326. 

meas. of, 324. 

Thomson's method, 325. 
of gases, spec, inductive, 35, 
of liquids, spec, ind., table of, 37. 
of railway motors, 673. 
of solids, spec, ind., table of, 36, 

37. 
of storage batteries, 874, 883- 
of telephone cables, 1085. 
of transformers, choice of, 458. 

table of, 498. 
of transmission circuits, 248. 
of various overhead transmission 

lines, 250. 
per 1000 feet of aerial wires, table 

of, 252. 
reactance, 259, 
reactance of transmission circuits, 

248. 
spec, ind., measurement of, 38. 
susceptance of transmission cir- 
cuits, 249. 
susceptance, table of, 269. 
symbol of, 8. 
tests for locating breaks in cables, 

327 



Capacity tests with Lord Kelvin'* 
dead-beat voltmeter, 326. 
unit of, 4 
Carcel lamp, 530. 
Car bodies, weight of, 734 
body, preparation of, 745. 
controllers, 753- 
energy consumption per, 652. 

input to, 657 
equipments, 613, 752, 
heaters, cross seat type, 1268. 
hints to purchasers of, 1269. 
truss plank type, 1267. 
heating, cost of, 1266. 

electric, 770, 1265. 
lighting, G. E. railway system, 

851. 
motors, installation of, 745. 

test of, 392. 
tests, interurban, 722. 
wiring, 746. 

for heaters, diagram of, 1267. 
special cables for, prop, of, 173. 
Westinghouse railway system, 

846. 
Carbide furnace, King, 1245. 
Carbon brushes, current density for, 
442. 
res. of, 362. 
use of, 351 
Carbon dioxide, spec. ind. cap. of, 35. 
disulphide, spec. ind. cap. of, 35. 
dust, 578. 

effect on steel of, 826. 
monoxide, spec ind. cap, of, 35. 
spec. res. of, 132. 
Carbons for enclosed arc lamps, 
578. 
for search lights, 579, 1125. 
resistance of, 577. 
sizes of, 578. 
test of arc light, 577. 
Carborundum, production of, 1245. 
Care of storage batteries, 1228. 
Carey-Foster method, meas. res. by, 

58. 
Carhart-Clark cell, des. of, 19. 
Carpenter's hrottling calorimeter 
1395. 
curves. 139^, 



INDEX. 



1541 



Carpenter's throttling Calorimeter, 

directions for use, 1395. 
Carrying capacity of armature con- 
ductors, 375. 

of fuses, 1275. 

galv. iron wire, 34. 

of lead covered cables, 213. 

of rubber ins. cables, 210. 

of wires, 208. 
Cars, bucking of, 806. 

depreciation of, 770. 

dimensions of electric, table of, 
732. 

emergency braking of , 731. 

energy required for, 679 . 

lighting of, 806. 

power required for, 656. 

speed and energy curves for, 680. 
Cartridge fuses, 1276. 
Carty bridging bell, 1102. 
Cascade, cap. of condensers in, 324. 
Cast iron magnet shoes, 352. 

permeability of, 89. 

phys. and elec. prop, of, 137. 

test of, 1294. 

water main, electrolytic action on, 
854. 
Castner metallic sodium cell, 1242. 

process, caustic soda by, 1240. 
Castor oil, spec. ind. cap. of, 37. 
Cast steel, permeability of, 89. 

rope, wire, 1325. 
Catenary trolley, bridge for, 648. 

construction, 639. 

material for, 643. 
Cathode, definition of, 1229. 

rays, theory of, 1248. 
Caustic soda, production of, 1239. 
Cell, Burnley type, 18. 

Carhart-Clark type, 19. 

chloride of silver type, 16. 

Edison-Lalande, des. of, 17. 

Fuller, description of, 16. 

Gasner type, 18 

grouping, efficiency of, 21. 

Leclanche*, des. of, 16. 

standard, construction of, 11. 
description of, 19. 
spec, for, 10. 

Weston cadmium type, 19. 



Cells, Clark type, 19. 

closed circuit, table of, 14. 
grouping of, 19. 
open circuit, 15. 
Celluvert, spec. ind. cap. of, 36. 
Cement, adhesion to bricks of, 1294. 
and sand, fineness of, 1294. 
crushing load of, 1322. 
hydraulic, strength of, 1294. 
mortar, 1293. 
Portland, strength of, 1294. 

wt. of, 1293. 
Rosendale, wt. of, 1293. 
strength of neat, 1294. 
Centering of armature, 403. 
Center of gravity of distribution 
system, 277. 
pole line construction, 631. 
Centi-ampere meter, balance used 

as, 43. 
Centigrade vs. Fahrenheit scale, 

1508. 
Centimeter, definition of, 2. 
Central battery system, 1096. 
energy system, 1096. 
office apparatus, 1104. 
offices, adv. of one vs. several, 

1094. 
R.R. of N.J. shops, power to run 

tools in, 1520. 
station battery connections, 899. 
electrically operated switch- 
board, 928. 
lightning arresters in, 983. 
switchboard panels, 907. 
three wire battery system, 903, 
vs. isolated plant, 1286. 
telephone office, 1089. 
Centrifugal tension in Manila ropes, 

1491. 
C.G.S. units, 2. 
names of, 6. 
Chain, 1496. 
coil, 1496. 
proof, 1496. 
short link, 1496. 
weight of, 1496. 
Characteristic curve, external 
dynamo, 337. 
of dynamo, plotting of, 382. 



1542 



INDEX, 



Characteristic curve of N.Y.C. loco- 
motive, 742. 
of railway motor, 664. 
curves of over-compounded 

dynamo, 340. 
of solenoids, 129. 
Characteristics of electromagnets, 
129. 
of G.E. single-phase motor, 713c 
of railway booster, 813. 
of railway motors, 685. 
of transformers, 483. 
of two-path armature winding, 

348. 
of Westinghouse single-phase 
motor, 715. 
Charcoal rope, wire, 1325. 
Charge curves, storage battery, 876, 
of storage battery, loss of, 884. 
rate for batteries, 883. 
Charging batteries, 482. 

batteries, connections for, 899. 
current of line wave, 249. 

per 1000 feet of aerial circuit, 
253. 
of storage batteries, 880. . 
Chart for calculating A.C. lines, 282. 
of parabolic curves in wire spans, 
218. 
Chase-Shawmut fuse wire, 1275 
Chatterton's compound, specifica- 
tions for, 194. 
Checking preliminary dynamo di- 
mensions, 363. 
wattmeters, 72. 
Chemical action in cells, 14. 
equivalent of elements, 1230. 
properties of rubber, 229. 
qualities of steel for third rail, 822. 
Chimney construction, 1339. 

weight for burning given amounts 

of coal, 1342. 
protection, 1281. 
rate of combustion due to height 

of, 1342, 

tables, 1338. 

Chimneys, 1338. 

dimensions and cost of, 1343. 

draught power of, 1338. 

iron, dimensions and cost of, 1344. 



Chimneys, necessary height of, 1342 
radial brick, 1341. 
and bond, 1340, 
size of, 1338. 

steel, foundations for, 1343. 
lining for, 1343. 
plate, 1343, 
Chloride of silver cell, 16. 
Chlorine in electrolyte, test for, 878 
Choke coils, mountingof, 984. 
S.K.C. arrester, 991. 
use of, 994. 
Choking effect of inductance, 1079. 
Chord of polar arc, values of, 371. 
of pole face, dimensions of, 363. 
Chrome-bronze, phys. and elec. prop 
of, 135. 
-steel, phys. and elec. prop, of, 135. 
Chronographs, types of, 1128. 
Chronoscope, Schultz, 1130. 
Circuit breaker, def . of, 52 
design, 952. 
Westinghouse oil, 969. 
Circuit breakers, capacity of, 955. 
for booster protection, 952. 
for motors, capacity of, 955. 
for protection of transmission 

line, 951 c 
for railways, use of, 789. 
for storage battery protection, 

952. 
grouping of, 929. 
leads for, 975. 
mounting of, 912. 
oil, arrangement of, 935. 
polyphase motors protected by, 

954. 
rating of, 50 , 912. 
specifications for, 947 
table of, 949. 
Circuit closer, torpedo, 1139. 
trunks, operation of, 1095. 
Circuits in buildings, ins. res. of, 85. 
laws of electrical, 55 
multiple, res. of, 55. 
testing drop in railway, 804. 
tests of street railway, 798. 
Circulating pumps, 1445. 
Cities, electrical distribution in, 261. 
mill power in various, 1462. 



INDEX. 



1543 



Clark cell, description of, 19. 
E.M.F of, 5. 
method, comparison of E.M.F. by, 
77. 
testing joints of cables by, 323. 
Clay conduits, constr. of, 301. 

foundations on, 1290. 
Clearing-out drops 1090. 
Closed cars, weight of, 734. 
circuit cells, table of, 14. 
Coal, American, heating value of, 
1350 
and electric heating compared, 

1265. 
anthracite, sizing tests of, 1354. 
approximate analysis of, 1352. 
consumed by isolated plant, 1286. 
gas, analysis of, 1510. 
candle power of, 1450. 
spec. ind. cap. of, 35. 
heating value of, 1349. 
power, data on, 869. 
space to store, 1353. 
value of in weight of woods, 1349. 
weight per cubic foot of, 1353. 
Coals, relative value and how to 

burn, 1355. 
Coast-defense board, recomm. of, 
1123. 
guns, manipulation of, 1134. 
Coasting, formula for, 668. 

line, location of, 668. 
Cocoa and coffee dryers, electric, 

1270. 
Codes, telegraph, 1052. 
Coefficient of induction, meas. of, 65, 
of induction, symbol of, 8. 
of self-induction, 64. 
def . of, 238, 
formula for, 405 
of temperature of metals, 133. 
Coefficients of expansion of solids. 
1508. 
of magnetic eakage, 376. 
of reflections, 593. 
Coercive force, def, of, 108. 
Coffee and cocoa dryers, electric, 

1270. 
Coherer, 1058. 
receivers, 1064. 



Coherers, mercury auto, 1066. 
Coil chain, 1496. 

slots, design of armature, 358. 

trial armature, 373. 
surface of field magnets, 352 
Coils, armature, placing of, 358. 
for transformers, 444 
heating of, 127. 
values for number of armature, 

373. 
winding of, 112. 
Coke, analysis of, 1353. 
space required for, 1353. 
weight per bushel of, 1353. 
Collier & Sons' factory, heating 

devices in, 1270. 
Columns, comparison of water, 1463, 
hollow, 1305. 

cylindrical, 1306. 
pillars or struts, 1300. 
solid cast iron, 1305. 
strength of white pine, 1319. 

solid cast iron, 1305. 
tests of cast iron, 1306. 
ultimate strength of, 1306. 
wrought iron, ult. strength of, 
1307. 
Colza oil, spec ind. cap. of, 37. 
Combinations of railway motors, 

760. 
Combined volt and ammeter method, 

meas. A.C. power by, 71. 
Combustibles, properties of, table of, 

1348. 
Combustion, draught necessary for, 

1342, 
Commercial efficiency curve for are 
dynamo, 338. 
efficiency curve for motors, 370. 

of dynamos, def. of, 383. 
lights, burning of, 611. 
rating of railway motors, 675. 
transformers, 445. 
Committee on Notation, table by, 6. 
Common battery system, 1096, 1115. 
signaling battery system, 1115. 
trunks, 1096. 
Commutated rotor windings, 429. 
Commutating machines, def. of, 504. 
zone, 350. 



1544 



INDEX. 



Commutation in dynamos, 364. 
Commutator bars, number of, 361. 

brushes, sparking at, 805. 

brush friction, meas. of, 509. 

diam. of, 361. 

rise of temperature of, 362. 

segments, number of, 361. 

type, D.C. meters, 997. 
Commutators, construction of, 351. 
Comparative cost of gas and elec. 
cooking, 1260. 

expense of operating transformers, 
458. 

values of lighting methods, 594. 
Comparison of copper and aluminum 
wire, 195. 

of interurban car tests, 724. 
Compensated A.C. motor character- 
istics, 713. 

revolving field alternators, 409. 
Compensation for power factor, 
1002. 

method, E.M.F. of batteries, 62. 
Compensator regulators, definition of, 
503. 

use of starting, 918. 
Compensators, construction of, 463. 

for induction motors, 429. 
Composite electric balance, 43. 
Compound cables, design of, 331. 

dynamos, characteristic of, 340. 
des. of, 336. 
regulation tests of, 382. 

engines, cylinder ratios for, 1441. 
Compressive strength of woods, 1317. 
Concealed lighting system, 601. 
Concentric cable, capacity of, 251. 
Concrete foundations, 1292. 

manholes, cost of, 303. 

reinforced, 1292. 

sub-foundations, 1292. 
Condensation in steam pipes, 1415. 

in steam pipes aboard ship, 1415. 
Condenser capacities, ejector, 1445. 

current, curve of, 1219. 

diagr. of connections of, 39. 

method, res. of batteries by, 60. 

unit, 5. 
Condensers and pumps, 1443. 

construction of, 38. 



Condensers, cooling water by, 1444. 
design of, 35. 
in cascade, cap. of, 324. 
in parallel, 63. 
cap. of, 324. 
in series, 63. 

cap. of, 324. 
losses in, meas. of, 513. 
Condensing engines, number of 

expansions in, 1441. 
Conductance, definition of, 9, 55. 
of multiple circuits, 55. 
symbol of, 8. 
Conducting power of sulphuric acid, 

table of, 905. 
Conductivity, definition of, 9. 

Matthiessen's stand, of, table of, 

132. 
millivoltmeter meas. of, 87. 
Northrup method of, meas., 60. 
of cables, meas. of, 330. 
of conductors, table of, 132. 
of copper, 518, 910. 
of dielectrics, specific thermal 

234. 
percentage, form, for, 132. 
relative, 132. 
specific, 132. 
symbol of, 8. 
Conductor rail, Potter type, 830. 
Conductors, carrying cap. of arma- 
ture, 375. 
dimensions of, 260. 
economical tapering of, 279. 
for electric railways, overhead, 

785. 
for high-tension, insulation of, 

939. 
for high-tension transmission, 235. 
for parallel D C. system, size of, 

284. 
for railways, dimensions of, 791. 
installing, U. S. Navy, spec, for, 

1170. 
isolation of, 936 
per K. W. del'd, curves showing 

weight of copper, 283. 
res. of, 61. 

rotation around pole of, 109. 
spec. res. of, table of, 132. 



INDEX. 



1545 



Conduit, Board of Trade regulations 
for, 783. 
construction, U. S. Navy, 1170. 
cost of estimating, 317. 
itemized, 316. 
total, 307 
def. of, 301. 

foot, cost per manhole of, 304< 
cost per, table of, 306. 
in cities, cost per, table of, 
307 
laying of, 301. 

multiple duct, constr. of. 301. 
New Orleans, 308. 
systems, heat dissipation in, 214. 

railway, 835. 
work, usual practice of, 302. 
Conduits, Chicago, underground, 
cost of, 317. 
cost of, 302. 

monolithic, des. of, 301. 
multiple, adv. of, 301. 
single duct, adv. of, 301. 
Connecting transformers to rotary 

converters, 476. 
Connection of batteries, 19. 
Connections of polyphase meters, 
checking of, 1026. 
of transformers, 297, 472. 
on switchboards, 910. 
Connectors, Seeley's cable, 190. 
Consolidated car heating, wiring 

diag. of, 1267. 
Constant current booster system, 
diagram of, 901. 
current from constant potential 

transformers, 464. 
current machines, regulation of, 

513. 
current transformer panels, equip. 

of, 922. 
current transformers, G. E. type, 

464. 
galvanometer, 23. 
hysteresis, wattmeter test for, 102, 
potential arc lamp, 574. 

machines, regulation of, 513 
secondary current, transformers 
for, 462. 
Constantin wire, properties of, 202. 



Constants for barrel armature wind- 
ing, 376. 

hysteretic, table of, 99. 

of meters, values of, 1029. 
Construction of chimneys, 1339. 

of manholes, cuts of, 309. 

power station, chart of, 1289. 

tools, electric work, 1530. 
Consumption of energy of cars, 652. 

of energy of elec. heaters, 1265, 
Contact buttons, Westinghouse 
railway system, 844. 

plates, Westinghouse railway 
system, 841. 
Contactors, multiple unit system, 762. 
Continental code, 1052. 
Control of lights from two or more 
points, 294. 

of motors, Ward Leonard's sys- 
tem, 354. 

of water-tight doors, 1198. 
Controller, care of, 747. 

combination, 760. 

for oil circuit breaker, 975. 

series-parallel, 753. 
Controllers, dimensions of, 757. 

G.E. railway system, 851. 

installation of, 746. 
Controlling desks, 941. 

discharge, methods of, 888. 

panels, Navy spec, for, 1185. 

pedestal, 940. 

switchboards, 940. 
Convectors and radiators, 1263. 
Converter armature windings, 441. 

definition of, 503. 

panels, three-phase rotary, equip, 
of, 919. 
Converters connected to transform- 
ers, 477, 

rotary type, 436. 
Conveyors, ammunition, U. S. 

Navy, 1193. 
Cooking apparatus, electric, effi- 
ciency of, 1260 

electric, cost of, 1259. 

gas and elec. compared, 1260. 

record, daily electric, 1262. 

utensils, electric, cost of operating, 
1261. 



1546 



INDEX. 



Cooling surface of field coils, table 

of, 352. 
tower test, 1447. 
of transformers, 448. 
water for condensers. 1443 
Cooper-Hewitt mercury lamps, 558 
Conductivity, 132. 

Matthiessen's Standard, 132 
Copper, admixture of, effect of, 144. 
and aluminum compared, 195. 
and brass wire and plates, weight 

of, 1324. 
bar data, 911. 
bars on switchboards, 909. 
brushes, current density for, 442. 

res. of, 362; use of, 351. 
conductivity of, 518, 910. 
electric welding of, 1272. 
electrolytic refining of, 1235. 
for A. C. lines, table for calc. of, 

279. 
fusing effect of current on, 217. 
in railway feeders, 791. 
loss in alternator armatures, 407. 

in transformers, 445. 

in transformers, meas. of, 487. 

in transformers, Sumpner's test 
of, 497. 

in transformers, table of, 498. 
melting point of, 143. 
phys. and elec. prop, of, 135. 
plating, 1233. 

res. of cables, meas. of, 330. 
rise in resistance of, 379. 
spec. res. of, 132. 
strands, stand, prop, of, table of, 

159. 
temp, coefficient of, 133, 52 , 
weight of, 143. 

of round bolt, 1323. 
wire and plates, 1324. 

fuses for railway circuits, 731. 

Matthiessen's form, for, 133. 

phys. const, of, 143. 

res. of, table of, 148. 

skin effect factor for, 238. 

solid, G. E. Co., prop, of, table 
of, 162. 

solid, table of, 154. 

stranded, table of, 155. 



Copper wire tables, A.I.E.E , 146. 
tables, explan. of, 145 
tensile strength of, 156. 
weight of, English system, table 

of, 157. 
weight of, metric system, table 
of, 158. 
Core disks for armatures, 356. 
insulation, armature, 341. 
losses, 98. 

in armature, 360. 

in transformers, 445. 

in transformers, comparative, 

455. 
in transformers, curves of, 454, 

456. 
in transformers, meas. of, 485. 
in transformers, table of, 498. 
loss test, 383. 
of stator and rotor, 425. 
of submarine cables, design of, 331 . 
of three-phase- transformers, 470. 
type transformers, coils for, 444. 
Cores, cross-section of, 365. 

field magnet, general data on, 352. 
magnetic densities for transformer, 

447. 
of armatures, data on, 357. 
of American transformers, types 
of, 443. 
Corey telephone system, U. S. Navy, 

1209. 
Corn plaster transmitters, 1074. 
Cos a, values of, 276. 
Cost of aluminum wire, 195. 
of conduit, 302. 

estimating, table of, 317. 
itemized table of, 316. 
total, 307. 
of cooking daily meal by elec, 

weekly record, 1262. 
of duct material in place, table of, 

307. 
of electric car heating, 1266. 
of 5' X 5' X 7' manhole, 316. 
of heating water by electricity, 

1259. 
of incandescent lamps, 556. 
of manhole, estimating, table of, 
317. 



INDEX. 



1547 



Cost of manholes, table of, 302 
of one mile of trolley system, 629. 
of operating electric cooking 
utensils, 1259, 1261. 
electric elevators, 1528. 
elec. heaters, 1265. 
elec. irons, 1263. 
lamps, 554. 
of paving per sq. yd., 305 
of power, curves for reducing, 868. 
of protected third rail, 835. 
of sewer connections, 303, 
of street excavation per conduit 

foot, 306. 
of telephone plant, 1108. 
of tools and supplies for installing 

electric work, 1531. 
per conduit foot for manhole, 304, 
per conduit ft. in cities, table of, 

307 
per conduit foot, table of, 306. 
Costs, comparative, gas and elec. 

cooking, 1260. 
Cotton covered wires, linear space 
occupied by, tables of, 121-126, 
covered wire, diam. of, 163a. 
machinery, power to drive, 1524. 
Coulomb, definition of, 5. 
international, def. of, 9. 
value of, 8. 
Counter cells, use of, 891. 
e.m.f. cells, use of, 891. 
e.m.f. in motor armatures, 353. 
torque, meas. of, 396. 
Cove-lighting, 592. 
Cover for service boxes, 315. 
Covers for manholes, cuts of, 313- 

315. 
Cowles furnace, 1247. 
Crane chain, 1496. 
Cranes, boat, Navy spec, for, 1194. 

power to run electric, 1527. 
Cross connections, use of, 1104. 
seat heaters, wiring diag. of, 1268 . 
section of field core, 365. 
of conductors, calc. of, 277. 
of conductor, formula for, 265. 
-talk, definition of, 1081. 

elimination by transposition of, 
289. 



Crosses in cables, location of, Ayrton 

method, 327 
Crossings of wires, 639 
Crushing loads for brick, stone, 
mortar, cement, 1322. 
strength of woods, 13 16. 
Cubic feet table, water ho p., 1475. 
Current carrying capacity of lead 
covered cables, 213. 
carrying capacity of rubber ins, 

cables, 210 
carrying capacity of wires, 208. 
curve for railway motors, 669. 
definition of, 50^.. 
densities for transformer coil, 447, 
for various brush materials, 
442. 
density at brush faces, 361. 
for brushes, 351. 
for commutator segments, 361 . 
distribution by railway conduc- 
tors, 791. 
in cables, max. allowable, 212- 
in multiple circuits, 55, 
in three-phase circuit, meas. of, 

406. 
maximum, A. C. windings, 127. 
mean, A. C. windings, 127. 
measurement of, 41. 
millivoltmeter meas. of, 78. 
of alternators, 405. 
potentiometer meas. of, 47, 63. 
swapping, 859. 
taken by induction motors, 297. 

by lamps, 542. 
transformers, descr. of, 945. 
unit of, 4. 
. variations on water main, 857. 
voltmeter meas. of, 77. 
wave form of, "<C, 1218. 
Currents, fusing effects of, 217. 
Curtis steam turbine, 1455. 
Curvature of rails, 616. 
Curve drawing meter, G. E., 1036 
dynamo magnetization, 336. 
magnetic distribution, 340. 
tracer, Rosa type, * -. 
Curves, altern. current power. 70. 
railway, 612. 

formula for, 665. 



1548 



INDEX. 



Curves, trolley wire, 638, 

voltage of storage batteries, 883. 
Cut-outs, slate, res. betw. terminals 

of, 86. 
Cyanide of potassium, production of, 
1246. 

of sodium, production of, 1246. 
Cycle, def. of, 501. 
Cycles, measurement of, 50-54. 
Cylinder ratios, compound engines, 

1441. 
Daily electric cooking record, 1262. 
Damping of oscillator, 1059. 
D.andW. fuses, 1276. 
Daniell cell, 14. 
D' Arson val galvanometer, 21. 

galvanometer, des. of, 25. 
ill. of, 25. 
Data for transformer tests, 495. 
Davy cell, 14. 
Decade resistance box, 32. 
Decane, spec. ind. cap. of, 37. 
Deceleration, formula of, 668. 
Deck beams, 1314. 

winches, 1196. 
Decylene, spec. ind. cap. of, 37. 
Defensive mines, 1137. 
Definite time limit relays, 956. 
Definition of symbols, dynamo 

section, 334. 
Deflection of beams, 1309. 
Deflections of aluminum wire in 

still air, 226. 
De Laval steam turbine, 1452. 
Delta connected armature winding, 
413. 

connection of transformers, 473, 
478. 
of winding, 404. 
Demand factor, 505. 

meter, Wright, 1008. 
Density of field magnet cores, mag- 
netic, 365. 

of armature teeth, 367. 

of electrolyte, 877, 884. 

of pole faces, magnetic calc. of, 356. 
Depolarizer, def. of, 14. 
Deposit, rate of, 1235. 
Depreciation of isolated plant, 1285. 

of telephone plant, 1108. 



Depreciation of street railways, tabk 

of, 770. 
Depth of armature coil slots, 373. 
Derived geometric units, 2. 

mechanical units, 2. 

units, symbols of, 1. 
Design of circuit breakers, 952. 

of transformers, 447. 
Designing dynamos, 370. 

of dynamos, principles of, 355. 
Destructive effect of electrolysis 

854. 
Detectors, electrolytic, 1067. 

hot-filament, 1068. 

low resistance, 1065. 

shunted, 1065. 

magnetic, 1067. 
Deterioration of underground metals, 

852. 
Determination of moisture in steam, 
1394. 

of wave form, 49. 
Diagram of car heating wiring, 1267. 

of car wiring, 747. 

of cells in multiple, 20. 

of train performance, 663. 
Diameter of commutator, 361. 
Dielectric strength of air, 233. 

strength of insulating materials. 
228. 

strength, test of, 515. 

tests of cables, 332. 
Dielectrics, properties of, 227. 

puncturing voltages for, 228. 

specific inductive capacity of, 227. 
thermal conductivity of, 234. 

variation of resistance of, 228. 
Difference of elevation, potential 
strains due to, 981. 

of potential, meas. of, 75. 
symbol of, 8. 
unit of, 4. 
Differential ammeter, use of, 903. 

galv. method, res. meas. by, 56. 

gear, turret turning system, 1190. 
Diffused lighting system, 602, 
Diffuse reflection, coef. of, 596. 
Diffusion of light, 599. 
Dilute sulphuric acid, conducting 
power of, table of, 905. 



INDEX. 



1549 



Dilute sulphuric acid, resistance of, 
1229. 
strength of, table of, 904 
Dimensions of conductors, 26p. 
of controllers, 757. 
of dynamos, preliminary, check- 
ing of, 363. 
of electric cars, table of, 732. 
of physical quantities, 6. 
of railway conductors, 791. 
of storage battery, 883, 
Dip in span wire, 634. 
Direct-connected generating sets, 
standards, 1435. 
control panel switchboard, 906. 
current arc lamps, 568. 

circuit breakers, design of, 952. 
circuits for operating oil 

switches, etc., 939. 
distribution, pressure for, 260. 
distribution, size of conduc- 
tors for, 284. 
dynamos, Hopkinson's test of, 

393. 
exciter switchboard, 942. 
feeder panel, equipment of , 928. 
generator panels, equipment of, 

924. 
meters, testing of, 1020. 
motor panel, equipment of, 928. 
motors, counter e.m.f. in, 353. 
over voltage relay, 960. 
reverse current circuit breaker, 

950. 
rotary, converter panel for, 925. 
system, examples of, 271. 
use of in U. S., 870. 
deflection method, ins. res. by, 

321. 
discharge method, meas. cap. by, 

63, 325. 
reading ohmmeter, 57. 

potentiometer method, E.M.F., 
of batteries, 63. 
Discharge, chemical effect of electric, 
1232. 
curves, storage battery, 875. 
methods of controlling, 888. 
points for lightning rods, 1282. 
rate of storage batteries, 874, 883. 



Dischargers, static, 992. 
Discharges, atmospheric, 1278. 
Disconnecting switches, 965. 
arrangement of, 933. 
between bus bars, 929. 
Discount meter, Wright, 1008. 
Disinfecting sewage, 1244. 
Disks, armature core, constr. of, 34 . 

armature core, data on, 356. 
Disk type armatures, 341. 
Disruptive strength cf transformer 

insulation, 483. 
Distance-time curve, 668. 
Distributed coil form of winding, 
410. 
signal block system, 627. 
Distributing cables, 1083. 

frames, 1104. 
Distribution curves, 540. 
light, 599. 
system, parallel, 277. 

for single-phase railway, 718. 
systems in general, 262. 
Distributive shunt telephone sys- 
tem, 1107. 
Ditches, constr. of, 868. 

flumes and, 1468. 
Diversity factor, 505. 
Divided bar method, determ. magn. 

values by, 92. 
Diving-lanterns, 1179. 
Domestic illumination, 596. 
Dossert joint, 191, 910. 
Double bridge, ^Kelvin type, 59. 
current generator, def. of, 502. 

use of, 440. 
galv. iron telegraph wire, proper- 
ties of, 200. 
square roots, table of, 45, 46. 
track pole construction, 631. 
truck cars, power for, 656. 
Draft power for comb, of fuels, 1342 
Drag on armature conductors, 351. 
Draw-bar pull, test of, 803. 
Drawing in underground cables, 319. 
Drill presses, power required for, 

1521. 
Driver-Harris wire, properties of, 
202. 
resistance of, 207. 



1550 



INDEX. 



Drop at end of line, test of, 800. 
in A.C. lines in per cent, 280. 
in candle-power of lamps, 544. 
in overhead lines, 798. 

returns, 798. 
in pressure in parallel distribution 

system, 279. 
in railway circuits, test of, 804. 
feeders, 791. 
line, 794. 
in secondary of transformers, 

test of, 483. 
in voltage at brush faces, 362. 
at train, 795. 
in railway circuit, 796. 
in storage cells, table of, 879. 
max., U. S. Navy spec, for, 1171. 
Drum armatures, 341. 

windings of armature, 345. 
Dry batteries, description of, 18. 
cell, Burnley type, 18. 

chloride of silver type, 16. 
Gasner type, 18. 
measure, metrical equivalents, 
1502. 
Drysdale's permeameter, 97. 
Duct, def. of, 301. 

material in place, cost of, table of, 
307. 
Ductility of boiler plate, 1333. 
Ducts, arrangement of, cuts of, 
310. 
heat dissipation in, 214. 
in manhole, grouping of, 318. 
Duddell oscillograph, 52. 
Dumb-bell oscillator, 1056. 

discharge of, 1060. 
Duncan meters, 998. 

method, meas. of wave form by, 

recording wattmeters, testing of, 
1031. 
Duplex loop system, 1047. 

repeater, 1049. 

telegraphy, 1044. 

telephony, 1106. 
Durability of railroad ties, 619. 
Dust of carbons, 578. 
Dynamo cable, flexible, table of, 172. 

design, principles of, 355. 



Dynamo cable, dimensions, pre- 
liminary, checking of, 363. 

efficiencies, average, table of, 377. 

efficiency, U. S. Navy, 1158. 

regulation, test for, 382. 

room distribution, U. S. Navy, 
diagram of, 1165. 

room, U. S. Navy, 1153. 
Dynamometer, Siemens' electro-, 42. 
Dynamos and motors, principles of. 
336. 

and motors, tests of, 378. 

classification of, 336. 

design of, 370. 

efficiency tests of, 383. 

E.M.F. of, meas. of, 74. 

in ships, gyrostatic action on, 353. 

insulation of, meas. of, 86. 

resistance of, workshop method, 
61. 

temperature rise in, 378. 

U. S. Navy, spec, for, 1156. 
Dynamotors, definition of, 50" 

description of, 434. 
Dyne, definition of, 3. 

JEartli connections, 782. 
currents, effect of, 1081. 
foundations on, 1291. 
Ebonite, spec. ind. cap. of, 36, 227. 
Economical tapering of conductors, 

279. 
Economizers, fuel, 1378. 
Economy coils, construction of, 463. 
of isolated electric plants, 1283. 
of superheated steam, 1414. 
Eddy current core loss tests, 385. 
factors, table of, 106. 
loss, formula for, 99. 
loss, meas. of, 104, 50i,. 
currents in armatures, prevention 

of, 350. 
currents in iron cores, 99. 
Edison-Lalande cell, des. of, 17. 
-Lalande cell, illustration of, 18. 
storage batteries, 1227. 
three wire system, 355. 
Effective E.M.F. of A.C. current, 
404. 
resistance of A.C. circuits, 236. 



INDEX. 



1551 



Effect of line capacity, 264. 
Efficiencies, average dynamo, table 

of, 377. 
Efficiency curve of motors, 370. 
curve of arc dynamo, commercial, 

338. 
curve of arc'dynamo/electrical, 338. 
curves of railway motors, 686. 
def . of, 507. 

generator, U. S. Navy, 1158. 
of arc lights, 580. 
of bonds, 781. 
of cell groupings, 21. 
of dynamos, 370. 
of dynamos and motors, meas. of, 

508. 
of dynamo, calc. of, 391. 
of elec. cooking apparatus, 1260. 
of gas engine, 1449. 
of lamps, variation in, 547. 
of large and small transformers, 

relative, 459. 
of Moore tube, 566. 
of motors, Navy spec, for, 1185. 
of motors, tests of, 394. 
of railway motors, 663. 
of small pumps, 1368. 
of steam boiler, 1329. 
of steam engines, superheated 

steam, 1414. 
of storage batteries, 879. 
of storage batteries, variation of, 

884. 
of transformers, 453. 
of transformer, test of, 493. 
of various types of steam engines, 

1439. 
tests of dynamos, 383. 

of dynamos and motors, 386. 

of induction motors, 398. 

of railway motors, 803. 

of street railway motors, 397. 

of two d. c. dynamos, Hopkin- 
son's method, 393. 

of two similar dynamos, Kapp's 

method, 387 
Ejector condenser capacities, 1445. 
Elasticity, modulus of, 1302. 
Elastic limit, 1302. 
resilience, 1312. 



Electrical and mechanical units table 

of, 1258. 
circuits, laws of, 55. 
efficiency curve of arc dynamo, 

338. 
efficiency of dynamos, def. of, 383. 
engineering symbols, 1. 

units, 2. 
load test, 395. 
measuring instruments, 21. 
prop, of alloys, table of, 134-140. 

of metals, table of, 134-140. 

of rubber, 229. 
qualities of steel for third rail, 822. 
symbols, 1. 
units, 4. 

international, 9. 
Electrically operated central station 

switchboards, 928. 
Electric and coal heating compared, 

1265. 
and gas cooking compared, 1260. 
and gas rates compared, 1261. 
automobiles, 1224. 
balance, Kelvin type, 43. 
brake controllers, list of, 755. 
car controllers, 753. 

heaters, hints to purchasers of, 
1269. 

heating, 1265. 

heating, cost of, 1266. 

motors, installation of, 745. 
cars, dimensions of, table of, 732. 

speed and energy curves for, 
680. 
circuits, ins. res. of, 85. 
cooking apparatus, efficiency of, 
1260. 

cost of, 1259. 

record, table of, 1262. 

utensils, cost of operating, 1261. 
cranes, power to run, 1527. 
drive, saving by, 1529- 
energy, def. of, 5. 

symbol of, 8. 
elevators, operating cost of, 1528. 

power used in, 1528. 
equipment of one car, 752. 
forge, Burton, 1274. 
furnace, efficiency of, 1244. 



1552 



INDEX. 



Electric fuses for firing guns, 
1134. 
heaters, energy consumption of, 

1265. 
heat in printing plants, 1269-1270. 
heating, 1263. 

classification of, 1256. 
devices in laboratories, 1270. 
industrial, 1269. 
irons, cost of operating, 1263. 
land mine, 1137. 
locomotives, 614. 

table of, 739. 
meters, accuracy of, 997. 
plants, isolated, economy of, 12(S3. 
power, def. of, 5. 

rrieas. by wattmeter method, 72. 
symbol of, 8. 

transmission, system of, 865. 
propulsion, Leonard's system of, 

354. 
quantity, def. of, 5. 
railway booster calculations, 809. 
energy of, 706. 
material required for one mile 

of, 628. 
surface contact system, 840. 
system of operation of, 613. 
third rail system, 821. 
conduit systems of, 835. 
rail welding, 1273. 
smelting, 1247. 
def. of, 1232. 
steering gear, navy spec, for, 

1200. 
welding and forging, 1271. 
of axles, 1272. 
of iron and steel, 1271. 
whistle, navy spec, for, 1210. 
Electrochemical equivalents, 14, 

1230. 
Electrochemistry, scope of, 1231. 
Electrodes, definition of, 1229. 
Electro-dynamometer, 42. 
Electrolysis due to A.C., 860. 
in lower New York, 858. 
near power house, 862. 
remedies for, 861. 
rules for prevention of, 781. 
theory of, 852, 1229. 



Electrolyte, composition of, 877. 
change in, 873 
definition of, 1129. 
density of, 884. 
impurities, effect of, 1238. 
Electrolytic action on bonded rails, 
855. 
action on underground metals, 

852. 
chemical analysis, 1232. 

effects, 1232. 
chemistry, branches of, 1231. 
copper, phys. and elec. prop, of, 

135. 
detectors, 1067. 
effect on water meters, 858. 
interrupters, 1253. 
production of metals, def. of, 

1232. 
refining of copper, 1235. 
of metals, def. of, 1232. 
Electromagnetic induction, 64. 
railway sys tern, 840. 
unit, definition of, 5. 
units, symbols of, 1. 

table of, 7. 
waves, 1055. 
Electromagnet, law of plunger, 127 
Electromagnets, A.C., 127. 
A.C., impedance in, 127. 
calc. of, table of, 114. 
characteristics of, curves of, 129 
exciting power of, 111- 
flux density of, 89. 
heating of, 127. 

magnetization of, table of, 111. 
plunger, shapes of, 128. 
properties of, 108. 
pull of, 110. 
traction of, 110. 
winding of, 112. 
Electrometallurgy, scope of, 1231. 
Electrometer, Mascart, 39. 
quadrant, 40. 
Ryan type, 51. 

testing joints of cables by, 323. 
Electromotive force, definition of, 5. 
formula for generation of, 356. 
for plating, 1234. 
Induced, 64. 



INDEX. 



1553 



Electromotive force, meas. of, 5", 
62. 

of batteries and dynamos, 74. 

symbol of, 7. 

unit of, 4. 
Electroplating, def. of, 1232. 

methods of, 1233. 
Electropoin, use of, 16. 
Electrostatic capacity, meas. of, 40. 

capacity of telephone cables, 1084. 

induction, effect of, 1081. 

units, 1. 

units, definition of, 4. 

in terms. of electromagnetic, 9. 

voltmeter, Kelvin, 40. 
use of, 945. 
Electrothermal chemistry, 1232, 

1244. 
Electrotyping, def. of, 1232. 

methods of, 1232. 
Elementary laws of circuits, 55. 
Elements, atomic weights of, 1230. 

of usual sections, 1303. 
Elevating gear for guns, 1191. 
Elevation, effect on potential of 
lines of, 981. 

of outer rails, 617. 
Elevators, operating cost of electric, 

1528. 
Emergency braking of cars, 731. 
E.M.F., determination of, 49. 

formula for generation of, 356. 

generation of, 336. 

of A.C. current, discussion of, 404. 

of batteries, comparison of, 76. 
meas. of, 62, 74. 

of dynamos, meas. of, 74. 

of standard cells, 19. 
Enameled wire, 187b. 
Enclosed arc carbons, 578. 

arc lamps, 568, 575. 

fuses, 1276. 

motors, navy spec, for, 1183. 
End cell switches, 890. 
Endless chain ammunition hoists, 

U. S. Navy, 1192. 
Energy and speed curve, 680. 

consumption of elec. heaters, 1265 < 
per car, 652. 

dissipation in arm. core, 107. 



Energy and speed curve, electric, 
def. of, 5. 

for electric cars, approx. of, 679. 

input to cars on grades, 657. 

in three-phase circuit, 405. 

kinetic and potential, 3. 

of electric railway, 706. 

units compared with work units, 
12. 
Engine foundation, 1292. 

lathes, power required for, 1516. 

telegraphs, U. S. Navy, 1202. 
Engines, racing of, 981. 

U. S. Navy, specifications for, 
1154. 
Equalizer circuits, remote control 

switches for, 962. 
Equalizing connections, def., 503. 
Equation of steam pipes, 1418. 
Equilucial lines, map of, 592. 
Equipment of one car, 752. 

of electric cars, 613. 
Equivalent, electrochemical, 14. 

sine wave, 501. 

values of elec. and mech. units, 
1258. 
Erection of batteries, 884. 
Erg, definition of, 3. 

value of, 12. 

measurement of, 104. 
Error of meas. in voltmeter tests, 76. 

table for wattmeters, 1032. 
Estimate of water, 869. 
Estimating cost of conduits, table of, 
317. 

cost of manhole, table of, 317. 
Ether, oscillations in, 1278. 
Evaporation, factors of, 1401. 
Evolution of conduit, 301. 
Ewing's hysteresis tester, 102. 
Excavation per conduit foot, cost of, 

306. 
Excessive voltage, evils of, 545. 
Exchange current in transformer, 495. 

systems, automatic, 1105. 

telephone systems, 1088. 
Exciter switchboard, D. C, 942. 
Exciting current in transformer, 483. 
in transformer, meas. of, 485. 
in transformer, table of, 498- 



1554 



INDEX. 



Exciting power of electromagnets, 

111. 
Excitation current in transformer, 
meas. of, 485. 
loss in dynamos, 509. 
of field-magnets, 365. 
of induction motors, 398. 
Exide storage batteries, 1227. 
Expansion, coefficients of, 1508. 

of water, 1362. 
Expense of operating transformers, 

458. 
Expenses of telephone cables, 1087. 
Explosions due to electrolysis, 859. 
Explosives near railways, danger of, 

863. 

Exposure used in transposition, 288. 

Extension bell, connections of, 1076. 

External characteristic curve of 

dynamo, 337. 

characteristic curve of shunt 

dynamo, 339. 
resistance of cells, 20. 
Externally controlled boosters, 894. 
Eye beam foundations, 1293. 
Eyes, effect of light on, 600. 
Factories, power consumption in, 

1517. 
Factors, eddy current, table of, 106, 

hysteresis, table of, 100. 
Factors of evaporation, 1400 and 
1403-a. 
sa»*ety, N. Y. City building codes, 
1302. 
Factory call bell system, 293. 
Fahrenheit vs. Cent, scale. 1508. 
Fall of potential in railway return, 

782. 
Fans, effect of temp, of gases on 
load, 1346. 
for induced draft, 1345. 
ventilation, navy spec, for, 1196. 
Farad, definition of, 5. 
international, def. of, 9. 

standard, 38. 
value of, 8. 
Fatigue of iron and steel, magnetic, 

455. ■ 

Faults in armatures, tests for, 402. 
in cables, location of, 328. 



Faults in cables, Murray's method, 

329. 
in street cars, 805. 
in underground cables, location of, 

331. 
Feeder circuit protection by relays, 

959. 
panel, D.C., equipment of, 928. 

single-phase,.equipment for, 916. 

three-phase, equip, of, 917. 

two-phase, equip, of, 918. 
potential regulator, G. E. type, 

468. 
regulator, G. E. type, 468. 
Feeders, arrangement of, 788. 
capacity of, 786. 
classes of, 788. 
design of, 787. 
load on, 787. 
regulation of, 513. 
Feed- water heaters, 1375. 

heating by pump exhaust, 1377. 

pipes, sizes of, 1373. 

saving by heating, 1376. 

saving in fuel by heating, 1377. 
Ferro-nickel wire, properties of, 202, 

207. 
Feet per minute in miles per hour, 

660. 
to centimeters, 1503. 
Fibre, specific inductive capacity 

of, 227. 
Field buzzer, 1140. 

coils, cooling surfaces of, table of, 
352. 

heating of, 352. 

resistance of, 401. 
frame of induction motor, slots in, 

426. 
intensity, value of, 7. 
magnet coil surface, 352. 

cores, design of, 365. 

excitation, 365. 

windings, 369. 

magnets, ampere turns in, 366. 

design of, 364. 

general data on, 352. 

use of various types of, 355. 
rheostats, electrically controlled, 

942. 



INDEX. 



1555 



Field switchboards, electrically con- 
trolled, 942. 
telegraphs, 1140. 
telephones, 1140. 
wireless set-pack, 1145. 
Figure of merit of galvanometers, 

21. 
Filling standard cell, 13. 
Fire alarm system, U.S. Navy, 1210. 
brick, sizes of, 1321. 
protection in transformer house, 

871. 
temperature of, 1349. 
Fires caused by lightning, 1279. 

due to electrolysis, 859. 
Firing guns, navy method of, 1212. 

mechanism, electric, 1148. 
Fish ladders, 869. 
Fiske range finder, 1211. 
Fixtures, U. S. Navy, 1171. 
Flame at commutator, 805. 
Flame-proof coverings, 939. 
Flaming arc lamp, 572. 
Flaming-point of carbons, 577. 
Flanges, pipe, 1430-1433. 
Flat plates, Board of Trade rules, 
1333. 
boiler, safe pressure on, 1332. 
Flash, energy of, 1278. 
lightning, data on, 1277. 
test of transformer oil, 500. 
Fleming's method, meas. A. C. 
power by, 71. 
modification of Hopkinson's test, 
394. 
Flexible dynamo cable, table of, 172. 
Flexure of beams, fundamental 

formulae of, 1308. 
Flow of steam in pipes, 1416. 
of water, estimate of, 869. 

in a stream, measurement of, 

1471. 
in various pipes, 1373. 
over weirs, 1473.. 
through an orifice, 1470. 
Fluctuating load diagram, 888. 
Flues, boiler, area of, 1329. 
Flumes and ditches, 1468. 
Fluoroscopes, use of, 1255. 
Fluorspar, spec. ind. cap. of, 36. 



Flux density for induction motors, 
427. 

of force, value of, 7. 

for transformer cores, curve of, 
446. 

in air-gap, 365. 

in field magnets, 366. 

magnetic, definition of, 4. 
Foot, decimals to inches, 1505. 

-candle, def. of, 525. 

-pound, value of, 12. 

valve, 1447. 
Forced draught, blowers for, 1344. 
Force on conductors in magnetic 
field, 108. 

de cheval, 3. 

definition and unit of, 3. 

magnetomotive, definition of, 5. 

magnetizing, definition of, 4. 
Forge, electric, Burton, 1274. 
Forging by electricity, 1271. 
Form-factor of wave, 501. 
Formulae for transmission lines, 275. 
Formula for testing Shallenberger 

meter, 1028. 
Fortress telegraphs, 1140. 

telephones, 1140. 
Fort Wayne induction wattmeters, 
1005. 

wattmeters, testing of, 1032. 
Forward lead of brushes, 350. 
Foucault currents in armature, 
prevention of, 350. 

currents, representation of, 386. 
Foundation beds, load on, 1292. 

concrete, 1292. 

engine, 1292. 

on clay, 1290. 

on piles, 1291. 

on soft earth, 1291. 
Foundations, 1290. 

and structural materials, 1289. 

brick, 1292. 

eye beam, 1293. 

on gravel, 1290. 

on rock, 1290. 

stone, 1293. 

on sand or gravel, 1290. 
Four-circuit single winding of arma- 
tures, 342. 



1556 



INDEX. 



Four-party selective telephone sys- 
tems, 1103. 
-wire two-phase system, formula 
for, 270. 
Frame buildings, steel, electrolysis 

in, 859. 
Frames for switchboards, 908. 
Francis* weir formulae, 1474. 
Freight elevators, operating cost of, 

1528. 
French calorie, 1511. 
Frequency changer, def. of, 503. 
definition of, 501. 
symbol of, 8. 
Frequencies, discussion of standard, 
522. 
of generators, 870. 
Friction, 1505. 

load in machine shops, 1523. 
brush contact, 362. 
curve for train, 679. 
curves of railway motors, 676. 
test for dynamos, 383. 
Fuel economizers, 1378. 

economizers, Green's, 1378. 
value of woods for, 1349. 
Fuels, draft necessary to burn, 1342. 
gaseous, 1357. 

heat of combustion of, 1347. 
kinds and ingredients of, 1346. 
liquid, 1356. 

total heat of combustion of, 1347. 
Fuller cell, description of, 16. 
Fundamental principles of dynamos 
and motors, 336. 
units, definition of, 2. 
symbols of, 1. 
table of, 6. 
Furnace, electric, efficiency of, 1244. 
Furnaces, oil, 1357. 
Fuse block, ins. of, meas. of, 82. 
data, 1275. 
wires, rating of, 1275. 
table of, 1275. 
Fuses for firing guns, electric, 
1134. 
for railway circuits, 731. 
installation of, 1276. 
Fusing effect of current, 217. 
Fusion, electric, def. of, 1232. 



Gallon, 1499. 
Galvanic cell, 14. 

Galvanized iron telegraph wire, 
properties of, 199. 
iron wire for water rheostats, 34. 
steel strand wires, 642. 
Galvanometer, ballistic, 25. 
constant, 23. 
D'Arsonval, des. of, 25. 
Kelvin type, 23. 

method, differential, res. by, 56. 
ins. res. of wiring system by, 84 
moving coil, des. of, 25. 
reflecting, Kelvin, 23. 
scale, 24. 
shunt boxes, 29. 
telescope, 24. 
tangent type, 22. 
used with potentiometer, 48. 
Galvanometers, 21. 

figure of merit of, 21. 
moving-coil, 21. 
moving-needle, 21. 
resistance of, 60. 
Gap, air, mechanical, 363. 

distance curves, 234. 
Garton lightning arrester, 990. 
Gas and electricity compared foi 
cooking, 1260. 
and electric rates compared, 1261 
engine power plant, 1450. 

pumping plant, 1450. 
Mghts, wiring for, 295. 
test of, 1450. 
engines, 1448. 

classification of, 1448. 
comparative economy of, 1449. 
cost of lifting water by using, 

1450. 
heat energy disposition in, 1450. 
value of coal gas for, 1450. 
light wiring, 295. 
passages and flues, 1329. 
Gaseous fuels, 1357. 
Gases, effect of temp, on fan load, 
1346. 
specific gravity of, 1512. 
Gasner cell, 15 ; dry cell, 18. 
Gauges, wire, table of, 141. 
Gauss, definition of, 4. 



INDEX. 



1557 



Gauss, value of, 7. 
Gem lamps, 549. 
General Electric Company: 
A.C. lightning arrester, 987. 
A.C. motor characteristics, 713. 
A.C. overload relay, 961. 
A.C. railway system, 710. 
arc switchboards, 922. 
car controller, 753. 
circuit breaker, 950. 
constant current transformers, 

464. 
induction motors, 297. 

current taken by, 297. 
locomotives, 740. 
mercury arc rectifiers, 480. 
multiple unit control, 761. 
oil break switch motor, 976. 

switch, 979. 
prepayment wattmeters, 1010. 
railway motors, 729. 

characteristic curves of, 686. 
recording meters, 1037. 

wattmeters, testing of, 1030. 
rubber ins. wires and cables, 

tables of, 164-172. 
searchlight, 1181. 
surface contact railway, 847. 
switchboard panel, 907. 
system, electric heating, 1257. 
wattmeter constant, 1030. 
wires and cables, tables of, 161- 

178. 
General symbols, 1. 
Generating station, hydro-electric, 

section of, 930. 
sets, tests on U. S. Navy, 1159. 

U.S. Navy, 1153. 
Generator circuit protection by 

relays, 959. 
control pedestal, 940. 
efficiency, U. S. Navy, 1158. 
magneto, constr. of, 1078. 
panels, Westinghouse three-wire, 
926. 

D.C., equipment of, 924. 

three-phase, 912. 

two-phase, 915. 
polyphase, 502. 
switchboard, U. S. Navy, 1163. 



Generator, three- wire system, 355. 
turbo, U. S. Navy spec, for, 
1161. 
Generators, double current type, 
440. 
frequencies of, 870. 
protection by static interrupter of, 

993. 
rating of, 50 
regulation of, 870. 
speed of, 870. 

U. S. Navy, spec, for, 1156. 
wiring for, 295. 
Geometric units, derived, 2. 

table of, 6. 
German silver, fusing effect of 
current on, 217. 
silver, phys. and elec. prop, of, 

136. 
silver wire, properties of, 202. 
res. of, 203. 
Gest's manhole, cut of, 312. 
Ghegan repeater, 1042. 
Gibbs' process, potassium chlorate 

by, 1242. 
Gilbert, definition of, 5. 

value of, 7. 
Glass, specific heat of, 1511. 

specific inductive capacity of, 36, 
227. 
Globes, effect on light of, 582. 
Glower of Nernst lamp, 562. 
Gold, phys. and elec. prop, of, 
136. 
plating, 1234. 
spec. res. of, 132. 
temperature coef. of, 133. 
Goldschmidt weld, 778. 
Gordon's formulae for columns, 

1300. 
Gott's method, testing cap. of 

cables by, 326. 
Gould storage battery, 1228. 
Government printing office, heating 

devices in, 1269-1270. 
Grades and rise, 617. 
effect of, 612. 
formula for, 665. 
tractive effort on, 657, 661. 
Gradient, magnetic, 130. 



1558 



INDEX. 



Gramme armature, windings of, 342. 

definition of, 2. 

-degree C, value of, 12. 
Granite, crushing load on, 1322. 
Granular button transmitters, 1074. 
Graphic illuminating chart, 587. 

recording meters, 1036. 
Graphite, production of, 1245. 
Grates, air space in, 1329. 
Grate, space between boiler and, 
1329. 

surface per h. p., 1329. 
Gravel, foundations on, 1290. 
Gravity cell, des. of, 15. 

resistance due to, 1224. 
Greases, 1497. 
Greek letters, 1505. 
Green's fuel economizer, 1379. 
Grey cast iron, phys. and elec. prop. 

of, 137. 
Grinding machines, power required 

for, 1521. 
Ground connections, 983. 

connections for lightning rods, 
1279. 

detectors, static, installation of, 
942. 

on arc circuits, meas. of, 81. 

return drop, test of, 799. 
Grounded armature, test for, 402. 

neutral, circuits with, 984. 
Grounding the neutral, 478. 
Grouping of cells, 19. 

of ducts in manhole, 318. 
Grove cell, 14. 

Guarantees of transformers, 482. 
Guns, coast defense, manipulation of, 
1134. 

firing, Navy method of, 1212. 

motors for operating, 1191. 

rapid fire, 1149. 
Gutta-percha covered wire, jointing 
of, 193. 

properties of, 231. 

spec. ind. cap. of, 36, 227. 
Guy wires, 638. 

Gypsum, spec. ind. cap. of, 36. 
Gyration, radius of, 1303. 
Gyrostatic action on ship dynamos, 
353. 



Half- Atkinson repeater, 1048. 
deflection method, res. of galv. by, 
60. 
Hall process, aluminum production 

by, 1239. 
Hand control, A. C. railway system,, 
710. 
-operated oil break switch, G. E. 
type, 978. 
remote-control switchboards, 

928. 
switchboard, 906. 
potential control system of G. E. 
Co., 710. 
Hangers required per span for tan- 
gent track, 646. 
Hannibal shops, St. Joseph and K. 

Ry. motors, 1518. 
Harcourt pentane standard, 530. 
Hard-drawn copper telegraph wire, 

prop, of, 156. 
Harmonics, theory of, 1218. 
Head, choice of, 869. 
Headway of cars, table of, 658. 
speed and number of cars, table of, 
660. 
Heat, 1509. 

absorption curves, 1376. 
balance, 1389. 

energy from burning gas, 1450. 
in printing plants, electric, 1269- 

1270. 
intensity of, 1506. 
light and power in isolated plants, 
cost of, 1285. 

cost in residences of, 1287 
mechanical equivalent of, 

1511. 
of electric arc, 581. 
radiation in ducts, 214. 
run of dynamos, 379» 
temperature and intensity of, 

1506. 
test of induction motors, 398. 

of transformer, 489. 
transmitted through cast iron 

plates, 1425. 
units, 3, 1258, 1510. 
in steam, 1404. 
table of, 1510. 



INDEX. 



1559 



Heaters, energy consumption of 
electric, 1265. 
feed water, 1375. 
Heating by convection, 1264. 
by radiation, 1264. 
cars by electricity, 770. 
devices in laboratories, elec, 1270 
effect on hysteresis loss in trans- 
former, 457. 
electric, 1263. 
cars, 1265. 

classification of, 1256. 
industrial electric, 1269. 
of armatures, 349. 
of cables in ducts, 210. 
of field coils, 127, 352. 
of transformers, meas. of, 497. 
pipes, condensation in, 1415. 
surface of steam boilers, 1328. 
of tubes, 1328. 

per horse-power in boilers, 1329. 
water by electricity, cost of, 1259. 
Hefner amyl lamp, 532. 

unit, 532. 
Hekto-ampere meter, balance used 

as, 44. 
Helm angle indicators, U. S. Navy, 

1202. 
Hemp rope, weight of, 1494. 
Henry, definition of, 9, 238. 
international, 10. 
measurement of, 64. 
value of, 8. 
Heroult process, aluminum produc- 
tion by, 1239. 
Herrick testing-board, 805. 
Hertzian oscillator, 1057. 
Hexane, spec. ind. cap. of, 37. 
High efficiency lamps, use of, 589. 
High potential circuit arresters, 993. 
generators, protection by static 

interrupter of, 993. 
on A.C. circuits, protection 

against, 981. 
switches, 967. 
tests, U. S. Navy, 1168. 
High power transmitters, 1063. 
resistances, meas. of, 79. 
resistance for voltmeters, 75. 
speed car tests, 727. 



High-speed railway trials, 719. 
High-tension bus bar structure, 
935. 

conductors, insulation of, 939. 

lamps, 570. 

lines, aluminum for, 199. 

station bus bars, 933. 

switches, 967. 

transmission, conductors for. 
235. 

voltage transformers, 938. 

wires in power station, 867. 
High voltage, break down tests fcr. 
233. 

testing set, 461. 

tests, 515. 

tests of cables, 332. 

transmission, 870. 
Hissing-point of carbons, 577. 
Hoho-Lagrange system, 1274. 
Hoist, ammunition, electric, 1147. 
Hoists for ammunition, U. S. Navy, 

1191. 
Holden hysteresis meter, 102-104. 
Hollow shafts, 1485. 
Holtzer-Cabot telephone system, 

U. S. Navy, 1208. 
Hook switch, design of, 1075. 
Hopkinson's test of two similar D.C. 

dynamos, 393. 
Horizontal return tubular boilers, 

1327. 
plane illumination, 586. 
Horn type lightning arresters. 995. 
Horse-power, definition of, 3, 52 

formulae for machine tool re' 
quirements, 1515. 

of Manila ropes, 1491. 

of motors, meas. of, 395. 

of railway motors, 731. 

of running stream, 1462. 

of steam boilers, 1327. 

of steam engines, 1440. 

of street railway motors, 661. 

of traction, 653. 

of water, tables of, 1475. 

required for automobiles, 1224. 

second, value of, 12. 

used in electric welding, 1271. 

used in factories, 1517. 



1560 



INDEX. 



Hotel telephone systems, 1088. 
Hot-filament detectors, 1068. 
Hours of burning lights, 611. 
House circuits, res. of, 61. 
telephone systems, 1088. 
transformers, capacity of, 458. 
wire, weather-proof, table of, 160. 
wiring, 279, 293. 
Humphreys' lighting tables, 607. 
Hydraulic head, choice of, 869. 
plants, constr. of, 868. 
turbiDes, regulation of, 514. 
Hydro-electric plant, section of, 930. 
switchboard for, plan of, 931. 
transformer cell, plan of, 931. 
Hydro-electrothermic system, 1274. 
Hydrogen as depolarizer, use of, 879. 

spec. ind. cap. of, 35. 
Hysteresis curves for transformer 
cores, 453. 
factors, table of, 100. 
in armature core, 341. 
index, 99. 

loss factors, table of, 99. 
formula for, 98. 

in transformer core, table of, 457. 
in transformers, law for, 445. 
tests, 385. 
meter, G. E. type, 102-104. 
tester, Ewing type, 102. 
testing by step-by-step method, 

101. 
testing by wattmeter method, 102. 
Hysteretic constants, table of, 99. 

IA JIA wire, properties of, 204. 
Illuminants, rating of, 540. 
Illuminating chart, 588. 

engineering, 584. 

lamps for switchboards, 909. 

values, data on, 592. 
Illumination, efficiency of, 584. 

formulae for, 584, 587. 

for reading, 602. 

for various purposes, 589. 

intensity of, laws of, 528. 
table of, 586. 

of interiors, 596. 

units of, 525. 
Impedance coils, use of, 429, 1117. 

definition of, 259. 



Impedance coils, formula for, 1221. 
in alternators, 405. 
in A.C. coils, 127. 
of steel rails to A.C. current, 795. 
of transformer, meas. of, 487. 
Impedance ratio, def. of, 514. 

symbol of, 8. 
Impressed E.M.F. curves, 1218. 

E.M.F. of transmission circuits 
239. 
Improvement in transformers, 454. 
Impulse currents, generator for, 
1103. 
water wheel, 1477. 
Impulsive rush discharges, 1278. 
Impurities in electrolyte, 877. 
Incandescent lamps as standards, 
533. 
burning out of, 805. 
cost of, 556. 
efficiency of, 540. 
light by, 601. 
luminosity of, 548. 
navy spec, for, 1171.* 
navy standard, 1176. 
proper use of, 544. 
rating of, 525. 
renewals of, 556. 
uses of, 555. 
Incandescent station lightning 

arrester, 986. 
Inch, miner's, 1473. 
Inches to decimals of a foot, 1505. 

to millimeters, 1504. 
Inclined planes, strains in rope on, 

1494. 
Inclosed fuses, 1276. 
Incrustation, causes of, in boilers, 
1362. 
means for preventing, 1362. 
Index, hysteresis, 99. 

notation, 2. 
Indicators, order, U. S. Navy, 1202. 
Induced E.M.F. in transformers, 
equation for, 446. 
draught, fans for, 1345. 
Inductance and capacity, neutrali- 
zation of, 292. 
choking effect of, 1079. 
definition of. 9- 



INDEX. 



1561 



Inductance and capacity in A.C. 

circuit, effect of, 1216. 
mutual, meas. of, 67. 
of A.C. circuits, 239, 259. 
Induction coil, constr. of, 1074. 
coil, design of, 1074. 

for X-rays, use of, 1252. 
coef. of, meas. of, 65. 
electromagnetic, 64. 
generator, 502. 
law of, 64. 

machines, losses in, meas. of, 511* 
magnetic, definition of, 4. 
meters, design of, 1003. 
Induction motor, current taken by, 
297. 

flux densities for, 427. 

methods of starting, 918. 

panels, equipment of, 918. 

polyphase type, 422. 

power del'd to, 280. 

regulation of, 383, 513. 

rotor slots for, 427. 

slots in field frame of, 426. 

speed of, 424- 

starter, def. of., 503. 

transformers for, 296. 

test of, 397. 

wiring for, 296. 
Induction potential regulator, 469> 

503. 
telegraph, field, 1140. 
transposition to eliminate, 285. 
type furnace, 1244. 

wattmeters, Westinghouse, 999, 
1003. 
wattmeters, Thomson polyphase, 

1005. 
Inductive capacity, spec, def. of, 38. 
capacity of gases, values of, 35. 

of substances, table of, 36, 37. 
circuits, wattmeters on, 1000. 
drop in trolley, 797. 
effect of alternating currents, 236. 
load, def. of, 50£ 

regulation of transformer for, 
492. 
loads, testing meters on, 1018. 
reactance, formula for, 239. 

In ohms per 1000 feet, 242. 



Inductive reactance fn solid iron 

wire, table of, 248. 

in three-phase line, 245. 

representation of, 259, 

Inductor alternator, def. of, 502. 

type synchroscope, 417. 
Industrial electric heating, 1269. 
Inertia, moment of, 1302. 

of rotating parts of train, 683. 
Ingredients of rails, table of, 780. 
Injectors, deliveries by live steam, 
1371. 
exhaust, 1372. 
lifting cold water by, 1372. 

hot water by, 1372. 
live steam, 1370. 
performance of, 1371. 
vs. pumps for boiler feeding, 
1372. 
Installation of battery plants. 897. 
of car motors, 745. 
of fuses, 1276. 
of polyphase meters, 1023. 
of storage batteries, 885. 
Instantaneous relays, 956. 

value of E.M.F.. 404. 
Instrument posts, 941. 
scales, figuring, 946. 
Instruments, electrical measuring, 
21. 
for switchboard, 940, 945. 
testing, description of, 13. 
Insulated cables, varnished cambric, 
triple conductor, 185. 
cables, varnished cambric, tables 

of, 179-183. 
copper wires and cables, table of, 

160. 
wires and cables, rubber cov., tables 
of, 164-172. 
carrying capacity of, 209. 
locating faults in, Warren's 
method of, 330. 
Insulating cable ends for tests, 322. 
cable joints, 191. 
ground near power station, 862. 
joints in mains, 861. 
materials, dielectric strength of, 
228. 
puncturing voltages for, 225. 



1562 



INDEX. 



Insulation across fuse block, meas., 

of, 82. 
distances on switchboards, 912. 
of armature core, 341 . 
of dynamos, meas. of, 86. 
of high-tension cables, 939, 
of transformer, 447. 
resistance betw. conductors, N. C, 
85. 

by loss of charge method, 322. 

meas. of, 514. 

of arc light circuits, 81. 

of cables, 321. 

of circuits, meas. of, 80, 85. 

of dynamos, 86. 

of motors, 87. 

of railway lines, 783. 

of rubber, 231. 

of telephone cables, 1084. 

U. S. Navy standard, 1168. 

of wiring system, 82. 
test of cables, 332. 

of dynamos, 381. 

of rubber, 230. 

of transformers, 483. 
Insulators for third rail, 831. 

Metropolitan street railway, 840. 
on poles, arrangement of, 291. 
Integrating meters, action of, 997. 
meters, Westinghouse, D.C., 998. 
photometer, 539. 
wattmeters, data for, 1016. 

induction type, 999. 

tests of, 1013. 

Westinghouse, 1004. 
Intensity of brilliancy, 599. 
of current, symbol of, 8. 
of illumination, laws of, 528. 

table of, 586. 
of light, 530. 
of magnetic field, 4. 

force, def. of, 108. 
of magnetization, 4. 

value of, 7. 
of searchlights, 1125. 
Interaxial distances between A.C. 

conductors, 240. 
Interborough rail, 830. 
Intercommunicating telephone sys- 
tems, 1088, 1114. 



Inter-connected star arrangement 
of three-phase transformers, 
477. 
Interior illumination, 596. 

wiring, carrying cap. of cond- for, 
209. 
Interlock switches for railway con- 
trol, 768. 
Intermediate distributing frames, 

1104. 
Internal characteristic of shunt 
dynamo, 339. 
resistance of batteries, meas. of, 
87. 
of cells, 20. 

of storage batteries, 883. 
International ampere, def. of, 9- 
ampere, specification for determ., 

10. 
coulomb, def. of, 9. 
electrical units, 9. 
farad, def. of, 9. 
standard, 38. 
henry, value of, 10. 
joule, value of, 10. 
ohm, construction of, 30. 
def. of, 9. 
value of, 131. 
volt, definition of, 5, 9. 

determ. of, 10. 
watt, value of, 10. 
Interpolar edges, design of, 363. 
Interrupters, Wehnelt, 1254. 
for X-rays, use of, 1253. 
Interurban booster calculation, 
812. 
car tests, 722, 725. 
Intrinsic brightness of sources of 

light, 529. 
Inverse time limit relays, 957. 
Inverted converter, def. of, 436. 
Inward flow turbines, 1476. 
Iron ageing tests, curves of, 453. 
and steel, ageing of, 455. 
elec. welding of, 1271. 
magnetic fatigue of, 45^. 
permeability curves of, 90. 
wire, constants of, 199. 
fusing effect of current on, 217 
in electrolyte, test for, 877. 



INDEX- 



1563 



&*"**> loss curves of Westinghouse 
motors, 674. 

determinations, 107. 

In transformer, table of, 482. 

In transformer cores, 453. 

In transformer, Sumpner's 
method, 496. 
magnetic properties of, 89. 
permeability of, 89. 

meas. of, 94. 
phys. and elec. prop, of, 137. 
pieces of, attraction between, 111. 
pipe, elec. welding of, 1272. 
plating, 1234. 
poles, 633, 
production of, 1247. 
spec. res. of, 132. 
stacks, guyed, cost of, 1344. 
telegraph wire, galv., properties 

of, 199. 
temperature coef. of, 133. 
U. S. standard gauge, weights of, 

1299. 
weight of, 1294. 

flat per foot, 1295. 

plate, 1298. 

square and round, 1297. 
wire for water rheostats, 34. 

inductive reactance in, table of, 
248. 

properties of, 199. 

self induction in, 240. 

self induction in, table of, 248. 

skin effect factor for, 238. 

use in telephony of, 1082. 
Irons, electric, cost of operating, 1263. 
soldering and branding, elec, 1270. 
Isolated electric plants, economy of, 

1283. 
plant, coal consumed by, 1286. 

vs. central station, 1286. 
Isolation of conductors on switch- 
boards, 929, 936. 
Itemized cost of conduit, tableof 9 316= 

JTack« for ammeter connections, 922 

telephone, 1089. 
Jamison rule for ins, res., 85 
Jigger, use of, 1065. 
Joint effect of electrolysis, 853, 



Jointing gutta-percha covered wire, 

193. 
Joints, Dossert cable, 191. 

in cables, testing of, 323. 

in mains, insulating, 861. 

in paper insulated cables, 191 

in rubber ins. cables, 190= 

in Waring cables, 191. 

per mile of track, 618 

rail, tests of, 801. 

insulating cable, 191. 
Joly's photometer, 536. 
Joule, definition of, 3, 

value of, 5, 8, 
Joule's equivalent, 4. 
Jump distance curve, 234. 
Jumping-point of carbons, 577, 
Junction boxes, U. S. Navy gpec 
for, 1171 = 

Kapp's efficiency test of two dyna- 
mos, 387. 
potential regulators, 468. 
Kempe rule for ins. res. ; 85. 
Kelvin balance, diagram of, 44. 
electric balance, 43. 
electrostatic voltmeter, 40. 
galvanometer, 23. 
Kelvin's double bridge, 59. 
law, 261, 787. 

applied to booster distribution, 
810. 
multicellular voltmeter, cap. test 
with, 326. 
Kerosene for boilers, 1364. 
Kilowatt curve for railway motors, 

669. 
Kilowatts of energy in three-phase 
cables, 216. 
on grades, 657. 
Kinetic energy, 3. 
King carbide furnace, 1245 
Kirchoff's laws, 55. 
Knee of saturation curve, 401, 
Krupp's wire, properties of, 202, 206. 
Kryptol method, electric heating, 
1257 

I a lie! rating of gem lamps, 549. 
Laboratories, electric heat in, 1370. 



1564 



INDEX. 



Lagging current, effect of, 439. 
Lake electric railway, high-speed 

trials on, 719. 
Lamination of cores, reason for, 99. 
Laminations for transformer core, 

445. 
Lamp indication for oil circuit 
breaker, 975. 
renewals, 547. 
signals, telephone, 1098. 
Lamps, candle-power of, drop in, 
544. 
current taken by, table of, 542. 
efficiency of, 525. 
life of, 544. 
material required for instal. of, 

1531. 
Navy spec, for, 1171. 
U. S. Navy standard, table of, 
1176. 
Lande cell, 14. 
Lanterns, diving, 1179. 
, Lap-connected armature windings, 
345. 
Lateral, def. of, 302. 

effect of electrolysis, 853. 
Lathes, power required for, 1516. 
Law cell, 15. 

of Brown & Sharpe wire gauge, 

142. 
of induction, 64. 
of plunger electromagnet, 127. 
of traction, 110. 
Maxwell's, 94. 
Laws, Kirchoff's, 55. 

of circuits, elementary, 55. 
Laundry irons, electric, cost of 

operating, 1263. 
Layers of cotton -covered wires, 
space occupied by, tables of, 
121-126. 
Laying out dynamos, procedure in, 

370. 
Lay-overs at end of run, 676. 
Lead burning, 885. 

covered cables, carrying capacity 

of, 213. 
covered cables, tables of, 174- 

178. 
covering of cable joints, 191. 



Lead burning, fusing effect of currenl 
on, 217. 

of brushes, 350. 

peroxide, use in batteries of, 873 

phys. and elec. prop, of, 137. 

plates, joining of, 885. 

sheathed telephone cables, 188. 
telegraph cables, 189. 

sheath of cable, loss of power in, 
293. 

spec. res. of, 132. 

sulphate, use of, 873. 

temperature coef. of, 133. 
Leading current, production of, 439. 
Leads for transformers, 499. 
Leakage current on railway line, 783. 

coefficients, magnetic, 376. 

drop in transformers, 497, 

of magnetic lines in dynamos, 365. 

reactance, def. of, 503. 
Least exciting current of syn- 
chronous motors, 400. 
Leclanche* cell, des. of, 16. 
Leeds & Northrup bridge, 32. 
Legal ohm, value of, 131. 
Lemon oil, spec. ind. cap. of, 37. 
Length, measures of, 1499. 

of magnet coils, corrections for, 
tables of, 117-120. 

of magnet cores, 365. 

of sparks, curves of, 949. 
Leonard's system of electric pro- 
pulsion, 354. 
of motor control, 354. 
Le Roy method, electric heating, 

1257. 
Letters, Greek, 1505. 
Lever switches, 963. 
Life of carbons, 577. 

of lamps, 544. 

tests, Navy spec, for lamp, 1172. 
Lifting-power of electromagnets, 110. 
Light and power cables, 320. 

control from two or more points, 
294. 

cut off by globes, 582. 

data on, 528. 

distribution of, 599. 

heat and power, cost in residences 
of. 1287. 



INDEX. 



1565 



Light, heat and power in isolated 

plants, cost of, 1285. 
standard of, 530. 
units of, 530. 
Lighting cars, G. E. railway system, 

851. 
circuits, res. of, meas. of, 80. 
lines, transposition of, 285. 
methods, comparative values of, 

594. 
of street cars, 806. 
plant, batteries for residential, 

898. 
schedule for London, 611. 
schedules, 603. 
service, navy, 1153. 
system, U. S. Navy, 1171. 
Ughtning arresters, arc station, 985. 

direct current, 984. 

function of, 980. 

Garton, 990. 

General Electric A.C., 987. 

high potential circuit, 993. 

horn type, 995. 

incandescent station, 986. 

in central stations, 983. 

in power station, 867. 

inspection of, 984. 

insulation of, 984. 

low equivalent, 994. 

magnetic blow-out, 987. 

multiplex three-phase, 988, 

non-arcing D.C., 984. 
metal double pole, 989 

railway non-arcing, 985. 

S.K.C., 990. 

spark gaps of, 991. 

Stanley, 990. 

unit, 990. 

use of, 1087. 

Wurts type, 984. 
Lightning flash, data on, 1277. 

protection, 980. 
Lightning rods, history of, 1277. 

installation of, 1278. 

points of, 1281. 

tests of, 1282. 
Lime mortar, 1293. 
Limestones, crushing load of, 1322. 
Limitation of voltages, 866. 



Limit of sag for aluminum wire, 225. 
Limits of telephonic transmission, 

1107. 
Lincoln synchronizer, 416. 
Lineal measures, metrical equiva- 
lents of, 1500. 
Linear space occupied by d.c. cov. 
wire, table of, 123-126. 
s.c. cov. wire, table of, 121-123. 
Line capacity, effect of, 264. 

discharger of S.K.C. arrester, 991. 
drops, 1090. 

equipment, depreciation of, 770. 
formulae, transmission, 275. 
material per mile of trolley, 643. 
power loss in, 261. 
pressure, adv. of high, 260. 
relay for railway control, 769. 
switch for railway control, 767. 
wire, weather-proof, table of, 160. 
Link shoe for third rail, 832. 
Liquid fuels, 1356. 

rheostats, 33. 
Liquids, measures of, 1500. 

measures of, metrical equivalents 

of, 1502. 
specific gravity of, 1512. 
ind. cap. of, table of, 37. 
res. of, 133. 
Load curve, 887. 

diagram, fluctuating, 888. 
factor, def. of, 506 

of railway system, 785. 
factors, cost of power at various, 

868. 
hauled by motor car, 655. 
losses, meas. of, 509. 
on foundation beds, permissible, 

1292. 
peak, batteries to carry, 886. 
power factors, 279. 
steel beams, safe, 1310. 
test of motors, 395. 
Loading gear for guns, 1191 

telephone lines, 1107. 
Local action in storage batteries, 878. 
Locating breaks in cables by cap. 
test, 327. 
crosses in cables, Ayrton method, 
327, 



1566 



INDEX. 



Locating faults in cables, loop 
method, 328. 
in underground cables, 331. 
Location of transformers, 499. 
Locomotives, electric, 614. 
electric, table of, 739, 
tractive coefficient of, 662. 
Loft building plant, economy of, 

1285. 
London, lighting schedule for, 611. 
Long distance transmission, data on, 
866. 
transformers for, 474. 
Loop method, locating- faults in 

cables by, 328. 
Lord Kelvin's composite balance, 43. 
multicellular voltmeter, cap. test 
with, 326. 
Lord Rayleigh's method, E.M.F. of 

batteries, 62. 
Loss factors, hysteresis, table of, 99. 
in line, power, 261. 
of active material in battery plates, 

881. 
of capacity of storage batteries, 

881. 
of charge method, ins. res. by 322. 

of storage batteries, 884. 
of head due to bends, water, 1374. 
of potential method, meas. cap. by, 

64. 
of power in cable sheath, 293. 
of voltage in storage batteries, 882. 
Losses at brush faces, 362. 
core, 98. 
electrical method of supplying, 

389. 
in armature, formula for, 358. 
in machines, meas. of, 509. 
in transformers, 445. 
comparative, 455. 
curves of, 453. 
Lowell mill power, table of, 1464. 
Low equivalent lightning arrester, 
994. 
resistance detector, 1065. 

meas. of, 59. 
tension lamps, 569. 
voltage A.C. relay, 962. 
D.C. relay, 961. 



Lubricants, best for diff. purposes, 

1498. 
Lubrication, 1497, 

of engines, 1413. 

of motors, navy spec, for, 1185. 
Lumen, def- of, 521;, 5C2. 
Luminosity of inc. lamps, 548. 
Luminous flux, 529. 
Lummer-Brodhun photometer, 536. 
Lumsden's method, E.M.F. of batte- 
ries, 62. 

Machine shops, friction load in, 

1523. 

lighting of, 597. 

men employed in, 1523. 

power to run, 1518. 
tools, power to drive, 1515. 
Magazine light boxes, U.S. navy,1171. 
Magnesium, phys. and elec. prop, of, 

137. 
Magnet coils, correcting length of, 

table of, 117-120. 
coils, general data on, 352. 

heating of, 127. 
cores, design of, 365. 
poles, determination of number of, 

355. 
windings, field, 369. 
wire, res, of, table of, 112. 
Magnetic blow-out lightning arrester, 

987. 
circuit in dynamos, balancing of, 
349. 

of transformer core, equation 
for, 446. 

principle of, 109. 
density of transformer cores, 447. 

of field magnet cores, 365. 

of armature cores, 357. 

of armature teeth, 367. 

of pole faces, calc. of, 356. 
detectors, 1067. 
distribution, curve of, 340. 
fatigue of iron and steel, 455. 
flux, definition of, 4. 

formula for, 109. 
field, intensity of, 4. 
force, intensity of, 108. 
gradient, 130. 



INDEX. 



1567 



Magnetic induction, definition of, 4. 
value of, 7. 
leakage coefficients, 376. 

in dynamos, 365* 
moment, 4, 7. 

permeability, definition of, 5. 
properties of iron, 89. 
resistance, definition of, 5. 

specific, 5. 
square method, determ. magn. 

values by, 93. 
susceptibility, definition of, 5. 
units, definition of, 4. 
symbols of, 1. 
table of, 7. 

values, determination of, 91. 
Magnetism, residual, def. of, 108. 
Magnetite arc lamp, 570. 
Magnetization, intensity of, 4. 
of electromagnets, table of, 111. 
curve of dynamos, 336. 
curves of D.C. motor, 353. 
Magnetizing force, definition of, 4. 

value of, 7. 
Magneto-generator, constr. of, 1078. 
Magnetometer method, determ. 

magn. values by, 91. 
Magneto-motive force, def. of, 5, 108. 
value of, 7. 
Magneto potential regulators, def. of, 

503. 
Magneto transmitters, 1071. 
Magnets, excitation of field, 365. 

field, design of, 364. 
Main distributing frames, 1104. 
Mains, insulating joints in, 861. 
Maintenance of Nernst lamps, 564. 
Mance method, res . of batteries by,61 . 
Manganese, effect on steel of, 825. 

steel, phys. and elec. prop, of, 137. 
Manganin wire, properties of, 202, 

204. 
Manhattan rail, 830. 
Manhole constr., cuts of, 309. 

constr. for shallow trenches, 319. 
improved forms of, 318. 
of Niagara Falls Power Co., 

319. 
objectionable types of, 318. 
cost of, 5' X 5' X 7', 316. 



Manhole covers, cuts of, 313-315. 

def. of, 301. 

estimating cost of, 317. 

of conduit Metropolitan Railway. 
838. 
Manholes, brick, cost of, 303. 

concrete, cost of, 303. 

cost of, table of, 302. 

sizes of, 302. 
Manila rope, data on, 1492. 
Manipulation of coast defense guns, 

1134. 
Marble, crushing load, 1322. 

for switchboards, 907. 
Market wire gauge, use of, 201. 
Mascart electrometer, 39. 
Masonry, 1321. 
Master controller, multiple unit 

system, 764. 
Material per mile of trolley line, 643. 

required for one mile of railway, 
628. 
Materials, strength of, 1301. 
Mats burglar alarm, wiring of, 295. 
Matthiessen's copper formula, 133. 

standard of conductivity, 132. 
Maximum current, A. C. windings, 
127. 

output of induction motors, 398. 

value of E.M.F. of A.C. current, 
404. 
Maxwell, definition of, 4. 

law of traction, 94. 

value of, 7. 
Mean current, A.C. windings, 127. 

effective pressure, table of, 1442. 

hemispherical candle-power, def. 
of, 529. 

horizontal intensity, 529. 

length per turn of coil, table of, 
114-116. 

spherical candle-power, def .of, 529. 

spherical candle-power of arc 
lamps, 580. 
Measure, apothecaries*, 1500. 

avoirdupois, 1500. 

of capacity, 1499. 

of length, 1499. 

of liquids, 1500. 

of surface, 1499. 



1568 



INDEX. 



Measure of weights, troy, 1500. 
Measurement of alternating currents, 
26-28. 

of capacity, 63. 

of efficiency, 508. 

of E.M.F., 62. 

of ins. res. of cables, 321. 

of low resistance, 59. 

of mutual inductance, 67. 

of resistance, 56. 

of standard ampere, 10. 

of three-phase power. 72. 
Measures, metrical equivalents, 1500. 
Measuring instruments, elec, 21. 

power in six-phase circuits, 477. 
Mechanical and electrical units, 
table of, 1258. 

air-gap, 363. 

equivalent of heat, 1511. 

interrupters, 1253. 

properties of rubber, 229. 

stoking, 1359. 

symbols, 1. 

units, derived, 2. 
table of, 6. 
Mega-erg, value of, 12. 
Megohm, definition of, 5. 
Melting point of copper, 143. 

point of substances, 1532. 

railway bonds, 773. 
Mercurous sulphate for standard 

cell, 11, 13. 
Mercury and water columns, pres- 
sure of, 1463. 

arc rectifiers, 480. 

for battery charging, 482. 

auto-coherers, 1066. 

for standard cell, 11. 

phys. and elec. prop, of, 138. 

spec. res. of, 132. 

temperature coef. of, 133. 

vapor lamps, 558. 
Merrill on water rheostats, 33. 
Mershon's chart for calculating 

transmission lines, 279. 
Mershon's method, meas. of wave 

form by, 5 . 
Metalized carbon lamps, 549. 
Metal joints in cables, 190. 

pipes, effect of current on, 852. 



Metallic arc lamp, 572. 

circuits in telephony, 1081. 
sheath, capacity of two wires in, 

250. 
sodium, production of, 1241. 
Metals, phys. and elec. prop, of 
table of, 134-140. 
temperature coef. of, 133. 
by fusion of, 1349. 
Meter bearings, 1009. 

commutator type, DC, 997. 
Duncan, 998. 

hysteresis, G. E. type, 102-104. 
Shallenberger, 1028. 
testing formula, 1027. 
Westinghouse, integrating, 998. 
Wright discount, 1008. 
Meters, action of, 1039. 
constants of, 1029. 
direct current, testing of, 1020. 
electric, accuracy of, 997. 
graphic recording, 1036. 
integrating, action of, 997. 
polyphase, service connections of, 
1023. 
testing of, 1020. 
remedy for electrolysis in, 861. 
speeds of, 1029. 
switchboard, list of, 945. 
to feet or inches, 1503. 
types of, 504. 
Methods of lighting, efficiency of, 

594. 
Metrical measures, 1500 to 1504. 
Metropolitan conduit railway sys- 
tem, 837. 
street railway system, 836. 
Mho, value of, 8. 
Mica for commutators, 351. 
puncturing voltage of, 234. 
spec. ind. cap. of, 36, 227. 
Mioanite, spec. ind. cap. of, 227. 
Micro-Farad, definition of, 5, 38. 
Micron, 1500. 

Miles per hour in feet per min., 660. 
Millihenrys of non-magnetic wire, 

241. 
Milliken repeater, 1041. 
Milling machines, power required by, 
1522. 



INDEX. 



156S 



Mill! voltmeter, meas. of cond. with, 
87. 
method, meas. of current by, 78, 
meas. small res. with, 79. 
Mill power, 1462. 
Mils to centimeters, 1503. 
Mineral oils, 1497. 
Miner's inch, 1473. 

water H.P. table, 1475. 
Mines, electric land, 1137. 
Minimum size of high-tension con- 
ductors, 235. 
Mirror galvanometer, 23. 

spec. ind. cap. of, 36. 
Miscellaneous tables, 1499. 
Modulus of elasticity, 1302, 1312. 
of elastic resilience, 1312. 
of rupture of woods, 1317. 
Mohawk type locomotive, 740. 
Moisture in steam, 1394. 
Molecular magnetic friction, meas. 

of, 50 . 
Moment, magnetic, 4. 
of inertia, 1302. 

compound shapes of, 1303. 
table of, 1304. 
of resistance, table of, 1304. 
of rupture of beams, 1309. 
of stress of beam, max., 1309. 
Momentum, definition of, 3. 
Monolithic conduits, des. of, 301. 
Moonlight schedules, 603. 
Moore tube, efficiency of, 566- 

vacuum tube light, 565. 
Mortar, cement, 1293. 

lime, 1293. 
Mortars, 1293. 
Morse code, 1052. 

system, description of, 1040. 
Motive powers, 864. 
Motor brushes, backward lead of, 
353. 
capacity curves, railway, 676. 
car batteries, electrolyte for, 877. 
dimensions of, table of, 732. 
horse-power of, 653. 
characteristics, 685. 
combinations, 760. 
control, Ward Leonard's system, 
354. 



Motor converter, def . of, 503 . 
definition of, 502. 
equipments, weights of A.C., 719. 
field magnets, flux in, 367. 
-generator, definition of, 50 . 
-generators, 434. 
-generator turret turning system, 

1189. 
men, personal factor of, 724. 
operated oil break switch, G. E 

type, 976. 
panel, D.C., equipment of, 928. 
panels, induction, equip, of, 918. 

three-phase synchronous, equip, 
of, 919. 
regulation, test for, 382. 
retraction, gun operation, 1134. 
tests, 394. 

traversing, gun operation, 1134. 
work, variable speed, system for, 

354. 
Motors and dynamos, tests of, 378. 
automobile, 1227. 
boat crane, Navy spec, for, 1194. 
circuit breakers for, capacity of, 

955. 
controlling panels for Navy spec, 

for, 1185. 
counter E.M.F. in armatures of, 

353. 
efficiency curve of, 370. 

of, Navy spec, for, 1185. 

of railway, 803. 

tests of, 395. 
electric railway, 614. 
G.E. railway system, 851. 
induction, starting of, 918. 
ins. res. of, meas. of, 87. 
lubrication of, Navy spec, for, 

1185. 
magnetization curve of D.C., 353. 
Navy spec, for, 1183. 

railway windings of armatures 
for, 348. 
rating of railway, 523. 
rise of temperature in, 378. 
street railway, rating of, 661, 673. 
synchronous, tests of, 399. 

used as condensers, 292. 
temp, rise of, Navy spec, for, 1184. 



1570 



INDEX. 



Motors, test of street car, 392. 
torque of armatures of, 353. 
used to drive machine tools, 1518. 
ventilation fan, Navy spec, for, 
1196. 
Moving body on air resistance, effect 
of, 659. 
-coil galvanometers, 21. 

des. of, 25. 
-needle galvanometers, 21. 
Multicellular voltmeter, cap. test 

with, 326. 
Multi-circuit single winding of 
armature, 342. 
-contact transmitters, 1072. 
-phase transformers vs. single- 
phase, 871. 
-polar machines, armature wind- 
ings for, 345. 
-speed motors, def. of, 504. 
Multiple circuits, current in, 55. 
circuits, res. of, 55. 
conduits, adv. of, 301. 
connection of alternators, 420. 

of batteries, 19. 
control, A.C. railway system, 
710. 
unit switch system, 766. 
duct conduit, constr. of, 301. 
switchboards, 1090. 
telephone system, adv. of, 1094. 
unit control, G.E. type, 712, 761. 
Multiplex armature windings, 347. 
telephony, 1106. 

three-phase lightning arrester, 
988. 
Multiplier, Y-box, Weston, 73. 
Multiplying power of shunt, 29. 
Murray's method, locating faults in 

cables by, 328. 
Mutual inductance, def. of, 236. 
inductance, meas. of, 67. 

secohmmeter method, 69. 
induction, transposition to elimi- 
nate, 285. 
neutralization of capacity and 
inductance, 292. 

National coast defense board, 
recomm. of, 1123. 



National Electrical Code, standard 
conductors, table of, 162. 
Electrical Contractors' Assoc, 
symbols adopted by, 299. 
Natural draft transformers, 448. 
Navy electric fuse, 1137. 
generating sets, 1153. 
special lamps, 1173. 
specifications, 1153. 
standard wires, table of, 174. 
telephone systems, 1206. 
U. S., electricity in, 1153. 
wiring specifications, 1167. 
Neatsfoot oil, spec. ind. cap. of, 37. 
Needle point spark gap curve, 233. 
Negative booster, 790. 
Nernst lamps, descr. of, 562. 

rating of, 540. 
Ness telephone switch, 1118. 
Neutral, grounding of, 478. 

unstable, 479. 
Neutralization of capacity and 

inductance, 292. 
Newburgh telephone system, 1103. 
New York central locomotives, 741. 
Central third rail, 834. 
City, electrolysis in lower, 858. 
lighting table for, 604. 
Niagara-Buffalo Line, arrangement 
of, 290. 
Falls Power Co., manhole constr. 
of, 319. 
Nickel, phys. and elec. prop, of, 
138. 
plating, 1234. 
spec. res. of, 132. 
steel, phys. and elec. prop, of, 

138. 
temperature, coef. of, 133. 
Nickeline, phys. and elec. prop, of, 

138. 
Night sights, electric, 1148. 
Nitrates in electrolyte, test for, 878. 
Nitric acid, spec. res. of, 133. 
Nitrous oxide, spec. ind. cap. of, 35- 
Noark fuses, 1276. 
Non-arcing lightning arresters, 984. 
metal lightning arrester, 989. 
railway lightning arrester, 985. 
Non-inductive load, def. of, 50 s . 



INDEX. 



1571 



Non-inductive load, regulation of 

transformer for, 492. 
-magnetic wires, ind. reactance of, 

table of, 242. 
-magnetic wires, self-induction in, 

239. 
-reversible booster, use of, 893. 
sine wave, equivalent of, 501. 
Northrup instrument, des. of, 26, 

28. 
method, conductivity by, 60. 

meas. ins. res. by, 82. 
Notation, A.I.E.E., 523. 
committee on, table by, 6. 
index, 2. 
used in dynamo and motor 

section, 334. 

Octane, spec. ind. cap. of, 37. 
Octylene, spec. ind. cap. of, 37. 
Oersted, definition of, 5. 

value of, 7. 
Office building plant, economy of, 

1285. 
Ohm, definition of, 5. 

international, construction of, 30. 

def.of, 9. 
per mil-foot, def. of, 131. 
value of, 7, 8. 
Ohmic resistance of storage cell, 883. 
Ohmmeter, direct reading, 57. 

Sage type, 58. 
Ohm's law, 55. 
Ohms, value of various standard, 

131. 
Oil and coal, comparative costs of, 
1358. 
break switch, General Electric 

motor operated, 976. 
circuit breaker, controller, 975. 
breakers, arrangement of, 935. 
breakers, Westinghouse, 969. 
-cooled constant current trans- 
formers, 465. 
transformers, 448. 
flash test of transformer, 500. 
for lubrications, 1497. 
for transformers, specifications 

for, 500. 
!n transformers, use of, 448 



Oil switch, General Electric, 979. 
switches, arrangement of, 933- 
hand operated, electrically 

tripped, 979. 
operation of, 967. 
specifications for, 947. 
use of, 912. 
weight per gallon of, 1497. 
Olive oil, spec. ind. cap. of, 37, 

227. 
Open cars, weight of, 736. 

circuit A.C. armature winding, 

410. 
circuit cells, 15. 
Open circuit in armature, test for, 
402. 
wire circuits, 1082. 
Operating cost of gas and elec. 
cooking, 1260. 
cost of lamps, 554. 
elec. cooking utensils, cost of, 

1261. 
elec. heaters, cost of, 1265. 
Opposition method of testing trans- 
formers, 496. 
Order indicators, U. S. Navy, 1202. 
Oscillating current, definition of, 

502. 
Oscillations, electrical, 1055. 
in ether, 1278. 
undamped, 1068. 
Oscillator, dumb-bell type, 1056. 
Oscillograph, Blondel type, Sk. 
Outer rail, elevation of, 617. 
Outflow of steam, 1416. 

into atmosphere, 1416. 
Output of dynamos, formula for, 
356. 
of motors, test of, 395. 
Outward flow turbines, 1476. 
Over-compounded dynamo, charac- 
teristic of, 340. 
Overhead lines, drop in, 798. 
lines, transposition of, 285. 
railway conducting system, 785. 
trolley construction, cost of, 

629. 
wires, capacity of, 250. 
Overland wires, breaks in, location 
of, 327, 



1572 



INDEX. 



Overload A.C. relay, 962. 

capacities, 521. 

capacity, test of, 381. 

circuit breakers, 899, 950. 

guarantees for machines, 947. 

relay, Westinghouse A.C, 962. 
Overshot water wheels, 1476. 
Overspeeding of rotaries, preven- 
tion of, 961. 
Over-voltage relay, Westinghouse, 

D.C., 962. 
Ozokerite, spec. ind. cap. of, 37, 227. 

Packing* of transmitters, 1074. 
Painting, 1498. 

exposure tests, 1498. 
Palladium, phys. and elec. prop, of, 

138. 
Pan-cake form of winding, 410. 
Panel switchboards, design of, 906. 
Panels, motor controlling, navy spec, 
for, 1185. 
rotary converters, equipment of, 
924. 
Paper insulated cables, carrying 
capacity of, 208. 
cables, joints in, 191. 

tables of, 174-178. 
telephone cables, 188. 
Paper, spec. ind. cap. of, 36, 227. 
Parabolic curves in wire spans, 

charts of, 218. 
Paraffin, spec. ind. cap. of, 36, 227. 
Parallel, condensers in, 63, 324. 
D.C. distribution, size of con- 
ductors for, 284. 
distribution, 277. 
-flow turbines, 1476. 
running of alternators, 419. 
Para rubber, electrical properties of, 

229. 
Parson's steam turbine, 1453. 
Party lines, demand for, 1102. 

telephone lines, 1108. 
Parville method, electric heating, 

1257. 
Passenger elevators, operating cost 

of, 1528. 
Pasted electrode battery, advan- 
tages of, 880 



Pasted plates of storage cells, 880. 
Patent-nickel wire, properties of, 

202. 
Pavement, cost of, 619. 
Paving, cost of, 305, 619. 

depreciation of, 770. 
Peak discharge of batteries, 888. 

of load, batteries to carry, 886. 
Peggendorff cell, 14. 
Penstocks, constr. of, 869. 
Pentane standard lamp, 530. 
Percentage conductivity, 132. 

drop, discussion of, 262. 
Performance diagram, train, 663, 

667. 
Permanent magnetism, def . of, 108. 

magnet voltmeters, 74. 
Permeability curve of arc dynamo, 
338. 
curves of iron and steel, 90. 
of iron and steel, 89. 
value of, 7. 
Permeameter, Drysdale's, use of, 97. 

Thompson's use of, 93-96. 
Personal factor of motormen, 724. 
Petroleum, chemical composition of, 
1356. 
furnaces, 1357. 

oil, spec. ind. cap. of, 37, 227. 
oils, chemical composition of, 
1357. 
Phase-displacing apparatus, 512. 
Phase difference, def. of, 501. 
Philadelphia Inspection Rules for 

boilers, 1332. 
Phillip's code, 1052. 
Phoenix rule for ins. res., 86. 
Phonograph in telephony, use of, 

1096. 
Phosphor-bronze, phys. and elec. 

prop, of, 139. 
Photo-chronograph, Squire-Crehore, 

1133. 
Photometer, Bunsen type, 535. 
Photometers, integrating type, 539. 
Physical constants of copper wire, 
143. 
prop, of alloys, table of, 134-140. 

of metals, table of, 134-140. 
quantities, table of, 6. 



INDEX. 



1573 



Physikalische Reichsanstalt res. 

unit, 30. 
Piles, arrangement of, 1292. 
foundation on, 1291. 
safe load on, 1291. 
Pilot brush, use of, 340. 
Pipe bends, 1431. 

covering, relative value of, 1422. 
flanges and bolts, strength of, 
1431. 
dimensions of, 1430. 
high pressure, screwed, 1430. 
high pressure, shrink, 1432. 
standard, 1433. 
iron, elec. welding of, 1272. 
lines, constr. of, 869. 
riveted hydraulic, wt., safe head, 
1469. 
Pipes, diam. of steam and exhaust, 
diagram of, 1419. 
dimensions of riveted steel, 1467. 
equation of gas, 1418. 

of steam, 1418. 
formula for riveted steel, 1467. 
friction of water in, 1374. 
loss of head due to bends in, 1374. 
riveted steel, 1466.' 
sizes for feed- water, 1373. 
of steam and gas, 1419. 
standard dimensions of extra 

strong, 1427. 
standard dimensions, of wrought 
, iron, 1419. 

thawing by electricity, 1531. 
wooden-stave, 1468. 
Piping, steam, U. S. navy spec, for, 

1163. 
Pitch, specific inductive capacity of, 

227. 
Planers, power required for, 1516. 
Plante cell, advantages of, 880. 
Plate box poles, 632. 

glass, spec. ind. cap. of, 36. 
surface for batteries, area of, 883. 
Plates, appearance of battery, 874. 
buckling of, 881. 

of batteries, cadmium test of, 878. 
safe working prssure for flat, 1332. 
types of, 874. 
Plating baths, 1233. 



Platinoid, fusing effect of current on, 
217. 

phys. and elec. prop, of, 139. 

wire, properties of, 202. 
Platinum, fusing effect of current on, 
217. 

in electrolyte, test for, 877. 

phys. and elec. prop, of, 139. 

silver wire, properties of, 202. 

spec. res. of, 132. 

standard of light, 532. 

temperature coef. of, 133. 

wire, properties of, 202, 
Plow, metropolitan street railway, 
839. 

suspension, 840. 
Plug tube switches, 965. 
Plunger electromagnet, law of, 127. 

electromagnets, shapes of, 128. 

magnets, range of, 130. 
Pneumatic tires, data on, 1225. 
Poggendorff method, comparison of 

E.M.F. by, 77. 
Polar arc, chord of, values of, 371. 

duplex, 1044. 

relay, use of, 1044. 
Polarity of transformer, 495. 
Polarization, def . of, 14. 

of storage cell, 879. 

of X-rays, 1248. 
Polarized bells, biased, 1103. 

constr. of, 1076. 

use of, 1114. 
Pole face, dimensions of, 363. 

faces, shape of, 356. 

line construction, 630. 

lines for high tension work, *>71* 

pieces, faces of, 363. 

transpositions, 1082. 

unit strength of, 4. 
Poles, determination of number of, 
355. 

of induction motor, 426. 

plate box type, 632. 

use of green wooden, 806. 

wooden, contents of, 633. 
Polyphase apparatus, c ; -cuit 
breakers for, 953. 

generator, def. of, 502. 

induction motor, theory of 422. 



1574 



INDEX. 



Polyphase induction motor, power 
of, 423. 
starting torque of, 423. 
induction wattmeters, 1003. 
integrating wattmeters, 1004. 
lines, transposition of, 287. 
meters, connections of, 1026. 
constants of, 1031. 
installation of, 1023. 
service connections of, 1023. 
testing of, 1020. 
motor protected by circuit 
breakers, 954. 
Porcelain, spec. ind. cap. of, 37, 227. 
Portable integrating wattmeters, 
data for, 1016. 
sub-station, 819. 
telephone switchboard, 1141. 
testing battery, 16. 
Portland cement, wt. of, 1293. 
Position indicators, U.S. navy, 1202. 
Post-office wheatstone bridge, 31. 
Potassium chlorate, production of, 
1242. 
cyanide, production of, 1246. 
use of, 1233. 
Potential betw. plates of batteries, 
test of, 878. 
drop in feeders, 788. 
energy, 3. 

measurement of, 40. 
regulator, three-phase induction, 

469. 
regulators, 467. 
def. of, 503. 
rise due to transformers, 479. 
transformers, descr. of, 945. 
Potentiometer, des. of, 47. 

method, E.M.F. of batteries, 63. 
use of, 47. 
Pound, 1499. 
calorie, 1511. 
-degree, C. value of, 12. 
Power ammunition hoists, U. S. 
navy, 1191. 
and light cables, 320. 
Ayrton and Sumpner method for 

meas. A.C., 71. 
carrying capacity in three-phase 
cables, 216. 



Power circuits, res. of, meas. of, 80. 
consumption in factories, 1517. 
consumption of cars, 658. 
curve for railway motors, 669 
curves, altern. current, 70. 

for reducing cost of, 868. 

for trolley cars, 652. 
definition of, 3. 
distribution, discussion of, 262. 

system, A.C. railway, 718. 
electric, def. of, 5. 

meas. of, 50 . 
factor compensation, 1002. 

def. of, 279, 50 . 

in three-phase circuits, 72. 

of transformers, 458. 

varied by use of synchr. motors, 
292. 
for cars, 656. 
house, electrolytic action near, 

862. 
in altern. circuit, meas. of, 69. 
in six-phase circuits, 477. 
international unit of, 10. 
light and heat, in residences, cost 

of, 1287. 
light and heat in isolated plants, 

cost of, 1285. 
lines, transposition of, 285. 
loss, formula for, 265. 

in lead sheath of cables, 293. 

in line, 261. 
mechanical, meas. of, 50 . 
of polyphase induction motor, 

423. 
of water flowing in a pipe, 1462. 
-operated switchboards, 906. 
plants, chimney protection for, 

1281. 
plants, lightning arresters in, 983. 
required for automobiles, 1224. 

for electric cranes, 1527. 

for machine tools, 1516. 
for street railways, 656. 
to drive machinery, 1515. 
station construction, chart of, 
1289. 
depreciation of, 770. 
design of, 866. 
efficiency of machines in, 663. 



INDEX. 



1575 



Power station for railways, 815. 
system, U. S. Navy, 1183. 
three-phase, meas. of, 72. 
to drive machine shops, 1518. 
transmission, classif. of, 864. 
losses in, 1529. 
transformers for three phase, 

478. 
voltage for, 870. 
used by machine tools, 1515. 
Preliminary dynamo dimensions, 

checking of, 363. 
Prepayment wattmeters, 1010. 

wattmeters, Fort Wayne, 1012. 
Pressure gradients, descr. of, 283. 
drop in parallel distribution 

system, 279. 
drop, formula for, 264. 
mean effective steam, table of, 

1442. 
of water to 1000 ft. head., 1465. 
working, for cylindrical shells of 
boilers, 1330. 
Prevention of electrolysis, 861. 
Primary batteries, action of, 14. 
Primer for gun firing, 1213. 
Principle of magnetic circuit, 109. 
Printing machinery, power to run, 
1525. 
plants, electric heat in, 1269-1270. 
Private telephone lines, 1088. 
Production of metals, 1232. 
Projectiles, velocity of, test of, 1128. 
Projectors, search light, 575. 

U.S. Navy, 1179. 
Prometheus system, electric heating' 

1257. 
Prony brake, formula for, 1515. 

test, 395. 
Propagation of waves, 1058. 
Properties of aluminum wire, 194. 
of dielectrics, 227. 
of galv. iron wire, 34. 
of saturated steam, table of, 
1404. 
above a vacuum, 1406. 
of wires and cables, 131. 
Propulsion, electric, Leonard's sys- 
tem of, 354. 
Protected third rail, cost of, 835. 



Protection against high potentials 
on A.C. circuits, 981. 

of buildings from lightning, 1289. 

of chimneys, 1281. 

of steam heated surfaces, 1421. 

of transformers against fire, 871. 

relays, table of, 960. 
Protective relays, 956. 

wires, use of, 982. 
Protectors, telephone, 1088. 
Puffer's modification of Kapp's 
dynamo test, 389. 

test of street car motors, 392. 
Pulleys, 1487. 

rules for, 1487. 

to find size of, 1487. 
Pull of electromagnets, curves of, 
129. 

of electromagnets, formula for, 
110. 

-off curve construction, hangers 
for, 647. 

on armature conductors, formula 
for, 351. 
Pulsating current, definition of, 50,. 
Pulsation, def. of, 505. 
Pump exhaust, 1377. 
Pumping back test of motors, 397. 
test of two dynamos, 388. 

hot water, 1367. 
Pumps, 1367, 1443. 

air, 1445. 

and condensers, 1443. 

double cylinder, sizes of, 1370. 

circulating, 1445. 

single cylinder, sizes of, 1369 

sizes of direct-acting, 1368. 
Puncturing voltage for dielectrics, 
228. 

voltage of mica, 234. 
Pupin telephone system, 1107. 

Quadrant electrometer, 40. 
Quadruplex telegraphy, 1051. 
Quality of light, 600. 

of steam by color of issuing jet, 

1400. 
Quantity of electricity, def. of, 5. 

meas. of, 25. 

symbol of, 8. 



1576 



INDEX. 



Quantity of electricity, unit of, 4. 
Quartz, spec. ind. cap. of, 37. 
Quick break switches, 964. 

Radial brick, bond in, 1340. 

for chimneys, 1341. 
telephone system, 1117. 
Radiation, laws of, 528. 

of heat in ducts, 214. f 
Radiators and convectors, 1263. 
Radioscopic images, examination of, 

1255. 
Radius of curvature, 616. 
of gyration, 1303. 

compound shapes, 1303. 

table of least, 1304. 
Rail bonds, testing of, 801. 
curvature, 616. 
joints, testing of, 801. 
Potter type, 830. 
testers 802. 
welding, electric, 1273. 

thermit system, 778. 
Rails and bonded joints, rel. value 

of, 780. 
electrolytic action on, 855. 
impedance of steel, 795. 
ingredients of, 780. 
resistance of, 821. 
specifications for, 830. 
weight of, 615. 
Railway booster calculations, 809. 

system, 807. 
bonds, requirements for, 775. 

types of, 772. 
circuits, drop in, 796. 

testing drop in, 804. 

tests of, 798. 
conductors, dimensions of, 791. 
conduit systems of, 835. 
depreciation, table of, 770. 
electric, system of operating, 613. 
energy of electric, 706 
equipments compared, 719. 

weights of, 730. 
machinery, depreciation of, 770. 
motor characteristics, 685. 

combinations, 760. 
motors, 614. 

A.C. type, 707. 



Railway motors, armature windings 
of, 348. 
capacity of, 673. 
characteristic curves for, 664. 
efficiency of, 803. 
installation of, 745. 
rating of, 523. 
selection of, 52?. 
speed-time curve for, 669. 
standard sizes of, 729. 
test of, 397. 
temperature of, 675. 
torque of, 731. 
non-arcing lightning arresters, 

985. 
overhead conductors, 785. 
power station, 815. 
service boosters, 813. 
shop, power required in ideal, 

1521. 
speed and energy curves, 680. 
sub-stations, equipment of, 942. 
system, load factor of, 785. 
ties, durability of, 619. 
turnouts, 620. 
Rake of poles, 633. 
Range finder, Fiske, 1211, 
finders, lights for, 1148. 
indicators, U. S. Navy, 1204. 
of carbons, 577. 
of solenoids, 130. 
Rape-seed oil, spec. ind. cap. of, 

37. 
Rapid fire guns, firing mechanism 

for, 1149. 
Rated terminal voltage, def . of, 515 . 
Rate of acceleration, 666. 

of deposit, 1235. 
Rates, gas and electric, comparison 
between, 1261. 
of charge of batteries, 883. 
of discharge of batteries, 883. 
of storage batteries, 874. 
Rating of fuse wires, 507, 1275. 
of generators or motors, 506. 
of illuminants, 540. 
of railway motors, 661, 673, 729. 
Ratio of transformers in three-phase 
system, 471. 
test of transformer, 491. 



INDEX. 



1577 



Rayleigh's method, E.M.F. of 

batteries, 62. 
Reactance coil for A.C. arc cir- 
cuits, 466. 

factors, table of, 266. 

of three-phase line, inductive, 
245. 

'of transmission circuits, 238. 

symbol of, 8. 

-voRs for A.C. lines, 280. 
Reaction of alternator armatures, 
414. 

of armatures, 350, 364. 
Reactive coils, use of, 982. 

factor, def. of, 505. 
Reactors, def. of, 503. 
Reading, illumination for, 602. 
Receiver, Bell telephone, 1070. 

capacity, 1443. 

with detector, 1065. 
Receivers, coherer with jigger, 1064. 

wireless telegraph, 1063. 
Recording meters, Bristol, 1036. 

wattmeters, Duncan, 1000. 
G. E., testing, 1030. 
Thomson, 998. 
Records of temperature test, 381. 
Rectifying apparatus, losses in, 

meas. of, 512. 
Reduced deflection method, res. of 

batteries by, 60. 
Reed method, electric heating, 1257. 
Refined iron, qualities of, 824. 
Refineries, copper, 1238. 
Refining of copper, 1235. 

of metals, 1232. 

of silver, 1238. 
Reflecting galvanometer, Kelvin 

type, 23. 
Reflections, coefficients of table of, 

593. 
Regulating battery, 888. 

devices for induction motors, 428. 

reactance coil, 466. 

relays, 956. 
Regulation, importance of, 545. 

of arc lamps, 576. 

of dynamos, test for, 382. 

of generators, 870. 

of electrical machines, 513. 



Regulation of transformers, 458. 
by calculation, 492. 
comparative, 455. 
table of, 498. 
test of, 491. 
of voltage of transformers, 452. 
Regulations of Board of Trade, 781. 
Regenerative X-ray tubes, 1251. 
Regulators for A.C. generators, 409. 
for separate circuits, 469. 
of potential, 467. 
three-phase induction potential, 
469. 
Reinforced concrete, 1292. 
Relative conductivity, 132. 

efficiency of large and small trans- 
formers, 459. 
Relay, General Electric A.C. over* 
load, 961. 
low voltage A.C, 962. 

D.C., 961. 
overload, A.C, 962. 
over- voltage, D.C, 960. 
reverse-phase A.C, 962. 
underload D.C, 962. 
Westinghouse A.C. overload, 962. 
D.C. over- voltage, 962. 
time limit, 960. 
Relays, auxiliary, 956. 
classification of, 955. 
commonly employed, 960. 
definite time limit, 956. 
instantaneous, 956. 
inverse time limit, 956. 
protection of A.C systems by, 959. 
protective, 956. 
regulating, 956. 
reverse current, 961. 
signalling, 955. 
Reliability of service, switchboards 

built to insure, 929. 
Reluctance, definition of, 5. 

value of, 7. 
Reluctivity, definition of, 5. 

value of, 7. 
Remedies for electrolysis, 861. 
Remote control panel switchboard, 
906, 928. 
control switches for equalizer cir- 
cuits, 962. 



1578 



INDEX. 



Removal from service of storage 

batteries, 881. 
Renewals of lamps, 547, 556. 
Repeater, Atkinson, 1048. 

duplex, 1049. 

Ghegan, 1042. 

Milliken, 1041. 

Weiny-Phillips, 1043. 
Repeaters, use of, 1041. 
Repulsion motor, def. of, 502. 
Reservoirs, storage, 867. 
Residential plant, cost of maint. of, 
1287. 

plant, installation of, 897. 
Residual magnetism, def. of, 108. 
Resin, spec. ind. cap. of, 37. 
Resistance box, decade type, 32. 

control of battery discharge, 891. 

curves on air, 659. 

definition of unit of, 5. 

due to gravity, 1224. 

for arc lamps, 581. 

high voltmeter, 75. 

In overhead lines, 798. 
returns, 798. 

In rotor of induction motors, 428. 

In stator of induction motors, 
429. 

low, meas. of, 59. 

magnetic, definition of, 5. 

meas. of, with ohmmeter, 57. 
with volt and ammeter, 78. 

measurements, 56. 

of A. C. circuits, 259. 

conductors, effective, 238. 

of aerial lines, 61. 

of aluminum wire, 194, 196. 

of armature, meas. of, 401. 

of batteries, 60. 

of bonds, 776. 

of brushes, 362. 

of cables, meas. of, 330. 

of carbons, 577. 

of cells, internal, 20. 

of conductors, 61. 
table of, 266. 

of copper wire, table of, 148. 

of dilute sulphuric acid, 1229. 

of Driver-Harris wire, 207. 

of field coils, meas. of, 401 



Resistance of galvanometers, 60. 

of German silver wire, 203. 

of gutta-percha, 231. 

of house circuits, 61. 

of light and power circuits, meas* 
insulation, 80. 

of multiple circuits, 55. 

of plating bath, 1235. 

of rails, 821. 

of steel, 825. 

of storage batteries, 883. 

of stranded aluminum wire, table 
of, 198. 

of sulphate of copper, zinc, 1231. 

of track rails, 779. 

of transformer, meas. of, 486. 

of trolley and track, 798 

of water rheostats, 33. 

of wiring system, insulation, 82. 

of working batteries, 61. 

practical standard of, 30. 

specific, 131. 
magnetic, 5. 

symbols of, 7. 

table of galv. iron wire, 34. 

temperature coefficient, 133. 

to traction, 1225. 

type furnace, 1244. 

unit of, 4, 131. 

variation with temperature of, 228. 

-volts for A.C. lines, 280. 

wires, properties of, 202. 
Resistances, high, meas. of, 79. 

small, meas. of, 79. 
Resisting moment of beams, 1308. 
Resistivity, definition of, 9. 

symbol of, 8. 
Resonance, curves of, 1216. 

theory of, 1215. 
Retardation, rate of, 668. 
Retentiveness, def. of, 108. 
Retraction motor for gun operation, 

1134. 
Return booster system, 808. 

call bell system, 293. 

circuit, 771. 

current, division of, 800. 

drop of ground, test of, 799. 
Returns, drop in, 798. 

regulation for railway, 781. 



INDEX. 



1579 



Reverse current circuit breaker, 950. 
current relay, 961. 
-phase A.C. relay, 962. 
Reverser, multiple unit system, 762. 
Reversible booster, use of, 894. 
Reversing current in armatures, 351. 
Revolution indicators, U. S. Navy, 

1204. 
Revolving field alternators, 409 
Rheostatic controller, 754. 

controllers, list of, 756. 
Rheostats, temperature rise in, 520. 

water, 33. 
Right of way for pole lines, 871. 
Ring armature, windings of, 342. 
down trunks, 1096. 
method, determ. magn. values by, 

91. 
type armatures, 341. 
Ringing keys, 1090. 
Rise and grades, 617= 

of potential due to transformers, 

479. 
of temperature in armatures, 349, 
358. 
of commutator, 362. 
in dynamos, test of, 378. 
in field coils, 352. 
in transformers, test of, 483, 

491. 
in transformers, 447, 498. 
meas. of, 518. 

U. S. Navy generators, 1158. 
Ritchie's photometer, 536. 
Riveted bonds, 774. 
Roadbed, depreciation of, 770. 
Road surface material, 1225. 
Rock, foundations on, 1290. 
salt, spec. ind. cap. of, 37. 
Rodding of cables, 319. 
Rod float gauging, theory of, 1471. 
Rods, lightning, installation of, 1278. 
Roebling galv, telegraph wire, prop- 
erties of, 200. 
steel telegraph wire, properties of, 

201. 
wire gauge, 141. 
Rolling stock, depreciation on, 

770. 
Room lighting, data on, 597. 



Rope driving, 1490. 
hemp, wt. of, 1494. 
horse-power of transmission, 1492. 
manila, velocity of, table of, 1492. 
wt. and strength of, 1494. 
Ropes and belts, slip of, 1493. 
horse-power of manila, 1491. 
of manila, diagram of, 1492. 
strain from loads on inclined 
planes, 1494. 
Rosa curve tracer, 51. 
Rosendale cement, wt. of, 1293. 
Rosin, specific inductive capacity of, 

227. 
Rotaries, overspeedingof , prevention 
of, 961. 
starting diagram of connections 

for, 920. 
starting of, 440. 
Rotary compensator turret turning 

system, 1189. 
Rotary converter circuit protection 
by relays, 959. 
def . of, 503. 

panel, General Electric D. C, 
925. 
equipment of, 919, 924. 
sub-station, 816. 
Rotary converters connected to 
transformers, 442, 476. 
descr. of, 436. 
for six-phase system, 475. 
in sub-stations, 814. 
starting, diagram of connections 

for, 920. 
voltage between collector rings 
of, 439. 
Rotary field of induction motor, 425. 
induction apparatus, temp, rise 

in, 520. 
transformers, armature windings 
for, 441. 
Rotating field in wattmeters, 1000. 
Rotation of conductors around pole, 

109. 
Rotor, core of, 425. 
definition of, 423. 
resistance in, 428. 
slots, number of, table of, 427. 
windings, commutated, 429. 



1580 



INDEX. 



Rowland method, determ. magn. 

values by, 91. 
Rubber covered cables, carrying 
capacity of, 208. 
wire and cables, prop, of, 161. 
underwriters' test of, 161. 
Rubber, electrical properties of, 229. 
insulated cables, carrying capac- 
ity of, 210. 
cables, data on, 214. 
telegraph cables, 189. 
wires and cables, tables of, 164- 
172. 
insulation test of, 230. 
specific inductive capacity of, 227. 
tires, data on, 1225. 
Rules for conductingboiler tests, 1384. 
Rumford's photometer, 536. 
Ryan electrometer, 51. 
Ryan's method, meas. of wave form 
by, 51. 

Sad irons, elec, cost of operating, 

1263. 
Sag and tension in wire spans, 218. 
for aluminum wire, limit of, 225. 
in wire spans, calc. of vertical, 222. 
Sage direct reading ohmmeter, 58. 
Safe load on wooden beams, chest- 
nut, 1319. 
hemlock, 1319. 
southern pine, 1320. 
spruce, 1318. 
white cedar, 1319. 
white pine, 1318. 
yellow pine, 1319. 
load on brickwork, 1322. 

on steel beams, 1310. 
temperature for field coils, 352. 
Safety valves, 1382. 

Philadelphia rules, 1383. 
rules for pop valves, 1383. 
rules governing, 1382. 
Saline solutions, conducting power 

of, 905. 
Salt solution for water rheostats, 34. 
Sand and cement, A.S.C.E. recom- 
mendations, 1294. 
and cement, fineness of, 1294. 
foundations on. 1290. 



Sandstones, crushing load, 1323. 
Sangamo integrating meter, 1006. 

wattmeters, testing of, 1035. 
Saturation factor, def. of, 505. 

test of dynamos, 400. 
S.B. resistance wire, 207. 
Scale, galvanometer, 24. 

solubility of, 1363. 
Scales, instrument, figuring of, 946. 
Schedule for 35-ton car, 658. 
Schmidt chronoscope, 1131. 
Schuckert searchlights, 1123. 
Schultz chronoscope, 1130. 
Scott method of connecting convert- 
ers and transformers, 477. 
Screwed contact, current density 

for, 442. 
Searchlight carbons, 579. 

projectors, 575. 
Searchlights, data on, tables of, 1127. 

intensity of light of, 1125. 

mirrors of, 1125. 

Schuckert type, 1123. 

use of, 1123. 

U. S. Navy, spec, for, 1179. 
Secohmmeter, meas. mutual ind. 

by, 69. 
Secondary current, transformers 
for constant, 462. 

standards, checking of, 1013. 
Second, definition of, 2. 
Sectional rail, Westinghouse rail- 
way system, 846. 
Sections, elements of usual, 1303. 

of trolley system, laying out, 785. 
Seeley's cable connectors, 190. 
Segments, commutator, number of, 

361. 
Selective telephone systems, 1102. 
Selenium, spec. ind. cap. of, 37. 

spec. res. of, 132. 
Self-inductance, meas. coef. of ind. 
by, 65. 

with altern. current, meas. of, 66 
Self-induction, coefficient of, 64. 

def. of, 238. 

formula for, 239. 

in solid iron wire, table of, 248. 

in stranded wires, 241. 

of transmission circuits, 238. 



INDEX. 



1581 



Self-induction standard, Ayrton and 

Perry's, 66. 
Separate circuit regulators, 469. 
Separately excited dynamo, 338. 
Separating calorimeter, 1398. 
Separators, steam, 1380. 
Series A.C. regulator, G.E. type, 466. 

boosters for railway service, 813. 

commutator A.C. motor, 503. 

condensers in, 63, 324. i 

connection of batteries, 19. 

dynamo, descr. of, 336. 

ext. characteristic curve of, 337. 

limit switch for railway control, 
769. 

multiple switchboards, 1092. 

parallel controller, 753. 
controllers, list of, 755. 

party lines, 1108. 

telephone system, 1076, 1109. 

transformers, 464. 
Service box cover, cut of, 315. 

box, def. of, 301. 

boxes, constr. of, 302. 

capacity of railway motors, 675. 

connection of polyphase meters, 
1023. 

meter, tests of, 1015. 

reliability, switchboards built to 
insure, 929. 
Sesame oil, spec. ind. cap. of, 37. 
Sewer connections, cost of, 303. 
Sewing machine, power to run, 1525. 
Shafting, centers of bearings of, 
1483. 

deflection of, 1482. 

hollow, 1485. 

horse-power of iron, 1481. 
tables of, 1484. 

laying out, 1485. 

pulleys, belting, rope driving, 
1481. 
Shafts, armature, 341. 

hollow, 1485. 
Shallenberger meter, testing of, 1028. 
Shallow trenches, manhole constr. 

for, 319. 
Shape of moving body, effect of, 659. 

of pole faces, 356. 
Shapers, power required for, 1520. 



Sharp-Millar's pnotometer, 539. 
Shawmut soldered bond, 772. 
Shearing strength of woods, 1316. 
Shear, vertical-beams, 1308. 
Sheathing core, formula of, 142. 
Sheath, metallic, capacity of wires in, 

251. 
Sheet metal, permeability of, 89. 
Sheldon method, meas. low res. by, 

59. 
Shellac, spec. ind. cap. of, 37, 227. 
Shell type transformers, coils for, 

444. 
Shelves for bus-bars, 933. 
Ship, condensation of steam in pipes 

aboard, 1415. 
Ships, dynamos in, gyrostatic action 

on, 353. 
Shoes, cast iron magnet, 352. 

third rail, 832. 
Short circuit in armature, test for, 
402. 
connection winding of armatures, 
343. 
Shunt booster, use of, 892. 
boxes, galvanometer, 29. 
dynamo, external characteristic of, 
339. 
internal characteristic of, 339. 
dynamos, regulation tests of, 382. 
winding of compound wound 

machine, 369. 
wound dynamos, des. of, 336. 
Shunted detector, 1065. 
Shunts, ammeter, 41. 
Shut-down of plant, provision 

against, 929. 
Side brackets for trolley line, 635. 
Siding suspension, 638. 
Siemens' electro-dynamometer, 42. 

ohm, value of, 131. 
Sights, night, electric, 1148. 
Signal corps wireless telegraphy, 
1145. 
lights, U. S. navy, 1181. 
stranded wire, galv., properties of 

200. 
system, requirements of, 623. 
Signalling, automatic Mock. 622. 
relays, 955. 



1582 



INDEX. 



Signalling, syntonic, 1059. 
Silicon-bronze, phys. and elec. prop. 

of, 140. 
Silt, effect on storage of, 869. 
Silver, phys. and elec. prop, of, 139. 

plating, 1234. 

refining of, 1238. 

spec. res. of, 132. 

temperature coef. of, 133. 

voltameter, description of, 10. 
Simplex system, electric heating, 

1257. 
Sine curve, discussion of, 404. 

wave, def . of, 507. 
Single conductor cables, watts per 
foot lost in, 212. 

conductor cable cambric ins., 
tables of, 179-183. 

conductor wire table, U. S. navy, 
1170. 

contact transmitters, 1071. 

duct conduit, adv. of, 301. 

overhead wire, capacity of, 250. 
Single-phase A.C. motors, 421. 

A.C. railway system, 707. 

A.C. sub-station, views of, 943. 

air-blast transformers, 452. 

armature winding, 411. 

circuit, charging current per 1000 
feet of, 253. 

circuits, self induction in, 239. 

feeder panel, equipment for, 916. 

induction wattmeters, 1003. 

line, capacity effect in, 249. 

potential regulators, 467. 

railway, distribution system for, 
718. 

railway motor characteristics, 713. 

rotary converter, 436. 

transformer connections, 472. 

transformers vs. multi-phase, 871. 

transmission circuit, calc. of, 280. 

wiring examples, 272. 
Single truck cars, power for, 656. 
Six-phase, changing three-phase to, 
475. 

circuits, power in, 477. 
Size of conductors for parallel D. C. 
distribution, 284. 

of generator units, 870. 



Sizes of carbons, 578. 

of railway motors, 729. 
S.K.C. high voltage testing set, 461. 

lightning arrester, 990. 
Skin effect, 1061. 
def. of, 236. 
factors, table of, 237. 
Slate cut-outs, res. betw. terminals 
of, 86. 
for switchboards, 907. 
Slawson's signal block system, 627. 
Slide-wire bridge, 58. 
Sliding trolley collector, 644. 
Slip of induction motor, table of, 
425. 
of ropes and belts, 1493. 
Slipper shoe for third rail, 833. 
Slot sizes, armature, values of, 372. 
Slots in field-frame of induction 
motor, 426. 
of armature cores, design of, 357. 
Slotted or toothed type armatures, 

341. 
Slotters, power required for, 1520. 
Smashing point, def. of, 540. 
Small resistances, meas. of, 79. 
Smelting by Stassano process, 1274. 
electric, 1247. 
def. of, 1232. 
Smooth body armatures, advantages 

of, 341. 
Sneak current protector, 1088. 
Soapstone for switchboards, 907. 
Sodium, cyanide of, production of, 
1246. 
hydrate, production of, 1239. 
production of, 1241. 
Soft iron ammeters, 41. 
Soldered bonds, test of, 773. 

types of, 772. 
Soldering irons, electric, 1270. 
Solenoids, characteristics of, curves 
of, 129. 
coefficient of self ind. of, 65. 
pull of iron-clad, 127. 
tractive effort of, 130. 
Solid back transmitters, 1072. 
copper wire, G. E. Co., prop, of, 
table of, 162. 
prop, of, table of, 154. 



INDEX. 



1583 



Solid tires, data on, 1225. 

Solids, spec. ind. cap. of, table of, 

36, 37. 
Solubilities of scale-making mater- 
ials, 1363. 
Sound, propagation of, 1069. 
Sources of light, intrinsic brightness 

of, 529. 
Space occupied by D.C. cov. wire, 
table of, 123-126. 
occupied by S.C. cov. wire, table 

of, 121-123. 
required by turbines vs. recipro- 
cating engines, 1454. 
Spacing of beams for various loads, 

1315. 
Span construction, 644. 
wire, dip in, 634. 
material for, 635. 
Spans, chart for long, 220. 
chart for short, 221. 
tension and sag in wire, 218. 
Spark gap curve, 233, 462. 
gap, meas, 517. 
points, consir. of, 517. 
Sparking at commutator, 805. 
at switches, 948. 

distance across needle points, 462. 
distances, table of, 526. 
of brushes, 805. 
Sparks, chemical effect of electric, 
1232, 
length of, curves of, 949. 
Special cables for car wiring, prop, 
of, 173. 
lamps, navy, table of, 1178. 
Specifications for det. ampere, 10. 
for det. intern, volt, 10. 
for paper ins. telegraph cables, 

189. 
for paper ins. telephone cables, 

188. 
for submarine cables, 189. 
for switchboards, 947. 
for 30 per cent rubber compound, 

229. 
for telephone cables, 1083. 
for transformer oil, 500. 
for transformers, 498. 
U.S. Navy, 1153 



Specifications for wiring, U. S. Navy, 

1167. 
Specific conductivity, 132. 

energy dissipation in arm. core, 

107. 
gravity and unit weights, tables 

of, 1513. 
gravity, table of, 1512. 
heat, mean, of platinum, 1509. 
of gases and vapors at con- 
stant pres., 1511. 
of water, 1511. 
heats of metals, 1509. 
inductive capacity, 4, 38. 
measurement of, 38. 
of dielectrics, 227. 
of gases, table of, 35. 
of liquids, table of, 37. 
of solids, table of, 36, 37. 
magnetic resistance, 5, 7. 
resistance, 131. 

of conductors, table of, 132. 
of liquids, table of, 133. 
thermal conductivity of dielec- 
trics, 234. 
Speech, definition of, 1069. 
Speed and energy curve, 680. 
curves of railway motors, 686. 
error table for wattmeters, 1032. 
headway and number of cars, 660. 
of cars, diam. of wheels to obtain 

certain, 655. 
of dynamos, formula for, 356. 
of induction motors, 424. 
of power generators, 870. 
of wattmeters, 1029. 
recorders, U. S. Navy, 1212. 
run of N. Y. C. locomotive, 743. 
-time curve, 667. 
Spendersf elds line, details of, 651 . 
Spermaceti, spec. ind. cap. of, 37. 
Sperm oil, spec. ind. cap. of, 37. 
Spherical candle power of lamps, 
540. 
reduction factor, 525. 
Spiegeleisen, phys.and elec.prop. of, 

137. 
Spikes, table of, 618. 
Spitting-off discharges, 1278. 
Sprague multiple unit control, 761. 



1584 



INDEX. 



Spring jacks, use of, 1089. 

Square roots, table of, double, 45, 46 

Squire-Crehore photo-chronograph, 

1133. 
Squirrel-cage induction motors, rotor 

slots for, 427. 
Staggering trolley, 644. 
Standard candle, 530. 

cell, construction of, 11. 
description of, 10, 19. 
filling of, 13. 

used with potentiometer, 47. 
condensers, construction of, 38. 
conductors, N. E. C, prop, of, 

table of, 132. 
copper wire strands, prop, of, 

table of, 159. 
of resistance, construction of, 30. 
of self-induction, Ayrton and 
Perry's, 66. 
symbols for wiring plans, 299. 
Standardization rules A.I.E.E., 500a, 
Standards of light, 530. 
Stanley lightning arrester, 990. 
Star connected armature windings, 
413. 
connection of transformer, three- 
phase, 473. 
of winding, 404. 
Starting current test of synchronous 
motors, 400. 
devices for induction motors, 428. 
induction motors, methods of, 918. 
of rotaries, 440. 
rotary converters, diagram of 

connection for, 920. 
torque of polyphase induction 
motor, 423. 
Stassano process for elec. welding, 

1274. 
Static dischargers, 992. 

ground detectors, installation of, 

942. 
interrupter, 993. 

machines, use for X-ray of, 1252. 
transformer, def. of, 443. 
wave, action of, 993. 
Stationary impedance of induction 

motors, 398. 
Stator. core of, 425. 



Stator, definition of, 423. 

resistance in, 429. 
Stays, boiler head, 1333. 
Steady strain discharges, 1278. 
Steam, 1327. 

Steam boiler, efficiency of, 1329. 
settings, 1334. 
measurements of, 1336. 
strength of riv. shell, 1330. 
Steam boilers, cylinders of, 1327. 
flues of, 1327. 

gas passages and flues of, 1329. 
grate surface per h.-p. of, 1329. 
heating surface of, 1328. 
tubes of, 1328. 
per h. p., 1329. 
hor. return tubular, 1327. 
setting of, 1335. 
horse-power of, 1327. 
points in selecting, 1327. 
scotch or marine, 1327. 
types of, 1327. 
vertical fire tube, 1327. 
water tube, 1327. 
working pressure of, 1330. 
Board of Trade rule, 1332. 
Philadelphia rule, 1332. 
U. S. statutes, 1332. 
Steam engines, 1434. 

and dynamos, standards of, 

1435. 
brake horse-power of, 1440. 
cylinder ratios of, 1441. 
horse-power of, 1440. 
ind. hor3e-power of, 1440. 
mean effective pressure table of, 

1442. 
nominal horse-power of, 1440. 
receiver capacity of, 1443. 
regulation of, 514. 
tests of various types of, 1413. 
Steam, flow through pipes of, 
1417. 
flow to atmosphere of, 1416. 
to lower pressures of, 1416. 
heating, boiler horse-power, 1415 
moisture calorimeter diagram. 
1397. 
in, determination of, 1394. 
tables of, 1396. 



INDEX. 



1585 



Steam pipe covering, cost and heat 
loss of, 1423. 
electrical tests of, 1422. 

diagram of, 1423. 
heat loss in, 1423. 
miscellaneous substances for, 

1425. 
relative economy of, 1424. 
value of, 1422. 
Steam pipes, 1417. 

condensation in, 1415. 
aboard ship, 1415. 
heating, 1415. 
loss of heat from, 1421. 
Steam piping, U. S. navy spec, for, 
1163. 
ports and passages, 1443. 
properties of saturated, 1404. 

1-15 lbs. abs., 1404. 
quality by color of issuing jet, 

1400. 
separators, 1380. 
superheated, 1413. 
table, DeLaval turbine, 1458. 
total heat of, 1511. 
Steam turbine, 1451. 
Curtis, 1455. 
DeLaval steam flow, table of, 

1458. 
tests of, 1452. 
Parsons, 1453. 

vanes in Westinghouse-Parsons, 
1453. 
Steam turbines, relative floor space 
of, 1454. 
relation of foundation to h.-p. of 

1457. 
U. S. Navy spec, for, 1160. 
Steam, volume of, tables of, 1404. 

weight of, tables of, 1404. 
Steel and iron, ageing of, 455. 
elec. welding of, 1271. 
magnetic fatigue of, 455. 
permeability curves of, 90. 
wire, constants of, 199. 
Steel chimneys, brick lining of, 1343. 
cost of, 1343. 
foundation size of, 1343. 
field magnet yokes, 352. 
for third rail, qualities of, 822 



Steel frame buildings, electrolysis in, 
859. 
magnetic qualities of, 91. 
permeability of, meas. of, 94. 
poles, 633. 

weight of, 633. 
production of, 1247. 
rails, 825. 

impedance of, 795. 
resistance of, 825. 
strand wires for trolleys, 642. 
telegraph wire, properties of, 201. 
weight of, 1294. 
wire, properties of, 199, 201. 
use in telephony of, 1082. 
Steering-gear, navy spec, for, 1200. 
Steinmetz hysteresis formula, 98. 
Step-by-step method, hysteresis 
tests by, 101. 
telephone systems, 1102. 
Step-down transformers for Y-dis- 

tributions, 478. 
Stepping-down arrangement for long 

distance transmission, 474. 
Stepping-up arrangement for long 

distance transmission, 474. 
Stern's duplex, 1050. 
Stillwell potential regulator, 467. 
Stoking, mechanical vs. hand firing, 

1359. 
Stone, crushing load of, 1322. 

foundations, 1293. 
Stop watch, use in meter tests of, 

1015. 
Stops of car, table of frequency of, 

658. 
Storage batteries, automobile, 1227. 
capacity of, 874, 883. 
care of, 1228. 

central station, three-wire sys- 
tem, 903. 
charge and discharge rates of, 

883. 
charging of, 880. 
connections for charging, 899. 
constant current, booster sys- 
tem, 901. 
dimensions of, 883. 
discharge rate of, 874. 
efficiency of, 879. 



1586 



INDEX. 



Storage batteries, elements of, 872. 

erection of, 884. 

installation of, 885. 

internal resistance of, 883. 

load regulation by, 888. 

loss of charge of, 884. 

polarization of, 879. 

removal from service of, 881. 

requirements of, 874. 

sulphation of, 881. 

tests of, 882. 

theories of, 872. 

three- wire system, 899. 

to carry load peak, 886. 

troubles of, 881. 

uses of, 886. 

variation of efficiency of, 884. 

voltage curves of, 883. 

weight of, 882. 
Storage battery booster equipment, 
902. 

boosters, circuit breakers pro- 
tecting, 952. 

capacity, 900. 

discharge, control of, 891. 

plant, installation of, 897. 

plates, cadmium test of, 878. 

types of, 874. 
Storage reservoirs, 867. 
Stoves, car, cost of operating, 1266. 
Strains in ropes on inclined planes, 

1494. 
Strain test, 381. 
Stranded conductor, G. E. Co., 

table of, 163. 
copper conductors, carrying cap. 
of, 209. 

wire, prop, of, table of, 155. 
weather-proof aluminum wire, 197. 
wires, self induction of, 241. 
Strain, 1301. 
Strands, standard copper, prop, of, 

table of, 159. 
table of wire, 142. 
Stray power of dynamo, calculation 
of, 391. 

test of motor, 396. 
Streams, estimating, 869. 
St^«t car equipments, compared, 
7 lb. 



Street car heating, electric, 1265. 
cars, lighting of, 806. 

possible schedule for, 658. 
excavation per conduit foot, cost 

of, 306. 
lighting by arc lamps, 582. 
Street railway booster system, 807. 
circuits, test of, 798. 
material required for one mile of, 

628. 
motor characteristics, 713. 

control, Leonard's system of, 

354. 
testing, 803. 
motors, armature windings of, 
348. 
capacity of, 673. 
characteristic curve of, 664, 686. 
efficiency of, 663, 803. 
rating of, 661. 

service capacity curves of, 676. 
speed-time curve for, 669. 
test of, 392, 397. 
power station, 815. 
Street railways, depreciation on, 
table of, 770. 
power required for, 656. 
Strength of current, meas. of, 78. 
of dilute sulphuric acid, table 

of, 904. 
of materials, 1301. 
of riveted shell, boiler, 1330. 
of wire ropes, 1325. 
Stress, 1301. 
Strut bars, 1314. 

Submarine and underground cables, 
tests of, 321. 
cables, 189, 1083. 
testing of, 331. 
Submerged rheostats, wire for, 34. 
Sub-station design, 814. 
for railways, 815. 
portable type, 819. 
rotary converter, 816. 
single phase A.C., views of, 
943. 
Sub-stations, drop between, 794. 

equipment of, 942. 
Substitution method, res. meas. by, 
56. 



INDEX. 



158? 



Suburban cars, types of, 612. 
Sulphate of copper, res. of, 1231. 
of lead, use of, 873. 
of zinc, res. of, 1231. 
Sulphation of storage batteries, 881. 
Sulphur dioxide, spec. ind. cap. of, 
35. 
spec. ind. cap. of, 37. 
Sulphuric acid, conducting power of, 
table of, 905. 
resistance of, 1229. 
spec. res. of, 133. 
strength of, table of, 904. 
Sumpner's test of copper loss in 
transformers, 497. 
of iron loss in transformers, 
496. 
Superficial measures, metrical equiv. 

1501. 
Superheated steam, 1413. 

economy of engines using, 1413. 
Superheaters, 1413. 
Supplies, approx. list of electric 

work, 1531. 
Supplying losses, electrical method 

of, 389. 
Surface contact plates, G. E. railway 
system, 848. 
railway, G. E. system, 847. 
railway system, 840. 
shoes, G. E. railway system, 
850. 
Surface insulation against electro- 
lysis, 862. 
measures of, 1499. 
Susceptance, capacity, table of, 269. 

symbol of, 8. 
Susceptibility, magnetic, definition 
of, 5. 
value of, 7. 
Suspended wires not on same level, 

sag in, 223. 
Suspension brackets, 635. 

of trolley wires, 637. 
Swapping of current, 859. 
Swedish iron rope wire, 1325. 
Switchboard, definition of, 906. 
instruments, 940. 

list of, 945. 
meters, list of, 945. 



Switchboards, A.C. and D.C., ro- 
tary converter panels for, 924. 

A.C. panels for, 912. 

aluminum bars for, 911. 

arc, General Electric, 922. 

central station, electrically op- 
erated, 928. 
panels for, 907. 

connections on, 910. 

constant current transf. panels 
for, 922. 

controlling, 940. 

copper bars for, 909, 911. 

D. C. exciter, 942. 
feeder panel for, 928. 
generator panel for, 924. 
motor panel for, 928. 

direct control panel, 906. 

electrically operated, 929. 

for battery plants, 898. 

for hydro-electric plant, 931. 
for transmission plants, 870. 

frames for, 908. 

General Electric D.C., rotary con- 
verter panel for, 925. 

generator, U. S. Navy, 1163. 

hand-operated, 906. 
remote-control, 928. 

illuminating lamps for, 909. 

induction motor panels for, equip, 
of, 918. 

insulation distances on, 912. 

isolation of conductors on, 929. 

material for, 907. 

panel, design of, 906. 

power-operated, 906. 

reliability of service insured by, 929. 

remote control panel, 906. 

space behind, 907. 

specifications for, 947. 

single-phase panel for, equip- 
ment of, 916. 

sub-station, equipment of, 942. 

telephone, common battery, 1098. 
design of, 1089. 
multiple, 1090. 
portable, 1141. 
series multiple, 1092. 

temperature rise of devices on, 
910. 



1588 



INDEX. 



Switchboards, three-phase panels for 
912. 
rotary converter panel for, 919. 
synchr. motor panels for, 919. 
two-phase panels for, 915 
Westinghouse generator panel 
for, 925. 
rotary panel for, 925. 
three-wire generator panel for, 
926. 
Switches disconnecting type, 965. 
for equalizer circuits, remote con- 
trol, 962. 
for high potential, 957. 
lever type, 963. 
oil, operation of, 967. 
plug tube type, 965. 
quick break, 964. 
sparking at, 948. 
Switching devices, arrangement of, 
935. 
specifications for, 948. 
Switch jaws, current density for, 

442. 
Symbols, dynamo and motor section, 
334. 
electrical engineering, 1. 
for wiring plans, 299. 
mechanical, 1. 
table of, 6. 
Synchronizers, descr. of, 416. 
Synchronizing of alternators, 421. 
Synchronous converter, def. of, 503. 
impedance, 400. 

field current, 383. 
machines, def. of, 504. 

losses in, meas. of, 511. 
motor panels, equip, of, 919. 
motors, starting of, 431. 
tests of, 399. 
theory of, 432. 
used as condensers, 292. 
phase modifier, def. of, 502. 
Synchroscope, definition of, 504. 

inductor type, 417. 
Synopsis of report, water power 

property, 1460. 
Syntonic apparatus, 1062. 

signalling, 1059. 
System, C. G. S., 2. 



Table of angular dist. betw. 
brushes 344. 
of armature slot sizes, 372. 
of capacity per 1000 feet of aerial 

wires, 252. 
of change of hysteresis by heating, 

457. 
of charging current per 1000 feet 

of aerial circuits, 253-258. 
of closed circuit cells, 14. 
of copper wire phys. const., 143. 
of cost of duct material in place, 
307. 
of paving per sq. yd., 305. 
of street excavation per cond 
ft., 306. 
of double square roots, 45-46. 
of eddy current factors, 106. 
of electrical and mechanical units, 

1258. 
of energy and work units, 12. 

of dissipation in arm. core, 107. 
of hysteretic constants, 99. 
of inductive reactances, 242. 
of magnetization of electromag- 
nets, 111. 
of physical quantities, 6. 
of properties of galv. iron wire, 

34. 
of open circuit cells, 15. 
of resistance of aluminum wire, 
196. 
of Driver-Harris wire, 207. 
of magnet wire, 112. 
of self-induction in millihenrys, 

241. 
of specific ind. cap. of gases, 35. 
of specific res. of cond., 132. 
of wire gauges, 141. 
Tables correcting length of magnet 
coil, 117-120. 
of linear space occupied by D. C. 

cov. wire, 123-126. 
S. C. cov. wire, 121-123. 
Tabulation of core loss tests, 384. 
Tan a, values of, 276. 
Tangent galvanometer, des. of, 22. 

track, hangers per mile for, 646. 
Tantalum lamps, 549. 

candle-power of, 553. 



INDEX. 



1589 



Tapering of conductors, economical, 
279. 
of railway conductors, 793. 
Teaser, use of, 477. 
Teeth of armature cores, design of, 

357. 
Telautograph, U. S. Army, 1141c 
Telegraph cables, 189. 
codes, 1052. 
field, 1140. 
fortress, 1140. 
U. S. Navy engine, 1202. 
wire, galv. iron, properties of, 199. 
hard-drawn, prop, of, 156. 
steel, properties of, 201. 
Telegraphy, American methods of, 
1040. 
closed circuit method of, 1040. 
duplex, 1044. 

European method 9f, 1040. 
open circuit method of, 1040, 
wireless, U. S. Army, 1145. 
Telephone cables, 188. 
capacity of, 1085. 
expenses of, 1087. 
sizes of, 1086. 
specifications for, 1083. 
lines, hotel, 1088. 
house, 1088. 
private, 1088. 
transposition of, 285. 
method, meas. mutual ind. by, 
68. 
meas. self-induction by, 66. 
plant, cost of, 1108. 

depreciation of, 1108. 
receiver, Bell, 1070. 

watch, 1070. 
switchboards, common battery, 
1098. 
design of, 1089. 
portable, 1141. 
series multiple, 1092. 
system, branch terminal, 1093. 
bridging, 1093. 
central battery, 1096. 
central energy, 1096. 
common battery, 1096. 
Pupin, 1107. 
radial, 1117. 



Telephone system, three-wire, 

transfer, 1094. 

two- wire, 1101, 1120. 
systems, automatic exchange, 
1105. 

bridging of, 1110. 
common signalling battery, 
1115. 

four-wire selective, 1103. 

intercommunicating, 1114. 

Newburgh, 1103. 

selective, 1102. 

series party, 1109. 

step-by-step, 1102. 

transmission, 1070. 

two-party selective, 1102. 
Telephonic transmission, limits of, 

1107. 
Telephones, field, 1140. 
fortress, 1140. 
navy, spec, for, 1206. 
Telephony, duplex, 1106. 

multiplex, 1106. 
Telescope for galvanometer, 24, 
Temperature coef. of copper, 527. 

of metals, 133. 
correction, 519. 
of electric arc, 581. 
of fire, 1349. 

of apparatus during test, 508. 
of transformer windings, 447. 
or intensity of heat, 1506. 
rise in armatures, 349, 358. 

in boosters, 814. 

in cables, 210. 

in commutator, 362. 

in field coils, 352. 

in generators, U.S. Navy, 1158. 

in magnet coils, 127. 

in railway motors, 675. 

in switchboard devices, 910. 

in transformers, 491, 498. 

in, meas. of, 518. 
test by rise of resistance, 379. 
tests of dynamos, 378. 

records of, 381. 
variation of resistance with, 228. 
Tensile strength of copper wire, 

table of, 156. 

of woods, 1316, 



1590 



INDEX. 



Tension and sag in wire spans, 218. 
Terminal anchorage, 637. 
Terminals for bonds, 774. 
Test car, diagram of, 799. 

lamps, Navy standard, 1172. 
plate, descr. of, 537. 
voltage, meas. of, 517. 
Testing-board, Herrick's, 805. 

batteries, chloride of silver type, 

16. 
capacity of cables, 325. 
drop and resistance in trolley 

lines, 798. 
dynamo efficiency, Kapp's method, 

387. 
electric plants, 1283. 
instruments, description of, 13. 
integrating wattmeters, 1028. 
joints of cables, 323. 
large transformer, G. E. method, 

490. 
rail bonds, 801. 
service meters, 1015. 
set, S.K.C. high voltage, 461. 
storage batteries, 882. 
submarine cables, 331. 
transformers, 459, 482. 

Ayrton & Sumpner's method 

of, 496. 
data for, 495. 
Tests of American woods, 1317. 
of cables, dielectric, 332. 
of cast iron columns, 1306. 
of dynamos and motors, 378. 
of interurban cars, 722. 
of R. C. wire, Underwriters', 161. 
of street railway circuits, 798. 
of synchronous motors, 399. 
of various types of steam engines, 

1439. 
of, with voltmeter, 74. 
Thallium, phys. and elec. prop, of, 

140. 
Thawing water pipes by electricity, 
1271. 
power required for etc., 1531. 
Theater run of high speed railway, 

721. 
Theory of polyphase induction 
motor, 423. 



Theory of storage batteries, 872. 

of synchronous motor, 432. 
Thermal conductivity of dielectrics, 
specific, 234. 
unit, British, 3. 
Thermit rail welding, 778. 
Thermometers, comparison of, 1506. 
Third rail bonding, 778. 
cost per mile of, 835. 
insulators, 831. 
location of, 830. 
qualities of steel for, 822. 
shoes, 832. 
system, 821. 
Thompson permeameter, use of, 

93-96. 
Thomson elec. welding process, 1271. 
induction wattmeters, 1005. 
polyphase induction wattmeters, 

1005. 
recording wattmeters, 998. 
-Ryan dynamo, special winding 
of, 351. 
Thomson's method, res. of gal v. by, 
60. 
testing cap. of cables by, 325. 
Three conductor cables, G. E. Co., 
table of, 170. 
loss of power in sheath of, 

293. 
watts per foot lost in, 212. 
paper ins. cables, table of, 178. 
Three-phase alternators, E.M.F. of, 
404. 
armature winding, 413. 
cables, power carrying cap. of, 216. 
circuits, arrangement of, 291. 
charging current per 1000 feet 

of, 253. 
energy in, 405. 
self induction in, 239. 
delta connection armatures, loss 

in, 408. 
distribution railway system, 815. 
feeder panel, equip, of, 917. 
generator panels, 912. 
induction motors, current taken 
by, 297. 
potential regulators, 469. 
lines, balancing of, 287. 



INDEX. 



1591 



Three-phase lines, capacity effect in, 

249. 
motors, reading watts in, 398. 
power, meas. of, 72. 

transmission, transformers for, 

478. 
rotary converter, 437. 

panels, equip, of, 919, 924. 
rotary transformers, armatures of, 

441. 
star connection armatures, loss in, 

408. 
station bus-bars, 933. 
synchronous motor panels, equip. 

of, 919. 
system, balanced, 73. 

protection by relays, 959. 
systems, ratio of transformers in, 

471. 
to six-phase connections, 475. 
transformer connections, 473. 
transformers, 470. 
transmission line, ind. react, of, 

245. 
wiring examples, 273. 
Three voltmeter method, A.C. power 

by, 71. 
Three- wire battery system, 899. 
booster system, diagram of, 902. 
direct current system examples, 

271. 
Edison system, 355. 
generator panel, equipment of, 926. 
telephone system, 1099. 
street railway system, 807. 
two-phase system, formula for, 

270. 
variable speed motor system, 354. 
Throttling calorimeter, 1394. 
Ties, bearing surface per, 618. 
durability of, 619. 
per mile per track, 618. 
Time-constant, formula for, 239. 
element mechanism, 958. 
limit relays, 956. 

relay, Westinghouse, 960. 
required for elec. welding, 1272. 
Tin, fusing effect of current on, 217. 
phys. and elec. prop, of, 140. 
spec. res. of, 132. 



Tin, temperature coef. of, 133. 
Tire welding, electric, 1272. 
Tires, data on, 1225. 
Tirrell regulator for alternators, 409. 
Toluene, spec. ind. cap. of, 37. 
Tools and supplies for installing 

electric work, 1530. 
Toothed armatures, advantages of, 

341. 
Torpedo circuit closer, 1139. 

firing, electric, 1213. 
Torque of induction motors, calc. of, 
399. 
of motor armatures, 353. 
of polyphase induction motor, 423. 
of railway motors, 731. 
Torsion dynamometer, 42. 
Tower, cooling, 1447. 
Track and trolley, resistance of, 798. 
bonding, condition of, 800. 
bonds, efficiency of, 781. 
requirements for, 775. 
data, 618. 

gang, tools for, 620. 
laying force, 619. 
rail, resistance of, 779. 
return circuit, 771, 786. 
Traction data, 1224. 
horse-power of, 653. 
law of, 110. 
method, determ. magn. values by, 

93. 
of electromagnets, 110. 

table of, 111. 
table of, 655. 
Tractive coefficient, 662. 
effort, 661. 

curves of railway motors, 686. 
of solenoids, 130. 
on grades, 657. 
test for, 1226. 
force, table of, 654. 
Train diagram, 787. 
friction, 613. 
curve, 679. 
log for interurban tests, 722. 
performance diagram, 663, 667. 
resistance curve for one car train, 

683. 
voltage drop at, 795. 



1592 



INDEX. 



Training gear for guns, 1191. 
Transfer telephone system, 1094. 

adv. of, 1094. 
Transformer cells for hydro-electric 

plant, 931. 
connections, 472. 

cores, magnetic densities for, 447. 
tests, data for, 495. 
def. of, 503. 
design, 447. 
equations, 446. 
house, single-phase A.C., views of, 

943. 
loss, meas. of, 511. 
oil, specifications for, 500. 
panels, constant current, equip. 

of, 922. 
Static, def. of, 443. 
testing, 482. 
Transformers, ageing of, 498. 
air-blast type, 449. 
capacity of, table of, 498. 
change of hysteresis by heating in, 

457. 
characteristics of, 483. 
comparative core losses in, 455. 
comparative expense of operating 

large and small, 458. 
connected to rotary converters, 

442, 476. 
connections for wiring, 297. 
copper loss in, table of, 498. 
core loss in, 445. 

table of, 498. 
cores of American types of, 443. 
current, descr. of, 945. 
det. of size of, 295. 
duties of perfect, 445. 
efficiency of, 453. 

test of, 493. 
exciting current in, table of, 498. 
for constant current, 464. 
for constant secondary current, 

462. 
for long distance transmission, 

arrangement of, 474. 
for stepping-down high potential, 

478. 
for transmission plants, 870. 
heat test of, 489, 497, 



Transformers, hysteresis loss of, 445. 
improvement in, 454. 
insulation of, 447. 
insulation test of, 483, 516. 
in three-phase system, ratio of, 

471. 
iron loss for, table of, 482. 
leakage drop in, meas. of, 497. 
location of, 499. 
natural draft type, 448. 
oil-cooled, 448. 
polarity of, 495. 
potential, descr. of, 945. 
power factor of, 458. 
protection by static interrupter of, 

993. 
regulation of, 458, 491. 

table of, 498. 
resistance of, meas. of, 486. 
rise of temperature in, 498. 
series type, 464. 
specifications for, 498. 
table of capacities of, 296. 
temperature of windings of, 447. 
temperature rise in, 520. 
testing, 459. 
testing iron and copper losses of, 

496. 
three-phase type, 470. 
water-cooled type, 449. 
wiring for, 295. 

Y or delta connection of, 478. 
Translating devices, distribution to, 

262. 
Transmission circuits, capacity of, 
249. 

properties of, 238. 
conductors for high tension, 235. 
line formulae, 275. 

inductive react, of three-phase, 
245. 

of known constants, 274. 
lines, aluminum for high tension, 
199. 

calculation of, 264. 

circuit breakers protecting, 951. 

design of, 866. 

efficiency of, 512. 

high potential strains on, 981. 

regulation of, 513. 



INDEX. 



1593 



Transmission of power, classif. of, 
864. 
of speech, 1070. 

plants, switchboards for, 870. 
system, conductors for, 260. 
telephonic, limits of, 1107. 
Transmitters, battery, 1071. 
Blake, 1072. 
granular button, 1074. 
high-power, 1063. 
magneto, 1071. 
multi-contact, 1072. 
single-contact, 1071. 
solid back, 1072. 
ungrounded, 1063. 
wireless telegraph, 1062. 
Transmitting appliances, table of, 

864. 
Transposition of lines, 285. 

telephone lines, 1082. 
Transverse strength of beams, 1308, 

of woods, 1317. 
Traversing motor for gun operation, 

1134. 
Trenton beams and channels, 1313. 
iron beams and channels, 1314. 
rolled steel beams, 1313. 
Trial armature coil slots, 372. 
values for number of armature 
coils, 373. 
Trigg works, motors, horse-power of, 

1518. 
Trimming arc lamps, 583. 
Trip contact for relays, 958. 
Triple cond. varnished cambric 

cables, 185. 
Triplex armature windings, 348. 
Trip oil switches, use of, 916. 
Tripping mechanism, 958. 
Trolley and track, resistance of, 798. 
cars, energy consumption of, 652. 
power required for, 656. 
wiring of, 806. 
construction, cost of one mile of, 
629. 
for A. C. railways, 640. 
feeders, arrangement of, 789. 
line, drop at end of, 800. 

material per mile of, 643. 
system, laying out, 785. 



Trolley and track, wheels, R.P.M. of, 
655. 
wire, dip in, 635. 
size of, 786. 
suspension, 637. 
Troubles of storage batteries, 881. 
Troy measure, 1500. 
Truck lights, U. S. Navy, 1181. 
Trucks of cars, weight of, 734. 
Trunking, methods of, 1095. 
Trunk signals, auxiliary, 1096. 
Truss plank heaters, wiring diag. of, 

1267. 
Tube lighting system, 565. 
Tubes, collapsing pressure of, 1429, 
dimensions of boiler, 1428. 
heating surface of, 1328. 
regenerative X-ray, 1251. 
X-ray, 1249. 
Tubular lamps, navy spec, for, 1173 

poles, iron and steel, 633. 
Tungsten lamps, data on, 553. 
steel, phys. and elec. prop, of, 
140. 
Turbines, dimensions of hydraulic, 
1477. 
dimensions of Victor, 1477. 
impulse wheels, diagram of, 1479. 
installing hydraulic, 1477. 
inward flow of, 1476. 
McCormack, diagram of, 1478. 
outward flow of, 1476. 
parallel flow, 1476. 
steam, 1451. 

U. S. Navy spec, for steam, 1160. 
water, 1476. 
Turbo generating sets, spec, for, 1 159. 

generators, operation of, 1162. 
Turnout suspension, 638. 
Turnouts, railway, 620. 
Turns of wire for transformers, 
equation for, 446. 
of wire in coil, calc. of, 113. 
per armature coil, trial calc. for, 
374. 
Turpentine oil, spec. ind. cap. of, 

37, 227. 
Turret turning gear, navy spec, for, 
1187. 
system, 1165. 



1594 



INDEX. 



Twin conductor wire table, U. S. 

Navy, 1170. 
Twisted pairs, use of, 1082. 

wire, res. betw. terminals of, 86. 
Two-circuit single winding of arma- 
ture, 342. 
-conductor cables, watts per foot 

lost in, 212. 
motors vs. four motors per car, 729. 
overhead wires, capacity of, 250. 
-party selective telephone sys- 
tems, 1102. 
-path triplex armature wind., 348. 
-phase armatures, loss in, 408. 
armature windings, 412. 
circuits, arrangement of, 291. 
feeder panel, equip, of, 918. 
generator panel, 915. 
rotary converter, 436. 
rotary converter panels, 921. 
rotary transformers, armatures 

of, 441. 
systems, formula for, 270. 
transformer connections, 472. 
transmission circuit, calc. of ,280. 
wiring examples, 272. 
Two-wire direct current system, 
examples, 271. 
telephone system, 1101, 1120. 
Types of plates for batteries, 874. 
of underground cables, 320. 

Undamped oscillations, 1068. 
Underground and submarine cables, 
tests of, 321. 
cables, drawing in, 319. 
locating faults in, 331. 
types of, 320. 
conduits and construction, 301. 

in Chicago, cost of, 317. 
mains, current variations on, 857. 
metal, deterioration of, 852. 
telephone cables, 188. 

capacity of, 1086. 
work at New Orleans, 308. 
Underhill on Electromagnets, 127- 

130. 
Underload circuit breakers, 950. 
use of, 899. 
D.C. relay, 962. 



Underwriters* rules for protection of 
buildings, 1280. 
test of R. C. wire, 161. 
Ungrounded transmitters, 1063. 
Uniform railway conductors. 792. 
Unipolar machines, def. of, 504. 

losses in, meas. of, 512. 
Uni Signal Company system, 624. 
Unit difference of potential, 4. 
electromagnetic, definition of, 5. 
electro-motive force, 4. 
lightning arrester, 990. 
of capacity, 4. 
of current, 4. 
of force, 3. 
of horse-power, 3. 
of quantity, 4. 
of resistance, 4. 
of resistance, definition of, 5. 
of strength of pole, 4. 
of work, 3. 

switch control, A.C. railway 
system, 710. 
system, 766. 
weights, 1513. 
United States Army, use of elec. in, 
1123. 
Navy electric fuse, 1137. 
electricity in, 1153. 
engine specifications for, 

1154. 
generator spec, for, 1156. 
Units, absolute, 2. 
C. G. S., 2. 
derived geometric, 2. 
derived mechanical, 2. 
electrical, 4. 

and mechanical, table of, 1258. 
engineering, 2. 
electrostatic, 4. 
fundamental, 2. 
geometric, 2. 

international electrical, 9. 
magnetic, definition of, 4. 
of heat, 3. 
of light, 530, 534. 
of resistance, 131. 
symbols and abbreviations for, 6. 
Universal shunt, Ayrton and Mather, 
30. 



INDEX. 



1595 



Unstable neutral, 479. 
Upper harmonics, theory of, 1218. 
Uses of incandescent lamps, 544, 
555. 
of light, 600. 
of storage batteries, 886. 
U. S. Navy rule for ins. res., 85. 

standard lamps, table of, 1176. 
U. S. standard gauge for sheet and 
plate steel and iron, 1299. 
sheet metal gauge, thickn in 
millimeters, 1299. 
Utensils, electric cooking, cost of 
' operating, 1259. 

Vacuum, spec. ind. cap. of, 35. 
tube light, 565. 

tubes, exciting source for, 1252. 
Value of A.C. voltage and current in 

terms of D.C., 438. 
Values for numbers of armature 
coils, 373. 
for turns per armature coil, 374. 
Valve, foot, 1447. 
Vapor lamps, Cooper-Hewitt type, 

558. 
Vapors, specific gravity of, 1512. 
Variable speed motor work, 354. 
Variation, def. of, 506. 
of efficiency of lamps, 547. 
of resistance with temperature, 

228. 
of voltage in storage battery, 876. 
Varley loop test, locating faults in 

cables by, 329. 
Varnished cambric ins. cables, tables 
of, 178a-187a. 
triple cond., 185. 
Vaseline, spec. ind. cap. of, 37. 
Vegetable oils, 1497. 
Velocity, angular, 1505. 
definition of, 3. 
definition of, 2. 
Ventilation fans, navy spec, for, 
1196. 
of armatures, 350. 
of transformers, 449. 
Vertical shear of beams, 1308. 

tubular boilers, 1327. 
Very high res., meas. of, 79. 



Victor turbines, dimensions of, 1477. 
Virtual resistance of storage cell, 

883. 
Voltage and current of A.C. in terms 
of D.C., 438. 
curve of railway motors, 669. 
curves of storage batteries, 883. 
drop at brush faces, 362. 

in parallel distribution system, 

279. 
in storage cells, table of, 879. 
for power transmission, 870. 
limitation of, 866. 
loss in storage batteries, 882. 
meas. of, 62. 

regulation of transformers, 452. 
transformers, high-tension station, 

938. 
variation in storage battery, 876. 
variations, minimizing, 1002. 
Voltages, discussion of standard, 
521. 
for plating, 1234. 
Voltaic battery, def. of, 14. 
Voltameter, silver, description of, 10. 
Volt, definition of, 5. 
generation of, 336. 
international, def. of, 9. 

specification for determ., 10. 
value of, 7, 8. 
Voltmeter, balance used as, 43. 
Bristol recording single-phase, 

1038. 
electrostatic, Kelvin, 40. 
method, meas. of current by, 77. 
Weston type, 41. 
Voltmeters, description of, 40. 
electrostatic, use of, 945. 
high res. for, 75. 
meas. high res. with, 79. 

ins. res. of circuits with, 80, 
ins. res. of wiring system with, 

82. 
res. with, 78. 
permanent magnet type, 74. 
tests with, 74. 
Voltex process for welding aad 

brazing, 1274. 
Volume of steam, tables of, 1404. 
Voynow joint, 778. 



1596 



INDEX. 



Vulcanized rubber, electrical prop- 
erties of, 229. 

Wagner motor, design of, 430. 
single-phase motor, connections 

of, 431. 
Walmsley's rail tester, 802. 
Ward-Leonard system of motor 

control, 354. 
turret turning gear, 1188. 
Waring cables, joints in, 191. 
Warren's method, locating faults in 

ins. wires by, 330. 
Watch receiver, 1070. 
Water analyses, table of, 1366. 
and mercury columns, pressure of, 

1463. 
-cooled transformers, 449. 
cubic feet discharged per min., 

1470. 
expansion of, 1362. 
flow, estimate of, 869. 

in a stream, 1471, 

over Weirs, 1473. 

through an orifice, 1471. 

through various pipes, 1469* 
for boiler feed, 1362. 
friction in pipes of, 1374. 
gas, 1357. 
heating by electricity, cost of, 

1259. 
horse-power, tables of, 1475. 
lifted by suction, 1367. 
loss of head due to bends in pipes, 

1374. 
mains, effect of current on, 852. 
meters, electrolytic effect on, 858. 
motors, regulation of, 514 
pipes, thawing out, 1271. 
power, 1460. 

data on, 867. 

synopsis of report on, 1460. 

yearly expense per H .P. of, 1464. 
pressure of, 1465. 
pumping hot, 1367. 
purification of boiler feed by 

boiling, 1365. 
rheostats, 33. 
rod float gauging, 1471. 
specific heat of, 1511. 



Water, specific inductive capacity of, 
227. 

res. of, 133. 
speed through pump-passages and 

valves of, 1368. 
theoretical velocity and discharge 

of, 1470. 
tight door alarm, U. S. Navy, 
1211. 

doors, control of, 1198. 
weight per cubic foot of, 1360. 
wheels, 1476. 

racing of, 981. 
Watt, definition of, 3. 
-second, value of, 12. 
value of, 5, 8. 
Wattless current, def. of, 296. 
Wattmeter, balance used as, 44. 
hysteresis tested by, 102. 
power meas. by, 72. 
Wattmeters, action of, 1039. 
bearings of, 1009. 
Bristol recording single-phase, 

1037, 
calibration of, 1014. 

Westinghouse integrating, 1016. 
checking, 72. 
constants of, 1029. 
D. C. Sangamo, 1007. 
Fort Wayne induction, 1005. 

testing of, 1033. 
G. E. recording, 1036. 

testing of, 1030. 
integrating, testing of, 1013. 
on inductive circuit, 1000. 
polyphase and D.C., testing of, 
1020. 

installation of, 1023. 

integrating, 1004. 
prepayment, 1010. 
Sangamo integrating, 1006. 

testing of, 1035. 
speed error table for, 1032. 
speeds of, 1029. 
Thomson high torque, 1005. 

polyphase induction, 1005. 

recording, 998. 
use of, 72. 

Westinghouse induction, 999, 
1003, 



INDEX. 



1597 



Wattmeter, Westinghouse recording, 
1037. 
Weston type, 42. 
Wright discount, 1008. 
Watts lost in armature cores, 360. 
in armature windings, 359. 
in cables, 210. 
in core of transformer, 456. 
transformer cores, 454. 
per candle of arc lamps, 540. 
Wave-connected armature wind- 
ings, 347. 
form, determination of, 50. 

E.M.F., 1218. 
shape, standard, 507, 508. 
Waves, electromagnetic, 1055. 

propagation of, 1058. 
Wax, specific inductive capacity of, 

227. 
Weather-proof aluminum wire 
stranded, 197. 
wire, carrying capacity of, 209. 
table of, 160, 160a-160b-160c. 
Weaver speed recorder, 1212. 
Webb, H. S. on water rheostats, 33. 
Weber photometer, 537. 
Wehnelt interrupters, 1254. 
Weight and bulk of bricks, 1322. 
of A.C. motor equipments, 719. 
of aluminum, 1514. 
of brass, sheet and bar, 1323. 
of car bodies and trucks, 734. 
of chains, 1496. 
of conductors, calc. of, 277. 
formula for, 265. 
table of, 270. 
of copper, 143. 

and brass wire and plates, 1324. 
per K.W. del'd, curves show- 
ing, 283. 
round bolt, 1323. 
wire, English system, table of, 

157. 
metric system, table of, 158. 
of flat iron, 1295. 
of iron and steel, 1294. 

per sq. ft. in kilograms, 1299. 
per sq. ft. in lbs., 1299. 
per sq. ft. in ounces, 1299. 
per sq. meter in kilograms, 1299. 



Weight of iron and steel per sq. 
meter in lbs., 1299. 

of oil per gallon, 1497. 

of plate iron, 1298. 

of rails, 615." 

of railway equipments, 739. 

of square and round iron, 1297c 

of steam, tables of, 1404. 

of storage cells, 882. 

of various woods, 1316. 

cf water per cubic foot, 1300. 
above 212° F., 1361. 

of wood, 634. 

per mile-ohm, def. of, 131. 
Weights and measures, 1499. 

apothecaries, 1500. 

avoirdupois, 1500. 

metrical equivalents, 1501. 

troy, 1500. 
Weiny-Phillips repeater, 1043. 
Weir dam measurement, 1473. 

table, 1474. 
Weirs, Francis' formulae for, 1474 
Welding, electric, 1271. 

H.P. used in electric, 1271. 

iron pipe, 1272. 

tires, 1272. 
Western Electric telephone system 

U. S. Navy, 1207. 
Westinghouse A.C. motor character- 
istics, 715. 

A.C. railway system, 707. 

circuit breaker, 951. 

economy coil, 463. 

electromagnetic railway, 841. 

generator panel, 925. 

induction type wattmeters, 999, 
1003. 

integrating meters, 998. 

locomotives, 744. 

method of balancing magnetic 
circ. in dynamo, 349. 

mercury arc rectifiers, 481. 

oil circuit breakers, 969. 

railway motors, 729. 

characteristic curves of, 696. 
rating of, 673. 

recording meters, 1037. 

relay, D. C. over- voltage, 962. 

rotary panel, 925. 



1598 



INDEX. 



Westinghouse single-phase potential 
regulators, 467. 
switchboard panel, 907. 
three-wire generator panel, equip- 
ment of, 926. 
unit switch control system, 766. 
wattmeters, calibration data for, 
1016. 
test formula for, 1028. 
Weston cadmium cell, 19. 

model, Wheatstone bridge, 56. 
voltmeter, 41. 
wattmeter, 42. 
Wheatstone bridge, 32. 
Y-box multiplier, 73. 
Wheatstone bridge, 31. 
Kelvin type, 59. 
method, res. meas. by, 56. 
method, E.M.F. of batteries, 62. 
Wheels, R.P.M. of trolley, 655. 
Whistle, electric, navy spec, for, 

1210. 
White core ins. three cond. cable, 

table of, 170. 
Winches, deck, 1196. 
Windage test for dynamos and 

motors, 383. 
Winding of electromagnets, 112. 
field-magnets, 369. 
plunger solenoids, 128. 
ring armature, 342. 
Windings of A.C. armatures, 410. 
Wind velocity on wire spans, effect 

of, 219. 
Wire, aluminum, deflection in feet of, 
226. 
properties of, 194. 
resistance of stranded, table of, 
198. 
copper, properties of, 143. 
cotton covered, 163a. 
galv. iron, water rheostats, 34. 
gauge, U. S., and weights of iron, 

1299. 
gauges, table of, 141. 
iron and steel, prop, of, 199. 
magnet, table of, res. of, 112. 
Navy standard, 174. 
paper insulated, 174. 
resistance, 202, 



Wire rope, galvanized iron, 1325. 

notes on uses of, 1494. 

standard hoisting, 1326. 

transmission of power by. 
1495. 
transmission or haulage by, 1325. 
ropes, horse-power of, 1495. 
rubber covered, 161. 
sizes for armature coils, 372. 
solid copper, table of, 154. 
spans, tension and sag in, 218. 
steel, properties of, 201. 
stranded copper, table of, 155 
strands, table of, 142. 
table, U. S. Navy, 1169. 
tables, copper, A.I.E.E., 146. 
condensed table, 154. 

explan. of, 145. 
varnished cambric ins., 179. 
weather proof, 160, 160a, 1606. 
weight of copper, table of, 157. 
Wireless telegraphy receivers, 1064. 

theory of, 1055. 

transmitters, 1062. 

U. S. Army, 1145. 
Wires and cables, properties of, 

131. 
cambric ins., tables of, 179. 
current carrying capacity of, 208. 
enameled, table of, 187b. 
fusing effect of current on, 217. 
gutta-percha covered, jointing of, 

193. 
navy standard, table of, 174. 
paper ins. G. E. tables of, 174-178. 
rubber ins. G. E. tables of, 164- 

172. 
space occupied by cotton covered, 

tables of, 121-126. 
suspended from points not in same 

level, sag in, 223. 
U. S. Navy spec, for, 1167. 
Wiring bells, 293. 

diagrams of cars, 806. 
for transformers, 295. 
of cars, 746 

for heaters, diagram of, 1267. 
of houses, 279. 

plans, standard symbols for, 299. 
specifications, U. S. Navy, 1167. 



INDEX. 



1599 



Wiring system, ins. res. of, 82. 
Wood as fuel, 1356. 

beams, strength of, 1318. 

mill, power required to run tools 

for, 1519. 
specific inductive capacity of, 227. 
tests of American, 1317. 
weight per cord of, 1356. 
Wood working machinery, power to 
run, 1519. 
tools, power required for, 1522. 
Wooden poles, contents of, 633. 
painting of, 806. 
stave pipe, 1468. 
Woods, American, wt. and value as 
fuel of, 1349. 
crushing strengths of, 1316. 
pressure to indent sV, 1316. 
properties of various, 1316. 
relative strength for cross break- 
ing, 1316. 
shearing strength with the grain of, 

1316. 
specific gravity, table of, 1512. 
tensile strength of, 1316. 
value in tons of coal, 1349. 
weight of, 634. 

per cubic foot of, 1316. 
per ft. B. M., 1316. 
Woolf process, disinfecting by, 1244. 
Work done by conductors in magn. 
field, 109. 
international unit of, 10. 
unit of, 3. 



Work units compared with energy 

units, 12. 
Workshop method, res. of batteries, 

61. 
Wright demand meter, 1008, 

discount meter, 1008. 
Wrought iron, permeability of, 89. 

phys. and elec. prop, of, 137. 

pipe, dimensions of, 1426. 

poles, weight of, 633. 

qualities of, 824. 
Wurts lightning arresters, 984. 

X-rays, polarization of, 1248. 

theory of, 1248. 

tubes for, 1249. 
Xylene, spec. ind. cap. of, 37. 

Y-box multiplier, Weston, 73. 

-connection of transformers, 478. 
Yokes, field magnet, general data on, 
352. 

Zerener system of welding, 1274. 
Zero instrument, Northrup, 26. 
Zinc amalgam for standard cell, 11. 

for boiler scale, 1365. 

phys. and elec. prop, of, 136, 
140. 

spec. res. of, 132. 

sulphate for standard cell, 11. 
spec. res. of, 133. 

temperature coef. of, 133. 
Zone, commutating, 350. 





One of the Complete Group 

of Weston Round Pattern A. C, 

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Group is for D. O. Service, 

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From a purely scientific standpoint this Company 
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Indicating Electrical 
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They are thoroughly worthy to represent Weston 
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these are the instruments most frequently encoun- 
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desirable for educational purposes. 

There are Weston Instruments in 
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23 Branch Offices in the Larger Cities 



ELECTRICAL WIRES 
AND CABLES 



TELEPHONE WIRE 
TROLLEY WIRE 
POWER CABLES 
WEATHERPROOF 

WIRE 
MAGNET WIRE 
ANNUNCIATOR 
WIRE 
LAMP CORD 
AUTOMOBILE 
CABLES 




WIRE 

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STRAND 



MADE BY 



John A. Roebling's Sons Co. 

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DOSSERT CONNECTORS 




2- Way Type A Showing: Details. 

Dossert Connectors eliminate entirely the use of solder in making electrical con- 
nections and splices, and are approved for use without solder by the National Board of 
Fire Underwriters for all classes of wiring. 

By their use much labor is saved and splices obtained that will withstand any over- 
load. Many careful tests show that a splice made by means of a Dossert Connector 
will not heat as much as the cable which it connects when the cable is heavily over- 
loaded. 

Type A Connectors are for use on cables, stranded, or solid wires, rods and tubing* 
They are simple and effective, and by their use splices can be quickly made in conduct" 
ors of any size. Type A Connectors, however should not be used on a cable that is to 
be subjected to heavy tensile strains. 






Part Cross-sectional View of Type B 2-Way 




Type B Connectors are for use on stranded 
wires or cables only, and are designed to make 
a joint which will withstand heavy tensile 
strains. They are not made for wires smaller 
than No. 0. 

The Cable Tap is used to connect a branch 
wire, rod or bleeder, to a main wire, rod or 
feeder. It does not splice the main, but 
simply clamps on to it. Branch wire is con- 
nected to cable tap by means of a nut and 
sleeve as shown in Type A cut. 

With Dossert devices any combination of 
different sizes of cables, stranded and solid 
wires, rods and tubing can be connected to- 
gether. The cable tap will tap from any size 
main to any size branch. Terminal and 
switchboard lugs, front or back connected; 
angle and swivel lugs. Insulated connectors; 
two-ways, three-ways, equalizers, cable an- 
chors, reducers, elbows, Y's, service box lugs 
Cable Tap and plugs, grounding devices and stud con- 

nectors for threaded rods or flat strips or blocks. 

Send for Tenth Year Catalogue. 

Dossert & Company 

H. B. LOGAN, President 

242 West 41st Street New York, N. Y. 




SEND FOR IT TO-DAY 



Catalog of Books on 

ELECTRICITY 



Classified by subjects as follows: 



Alternating Currents. 

Armatures. 

Automobiles. 

Batteries. 

Bells. 

Biography and History. 

Cables and Wires. 

Dictionaries, Directories. 

Direct Currents 

Dynamo Electric Machines — 

A. C. and D. C. 

Care, Repair, Testing. 
Electricity and Magnetism. 

Advanced Texts. 

Books for Amateurs 

Elementary Texts. 

In Mines. 

Various Applications. 
Electrochemistry. 
Electrometallurgy. 
Electroplating. 
Induction Coils. 



Lighting. 

Lightning Protection. 

Measurements and Meters- 
Calculations. 

Miscellaneous. 

Patents. 

Pocket Books. 

Power Plants and Trans= 
mission. 

Radium. 

Railways. 

Static Electricity. 

Switchboards and Circuits. 

Telegraphy- 
Cables, Codes. 
Wireless. 

Telephony- 
Wireless. 

Transformers. 

Wireless Telegraphy. 

Wiring for Light and Power. 

X Rays and Radiography. 



96 Pages. 900 Books. 32 Subjects 

No matter what branch of Electrical Engi- 
neering you want information about, you'll 
find a book that gives it in this catalog. 
We send it free and are always glad to an- 
swer any questions about Scientific Books. 



D. Van Nostrand Company 

Publishers and Sellers of Scientific Books 
25 PARK PLACE, NEW YORK 



